Polymers

2023

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21 pages, 20381 KiB

Open AccessArticle

Fracture of Epoxy Matrixes Modified with Thermo-Plastic Polymers and Winding Glass Fibers Reinforced Plastics on Their Base under Low-Velocity Impact Condition

by Ilya V. Tretyakov, Tuyara V. Petrova, Aleksey V. Kireynov, Roman A. Korokhin, Elena O. Platonova, Olga V. Alexeeva, Yulia A. Gorbatkina, Vitaliy I. Solodilov, Gleb Yu. Yurkov and Alexander Al. Berlin

Polymers 2023, 15(13), 2958; https://doi.org/10.3390/polym15132958 - 5 Jul 2023

Cited by 3 | Viewed by 1283

Abstract

The work is aimed at studying the impact resistance of epoxy oligomer matrices (EO) modified with polysulfone (PSU) or polyethersulfone (PES) and glass fibers reinforced plastics (GFRP) based on them under low-velocity impact conditions. The concentration dependences of strength and fracture energy of [...] Read more.

The work is aimed at studying the impact resistance of epoxy oligomer matrices (EO) modified with polysulfone (PSU) or polyethersulfone (PES) and glass fibers reinforced plastics (GFRP) based on them under low-velocity impact conditions. The concentration dependences of strength and fracture energy of modified matrices and GFRP were determined. It has been determined that the type of concentration curves of the fracture energy of GFRP depends on the concentration and type of the modifying polymer. It is shown that strength σ and fracture energy E_M of thermoplastic-modified epoxy matrices change little in the concentration range from 0 to 15 wt.%. However, even with the introduction of 20 wt.% PSU into EO, the strength increases from 164 MPa to 200 MPa, and the fracture energy from 32 kJ/m² to 39 kJ/m². The effect of increasing the strength and fracture energy of modified matrices is retained in GFRP. The maximum increase in shear strength (from 72 MPa to 87 MPa) is observed for GFRP based on the EO + 15 wt.% PSU matrix. For GFRP based on EO + 20 wt.% PES, the shear strength is reduced to 69 MPa. The opposite effect is observed for the EO + 20 wt.% PES matrix, where the strength value decreases from 164 MPa to 75 MPa, and the energy decreases from 32 kJ/m² to 10 kJ/m². The reference value for the fracture energy of GFRP 615 is 741 kJ/m². The maximum fracture energy for GFRP is based on EO + 20 wt.% PSU increases to 832 kJ/m² for GFRP based on EO + 20 wt.% PES—up to 950 kJ/m². The study of the morphology of the fracture surfaces of matrices and GFRP confirmed the dependence of impact characteristics on the microstructure of the modified matrices and the degree of involvement in the process of crack formation. The greatest effect is achieved for matrices with a phase structure “thermoplastic matrix-epoxy dispersion.” Correlations between the fracture energy and strength of EO + PES matrices and GFRP have been established. Full article

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7 pages, 196 KiB

Open AccessEditorial

Reinforced Polymer Composites III

by Victor V. Tcherdyntsev

Polymers 2023, 15(9), 2069; https://doi.org/10.3390/polym15092069 - 27 Apr 2023

Cited by 1 | Viewed by 3505

Abstract

The development of modern technology requires the development of new materials with improved operational and technological properties [...] Full article

15 pages, 4160 KiB

Open AccessArticle

Optimization of Compression and Flexural Properties of Masonry Veneers with Recycled PET-1

by Juan Paredes, Willan Castillo, Gabriela Salinas, Henry Erazo and Víctor H. Guerrero

Polymers 2023, 15(5), 1122; https://doi.org/10.3390/polym15051122 - 23 Feb 2023

Viewed by 2208

Abstract

The study of new materials formulated using recycled polymers offers an ecological and sustainable alternative for the construction industry. In this work, we optimized the mechanical behavior of manufactured masonry veneers made from concrete reinforced with recycled polyethylene terephthalate (PET) from discarded plastic [...] Read more.

The study of new materials formulated using recycled polymers offers an ecological and sustainable alternative for the construction industry. In this work, we optimized the mechanical behavior of manufactured masonry veneers made from concrete reinforced with recycled polyethylene terephthalate (PET) from discarded plastic bottles. For this purpose, we used the response surface methodology to evaluate the compression and flexural properties. PET percentage, PET size and aggregate size were used as input factors in a Box–Behnken experimental design resulting in a total of 90 tests. The fraction of the commonly used aggregates replaced by PET particles was 15%, 20% and 25%. The nominal size of the PET particles used was 6, 8 and 14 mm, while the size of the aggregates was 3, 8 and 11 mm. The function of desirability was used to optimize response factorials. The globally optimized formulation contained 15% of 14 mm PET particles in the mixture, and 7.36 mm aggregates, obtaining important mechanical properties of this characterization of masonry veneers. The flexural strength (four-point) was 1.48 MPa, and the compression strength was 3.96 MPa; these values show property improvements of 110% and 94%, respectively, compared to commercial masonry veneers. Overall, this offers the construction industry a robust and environmentally friendly alternative. Full article

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25 pages, 88431 KiB

Open AccessArticle

Analysis of the Effect of Fiber Orientation on Mechanical and Elastic Characteristics at Axial Stresses of GFRP Used in Wind Turbine Blades

by Ciprian Ionuț Morăraș, Viorel Goanță, Dorin Husaru, Bogdan Istrate, Paul Doru Bârsănescu and Corneliu Munteanu

Polymers 2023, 15(4), 861; https://doi.org/10.3390/polym15040861 - 9 Feb 2023

Cited by 6 | Viewed by 2334

Abstract

Due to its physical and mechanical properties, glass-fiber-reinforced polymer (GFRP) is utilized in wind turbine blades. The loads given to the blades of wind turbines, particularly those operating offshore, are relatively significant. In addition to the typical static stresses, there are also large [...] Read more.

Due to its physical and mechanical properties, glass-fiber-reinforced polymer (GFRP) is utilized in wind turbine blades. The loads given to the blades of wind turbines, particularly those operating offshore, are relatively significant. In addition to the typical static stresses, there are also large dynamic stresses, which are mostly induced by wind-direction changes. When the maximum stresses resulting from fatigue loading change direction, the reinforcing directions of the material used to manufacture the wind turbine blades must also be considered. In this study, sandwich-reinforced GFRP materials were subjected to tensile testing in three directions. The parameters of the stress–strain curve were identified and identified based on the three orientations in which samples were cut from the original plate. Strain gauge sensors were utilized to establish the three-dimensional elasticity of a material. After a fracture was created by tensile stress, SEM images were taken to highlight the fracture’s characteristics. Using finite element analyses, the stress–strain directions were determined. In accordance to the three orientations and the various reinforcements used, it was established that the wind turbine blades are operational. Full article

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23 pages, 6083 KiB

Open AccessFeature PaperArticle

Assessing Mechanical Properties of Jute, Kenaf, and Pineapple Leaf Fiber-Reinforced Polypropylene Composites: Experiment and Modelling

by M. M. Alamgir Sayeed, Abu Sadat Muhammad Sayem, Julfikar Haider, Sharmin Akter, Md. Mahmudul Habib, Habibur Rahman and Sweety Shahinur

Polymers 2023, 15(4), 830; https://doi.org/10.3390/polym15040830 - 7 Feb 2023

Cited by 20 | Viewed by 3821

Abstract

The application of natural fibers is increasing rapidly in the polymer-based composites. This study investigates manufacturing and characterization of polypropylene (PP) based composites reinforced with three different natural fibers: jute, kenaf, and pineapple leaf fiber (PALF). In each case, the fiber weight percentages [...] Read more.

The application of natural fibers is increasing rapidly in the polymer-based composites. This study investigates manufacturing and characterization of polypropylene (PP) based composites reinforced with three different natural fibers: jute, kenaf, and pineapple leaf fiber (PALF). In each case, the fiber weight percentages were varied by 30 wt.%, 35 wt.%, and 40 wt.%. Mechanical properties such as tensile, flexural, and impact strengths were determined by following the relevant standards. Fourier transform infrared (FTIR) spectroscopy was employed to identify the chemical interactions between the fiber and the PP matrix material. Tensile strength and Izod impact strength of the composites significantly increased for all the composites with different fiber contents when compared to the pure PP matrix. The tensile moduli of the composites were compared to the values obtained from two theoretical models based on the modified “rule of mixtures” method. Results from the modelling agreed well with the experimental results. Tensile strength (ranging from 43 to 58 MPa), flexural strength (ranging from 53 to 67 MPa), and impact strength (ranging from 25 to 46 kJ/m²) of the composites significantly increased for all the composites with different fiber contents when compared to the pure PP matrix having tensile strength of 36 MPa, flexural strength of 53 Mpa, and impact strength of 22 kJ/m². Furthermore, an improvement in flexural strength but not highly significant was found for majority of the composites. Overall, PALF-PP displayed better mechanical properties among the composites due to the high tensile strength of PALF. In most of the cases, T₉₈ (degradation temperature at 98% weight loss) of the composite samples was higher (532–544 °C) than that of 100% PP (500 °C) matrix. Fractured surfaces of the composites were observed in a scanning electron microscope (SEM) and analyses were made in terms of fiber matrix interaction. This comparison will help the researcher to select any of the natural fiber for fiber-based reinforced composites according to the requirement of the final product. Full article

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17 pages, 3402 KiB

Open AccessArticle

Deformation Behavior of Single Carbon Fibers Impregnated with Polysulfone by Polymer Solution Method

by Andrey A. Stepashkin, Hussam Mohammad, Elena D. Makarova, Yulia V. Odintsova, Alexander I. Laptev and Victor V. Tcherdyntsev

Polymers 2023, 15(3), 570; https://doi.org/10.3390/polym15030570 - 22 Jan 2023

Cited by 8 | Viewed by 2451

Abstract

Tensile deformation behavior of continuous high-strength and high-modulus single carbon fibers impregnated with a polysulfone solution was investigated. The effect of the carbon fiber type, mass fraction of the polymer, and the loading rate on the tensile strength was studied. It was observed [...] Read more.

Tensile deformation behavior of continuous high-strength and high-modulus single carbon fibers impregnated with a polysulfone solution was investigated. The effect of the carbon fiber type, mass fraction of the polymer, and the loading rate on the tensile strength was studied. It was observed that, whereas for high-modulus carbon fibers the magnitude of tensile strength depends significantly on the loading rate, for high-strength carbon fibers, such dependence was nearly not observed. SEM study shows that at low loading rates, elementary filaments inside the impregnated fiber are able to align themselves along the load application axis because a thermoplastic matrix can flow under the tensile stresses’ force. As a result, the fiber’s strength properties can be realized more effectively in the thermoplastic-based composites than in the same composite with an epoxy matrix. Full article

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2022

Jump to: 2023, 2021, 2020, 2019

13 pages, 1893 KiB

Open AccessArticle

Investigation of Thermal Properties of Zr-Based Metallic Glass–Polymer Composite with the Addition of Silane

by Adit Sharma, Dmitry Muratov, Mikhail Zadorozhnyy, Andrey Stepashkin, Andrey Bazlov, Artem Korol, Ruslan Sergiienko, Victor Tcherdyntsev and Vladislav Zadorozhnyy

Polymers 2022, 14(17), 3548; https://doi.org/10.3390/polym14173548 - 29 Aug 2022

Cited by 5 | Viewed by 2230

Abstract

Composites based on Zr₆₅Cu_17.5Ni₁₀Al_7.5/PTFE (polytetrafluoroethylene) with silane were prepared by ball milling with subsequent thermal pressing. Silanization was performed in the alcoholic solution with metallic glass powder. Different composites, 30/70 and 50/50 with silane, were [...] Read more.

Composites based on Zr₆₅Cu_17.5Ni₁₀Al_7.5/PTFE (polytetrafluoroethylene) with silane were prepared by ball milling with subsequent thermal pressing. Silanization was performed in the alcoholic solution with metallic glass powder. Different composites, 30/70 and 50/50 with silane, were prepared. During ball milling, Zr₂Cu and Zr₂Ni intermetallic phases were formed. The Zr-based metallic glass had a large supercooled region, and the melting point of the 30/70 and 50/50 composites with silane was near to the melting point of PTFE. The 50/50 composite (silane) had the highest thermal conductivity compared to the 30/70 composite samples. The incorporation of silane in metallic glass/polymer was investigated by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analysis. Thermogravimetric analysis (TGA) showed the thermal stability of the composite samples up to 450–460 °C. It was also concluded that the 50/50 composite with silane has better thermal stability than the 30/70 composite with silane. The addition of silane in 30/70 and 50/50 composites increased the thermal conductivity compared to the composites without silane. Full article

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20 pages, 6652 KiB

Open AccessArticle

Mechanical and Thermophysical Properties of Carbon Fiber-Reinforced Polyethersulfone

by Valerii G. Torokhov, Dilyus I. Chukov, Victor V. Tcherdyntsev, Galal Sherif, Mikhail Y. Zadorozhnyy, Andrey A. Stepashkin, Ilya I. Larin and Elena V. Medvedeva

Polymers 2022, 14(14), 2956; https://doi.org/10.3390/polym14142956 - 21 Jul 2022

Cited by 15 | Viewed by 4787

Abstract

In this study, the mechanical and thermophysical properties of carbon fiber-reinforced polyethersulfone are investigated. To enhance the interfacial interaction between carbon fibers and the polymer matrix, the surface modification of carbon fibers by thermal oxidation is conducted. By means of AFM and X-ray [...] Read more.

In this study, the mechanical and thermophysical properties of carbon fiber-reinforced polyethersulfone are investigated. To enhance the interfacial interaction between carbon fibers and the polymer matrix, the surface modification of carbon fibers by thermal oxidation is conducted. By means of AFM and X-ray spectroscopy, it is determined that surface modification changes the morphology and chemical composition of carbon fibers. It is shown that surface modification dramatically increases the mechanical properties of the composites. Thus, flexural strength and the E-modulus of the composites reinforced with modified fibers reached approximately 962 MPa and 60 GPa, respectively, compared with approximately 600 MPa and 50 GPa for the composites reinforced with the initial ones. The heat deflection temperatures of the composites reinforced with the initial and modified fibers were measured. It is shown that composites reinforced with modified fibers lose their stability at temperatures of about 211 °C, which correlates with the glass transition temperature of the PES matrix. The thermal conductivity of the composites with different fiber content is investigated in two directions: in-plane and transverse to layers of carbon fibers. The obtained composites had a relatively high realization of the thermal conductive properties of carbon fibers, up to 55–60%. Full article

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16 pages, 4653 KiB

Open AccessArticle

Mechanical Properties of Bambusa Oldhamii and Yushania-Alpina Bamboo Fibres Reinforced Polypropylene Composites

by Yalew Dessalegn, Balkeshwar Singh, Aart W. van Vuure, Ali A. Rajhi, Alaauldeen A. Duhduh, Nazia Hossain and Gulam Mohammed Sayeed Ahmed

Polymers 2022, 14(13), 2733; https://doi.org/10.3390/polym14132733 - 4 Jul 2022

Cited by 3 | Viewed by 2237

Abstract

The current studies aim to measure the mechanical strength based on age, harvesting season and bamboo species in Ethiopia. The bamboo fibres are extracted using a roll milling machine, which was developed by the author. The age groups (1, 2 and 3 years), [...] Read more.

The current studies aim to measure the mechanical strength based on age, harvesting season and bamboo species in Ethiopia. The bamboo fibres are extracted using a roll milling machine, which was developed by the author. The age groups (1, 2 and 3 years), harvesting months (February and November), and bamboo species (Yushania alpina and Bambusa oldhamii) are the parameters of the current research studies. Prepregs and composites were produced from bamboo fibres and polypropylene. The mechanical properties of bamboo fibres and their composites in Ethiopia have not been investigated by researchers for the composite application so far. The tensile strength, Young’s modulus, and impact strength of injibara (Y. alpina) bamboo fibres reinforced PP composites from the ages of 1– 3 years old in November is 111 ± 9–125 ± 8 MPa, 15 ± 0.9–25 ± 0.72 GPa, and 47 ± 5 KJ/m²–57 ± 6 KJ/m², whereas, in February, it is 86 ± 3.86–116 ± 10 MPa, 11 ± 0.71–23 ± 1.5 GPa, and 34 ± 4–52 ± 6 KJ/m², respectively. Moreover, Kombolcha (B. oldhamii), bamboo fibres reinforced PP composites in November are 93 ± 7–111 ± 8 MPa, 7 ± 0.51–17 ± 2.56 GPa, and 39 ± 4–44 ± 5 KJ/m², whereas, in February, it is 60 ± 5–104 ± 10 MPa, 12 ± 0.95–14 ± 0.92 GPa, and 26 ± 3 KJ/m²–38 ± 4 KJ/m², respectively. Furthermore, Mekaneselam (Y. alpina) bamboo fibres reinforced PP composites in November are 99 ± 8–120 ± 11 MPa, 9 ± 0.82–16 ± 1.85 GPa, and 37 ± 4 KJ/m²–46 ± 5 KJ/m², whereas, in February, it is 91 ± 8–110 ± 9 MPa, 8 ± 0.75–14 ± 1.86 GPa, and 34 ± 3 KJ/m²–40 ± 4 KJ/m², respectively. At two years, November and Injibara bamboo have recorded the highest mechanical properties in the current research studies. Bamboo fiber strength in Ethiopia is comparable to the previous study of bamboo fibres and glass fibres used for composite materials in the automotive industry. Full article

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18 pages, 6952 KiB

Open AccessArticle

Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection

by Wenda Song, Zhengzhi Mu, Yufei Wang, Zhiyan Zhang, Shuang Zhang, Ze Wang, Bo Li, Junqiu Zhang, Shichao Niu, Zhiwu Han and Luquan Ren

Polymers 2022, 14(13), 2552; https://doi.org/10.3390/polym14132552 - 23 Jun 2022

Cited by 7 | Viewed by 2618

Abstract

Rotor plays a vital role in the dynamical system of an unmanned aerial vehicle (UAV). Prominent aerodynamic and acoustic performance are a long-term pursuit for the rotor. Inspired by excellent quiet flight characteristics of owls, this work adopted bionic edge design and rational [...] Read more.

Rotor plays a vital role in the dynamical system of an unmanned aerial vehicle (UAV). Prominent aerodynamic and acoustic performance are a long-term pursuit for the rotor. Inspired by excellent quiet flight characteristics of owls, this work adopted bionic edge design and rational material selection strategy to improve aerodynamic and acoustic performance of the rotor. A reference model of rotor prototype with streamlined edges was firstly generated by reverse engineering method. With inspiration from owl wings and feathers, bionic rotors with rational design on leading and trailing edges were obtained. Original and bionic rotors were fabricated with polyamide PA 12 and Resin 9400 by 3D printing technique. Aerodynamic and acoustic performance of the as-fabricated rotors were experimentally measured and analyzed in detail using a self-established test system. Comparative experimental results indicated that the aerodynamic and acoustic performance of the rotors was closely related to the bionic structures, material properties, and rotational speeds. At the same rotational speed, bionic rotor fabricated with Resin 9400 can produce a higher thrust than the prototype one and its power consumption was also reduced. The resulting noise of different bionic rotors and their directivities were comparatively investigated. The results verified the bionic edge design strategy can effectively control the turbulent flow field and smoothly decompose the airflow near the tailing edge, which resulting in enhancing the thrust and reducing the noise. This work could provide beneficial inspiration and strong clues for mechanical engineers and material scientists to design new abnormal rotors with promising aerodynamic and acoustic performance. Full article

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12 pages, 4123 KiB

Open AccessArticle

Fracture Toughness of Moldable Low-Temperature Carbonized Elastomer-Based Composites Filled with Shungite and Short Carbon Fibers

by Semen D. Ignatyev, Eugene S. Statnik, Dmitriy Yu. Ozherelkov, Dmitry D. Zherebtsov, Alexey I. Salimon, Dilyus I. Chukov, Victor V. Tcherdyntsev, Andrey A. Stepashkin and Alexander M. Korsunsky

Polymers 2022, 14(9), 1793; https://doi.org/10.3390/polym14091793 - 27 Apr 2022

Cited by 3 | Viewed by 2836

Abstract

This work evaluated the fracture toughness of the low-temperature carbonized elastomer-based composites filled with shungite and short carbon fibers. The effects of the carbonization temperature and filler content on the critical stress intensity factor (K_1c) were examined. The K [...] Read more.

This work evaluated the fracture toughness of the low-temperature carbonized elastomer-based composites filled with shungite and short carbon fibers. The effects of the carbonization temperature and filler content on the critical stress intensity factor (K_1c) were examined. The K_1c parameter was obtained using three-point bending tests for specimens with different l/b ratio (notch depth to sample thickness) ranging from 0.2 to 0.4. Reliable detection of the initiation and propagation of cracks was achieved using an acoustic sensor was attached to the samples during the bending test. The critical stress intensity factor was found to decrease linearly with increasing carbonization temperature. As the temperature increased from 280 to 380 °C, the K_1c parameter was drastically reduced from about 5 to 1 MPa·m^1/2 and was associated with intense outgassing during the carbonization step that resulted in sample porosity. The carbon fiber addition led to some incremental toughening; however, it reduced the statistical dispersion of the K_1c values. Full article

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18 pages, 4170 KiB

Open AccessArticle

Expandable Graphite as a Multifunctional Flame-Retarding Additive for Highly Filled Thermal Conductive Polymer Formulations

by Florian Tomiak, Kevin Schneider, Angelina Schoeffel, Klaus Rathberger and Dietmar Drummer

Polymers 2022, 14(8), 1613; https://doi.org/10.3390/polym14081613 - 15 Apr 2022

Cited by 9 | Viewed by 2768

Abstract

Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. [...] Read more.

Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. It is demonstrated that thermal conductivity can significantly influence the time to ignition, although offering little fire resistance once ignited even in highly filled systems. Thus, for PA6 formulations containing solely 70 wt.% G, the peak heat release rate (pHRR) measured in cone calorimeter tests was 193 kW/m², whereas PA6 formulations containing 20 wt.% EG/50 wt.% G did not exhibit a measurable heat development. Particular attention was paid to effect separation between thermal conductivity and residue formation. Good thermal conductivity properties are proven to be particularly effective in test scenarios where the heat impact is comparatively low and the testing environment provides good heat dissipation and convective cooling possibilities. For candle-like ignition scenarios (e.g., LOI), filling levels of >50 wt.% (G or EG/G) are shown to be sufficient to suppress ignition exclusively by thermal conductivity. V0 classifications in UL-94 vertical burning tests were achieved for PA6 formulations containing ≥70 wt.% G, ≥25 wt.% EG and ≥20 wt.% EG/25 wt.% G. Full article

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22 pages, 8415 KiB

Open AccessArticle

Oil-Based Mud Waste as a Filler Material in LDPE Composites: Evaluation of Mechanical Properties

by Shohel Siddique, Adam Novak, Emin Guliyev, Kyari Yates, Pak Sing Leung and James Njuguna

Polymers 2022, 14(7), 1455; https://doi.org/10.3390/polym14071455 - 2 Apr 2022

Cited by 1 | Viewed by 2458

Abstract

Traditionally, the drilling waste generated in oil and gas exploration operations, including spent drilling fluid, is disposed of or treated by several methods, including burial pits, landfill sites and various thermal treatments. This study investigates drilling waste valorisation and its use as filler [...] Read more.

Traditionally, the drilling waste generated in oil and gas exploration operations, including spent drilling fluid, is disposed of or treated by several methods, including burial pits, landfill sites and various thermal treatments. This study investigates drilling waste valorisation and its use as filler in polymer composites. The effect of the poor particle/polymer interfacial adhesion bonding of the suspended clay in oil-based mud (OBM) slurry and the LDPE matrix is believed to be the main reason behind the poor thermo-mechanical and mechanical properties of low-density polyethylene (LDPE)/OBM slurry nanocomposites. The thermo-mechanical and mechanical performances of LDPE)/OBM slurry nanocomposites without the clay surface treatment and without using compatibilizer are evaluated and discussed. In our previous studies, it has been observed that adding thermally treated reclaimed clay from OBM waste in powder form improves both the thermal and mechanical properties of LDPE nanocomposites. However, incorporating OBM clay in slurry form in the LDPE matrix can decrease the thermal stability remarkably, which was reported recently, and thereby has increased the interest to identify the mechanical response of the composite material after adding this filler. The results show the severe deterioration of the tensile and flexural properties of the LDPE/OBM slurry composites compared to those properties of the LDPE/MMT nanocomposites in this study. It is hypothesised, based on the observation of the different test results in this study, that this deterioration in the mechanical properties of the materials was associated with the poor Van der Waals force between the polymer molecules/clay platelets and the applied force. The decohesion between the matrix and OBM slurry nanoparticles under stress conditions generated stress concentration through the void area between the matrix and nanoparticles, resulting in sample failure. Interfacial adhesion bonding appears to be a key factor influencing the mechanical properties of the manufactured nanocomposite materials. Full article

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21 pages, 9738 KiB

Open AccessArticle

Effect of Adding Pyrolysis Carbon Black (CBp) on Soft Friction and Metal Wear during Mixing

by Yiren Pan, Yi Pan, Zhilin Wang, Shuang Han, Wenwen Han and Huiguang Bian

Polymers 2022, 14(7), 1319; https://doi.org/10.3390/polym14071319 - 24 Mar 2022

Cited by 2 | Viewed by 1868

Abstract

In the cracking process of waste tires, pyrolysis carbon black (CBp), as a solid product, accounts for about 35% of the total tire rubber content. Here, the treated CBp has been gradually applied to the tire formula to improve the recycling efficiency of [...] Read more.

In the cracking process of waste tires, pyrolysis carbon black (CBp), as a solid product, accounts for about 35% of the total tire rubber content. Here, the treated CBp has been gradually applied to the tire formula to improve the recycling efficiency of waste tires. This study elucidated the influence of adding CBp during the tire mixing process on soft friction and metal wear. Compared with industrial carbon black (I-CB), the friction coefficient of CBp was smaller at different mixing stages, and the ripple caused by adhesion friction was not evident. After the modified CBp (M-CBp) was obtained by implementing the surface activation of common CBp (C-CBp), the friction coefficient between M-CBp and metal increased by 10%, while the filler dispersion and comprehensive mechanical properties showed an upward trend. The wear rate of metal was higher than that observed after adding I-CB during the same mixing mode; thus, it was necessary to strengthen the wear resistance of the inner-wall surface of the mixing chamber. The –OH group on the M-CBp surface can also participate in the silane coupling reaction and aggravate the metal wear of the mixer chamber wall. Through a comparison of results, the mixing friction coefficient can reflect the strength of filler–rubber interaction, which in turn can preliminarily represent the dispersion effect and comprehensive properties, reveal the reason behind the poor performance of CBp, and highlight the need for modification from the perspective of tribology. Full article

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20 pages, 3882 KiB

Open AccessArticle

Expandable Graphite, Aluminum Diethylphospinate and Melamine Polyphosphate as Flame Retarding System in Glass Fiber-Reinforced PA6

by Florian Tomiak, Angelina Schoeffel, Klaus Rathberger and Dietmar Drummer

Polymers 2022, 14(6), 1263; https://doi.org/10.3390/polym14061263 - 21 Mar 2022

Cited by 13 | Viewed by 2995

Abstract

A flame retardant system based on expandable graphite (EG), aluminum diethylphosphinate (AlPI) and melamine polyphosphate (MPP) was investigated in glass fiber- (GF) reinforced polyamide 6 (PA6). Burning characteristics were evaluated via cone calorimeter, limiting oxygen index (LOI) and UL-94 tests. Thermogravimetric analysis (TGA) [...] Read more.

A flame retardant system based on expandable graphite (EG), aluminum diethylphosphinate (AlPI) and melamine polyphosphate (MPP) was investigated in glass fiber- (GF) reinforced polyamide 6 (PA6). Burning characteristics were evaluated via cone calorimeter, limiting oxygen index (LOI) and UL-94 tests. Thermogravimetric analysis (TGA) and coupled Fourier transform infrared spectroscopy (FTIR) was used to investigate the decomposition process as well as flame retardant modes of actions. Specifically, in the cone calorimeter tests, formulations containing EG showed excellent flame retardant properties for non-reinforced and reinforced PA6. The best performance was achieved for 25 wt.% glass fiber-reinforced PA6 containing solely 20 wt.% EG, corresponding to a measured pHRR of 134 kW/m² and a total smoke production of 1.2 m². Higher glass fiber contents of 45 wt.% (30 vol.%) revealed a lower char volume, which was attributed to both the limited space available for expansion and the sheer-induced reduction in particle size during processing. All of the reinforced PA6 formulations only achieved V2 classifications, but this was at low filling degrees (10 wt.%) for both net EG or EG/AlPi/MPP combinations. For GF-reinforced PA6 containing EG/AlPi/MPP mixtures, a synergistic effect was found to improve the oxygen index up to 30.6%. Full article

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16 pages, 66359 KiB

Open AccessArticle

Influence of Filament Winding Tension on the Deformation of Composite Flywheel Rotors with H-Shaped Hubs

by Xiaodong Chen, Yong Li, Dajun Huan, Hongquan Liu, Lisa Li and Yanrui Li

Polymers 2022, 14(6), 1155; https://doi.org/10.3390/polym14061155 - 14 Mar 2022

Cited by 5 | Viewed by 3630

Abstract

The residual stress plays an important role in composite flywheel rotors composed of filament windings. The fiber tension during high-prestressed winding is the main source of the rotor deformation and residual stress of composite layers. In this study, the effect of the winding [...] Read more.

The residual stress plays an important role in composite flywheel rotors composed of filament windings. The fiber tension during high-prestressed winding is the main source of the rotor deformation and residual stress of composite layers. In this study, the effect of the winding tension gradient on deformation was monitored in real-time. Two types of in-plane winding tension fluctuation methods were developed to investigate the effect of tension on deformation. Online and offline measurements were performed for the strain acquisition. A wireless strain instrument was used for online deformation monitoring and a laser scanner was used for the offline surface reconstruction. Additionally, different filament winding strategies were carried out to improve the efficiency of the winding tension by finite element analysis. The results indicated that the deviation between numerical and experimental results was within 8%. Based on the proposed numerical method, the influence of the in-plane and out-of-plane winding tension gradient distributions on the rotation process of the H-shaped rotor was analyzed. An in-plane winding strategy with variable tension was developed, which increased the initial failure speed by 160%. Full article

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17 pages, 3725 KiB

Open AccessArticle

Characterizing the Structural Behavior of FRP Profiles—FRCM Hybrid Superficial Elements: Experimental and Numerical Studies

by Amir Reza Eskenati, Amir Mahboob, Ernest Bernat-Maso and Lluís Gil

Polymers 2022, 14(6), 1076; https://doi.org/10.3390/polym14061076 - 8 Mar 2022

Cited by 3 | Viewed by 1948

Abstract

Composite materials have been increasingly used to produce hybrid structures together with concrete. This system is commonly applied to bridges and roof structures. The main idea of the current research was to extend this approach by replacing the concrete with a fabric-reinforced cementitious [...] Read more.

Composite materials have been increasingly used to produce hybrid structures together with concrete. This system is commonly applied to bridges and roof structures. The main idea of the current research was to extend this approach by replacing the concrete with a fabric-reinforced cementitious matrix (FRCM) composite, resulting in a combination of composite materials. The main aim was to characterize the structural behavior of fiber-reinforced polymer (FRP) profiles and FRCM hybrid superficial elements. Two different prototypes of the hybrid superficial structural typology were tested to cover bidimensional and three-dimensional application cases of the proposed technology. After mortar cracking, the experimental results revealed a ductile response and a high mechanical capacity. A finite element model was implemented, calibrated, and validated by comparing numerical data with experimental results of the two prototypes. The output was a validated model that correctly captured the characteristic response of the proposed technology, which consisted of changing the structural response from a stiff plate configuration to a membrane type due to cracking of the FRCM composite part of the full solution. The suggested numerical model adequately reflected the experimental response and proved valuable for understanding and explaining the resistive processes established along this complicated FRP-FRCM hybrid structure. Full article

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14 pages, 7722 KiB

Open AccessArticle

Effect of CuO and Graphene on PTFE Microfibers: Experimental and Modeling Approaches

by Maroof A. Hegazy, Hend A. Ezzat, Ibrahim S. Yahia, Heba Y. Zahran, Hanan Elhaes, Islam Gomaa and Medhat A. Ibrahim

Polymers 2022, 14(6), 1069; https://doi.org/10.3390/polym14061069 - 8 Mar 2022

Cited by 18 | Viewed by 2720

Abstract

The surface of pure polytetrafluoroethylene (PTFE) microfibers was modified with ZnO and graphene (G), and the composite was studied using ATR-FTIR, XRD, and FESEM. FTIR results showed that two significant bands appeared at 1556 cm⁻¹ and 515 cm⁻¹ as indications for [...] Read more.

The surface of pure polytetrafluoroethylene (PTFE) microfibers was modified with ZnO and graphene (G), and the composite was studied using ATR-FTIR, XRD, and FESEM. FTIR results showed that two significant bands appeared at 1556 cm⁻¹ and 515 cm⁻¹ as indications for CuO and G interaction. The SEM results indicated that CuO and G were distributed uniformly on the surface of the PTFE microfibers, confirming the production of the PTFE/CuO/G composite. Density functional theory (DFT) calculations were performed on PTFE polymer nanocomposites containing various metal oxides (MOs) such as MgO, Al₂O₃, SiO₂, TiO₂, Fe₃O₄, NiO, CuO, ZnO, and ZrO₂ at the B3LYP level using the LAN2DZ basis set. Total dipole moment (TDM) and HOMO/LUMO bandgap energy ΔE both show that the physical and electrical characteristics of PTFE with OCu change to 76.136 Debye and 0.400 eV, respectively. PTFE/OCu was investigated to observe its interaction with graphene quantum dots (GQDs). The results show that PTFE/OCu/GQD ZTRI surface conductivity improved significantly. As a result, the TDM of PTFE/OCu/GQD ZTRI and the HOMO/LUMO bandgap energy ΔE were 39.124 Debye and ΔE 0.206 eV, respectively. The new electrical characteristics of PTFE/OCu/GQD ZTRI indicate that this surface is appropriate for electronic applications. Full article

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19 pages, 3819 KiB

Open AccessArticle

Experimental and Numerical Study of Adhesively and Bolted Connections of Pultruded GFRP I-Shape Profiles

by Amir Reza Eskenati, Amir Mahboob, Ernest Bernat-Maso and Lluís Gil

Polymers 2022, 14(5), 894; https://doi.org/10.3390/polym14050894 - 24 Feb 2022

Cited by 8 | Viewed by 2425

Abstract

Recent developments indicate that the application of pultruded FRP profiles has been continuously growing in the construction industry. Generating more complex structures composed of pultruded FRP profiles requires joining them. In particular, I-shape glass fiber pultruded profiles are commonly used and the possible [...] Read more.

Recent developments indicate that the application of pultruded FRP profiles has been continuously growing in the construction industry. Generating more complex structures composed of pultruded FRP profiles requires joining them. In particular, I-shape glass fiber pultruded profiles are commonly used and the possible joints to connect them should be specifically studied. The mechanical behavior of adhesively and bolted joints for pultruded Glass FRP (GFRP) profiles has been experimentally addressed and numerically modeled. A total of nine specimens with different configurations (bolted joints, adhesive joints, web joints, web and flange joints, and two different angles between profiles) were fabricated and tested, extending the available published information. The novelty of the research is in the direct comparison of joint technologies (bolted vs. adhesive), joint configuration (web vs. flange + web) and angles between profiles in a comprehensive way. Plates for flange joints were fabricated with carbon fiber FRP. Experimental results indicate that adding the bolted flange connection allowed for a slight increase of the load bearing capacity (up to 15%) but a significant increase in the stiffness (between 2 and 7 times). Hence, it is concluded that using carbon FRP bolted flange connection should be considered when increasing the joint stiffness is sought. Adhesively connections only reached 25% of the expected shear strength according to the adhesive producer if comparing the numerically calculated shear strength at the failure time with the shear strength capacity of the adhesive. Apart from assessing adhesive connections, the implemented 3D numerical model was aimed at providing a simplified effective tool to effectively design bolted joints. Although the accurate fitting between experimental and numerical results of the mechanical response, especially the stiffness of the joint, the local failure experimentally observed was not automatically represented by the model, because of the simplified definition of the materials oriented to make the model available for a wide range of practitioners. Full article

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18 pages, 5051 KiB

Open AccessArticle

Ductility Enhancement of Sustainable Fibrous-Reinforced High-Strength Lightweight Concrete

by Md. Akter Hosen, Mahaad Issa Shammas, Sukanta Kumer Shill, Safat Al-Deen, Mohd Zamin Jumaat and Huzaifa Hashim

Polymers 2022, 14(4), 727; https://doi.org/10.3390/polym14040727 - 14 Feb 2022

Cited by 18 | Viewed by 3233

Abstract

To limit the cross-sectional size of concrete structures, high-strength, lightweight concrete is preferred for the design and construction of structural elements. However, the main drawback of high-strength, lightweight concrete is its brittleness over normal-weight concrete. The ductility of concrete is a crucial factor, [...] Read more.

To limit the cross-sectional size of concrete structures, high-strength, lightweight concrete is preferred for the design and construction of structural elements. However, the main drawback of high-strength, lightweight concrete is its brittleness over normal-weight concrete. The ductility of concrete is a crucial factor, which plays an important role when the concrete structures are subjected to extreme situations, such as earthquakes and wind. This study aims to improve the ductility of high-strength, lightweight concrete by incorporating steel fibers. The palm oil clinker (POC)-based, high-strength, lightweight concrete specimens reinforced with steel fibers were prepared and their ductility was systematically examined. POC was used as aggregates and supplementary cementitious materials. Steel fibers from 0–1.50% (by volume), with an increment of 0.5%, were used in the concrete mix. Compression ductility, displacement ductility and energy ductility were used as indicators to evaluate the enhancement of ductility. Moreover, the compressive strength, flexural strength, stress-strain behavior, modulus of elasticity, load-displacement characteristics, energy absorption capacity and deformability of the concrete samples were investigated. The compression ductility, displacement ductility and energy ductility indexes were found to be increased by up to 472%, 140% and 568% compared to the control specimens (concrete with 0% steel fibers), respectively. Moreover, the deformability and energy absorption capacity of the concrete were increased by up to 566% and 125%, respectively. Therefore, POC-based, high-strength, fibrous, lightweight concrete could perform better than conventional concrete under extreme loading conditions as it showed significantly higher ductility. Full article

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16 pages, 7745 KiB

Open AccessArticle

Performance Investigation and Cost–Benefit Analysis of Recycled Tire Polymer Fiber-Reinforced Cemented Paste Backfill

by Zhuoqun Yu, Yongyan Wang and Jianguang Li

Polymers 2022, 14(4), 708; https://doi.org/10.3390/polym14040708 - 12 Feb 2022

Cited by 10 | Viewed by 2422

Abstract

To alleviate the environmental problems caused by scrap tire and tailings disposal, the performance of recycled tire polymer fiber (RTPF)-reinforced cemented paste backfill (CPB) was investigated. Ordinary CPB, commercial poly-propylene fiber (CPPF) and reinforced CPB were also investigated for comparison. Slump tests, unconfined [...] Read more.

To alleviate the environmental problems caused by scrap tire and tailings disposal, the performance of recycled tire polymer fiber (RTPF)-reinforced cemented paste backfill (CPB) was investigated. Ordinary CPB, commercial poly-propylene fiber (CPPF) and reinforced CPB were also investigated for comparison. Slump tests, unconfined compression tests and a cost–benefit analysis were conducted. The results indicate that the flowability of the RTPF-reinforced CPB decreased with the increasing fiber content. The failure strain, unconfined compressive strength, and toughness values were generally higher than that of ordinary CPB (i.e., CPB without any fiber reinforcement). However, the mechanical properties would not be improved continuously with increasing RTPF content. It was found that the inclusion of RTPFs achieved the best improvement effect with the best mechanical properties of CPB at the fiber content of 0.6%. The failure mode of the RTPF-reinforced CPB was safer than that of the ordinary CPB. Microscopic observations indicated that the bond between RTPFs and the CPB matrix could affect the mechanical properties of the RTPF-reinforced CPB. From the cost–benefit analysis, the inclusion of RTPFs to reinforce CPB could gain relatively high mechanical properties with a low material cost. Full article

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17 pages, 5859 KiB

Open AccessArticle

Numerical Investigation of the Orientability of Single Reinforcement Fibers in Polymer Matrices

by Anja Winkler, Niels Modler, Maik Gude, Yun Xu, Martin Helwig, Eike Dohmen, Axel Dittes, Dominik Höhlich and Thomas Lampke

Polymers 2022, 14(3), 534; https://doi.org/10.3390/polym14030534 - 28 Jan 2022

Cited by 6 | Viewed by 2581

Abstract

Fiber-reinforced polymers are increasingly being used, especially in lightweight structures. Here, the effective adaptation of mechanical or physical properties to the necessary application or manufacturing requirements plays an important role. In this context, the alignment of reinforcing fibers is often hindered by manufacturing [...] Read more.

Fiber-reinforced polymers are increasingly being used, especially in lightweight structures. Here, the effective adaptation of mechanical or physical properties to the necessary application or manufacturing requirements plays an important role. In this context, the alignment of reinforcing fibers is often hindered by manufacturing aspects. To achieve graded or locally adjusted alignment of different fiber lengths, common manufacturing technologies such as injection molding or compression molding need to be supported by the external non-mechanical process. Magnetic or electrostatic fields seem to be particularly suitable for this purpose. The present work shows a first simulation study of the alignment of magnetic particles in polymer matrices as a function of different parameters. The parameters studied are the viscosity of the surrounding polymer as a function of the focused processing methods, the fiber length, the thickness and permeability of the magnetic fiber coatings, and the magnetic flux density. The novelty of the presented works is in the development of an advanced simulation model that allows the simulative representation and reveal of the fluid–structure interaction, the influences of these parameters on the inducible magnetic torque and fiber alignment of a single fiber. Accordingly, the greatest influence on fiber alignment is caused by the magnetic flux density and the coating material. Full article

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17 pages, 2649 KiB

Open AccessArticle

Micromechanical Modeling for Tensile Properties of Wood Plastic Composites: Use of Pruned Waste from Pecan Orchards as Sustainable Material for Reinforcement of Thermoplastic Composite

by Juan Miguel Díaz-Mendoza, Delia J. Valles-Rosales, Young H. Park and Ronald C. Sabo

Polymers 2022, 14(3), 504; https://doi.org/10.3390/polym14030504 - 27 Jan 2022

Cited by 6 | Viewed by 2162

Abstract

Wood plastic composites (WPCs) specimens containing high-density polyethylene (HDPE) and wood pruning waste were manufactured and evaluated for their mechanical properties. Pecan waste was used as an accessible and sustainable source in this study, and the effects of its particle size and concentration [...] Read more.

Wood plastic composites (WPCs) specimens containing high-density polyethylene (HDPE) and wood pruning waste were manufactured and evaluated for their mechanical properties. Pecan waste was used as an accessible and sustainable source in this study, and the effects of its particle size and concentration on WPC strengths were evaluated. Pecan waste was milled and sieved to various particle sizes, and testing samples were fabricated by mixing them in a twin-screw extruder and injection molding. A coupling agent was used to create a stable bond between the HDPE and wood. Both tensile modulus and strength were increased with an increasing pecan flour concentration up to about 60 weigh percent. A micromechanical model is proposed for predicting the mechanical properties of the wood flour/fiber reinforce composite. This model uses a correction factor of an elliptical of carried sizes and shapes. The preliminary results of the model have a high correlation with the experimental values of the composite in all mesh sizes. Full article

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18 pages, 3816 KiB

Open AccessArticle

Effect of Graphite Filler Type on the Thermal Conductivity and Mechanical Behavior of Polysulfone-Based Composites

by Hussam Mohammad, Andrey A. Stepashkin and Victor V. Tcherdyntsev

Polymers 2022, 14(3), 399; https://doi.org/10.3390/polym14030399 - 20 Jan 2022

Cited by 21 | Viewed by 3931

Abstract

The goal of this study was to create a high-filled composite material based on polysulfone using various graphite materials. Composite material based on graphite-filled polysulfone was prepared using a solution method which allows the achievement of a high content of fillers up to [...] Read more.

The goal of this study was to create a high-filled composite material based on polysulfone using various graphite materials. Composite material based on graphite-filled polysulfone was prepared using a solution method which allows the achievement of a high content of fillers up to 70 wt.%. Alongside the analysis of the morphology and structure, the thermal conductivity and mechanical properties of the composites obtained were studied. Structural analysis shows how the type of filler affects the structure of the composites with the appearance of pores in all samples which also has a noticeable effect on composites’ properties. In terms of thermal conductivity, the results show that using natural graphite as a filler gives the best results in thermal conductivity compared to artificial and expanded graphite, with the reduction of thermal conductivity while increasing temperature. Flexural tests show that using artificial graphite as a filler gives the composite material the best mechanical load transfer compared to natural or expanded graphite. Full article

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15 pages, 4624 KiB

Open AccessArticle

Experimental Investigation of Unconfined Compression Strength and Microstructure Characteristics of Slag and Fly Ash-Based Geopolymer Stabilized Riverside Soft Soil

by Zhengdong Luo, Biao Luo, Yufei Zhao, Xinyu Li, Yonghua Su, He Huang and Qian Wang

Polymers 2022, 14(2), 307; https://doi.org/10.3390/polym14020307 - 13 Jan 2022

Cited by 17 | Viewed by 3396

Abstract

To solve the issues of insufficient early strength of cement stabilized soil and high resource cost, high reduction cost, and high environmental cost induced by the application of cement, the slag and fly ash-based geopolymer was adopted as the stabilizer to treat riverside [...] Read more.

To solve the issues of insufficient early strength of cement stabilized soil and high resource cost, high reduction cost, and high environmental cost induced by the application of cement, the slag and fly ash-based geopolymer was adopted as the stabilizer to treat riverside soft soil. This study mainly investigated the effects of stabilizer content, slag-to-fly ash ratio, and alkaline activator content on the strength of geopolymer stabilized soils with different curing ages. Unconfined compressive strength (UCS), scanning electron microscope (SEM), and X-ray energy spectrum analysis (EDS) tests were carried out. The results show that the stabilizer content, slag–fly ash ratio, and alkaline activator content have a decisive influence on the UCS of geopolymer-stabilized soil. The mix-proportions scheme of geopolymer stabilized riverside soft soil, with a geopolymer content of 15%, a slag–fly ash ratio of 80:20, and an alkaline activator content of 30%, is considered optimum. It is proven by SEM that the uniformly distributed gelatinous products formed in the geopolymer-stabilized soil bind the soil particles tightly. Moreover, the EDS analysis confirms that the gelatinous products are mainly composed of C-S-H gel and sodium-based aluminosilicate (N-A-S-H). Full article

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2021

Jump to: 2023, 2022, 2020, 2019

15 pages, 5195 KiB

Open AccessArticle

Phytic Acid Doped Polypyrrole as a Mediating Layer Promoting Growth of Prussian Blue on Cotton Fibers for Solar-Driven Interfacial Water Evaporation

by Xueyao Wang, Dongmei Yang, Xianhui An and Xueren Qian

Polymers 2022, 14(1), 6; https://doi.org/10.3390/polym14010006 - 21 Dec 2021

Cited by 4 | Viewed by 3172

Abstract

Phytic acid doped polypyrrole (PPy) as a mediating layer was in-situ coated on cotton fibers (CFs) to promote the growth of Prussian blue (PB) and construct the PB/PPy@CFs composite. The results showed that the proper amounts of PA doped PPy in-situ generated significantly [...] Read more.

Phytic acid doped polypyrrole (PPy) as a mediating layer was in-situ coated on cotton fibers (CFs) to promote the growth of Prussian blue (PB) and construct the PB/PPy@CFs composite. The results showed that the proper amounts of PA doped PPy in-situ generated significantly promoted the growth of PB on CFs, the PB deposition ratio increased from 12.29% (PB@CFs) to 32.4% (PB/PPy@CFs), and the growth of PB on PPy@CFs could be completed in 4 h. Scanning electron microscopy (SEM) showed that the PB particles with perfect nano cubic structure were formed in the composite. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) showed that both PB and PPy were successfully deposited on CFs. The PB/PPy@CFs composite had excellent light absorption, hydrophilicity, wettability, and photothermal property, and the surface could be heated up to 81.5 °C under one sun illumination. The PB/PPy@CFs composite as a photothermal conversion material was used for solar-driven interfacial water evaporation, the water evaporation rate was 1.36 kg·m⁻²·h⁻¹ at the optical concentration of 1 kW·m², and the corresponding photothermal conversion efficiency increased from 81.69% (PB@CFs) to 90.96% (PB/PPy@CFs). Full article

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23 pages, 10537 KiB

Open AccessArticle

An Assessment of ASTM E1922 for Measuring the Translaminar Fracture Toughness of Laminated Polymer Matrix Composite Materials

by Islam El-Sagheer, Amr A. Abd-Elhady, Hossam El-Din M. Sallam and Soheir A. R. Naga

Polymers 2021, 13(18), 3129; https://doi.org/10.3390/polym13183129 - 16 Sep 2021

Cited by 27 | Viewed by 4103

Abstract

The main objective of this work is to predict the exact value of the fracture toughness (K_Q) of fiber-reinforced polymer (FRP). The drawback of the American Society for Testing Materials (ASTM) E1922 specimen is the lack of intact fibers behind [...] Read more.

The main objective of this work is to predict the exact value of the fracture toughness (K_Q) of fiber-reinforced polymer (FRP). The drawback of the American Society for Testing Materials (ASTM) E1922 specimen is the lack of intact fibers behind the crack-tip as in the real case, i.e., through-thickness cracked (TTC) specimen. The novelty of this research is to overcome this deficiency by suggesting unprecedented cracked specimens, i.e., matrix cracked (MC) specimens. This MC exists in the matrix (epoxy) without cutting the glass fibers behind the crack-tip in the unidirectional laminated composite. Two different cracked specimen geometries according to ASTM E1922 and ASTM D3039 were tested. 3-D FEA was adopted to predict the damage failure and geometry correction factor of cracked specimens. The results of the TTC ASTM E1922 specimen showed that the crack initiated perpendicular to the fiber direction up to 1 mm. Failure then occurred due to crack propagation parallel to the fiber direction, i.e., notch insensitivity. As expected, the K_Q of the MC ASTM D3039 specimen is higher than that of the TTC ASTM D3039 specimen. The K_Q of the MC specimen with two layers is about 1.3 times that of the MC specimen with one layer. Full article

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17 pages, 5337 KiB

Open AccessArticle

Mechanical Performance of Granite Fine Fly Dust-Filled Basalt/Glass Polyurethane Polymer Hybrid Composites

by Napisah Sapiai, Aidah Jumahat, Mohammad Jawaid, Md Zin Abu and Mochamad Chalid

Polymers 2021, 13(18), 3032; https://doi.org/10.3390/polym13183032 - 8 Sep 2021

Cited by 6 | Viewed by 2512

Abstract

The granite processing industry generates large amounts of bottom granite dust waste every day. After the drying and heating process of concrete mixture production, the granite dust is blown and collected in the filtering nozzle. This very fine particle granite dry fly dust, [...] Read more.

The granite processing industry generates large amounts of bottom granite dust waste every day. After the drying and heating process of concrete mixture production, the granite dust is blown and collected in the filtering nozzle. This very fine particle granite dry fly dust, with a particle size maximum distribution of 500 μm, can easily be blown away by wind and cause serious environmental impacts. The use of this waste material would be an effective way to reduce such impacts. Therefore, this paper presents an experimental study on the potential of granite dust as a filler in enhancing the mechanical performance of a hybrid basalt/glass (WB/GCSM) composite. The unhole and open hole tensile (UHT and OHT) properties, low velocity impact (LVI) properties, quasi-static indentations (QSI) properties, flexural properties, interlaminar shear stress (ILSS) properties, and morphology of the developed WB/GCSM composites were evaluated. To meet the objective of this study, composite specimens were produced using 1.5–60 μm granite fly dust at three (3) different loadings (1, 3 and 5 wt%). This granite fly dust was incorporated into polyurethane resin using a mechanical stirring technique. The production of FRP laminates then completed using a hand lay-up and vacuum bagging technique. Four types of the WB/GCSM composites systems, i.e., [WB/GCSM], [WB/GCSM/1GD], [WB/GCSM/3GD] and [WB/GCSM/5GD] were fabricated and compared. The analysis results for the mechanical tests revealed that the incorporation of granite dust of up to 3 wt% had increased the UHT, OHT, LVI, QSI, flexural and ILSS properties of all WB/GCSM composites systems. Higher levels of damage tolerance in UHT and OHT tests, and increased ductility index in the LVI test were obtained when granite dust was added up to 5 wt%. However, a remarkable improvement in all mechanical properties was noticed for [WB/GCSM/1GD], which recorded the highest mechanical performance among all WB/GCSM composite systems. Full article

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20 pages, 8433 KiB

Open AccessArticle

Poly (Lactic Acid)/Ground Tire Rubber Blends Using Peroxide Vulcanization

by Nicolas Candau, Oguzhan Oguz, Noel León Albiter, Gero Förster and Maria Lluïsa Maspoch

Polymers 2021, 13(9), 1496; https://doi.org/10.3390/polym13091496 - 6 May 2021

Cited by 14 | Viewed by 3363

Abstract

Poly (Lactic Acid) (PLA)/Ground Tire Rubber (GTR) blends using Dicumyl peroxide (DCP) as a crosslinking agent were prepared with the following aims: propose a new route to recycle wastes rubber from the automotive industry and improve the toughness and impact strength of the [...] Read more.

Poly (Lactic Acid) (PLA)/Ground Tire Rubber (GTR) blends using Dicumyl peroxide (DCP) as a crosslinking agent were prepared with the following aims: propose a new route to recycle wastes rubber from the automotive industry and improve the toughness and impact strength of the inherently brittle bio-based PLA. The GTR were subjected to two types of grinding process (cryo- and dry ambient grinding). Swelling measurements revealed the grinding to be associated with a mechanical damage of the rubber chains, independently on the type of grinding or on the GTR size (from <400 µm to <63 µm). Moreover, the finest GTR contains the largest amount of reinforcing elements (carbon black, clay) that can be advantageously used in PLA/GTR blends. Indeed, the use of the finest cryo-grinded GTR in the presence of DCP showed the least decrease of the tensile strength (−30%); maintenance of the tensile modulus and the largest improvement of the strain at break (+80%), energy at break (+60%) and impact strength (+90%) as compared to the neat PLA. The results were attributed to the good dispersion of both fine GTR and clay particles into the PLA matrix. Moreover, a possible re-crosslinking of the GTR particles and/or co-crosslinking at PLA/GTR interface in presence of DCP is expected to contribute to such improved ductility and impact strength. Full article

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14 pages, 12608 KiB

Open AccessArticle

Fabrication and Characterization of Chitosan/Cellulose Nanocrystal/Glycerol Bio-Composite Films

by Kusmono, Muhammad Waziz Wildan and Fadhlan Ihsan Lubis

Polymers 2021, 13(7), 1096; https://doi.org/10.3390/polym13071096 - 30 Mar 2021

Cited by 47 | Viewed by 4656

Abstract

Cellulose nanocrystal (CNC)-reinforced bio-composite films containing glycerol were produced using the solution casting technique. The influences of the addition of CNC (2, 4, and 8 wt%) and glycerol (10, 20, and 30 wt%) on the properties of the bio-composite films were studied in [...] Read more.

Cellulose nanocrystal (CNC)-reinforced bio-composite films containing glycerol were produced using the solution casting technique. The influences of the addition of CNC (2, 4, and 8 wt%) and glycerol (10, 20, and 30 wt%) on the properties of the bio-composite films were studied in the present work. The resulting films were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetry analysis (TGA), and according to their tensile, water absorption, and light transmission behavior. The introduction of 4 wt% CNC into the chitosan film did not affect the thermal stability, but the presence of 20 wt% glycerol reduced the thermal stability. The addition of 4 wt% CNC to the chitosan film increased its tensile strength, tensile modulus, and elongation at break by 206%, 138%, and 277%, respectively. However, adding more than 8 wt% CNC resulted in a drastic reduction in the strength and ductility of the chitosan film. The highest strength and stiffness of the chitosan bio-composite film were attained with 4 wt% CNC and 20 wt% glycerol. The water absorption and light transmission of the chitosan film were reduced dramatically by the presence of both CNC and glycerol. Full article

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16 pages, 3353 KiB

Open AccessArticle

Enhancement of Chloroprene/Natural/Butadiene Rubber Nanocomposite Properties Using Organoclays and Their Combination with Carbon Black as Fillers

by Patricia Castaño-Rivera, Isabel Calle-Holguín, Johanna Castaño, Gustavo Cabrera-Barjas, Karen Galvez-Garrido and Eduardo Troncoso-Ortega

Polymers 2021, 13(7), 1085; https://doi.org/10.3390/polym13071085 - 29 Mar 2021

Cited by 5 | Viewed by 4550

Abstract

Organoclay nanoparticles (Cloisite^® C10A, Cloisite^® C15) and their combination with carbon black (N330) were studied as fillers in chloroprene/natural/butadiene rubber blends to prepare nanocomposites. The effect of filler type and load on the physical mechanical properties of nanocomposites was determined and [...] Read more.

Organoclay nanoparticles (Cloisite^® C10A, Cloisite^® C15) and their combination with carbon black (N330) were studied as fillers in chloroprene/natural/butadiene rubber blends to prepare nanocomposites. The effect of filler type and load on the physical mechanical properties of nanocomposites was determined and correlated with its structure, compatibility and cure properties using Fourier Transformed Infrared (FT-IR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and rheometric analysis. Physical mechanical properties were improved by organoclays at 5–7 phr. Nanocomposites with organoclays exhibited a remarkable increase up to 46% in abrasion resistance. The improvement in properties was attributed to good organoclay dispersion in the rubber matrix and to the compatibility between them and the chloroprene rubber. Carbon black at a 40 phr load was not the optimal concentration to interact with organoclays. The present study confirmed that organoclays can be a reinforcing filler for high performance applications in rubber nanocomposites. Full article

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11 pages, 3172 KiB

Open AccessArticle

Toward Physicochemical and Rheological Characterization of Different Injectable Hyaluronic Acid Dermal Fillers Cross-Linked with Polyethylene Glycol Diglycidyl Ether

by Nicola Zerbinati, Sabrina Sommatis, Cristina Maccario, Maria Chiara Capillo, Giulia Grimaldi, Giuseppe Alonci, Marina Protasoni, Raffaele Rauso and Roberto Mocchi

Polymers 2021, 13(6), 948; https://doi.org/10.3390/polym13060948 - 19 Mar 2021

Cited by 22 | Viewed by 5424

Abstract

(1) Background: Injectable hyaluronic acid (HA) dermal fillers are used to restore volume, hydration and skin tone in aesthetic medicine. HA fillers differ from each other due to their cross-linking technologies, with the aim to increase mechanical and biological activities. One of the [...] Read more.

(1) Background: Injectable hyaluronic acid (HA) dermal fillers are used to restore volume, hydration and skin tone in aesthetic medicine. HA fillers differ from each other due to their cross-linking technologies, with the aim to increase mechanical and biological activities. One of the most recent and promising cross-linkers is polyethylene glycol diglycidyl ether (PEGDE), used by the company Matex Lab S.p.A., (Brindisi, Italy) to create the HA dermal filler PEGDE family. Over the last few years, several studies have been performed to investigate the biocompatibility and biodegradability of these formulations, but little information is available regarding their matrix structure, rheological and physicochemical properties related to their cross-linking technologies, the HA content or the degree of cross-linking. (2) Methods: Seven different injectable HA hydrogels were subjected to optical microscopic examination, cohesivity evaluation and rheological characterization in order to investigate their behavior. (3) Results: The analyzed cross-linked dermal fillers showed a fibrous “spiderweb-like” matrix structure, with each medical device presenting different and peculiar rheological features. Except for HA non cross-linked hydrogel 18 mg/mL, all showed an elastic and cohesive profile. (4) Conclusions: The comparative analysis with other literature works makes a preliminary characterization of these injectable medical devices possible. Full article

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17 pages, 32937 KiB

Open AccessArticle

Effect of Low Hydroxyapatite Loading Fraction on the Mechanical and Tribological Characteristics of Poly(Methyl Methacrylate) Nanocomposites for Dentures

by Ahmed Fouly, Ahmed Mohamed Mahmoud Ibrahim, El-Sayed M. Sherif, Ahmed M.R. FathEl-Bab and A.H. Badran

Polymers 2021, 13(6), 857; https://doi.org/10.3390/polym13060857 - 11 Mar 2021

Cited by 34 | Viewed by 3289

Abstract

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA [...] Read more.

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young’s modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss. Full article

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17 pages, 5344 KiB

Open AccessArticle

Tribological, Mechanical and Thermal Properties of Fluorinated Ethylene Propylene Filled with Al-Cu-Cr Quasicrystals, Polytetrafluoroethylene, Synthetic Graphite and Carbon Black

by Leonid K. Olifirov, Andrey A. Stepashkin, Galal Sherif and Victor V. Tcherdyntsev

Polymers 2021, 13(5), 781; https://doi.org/10.3390/polym13050781 - 4 Mar 2021

Cited by 12 | Viewed by 3280

Abstract

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al₇₃Cu₁₁Cr₁₆ powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection [...] Read more.

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al₇₃Cu₁₁Cr₁₆ powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection molding. Thermal, mechanical, and tribological properties of the obtained composites were studied. It was found that composite containing 5 wt.% of Al₇₃Cu₁₁Cr₁₆ quasicrystals and 2 wt.% of nanosized polytetrafluoroethylene has 50 times better wear resistance and a 1.5 times lower coefficient of dry friction comparing with unfilled fluorinated ethylene propylene. Addition of 15 wt.% of synthetic graphite to the above mentioned composition allows to achieve an increase in thermal conductivity in 2.5 times comparing with unfilled fluorinated ethylene propylene, at that this composite kept excellent tribological properties. Full article

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10 pages, 2800 KiB

Open AccessArticle

Preparation, Properties, and Microbial Impact of Tungsten (VI) Oxide and Zinc (II) Oxide Nanoparticles Enriched Polyethylene Sebacate Nanocomposites

by Amr S. Ismail, Salah M. Tawfik, Amr H. Mady and Yong-Ill Lee

Polymers 2021, 13(5), 718; https://doi.org/10.3390/polym13050718 - 26 Feb 2021

Cited by 6 | Viewed by 2273

Abstract

Nanoparticles of tungsten oxide (WO₃) and zinc oxide (ZnO) enriched polyethylene sebacate (PES) nanocomposites were prepared through the coprecipitation process and condensation polymerization reaction. The obtained nano-sized particles of WO₃ and ZnO, PES, and nanocomposites (WO₃-PES NC and [...] Read more.

Nanoparticles of tungsten oxide (WO₃) and zinc oxide (ZnO) enriched polyethylene sebacate (PES) nanocomposites were prepared through the coprecipitation process and condensation polymerization reaction. The obtained nano-sized particles of WO₃ and ZnO, PES, and nanocomposites (WO₃-PES NC and ZnO-PES NC) were investigated. The average molecular weight of the cured PES was measured by employing the gel permeation chromatography (GPC) technique. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) spectra assured the formation of the polymeric nanocomposites.WO₃ and ZnO nanoparticles supposed a condensed porous spherical phase found implanted in the polymer structure, as detected by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. These nano-scale systems achieved an electrical activity based on the conductive nanoparticles embedded matrix as a result of the ion–ion interactions. The microbial influence of the nanocomposites was examined against pathogenic bacteria; Pseudomonas aeruginosa,Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, and Fungi; Aspergillus niger, and Candidaalbicans. Results exhibited that these nanocomposites have antimicrobial effects from moderate to slightly high on bacteria and high on fungi which was confirmed by a clear zone of inhibition. This study contributes to the design of reasonable composites to be under evaluation for their catalytic effect. Full article

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16 pages, 21632 KiB

Open AccessArticle

Utilization of Bracing Arms as Additional Reinforcement in Pultruded Glass Fiber-Reinforced Polymer Composite Cross-Arms: Creep Experimental and Numerical Analyses

by Muhammad Rizal Muhammad Asyraf, Mohamad Ridzwan Ishak, Salit Mohd Sapuan and Noorfaizal Yidris

Polymers 2021, 13(4), 620; https://doi.org/10.3390/polym13040620 - 19 Feb 2021

Cited by 44 | Viewed by 3735

Abstract

The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under [...] Read more.

The application of pultruded glass fiber-reinforced polymer composites (PGFRPCs) as a replacement for conventional wooden cross-arms in transmission towers is relatively new. Although numerous studies have conducted creep tests on coupon-scale PGFRPC cross-arms, none had performed creep analyses on full-scale PGFRPC cross-arms under actual working load conditions. Thus, this work proposed to study the influence of an additional bracing system on the creep responses of PGFRPC cross-arms in a 132 kV transmission tower. The creep behaviors and responses of the main members in current and braced PGFRPC cross-arm designs were compared and evaluated in a transmission tower under actual working conditions. These PGFRPC cross-arms were subjected to actual working loads mimicking the actual weight of electrical cables and insulators for a duration of 1000 h. The cross-arms were installed on a custom test rig in an open area to simulate the actual environment of tropical climate conditions. Further creep analysis was performed by using Findley and Burger models on the basis of experimental data to link instantaneous and extended (transient and viscoelastic) creep strains. The addition of braced arms to the structure reduced the total strain of a cross-arm’s main member beams and improved elastic and viscous moduli. The addition of bracing arms improved the structural integrity and stiffness of the cross-arm structure. The findings of this study suggested that the use of a bracing system in cross-arm structures could prolong the structures’ service life and subsequently reduce maintenance effort and cost for long-term applications in transmission towers. Full article

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7 pages, 189 KiB

Open AccessEditorial

Reinforced Polymer Composites

by Victor V. Tcherdyntsev

Polymers 2021, 13(4), 564; https://doi.org/10.3390/polym13040564 - 13 Feb 2021

Cited by 9 | Viewed by 2225

Abstract

The development of modern technology requires the elaboration of new materials with improved operational and technological properties [...] Full article

17 pages, 4621 KiB

Open AccessArticle

Hypergravity-Induced Accumulation: A New, Efficient, and Simple Strategy to Improve the Thermal Conductivity of Boron Nitride Filled Polymer Composites

by Kangkang Yu, Tao Yuan, Songdi Zhang and Chenlu Bao

Polymers 2021, 13(3), 459; https://doi.org/10.3390/polym13030459 - 31 Jan 2021

Cited by 9 | Viewed by 3935

Abstract

Thermal conductive polymer composites (filled type) consisting of thermal conductive fillers and a polymer matrix have been widely used in a range of areas. More than 10 strategies have been developed to improve the thermal conductivity of polymer composites. Here we report a [...] Read more.

Thermal conductive polymer composites (filled type) consisting of thermal conductive fillers and a polymer matrix have been widely used in a range of areas. More than 10 strategies have been developed to improve the thermal conductivity of polymer composites. Here we report a new “hypergravity accumulation” strategy. Raw material mixtures of boron nitride/silicone rubber composites were treated in hypergravity fields (800–20,000 g, relative gravity acceleration) before heat-curing. A series of comparison studies were made. It was found that hypergravity treatments could efficiently improve the microstructures and thermal conductivity of the composites. When the hypergravity was about 20,000 g (relative gravity acceleration), the obtained spherical boron nitride/silicone rubber composites had highly compacted microstructures and high and isotropic thermal conductivity. The highest thermal conductivity reached 4.0 W/mK. Thermal interface application study showed that the composites could help to decrease the temperature on a light-emitting diode (LED) chip by 5 °C. The mechanism of the improved microstructure increased thermal conductivity, and the high viscosity problem in the preparation of boron nitride/silicone rubber composites, and the advantages and disadvantages of the hypergravity accumulation strategy, were discussed. Overall, this work has provided a new, efficient, and simple strategy to improve the thermal conductivity of boron nitride/silicone rubber and other polymer composites (filled type). Full article

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22 pages, 8657 KiB

Open AccessArticle

Combination of Self-Healing Butyl Rubber and Natural Rubber Composites for Improving the Stability

by Kunakorn Chumnum, Ekwipoo Kalkornsurapranee, Jobish Johns, Karnda Sengloyluan and Yeampon Nakaramontri

Polymers 2021, 13(3), 443; https://doi.org/10.3390/polym13030443 - 30 Jan 2021

Cited by 16 | Viewed by 5265

Abstract

The self-healing composites were prepared from the combination of bromobutyl rubber (BIIR) and natural rubber (NR) blends filled with carbon nanotubes (CNT) and carbon black (CB). To reach the optimized self-healing propagation, the BIIR was modified with ionic liquid (IL) and butylimidazole (IM), [...] Read more.

The self-healing composites were prepared from the combination of bromobutyl rubber (BIIR) and natural rubber (NR) blends filled with carbon nanotubes (CNT) and carbon black (CB). To reach the optimized self-healing propagation, the BIIR was modified with ionic liquid (IL) and butylimidazole (IM), and blended with NR using the ratios of 70:30 and 80:20 BIIR:NR. Physical and chemical modifications were confirmed from the mixing torque and attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR). It was found that the BIIR/NR-CNT_CB with IL and IM effectively improved the cure properties with enhanced tensile properties relative to pure BIIR/NR blends. For the healed composites, BIIR/NR-CNT_CB-IM exhibited superior mechanical and electrical properties due to the existing ionic linkages in rubber matrix. For the abrasion resistances, puncture stress and electrical recyclability were examined to know the possibility of inner liner applications and Taber abrasion with dynamic mechanical properties were elucidated for tire tread applications. Based on the obtained T_g and Tan δ values, the composites are proposed for tire applications in the future with a simplified preparation procedure. Full article

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17 pages, 5453 KiB

Open AccessArticle

Effects of Nanoclay on Mechanical and Dynamic Mechanical Properties of Bamboo/Kenaf Reinforced Epoxy Hybrid Composites

by Siew Sand Chee, Mohammad Jawaid, Othman Y. Alothman and Hassan Fouad

Polymers 2021, 13(3), 395; https://doi.org/10.3390/polym13030395 - 27 Jan 2021

Cited by 56 | Viewed by 3527

Abstract

Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite [...] Read more.

Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite nanotube (HNT)) with high shear speed homogenizer followed by hand lay-up fabrication technique. The effect of adding nanoclay on the tensile, flexural, and impact properties of the hybrid nanocomposites were studied. Fractography of tensile-fractured sample of hybrid composites was studied by field emission scanning electron microscope. The dynamic mechanical analyzer was used to study the viscoelastic properties of the hybrid nanocomposites. BK/E-OMMT exhibit enhanced mechanical properties compared to the other hybrid nanocomposites, with tensile, flexural, and impact strength values of 55.82 MPa, 105 MPa, and 65.68 J/m, respectively. Statistical analysis and grouping information were performed by one-way ANOVA (analysis of variance) and Tukey method, and it corroborates that the mechanical properties of the nanoclay-filled hybrid nanocomposites are statistically significant. The storage modulus of the hybrid nanocomposites was improved by 98.4%, 41.5%, and 21.7% with the addition of OMMT, MMT, and HNT, respectively. Morphology of the tensile fracture BK/E-OMMT composites shows that lesser voids, microcracks and fibers pull out due to strong fiber–matrix adhesion compared to other hybrid composites. Hence, the OMMT-filled BK/E hybrid nanocomposites can be utilized for load-bearing structure applications, such as floor panels and seatbacks, whereby lightweight and high strength are the main requirements. Full article

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15 pages, 1783 KiB

Open AccessArticle

Dynamic Characteristics of Woven Flax/Epoxy Laminated Composite Plate

by Venkatachalam Gopalan, Vimalanand Suthenthiraveerappa, A. Raja Annamalai, Santhanakrishnan Manivannan, Vignesh Pragasam, Panidvelan Chinnaiyan, Giriraj Mannayee and Chun-Ping Jen

Polymers 2021, 13(2), 209; https://doi.org/10.3390/polym13020209 - 8 Jan 2021

Cited by 16 | Viewed by 2904

Abstract

Due to the growing environmental awareness, the development of sustainable green composites is in high demand in composite industries, mainly in the automotive, aircraft, construction and marine applications. This work was an attempt to experimentally and numerically investigate the dynamic characteristics of Woven [...] Read more.

Due to the growing environmental awareness, the development of sustainable green composites is in high demand in composite industries, mainly in the automotive, aircraft, construction and marine applications. This work was an attempt to experimentally and numerically investigate the dynamic characteristics of Woven Flax/Bio epoxy laminated composite plates. In addition, the optimisation study on the dynamic behaviours of the Woven Flax/Bio epoxy composite plate is carried out using the response surface methodology (RSM) by consideration of the various parameters like ply orientation, boundary condition and aspect ratio. The elastic constants of the Woven Flax/Bio epoxy composite lamina needed for the numerical simulation are determined experimentally using two methods, i.e., the usual mechanical tests as well as through the impulse excitation of vibration-based approach and made a comparison between them. The numerical analysis on the free vibration characteristics of the composite was carried out using ANSYS, a finite element analysis (FEA) software. The confirmation of the FE model was accomplished by comparing the numerical results with its experimental counterpart. Finally, a comparison was made between the results obtained through the regression equation and finite element analysis. Full article

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17 pages, 8934 KiB

Open AccessArticle

Enhanced Thermal Conductivity of Epoxy Composites Filled with Al₂O₃/Boron Nitride Hybrids for Underfill Encapsulation Materials

by William Anderson Lee Sanchez, Chen-Yang Huang, Jian-Xun Chen, Yu-Chian Soong, Ying-Nan Chan, Kuo-Chan Chiou, Tzong-Ming Lee, Chih-Chia Cheng and Chih-Wei Chiu

Polymers 2021, 13(1), 147; https://doi.org/10.3390/polym13010147 - 1 Jan 2021

Cited by 53 | Viewed by 7874

Abstract

In this study, a thermal conductivity of 0.22 W·m⁻¹·K⁻¹ was obtained for pristine epoxy (EP), and the impact of a hybrid filler composed of two-dimensional (2D) flake-like boron nitride (BN) and zero-dimensional (0D) spherical micro-sized aluminum oxide (Al₂O [...] Read more.

In this study, a thermal conductivity of 0.22 W·m⁻¹·K⁻¹ was obtained for pristine epoxy (EP), and the impact of a hybrid filler composed of two-dimensional (2D) flake-like boron nitride (BN) and zero-dimensional (0D) spherical micro-sized aluminum oxide (Al₂O₃) on the thermal conductivity of epoxy resin was investigated. With 80 wt.% hybrid Al₂O₃–BN filler contents, the thermal conductivity of the EP composite reached 1.72 W·m⁻¹·K⁻¹, increasing approximately 7.8-fold with respect to the pure epoxy matrix. Furthermore, different important properties for the application were analyzed, such as Fourier-transform infrared (FTIR) spectra, viscosity, morphology, coefficient of thermal expansion (CTE), glass transition temperature (T_g), decomposition temperature (T_d), dielectric properties, and thermal infrared images. The obtained thermal performance is suitable for specific electronic applications such as flip-chip underfill packaging. Full article

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12 pages, 529 KiB

Open AccessArticle

Influence of Mechanical Couplings on the Dynamical Behavior and Energy Harvesting of a Composite Structure

by Marek Borowiec, Jaroslaw Gawryluk and Marcin Bochenski

Polymers 2021, 13(1), 66; https://doi.org/10.3390/polym13010066 - 26 Dec 2020

Cited by 5 | Viewed by 2493

Abstract

In this paper, the dynamical behavior of composite material is analyzed, including the energy harvesting effect. The composite is modeled by the Finite Element Method (FEM) and is made of pre-impregnate with a matrix of thermosetting epoxy resin reinforced with high-strength R-type glass [...] Read more.

In this paper, the dynamical behavior of composite material is analyzed, including the energy harvesting effect. The composite is modeled by the Finite Element Method (FEM) and is made of pre-impregnate with a matrix of thermosetting epoxy resin reinforced with high-strength R-type glass fibers, and it is designed as a beam structure that is exposed to mechanical vibrations. The structure assumed the form of a beam with a substantially rectangular cross section. The couplings of motion occurring between mode shapes at properly selected fiber orientations are investigated. The beams with determined sets of composite layers and a coupling effect are used to recover electricity from the mechanical vibrations in the vicinity of the first resonance zone. The composite with a certain number of fiber glass layers has assumed an orientation relative to the beam axis. The new values found in this paper are the intensity of the coupling between the bending in the stiff and flexible directions of the beam for a chosen fiber layer stacking sequence. Additionally, the influence of layer configuration on the energy harvesting efficiency of the Macro-Fiber Composite (MFC) piezoelectric element is assessed. Full article

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8 pages, 2144 KiB

Open AccessArticle

Two-Dimensional Piezoresistive Response and Measurement of Sensitivity Factor of Polymer-Matrix Carbon Fiber Mat

by Min Wu, Li Huang, Xiaoyu Zhang, Jianzhong Chen and Yong Lv

Polymers 2020, 12(12), 3072; https://doi.org/10.3390/polym12123072 - 21 Dec 2020

Cited by 1 | Viewed by 2218

Abstract

Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied [...] Read more.

Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied by a two-times uniaxial tension loading method in different directions, which was pasted in the center area of a cruciform aluminum substrate. The relations between the resistance change rate and the orthogonal strains were established, the reasonability of which was confirmed by comparison with the experimental results. The results show that the longitudinal piezoresistive sensitivity factor C₁₁ is 21.55, and the lateral piezoresistive sensitivity factor C₁₂ is 24.15. Using these factors, the resistance change rate of another polymer-matrix carbon mat was predicted, which was made by the same technique, and the error between the predicted and the experimental results was 1.3% in the longitudinal direction and 6.1% in the lateral direction. Full article

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15 pages, 4698 KiB

Open AccessArticle

A Preliminary Study of the Influence of Graphene Nanoplatelet Specific Surface Area on the Interlaminar Fracture Properties of Carbon Fiber/Epoxy Composites

by Konstantina Zafeiropoulou, Christina Kostagiannakopoulou, George Sotiriadis and Vassilis Kostopoulos

Polymers 2020, 12(12), 3060; https://doi.org/10.3390/polym12123060 - 21 Dec 2020

Cited by 10 | Viewed by 2650

Abstract

Graphene nanoplatelets (GNPs) are of particular interest to the field of nano-reinforced composites since they possess superior mechanical, fracture, thermal, and barrier properties. Due to their geometrical characteristics, high aspect ratio (AR)/specific surface area (SSA) and their planar structure, GNPs are considered as [...] Read more.

Graphene nanoplatelets (GNPs) are of particular interest to the field of nano-reinforced composites since they possess superior mechanical, fracture, thermal, and barrier properties. Due to their geometrical characteristics, high aspect ratio (AR)/specific surface area (SSA) and their planar structure, GNPs are considered as high-potential nanosized fillers for improving performance of composites. The present study investigates the effect of SSA of GNPs on fracture properties of carbon fiber reinforced polymers (CFRPs). For this reason, two nano-doped CFRPs were produced by using two types of GNPs (C300 and C500) with different SSAs, 300 and 500 m²/g, respectively. Both types of GNPs, at the same content of 0.5 wt%, were added into the epoxy matrix of composites by applying a three-roll milling technique. The nanomodified matrix was used for the manufacturing of prepregs, while the final composite laminates were fabricated through the vacuum-bag method. Mode I and II interlaminar fracture tests were carried out to determine the interlaminar fracture toughness G_IC and G_IIC of the composites, respectively. According to the results, the toughening effect of C500 GNPs was the strongest, resulting in increases of 25% in G_IC and 33% in G_IIC compared with the corresponding unmodified composites. The activation of the absorption mechanisms of C500 contributed to this outcome, which was confirmed by the scanning electron microscopy (SEM) analyses conducted in the fracture surfaces of specimens. On the other hand, C300 GNPs, due to disability to be dispersed uniformly into the epoxy matrix, did not influence the fracture properties of CFRPs, indicating that probably there is a threshold in SSA which is necessary to achieve for improving the fracture properties of CFRPs. Full article

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14 pages, 5699 KiB

Open AccessArticle

Rheological and Mechanical Properties of Silica/Nitrile Butadiene Rubber Vulcanizates with Eco-Friendly Ionic Liquid

by Munir Hussain, Sohail Yasin, Hafeezullah Memon, Zhiyun Li, Xinpeng Fan, Muhammad Adnan Akram, Wanjie Wang, Yihu Song and Qiang Zheng

Polymers 2020, 12(11), 2763; https://doi.org/10.3390/polym12112763 - 23 Nov 2020

Cited by 26 | Viewed by 4879

Abstract

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to [...] Read more.

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to formulate the nanocomposites. The impact of [EMIM]OAc on silica dispersion in a nitrile rubber (NBR) matrix was investigated by a transmission electron microscope and scanning electron microscopy. The combined use of the ionic liquid and silane in an NBR/silica system facilitates the homogeneous dispersion of the silica volume fraction (φ) from 0.041 to 0.177 and enhances crosslinking density of the matrix up to three-fold in comparison with neat NBR, and also it is beneficial for solving the risks of alcohol emission and ignition during the rubber manufacturing. The introduction of ionic liquid greatly improves the mechanical strength (9.7 MPa) with respect to neat NBR vulcanizate, especially at high temperatures e.g., 100 °C. Furthermore, it impacts on rheological behaviors of the nanocomposites and tends to reduce energy dissipation for the vulcanizates under large amplitude dynamic shear deformation. Full article

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17 pages, 6624 KiB

Open AccessArticle

Numerical Analysis of the Contact Behavior of a Polymer-Based Waterproof Membrane for Tunnel Lining

by Kicheol Lee, Dongwook Kim, Soon-Wook Choi, Soo-Ho Chang, Tae-Ho Kang and Chulho Lee

Polymers 2020, 12(11), 2704; https://doi.org/10.3390/polym12112704 - 16 Nov 2020

Cited by 8 | Viewed by 3223

Abstract

Waterproof membranes have higher initial strength, faster construction, and better waterproofing than conventional sheet membranes. In addition, their polymer constituents have much higher interfacial adhesion and tensile strength than those of conventional materials. However, despite their advantages, waterproof membranes are not widely used [...] Read more.

Waterproof membranes have higher initial strength, faster construction, and better waterproofing than conventional sheet membranes. In addition, their polymer constituents have much higher interfacial adhesion and tensile strength than those of conventional materials. However, despite their advantages, waterproof membranes are not widely used in civil construction. This study evaluates the material properties and interface parameters of a waterproof membrane by considering the results of laboratory experiments and numerical analysis. Since the contact behavior of a membrane at its interface with shotcrete is important for understanding the mechanism of the support it offers known as a shotcrete tunnel lining, modeling should adopt appropriate contact conditions. The numerical analysis identifies the suitability and contact conditions of the waterproof membrane in various conditions. Full article

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15 pages, 7041 KiB

Open AccessArticle

Low-Temperature Carbonized Elastomer-Based Composites Filled with Silicon Carbide

by Andrey A. Stepashkin, Semen D. Ignatyev, Dilyus I. Chukov, Victor V. Tcherdyntsev, Sergey D. Kaloshkin and Elena V. Medvedeva

Polymers 2020, 12(11), 2669; https://doi.org/10.3390/polym12112669 - 12 Nov 2020

Cited by 2 | Viewed by 4073

Abstract

Thermally stable composites obtained by the low-temperature carbonization of an elastomeric matrix filled with hard dispersed silicon carbide particles were obtained and investigated. Evolution of the microstructure and of mechanical and thermal characteristics of composites during thermal degradation and carbonization processes in a [...] Read more.

Thermally stable composites obtained by the low-temperature carbonization of an elastomeric matrix filled with hard dispersed silicon carbide particles were obtained and investigated. Evolution of the microstructure and of mechanical and thermal characteristics of composites during thermal degradation and carbonization processes in a wide range of filling from 0 to 450 parts per hundred rubber was studied. For highly filled composites, the compressive strength values were found to be more than 200 MPa; Young’s modulus was more than 15 GPa. The thermal conductivity coefficient of composites was up to 1.6 W/(m·K), and this magnitude varied slightly in the temperature range of 25–300 °C. Coupled with the high thermal stability of the composites, the observed properties make it possible to consider using such composites as strained friction units instead of reinforced polymers. Full article

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16 pages, 6027 KiB

Open AccessArticle

Analysis of Viscoelastic Behavior of Polypropylene/Carbon Nanotube Nanocomposites by Instrumented Indentation

by Felicia Stan, Adriana-Madalina Turcanu (Constantinescu) and Catalin Fetecau

Polymers 2020, 12(11), 2535; https://doi.org/10.3390/polym12112535 - 29 Oct 2020

Cited by 8 | Viewed by 2796

Abstract

In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). [...] Read more.

In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). Next, the Maxwell–Voigt–Kelvin model coupled with two-cycle indentation tests was used to predict the shear creep compliance function and the equivalent indentation modulus. The indentation hardness and elastic modulus of the PP/MWCNT nanocomposites extracted based on the Oliver and Pharr method were compared with the equivalent indentation modulus predicted based on the Maxwell–Voigt–Kelvin mode. The experimental results indicated that the addition of nanotubes into the polypropylene has a positive effect on the micro-mechanical properties of PP/MWCNT nanocomposites. Indentation hardness and elastic modulus increased significantly with increasing MWCNT loading. The creep resistance at the micro-scale of the PP/MWCNT nanocomposites improved with the addition of MWCNTs, with creep displacement reduced by up to 20% by increasing the carbon nanotube loading from 1 to 5 wt %. The Maxwell–Voigt–Kelvin model with three and five Voigt–Kelvin units accurately predicted the shear creep function and its change with increasing MWCNT loading. However, the equivalent indentation modulus was found to be sensitive to the number of Voigt–Kelvin units: the more Voigt–Kelvin units, the better the model predicts the equivalent indentation modulus. Full article

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13 pages, 5635 KiB

Open AccessArticle

A Branched Polyelectrolyte Complex Enables Efficient Flame Retardant and Excellent Robustness for Wood/Polymer Composites

by Yanping Huang, Shuai Zhang, He Chen, Chunxiang Ding, Yan Xuan, Mingzhu Pan and Changtong Mei

Polymers 2020, 12(11), 2438; https://doi.org/10.3390/polym12112438 - 22 Oct 2020

Cited by 13 | Viewed by 2664

Abstract

Wood/thermoplastic composites (WPCs) have been restricted in some fields of building construction and electrical equipment because of their inherent high flammability and lower toughness. In this work, a branched crosslinking network polyelectrolyte complex (PEC) has been designed by incorporation of polyethyleneimine (PEI), a [...] Read more.

Wood/thermoplastic composites (WPCs) have been restricted in some fields of building construction and electrical equipment because of their inherent high flammability and lower toughness. In this work, a branched crosslinking network polyelectrolyte complex (PEC) has been designed by incorporation of polyethyleneimine (PEI), a cation polyelectrolyte end capped amine groups, into cellulose nanocrystals (CNC), and ammonium polyphosphate (APP) via self-assembling. The hydrogen bonding interactions, penetration, and mechanical interlock provided by PEC effectively enhance the interfacial bonding within matrix, wood fibers, and flame retardant. Interestingly, it generates abundant micropores on the inner structure of WPC. The excellent interfacial bonding performance and easy-to-move molecular chain successfully transfer the stress and induce energy dissipation, simultaneously giving rise to higher strength and toughness for WPC. As well as the PEC endows WPC with a promotion in both smoke suppression and UL-94 V-0 rate. Additionally, the peak heat release rate and total smoke release for WPC obviously reduce by 36.9% and 50.0% respectively in presence of 25% PEC. A simple, eco-friendly, and concise strategy exhibits prospects for fiber-reinforced polymer composites with effective flame retardancy and mechanical robust properties. Full article

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48 pages, 4163 KiB

Open AccessReview

Mechanical Joining of Fibre Reinforced Polymer Composites to Metals—A Review. Part I: Bolted Joining

by Anna Galińska

Polymers 2020, 12(10), 2252; https://doi.org/10.3390/polym12102252 - 30 Sep 2020

Cited by 83 | Viewed by 12920

Abstract

As the fibre reinforced plastic composites gain larger and larger share in industry, the problem of joining them with metal elements becomes significant. The current paper is the first part of the literature review, which gathers and evaluates knowledge about methods suitable for [...] Read more.

As the fibre reinforced plastic composites gain larger and larger share in industry, the problem of joining them with metal elements becomes significant. The current paper is the first part of the literature review, which gathers and evaluates knowledge about methods suitable for mechanical joining of composite and metal elements. This paper concerns bolted joining, because this method of mechanical joining is widely used for joining composite materials. The paper describes failure modes of bolted joints in composite materials, the influence of the bolt clamping torque, the clearance between the bolt and the hole and aging on the performance of the joint, drilling techniques used in composite materials in order to minimize damages, different fastener types, inspection techniques, and finally, the techniques that have been developed in order to improve the strength of the bolted joints in composites. Since the hole drilled in a composite material in order to perform bolted joining is a weak point of the structure, those techniques: bonded inserts, titanium foil internal inserts, fibre steering, additional reinforcement, and moulded holes, mainly aim to improve the strength of the hole in the composite. The techniques have been discussed in details and compared with each other in the summary section. Full article

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13 pages, 6130 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Behavior of 3D Braided Composites Containing an Open-Hole

by Shuangqiang Liang, Qihong Zhou, Haiyang Mei, Ge Chen and Frank Ko

Polymers 2020, 12(9), 2147; https://doi.org/10.3390/polym12092147 - 21 Sep 2020

Cited by 4 | Viewed by 3243

Abstract

The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the [...] Read more.

The static and dynamic mechanical performances of notched and un-notched 3D braided composites were studied. The effect of longitudinal laid-in yarn was investigated in comparison with low braiding angle composites. The specimens were fatigue tested for up to millions of cycles, and the residual strength of the samples that survived millions of cycles was tested. The cross-section of the 3D braided specimens was observed after fatigue loading. It was found that the static and fatigue properties of low angle 3D braided behaved better than longitudinally reinforced 3D braided composites. For failure behavior, pure braids contain damage better and show less damage area than the braids with longitudinal yarns under fatigue loading. More cracks occurred in the 3D braided specimen with axial yarn cross-section along the longitudinal and transverse direction. Full article

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22 pages, 3111 KiB

Open AccessArticle

End-of-Life Recycling Options of (Nano)Enhanced CFRP Composite Prototypes Waste—A Life Cycle Perspective

by Fotini Petrakli, Anastasia Gkika, Alexandra Bonou, Panagiotis Karayannis, Elias P. Koumoulos, Dionisis Semitekolos, Aikaterini-Flora Trompeta, Nuno Rocha, Raquel M. Santos, Guy Simmonds, Glen Monaghan, Giorgio Valota, Guan Gong and Costas A. Charitidis

Polymers 2020, 12(9), 2129; https://doi.org/10.3390/polym12092129 - 18 Sep 2020

Cited by 26 | Viewed by 7186

Abstract

Life cycle assessment is a methodology to assess environmental impacts associated with a product or system/process by accounting resource requirements and emissions over its life cycle. The life cycle consists of four stages: material production, manufacturing, use, and end-of-life. This study highlights the [...] Read more.

Life cycle assessment is a methodology to assess environmental impacts associated with a product or system/process by accounting resource requirements and emissions over its life cycle. The life cycle consists of four stages: material production, manufacturing, use, and end-of-life. This study highlights the need to conduct life cycle assessment (LCA) early in the new product development process, as a means to assess and evaluate the environmental impacts of (nano)enhanced carbon fibre-reinforced polymer (CFRP) prototypes over their entire life cycle. These prototypes, namely SleekFast sailing boat and handbrake lever, were manufactured by functionalized carbon fibre fabric and modified epoxy resin with multi-walled carbon nanotubes (MWCNTs). The environmental impacts of both have been assessed via LCA with a functional unit of ‘1 product piece’. Climate change has been selected as the key impact indicator for hotspot identification (kg CO₂ eq). Significant focus has been given to the end-of-life phase by assessing different recycling scenarios. In addition, the respective life cycle inventories (LCIs) are provided, enabling the identification of resource hot spots and quantifying the environmental benefits of end-of-life options. Full article

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15 pages, 3764 KiB

Open AccessArticle

Leather Waste to Enhance Mechanical Performance of High-Density Polyethylene

by Eylem Kiliç, Quim Tarrés, Marc Delgado-Aguilar, Xavier Espinach, Pere Fullana-i-Palmer and Rita Puig

Polymers 2020, 12(9), 2016; https://doi.org/10.3390/polym12092016 - 3 Sep 2020

Cited by 19 | Viewed by 5005

Abstract

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as [...] Read more.

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as filler for a high density polyethylene matrix (HDPE). A series of HDPE-BF composites, containing filler concentrations ranging from 20 to 50wt%, were formulated, injection molded and tested. The effect of filler contents on the mechanical properties of the composites were evaluated and discussed. Composites with BF contents up to 30wt% improved the tensile strength and Young’s modulus of the matrix, achieving similar mechanical properties to polypropylene (PP). In the case of flexural strength, it was found to be proportionally enhanced by increasing reinforcement content, maintaining high impact strength. These composites present great opportunities for PP application areas that require higher impact resistance. The materials were submitted to a series of closed-loop recycling cycles in order to assess their recyclability, being able to maintain better tensile strength than virgin HDPE after 5 cycles. The study develops new low-cost and sustainable composites by using a waste as composite filler. Full article

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16 pages, 3710 KiB

Open AccessArticle

Viscoelastic Behavior of Glass-Fiber-Reinforced Silicone Composites Exposed to Cyclic Loading

by Julia Beter, Bernd Schrittesser, Bernhard Lechner, Mohammad Reza Mansouri, Claudia Marano, Peter Filipp Fuchs and Gerald Pinter

Polymers 2020, 12(9), 1862; https://doi.org/10.3390/polym12091862 - 19 Aug 2020

Cited by 21 | Viewed by 4411

Abstract

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure–property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass [...] Read more.

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure–property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass fibers were chosen as the reinforcement, along with silicone as the matrix material. For the characterization of the flexible composites, a novel testing device was developed. Apart from the conventional dynamic mechanical analysis, in which the effect of the fiber orientation was also considered, modified step cycle tests were conducted under tensile loading. The material viscoelastic behavior was studied, evaluating both the stress relaxation response and the capability of the material to dissipate energy under straining. The effects of the displacement rate of the strain level, the amplitude of the strain applied in the loading–unloading step cycle test, and the number of the applied cycles were evaluated. The results revealed that an optimized fiber orientation leads to 30-fold enhanced stiffness, along with 10 times higher bearable stress. The findings demonstrated that tailored reinforced elastomers with endless fibers have a strong influence on the mechanical performance, affecting the structural properties significantly. Full article

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13 pages, 10076 KiB

Open AccessArticle

Analysis of Three-Phase Structure of Epoxy Resin/CNT/Graphene by Molecular Simulation

by Shun Naito, Jun Koyanagi, Takuji Komukai and Toshikazu Uno

Polymers 2020, 12(8), 1821; https://doi.org/10.3390/polym12081821 - 13 Aug 2020

Cited by 3 | Viewed by 3440

Abstract

In this study, the three-phase structure consisting of epoxy resin, carbon nanotubes (CNTs), and graphene, which is assumed to be the surface of carbon fiber, was simulated using molecular dynamics. Models in which the CNT number and initial position of CNT are varied [...] Read more.

In this study, the three-phase structure consisting of epoxy resin, carbon nanotubes (CNTs), and graphene, which is assumed to be the surface of carbon fiber, was simulated using molecular dynamics. Models in which the CNT number and initial position of CNT are varied were prepared in this study. Relaxation calculation for each three-phase model was implemented, and the movement of molecules was investigated. When CNTs are located between the graphene and epoxy at initial, how the epoxy approaches to graphene was discussed. Besides, interaction energies between CNT/graphene, CNT/epoxy, and graphene/epoxy were evaluated after relaxations. The value of the interaction energy between two individual molecules (epoxy resin and graphene, CNTs and graphene, epoxy resin and CNTs) among three-phase structure were obtained, respectively, and those mechanisms were discussed in this study. Full article

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13 pages, 5480 KiB

Open AccessArticle

Tribo-Mechanical Characterization of Carbon Fiber-Reinforced Cyanate Ester Resins Modified With Fillers

by Ankur Bajpai, Prateek Saxena and Klaus Kunze

Polymers 2020, 12(8), 1725; https://doi.org/10.3390/polym12081725 - 31 Jul 2020

Cited by 22 | Viewed by 4432

Abstract

High-performance polymer composites are being increasingly favored for structural applications. For this purpose, efforts are being focused on exploring the potential of high-performance thermoplastics and thermosets. Cyanate ester (CE) resin is a special thermoset that can be used at up to 400 °C [...] Read more.

High-performance polymer composites are being increasingly favored for structural applications. For this purpose, efforts are being focused on exploring the potential of high-performance thermoplastics and thermosets. Cyanate ester (CE) resin is a special thermoset that can be used at up to 400 °C without any considerable degradation; however, its tribological properties are not at the adequate level. Hence, it is needed to use this polymer in composite form with the fibrous/particulate reinforcement to impart better tribological properties and mechanical strength via a strong fiber–matrix interface. Carbon fiber/fabrics are at the forefront as reinforcement for specialty polymers. The tribological and tensile properties of cyanate ester (CE) composites-filled graphite, polytetrafluoroethylene (PTFE), and MoS₂ micron-sized fillers reinforced with carbon fibers (CF) are investigated experimentally in a block-on-ring setup at 100 N, for 10 h, and with a sliding distance of approximately 10,000 m, against a hardened polished 100Cr6 steel shaft and diamond-like-coated (DLC) 100Cr6 steel shaft. The tribological properties of the composites including the coefficient of friction and specific wear rate are enhanced especially with the incorporation of graphite fillers. The friction coefficient and wear rate of the graphite-based composite was decreased significantly at 5 wt.% of graphite concentration. Further, at the same concentration, the graphite-based composite showed superior tensile properties as compared to the reference system owing to better dispersion and adhesion between the fibers and matrix. Tensile tests are performed to characterize the fiber–matrix interfacial adhesion and other strength properties. Full article

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40 pages, 8757 KiB

Open AccessReview

Mechanical Joining of Fibre Reinforced Polymer Composites to Metals—A Review. Part II: Riveting, Clinching, Non-Adhesive Form-Locked Joints, Pin and Loop Joining

by Anna Galińska and Cezary Galiński

Polymers 2020, 12(8), 1681; https://doi.org/10.3390/polym12081681 - 28 Jul 2020

Cited by 72 | Viewed by 12273

Abstract

As fiber reinforced plastic composites gain an increasingly larger share in aerospace structures, the problem of joining them with metal elements becomes significant. The current paper is the second part of the literature review, which gathers and evaluates knowledge about methods suitable for [...] Read more.

As fiber reinforced plastic composites gain an increasingly larger share in aerospace structures, the problem of joining them with metal elements becomes significant. The current paper is the second part of the literature review, which gathers and evaluates knowledge about methods suitable for the mechanical joining of composite and metal elements. This paper reviews the joining methods other than bolted joining, which are discussed in the first part of the review, namely self-piercing riveting, friction riveting, clinching, non-adhesive form-locked joints, pin joints, and loop joints. Some of those methods are full-fledged and employed in commercial applications, whereas others are merely ideas tested at the level of specimens. The current review describes the ideas and the qualities of the joining methods as well as the experimental work carried out so far. The summary section of this paper contains a comparison of those methods with the reference to their qualities, which is important from the point of view of a composite structure designer: possibility of the joint disassembly, damages induced in composite, complication level, weight penalty, range of possible materials to be joined, and the joint strength. Full article

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24 pages, 2557 KiB

Open AccessReview

Strength Degradation in Curved Fiber-reinforced Polymer (FRP) Bars Used as Concrete Reinforcement

by Thanongsak Imjai, Reyes Garcia, Maurizio Guadagnini and Kypros Pilakoutas

Polymers 2020, 12(8), 1653; https://doi.org/10.3390/polym12081653 - 24 Jul 2020

Cited by 27 | Viewed by 7040

Abstract

Steel reinforcements in concrete tend to corrode and this process can lead to structural damage. Fiber-reinforced polymer (FRP) reinforcements represent a viable alternative for structures exposed to aggressive environments and have many possible applications where superior corrosion resistance properties are required. The use [...] Read more.

Steel reinforcements in concrete tend to corrode and this process can lead to structural damage. Fiber-reinforced polymer (FRP) reinforcements represent a viable alternative for structures exposed to aggressive environments and have many possible applications where superior corrosion resistance properties are required. The use of FRP rebars as internal reinforcements for concrete, however, is limited to specific structural elements and does not yet extend to the whole structure. The reason for this relates to the limited availability of curved or shaped reinforcing FRP elements on the market, as well as their reduced structural performance. This article presents a state-of-the art review on the strength degradation of curved FRP composites, and also assesses the performance of existing predictive models for the bend capacity of FRP reinforcements. Previous research has shown that the mechanical performance of bent portions of FRP bars significantly reduces under a multiaxial combination of stresses. Indeed, the tensile strength of bent FRP bars can be as low as 25% of the maximum tensile strength developed in a straight counterpart. In a significant number of cases, the current design recommendations for concrete structures reinforced with FRP were found to overestimate the bend capacity of FRP bars. A more accurate and practical predictive model based on the Tsai–Hill failure criteria is also discussed. This review article also identifies potential challenges and future directions of research for exploring the use of curved/shaped FRP composites in civil engineering applications. Full article

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15 pages, 4980 KiB

Open AccessArticle

Experimental and Numerical Research on Open-Hole Strength and Damage Mechanism of Regularly Arrayed Short Fiber Reinforced Polymer Composite

by Junfeng Hu, Xutong Zhang, Zhou Chen, Wenkang Guo, Hang Li and Xi Deng

Polymers 2020, 12(7), 1622; https://doi.org/10.3390/polym12071622 - 21 Jul 2020

Cited by 10 | Viewed by 3209

Abstract

Laminates with unidirectionally arrayed chopped strands (UACS) are one of the advanced short fiber reinforced polymer composites (SFRP) with significant application prospect, which greatly improves mechanical properties compared to the traditional SFRP, meanwhile ensuring excellent flowability. In practice, composite laminate with an open [...] Read more.

Laminates with unidirectionally arrayed chopped strands (UACS) are one of the advanced short fiber reinforced polymer composites (SFRP) with significant application prospect, which greatly improves mechanical properties compared to the traditional SFRP, meanwhile ensuring excellent flowability. In practice, composite laminate with an open hole is one of the typical connective components, and it is necessary to clarify the allowable load and damage tolerance performance of notched structures. In the present study, UACS laminates were fabricated using the continuous carbon fiber reinforced polymer (CFRP) prepreg, on which regularly arrayed bi-angled slits were introduced by a commercial numerical control cutter. The tensile strength and strain distribution around the open hole of the notched UACS laminate were experimentally investigated, while the damage progression near the open hole of the notched UACS laminate was analyzed by the finite element method (FEM). The tensile strength of the notched UACS laminate was measured at 298 MPa, which is about 60% of the strength of the unnotched UACS laminate. The simulation results match well with the experimental results, although there is a little overestimate on strength, by about 5% and 7%, for unnotched and notched UACS laminates, respectively. The final critical failure mode for the notched UACS laminate is mainly dominated by the delamination instead of the fiber breakage in the unnotched UACS laminate. Full article

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20 pages, 5239 KiB

Open AccessArticle

Study of Compaction Properties and Permeability Prediction of Multilayered Quadriaxial Non-Crimp Fabric in Liquid Composite Molding Process

by Yi Geng, Jinhua Jiang, Fangbing Lin, Huiqi Shao, Chenglong Zhang and Nanliang Chen

Polymers 2020, 12(7), 1525; https://doi.org/10.3390/polym12071525 - 9 Jul 2020

Cited by 3 | Viewed by 3485

Abstract

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation [...] Read more.

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation mechanism was affected by the interaction with stitch yarns. Owing to the meso-channels in the fibrous structure and the nesting between layers, the in-plane permeability of quadriaxial NCF did not follow an inverse proportion relationship with the fiber volume fraction. To predict the in-plane permeability of multilayered quadriaxial NCFs, unit cell models at a high level of geometrical details were built, including local variations in yarn cross-sections and the nesting deformation between layers. Numerical methods were implemented, and the prediction results were in very good agreement with the experimental data. Besides, the major contributing parameters to the enhancement of the in-plane permeabilities were identified by investigating the correlation between permeability and structural parameters of quadriaxial NCF. The modeling methodology and the principles established can be applied to the design of the quadriaxial NCF fabrics, where the permeability enhancement was evidenced. Full article

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12 pages, 8333 KiB

Open AccessArticle

Preparation and Characterization of Furan–Matrix Composites Blended with Modified Hollow Glass Microsphere

by Yizhe Ma, Ying Du, Jin Zhao, Xubo Yuan and Xin Hou

Polymers 2020, 12(7), 1480; https://doi.org/10.3390/polym12071480 - 1 Jul 2020

Cited by 14 | Viewed by 3422

Abstract

In this study, a new class of thermal insulation composites was prepared by blending a modified hollow glass microsphere (HGM) with furan resin. The particle dispersion between the microparticles and resin matrix was improved using 3-methacryloxypropyltrimethoxy silane (KH-570). Furthermore, the structure and morphology [...] Read more.

In this study, a new class of thermal insulation composites was prepared by blending a modified hollow glass microsphere (HGM) with furan resin. The particle dispersion between the microparticles and resin matrix was improved using 3-methacryloxypropyltrimethoxy silane (KH-570). Furthermore, the structure and morphology of the modified HGM were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In addition, the effects of the modified HGM on the thermal insulation, flame retardancy, and thermal properties of the composites were investigated. The thermal conductivity of the composites was lower than that of the native furan resin. The minimum thermal conductivity of the composites was 0.0274 W/m·K; the flame retardancy of the composites improved, and the limiting oxygen index become a maximum of 31.6%, reaching the refractory material level. Furthermore, the thermal analysis of the composites demonstrated enhanced thermal stability. This study demonstrates that the composite material exhibited good thermal insulation performance and flame retardancy and that it can be applied in the field of thermal insulation. Full article

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14 pages, 9257 KiB

Open AccessArticle

Experimental Evaluation of Low Velocity Impact Properties and Damage Progression on Bamboo/Glass Hybrid Composites Subjected to Different Impact Energy Levels

by Ain Umaira Md Shah, Mohamed Thariq Hameed Sultan and Syafiqah Nur Azrie Safri

Polymers 2020, 12(6), 1288; https://doi.org/10.3390/polym12061288 - 4 Jun 2020

Cited by 15 | Viewed by 2983

Abstract

Six impact energy values, ranging from 2.5 J to 10 J, were applied to study the impact properties of neat epoxy and bamboo composites, while six impact energy values, ranging from 10 J to 35 J, were applied on bamboo/glass hybrid composites. Woven [...] Read more.

Six impact energy values, ranging from 2.5 J to 10 J, were applied to study the impact properties of neat epoxy and bamboo composites, while six impact energy values, ranging from 10 J to 35 J, were applied on bamboo/glass hybrid composites. Woven glass fibre was embedded at the outermost top and bottom layer of bamboo powder-filled epoxy composites, producing sandwich structured hybrid composites through lay-up and molding techniques. A drop weight impact test was performed to study the impact properties. A peak force analysis showed that neat epoxy has the stiffest projectile for targeting interaction, while inconsistent peak force data was collected for the non-hybrid composites. The non-hybrid composites could withstand up to 10 J, while the hybrid composites showed a total failure at 35 J. It can be concluded that increasing the filler loading lessened the severity of damages in non-hybrid composites, while introducing the woven glass fibre could slow down the penetration of the impactor, thus lowering the chances of a total failure of the composites. Full article

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13 pages, 1226 KiB

Open AccessReview

A Review on the Kenaf/Glass Hybrid Composites with Limitations on Mechanical and Low Velocity Impact Properties

by Seri Nur Zumaimi Ahmad Nadzri, Mohamed Thariq Hameed Sultan, Ain Umaira Md Shah, Syafiqah Nur Azrie Safri and Adi Azriff Basri

Polymers 2020, 12(6), 1285; https://doi.org/10.3390/polym12061285 - 4 Jun 2020

Cited by 29 | Viewed by 4542

Abstract

Environmental awareness and trends to develop sustainable resources have directed much research attention towards kenaf fibre as an alternative reinforcement in composite manufacturing. Numerous studies have been conducted on kenaf and its hybrid composites. Most studies were conducted on kenaf/glass hybrid composites compared [...] Read more.

Environmental awareness and trends to develop sustainable resources have directed much research attention towards kenaf fibre as an alternative reinforcement in composite manufacturing. Numerous studies have been conducted on kenaf and its hybrid composites. Most studies were conducted on kenaf/glass hybrid composites compared to other kenaf/synthetic hybrid composites. Similar with other materials, mechanical properties were the fundamental knowledge identified by the researcher. Limited studies conducted on other properties have restricted the use of kenaf composites to non-structural applications. To extend the potential of kenaf composites to automotive exterior or other critical applications, studies on impact properties can be a valuable contribution in the material field. This review discusses the mechanical and low velocity impact properties of kenaf/glass hybrid composites reported previously. Percentage loading of fibre, the angle of orientation in woven fibres and the chemical treatment applied to the fibre before compounding are the three major parameters that affect the mechanical and impact properties of the composites. This review provides insights into the mechanical and impact properties of kenaf/glass hybrid composites for future research. Full article

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10 pages, 1729 KiB

Open AccessArticle

Tensile Properties of Composite Reinforced with Three-Dimensional Printed Fibers

by Komal Agarwal, Rahul Sahay and Avinash Baji

Polymers 2020, 12(5), 1089; https://doi.org/10.3390/polym12051089 - 10 May 2020

Cited by 10 | Viewed by 4247

Abstract

This study used melt-electrospinning writing to fabricate three-dimensional fiber constructs by embedding them in a polyvinyl alcohol (PVA) matrix to obtain thin composite films. Fourier transform infrared spectroscopy (FTIR) and dynamic scanning calorimetry (DSC) were used to demonstrate an interaction between the polycaprolactone [...] Read more.

This study used melt-electrospinning writing to fabricate three-dimensional fiber constructs by embedding them in a polyvinyl alcohol (PVA) matrix to obtain thin composite films. Fourier transform infrared spectroscopy (FTIR) and dynamic scanning calorimetry (DSC) were used to demonstrate an interaction between the polycaprolactone (PCL) fibrous phase and the PVA matrix phase. Following this, the mechanical deformation behavior of the composite was investigated, and the effect of reinforcement with three-dimensional fibrous constructs was illustrated. The specific strength of the composite was found to be five times higher than the specific strength of the neat PVA matrix. Additionally, the specific toughness of the composite was determined to be roughly four times higher than the specific toughness determined for the neat PVA matrix. These results demonstrate the potential of using melt-electrospinning writing for producing three-dimensional fibrous constructs for composite reinforcement purposes. Full article

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14 pages, 7006 KiB

Open AccessArticle

The Effect of Modification on the Properties of Polyetherimide and Its Carbon-Filled Composite

by Azamat Slonov, Ismel Musov, Azamat Zhansitov, Elena Rzhevskaya, Diana Khakulova and Svetlana Khashirova

Polymers 2020, 12(5), 1056; https://doi.org/10.3390/polym12051056 - 4 May 2020

Cited by 11 | Viewed by 3624

Abstract

The effect of oligophenylene sulfone (OPSU) and polycarbonate (PC) on the rheological, mechanical and thermal properties of polyetherimide (PEI) and a carbon-filled composite based on it was studied. It is shown that the introduction of OPSU and PC leads to a decrease in [...] Read more.

The effect of oligophenylene sulfone (OPSU) and polycarbonate (PC) on the rheological, mechanical and thermal properties of polyetherimide (PEI) and a carbon-filled composite based on it was studied. It is shown that the introduction of OPSU and PC leads to a decrease in the melt viscosity of PEI and a carbon-filled composite based on it with the preservation of their mechanical properties and heat resistance at a sufficiently high level. It was found that composites with OPSU have higher mechanical and thermal properties compared with composites with PC. Samples from modified carbon-filled PEI were printed by the fused deposit modeling (FDM) method. Three-dimensionally printed samples from carbon-filled PEI modified by OPSU showed significantly higher mechanical properties than composites with PC. Full article

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10 pages, 3104 KiB

Open AccessArticle

Bi-Functional Composting the Sulfonic Acid Based Proton Exchange Membrane for High Temperature Fuel Cell Application

by Guoxiao Xu, Juan Zou, Zhu Guo, Jing Li, Liying Ma, Ying Li and Weiwei Cai

Polymers 2020, 12(5), 1000; https://doi.org/10.3390/polym12051000 - 26 Apr 2020

Cited by 8 | Viewed by 3129

Abstract

Although sulfonic acid (SA)-based proton-exchange membranes (PEMs) dominate fuel cell applications at low temperature, while sulfonation on polymers would strongly decay the mechanical stability limit the applicable at elevated temperatures due to the strong dependence of proton conduction of SA on water. For [...] Read more.

Although sulfonic acid (SA)-based proton-exchange membranes (PEMs) dominate fuel cell applications at low temperature, while sulfonation on polymers would strongly decay the mechanical stability limit the applicable at elevated temperatures due to the strong dependence of proton conduction of SA on water. For the purpose of bifunctionally improving mechanical property and high-temperature performance, Nafion membrane, which is a commercial SA-based PEM, is composited with fabricated silica nanofibers with a three-dimensional network structure via electrospinning by considering the excellent water retention capacity of silica. The proton conductivity of the silica nanofiber–Nafion composite membrane at 110 °C is therefore almost doubled compared with that of a pristine Nafion membrane, while the mechanical stability of the composite Nafion membrane is enhanced by 44%. As a result, the fuel cell performance of the silica nanofiber-Nafion composite membrane measured at high temperature and low humidity is improved by 38%. Full article

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13 pages, 4822 KiB

Open AccessArticle

Surface Modification of Staple Carbon Fiber by Dopamine to Reinforce Natural Latex Composite

by Xiaolong Tian, Shuang Han, Qianxiao Zhuang, Huiguang Bian, Shaoming Li, Changquan Zhang, Chuansheng Wang and Wenwen Han

Polymers 2020, 12(4), 988; https://doi.org/10.3390/polym12040988 - 24 Apr 2020

Cited by 23 | Viewed by 3971

Abstract

Carbon fiber significantly enhances the mechanical, thermal and electrical properties of rubber composites, which are widely used in aerospace, military, national defense and other cutting-edge fields. The preparation of a high-performance carbon fiber rubber composite has been a research hotspot, because the surface [...] Read more.

Carbon fiber significantly enhances the mechanical, thermal and electrical properties of rubber composites, which are widely used in aerospace, military, national defense and other cutting-edge fields. The preparation of a high-performance carbon fiber rubber composite has been a research hotspot, because the surface of carbon fiber is smooth, reactive inert and has a poor adhesion with rubber. In this paper, a high-performance rubber composite is prepared by mixing dopamine-modified staple carbon fiber with natural latex, and the mechanisms of modified carbon fiber-reinforced natural latex composite are explored. The experimental results show that the surface-modified staple carbon fiber forms uniform and widely covered polydopamine coatings, which significantly improve the interface adhesion between the carbon fiber and the rubber matrix. Meanwhile, when the concentration of dopamine is 1.5 g/L and the staple carbon fiber is modified for 6h, the carbon fiber rubber composite shows excellent conductivity, thermal conductivity, and dynamic mechanical properties, and its tensile strength is 10.6% higher than that of the unmodified sample. Full article

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12 pages, 4829 KiB

Open AccessArticle

Effect of Glass Fibers Thermal Treatment on the Mechanical and Thermal Behavior of Polysulfone Based Composites

by Galal Sherif, Dilyus I. Chukov, Victor V. Tcherdyntsev, Valerii G. Torokhov and Dmitry D. Zherebtsov

Polymers 2020, 12(4), 902; https://doi.org/10.3390/polym12040902 - 13 Apr 2020

Cited by 18 | Viewed by 4749

Abstract

The effect of thermal treatment of glass fibers (GF) on the mechanical and thermo-mechanical properties of polysulfone (PSU) based composites reinforced with GF was investigated. Flexural and shear tests were used to study the composites’ mechanical properties. A dynamic mechanical analysis (DMA) and [...] Read more.

The effect of thermal treatment of glass fibers (GF) on the mechanical and thermo-mechanical properties of polysulfone (PSU) based composites reinforced with GF was investigated. Flexural and shear tests were used to study the composites’ mechanical properties. A dynamic mechanical analysis (DMA) and a heat deflection temperature (HDT) test were used to study the thermo-mechanical properties of composites. The chemical structure of the composites was studied using IR-spectroscopy, and scanning electron microscopy (SEM) was used to illustrate the microstructure of the fracture surface. Three fiber to polymer ratios of initial and preheated GF composites (50/50, 60/40, 70/30 (wt.%)) were studied. The results showed that the mechanical and thermo-mechanical properties improved with an increase in the fiber to polymer ratio. The interfacial adhesion in the preheated composites enhanced as a result of removing the sizing coating during the thermal treatment of GF, which improved the properties of the preheated composites compared with the composites reinforced with initial untreated fibers. The SEM images showed a good distribution of the polymer on the GF surface in the preheated GF composites. Full article

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14 pages, 6568 KiB

Open AccessArticle

Synergistic Effect of Maleated Natural Rubber and Modified Palm Stearin as Dual Compatibilizers in Composites based on Natural Rubber and Halloysite Nanotubes

by Nabil Hayeemasae, Zareedan Sensem, Indra Surya, Kannika Sahakaro and Hanafi Ismail

Polymers 2020, 12(4), 766; https://doi.org/10.3390/polym12040766 - 1 Apr 2020

Cited by 22 | Viewed by 3389

Abstract

The performance of rubber composite relies on the compatibility between rubber and filler. This is specifically of concern when preparing composites with very different polarities of the rubber matrix and the filler. However, a suitable compatibilizer can mediate the interactions. In this study, [...] Read more.

The performance of rubber composite relies on the compatibility between rubber and filler. This is specifically of concern when preparing composites with very different polarities of the rubber matrix and the filler. However, a suitable compatibilizer can mediate the interactions. In this study, composites of natural rubber (NR) with halloysite nanotubes (HNT) were prepared with maleated natural rubber (MNR) and modified palm stearin (MPS) as dual compatibilizers. The MPS dose ranged within 0.5–1.5 phr, while the MNR dose was fixed at 10 phr in all formulations. It was found that the mixed MNR/MPS significantly enhanced modulus, tensile strength, and tear strength of the composites. The improvements were mainly due to improved rubber-HNT interactions arising from hydrogen bonds formed in the presence of these two compatibilizers. This was clearly verified by observing the Payne effect. Apart from that, the MPS also acted as a plasticizer to provide improved dispersion of HNT. It was clearly demonstrated that MNR and MPS as dual compatibilizers improved rubber-HNT interactions and reduced filler-filler interactions, which then improved tensile and tear strengths, as well as dynamical properties. Therefore, the mix of MNR and MPS had a great potential to compatibilize non-polar rubber with HNT filler. Full article

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27 pages, 8501 KiB

Open AccessReview

Fiber Reinforced Polymer Laminates for Strengthening of RC Slabs against Punching Shear: A Review

by Osama Ahmed Mohamed, Manish Kewalramani and Rania Khattab

Polymers 2020, 12(3), 685; https://doi.org/10.3390/polym12030685 - 19 Mar 2020

Cited by 23 | Viewed by 6044

Abstract

Reinforced concrete flat slabs or flat plates continue to be among the most popular floor systems due to speed of construction and inherent flexibility it offers in relation to locations of partitions. However, flat slab/plate floor systems that are deficient in two-way shear [...] Read more.

Reinforced concrete flat slabs or flat plates continue to be among the most popular floor systems due to speed of construction and inherent flexibility it offers in relation to locations of partitions. However, flat slab/plate floor systems that are deficient in two-way shear strength are susceptible to brittle failure at a slab–column junction that may propagate and lead to progressive collapse of a larger segment of the structural system. Deficiency in two-way shear strength may be due to design/construction errors, material under-strength, or overload. Fiber reinforced polymer (FRP) composite laminates in the form of sheets and/or strips are used in structurally deficient flat slab systems to enhance the two-way shear capacity, flexural strength, stiffness, and ductility. Glass FRP (GFRP) has been used successfully but carbon FRP (CFRP) sheets/strips/laminates are more commonly used as a practical alternative to other expensive and/or challenging methods such column enlargement. This article reviews the literature on the methodology and effectiveness of utilizing FRP sheets/strips and laminates at the column/slab intersection to enhance punching shear strength of flat slabs. Full article

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16 pages, 9452 KiB

Open AccessArticle

PEEK Composites as Self-Lubricating Bush Materials for Articulating Revolute Pin Joints

by Juanjuan Zhu, Fang Xie and R S Dwyer-Joyce

Polymers 2020, 12(3), 665; https://doi.org/10.3390/polym12030665 - 17 Mar 2020

Cited by 38 | Viewed by 4936

Abstract

In this study, bearing bushes made of polyetheretherketone (PEEK), 30 wt % carbon fibre reinforced PEEK, 30 wt % glass fibre reinforced PEEK, each 10 wt % of PTFE, graphite and carbon fibre modified PEEK were investigated on a purpose built pin joint [...] Read more.

In this study, bearing bushes made of polyetheretherketone (PEEK), 30 wt % carbon fibre reinforced PEEK, 30 wt % glass fibre reinforced PEEK, each 10 wt % of PTFE, graphite and carbon fibre modified PEEK were investigated on a purpose built pin joint test rig. The unlubricated friction and wear behaviour was assessed in sliding contact with a 300M shaft, subjected to a nominal pressure of 93 MPa, articulating sliding speed of 45 °/s. The worn surface and the subsurface layer were studied using optical profilometry and scanning electron microscopy (SEM). Due to thermal sensitivity of PEEK composites, friction energy and temperature rise were analysed for determining the friction and wear mechanism. The bush made of PTFE, graphite and carbon fibre (each 10 wt %) modified PEEK presented the best performance for friction coefficient, wear loss, friction energy and temperature rise. Current work demonstrated that reinforcement modified PEEK composite possesses desirable properties to perform as a load bearing bush in certain tribological applications. Full article

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13 pages, 2439 KiB

Open AccessArticle

Utilization of Waste Bamboo Fibers in Thermoplastic Composites: Influence of the Chemical Composition and Thermal Decomposition Behavior

by Chin-Hao Yeh and Teng-Chun Yang

Polymers 2020, 12(3), 636; https://doi.org/10.3390/polym12030636 - 11 Mar 2020

Cited by 23 | Viewed by 5351

Abstract

In this study, four types of waste bamboo fibers (BFs), Makino bamboo (Phyllostachys makinoi), Moso bamboo (Phyllostachys pubescens), Ma bamboo (Dendrocalamus latiflorus), and Thorny bamboo (Bambusa stenostachya), were used as reinforcements and incorporated into polypropylene [...] Read more.

In this study, four types of waste bamboo fibers (BFs), Makino bamboo (Phyllostachys makinoi), Moso bamboo (Phyllostachys pubescens), Ma bamboo (Dendrocalamus latiflorus), and Thorny bamboo (Bambusa stenostachya), were used as reinforcements and incorporated into polypropylene (PP) to manufacture bamboo–PP composites (BPCs). To investigate the effects of the fibers from these bamboo species on the properties of the BPCs, their chemical compositions were evaluated, and their thermal decomposition kinetics were analyzed by the Flynn–Wall–Ozawa (FWO) method and the Criado method. Thermogravimetric results indicated that the Makino BF was the most thermally stable since it showed the highest activation energy at various conversion rates that were calculated by the FWO method. Furthermore, using the Criado method, the thermal decomposition mechanisms of the BFs were revealed by diffusion when the conversion rates (α) were below 0.5. When the α values were above 0.5, their decomposition mechanisms trended to the random nucleation mechanism. Additionally, the results showed that the BPC with Thorny BFs exhibited the highest moisture content and water absorption rate due to this BF having high hemicellulose content, while the BPC with Makino BFs had high crystallinity and high lignin content, which gave the resulting BPC better tensile properties. Full article

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9 pages, 784 KiB

Open AccessCommunication

Role of Nanoparticle–Polymer Interactions on the Development of Double-Network Hydrogel Nanocomposites with High Mechanical Strength

by Andrew Chang, Nasim Babhadiashar, Emma Barrett-Catton and Prashanth Asuri

Polymers 2020, 12(2), 470; https://doi.org/10.3390/polym12020470 - 18 Feb 2020

Cited by 34 | Viewed by 4047

Abstract

Extensive experimental and theoretical research over the past several decades has pursued strategies to develop hydrogels with high mechanical strength. Our study investigated the effect of combining two approaches, addition of nanoparticles and crosslinking two different polymers (to create double-network hydrogels), on the [...] Read more.

Extensive experimental and theoretical research over the past several decades has pursued strategies to develop hydrogels with high mechanical strength. Our study investigated the effect of combining two approaches, addition of nanoparticles and crosslinking two different polymers (to create double-network hydrogels), on the mechanical properties of hydrogels. Our experimental analyses revealed that these orthogonal approaches may be combined to synthesize hydrogel composites with enhanced mechanical properties. However, the enhancement in double network hydrogel elastic modulus due to incorporation of nanoparticles is limited by the ability of the nanoparticles to strongly interact with the polymers in the network. Moreover, double-network hydrogel nanocomposites prepared using lower monomer concentrations showed higher enhancements in elastic moduli compared to those prepared using high monomer concentrations, thus indicating that the concentration of hydrogel monomers used for the preparation of the nanocomposites had a significant effect on the extent of nanoparticle-mediated enhancements. Collectively, these results demonstrate that the hypotheses previously developed to understand the role of nanoparticles on the mechanical properties of hydrogel nanocomposites may be extended to double-network hydrogel systems and guide the development of next-generation hydrogels with extraordinary mechanical properties through a combination of different approaches. Full article

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13 pages, 3354 KiB

Open AccessArticle

Effect of Na₂CO₃ on the Microstructure and Macroscopic Properties and Mechanism Analysis of PVA/CMC Composite Film

by Jufang Zhu, Qiuying Li, Yanchao Che, Xingchen Liu, Chengcheng Dong, Xinyu Chen and Chao Wang

Polymers 2020, 12(2), 453; https://doi.org/10.3390/polym12020453 - 14 Feb 2020

Cited by 56 | Viewed by 5716

Abstract

Polyvinyl alcohol (PVA)/carboxyl methyl cellulose sodium (CMC)/Na₂CO₃ composite films with different contents of Na₂CO₃ were prepared by blending and solution-casting. The effect of Na₂CO₃ on the microstructure of PVA/CMC composite film was analyzed by [...] Read more.

Polyvinyl alcohol (PVA)/carboxyl methyl cellulose sodium (CMC)/Na₂CO₃ composite films with different contents of Na₂CO₃ were prepared by blending and solution-casting. The effect of Na₂CO₃ on the microstructure of PVA/CMC composite film was analyzed by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). Its macroscopic properties were analyzed by water sorption, solubility, and dielectric constant tests. The results show that the microstructure of PVA/CMC/Na₂CO₃ composite films was different from that of PVA and PVA/CMC composite films. In addition, compared to PVA and PVA/CMC composite films, the water sorption of PVA/CMC/Na₂CO₃ composite films relatively increased, the solubility in water significantly decreased, and the dielectric properties significantly improved. All these results indicate that the hydrogen bonding interaction between PVA and CMC increased and the crystallinity of PVA decreased after the addition of Na₂CO₃. This was also a direct factor leading to increased water sorption, decreased solubility, and enhanced dielectric properties. The reaction mechanism of PVA, CMC, and Na₂CO₃ is proposed to further evaluate the effect of Na₂CO₃ on the microstructure and macroscopic properties of PVA/CMC/Na₂CO₃ composite films. Full article

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14 pages, 17725 KiB

Open AccessArticle

Effect of Various Surface Treatments on the Performance of Jute Fibers Filled Natural Rubber (NR) Composites

by Kumarjyoti Roy, Subhas Chandra Debnath, Lazaros Tzounis, Aphiwat Pongwisuthiruchte and Pranut Potiyaraj

Polymers 2020, 12(2), 369; https://doi.org/10.3390/polym12020369 - 7 Feb 2020

Cited by 56 | Viewed by 4150

Abstract

In the present study, the suitability of various chemical treatments to improve the performance of jute fibers (JFs) filled natural rubber (NR) composites was explored. The surface of JFs was modified by three different surface treatments, namely, alkali treatment, combined alkali/stearic acid treatment [...] Read more.

In the present study, the suitability of various chemical treatments to improve the performance of jute fibers (JFs) filled natural rubber (NR) composites was explored. The surface of JFs was modified by three different surface treatments, namely, alkali treatment, combined alkali/stearic acid treatment and combined alkali/silane treatment. Surface modified JFs were characterized by X-ray diffraction (XRD) pattern, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). The reinforcing effect of untreated and surface treated JFs in NR composites was comparatively evaluated in terms of cure, mechanical, morphological and thermal properties. Combined alkali/silane treated JFs filled NR composite showed considerably higher torque difference, tensile modulus, hardness and tensile strength as compared to either untreated or other surface treated JFs filled NR systems. A crosslink density measurement suggested effective rubber-fibers interaction in combined alkali/silane treated JFs filled NR composite. Morphological analysis confirmed the improvement in the interfacial bonding between NR matrix and JFs due to combined alkali/silane treatment allowing an efficient “stress-transfer” mechanism. As a whole, combined alkali/silane treatment was found to be most efficient surface treatment method to develop strong interfacial adhesion between NR matrix and JFs. Full article

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2019

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17 pages, 4147 KiB

Open AccessArticle

Structure and Properties of Polysulfone Filled with Modified Twill Weave Carbon Fabrics

by Dilyus I. Chukov, Sarvarkhodza G. Nematulloev, Viсtor V. Tсherdyntsev, Valerii G. Torokhov, Andrey A. Stepashkin, Mikhail Y. Zadorozhnyy, Dmitry D. Zherebtsov and Galal Sherif

Polymers 2020, 12(1), 50; https://doi.org/10.3390/polym12010050 - 30 Dec 2019

Cited by 15 | Viewed by 4431

Abstract

Carbon fabrics are widely used in polymer based composites. Nowadays, most of the advanced high-performance composites are based on thermosetting polymer matrices such as epoxy resin. Thermoplastics have received high attention as polymer matrices due to their low curing duration, high chemical resistance, [...] Read more.

Carbon fabrics are widely used in polymer based composites. Nowadays, most of the advanced high-performance composites are based on thermosetting polymer matrices such as epoxy resin. Thermoplastics have received high attention as polymer matrices due to their low curing duration, high chemical resistance, high recyclability, and mass production capability in comparison with thermosetting polymers. In this paper, we suggest thermoplastic based composite materials reinforced with carbon fibers. Composites based on polysulfone reinforced with carbon fabrics using polymer solvent impregnation were studied. It is well known that despite the excellent mechanical properties, carbon fibers possess poor wettability and adhesion to polymers because of the fiber surface chemical inertness and smoothness. Therefore, to improve the fiber–matrix interfacial interaction, the surface modification of the carbon fibers by thermal oxidation was used. It was shown that the surface modification resulted in a noticeable change in the functional composition of the carbon fibers’ surface and increased the mechanical properties of the polysulfone based composites. Significant increase in composites mechanical properties and thermal stability as a result of carbon fiber surface modification was observed. Full article

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14 pages, 7053 KiB

Open AccessArticle

Pinned Hybrid Glass-Flax Composite Laminates Aged in Salt-Fog Environment: Mechanical Durability

by Luigi Calabrese, Vincenzo Fiore, Paolo Bruzzaniti, Tommaso Scalici and Antonino Valenza

Polymers 2020, 12(1), 40; https://doi.org/10.3390/polym12010040 - 26 Dec 2019

Cited by 22 | Viewed by 4111

Abstract

The aim of the present paper is to study the mechanical performance evolution of pinned hybrid glass-flax composite laminates under environment aging conditions. Hybrid glass-flax fibers/epoxy pinned laminates were exposed to salt-spray fog environmental conditions up to 60 days. With the purpose of [...] Read more.

The aim of the present paper is to study the mechanical performance evolution of pinned hybrid glass-flax composite laminates under environment aging conditions. Hybrid glass-flax fibers/epoxy pinned laminates were exposed to salt-spray fog environmental conditions up to 60 days. With the purpose of assessing the relationship between mechanical performances and failure mechanisms at increasing aging time, single lap joints at varying joint geometry (i.e., hole diameter D and hole distance E from free edge) were characterized after 0 days (i.e., unaged samples), 30 days, and 60 days of salt-fog exposition. Based on this approach, the property–structure relationship of the composite laminates was assessed on these critical environmental conditions. In particular, a reduction of failure strength for long-aging-time-aged samples was observed in the range 20–30% compared to unaged one. Due to the natural fiber degradation in a salt-fog environment, premature catastrophic fractures mode due to shear-out and net-tension were found, related to reduced joint fracture strength. This behavior identifies that this type of joint requires a careful design in order to guarantee an effective mechanical stability of the composite hybrid joint under long-term operating conditions in an aggressive environment. Full article

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19 pages, 8720 KiB

Open AccessArticle

Investigation on the Fiber Orientation Distributions and Their Influence on the Mechanical Property of the Co-Injection Molding Products

by Chao-Tsai Huang, Xuan-Wei Chen and Wei-Wen Fu

Polymers 2020, 12(1), 24; https://doi.org/10.3390/polym12010024 - 20 Dec 2019

Cited by 23 | Viewed by 4831

Abstract

In recent years, due to the rapid development of industrial lightweight technology, composite materials based on fiber reinforced plastics (FRP) have been widely used in the industry. However, the environmental impact of the FRPs is higher each year. To overcome this impact, co-injection [...] Read more.

In recent years, due to the rapid development of industrial lightweight technology, composite materials based on fiber reinforced plastics (FRP) have been widely used in the industry. However, the environmental impact of the FRPs is higher each year. To overcome this impact, co-injection molding could be one of the good solutions. But how to make the suitable control on the skin/core ratio and how to manage the glass fiber orientation features are still significant challenges. In this study, we have applied both computer-aided engineering (CAE) simulation and experimental methods to investigate the fiber feature in a co-injection system. Specifically, the fiber orientation distributions and their influence on the tensile properties for the single-shot and co-injection molding have been discovered. Results show that based on the 60:40 of skin/core ratio and same materials, the tensile properties of the co-injection system, including tensile stress and modulus, are a little weaker than that of the single-shot system. This is due to the overall fiber orientation tensor at flow direction (A₁₁) of the co-injection system being lower than that of the single-shot system. Moreover, to discover and verify the influence of the fiber orientation features, the fiber orientation distributions (FOD) of both the co-injection and single-shot systems have been observed using micro-computerized tomography (μ-CT) technology to scan the internal structures. The scanned images were further utilizing Avizo software to perform image analyses to rebuild the fiber structure. Specifically, the fiber orientation tensor at flow direction (A₁₁) of the co-injection system is about 89% of that of the single-shot system in the testing conditions. This is because the co-injection part has lower tensile properties. Furthermore, the difference of the fiber orientation tensor at flow direction (A₁₁) between the co-injection and the single-shot systems is further verified based on the fiber morphology of the μ-CT scanned image. The observed result is consistent with that of the FOD estimation using μ-CT scan plus image analysis. Full article

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15 pages, 6938 KiB

Open AccessArticle

Surface Modification of PET Fiber with Hybrid Coating and Its Effect on the Properties of PP Composites

by Yapeng Mao, Qiuying Li and Chifei Wu

Polymers 2019, 11(10), 1726; https://doi.org/10.3390/polym11101726 - 21 Oct 2019

Cited by 15 | Viewed by 5844

Abstract

Surface modification fundamentally influences the morphology of polyethylene terephthalate (PET) fibers produced from abandoned polyester textiles and improve the compatibility between the fiber and the matrix. In this study, PET fiber was modified through solution dip-coating using a novel synthesized tetraethyl orthosilicate (TEOS)/KH550/ [...] Read more.

Surface modification fundamentally influences the morphology of polyethylene terephthalate (PET) fibers produced from abandoned polyester textiles and improve the compatibility between the fiber and the matrix. In this study, PET fiber was modified through solution dip-coating using a novel synthesized tetraethyl orthosilicate (TEOS)/KH550/ polypropylene (PP)-g-MAH (MPP) hybrid (TMPP). The PET fiber with TMPP modifier was exposed to the air. SiO₂ particles would be hydrolyzed from TEOS and become the crystalline cores of MPP. Then, the membrane formed by MPP, SiO₂ and KH550 covered the surface of the PET fiber. TMPP powder was investigated and characterized by fourier transform infrared spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). TMPP-modified PET fiber was researched by X-ray diffraction and SEM. Furthermore, tensile strength of single fiber was also tested. PET fiber/PP composites were studied through dynamic mechanical analysis and SEM. Flexural properties of composites were also measured. The interfacial properties of PET fiber and PP matrix were indirectly represented by contact angle analysis. Results showed that the addition of TEOS is helpful in homogenizing the distribution of PP-g-MAH. Furthermore, TMPP generates an organic-inorganic ‘armor’ structure on PET fiber, which can make up for the damage areas on the surface of PET fiber and strengthen each single-fiber by 14.4%. Besides, bending strength and modulus of TMPP-modified PET fiber-reinforced PP composite respectively, increase by 10 and 800 MPa. The compatibility between PET fiber and PP was also confirmed to be increased by TMPP. Predictably, this work supplied a new way for PET fiber modification and exploited its potential applications in composites. Full article

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37 pages, 5930 KiB

Open AccessEditor’s ChoiceReview

Fiber-Reinforced Polymer Composites: Manufacturing, Properties, and Applications

by Dipen Kumar Rajak, Durgesh D. Pagar, Pradeep L. Menezes and Emanoil Linul

Polymers 2019, 11(10), 1667; https://doi.org/10.3390/polym11101667 - 12 Oct 2019

Cited by 1026 | Viewed by 57494

Abstract

Composites have been found to be the most promising and discerning material available in this century. Presently, composites reinforced with fibers of synthetic or natural materials are gaining more importance as demands for lightweight materials with high strength for specific applications are growing [...] Read more.

Composites have been found to be the most promising and discerning material available in this century. Presently, composites reinforced with fibers of synthetic or natural materials are gaining more importance as demands for lightweight materials with high strength for specific applications are growing in the market. Fiber-reinforced polymer composite offers not only high strength to weight ratio, but also reveals exceptional properties such as high durability; stiffness; damping property; flexural strength; and resistance to corrosion, wear, impact, and fire. These wide ranges of diverse features have led composite materials to find applications in mechanical, construction, aerospace, automobile, biomedical, marine, and many other manufacturing industries. Performance of composite materials predominantly depends on their constituent elements and manufacturing techniques, therefore, functional properties of various fibers available worldwide, their classifications, and the manufacturing techniques used to fabricate the composite materials need to be studied in order to figure out the optimized characteristic of the material for the desired application. An overview of a diverse range of fibers, their properties, functionality, classification, and various fiber composite manufacturing techniques is presented to discover the optimized fiber-reinforced composite material for significant applications. Their exceptional performance in the numerous fields of applications have made fiber-reinforced composite materials a promising alternative over solitary metals or alloys. Full article

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12 pages, 3909 KiB

Open AccessArticle

Evaluation of the Compatibility of Organosolv Lignin-Graphene Nanoplatelets with Photo-Curable Polyurethane in Stereolithography 3D Printing

by Fathirrahman Ibrahim, Denesh Mohan, Mohd Shaiful Sajab, Saiful Bahari Bakarudin and Hatika Kaco

Polymers 2019, 11(10), 1544; https://doi.org/10.3390/polym11101544 - 23 Sep 2019

Cited by 51 | Viewed by 5157

Abstract

In this study, lignin has been extracted from oil palm empty fruit bunch (EFB) fibers via an organosolv process. The organosolv lignin obtained was defined by the presence of hydroxyl-containing molecules, such as guaiacyl and syringyl, and by the presence of phenolic molecules [...] Read more.

In this study, lignin has been extracted from oil palm empty fruit bunch (EFB) fibers via an organosolv process. The organosolv lignin obtained was defined by the presence of hydroxyl-containing molecules, such as guaiacyl and syringyl, and by the presence of phenolic molecules in lignin. Subsequently, the extracted organosolv lignin and graphene nanoplatelets (GNP) were utilized as filler and reinforcement in photo-curable polyurethane (PU), which is used in stereolithography 3D printing. The compatibility as well as the characteristic and structural changes of the composite were identified through the mechanical properties of the 3D-printed composites. Furthermore, the tensile strength of the composited lignin and graphene shows significant improvement as high as 27%. The hardness of the photo-curable PU composites measured by nanoindentation exhibited an enormous improvement for 0.6% of lignin-graphene at 92.49 MPa with 238% increment when compared with unmodified PU. Full article

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18 pages, 5540 KiB

Open AccessArticle

Preparation and Properties of Rubber Blends for High-Damping-Isolation Bearings

by Tuo Lei, Yong-Wang Zhang, Dong-Liang Kuang and Yong-Rui Yang

Polymers 2019, 11(8), 1374; https://doi.org/10.3390/polym11081374 - 20 Aug 2019

Cited by 24 | Viewed by 8220

Abstract

To improve the energy dissipation capacity of rubber isolation bearings, it is important to find a new rubber material with good applicability and high damping properties. Two types of blends were prepared using nitrile rubber (NBR), brominated butyl rubber (BIIR) and ethylene-vinyl acetate [...] Read more.

To improve the energy dissipation capacity of rubber isolation bearings, it is important to find a new rubber material with good applicability and high damping properties. Two types of blends were prepared using nitrile rubber (NBR), brominated butyl rubber (BIIR) and ethylene-vinyl acetate copolymer (EVA): NBR/BIIR and NBR/BIIR/EVA. The vulcanization, mechanical and damping properties of the blends were analyzed. The results show that both blends exhibit excellent vulcanization plateaus and mechanical properties. For NBR/BIIR, as the BIIR content increases, the complementary effects of NBR and BIIR afforded by blending are enhanced. Two damping peaks appeared in the tanδ-T curve and shifted toward lower and higher temperatures, respectively, which clearly widened the effective damping temperature range. However, the damping value in the valley of the tanδ-T curve was as low as 0.39. For NBR/BIIR/EVA, the addition of EVA greatly increased damping in the valley of the tanδ-T curve to approximately 0.54. EVA was observed to be the optimal polymer for improving the compatibility of the NBR/BIIR blend. Moreover, hot air thermal aging tests showed that both blends demonstrated good stability. Full article

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11 pages, 4967 KiB

Open AccessArticle

Effect of Formation Route on the Mechanical Properties of the Polyethersulfone Composites Reinforced with Glass Fibers

by Galal Sherif, Dilyus Chukov, Victor Tcherdyntsev and Valerii Torokhov

Polymers 2019, 11(8), 1364; https://doi.org/10.3390/polym11081364 - 19 Aug 2019

Cited by 42 | Viewed by 4911

Abstract

Interfacial interaction is one of the most important factors that affect the mechanical properties of the fiber reinforced composites. The effect of fabrics′ sizing removal from glass fibers’ surface by thermal treatment on the mechanical characteristics of polyethersulfone based composites at different fiber [...] Read more.

Interfacial interaction is one of the most important factors that affect the mechanical properties of the fiber reinforced composites. The effect of fabrics′ sizing removal from glass fibers’ surface by thermal treatment on the mechanical characteristics of polyethersulfone based composites at different fiber to polymer weight ratios was investigated. Three fiber to polymer weight ratios of 50/50, 60/40, and 70/30 were studied. Flexural and shear tests were carried out to illustrate the mechanical properties of the composites; the structure was studied using Fourier-transform infrared spectroscopy and scanning electron microscopy. It was shown that solution impregnation of glass fabrics with polyethersulfone before compression molding allows to achieve good mechanical properties of composites. The thermal treatment of glass fabrics before impregnation results in an increase in flexural and shear strength for all the composites due to the improvement of fiber–matrix interaction. Full article

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