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Mechanical Properties of Fiber Reinforced Polymer Composites
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Mechanical Properties of Fiber Reinforced Polymer Composites

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Physics and Theory".

Deadline for manuscript submissions: closed (20 February 2023) | Viewed by 40493

Special Issue Editors

Dr. Pengda Li

E-Mail Website
Guest Editor
College of Civil and Transportation Engineering, Shenzhen University, Shenzhen, China
Interests: composite structure; FRP confined concrete; FRP repairing or retrofitting; LRS (large rupture strain)–FRP; stress–strain behavior; bond–slip relationship; durability
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Junjie Zeng

E-Mail Website
Guest Editor
School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 523083, China
Interests: smart building materials; sustainable and low-carbon building materials; recycled building materials; innovative building materials life cycle impact analysis; structural deterioration; novel repair methods; eco-friendly retrofitting methods; novel fiber-reinforced polymer (FRP) structures; ultra-high performance concrete
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Yang Wei

E-Mail Website
Guest Editor
School of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China
Interests: hydraulic concrete materials; underwater inspection and reinforcement of water-related structures; bridge detection and reinforcement technology; bamboo (wood) structure; new composite structure; concrete structural damage detection
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fiber-reinforced polymers (FRPs), known for their high strength–weight ratio, durability, and excellent anti-corrosion properties, have emerged as a popular material in new structures and in the strengthening and retrofitting of existing structures. With the development of materials science, some high-performance materials and structural forms with FRP have been developed. These emerging research fields have also attracted extensive interest from the research community. For safe and effective usage of high-performance structures with FRP composites, plausible approaches for estimating the mechanical properties and sustainable design theory of such structures need to be developed.

This Special Issue aims to present recent advances and emerging cross-disciplinarity in FRP composites by collecting mainly integrated studies on the mechanical properties of FRP composite structures. Studies from the testing, analysis, and numerical modeling of the composite structure to the design of new structures and repair and retrofit of existing FRP composite structures are welcome. Manuscripts are expected to reflect original research and technological advances on topics that include but are not limited to:

  • FRPs in the forms of sheets, plates, tubes, bars, etc.;
  • FRP-strengthened structures;
  • Interfacial behavior between FRP and substrate;
  • Thin-walled FRP composite structures;
  • FRP reinforced wood/bamboo structures;
  • FRP in combination with non-traditional cementitious materials.

Dr. Pengda Li
Dr. Junjie Zeng
Prof. Dr. Yang Wei
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • composite structure
  • FRP confined concrete
  • mechanical properties
  • bond–slip relationship
  • thin-walled composite
  • FRP bars
  • composite structure durability
  • FRP repairing or retrofitting
  • FRP–concrete–steel hybrid structures
  • biological fiber materials and structure
  • bamboo/wood structure
  • bamboo/wood composite structure
  • bamboo/wood concrete structure

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Published Papers (17 papers)

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Research

13 pages, 4471 KiB  
Article
Experimental Investigation on the Bonding Strength of Knotted CFRP Bars in Bulk Plastics
by Cihan Ciftci
Polymers 2023, 15(9), 2036; https://doi.org/10.3390/polym15092036 - 25 Apr 2023
Cited by 2 | Viewed by 1620
Abstract
Improving the interfacial bonding strength of CFRP materials is crucial for enabling the development of novel composite beam structures with higher specific bending strength demanded by the composite industry. In this research study, for reinforced bulk plastic composites, the aim is to enhance [...] Read more.
Improving the interfacial bonding strength of CFRP materials is crucial for enabling the development of novel composite beam structures with higher specific bending strength demanded by the composite industry. In this research study, for reinforced bulk plastic composites, the aim is to enhance the interfacial bonding strength of CFRP bar elements in bulk plastics by on the formation of knots. In this context, firstly, the knotted CFRP bars with varying cross-sectional areas were manufactured under laboratory conditions for the experimental investigation on the effect of knots on bonding strength. Commercially available smooth-surfaced CFRP bars were also purchased to be used as the reference. Then, all these CFRP bars were subjected to pull-out tests by using in bulk plastics. According to the test results, it was observed that the interfacial bonding strength of CFRP bars in bulk plastic materials could be increased up to 233% because of the knots. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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16 pages, 6473 KiB  
Article
Reinforced L-Shaped Frame Made of Textile-Reinforced Concrete
by Jiří Žalský, Tomáš Vlach, Jakub Řepka, Jakub Hájek and Petr Hájek
Polymers 2023, 15(2), 376; https://doi.org/10.3390/polym15020376 - 10 Jan 2023
Cited by 1 | Viewed by 1576
Abstract
Textile-reinforced concrete is becoming more and more popular. The material enables the realization of very thin structures and shells, often with organic shapes. However, a problem with this reinforcement occurs when the structure is bent (contains a corner), and the flexural stiffness around [...] Read more.
Textile-reinforced concrete is becoming more and more popular. The material enables the realization of very thin structures and shells, often with organic shapes. However, a problem with this reinforcement occurs when the structure is bent (contains a corner), and the flexural stiffness around this bent area is required. This article presents the design, solution, and load-bearing capacity of an L-shaped rigid frame made of textile-reinforced concrete. Basic material parameters of concrete matrix and carbon textile reinforcement were supplemented by a four-point bending test to calibrate fracture energy Gf, critical compressive displacement Wd, solver type, and other parameters of a numerical model created by Atena Engineering in specialized non-linear structural analysis software for reinforced concrete structures. The calibrated numerical model was used to evaluate different variants of carbon textile reinforcement of the L-shaped frame. The carbon textile reinforcement was homogenized using epoxy resin to ensure the interaction of all fibers, and its surface was modified with fine-grained silica sand to increase the cohesion with the concrete matrix. Specimens were produced based on the most effective variant of the L-shaped frame reinforcement to be experimentally tested. Thanks to the original shaping and anchoring of the reinforcement in the corner area, the frame with composite textile reinforcement is rigid and can transmit the bending stresses in both positive and negative directions. The results of the mechanical loading test on small experimental specimens correspond well to the results of numerical modeling using Atena Engineering software. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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17 pages, 4721 KiB  
Article
Flexural Strengthening of Large-Scale RC Beams with Nonprestressed and Prestressed CFRP Using Different Anchorages
by Hai-Tao Wang, Zhi-Ning Bian, Guo-Wen Xu, Min-Sheng Chen, Hao Xiong and Sai-Sai Liu
Polymers 2022, 14(24), 5498; https://doi.org/10.3390/polym14245498 - 15 Dec 2022
Cited by 5 | Viewed by 1580
Abstract
Externally bonded carbon-fiber-reinforced polymer (CFRP) technology can be used by different methods based on the anchorage device, CFRP type, and prestressing/nonprestressing. However, a direct comparison between the strengthening efficacies of different methods is still lacking. Seven large-scale RC beams were tested in this [...] Read more.
Externally bonded carbon-fiber-reinforced polymer (CFRP) technology can be used by different methods based on the anchorage device, CFRP type, and prestressing/nonprestressing. However, a direct comparison between the strengthening efficacies of different methods is still lacking. Seven large-scale RC beams were tested in this study to investigate the influences of the anchorage method, CFRP type, prestress, and prestressing system on the flexural strengthening efficacy of RC beams. The test results showed that the ultimate load increased by 38.3%, whereas the cracking and yielding loads were slightly affected when the anchorage method was enhanced from CFRP U-wraps to wedge-clamp anchors. The CFRP plate and CFRP sheet could provide a rather close flexural strengthening efficacy under the same CFRP strengthening amount. Compared to the nonprestressed CFRP plate, the prestressed CFRP plate was highly superior in improving the flexural behavior of RC beams. The cracking, yielding, and ultimate loads of the prestressed CFRP-strengthened specimens were 57.1%, 22.9%, and 5.9%, respectively, higher than those of the nonprestressed CFRP-strengthened specimen with an effective anchorage. The two types of prestressing systems based on the adhesive-friction anchor and wedge-clamp anchor were proven to be effective for flexural strengthening of RC beams with prestressed CFRP plates, and they could provide almost the same strengthening effect. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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20 pages, 4157 KiB  
Article
Dynamic Splitting Tensile Behaviour of Concrete Confined by Natural Flax and Glass FRP
by Wenjie Wang, Zonglai Mo, Yunpeng Zhang and Nawawi Chouw
Polymers 2022, 14(20), 4424; https://doi.org/10.3390/polym14204424 - 19 Oct 2022
Cited by 4 | Viewed by 1833
Abstract
Flax fibre has been used to reinforce concrete composite, but its dynamic properties have not been thoroughly studied. This study investigates the dynamic splitting tensile properties of plain concrete (PC) confined by flax-fibre-reinforced polymer (FFRP) and glass-fibre-reinforced polymer (GFRP). The dynamic splitting tensile [...] Read more.
Flax fibre has been used to reinforce concrete composite, but its dynamic properties have not been thoroughly studied. This study investigates the dynamic splitting tensile properties of plain concrete (PC) confined by flax-fibre-reinforced polymer (FFRP) and glass-fibre-reinforced polymer (GFRP). The dynamic splitting tensile tests were carried out on PC, FFRP-PC, and GFRP-PC cylinder specimens by the high-speed servo-hydraulic machine, with the impact-induced strain rates ranging from 0.1 to 58 s−1. The effect of the FRP confinement, FRP thickness and strain rate on the dynamic splitting tensile behaviour were assessed. The results indicated that similar confinement effectiveness of FFRP and GFRP is observed. The dynamic tensile strength of 1- and 2-layer FFRP-PC increased by 29% and 67%, and the one- and two-layer GFRP-PC increased by 32% and 84%, respectively. FFRP-PC and GFRP-PC cylinders showed less sensitivity to the strain rate compared with PC. The empirical relationship between the tensile DIF and strain rate for PC, FFRP-PC and GFRP-PC was proposed based on experimental data. The proposed model was developed to predict the dynamic splitting tensile strength. The results suggested the potential of FFRP composites applied into concrete structures under extreme dynamic loadings. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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17 pages, 2411 KiB  
Article
Effect of Stacking Sequence on Long-Term Creep Performance of Pultruded GFRP Composites
by Muhammad Rizal Muhammad Asyraf, Agusril Syamsir, Nazirul Mubin Zahari, Abu Bakar Mohd Supian, Fathoni Usman and Zarina Itam
Polymers 2022, 14(19), 4064; https://doi.org/10.3390/polym14194064 - 28 Sep 2022
Cited by 18 | Viewed by 2378
Abstract
Pultruded glass-fibre reinforced polymer (pGFRP) composites are classified as lightweight material, which exhibit high strength-to-weight ratio for structural usage. This composite material has been applied as cross-arm members in transmission towers due to its ability in thermal and electrical insulation. However, the influence [...] Read more.
Pultruded glass-fibre reinforced polymer (pGFRP) composites are classified as lightweight material, which exhibit high strength-to-weight ratio for structural usage. This composite material has been applied as cross-arm members in transmission towers due to its ability in thermal and electrical insulation. However, the influence of the stacking sequence of pGFRP composite on its mechanical performance has not been fully covered in the literature to explain the long-term durability of the current cross-arm designs. The study expected to evaluate five fiber layers with various stacking sequences in terms of quasi-static and creep tests in a four-point bending mode. The creep test was performed for 1440 h (60 days). These composites were fabricated using the pultrusion process in the form of a square hollow structure. Later, it was cut into composite coupons with various sizes depending on the test conducted. The results showed that nine layers with 0°/45°/0°/−45°/0°/−45°/0°/45°/0° had the ultimate flexural strength. This stacking sequence configurations seemed to be optimally manufactured in continuous roving fibre by alternating between 0° and ±45° fiber orientations. Additionally, the S-9 pGFRP composite sample showed that it had a low-creep deflection with high elastic and apparent creep moduli in 1440 h. In terms of strength reduction factor, this configuration was recorded as the highest. The findings showed that the nine layers of pGFRP composites with alternation of 0° and ±45° fiber orientations were highly suitable for structural application at transmission towers for a long-term operation. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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18 pages, 36584 KiB  
Article
Effect of Aggregate Size on the Axial Compressive Behavior of FRP-Confined Coral Aggregate Concrete
by Pengda Li, Deqing Huang, Ruiyu Li, Rongkang Li and Fang Yuan
Polymers 2022, 14(18), 3877; https://doi.org/10.3390/polym14183877 - 16 Sep 2022
Cited by 10 | Viewed by 1508
Abstract
Using locally available raw materials for preparing concrete, such as coral reefs, seawater, and sea sand, is conducive to compensating for the shortage of construction materials used on remote islands. Jacketing fiber-reinforced polymer (FRP), as passive confinement, is a practical approach to enhance [...] Read more.
Using locally available raw materials for preparing concrete, such as coral reefs, seawater, and sea sand, is conducive to compensating for the shortage of construction materials used on remote islands. Jacketing fiber-reinforced polymer (FRP), as passive confinement, is a practical approach to enhance the strength, ductility, and durability of such coral aggregate concrete (CAC). Rational and economical CAC structural design requires understanding the interactions between the CAC fracture process and FRP confinement. The coral aggregate size is the critical parameter of their interaction since it affects the crack propagation of CAC and FRP confinement efficiency. This study conducted axial compression tests on FRP-confined CAC cylinders with varying coral aggregate sizes and FRP confinement levels. The test results indicate that the coral aggregate sizes affected the unconfined CAC strength. In addition, the dilation behavior of FRP-confined CAC varied with aggregate sizes, showing that CAC with smaller coral aggregate featured a more uniform hoop strain distribution and larger FRP rupture strain. These coupling effects are epitomized by the variation in the transition stress on the stress–strain curve, which makes the existing stress–strain models not applicable for FRP-confined CAC. A modified stress–strain model is subsequently proposed. Finally, the practical and environmental implications of the present study are discussed. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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21 pages, 10044 KiB  
Article
Processing, Characterization of Furcraea foetida (FF) Fiber and Investigation of Physical/Mechanical Properties of FF/Epoxy Composite
by Abhishek Sadananda Madival, Deepak Doreswamy, Srinivasulu Maddasani, Manjunath Shettar and Raviraj Shetty
Polymers 2022, 14(7), 1476; https://doi.org/10.3390/polym14071476 - 6 Apr 2022
Cited by 16 | Viewed by 3330
Abstract
In recent days the rising concern over environmental pollution with excessive use of synthetic materials has led to various eco-friendly innovations. Due to the organic nature, abundance and higher strength, natural fibers are gaining a lot of interest among researchers and are also [...] Read more.
In recent days the rising concern over environmental pollution with excessive use of synthetic materials has led to various eco-friendly innovations. Due to the organic nature, abundance and higher strength, natural fibers are gaining a lot of interest among researchers and are also extensively used by various industries to produce ecological products. Natural fibers are widely used in the composite industry as an alternative to synthetic fibers for numerous applications and new sources of fiber are continuously being explored. In this study, a fiber extracted from the Furcraea foetida (FF) plant is characterized for its feasibility as a reinforcement to fabricate polymer composite. The results show that the fiber has a density of 0.903 ± 0.07 g/cm3, tensile strength (σt) of 170.47 ± 24.71 MPa and the fiber is thermally stable up to 250 °C. The chemical functional groups and elements present in the FF fiber are evaluated by conducting Fourier transform infrared spectroscopy (FT-IR) and energy dispersive spectroscopy (EDS). The addition of FF fibers in epoxy reduced the density (13.44%) and hardness (10.9%) of the FF/Epoxy (FF/E) composite. However, the void content (Vc < 8%) and water absorption (WA: < 6%) rate increased in the composite. The FF/E composite with 30% volume of FF fibers showed maximum σt (32.14 ± 5.54 MPa) and flexural strength (σf: 80.23 ± 11.3 MPa). Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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17 pages, 126492 KiB  
Article
Study of the Behavior of Square Concrete-Filled CFRP Steel Tubular under a Bending-Torsion Load
by Qing-Li Wang, Hang-Cheng Gao and Kuan Peng
Polymers 2022, 14(7), 1472; https://doi.org/10.3390/polym14071472 - 5 Apr 2022
Cited by 1 | Viewed by 1960
Abstract
To study the behavior of square concrete-filled CFRP (carbon fiber polymer) steel tubular under bending-torsional load, nine square section concrete-filled CFRP steel tubular specimens are designed. The T-θ curve and failure mode of square concrete-filled CFRP steel tubular are studied under a bending-torsional [...] Read more.
To study the behavior of square concrete-filled CFRP (carbon fiber polymer) steel tubular under bending-torsional load, nine square section concrete-filled CFRP steel tubular specimens are designed. The T-θ curve and failure mode of square concrete-filled CFRP steel tubular are studied under a bending-torsional load. Based on the test results, a finite element modeling method is proposed by using the finite element software ABAQUS, and the simulation results are compared with the experimental results. The results show that the simulation is in good agreement with the experimental results. On the basis of verifying the reliability of the model, the whole stress process and parameter analysis of the component are studied, and the calculation expression of bearing capacity of square concrete-filled CFRP steel tubular under bending-torsion load is proposed. The predicted specimen-bearing capacity of the proposed calculation expression of the bearing capacity of square concrete-filled CFRP steel tubular under bending-torsion load is basically consistent with the test results. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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20 pages, 3618 KiB  
Article
Effectiveness and Efficiency of Externally Bonded CFRP Sheets for Shear Strengthening of RC Beam-Column Joints
by Bu Wang, Xianhui Wu, Qi Liu, Yueyue Wu, Fei Huang, Linfeng Xu, Xing Wu and Yuanxin Deng
Polymers 2022, 14(7), 1347; https://doi.org/10.3390/polym14071347 - 26 Mar 2022
Cited by 4 | Viewed by 2345
Abstract
To develop feasible carbon fiber reinforced polymer (CFRP) retrofit schemes for the shear strengthening of real three-dimensional reinforced concrete (RC) beam-column joints, a series of parameters in relation to the contributions of the CFRP sheets externally bonded to joint panels was numerically investigated [...] Read more.
To develop feasible carbon fiber reinforced polymer (CFRP) retrofit schemes for the shear strengthening of real three-dimensional reinforced concrete (RC) beam-column joints, a series of parameters in relation to the contributions of the CFRP sheets externally bonded to joint panels was numerically investigated in this study. The parameters include CFRP reinforcement ratio, CFRP layout, transverse beam-to-joint panel width ratio, transverse beam-to-joint panel height ratio, location of transverse beam, and number of transverse beams. Strengthening efficiency, a new dimensionless index, was introduced to evaluate the residual effect of a CFRP-strengthening system weakened by the presence of transverse beams in comparison with the increase in joint shear capacity in relation to the one-way counterpart. The results obtained from 44 nonlinear finite element models, which were calibrated against experimental observations, confirmed the effectiveness of the CFRP strengthening technique with regard to the relatively wide ranges of the parameters. The significant differences among the roles of the parameters were revealed, and the reasons behind the differences were analyzed. Furthermore, the shear mechanism of the CFRP-retrofitted joint panels was discussed with the proposed strut-and-tie model. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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15 pages, 3959 KiB  
Article
Flexural Creep Behaviour of Pultruded GFRP Composites Cross-Arm: A Comparative Study on the Effects of Stacking Sequence
by Abdulrahman Alhayek, Agusril Syamsir, Abu Bakar Mohd Supian, Fathoni Usman, Muhammad Rizal Muhammad Asyraf and Mohd Afdzaluddin Atiqah
Polymers 2022, 14(7), 1330; https://doi.org/10.3390/polym14071330 - 25 Mar 2022
Cited by 26 | Viewed by 2342
Abstract
Pultruded glass fibre reinforced polymer (pGFRP) composites provide outstanding properties for composite polymer cross arms in power transmission line applications. This study has investigated the effects of various stacking sequences of fibres directions of pGFRP on flexural strength and creep behaviour. The use [...] Read more.
Pultruded glass fibre reinforced polymer (pGFRP) composites provide outstanding properties for composite polymer cross arms in power transmission line applications. This study has investigated the effects of various stacking sequences of fibres directions of pGFRP on flexural strength and creep behaviour. The use of static four-point bending flexural tests revealed that Stacking Sequence 2 (±45/0/90/0/90/0) had a significant flexural strength of 399.9 MPa while Stacking Sequence 1 (±45/90/0/±45) had a flexural strength of 242.5 MPa. Furthermore, the four-point bending creep experiments were performed at three distinct stress levels, notably 12%, 24%, and 37% of the ultimate flexural strength, to characterise the creep behaviour of distinct stacking sequences. Moreover, Findley’s power law equation for bending creep behaviour has revealed that the time-dependent reduction factor of Stacking Sequence 1 and Stacking Sequence 2 estimates a drop in flexural modulus of 23% and 10% respectively. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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19 pages, 5910 KiB  
Article
Multiscale Investigation on the Performance of Engineered Cementitious Composites Incorporating PE Fiber and Limstone Calcined Clay Cement (LC3)
by Guoqiang Gong, Menghuan Guo, Yingwu Zhou, Shuyue Zheng, Biao Hu, Zhongfeng Zhu and Zhenyu Huang
Polymers 2022, 14(7), 1291; https://doi.org/10.3390/polym14071291 - 23 Mar 2022
Cited by 11 | Viewed by 3184
Abstract
Limestone calcined clay cement (LC3) is successfully used to fabricate engineered cementitious composites (ECC) exhibiting tensile strength σtu of 9.55 ± 0.59 MPa or tensile strain capacity εtu of 8.53 ± 0.30%. The high tensile strength of the composites [...] Read more.
Limestone calcined clay cement (LC3) is successfully used to fabricate engineered cementitious composites (ECC) exhibiting tensile strength σtu of 9.55 ± 0.59 MPa or tensile strain capacity εtu of 8.53 ± 0.30%. The high tensile strength of the composites is closely related to the improvement of fiber/matrix interfacial bond strength, and the high ductility is attributed to the enhancement of fiber dispersion homogeneity. For the case of ECC incorporating 50% LC3, the reduction of initial cracking stress σtc that favors the growth of the crack in a controlled manner also contributes to the improvement of strain hardening behavior. The composition analysis indicates that carboaluminates and additional hydration products including C-(A)-S-H and ettringite are generated, which contributes to the densification of the microstructure of the ECC matrix. The pore structure is thus remarkably refined. Besides, when ordinary Portland cement (OPC) is partly replaced by LC3, the consumed energy and equivalent CO2 emission decrease, especially the equivalent CO2 emission with the reduction ratio attaining 40.31%. It is found that ECC using 35% LC3 exhibits the highest mechanical resistance and ECC incorporating 50% LC3 shows the highest ductility from the environmental point of view. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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13 pages, 18581 KiB  
Article
Improving Ductility for Composite Beams Reinforced with GFRP Tubes by Using Rebars/Steel Angles
by Jiansong Yuan, Danying Gao, Yin Zhang and Haitang Zhu
Polymers 2022, 14(3), 551; https://doi.org/10.3390/polym14030551 - 29 Jan 2022
Cited by 4 | Viewed by 2809
Abstract
The ductile behaviour of composite beams reinforced with glass fibre-reinforced polymer (GFRP) pultruded rectangular tubes was investigated in this paper. The composite beams were reinforced with GFRP tubes and different steel products, aiming to improve their ductility by using steel products. The main [...] Read more.
The ductile behaviour of composite beams reinforced with glass fibre-reinforced polymer (GFRP) pultruded rectangular tubes was investigated in this paper. The composite beams were reinforced with GFRP tubes and different steel products, aiming to improve their ductility by using steel products. The main parameters were the types of the steel reinforcement, namely rebars and steel angles. The flexural behaviour of four beam specimens was tested by using a four-point bending test. The experimental results show that the yield load of the specimens was determined by the steel products and the ultimate load was controlled by the GFRP tubes. Two ductility methods (displacement ductility and energy ductility) were used to evaluate the change of the ductility. Both the methods confirmed that the ductility of the composite beam was improved in varying degrees by using rebars and steel angles. Moreover, the analysis shows that improving the yield load or decreasing the ultimate load of the composite beams contributed to the improvement of the ductility. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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22 pages, 4944 KiB  
Article
Fire Performance of FRP-RC Flexural Members: A Numerical Study
by Dexin Duan, Lijun Ouyang, Wanyang Gao, Qingfeng Xu, Weidong Liu and Jian Yang
Polymers 2022, 14(2), 346; https://doi.org/10.3390/polym14020346 - 17 Jan 2022
Cited by 7 | Viewed by 2802
Abstract
Fiber-reinforced polymer (FRP) bars are increasingly used as a substitute for steel reinforcements in the construction of concrete structures, mainly due to their excellent durability characteristics. When FRP bar-reinforced concrete (referred to as FRP-RC for simplicity) members are used in indoor applications (e.g., [...] Read more.
Fiber-reinforced polymer (FRP) bars are increasingly used as a substitute for steel reinforcements in the construction of concrete structures, mainly due to their excellent durability characteristics. When FRP bar-reinforced concrete (referred to as FRP-RC for simplicity) members are used in indoor applications (e.g., in buildings), the fire performance of FRP-RC members needs to be appropriately designed to satisfy safety requirements. The bond behavior between the FRP bar and the surrounding concrete governs the composite action between the two materials and the related structural performance of the FRP-RC flexural member that will be affected when exposed to fire. However, there is a lack of reliable numerical models in the literature to quantify the effect of bond degradations of the FRP bar-to-concrete interface at high temperatures on the fire performance of FRP-RC flexural members. This paper presents a three-dimensional (3D) finite element (FE) model of FRP-RC flexural members exposed to fire and appropriately considers the temperature-dependent bond degradations of the FRP bar-to-concrete interface at high temperatures. In addition, the thermal properties of concrete and FRP bars are considered in the heat transfer analysis to predict the cross-sectional temperatures of the FRP-RC members under fire exposure. In the FE model, the mechanical properties and constitutive laws of concrete and FRP bars at high temperatures in addition to the bond degradations between them have been properly defined, thereby accurately predicting the global and local structural responses of the FRP-RC members under fire exposure. The proposed FE model has been validated by comparing the FE predictions (both temperature and midspan deflection responses during fire exposure) and the full-scale fire test results reported in the literature. The validated FE model is then used to study the effects of bond degradations on the global and local structural responses of the FRP-RC members under fire exposure. It is proved that the temperature-dependent bond degradations need to be considered to achieve accurate predictions of the failure mode and deflection responses. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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14 pages, 6360 KiB  
Article
Experimental Study on Axial Compressive Performance of Polyvinyl Alcohol Fibers Reinforced Fly Ash—Slag Geopolymer Composites
by Shuhua Xiao, Yongjian Cai, Yongchang Guo, Jiaxiang Lin, Guotao Liu, Xuewei Lan and Ying Song
Polymers 2022, 14(1), 142; https://doi.org/10.3390/polym14010142 - 30 Dec 2021
Cited by 12 | Viewed by 2277
Abstract
Geopolymer concrete (GC) has been gaining attention in research and engineering circles; however, it is a brittle material with poor tensile performance and crack resistance. To address these problems, we introduced fibers into GC. In this study, axial compression and scanning electron microscope [...] Read more.
Geopolymer concrete (GC) has been gaining attention in research and engineering circles; however, it is a brittle material with poor tensile performance and crack resistance. To address these problems, we introduced fibers into GC. In this study, axial compression and scanning electron microscope (SEM) tests were carried out on polyvinyl alcohol (PVA) short fiber reinforced low-calcium fly ash-slag-based geopolymer concrete (PFRGC). The ratio of PVA short fibers and low-calcium fly ash on the compression behavior of fiber reinforced geopolymer concrete (FRGC) were investigated and discussed. The test results show that PVA fibers play a bridging role in the cracks of the specimen and bear the load together with the matrix, so the addition of PVA fibers delayed the crack propagation of GC under axial compression. However, with the increase of low-calcium fly ash/PVA fibers, the number of unreacted fly ash particles in PFRGCs increases. Too many unreacted fly ash particles make GC more prone to micro-cracks during loading, adversely affecting compressive properties. Therefore, the axial compressive strength, elastic modulus, and Poisson’s ratio of GC decrease with the increasing low-calcium fly ash/PVA fibers. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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17 pages, 2495 KiB  
Article
An Improved C0 FE Model for the Sandwich Lattice Composite Panel
by Junqing Hong, Chunyan Shen, Weiqing Liu, Hai Fang and Laiyun Yang
Polymers 2021, 13(23), 4200; https://doi.org/10.3390/polym13234200 - 30 Nov 2021
Viewed by 1885
Abstract
Combining the improved C0 plate element using high-order zigzag theories and the beam element degenerated from the plate element, a type of analysis model for the sandwich lattice composite panel was developed. Compared with the actual test results including the mid-span deflections [...] Read more.
Combining the improved C0 plate element using high-order zigzag theories and the beam element degenerated from the plate element, a type of analysis model for the sandwich lattice composite panel was developed. Compared with the actual test results including the mid-span deflections and the surface sheet normal stresses, the outstanding of that method was presented through numeric calculation. The results showed that the model has great potential to become an excellent and highly efficient analysis and design tool for sandwich lattice composite panel to avoid the conventional three-dimension hybrid element model, which usually may lead to the complex program establishment, and the coupling degrees of freedom among the different types of elements. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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20 pages, 10949 KiB  
Article
Compressive Behavior of Bamboo Sheet Twining Tube-Confined Concrete Columns
by Xunyu Cheng, Yang Wei, Yuhan Nie, Gaofei Wang and Guofen Li
Polymers 2021, 13(23), 4124; https://doi.org/10.3390/polym13234124 - 26 Nov 2021
Cited by 11 | Viewed by 1802
Abstract
This study experimentally investigated various axial compressive parameters of a new type of confined concrete, which is termed bamboo sheet twining tube-confined concrete (BSTCC). This new composite structure was composed of an outer bamboo composite tube (BCT) jacket and a concrete core. Under [...] Read more.
This study experimentally investigated various axial compressive parameters of a new type of confined concrete, which is termed bamboo sheet twining tube-confined concrete (BSTCC). This new composite structure was composed of an outer bamboo composite tube (BCT) jacket and a concrete core. Under axial compression, the parameters of thirty-six specimens include concrete strength (i.e., C30 and C50) and BCT thickness (i.e., 6, 12, 18, 24, and 30 layers). The mechanical properties of the BSTCC specimens from the perspective of the failure mode, stress-strain relationship, effect of BCT thickness and dilation behavior were analyzed. The results showed that, in compression, with an increase in BCT thickness in the range of 18-layers of bamboo sheets, the strength increased remarkably. When the strength of the concrete core was high, the confinement effect of the BCT was reduced. In addition, the BCT thickness relieved the dilation of the BSTCC specimens. Finally, the experimental results were compared with predictions obtained from 7 existing FRP-confined concrete models. All the predictions had good agreement with the test results, which further confirmed that the models developed for FRP-confined concrete can provide an acceptable approximation of the ultimate strength of the BSTCC specimens. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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19 pages, 7000 KiB  
Article
Behavior of CFRP-Confined Sand-Based Material Columns under Axial Compression
by Guodong Li, Honglin Liu, Wentao Deng, Hongzhi Wang and Haitian Yan
Polymers 2021, 13(22), 3994; https://doi.org/10.3390/polym13223994 - 19 Nov 2021
Cited by 4 | Viewed by 2094
Abstract
This paper presents an innovative pumpable standing support designed for underground mines located in the arid and semi-arid deserts of the Gobi region with a shortage of water resources. The exterior shell of this pumpable standing support is made of carbon fiber-reinforced polymer [...] Read more.
This paper presents an innovative pumpable standing support designed for underground mines located in the arid and semi-arid deserts of the Gobi region with a shortage of water resources. The exterior shell of this pumpable standing support is made of carbon fiber-reinforced polymer (CFRP), while the infill material is a sand-based material (SBM). As the novel backfill material, SBM is the combination of high-water cementing material and desert sand. A series of experimental tests were conducted to obtain the mechanical response mechanism of this novel pumpable standing support under uniaxial compression. Test variables investigated in this research covered the water-to-powder ratio of the cementing material, the mixing amount of sand, and the thickness of the CFRP tube. Test results confirmed that the CFRP-confined SBM columns exhibited typical strain hardening behavior with the acceptable axial deformation. It was also demonstrated that using high-strength cementing material, a thicker CFRP tube, and a high mixing amount of sand effectively increased the bearing capacity of the CFRP-confined SBM column. Except for the exemplary structural behavior, the consumption of high-water cementing materials of the novel pumpable standing support is smaller than that of its counterparts made of pure cementing material, when specimens with the same mechanical performance are compared. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
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