J. Compos. Sci., Volume 6, Issue 11 (November 2022) – 31 articles

This study assessed polyethene composites produced by rotational moulding with hybrid reinforcement using recycled carbon fibre (RCF) and hemp fibre (HF). First, the RCF was treated with nitric acid to introduce hydroxyl groups on the fibres’ surface and was characterised by infrared spectroscopy and microscopy analyses. Although the fibre surface treatment improved the tensile properties of the composites, the use of grafted maleic anhydride polyethylene (MAPE) as a coupling agent was more effective in improving the interfacial bonding between the fibres and the matrix. Alkali-treated hemp fibres were then used in combination with RCF to produce rotationally moulded composites with an overall fibre content of 10 wt.% but with different ratios of HF/RCF, namely, (20/80) and (50/50). The results showed that the addition of RCF increased the composite’s Young’s modulus compared to neat PE, regardless of the fibre treatment. Similarly, the hybrid composites showed superior Young’s moduli than the HF–PE composites through the increase in the RCF content. It was also observed that adding RCF reduced the void size within the final composites compared to the HF–PE composites, which contributed to the greater performance of the hybrid composites compared to their natural counterparts. Full article

During the impregnation of reinforcement fabrics in liquid composite molding processes, the flow within fiber bundles and the channels between the fiber bundles usually advances at different velocities. This so-called “dual-scale flow” results in void formation inside the composite material and has a negative effect on its mechanical properties. Semi-empirical models can be applied to calculate the extent of the dual-scale flow. In this study, a methodology is presented that stops the impregnation of reinforcement fabrics at different filling levels by using a photo-reactive resin system. By means of optical evaluation, the theoretical calculation models of the dual-scale flow are validated metrologically. The results show increasingly distinct dual-scale flow effects with increasing pressure gradients. The methodology enables the measurability of microscopic differences in flow front progression to validate renowned theoretical models and compare simulations to measurements of applied injection processes. Full article

Wastewater incorporates a wide range of organic toxins, which have an adverse impact on the health of humans and other living things. In recent years, nanotechnology has promoted effective strategies for the photodegradation of industrial organic toxins and tenacious medical contaminants present in wastewater. Advanced composites based on photocatalysts can provide promising solutions for environmental cleanup without generating hazardous byproducts, because they promote the complete oxidation of contaminants. This survey article recaps the essentials of heterogeneous catalysis. Among the major players in heterogeneous catalysis, the metal oxide catalyst (e.g., TiO₂) groups cover photocatalysis of water toxins such as dyes, harmful organic molecules, and pharmaceutical contamination. The reasons for the proposal of TiO₂ as an active filler for heterogeneous photocatalysts include its superior surface area, significant activity for distinct oxidation and reduction reactions at low temperatures and pressures, effective interaction with metal supports, and chemical stability. Because of the aforementioned features, heterogeneous TiO₂ catalysts have a lot of potential in photocatalyst applications, and they can be improved even further by doping them with anionic or cationic dopants. Full article

This paper presents a technology for applying copper and silver films to cotton fabrics by combining photochemical and chemical methods for the reduction of the compounds of these metals. The resulting metal-containing films have inherent electrical conductivity of metals. All the main processes described in the work were carried out by means of the compounds being sorbed by the surface of the fabric when they were wetted in appropriate solutions. The aim of the work was to study the application of electrically conductive composite copper films on cotton fabrics. The tasks to achieve this aim were to perform scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis to confirm that as a result of the experiment, CuCl with a semiconductor ability was formed on the surface of the sample. The driving force behind the photochemical reduction of copper and silver halides on cotton surfaces is that, as a result of the photooxidation of cellulose molecules in the fabric, copper monochloride is first formed on the cotton surface. Subsequently, the process of obtaining silver particles based on semiconductor silver chloride obtained as a result of the transformation of copper monochloride was carried out. The physicochemical and photochemical processes leading to the formation of monovalent copper chloride, which provides sufficient adhesion to the substrate, are considered. It is shown that in this case, the oxidation of monovalent copper also occurs with the formation of soluble salts that are easily removed by washing. Since the proposed technology does not require special equipment, and the chemical reagents used are not scarce, it can be used to apply bactericidal silver films to various household items and medical applications in ordinary laundries or at home. This article examines an affordable and simple technology for producing metal films on a cotton surface due to the presence of disadvantages (time duration, high temperature, scarce reagents, special installations, etc.) of a number of well-known methods in the production of chemical coatings. Full article

The modern construction revolution throughout the past two decades has brought the need for ground vibration mitigation, and this has been one of the major study areas. These studies were mainly focused on the effect of forestation on vibration reduction as the available natural metamaterial. Physical methods such as the finite element method and the boundary conditions of 2D and 3D applications in ground vibration reduction have been developed. Many researchers, scientists, and organizations in this field have emphasized the importance of these methods theoretically and numerically. This paper presents the historical context of resonant metamaterials (MMs), the current progress of periodic 2D and 3D structures, and the possible future outcomes from the seismic metamaterials (SMs), and it relates them with their elastic counterparts to the natural metamaterial (NMs). The idea of bandgaps (FBGs) in the frequency range of interest is reviewed and discussed in some detail. Moreover, the attenuation associated with ground vibrations, noise, seismology, and the like is explained by managing the peculiar mechanisms of ground vibrations. However, a comprehensive computational review focuses on shielding MMs for ground vibration mitigation in urban areas. This phenomenon led to unique features for various techniques to control the bandgap width for various construction applications. Ecological solutions involve the creation of an economic, environmentally based seismic shield for both the Bragg scattering and the local resonance bandgaps. Reportedly, additive studies based on numerical simulation and experiments have improved the functionality of the 2D and 3D periodic structures. It was found that the mechanical properties differ (i.e., stiffness, Poisson’s ratio, and bulk density) and that the geometrical parameters (i.e., lattice, model dimensions, distance from vibration sources, and number of periodic structures) exhibited strong effects on the width and location of the derived FBGs. The geometrical properties of the used unit cell have a strong effect on the attenuation mechanism. Although deep analysis was created in much of the previous research, it was revealed, based on that research, that the attenuation mechanism is still unclear. However, this review article presents a detailed exposition of the recent research progress of the seismic metamaterials, including 2D, 3D, and the main mechanisms of the theoretical backgrounds of energy attenuation. It also summarizes the effects of the factors on the width and location of the bandgaps at a low frequency. In addition, the natural metamaterials and the study of the urban environment are surveyed. The major findings of this review involve the effectiveness of NMs for different functionalities in ground vibration attenuation, which leads to diverse purposes and applications and proposes a roadmap for developing natural materials for clean and quiet environments. Full article

A sparsely cross-linked copolymer was synthesized, and was composed of acrylic acid, acrylamide, and starch. Swelling of the copolymer in an aqueous solution resulted in the formation of hydrogel particles; this formulation was used as a partially biodegradable soil conditioner. The hydrogel was characterized with the following main conclusions: (a) the degree of copolymer swelling increases from 300 to 550 when altering the pH of the solution from 3 to 9. (b) After mixing with sand and soil, the degree of swelling decreases because of restricted volumes of sand/soil-filled containers and a mechanical resistance from the sand/soil particles. (c) Initial sand and soil additions demonstrate unsatisfactory water-retaining properties; the addition of the hydrogel significantly increases the maximum water capacity, while a substantial part of the water in the hydrogel remains available to plants. (d) Upon deposition of the hydrogel formulation over sand/soil and drying out, a protective coating forms on the surface, composed of hydrogel and sand/soil particles, resistant to wind and water erosion. (e) The starch-containing hydrogel is non-toxic towards bacterial and fungal microorganisms; the latter can utilize the microgel in order to support their own development. The results of the work indicate that cross-linked anionic copolymers are promising for use as combined soil conditioners. Full article

Here, we discuss a model for the quasi-static magnetoelectric (ME) interaction in three-layer composites consisting of a single piezoelectric (PE) layer and two magnetostrictive (MS) layers with positive and negative magnetostriction. Two types of layer arrangements are considered: Type 1: a sandwich structure with the PE layer between the two MS layers and Type 2: the two MS layers form the adjacent layers. Expressions for the ME response are obtained using the system of equations of elasto- and electrostatics for the PE and MS phases. The contributions from longitudinal and bending vibrations to the net ME response are considered. The theory is applied for trilayers consisting of lead zirconate titanate (PZT), nickel for negative magnetostriction, and Metglas for positive magnetostriction. Estimates of the dependence of the strength of the ME response on the thickness of the three layers are provided. It is shown that the asymmetric three-layer structures of both types lead to an increase in the strength of ME interactions by almost an order of magnitude compared to a two-layer piezoelectric-magnetostrictive structure. The model predicts a much stronger ME response in Type 2 structures than in Type 1. The theory discussed here is of importance for designing composites for applications such as magnetic field sensors, gyrators, and energy harvesters. Full article

This article reports research on the development and implementation of new methods for structurally integrated and recyclable polymer based electronic products via multi-head fused deposition modelling (FDM) 3D printing. The focus of this research is to propose an efficient FDM-3D printing process utilising multiple filaments with no interruption of the process to ensure the multi-material electronic product achieved is structurally integrated. Such research is an attempt towards development of recyclable rigid electronic structures via multi-material 3D printing, i.e., multiple conductive nanomaterial embedded thermoplastic and non-conductive thermoplastic layers (in coil forms, herein). Six radio frequency identification (RFID) tag coil geometries were selected for the study. The thermoplastic polymer used in this research was polylactic acid (PLA), and the conductive filament was carbon black nanoparticle embedded PLA at approx. 21 wt.%. The nozzle and filaments diameters examined were 1.75 mm. A MakerBot Replicator 2X 3D printer was partially disassembled to be equipped with a dual head, for our examinations. The research investigated the major challenges ahead of the proposed development, mainly, on the deteriorating effects on the quality of the integrated product (structural integrity, electric and magnetic properties) induced by the 3D printing process parameters (e.g., temperature). The most efficient nozzle and bed temperatures to prevent visible defects were found to be higher than the supplier’s recommendation, attributed to the uncertainties associated with the multi-material composition, and were found to require 248 and 100 °C for reliable and continued FDM printing, respectively. The measurements on the electric and magnetic properties, using 4-wire resistance and Hall effect method, respectively, were conducted to quantify process induced deteriorating effects, quantitatively. It has been examined whether the multi-material electronic structure can be achieved via uninterrupted (continuous) processing of polymer nanocomposite-based identification systems for recyclability purpose whilst maintaining the electromagnetic properties of it, a promising technology for reducing landfill. Recommendations were identified for best practices behind such development. Full article

This text reports the morphological and textural behavior of the synthesis stages of a CMK-3 carbon type using a silicon matrix of the SBA-15 type calcined at 823 K as a template. During the synthesis, three intermediate materials were obtained because of (i) the addition of sucrose to the SBA-15 template (CCMK3-1st), (ii) the addition of sucrose to the CCMK3-1st material (CCMK3-2nd), and (iii) the carbonization by pyrolysis of the by-product CCMK3-2nd (CCMK3-F). The texture of the above materials was found by analyzing the N₂ adsorption isotherms, applying the classical adsorption theories to obtain the BET-specific surface and the meso- and micropore distributions by the BJH and Dubinin–Astakhov (DA) methods, respectively, in addition to the non-localized density functional theory (NLDFT). Similarly, with high resolution, the samples were analyzed morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally, the adsorption isotherms of CO₂ and CH₄ of the CMK-3 sample were obtained at six different temperatures in the interval of 243 to 303 K to evaluate the behavior of the isosteric enthalpy of adsorption (q_st) and its CO₂:CH₄ ideal selectivity. The final CMK-3 carbon presented two families of micro- and mesopores of 1.5 and 3.2 nm, nanopipe diameters of 3.5 nm, and a specific surface area of 1350 m²/g. It also presented values of 6.0 and 2.4 mmol/g adsorbed CO₂ and CH₄ at 243 K, respectively, and strong intermolecular interactions, with q_st values higher than 22 kJ/mol reflected in high selectivity values for an ideal mixture of CO₂:CH₄ (30:70%). Full article

Sandwich panels are commonly used as structure, based on fiber reinforced composites, with the goal of high flexural stiffness and low mass. It is most common to separate two high performance composite facesheets with a low-density core, generally in the form of a foam or honeycomb. A recent concept has been to replace these traditional core materials with fiber reinforced truss-like structures, with the goal of further reducing mass. A system is described that can radically reduce the amount of tooling required for truss core sandwich panel manufacture. This system, which is a digital manufacturing platform for the extrusion of continuous fiber reinforced commingled glass fiber/PET tow, was developed to demonstrate the rigidization of composites both on, and off, a tool surface. Navtruss core panels were successfully manufactured using this digital manufacturing platform, without conventional tooling, and the resulting through thickness compression moduli and panel shear moduli were within 14.6% and 23% of the values baseline compression molded specimens. Thus, the results suggest that, with further development, complex truss core structures with performance approaching that of compression molded panels can be manufactured with radically reduced tooling requirements from high volume fraction, continuous fiber reinforced thermoplastic matrix composites. Full article

Active packaging based on chitosan (Ch) incorporated with six different natural hydro-alcoholic extracts (HAE) (rosemary, green tea, black tea, ginger, kenaf, and sage) were developed and tested to extend the shelf life of fresh poultry meat. The quality of the meat packaged was assessed through physical-chemical and microbiological characterization over 15 days of refrigerated storage. In vitro antimicrobial activity of pure extracts and films against Gram-positive (B. cereus) and Gram-negative (S. enterica) foodborne bacteria was also addressed. Pure extracts and the films developed showed antimicrobial activity by the diffusion agar method only against the Gram-positive bacteria. Microbial analysis of the meat wrapped with films incorporated with HAE showed a reduction of 3.1–4.5 log CFU/g and 2.5–4.0 log CFU/g on the total viable microorganisms and total coliforms, respectively. Ch + Kenaf and Ch + Sage films presented the highest antimicrobial activity. Regarding the oxidation degradation, as expected, TBARS values increased for all samples over time. However, the meat wrapped in the biocomposites, except for CH + Sage, presented lower secondary oxidation metabolites (reduction of 75–93%) in the content of malonaldehyde. This protection was superior for the meat wrapped with Ch + Rosemary. Active film also showed promising results by retarding the discoloration process and the increase of pH over time. Thus, the biocomposites produced can pose as an alternative technology to enhance the shelf life of fresh poultry meat and maintain its quality. Full article

The purpose of the present study is to offer an optimal model to predict the tensile index of the paper being consumed to make veneer impregnated with different weight ratios of modified starch (from 3.18 to 36.8%) to urea formaldehyde resin (WR) containing different formaldehyde to urea molar ratios (MR, from 1.16:1 to 2.84:1) enriched by different contents of silicon nano-oxide (NC, from 0 to 4%) using multiple linear regression (MLR) and adaptive neuro-fuzzy inference system (ANFIS) and compare the precision of these two models to estimate the response being examined (tensile index). Fourier-transform infrared spectroscopy (FTIR) and transmittance electron microscopy (TEM) were also used to analyze the results. The results of studying the adhesive structure using FTIR analysis showed that as the WR increased to the maximum level and MR increased to the average level (3%), more ether and methylene linkage forms due to cross-linking. TEM analysis also indicated that if an average level of silicon nano-oxide is applied, there will be more cross-linking due to the more uniform distribution and suitable interactions between the adhesive and nanoparticles. The modeling results showed that the ANFIS model estimates have been closer to the actual values compared to the MLR model. It can be concluded that the model offered by ANFIS has a higher potential to predict the tensile index of the paper impregnated with the combined adhesive of UF resin and modified starch. However, the MLR model could not offer a good estimate to predict the response. According to the preferred approach to predict the most effective property of resin coated paper, modelling would be useful to the research community and the results are beneficial in industrial applications without spending more cost and time. Full article

Natural extracellular matrix (ECM) is highly heterogeneous and anisotropic due to the existence of biomacromolecule bundles and pores. Hydrogels have been proposed as ideal carriers for therapeutic cells and drugs in tissue engineering and regenerative medicine. However, most of the homogeneous and isotropic hydrogels cannot fully emulate the hierarchical properties of natural ECM, including the dynamically spatiotemporal distributions of biochemical and biomechanical signals. Biomimetic hierarchical nanocomposite hydrogels have emerged as potential candidates to better recapitulate natural ECM by introducing various nanostructures, such as nanoparticles, nanorods, and nanofibers. Moreover, the nanostructures in nanocomposite hydrogels can be engineered as stimuli-responsive actuators to realize the desirable control of hydrogel properties, thereby manipulating the behaviors of the encapsulated cells upon appropriate external stimuli. In this review, we present a comprehensive summary of the main strategies to construct biomimetic hierarchical nanocomposite hydrogels with an emphasis on the rational design of local hydrogel properties and their stimuli-responsibility. We then highlight cell fate decisions in engineered nanocomposite niches and their recent development and challenges in biomedical applications. Full article

Today, among emerging materials, metal matrix composites, due to their excellent properties, have an increasing demand in the field of aerospace and automotive industries. However, the difficulties associated with the processing of these composites have been a challenge to manufacturing industries due to inhomogeneous mixing of the matrix with the reinforcement, oxidation, and microstructural phase transformation during processing. Hence, in this paper, Ti-6Al-4V reinforced with SiCp has been processed through a specially developed compression molding, followed by vacuum sintering. The main objective of this paper was to determine the favorable vacuum sintering conditions for Ti-6Al-4V reinforced with 15 Wt. % SiCp composites under a different aging temperature (°C), aging time (h), heating rate (°C/min), and cooling rate (°C /min) to improve the process output parameters such as the hardness, surface roughness, and to reduce the porosity using Taguchi’s Design of Experiments. Finally, the response surface methodology and random forest regression have been used to predict the optimum process output parameters. From the extensive experimentation and understanding gained from Taguchi’s Design of Experiments, the response surface methodology and random tree regression approach can be successfully used to predict the hardness, porosity, and surface roughness during the processing of Ti-6Al-4V-SiC_p composites. Full article

Glass-fiber-reinforced polymer (GFRP) is an advanced material that has superior corrosion resistance, a high strength-to-weight ratio, low thermal conductivity, high stiffness, high fatigue strength, and the ability to resist chemical and microbiological compounds. Despite their many advantages compared with traditional materials, GFRP sections exhibit brittle behavior when subjected to severe loading conditions such as earthquakes, which could be overcome by infilling the GFRP sections with concrete. This paper presents the results of an experimental investigation carried out on the cyclic response of a GFRP beam-column infilled with high-volume fly ash engineered cementitious composites (HVFA-ECC) consisting of 60%, 70%, and 80% fly ash as a replacement for cement. Finite element analysis was also conducted using robot structural analysis software, and the results were compared with the experimental results. The mechanical properties of GFRP sections presented are the compressive strength of ECC, the direct tensile strength of ECC determined using a dog-bone-shaped ECC specimen, the hysteresis behavior of the beam-column, and the energy dissipation characteristics. The lateral load-carrying capacity of beam-column GFRP infilled with HVFA-ECC consisting of 60%, 70%, and 80% fly ash was found to be, respectively, 43%, 31%, and 20% higher than the capacity of GFRP beam-columns without any infill. Hence the GFRP sections infilled with HVFA-ECC could be used as lightweight structural components in buildings to be constructed in earthquake-prone areas. Also in the structural components, as 70% of cement could be replaced with fly ash, it can potentially lead to sustainable construction. Full article

There is an increasing demand for food packaging materials that are safe for the environment and human health. Pure polyvinyl alcohol (PVA) film is non-toxic and transparent but has poor UV-light shielding, thermal and moisture resistance, and antibacterial activity. Our previous work prepared and characterized a biofilm derived from PVA and edible Uncaria gambir extract (UG). The film has antibacterial properties and is anti-UV and flexible. However, UG is hydrophilic, making this film have low moisture absorption. To improve these properties, we trialed adding boric acid (BA) and UG into the PVA. This present study aims to characterize pure PVA film and blend films resulting from mixing PVA (10%), BA (0.5%), and UG (1%). It was found that the PVA/UG/BA film presented the best performance in terms of UV light absorption, tensile properties, thermal and moisture resistance, and antibacterial activity. This blend sample absorbs about 98% of the UV light at 400 nm wavelength without significantly sacrificing transparency. These findings indicate that UG and BA could be advantageous in the preparation of moisture and thermal-resistant UV shielding films with low toxicity and high antibacterial properties based on PVA. They were also found to be strong enough for food packaging applications. Full article

This study was conducted to evaluate the effects of adding cinnamon nanoparticles (NPs), Zinc oxide (ZnO) nanoparticles (NPs), and Copper oxide (CuO) NPs on the antibacterial property of a luting and lining glass ionomer cement (GIC) that was used for the cementation of orthodontic bands to the tooth. Cinnamon NPs, ZnO NPs, and CuO NPs were added into a luting and lining GIC in weight percentages of 1%, 2%, and 4%, respectively while a non-modified GIC was considered as the control group. Agar disc diffusion test was applied to assess the antimicrobial property of samples against Streptococcus mutans (S. mutans). The cytotoxicity of the nanoparticles was examined through the MTT assay for gingival fibroblasts. Data showed that GIC containing cinnamon and ZnO NPs displayed a larger inhibition zone diameter and greater antibacterial activity against S. mutans than CuO NPs. Meanwhile, there were no significant differences in the inhibition zone diameter of cinnamon NPs and ZnO NPs. The cytotoxicity assessment revealed the lower cytotoxicity of cinnamon NPs and the higher cytotoxicity of CuO NPs while the cytotoxicity of ZnO NPs was observed to be higher than cinnamon NPs and lower than CuO NPs. GIC containing cinnamon NPs exhibited noticeable antibacterial activity against S. mutans and cinnamon NPs revealed less cytotoxicity and it is can be labeled as a favorable option for further assessment to be applied in fixed orthodontic treatments for the cementation of bands to teeth. Full article

The physicochemical nature of the amino group NH₂’s landing on the basal plane of the graphene and on the edge atoms of the graphene nanomesh was revealed. The mechanism of covalent binding between the NH₂ groups and the carbon atoms of the graphene and the GNM was discovered in silico by the SCC DFTB method. The maximum amount ratio of the amino groups to carbon atoms equaled 4.8% for GNM and 4.6% for the basal plane. The established values of the concentration and the trend of change in the work function of electrons are experimentally confirmed. Full article

Adhesively bonded composite reinforcements have been increasingly used in civil engineering since the 1980s. They depend on the effective transfer of forces throughout the adhesive joint that may be affected by defects or damages. It is therefore necessary to provide methods to detect and/or identify these defects present in the bonded joints without affecting their future use. This should be carried out through nondestructive methods (NDT) and should be able to discriminate the different types of defects that may be encountered. The acousto-ultrasonic technique shows good potential to answer to this challenge, as illustrated in recent studies led on small-scale model samples. In this paper, we assess the robustness of this methodology on larger scale samples using reinforced concrete beams (RC beam), that is a mandatory step prior to on-site applications. A mono-parametric analysis allows the detection of all types of defects using a simple criterion set. For the identification, it was necessary to conduct a data-driven strategy by means of a Principal Component Analysis (PCA) and a random forest (RF) method used from extracted parameters. Full article

Of great importance in materials science is the design of effective functional materials that can be used in various technological fields. Nanomodified materials, which have fundamentally new properties and provide previously unrealized properties, have acquired particular importance. When creating heating elements and materials for deformation measurement, it is necessary to understand the patterns of heat release under conditions of mechanical deformation of the material, as this expands the potential applications of such materials. A study of elastomers modified with multi-walled carbon nanotubes (MWCNTs) has been carried at the MWCNTs concentration of 1–8 wt.%. The modes of heat release of nanomodified elastomers at a voltage of 50 V at different levels of tension are reported. The increment of the MWCNTs concentration to 7 wt.% leads to an increment in the power of heat emissions. It is worth noting the possibility of using the obtained elastomer samples with MNT as sensitive elements of strain sensors, which will allow obtaining information about physical and chemical parameters following the principles of measuring the change in electrical resistance that occurs during stretching and torsion. The changes in conductivity and heat emission under different conditions have been studied in parallel with Raman mapping and infrared thermography. The reported studies allow to make the next step to develop flexible functional materials for the field of electric heating and deformation measurement based on elastic matrices and nanoscale conductive fillers. Full article

Plastic products play a significant role in fulfilling daily necessities, but the non-decomposable nature of plastic leads to inescapable environmental damage. Recycling plastic material is the most appropriate solution to avoid pollution and short product lifespan. The present study shows the recycling effect on carbon nanofiber (CNF) reinforced polypropylene (PP) nanocomposite to attain the purpose of reuse and sustainability. 30 wt% CNF melt-blended with polymer and PP-nanocomposites were fabricated using the injection molding technique. PP-CNF nanocomposites were recycled, and mechanical, thermal, and morphological properties were investigated. Three-point bending and tensile testing showed a low decrement of ~1% and ~5% in bending and tensile strength after recycling 30 wt% PP-CNF nanocomposites. Scanning electron microscopy (SEM) images show that the alignment of CNF was disturbed after recycling due to the decrement in the aspect ratio of CNF. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) showed that the crystallinity of PP increases with recycling. The lowering of interfacial interaction between CNF and PP after recycling was studied by a stress-controlled rheometer. The decrement in mechanical properties of PP-CNF nanocomposite is not significant due to CNF reinforcement; hence, it can be reused for the same or other structural applications. Full article

The ZnO-SnO₂-Fe₂O₃ composites containing flower-like particles were prepared by the non-isothermal polymer-salt method. Thermochemical processes proceeding during composites synthesis was studied by DTA/TG method. The structure and morphology of obtained composites were studied by the SEM and XRD analysis. Prepared composites containing small amounts of SnO₂ and Fe₂O₃ demonstrate the high adsorption and photodecomposition of the organic dye Rhodamine 6G in its solutions. Obtained materials show the ability of the photogeneration of the chemically active singlet oxygen under the visible irradiation. The synergistic effect of the flower structure and Fe₂O₃ doping can significantly improve the photocatalytic and adsorption activities. Full article

The filling stage in injection/infusion moulding processes plays a key role in composite manufacturing that can be influenced by the inlet and vent ports. This will affect the production of void-free parts and the desirable process time. Flow control is usually required in experiments to optimise such a stage; however, numerical simulations can be alternatively used to predict manufacturing-induced deficiencies and potentially remove them in the actual experiments. This study uses ANSYS Fluent software to model flow-front advancement during the impregnation of woven fabrics. A developed technique is applied by creating tracking points (e.g., on-line monitor) in the direction of the flow to report/collect data for flow-front positions as a function of time. The study adopts the FVM-VOF-based two-phase flow model together with an implicit time-stepping scheme, i.e., a dual-time formulation solution method with a preconditioned pseudo-time derivative. Initially, three time-step sizes, 5 s (small), 25 s, and 50 s (large), are evaluated to examine their impact on numerical saturation lines at various fabric porosities, 40%, 50%, and 60%, for a two-dimensional (2D) rectangular mould, and predictions are then compared with the well-known analytical Darcy. This is followed by a three-dimensional (3D) curved mould for a fillet L-shaped structure, wherein the degree-of-curvature of fibre preforms is incorporated using a User-Defined Function (UDF) to tailor the impregnation process. The developed approach shows its validation (1–5.7%) with theoretical calculations and experimental data for 2D and 3D cases, respectively. The results also stress that a shorter computational time can be achieved with a large time-step size while maintaining the same level of accuracy. Full article

Residual stresses in fiber metal laminates (FML) inevitably develop during the manufacturing process. The main contributor to these stresses is the difference in the coefficients of thermal expansion (CTE) between fibers and metal in combination with high process temperatures. To quantify these stresses, the use of specimens with an asymmetric layup is an easily adaptable method. The curvature that develops after the manufacturing of flat laminates with an asymmetrical layer stack is a measure of the level of residual stresses evolving during cure. However, the accuracy of the curvature evaluation is highly dependent on specimen design and other influencing parameters. This leads to deviations when compared to other methods for residual stress quantification as can be seen from the literature. Therefore, in this work a large set of FML specimens is comprehensively investigated to identify relevant influencing parameters and derive conclusions about specimen design and evaluation techniques. For certain layups and process parameters, there is a good correlation between the curvature and the stress-free temperature, which is further covered by analytical solutions for bimetals. This correlation is the basis to transfer curvature into a stress-free temperature that can consequently be used for the quantification of residual stress levels in more complex FMLs. The transfer is validated by in situ strain measurements during cure using a strain gauge technique. Based on the results, the application of asymmetric specimens for residual stress characterization in more complex laminates is presented in the form of a workflow. The work shows the basic considerations and procedures necessary to use asymmetric specimens for residual stress quantification in FML. Furthermore, the results obtained can also be transferred to other composite materials. Full article

This work investigated the (0002) textured ZnO films without and with the addition of an Au continuous top layer and its effects on their surface wettability and plasmonic resonance characteristics. The ZnO films were directly fabricated onto glass substrates at the synthesized temperature of 300 °C via a plasma-enhanced chemical vapor deposition (PECVD) system, and the as-synthesized ZnO film exhibited an average optical transmittance value of 85%. The ultraviolet (UV) light irradiation can be applied to enhance the hydrophilicity, changing it from a hydrophobic status to hydrophilic status due to the existing and adjustable characteristics of the photocatalytic activity. On the other hand, the surface wetting/contact angle (CA) value of the ZnO film with a controllable surface wettability switched from 94° (hydrophobicity) to 44° (hydrophilicity), after it was exposed to UV light irradiation for 5 min, and stably reversed back to hydrophobicity (92°) via a post-annealed treatment using rapid thermal annealing (RTA) at 350 °C for 5 min in air. A fast, simple, and reversible method for switching between hydrophilic and hydrophobic status is claimed in this present work. The improved surface plasmonic resonance is owning to the coupled electron and photon oscillations that can be obtained and produced at the interface between the flat Au layer and ZnO (metal/metallic oxide) heterostructured films for future applications of various wide-bandgap compound semiconductors. Full article

Titanium dioxide nanotubes (TNTs) were fabricated via electrochemical anodization process. Photocatalytic hydrogen generation from formic acid solution was investigated using TNTs with simultaneous Rh deposition. The effects of calcination temperature and time for TNTs on hydrogen generation were studied. The maximum hydrogen generation (54 µmol) was observed when using TNTs with a 500 °C calcination temperature and 10 h calcination time under 5 h of black light (352 nm) irradiation. The reusability tests indicated that the TNTs with photodeposited Rh metal (Rh/TNT) had excellent stability up to the fifth cycle for hydrogen generation from formic acid solution. The TNTs were characterized before and after photodeposition of Rh metal via X-ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and diffuse reflectance spectroscopy (DRS). XRD revealed the presence of optimal anatase–rutile phase ratios in TNTs at 500 °C and 300 °C calcination temperatures. XRD and SEM revealed the deposition of Rh metal on the TNT surface at 300 °C and 500 °C calcination temperatures. It was observed that the light absorption ability of TNTs calcined at 500 °C was greater than that of TNTs calcined at 300 °C. The reaction mechanisms for the formation of TNTs and photocatalytic hydrogen production from formic acid solutions by TNTs with simultaneous Rh deposition were also proposed. Full article

The results of the synthesis of PAN/NiO composite fibers by the electrospinning method are presented. The electrospinning installation included a rotating drum collector for collecting fibers. Nickel oxide nanoparticles were synthesized by solution combustion synthesis from nickel nitrate and urea. It was shown that monophase NiO nanoparticles with average particle sizes of 154 nm could be synthesized by this method. NiO nanoparticles were investigated by X-ray diffraction analysis and scanning electron microscopy. Based on NiO nanoparticles, composite PAN/NiO fibers were obtained by electrospinning. The obtained composite fibers were modified with heat treatment (stabilization and carbonization) processes. Obtained C/NiO fibers were investigated by SEM, and EDAX. It was shown that obtained composite fibers could be used for the detection of acetone and acetylene in air. These results show that C/NiO based electrospun fibers have potential applications in gas sensors. Full article

The effect of adhesive layers bonding to the core of functionally graded (FG) surface layers is investigated using the free vibration of a five-layer sandwich composite plate resting on a Winkler elastic foundation in a thermal environment. It is assumed that all layers are experiencing a steady-state temperature ΔT. The layer-wise theory is used to derive the governing equations with the help of Hamilton’s principle. The Navier solution is employed to obtain the closed-form solutions. The numerical results obtained using the present theory are compared with three-dimensional finite elements implemented by ABAQUS software. The results show that the proposed theory is not only accurate but also efficient in predicting the natural frequencies of sandwich plates resting on Winkler foundations. Full article

In this paper, two typical examples are used to illustrate the weak position of aircraft structure in the process of vibration. Through the modal analysis of the typical composite plate and I-shaped beam, the first 20-order modal strain energy of the plate is extracted, which is difficult to locate the weak spot due to the highly scattered location of the higher modal strain energy. The modal participation factor is introduced as the weight factor of the summation of the modal strain energy. The modal participation factor is large, the weighting factor is large, and the high modal strain energy of the composite plate moves diagonally in the 45° direction of the composite plate and the high strain energy region is consistent with the previous modes of the plate. This is the result of the weak in-plane shear stiffness of the composite panel, which shows the effectiveness of the mode weighted summation method. The I-shaped composite beam uses the modal strain energy summation of the weight factor, and the higher modal strain energy is concentrated on the middle part of the beam and at 1/4 and 3/4 of it. Therefore, the weak part of the vibration can be clearly identified. The higher modal strain energy is extracted by the method proposed to this paper, which can be used as a reference to structural design and dynamic on-line monitoring. Full article

High performance lightweight structures made of metal matrix composites (MMCs) are in demand for application in variety of industries such as aircraft, spacecraft, automobile, marine, sports equipment, etc. However, uniform distribution of the reinforcement phase to improve the mechanical properties and quality of MMCs has been the challenge for the manufacturing industries. Hence, researchers are focusing on the development of traditional low-cost method of producing metal matrix composites. In the view of above facts, an attempt is made to study the processing and characterization of Si-Al alloy reinforced with zirconium dioxide particulate composites in this paper. Hence, this paper concentrates on experimentally identifying the effect of stir cast and spray forming processing techniques followed by hot pressing on micro hardness, compressive strength, and tensile strength using Taguchi’s design of experiments for aluminum silicon matrix alloy reinforced with zirconium dioxide particulates. From the extensive experimentation on aluminum and silicon reinforced with the ZrO₂ powder particulates, it was observed that there was an improvement in selected mechanical properties as the percentage of ZrO₂ increased with 13 wt.% of silicon under spray forming processing technique compared to stir cast composites. This may be due to uniform distribution homogenous dispersion, larger work hardening rate, and structure of dislocation tangles around the ZrO₂ particulates that occurred during spray forming processing technique. Further, results obtained from the interaction plot, contour plot, main effects plot, and analysis of variance (ANOVA) proved to be successful for identifying the optimum processing parameters for Si-Al alloy reinforced with zirconium dioxide particulate composites. Further, this paper also discusses wear study using pin on disc wear testing apparatus on spray forming processed aluminum and silicon (13.0 wt.%) alloy reinforced with the ZrO₂ powder particulates based on Taguchi’s design of experiments followed by second order model generation for wear using response surface methodology. Finally, electrode wear study of spray forming processed aluminum and silicon alloy reinforced with the ZrO₂ powder particulates using electric discharge machining by varying peak current (A), pulse on time (μs), and pulse off time (μs) using brass, copper, and graphite as electrode material based on L₂₇orthogonal array. The understanding gained from the design of experiments in this paper can be used to develop future guidelines for processing and characterization of Si-Al alloy reinforced with zirconium dioxide particulate composites. Full article