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This study investigates the effects of incorporating glass microspheres (GMSs) as fillers in carbon fabric–epoxy composites (CFECs) on their degradation behavior under environmental conditions such as moisture and ultraviolet rays. The GMS-filled composites were subjected to accelerated ageing and evaluated using dynamic mechanical analysis (DMA), the Charpy impact test, and inter-laminar shear strength (ILSS) tests. The results indicate that the addition of GMS fillers significantly improves the stiffness and viscoelastic behavior of the composites. However, the impact strength of the composites decreases with the addition of GMS fillers and accelerated ageing. The ILSS results demonstrate that the addition of GMS fillers improved the interfacial bonding between the carbon–epoxy matrix and fillers. This study provides insights into the mechanical properties of GMS-filled carbon–epoxy composites.

This paper reviews the shape distortions in a polymer composite, its sources, characterization techniques, and remedies. The shape distortion may include warpage, spring-in, or change in enclosed diameter for flat, angled, and circular parts. Residual stresses are considered to be the major source of shape distortion (dimensional instability) in laminated composites. These stresses are the result of the difference in thermal expansion behavior of the different plies or between matrix and reinforcement. Additionally, fiber buckling, transversal cracking, and delamination are also produced in the composite, affecting its mechanical properties like tensile, flexural, and compression. The produced residual stresses are determined through different techniques like layer removal of symmetrical laminates, first ply failure, and x-ray diffraction. The common remedies for shape distortion reported in the literature include nanoparticle addition and variable thickness at the base or flanges.

Continuous fiber-reinforced thermoplastic composites having superior mechanical properties are preferred for lightweight architectures. Rising demands for enhanced mechanical performance under certain types of loadings have focused researchers toward the hybridization of composite materials. In this study carbon and aramid fibers were employed to produce hybrid fabrics by weaving in two different woven architectures, 1/1 plain and 2/1 twill. Polyvinyl butyral (PVB) matrix was reinforced with these woven fabrics and hybrid composites were fabricated by compression molding. Un-hybrid carbon and aramid composites were fabricated using PVB matrix, as control samples. Tensile characteristics of hybrid composites offered intermediate strain at failures of 0.5% due to the combined rigid and ductile natures of carbon and aramid, respectively. Flexural strength and absorbed impact energy (200 MPa and 97 kJ/m 2 ) were higher for hybrid composites, and quick elastic recoveries were experienced in hybrid composites after impact. Plain woven reinforced hybridization had about 25% and 5% lower tensile and flexural characteristics respectively, as more interlocking zones of warp and weft yarns reduced strength. However, these interlocking zones positively contributed to impact performance by 11.5% higher energy absorption.

The objective of this study is to establish a conceptual framework for fiber-reinforced polymer composite (FRPC) panels designed for structural purposes through the incorporation of a third phase (fillers). The present investigation was aimed to design and fabricate 3-phase polymer composite panels that offer enhanced thermal insulation and strength while maintaining low material and labor expenses. Two types of fibrous reinforcements (jute fabric and glass fabric) of different origins were used as reinforcement; polypropylene (PP) was used as the matrix, and microcrystalline cellulose (MCC) was used as particle reinforcement material. The composite materials were fabricated with different MCC concentrations (0, 2 wt%, and 4 wt%), using a hot compression molding technique. It was found that MCC helped to enhance the mechanical performance of the composite panels, while the thermal conductivity showed a slight reduction due to lower concentrations of MCC used. For polypropylene/glass (PPG) composites, thermal conductivity was reduced from 0.214 to 0.193 W/m·K by the addition of 4% MCC fillers. Similarly, for polypropylene/jute (PPJ) composites, it was reduced from 0.14 to 0.126 W/m·K by 4% MCC fillers. The Charpy impact strength of both PPG and PPJ composites was enhanced by the addition of fillers, and the effect was more significant in the case of PPG (increased from 24.83 to 43.98 kJ/m2 for 4% fillers). Cost analysis of the composite panels was also done, showing PPJ panels to be slightly cheaper as compared to PPG. The findings indicate that the developed composite panels have the potential to serve as partitioning as well as the outer shield of the building due to their effective thermal and mechanical properties.

Dual-core yarns, containing two filaments within the core of the yarn, have gained increasing commercial and research interest recently, especially in denim manufacturing. The use of multi-components in dual-core yarns allows for tailoring the properties of the yarn and denim fabric. The type of filaments and fibers and their surface characteristics play a role in fiber-to-fiber cohesion within yarn structure. However, little has been reported regarding the effect of different filaments on the properties of dual-core yarns. The objective of this study was to investigate the effect of three different filaments, T400, polyester flat (PET flat) and polyester textured (PET textured) as well as two yarn structures, siro versus non-siro, on tensile, elastic and other properties of dual-core yarns at same twist level and linear density of the yarn. The results showed that the siro spun dual-core yarn containing T400 exhibited 25% higher tenacity compared with yarns containing other filaments. However, the plastic deformation of the yarn containing PET flat filament, having a higher initial modulus, was at a relatively lower level compared with T400 and PET textured. Overall, the siro yarn structure showed lower imperfections and higher tenacity compared with the non-siro yarn structure. The dual-core yarn containing T400 showed a higher level of moisture wicking compared with other filaments which can add to the comfort properties but a similar hairiness level. The findings of this study suggest that the use of a filament with a higher initial modulus can improve the stretch and recovery behavior of the dual-core yarns.

The growing world population and urge of the improved living standard has increased the demand of materials leading to higher post-consumer waste. This paper investigates the potential of using plant waste (yard cutting) as reinforcement for composite materials, which is either landfilled or burnt. The yard cutting of a creeper plant, Argyreia speciose (local name Tezgam) plant was used for fiber extraction, by water retting. The extracted fibers were treated with an alkali solution and then converted to powder (particle) form by ball milling. The particles obtained, after milling, were used as a reinforcement to fabricate composite material along with jute fabric obtained from waste packing bags. The mechanical properties (tensile, flexural, and impact) of these waste material hybrid composites were investigated. It was found that the filler reinforced composites exhibited higher strength as compared to the others. The addition of fillers also enhanced the modulus of the material, both in tensile and 3-point bending mode. These fillers loaded composites were also able to withstand the maximum force for a longer period during the drop weight impact test. Hence, agricultural waste can be effectively used to develop a value-added product with enhanced performance properties.

Cellulose is the most abundant substance existing in the form of plants on the earth. These fibers are obtained either directly or indirectly from the seed, leaves, stem, or wood of plants. Cellulosic fibers are preferred for apparels owing to their abundance, ease of processing, biodegradation, and compatible with the human body in terms of better moisture management, thermal regulation, and tactile comfort. In this study, woven fabric made of four different cellulosic yarns, i.e. cotton, bamboo, tencel, and viscose were produced, and their thermo-physiological comfort properties were compared. The linear density of yarns, and thread density and weave structure (3/1 twill) of all the fabrics were kept constant on the weaving machine. Air permeability, thermal resistance, and moisture management tests were carried out to analyze their thermo-physiological comfort properties. The results showed that cotton fabric showed higher air permeability and thermal resistance as compared to other cellulosic fabrics. Whereas the moisture management properties of tencel fabric were superior to the rest of cellulosic fabrics. Moreover, the effect of cellulosic materials on air permeability and moisture management properties of the woven fabrics was found statistically significant.

This research offered an experimental examination of the effect of binder yarns, and 3D woven patterns on impact (Charpy and drop weight impact), and compression after impact (CAI) performance of seven (07) different kinds of 3D woven jute/green epoxy composites. Along with four (04) typical classifications of 3D woven reinforcements i.e., OLL, OTT, ALL, ATT, and three (03) novel (hybrid) 3D reinforcements i.e., H1 (OTT and ATT interlocking pattern), H2 (OTT and ALL interlocking pattern), H3 (OLL warp and weft interlocks “bidirectional”) were also developed on dobby weaving machine. OTT composite displayed the highest amount of impact strength during Charpy impact in both in-plane directions i.e., warp and weft in comparison with others due to the existence of the truly vertical binder yarns which is comparable with H1. While ALL sample exhibited the highest value of maximum load, work done, and energy absorbed during the 3 J and 6 J drop weight impact energies which is nearest comparable with hybrid 3 (H3) composite. H3 composite sample revealed the highest value of compression after impact (CAI) stress and modulus in both energy levels due to the presence of both warp and weft binder yarns in a single 3D structure.

Availability, simplicity of processing, biodegradability, sustainability, and compatibility with human skin in terms of moisture management and temperature regulation, cellulosic fibers are preferred for clothing. In this study four (04) different cellulosic yarns (cotton, bamboo, viscose, and tencel) and two weave designs (1/1 plain and 2/2 warp rib) were used to develop eight (08) woven fabrics with equal thread densities, and their volume porosity %, air permeability, thermal resistance, water vapor permeability index, and moisture management properties were compared. The results showed that tencel fabrics showed the highest water vapor permeability index and overall moisture management capability (OMMC) values, whereas cotton fabrics had the highest values of volume porosity %, air permeability, and thermal resistance. Furthermore, the 2/2 warp rib weave design showed higher values of volume porosity %, air permeability, and thermal resistance in comparison with 1/1 plain woven fabrics, while the water vapor permeability index and OMMC values were higher in 1/1 plain woven fabrics. Moreover, the statistical significance of both factors (cellulose material and weave design) on different results was also analyzed.

Carbon fiber-reinforced composite (CFRC) is a well-known hi-tech material with diverse applications. The CFRC faces several environmental conditions during its application, e.g., elevated temperatures, humidity, exposure to UV radiation, and acidic and alkaline environments. These environmental factors strongly affect the performance of CFRC, and they tend to age with time. Aging reduces the mechanical properties of the composite and ultimately its service life. In this review, the focus is on the aging of composite, common types of aging (thermal, hydrothermal acid and alkaline, and UV radiation), and the role of the third phase (fillers) in the aging process. There are numerous factors involved in the aging of composite. Aging starts with microcracks and proceeds towards delamination which further exposes the internal surface to environments. When the depths are exposed, free radicals are released and further deteriorate the internal structures. They create more pathways for oxygen to reach every millimeter of composite, thus reducing the mechanical performance of the composite. Usually, a trend is seen that introducing filler might slow down or compensate for the mechanical performance after aging. This trend is explored in the review article. However, usually, the third phase remained neutral and sometimes reduced and/or enhanced the mechanical properties after aging. In thermal aging, different metallic oxides have a noteworthy effect on mechanical performance. The synergistic effect of the third phase and aging on CFRC mechanical performance is also tabulated.

A sustainable approach to composites is leading to the use of natural fibers rather than synthetic materials, like carbon or glass, for reinforcement. However, the higher moisture absorption of natural fibers impairs the composite’s mechanical properties. Therefore, to improve the mechanical properties, some chemical treatments like silane and fluorocarbon can be performed to reduce the moisture absorption of natural fibers. In this study, flax was used as reinforcement, and epoxy was used as a matrix. In the first part of the study, flax reinforcement was treated with different concentrations of silane (20, 40, and 60 g/L) and fluorocarbons (80, 100, and 120 g/L). Moisture regains (MRs), absorbency, and tensile strength were measured at reinforcement levels. According to the results, reinforcements treated with 60 g/L silane (S3) and 120 g/L fluorocarbons (F3) exhibited the lowest MR values of 7.09% and 3.06%, respectively, whereas water absorbency was significantly reduced. The sample treated with 120 g/L fluorocarbons required 300 seconds extra time to absorb the water as compared with the untreated sample, whereas samples S3 and F3 showed an increase in tensile strength by 20.16% and 34.80% when compared with untreated reinforcement flax reinforcement. In the second part of the study, untreated and treated flax reinforcements were combined with an epoxy matrix for composite fabrication. MR and mechanical tests (tensile, flexural, and Charpy impact tests) were performed. Results revealed that treated flax-reinforced composites exhibited lower MR values 0.86% for F3 and 0.42% for S3, respectively. The tensile, flexural, and pendulum impact strengths of silane-treated reinforced composite sample C.S3 were increased by 15.07%, 117%, and 20.01%, respectively, compared with untreated reinforced composite samples. Consequently, both chemical treatments improve composite mechanical performance as well as service life.

This study investigates the influence of silane-treated aluminum hydroxide on the mechanical performance of flame-retardant composites. These composites have potential applications for luggage bags, as a replacement for conventional plastics, offering more durability and lighter weight. Glass fabric was used as the reinforcement, while epoxy was used as the matrix material. To impart flame retardancy, aluminum hydroxide nanoparticles were used as fillers in different weight % age (5%, 10% and 15%). As these are inorganic particles and have compatibility issues with the matrix material, silane-coupling agents (Dynasylan® 6490 and Dynasylan Glymo) were used to treat these filler particles. Both the silane-coupling agents fraction used for treatment and the fillers fraction added to the composites were varied to determine the most optimum combination. The mechanical properties of the developed composites such as tensile, flexural, and short beam shear strength were investigated. The best results were exhibited by 10% aluminum hydroxide fillers treated with 1% (by weight) coupling agent (Dynasylan Glymo).

Smart auxetic structures are gaining attention in various areas such as architecture, clothing (sports and protective), civil, and medical applications owing to their negative Poisson’s ratio. Compared to ordinary structures, these structures have better properties (shear resistance, formability, energy absorbance, and robust fracture strength). Auxetic structures show the exceptional property of becoming wider in one direction when stretched from another direction. In this research, three different auxetic weft-knitted structures were fabricated using nylon, polyester, acrylic, and cotton yarns on a Shima Seiki flat-knitting machine. The physical properties, negative Poisson’s ratio, and thermo-physiological comfort properties of these fabrics were checked. Negative Poisson’s ratio strain curves of the developed fabrics were plotted; all fabrics, except for nylon, show the negative Poisson’s ratio (NPR). The NPR decreases with increased strain in the longitudinal direction, and polyester exhibits a maximum value of NPR −0.4 in line structure at 30 mm extension. Results also revealed that structures made with nylon and polyester yarns exhibit a better value of air permeability than acrylic and cotton, while acrylic provides the best thermal resistance values than other materials in line structure and polyester yarn shows better overall moisture management capacity (OMMC) performance in zigzag structures.

The inherently brittle nature and the susceptibility to impact damage hinder the use of carbon/epoxy composite in some areas. In this study, poly ether ether ketone (PEEK) microparticles were incorporated to increase the resistance to delamination and interlaminar fracture toughness. A hand lay-up technique followed by compression molding was used to fabricate composite. The influence of PEEK particles was evaluated by tensile, flexural, short beam shear (SBS), compression, and Charpy impact test. The Barcol hardness, density, fiber volume fraction, and void content were also determined. According to the result, a maximum improvement in the tensile and flexural strength was observed for 2% incorporation of PEEK particles. However, there is downturn found in the flexural modulus. Moreover, a notable increment in the matrix-dominated properties (short beam shear, compression, and Charpy impact strength) was found with the addition of the PEEK particles.

In aerospace and automotive applications, composite materials are used as a major structural material along with metals. Composite-metal and metal-metal joining are very crucial in such structures. Adhesive bonding is commonly used for this purpose. Since such structures are exposed to varying temperatures and dynamic loads, it is essential to investigate the response of such joints under thermomechanical loading. Though various studies have been reported in the literature to assess the thermomechanical properties of composites, adhesives, and their joints, the effect of the surface treatment of metals and composites on the improvement in the thermomechanical behavior of the joints has not been reported. The metal and composite surfaces were modified using chemical etching techniques. The interaction between adhesives and adherends was studied using the DTMA technique in compression mode. Anodizing treatment on aluminum alloys improved the stiffness properties of metallic joints to 36% and decreased the damping to 23%, while chemical treatment on composite and metal adherends increased the stiffness of composite-metal joints to 34% and reduced the energy dissipation to 20%.

"Fibre-Reinforced Polymer Composites: Mechanical Properties and Applications" is a newly open Special Issue of Polymers, which aims to publish original and review papers on new scientific and applied research and make boundless contributions to the finding and understanding of the reinforcing effects of various synthetic and natural fibres on the performance of biopolymer composites [...]

The study was conducted to investigate the effect of cotton woven fabric pore size on its mechanical and comfort properties. Using 20/1 Ne cotton yarn, 10 fabrics with varying pore size were produced in plain weave for this study. In order to get variable pore sizes, the thread density was changed along warp and weft direction, keeping the linear density of yarn as constant. It was observed that with increase in pore size, air permeability as well as moisture management increased but the thermal resistance decreased. In general, the comfort properties of cotton fabrics were improved with a higher pore size but for applications requiring heat retention, the fabrics having smaller pore sizes must be preferred. It was further observed that the mechanical properties of cotton fabrics do not depend directly on the pore size, rather they depend on the number of threads, in a particular direction. The number of threads may be controlled to get desired pore size and ultimately the desired properties.

The particle loaded composites are being used widely for tailored properties, however, the particles tend to create concentration gradient along part length during infusion. Keeping in view the limitations of existing characterisation approaches, thermal expansion coefficient (CTE) is used as a macroscopic tool to measure particle filtration for the first time. Composite plates were fabricated by VIM (Vacuum Infusion Moulding) process from glass woven fabric and vinyl ester resin containing silica microparticles (0, 0.5, 1.0, 1.5, and 2.0%). CTE was determined at different positions from composite samples. It was found that the CTE was low at the inlet indicating a high particle concentration. A gradual decrease in the particle concentration was observed from the inlet towards the outlet. The variation of CTE due to the gradient of particle concentration was validated using COMSOL Multiphysics®. Both the experimental and numerical results show a similar global trend, i.e. CTE is decreasing with increase in the particle concentration. Hence the CTE can be effectively used as a qualitative tool for the measurement of particle filtration in the composite part produced by vacuum infusion.

In this study, we developed multifunctional and durable textile sensors. The fabrics were coated with metal in two steps. At first, pretreatment of fabric was performed, and then copper and silver particles were coated by the chemical reduction method. Hence, the absorbance/adherence of metal was confirmed by the deposition of particles on microfibers. The particles filled the micro spaces between the fibers and made the continuous network to facilitate the electrical conduction. Secondly, further electroplating of the metal was performed to make the compact layer on the particle- coated fabric. The fabrics were analyzed against electrical resistivity and electromagnetic shielding over the frequency range of 200 MHz to 1500 MHz. The presence of metal coating was confirmed from the surface microstructure of coated fabric samples examined by scanning electron microscopy, EDS, and XRD tests. For optimized plating parameters, the minimum surface resistivity of 67 Ω, EMI shielding of 66 dB and Ohmic heating of 118 °C at 10 V was observed. It was found that EMI SH was increased with an increase in the deposition rate of the metal. Furthermore, towards the end, the durability of conductive textiles was observed against severe washing. It was observed that even after severe washing there was an insignificant increase in electrical resistivity and good retention of the metal coating, as was also proven with SEM images.

The yarn structure and fabric interlacing pattern are determining parameters for fabric properties. The current study focusses on the multi-response optimization of certain fabric properties like shrinkage, areal density, thickness, flexural rigidity, and bending modulus using principal component analysis for optimum properties. Yarn twist (four different levels), fabric weave design (plain and twill), and yarn type (carded and combed) were the variables of the study. The Taguchi approach of the orthogonal array was sued for designing the experiments, and eight different samples were produced. The yarn twist and fabric weave design were found to have significant effect on these properties of the fabric. Furthermore, using analysis of the variance method, contribution% of parameters to these properties was determined.