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Polymer matrix syntactic foams have received a lot of interest in recent years because of their advantages, such as their lightweight and energy-absorbing properties. The purpose of this study is to produce representative elementary volume of syntactic foams with a random filling of hollow glass microspheres from neat epoxy to 0.4 v/v filling in epoxy resin. Different forms of syntactic foams have been evaluated. ANSYS software (2020, R1) was used to investigate the numerical results. The impact of the microsphere volume fraction on the elastic mechanical properties of syntactic foams was investigated. The relative modulus, density and Poisson's ratio values of foams fall as the microsphere volume fraction rises but specific modulus values of composites increases, confirming that the weight of a component can be reduced. The relative modulus, Poisson's ratio and density of syntactic foam decreases with increasing volume fraction of microballoon, dropping to approximately 4.5, 8.9 and 30 percent respectively at 0.4 volume fraction compared to neat epoxy. Parameters for beam and plate design ensuring that with same bending and axial stiffness for beam and bending stiffness for plate, weight of a component could well be reduced. As a consequence, utilizing syntactic foams in structural applications may result in significant weight reductions. [ABSTRACT FROM AUTHOR]

The tensile characteristics of a novel TWARMAT hybrid fabric with a weight of 600 g/m2, comprising aramid and E-glass fibers were assessed. Additionally, a conventional 205-g/m2 plain glass and 160-g/m2 plain carbon fiber fabrics were also tested for comparison. The results obtained reveal that TWARMAT exhibited superior stiffness and density ratios. To confirm these experimental results, the rule of mixtures was utilized. The close agreement between the two sets of data, with mean relative errors of 5.5 and 1.05% for Young's modulus and density respectively, confirms the reliability of the methods applied. [ABSTRACT FROM AUTHOR]

The Aqueous environment impairs the mechanical performance of carbon fiber‐reinforced polymers (CFRPs) and decreases the durability of engineering structures made of CFRPs primarily by degrading the resin matrix. Hence, the objective of this study is to investigate and accurately predict the influence of hydrothermal aging on the epoxy and its carbon fiber reinforced polymer (CFRP). Particularly, this work developed a modeling method that combined Fick's model, empirical aging model and elastoplastic constitutive model to predict the mechanical behavior of hydrothermally aged epoxy matrix. After the experimental characterization, this epoxy modeling method demonstrated its predictive capability on the mechanical response of the deteriorated epoxy under different hydro‐thermal‐salt conditions, with the mean absolute percent error (MAPE) of approximately 4.61%. Furthermore, the transverse compressive behavior of unidirectional (UD) CFRPs could be predicted by using the representative volume element (RVE) model with the degraded matrix behavior predicted via this epoxy modeling method. Integrated with this CFRP modeling, results from mechanical tests and fracture analysis further demonstrated that the hydrothermal aging effect on the transverse compressive performance of the UD CFRPs was dominated by the deterioration of their resin matrix. Therefore, this study demonstrates the feasibility of the finite element analysis (FEA) for mechanical aging of the epoxy matrix and its CFRP under hydrothermal conditions via employing the proposed integrated modeling method. Highlights: Degradation of epoxy polymer under hydro‐thermal‐salt aging conditions.Integrated model to predict mechanical response of hydrothermally aged epoxy.RVE model to predict the mechanical behavior of hydrothermally aged CFRP.Hydrothermal aging on the transverse compressive behavior of UD CFRP. [ABSTRACT FROM AUTHOR]

Highlights Designing and optimizing the interface of carbon fiber composites is the key to improve mechanical and biotribological properties. Carbon fiber‐reinforced hydroxyapatite‐epoxy matrix (CM) composites, which have excellent mechanical and biotribological properties, are often used to avoid artificial bone damage and improve the longevity of artificial bone. In this work, a SiC nanowires@pyrolytic carbon (SiCnws@PyC) is designed and incorporated into the CM to improve the mechanical and biotribological properties. SiCnws@PyC can promote bonding of the fiber/matrix interface and cohesion of the epoxy matrix. The mechanical and biotribological properties of CM are greatly improved because of the interface modification and reinforcement of SiCnws@PyC. The tensile strength and elastic modulus of SiCnws@PyC‐reinforced CM are 18.73% and 38.71% higher than those of CM, respectively. SiCnws@PyC‐reinforced CM has a 9.09% reduction in the friction coefficient and a 74.61% reduction in the wear rate. This study provides a promising methodology for the preparation of SiCnws@PyC‐reinforced CM with better stability and longevity for bone grafting applications. The mechanism of SiC nanowires@pyrolytic carbon (SiCnws@PyC) is explained. The SiCnws@PyC structure is designed into composites. PyC core‐shell transforms the structure of hydroxyapatite. The SiCnws@PyC enhances mechanical and biotribological properties of composites. [ABSTRACT FROM AUTHOR]

This review is a fundamental tool for researchers and engineers involved in the design and optimization of fiber-reinforced composite materials. The aim is to provide a comprehensive analysis of the mechanical performance of composites with epoxy matrices reinforced with carbon nanofibers (CNFs). The review includes studies investigating the static mechanical response through three-point bending (3PB) tests, tensile tests, and viscoelastic behavior tests. In addition, the properties of the composites' resistance to interlaminar shear strength (ILSS), mode I and mode II interlaminar fracture toughness (ILFT), and low-velocity impact (LVI) are analyzed. The incorporation of small amounts of CNFs, mostly between 0.25 and 1% by weight was shown to have a notable impact on the static and viscoelastic properties of the composites, leading to greater resistance to time-dependent deformation and better resistance to creep. ILSS and ILFT modes I and II of fiber-reinforced composites are critical parameters in assessing structural integrity through interfacial bonding and were positively affected by the introduction of CNFs. The response of composites to LVI demonstrates the potential of CNFs to increase impact strength by reducing the energy absorbed and the size of the damage introduced. Epoxy matrices reinforced with CNFs showed an average increase in stiffness of 15% and 20% for bending and tensile, respectively. The laminates, on the other hand, showed an increase in bending stiffness of 20% and 15% for tensile and modulus, respectively. In the case of ILSS and ILFT modes I and II, the addition of CNFs promoted average increases in the order of 50%, 100%, and 50%, respectively. [ABSTRACT FROM AUTHOR]

In this study, four distinct composite samples (Samples A, B, C, and D) were fabricated using varying compositions of biochar, rice bran, coconut coir, and epoxy matrix. Sample A, serving as the baseline with 90% epoxy and 10% biochar, exhibited moderate mechanical properties. Sample B, with 80% epoxy and 20% biochar, demonstrated significantly higher tensile and flexural modulus values, indicative of improved stiffness. Sample C, incorporating 10% rice bran alongside 80% epoxy and 10% biochar, displayed reduced mechanical properties compared to Sample B, potentially due to the lower strength of rice bran particles. Sample D, comprising 80% epoxy, 10% biochar, and 5% coconut coir, demonstrated weaker tensile properties but higher flexural modulus, suggesting enhanced resistance to bending forces. Mechanical testing, water absorption analysis, Fourier Transform Infrared (FTIR) spectroscopy, and SEM imaging provided comprehensive insights into the mechanical and chemical characteristics of the composites, underscoring their potential for diverse applications in sustainable materials development. [ABSTRACT FROM AUTHOR]

Natural fibre-reinforced polymer composite (NFRPC) has been introduced as one of the solutions to overcome the ecological and environmental problems accompanying the widespread usage of polymeric materials in every facet of life. However, the organic nature of both natural fibres (NFs) and polymers increases their flammability behaviour, and this, in turn, limits their application. In this regard, this work concentrates on studying the effect of adding flame retardants (FR) to jute-reinforced epoxy composites (JRECs), either by treating the jute fabric with diammonium phosphate (DAP) or adding DAP powder to the epoxy resin matrix on the flame retardancy performance as well as the mechanical properties. The results showed that the effect of the incorporation method of DAP either to jute fabric or to resin matrix has a significant difference on the flammability test results at low concentrations; however, at higher concentrations, the flame retardancy performance is not affected by the technique of adding FR to the composite system. On the other hand, the mechanical properties are significantly affected by the method of incorporating FR to JRECs at all concentrations. Moreover, the results obtained from JRECs with FR systems were evaluated and compared with the literature by constructing selection charts that relate the flame retardancy level to mechanical properties.

The widespread availability of banana peels makes them an excellent resource for bio-fillers in developing environmentally conscious and biodegradable composites, serving as substitutes for plastic and synthetic waste. This study focuses on using banana peel waste as a bio-filler to produce lighter and cheaper materials. The extracted banana peels were subjected to alkali treatment to improve interfacial interaction, and their crystalline performance, functional categories, and morphological studies were examined using XRD, FTIR, and SEM techniques. Composite samples were fabricated with varying bio-filler ratios (0.0, 2.5, 5.0, 7.5, and 10%) to examine their thermo-mechanical and tribological attributes. The inclusion of banana peel in the epoxy matrix at up to 5% significantly enhanced mechanical performance, while 7.5% composites demonstrated higher thermal endurance with a degradation temperature of 395 °C and reduced water retention. Frictional wear of the specimens was assessed by varying sliding speeds under different loads, with the highest coefficient of friction and temperature observed under a 30 N force for BPC-10.0 specimens. This research innovatively uses banana peel powder (approx. 65 µm) to create polymeric composites, addressing the need for sustainable materials with higher specific modulus and strength compared to conventional substances. The study uniquely evaluates the physical, mechanical, structural, and tribological efficiency of raw and processed banana peel particles, with chemical modifications improving crystallinity and interfacial bonding. This comprehensive approach provides vital insights for developing sustainable alternatives to reduce plastic usage. [ABSTRACT FROM AUTHOR]

This study presents the characterization of cross-linking parameters of a liquid crystalline epoxy monomer with an aromatic diamine as a curing agent. The mixture tested consisted of bis [4-(10,11-epoxyundecanoyloxy)benzoate] p-phenylene (LCEM) and 1,3-phenylenediamine (1,3-PDA). This paper focuses on the structural characterization of such systems using X-ray analysis. To investigate this, a comprehensive analysis was conducted using Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray Scattering (WAXS). Through DSC analysis, the curing behavior and transition temperature of the liquid crystal epoxy system were established. To fully characterize the cross-linking of the system, a novel technique called DSC-TOPEM® was employed. The use of this technique enabled real-time monitoring of the curing process and provided precise information on the cross-linking energy, which resulted in the finding that the mixture was cross-linking faster than expected. WAXS analysis was performed to assess the structural changes formed during the cross-linking. The results of this analysis confirm that lower cross-linking temperatures of the mixture cause better ordering of mesogens than higher ones. [ABSTRACT FROM AUTHOR]

As a result of their lower weight and higher strength-to-weight ratio, composite materials are gaining popularity in the automotive sector. Due to their superior mechanical qualities, synthetic hybrid fibres are also utilised in the automotive industry. Still, natural/synthetic hybrid fibres are gradually replacing the synthetic fibre composite to lessen the world's reliance on manufactured materials. Traditional hand layup is used to create three different composite laminates in this study: natural, synthetic and natural/synthetic fibre. The three laminates use jute fibre (corchorus), spandex (elastane) fibre and jute/spandex interwoven fibres as reinforcements; the weight fraction of reinforcement is 45%; the epoxy matrix is 50%, and granite nanoparticles are 5%; the dynamical effect and thermal stability of the hybrid composite are analysed and quantified by changing the weight fraction of reinforcement in the blend. The hybridisation of jute fibre and spandex fibre–interlaced mat loading (jute/spandex) achieved a maximum storage modulus of 2300 MPa at the glass transition temperature, along with improved results in visco-elastic characteristics and 8 per cent greater, 431 °C of thermal stability compared to samples A and B. After composite laminates were fabricated, their layer adhesion and surface finishing were characterised by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) nanoplatelets can be used to reinforce neat resin or the matrix phase of fiber composites for improved mechanical properties. Although the oxygen content levels in GO and reduced graphene oxide (rGO) strongly influence the interface with the polymer, experimental-based optimization of the oxygen content for enhanced composite properties is difficult and time-consuming. Fortunately, molecular dynamics (MD) simulation can be used to efficiently predict the interfacial properties of composite on the molecular level and provide physical insight into the effect of the oxygen content of rGO. In this study, MD is used to predict the elastic properties of rGO/epoxy interfaces and the corresponding interfacial shear strength (IFSS) for different oxygen content levels. The results indicate that increasing levels of oxygen in rGO results in interfaces with a reduced in-plane elastic modulus but a substantially higher IFSS. These results are important for the design of rGO/epoxy composites for specific engineering applications.

This paper aimed to study the compatibility between E-glass of chemical resistance (ECR-glass) fibers and the polymer matrix and the influence of different matrix types on the durability performance of ECR-glass fiber–reinforced polymer (GFRP) bars in a marine concrete environment. Two types of matrices, epoxy and vinyl ester, were employed to fabricate GFRP bars, which were then subjected to accelerated exposure by immersion in a simulated seawater sea-sand concrete (SWSSC) pore solution. The degradation performance and damage mechanism were thoroughly investigated. The results indicated that hydrolytic degradation of the cured epoxy and vinyl matrices and subsequent chemical etching to glass fibers are the primary damage mechanisms affecting GFRP bars in the SWSSC environment. Based on these mechanisms, two damage models were proposed: a chemical etching-based model and a hydroxyl ion diffusion-based model. These models enabled the prediction of the residual tensile strength of GFRP bars in the SWSSC pore solution environment at different temperatures. The accuracy of the proposed models was validated through comparisons with experimental data. [ABSTRACT FROM AUTHOR]

Determining the mechanical properties of a composite material represents an important stage in its design and is generally a complicated operation. These values are influenced by the topology and geometry of the resulting composite and the values of the elastic constants of the components. Due to the importance of this subject and the increasing use of composite materials, different calculation methods have been developed over the last fifty years. Some of the methods are theoretical, with results that are difficult to apply in practice due to difficulties related to numerical calculation. In the current paper, using theoretical results offered by the homogenization theory, values of engineering elastic constants are obtained. The finite element method (FEM) is used to determine the stress and strain field required in these calculations; this is an extremely powerful and verified calculation tool for the case of a material with any type of structure and geometry. In order to minimize errors, the paper proposes the method of least squares, a mathematical method that provides the best estimate for the set of values obtained by calculating FEM. It is useful to consider as many load cases as possible to obtain the best estimates. The elastic constants for a transversely isotropic material (composite reinforced with cylindrical fibers) are thus determined for a real case. [ABSTRACT FROM AUTHOR]

Green and renewable materials are becoming promising worldwide. Here, we compared morphological and mechanical strength characteristics of natural plant-based bast fibers (flax, hemp and nettle) with those of synthesized fibers (glass, basalt, carbon, polyacrylonitrile (PAN), polycaproamide (PCA) and viscose). The industrial bast fibers from hemp and nettle were extracted by chemical treatment with a sodium carbonate solution. The natural fibers were comparable in size to the synthetic ones. The PCA fibers had the largest diameter of 23–28 µm. The carbon monofiber had the lowest diameter of 7–8 µm. The dimension of the natural elementary fibers was 10–25 µm. The natural fibers had a better interfacial bonding to an epoxy matrix than PCA. Moreover, the specific strength of the unimpregnated and epoxy-impregnated fibers was determined. The natural fibers were superior in strength performance to some of synthetic fibers (viscose), while the specific strength of the impregnated flax fiber was commensurate with that of the impregnated PAN and PCA fibers. The specific strength of the flax and hemp fibers once impregnated with the matrix increased four- and twofold, respectively. The impregnated flax fibers exhibited the best mechanical strength behavior among the hemp and nettle bast fibers. The natural fibers are biodegradable, have a low density, and are more eco-benign than the mineral fibers. The selected natural fibers can be used to fabricate composites therefrom. [ABSTRACT FROM AUTHOR]

Creating environmentally friendly and renewable resources for various industrial uses has attracted increasing attention over the past few years. The thermal and mechanical features of epoxy-based composites filled with coir powder, an organic and sustainable fiber made from coconut husks, are examined in this work. The current study focuses on the thermo-mechanical performance of epoxy matrix composites with coir filler in the micrometer range. Tension, flexural, and dynamic mechanical analysis were all carried out to characterize and forecast the thermal behavior of the micro-composites and pure polymers. According to the findings of this study, 8 and 6 wt.% of coir filler-based composites exhibit the highest tensile and flexural strengths of 41.36 MPa and 171.24 MPa, respectively. In the case of dynamic mechanical analysis, 8 wt.% filler had the highest storage modulus of 1214.98 MPa. The results demonstrate that the damping factor increases dramatically as the temperature rises and reaches its maximum value after the glass transition section. Additionally, including coir powder improves the composites' thermal insulation capabilities, indicating their promise in demanding thermal resistance and insulation. [ABSTRACT FROM AUTHOR]

In this study, the potential use of nanocrystalline cellulose (CNC) modified epoxy nanocomposite as a matrix is investigated for both glass and carbon fiber-reinforced composites. Various amounts of CNCs (1, 2, 4, and 6 wt%) were added to bisphenol A diglycidyl ether-based epoxy resin (DGEBA), and the optimum CNC loading was determined as 4 wt% in terms of mechanical and thermal properties. Compared to the reference sample containing a neat epoxy matrix with the obtained carbon fiber/CNC-epoxy (CNC/epoxy/CF) and glass fiber/CNC-epoxy (CNC/epoxy/GF) hybrid nanocomposites, significant improvements have been determined in the in-plane shear modulus and strength, and flexural modulus, respectively. The mechanical properties improvements of CNC/epoxy/CF hybrid composites are approximately 0.9% higher than the CNC/epoxy/GF hybrid composites. Additionally, the distribution of CNC in hybrid nanocomposites is also investigated by scanning and transmission electron microscopies. It is noted that the homogenous dispersion of CNCs in the epoxy matrix and their diameters varied from 10 to 100 nm are detected at higher magnification.

In this study, we utilized the material design library in Ansys Product 2022 R1 to analyze the impact of short plant fibers on the mechanical properties of epoxy resin. We employed the representative volume element (RVE) approach and examined different volume fractions up to 50%. The technique employed in this study was multi-scale modeling based on the finite element method (FEM) for numerical homogenization. Subsequently, we used the same software to develop a five-layer laminated composite. The samples were based on epoxy resin enriched with short plant fibers at fractions of 20% and 30%, as well as pure epoxy resin. The laminated composites were reinforced with carbon fibers. The objective of this study was to analyze the mechanical response of each sample during a tensile test, focusing on multiple parameters. The sought-after results included total deformation, directional deformation, equivalent and elastic stress (Von-mises). The samples containing epoxy resin enriched with 30% of short hemp fibers exhibited remarkable mechanical strength compared to the other samples. These results suggest that the incorporation of short hemp fibers into the matrix led to a significant improvement in the mechanical strength of the composite. [ABSTRACT FROM AUTHOR]

A procedure and results of estimating the adhesion strength of a fiber–matrix system are presented. Carbon and basalt fibers are used, and a composition of epoxy resin and an amine solidifier is applied as a polymer matrix. The results of strength tests on the estimation of the adhesion strength by the pull-out method using two types of samples are presented: macro- and microsamples differ in the accuracy of determining the contact area between a fiber and the polymer matrix. The values of adhesion strength of microsamples based on elemental fibers are found to be lower than those of macrosamples, but the determination accuracy is substantially higher than that for the macrosamples. [ABSTRACT FROM AUTHOR]

The research focuses on connections of wooden structural elements with composite materials based on fiberglass. An overview of existing research and regulatory technical documents in the field of connections between wooden elements and composite materials based on fiberglass has been conducted. A type of connection for wooden elements with composite materials based on fiberglass is proposed. The article presents the results of strength and deformability studies of the developed connection. Strength characteristics are established in the form of the slice resistance of the composite material along the welding seam in the connection, a tear resistance of the composite material from the base, and the chipping of the composite material. The deformability characteristics of fiberglass connections under short-term machine testing with linearly increasing load in samples have been determined. [ABSTRACT FROM AUTHOR]

The present work aims to perform an extensive numerical study based on genetic algorithms and Weibull probabilistic approach to highlight the effect of date palm fiber (DPF), doum palm and alfa fibers on the fiber–matrix interface damage of date palm/epoxy, doum palm/epoxy, and alfa/epoxy biocomposite materials. The results obtained in this study coincide perfectly and in good agreement with very recent theoretical and experimental studies. Mehdi Jonoobi et al. found through experimental trials that date palm fibers can be used to improve the ductility of epoxy matrix, and the use of date palm fibers in an epoxy-based composite can improve epoxy strength according to the weight ratio of fiber used, in addition, Noora Al-Qahtani et al. found that the morphology of the composites was improved which present superior adhesion among the palm fiber and the polymer matrix. Thus, it is useful now to study the opportunity to promote date palm fiber in different development sectors to encourage industries to manufacture ecological products from the date palm which will be a candidate promoter for new technological applications. [ABSTRACT FROM AUTHOR]

This review is a fundamental tool for researchers and engineers involved in the design and optimization of fiber-reinforced composite materials. The aim is to provide a comprehensive analysis of the mechanical performance of composites with epoxy matrices reinforced with carbon nanofibers (CNFs). The review includes studies investigating the static mechanical response through three-point bending (3PB) tests, tensile tests, and viscoelastic behavior tests. In addition, the properties of the composites’ resistance to interlaminar shear strength (ILSS), mode I and mode II interlaminar fracture toughness (ILFT), and low-velocity impact (LVI) are analyzed. The incorporation of small amounts of CNFs, mostly between 0.25 and 1% by weight was shown to have a notable impact on the static and viscoelastic properties of the composites, leading to greater resistance to time-dependent deformation and better resistance to creep. ILSS and ILFT modes I and II of fiber-reinforced composites are critical parameters in assessing structural integrity through interfacial bonding and were positively affected by the introduction of CNFs. The response of composites to LVI demonstrates the potential of CNFs to increase impact strength by reducing the energy absorbed and the size of the damage introduced. Epoxy matrices reinforced with CNFs showed an average increase in stiffness of 15% and 20% for bending and tensile, respectively. The laminates, on the other hand, showed an increase in bending stiffness of 20% and 15% for tensile and modulus, respectively. In the case of ILSS and ILFT modes I and II, the addition of CNFs promoted average increases in the order of 50%, 100%, and 50%, respectively.

This study presents the characterization of cross-linking parameters of a liquid crystalline epoxy monomer with an aromatic diamine as a curing agent. The mixture tested consisted of bis [4-(10,11-epoxyundecanoyloxy)benzoate] p-phenylene (LCEM) and 1,3-phenylenediamine (1,3-PDA). This paper focuses on the structural characterization of such systems using X-ray analysis. To investigate this, a comprehensive analysis was conducted using Differential Scanning Calorimetry (DSC) and Wide-Angle X-ray Scattering (WAXS). Through DSC analysis, the curing behavior and transition temperature of the liquid crystal epoxy system were established. To fully characterize the cross-linking of the system, a novel technique called DSC-TOPEM® was employed. The use of this technique enabled real-time monitoring of the curing process and provided precise information on the cross-linking energy, which resulted in the finding that the mixture was cross-linking faster than expected. WAXS analysis was performed to assess the structural changes formed during the cross-linking. The results of this analysis confirm that lower cross-linking temperatures of the mixture cause better ordering of mesogens than higher ones.

In the present work, a commercial epoxy based on epoxy anhydride and tertiary amine was modified by a metallic catalyst (Zn2+) to induce vitrimeric behavior by promoting the transesterification reaction. The effect of two different epoxy/acid ratios (1 and 0.6) at two different zinc acetate amounts (Zn(Ac)2) on the thermomechanical and viscoelastic performances of the epoxy vitrimers were investigated. Creep experiments showed an increase in molecular mobility above the critical "Vitrimeric" temperature (Tv) of 170 °C proportionally to the amount of Zn(Ac)2. A procedure based on Burger's model was set up to investigate the effect of catalyst content on the vitrimer ability to flow as the effect of the dynamic exchange reaction. The analysis showed that in the case of a balanced epoxy/acid formulation, the amount of catalyst needed for promoting molecular mobility is 5%. This system showed a value of elastic modulus and dynamic viscosity at 170 °C of 9.50 MPa and 2.23 GPas, respectively. The material was easily thermoformed in compression molding, paving the way for the recyclability and weldability of the thermoset system. [ABSTRACT FROM AUTHOR]

The physical-mechanical properties of epoxy matrices modified with polyethersulfone (PES) and unidirectional glass- and carbon-fiber-reinforced plastics (GFRP and CFRP) based on them were investigated. The fracture toughness of epoxy matrices modified with 20 wt% PES, increased by 4.3 times. The delamination energy of GFRP and CFRP with this content of PES in the matrix increases by 50 and 65%, respectively. A correlation between the fracture toughness of modified matrices and the delamination toughness of GFRP and CFRP was established, and the influence of structure of the matrices on the fracture toughness of the reinforced plastics was demonstrated. A significant increase in the fracture toughness of the matrices and reinforced plastics was also observed during the formation of extended phases enriched with PES. [ABSTRACT FROM AUTHOR]

The inclusion of both fibre and solid lubricants into polymers may provide a potential solution to maximise their tribological and mechanical performances. This study investigates the effect of incorporating flax fibres and graphene nanoplatelets (GNPs) reinformcements in epoxy matrix composites on their tensile, microhardness and adhesive wear behaviour. Dry adhesive wear experiments were conducted using a block-on-ring (BOR) test rig against a stainless steel ring. Adhesive wear performance was evaluated considering the effect of the volume fraction (V f ) of flax fibre (0, 15, 20 and 25 V f . %) and different weight fractions of GNPs (1.5 and 3 wt.%). Different applied loads in the 15–60 N range, covering the mild and severe wear regions, were used. The worn surfaces were examined using a scanning electron microscope (SEM). The results revealed that flax fibre potently improved the stiffness and tensile strength of epoxy. Increase in V f of flax fibre showed a positive tendency to improve the wear resistance of epoxy; however, with an insignificant change in the coefficient of friction (COF). More interestingly, heat distortion temperature (HDT) was found to be the main key parameter controlling the wear behaviours of the composites. SEM observations indicated that severe wear signs – including detachment, fragmentation and fibre debonding – were noted when the interface temperature reached the heat distortion temperature of the epoxy. On the other hand, the inclusion of GNPs reduced the interface temperature during sliding as well as the COF of the flax/epoxy composite. Ultimately, incorporation of flax fibres and GNPs enhanced both mechanical and tribological performances of the eco-composites. [ABSTRACT FROM AUTHOR]

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made by introducing a metal catalyst (Zn2+) and its carbon fibre composites, focusing on the healing capability of the system. The dynamic crosslinking networks endow vitrimers with interesting rheological behaviour; the capability of the formulated resin (AV-5) has been assessed by creep tests. The analysis showed increased molecular mobility above a topology freezing temperature (Tv). However, the reinforcement phase inhibits the flow capability, reducing the flow. The fracture behaviour of CFRP made with the vitrimeric resin has been investigated by Mode I and Mode II tests and compared with the conventional system. The repairability of the vitrimeric CFRP has been investigated by attempting to recover the delaminated samples, which yielded unsatisfactory results. Moreover, the healing efficiency of the modified epoxy composites has been assessed using the vitrimer as an adhesive layer. The joints were able to recover about 84% of the lap shear strength of the pristine system. [ABSTRACT FROM AUTHOR]

Cerium carbide (CeC2), an inorganic nanofiller, was altered with 3-(2-mercaptoethylamino) propyldimethoxymethylsilane (MEAPS), and the resulting MEAPS/CeC2 was encased with graphene oxide (GO) in the pure epoxy resin (EP). By using electrochemical techniques in the marine environment, the protective behaviour of mild steel coated with epoxy in the presence of varying amounts of GO enclosed in silanized cerium carbide was examined. The epoxy-GO/MEAPS-CeC2 had an improved coating resistance of 9698.17 kΩ.cm2, according to the EIS measurements, even after 480 h of exposure to seawater. After being submerged in seawater for an hour, it was revealed that the coating resistance of EP-GO/MEAPS-CeC2 was found to be more than 42 times higher than that of pure EP. The EP-GO/MEAPS-CeC2 nanocomposite coated steel (1.5 I/nA) has the lowest ferrous ion dissipation, according to SECM investigations. Silanized cerium carbide was found to be improved in the degradation products, producing a robust inert nanolayered coating, according to FE-SEM/EDX research. With a WCA of 149°, the newly fabricated EP-GO/MEAPS-CeC2 coating had exceptional water-repellent qualities. In terms of adhesion strength and hardness, MEAPS/CeC2 wrapped in graphene oxide showed good mechanical qualities in the epoxy substrate. Prior to being submerged in seawater, an improved adhesive strength was attained for mild steel coated with EP-GO/MEAPS-CeC2 (13.8 MPa). The GO/MEAPS-CeC2 forms a robust inert crystalline covering that prevents ions from penetrating the specimen. As a result, the coating has increased adhesive strength and is able to remain intact after extended immersion times. Therefore, the EP-GO/MEAPS-CeC2 nanocomposite could act as a viable coating component for automotive parts. [ABSTRACT FROM AUTHOR]

A hyperelastic–viscoplastic constitutive model is developed to describe the strain-softening behavior of glass-filler-reinforced–epoxy composites under large strain-compression loading. The model's rheological network comprises two parallel networks; the first consists of a nonlinear elastic spring in series with a nonlinear viscous dashpot, and the other involves a hyperelastic Langevin spring. The postyield strain softening in the model is introduced by a time-dependent shear resistance to molecular deformation, where the shear resistance is varied from an initial value up to a saturation value at large strain. The model is reduced to a one-dimensional incompressible case, and fitted to the experimental data of spherical- and milled-glass-fiber–epoxy composites to retrieve the optimized model parameters. Milled-fiber–epoxy composites exhibit higher values of optimized elastic modulus and shear deformation resistance parameters, which are correlated to outcomes of dynamic mechanical analyses like filler-reinforcement efficiency, polymer chain-entanglement density, and filler–matrix adhesion. The improvement in filler-reinforcement efficiency due to milled fibers leads to better load transmission to the matrix, resulting in enhanced elastic modulus of milled-fiber–epoxy composites. An increase in polymer chain-entanglement density and filler–matrix adhesion results in higher resistance to viscous flow for milled-fiber composites. Semiempirical equations for elastic modulus and shear-deformation resistance parameters are proposed that consider the relative stiffness of filler and matrix, and the shape and volume fraction of fillers. When the fillers are embedded in the polymer matrix, these equations operate as multiplicative factors to the neat polymers. Thus, the model is capable of capturing the stress–strain response of both neat polymer and glass-filled polymer composites. [ABSTRACT FROM AUTHOR]

Determining the mechanical properties of a composite material represents an important stage in its design and is generally a complicated operation. These values are influenced by the topology and geometry of the resulting composite and the values of the elastic constants of the components. Due to the importance of this subject and the increasing use of composite materials, different calculation methods have been developed over the last fifty years. Some of the methods are theoretical, with results that are difficult to apply in practice due to difficulties related to numerical calculation. In the current paper, using theoretical results offered by the homogenization theory, values of engineering elastic constants are obtained. The finite element method (FEM) is used to determine the stress and strain field required in these calculations; this is an extremely powerful and verified calculation tool for the case of a material with any type of structure and geometry. In order to minimize errors, the paper proposes the method of least squares, a mathematical method that provides the best estimate for the set of values obtained by calculating FEM. It is useful to consider as many load cases as possible to obtain the best estimates. The elastic constants for a transversely isotropic material (composite reinforced with cylindrical fibers) are thus determined for a real case.

This paper investigates the influence of fiber length and fiber surface modification on the flexural properties of coir fiber-reinforced epoxy composites. The fiber lengths and concentration of sodium hydroxide (NaOH) solution for fiber treatment are the considered parameters for the investigation. The test specimens were fabricated by hand lay-up technique. The study reveals that NaOH concentration in the fiber treatment played a significant role in the flexural strength of coir fiber reinforced epoxy composites. However, an increase in NaOH concentration above 4% reduces the flexural strength. It was also found that the increase in fiber length was linearly proportionate to the flexural strength. The fiber surface morphology and the fractured surface of the composites were explored by SEM (Scanning Electron Microscope) images.

The widespread use of polymer composite materials (PCM) leads to an increase in non-recyclable waste. This paper discusses the feasibility of recycling fiberglass with an epoxy matrix by solvolysis in ethanol under supercritical conditions. The solvolysis process completes successfully within four hours in an environment of a pure solvent containing 10% water at a temperature of 280 °C when the solvent passes into the supercritical state. The treatment time increases up to 10 h at a process temperature of 250 °C. When using a coordination compound of copper(II) chloride with organic chloride salt having 2,3,5-triphenyltetrazolium as the counterion, having the composition of (2,3,5-triphenyltetrazolium)2[CuCl4], the treatment time is reduced. The addition of the complex of 5% by weight makes it possible to completely remove the epoxy matrix at a temperature of 250 °C for two hours. The products separated from the solvolysis liquid were studied by infrared spectroscopy. The resulting fibers were examined by thermogravimetric analysis and scanning electron microscopy. The residual strength of the recovered fibers is 98%. Thus, the resulting fibers can be reused in the composite industry. Including both for the production of decorative products and for the production of structural products made of polymer composite materials. [ABSTRACT FROM AUTHOR]

Creating environmentally friendly and renewable resources for various industrial uses has attracted increasing attention over the past few years. The thermal and mechanical features of epoxy-based composites filled with coir powder, an organic and sustainable fiber made from coconut husks, are examined in this work. The current study focuses on the thermo-mechanical performance of epoxy matrix composites with coir filler in the micrometer range. Tension, flexural, and dynamic mechanical analysis were all carried out to characterize and forecast the thermal behavior of the micro-composites and pure polymers. According to the findings of this study, 8 and 6 wt.% of coir filler-based composites exhibit the highest tensile and flexural strengths of 41.36 MPa and 171.24 MPa, respectively. In the case of dynamic mechanical analysis, 8 wt.% filler had the highest storage modulus of 1214.98 MPa. The results demonstrate that the damping factor increases dramatically as the temperature rises and reaches its maximum value after the glass transition section. Additionally, including coir powder improves the composites’ thermal insulation capabilities, indicating their promise in demanding thermal resistance and insulation.

The research focuses on connections of wooden structural elements with composite materials based on fiberglass. An overview of existing research and regulatory technical documents in the field of connections between wooden elements and composite materials based on fiberglass has been conducted. A type of connection for wooden elements with composite materials based on fiberglass is proposed. The article presents the results of strength and deformability studies of the developed connection. Strength characteristics are established in the form of the slice resistance of the composite material along the welding seam in the connection, a tear resistance of the composite material from the base, and the chipping of the composite material. The deformability characteristics of fiberglass connections under short-term machine testing with linearly increasing load in samples have been determined.

This paper investigates the influence of fiber length and fiber surface modification on the flexural properties of coir fiber-reinforced epoxy composites. The fiber lengths and concentration of sodium hydroxide (NaOH) solution for fiber treatment are the considered parameters for the investigation. The test specimens were fabricated by hand lay-up technique. The study reveals that NaOH concentration in the fiber treatment played a significant role in the flexural strength of coir fiber reinforced epoxy composites. However, an increase in NaOH concentration above 4% reduces the flexural strength. It was also found that the increase in fiber length was linearly proportionate to the flexural strength. The fiber surface morphology and the fractured surface of the composites were explored by SEM (Scanning Electron Microscope) images. [ABSTRACT FROM AUTHOR]

This paper focus on the process of fiber reinforced composites a significant portion of the paper emphasis the use of different machine, basic concept introduced in this paper of molding method and pouring of epoxy, hardener and nano silica mixture with hand lay-up technique. This study aims to develop fibre-reinforced epoxy hybrid composites by using hand lay-up method. In this work different material used are Epoxy LY556, Hardner HY951, SiO2 nano particle (Particle size 60-70nm) and 90 degree bidirectionl wooven bamboo fibre. Sample designated are as A10 (One layer Babboo fibre, 0% SiO2), A12 (2%SiO2), A14 (4%SiO2),B20 (Two-layer bamboo fibre, 0% SiO2), B22(2%SiO2), B24(4%SiO2), C30 (three layer bamboo fibre, 0% SiO2),C32(2%SiO2) and C34(4%SiO2). Samples were prepared by handlayup method. The effect of various weight percent of SiO2on mechanical property were investigated. The maximum value of tensile strength was found for sample C32, higher value of flexural strength was found for sample C32, higher value of izod impact test was for sample C32 and maximum value of barcol hardness was for sample B22. [ABSTRACT FROM AUTHOR]

A technique of sample preparation and the results of evaluation of adhesive strength using the pullout method have been presented. Carbon and basalt fibers have been used as fillers, and epoxy material has been used as a polymer matrix. The use of elementary carbon and basalt fibers with a diameter of 5 and 15 μm, respectively, is a feature of these tests. A list of the main technological errors arising in the manufacture of samples has been given, and methods for their elimination have been proposed. The results of strength tests on the assessment of adhesive strength determined by the pullout method and with interlayer shear have been presented. [ABSTRACT FROM AUTHOR]

Hollow silica nanospheres (HSNs) have superior properties such as low density, low dielectric constant, low thermal conductivity, good sound absorption, dispersibility, fluidity, and stability. They have the potential to be utilised as a reinforcing material in the development of next generation composites due to their properties. Epoxy is one of the commonly utilised polymers in today's technology. Production of epoxy matrix composite materials reinforced with particles having superior properties will open up new application areas for epoxy. In this study, mesoporous HSNs were produced. The mechanical, thermal and sound insulation properties of the composite were examined by reinforcing these mesoporous HSNs to the epoxy matrix. The epoxy matrix was reinforced with HSNs at 1 wt.%, 5 wt.%, and 10 wt.%. When the concentration of HSNs in the epoxy matrix was increased, its strength increased and its ductility decreased. While the non-reinforced epoxy had a tensile strength of 36.45 MPa, but the tensile strength of epoxy at the end of 10% HSN reinforcement reached 89.06 MPa. The strain % reduced in half. The sound insulation properties of epoxy improved as the concentration of HSNs increased. Thermal conductivity coefficient dropped up to a 5% reinforcement ratio, and then increased slightly at a 10% reinforcement ratio. The microstructure analyses indicated that when the reinforcement ratio increased, difficulties in the distribution of reinforcements to the matrix appeared. Furthermore, it was observed that when the matrix/reinforcement interface was improved, the properties of the composite improved. [ABSTRACT FROM AUTHOR]

High performance polymer composites are essential materials in nuclear applications where many components can receive high ionizing rays doses such as gamma-rays. In this work, two composites named E51WB and E51WB2 based on epoxy (E51) and tungsten borides (WB and WB2) were manufactured at room temperature and then exposed to gammarays doses up to 2000 KGy. The goal of this study was to investigate and compare the impact of gamma-rays on the chemical structure, mechanical and thermal properties of E51WB and E51WB2 composites using FTIR, SEM, TGA and tensile tests. As the results, the char yield (Yc) for E51WB gradually increased from 40 to 46% at 0, 1000 and 1500 KGy, then slightly drop to 44% at 2000 KGy. The E51WB sample displayed the strain value of 2.3% at 0 KGy, and it increased to 4.7 and 5 % at 1000 and 1500 KGy, respectively, while at 2000 KGy it decreased to 3.5%. This may be due to phenomena such as hydrogen abstraction, disproportion, degradation or the formation of new bonds. The comparison of the TGA results of E51WB and E51WB2 at 1000 and 1500 KGy respectively, leads to the conclusion that E51WB2 is thermally more resistant. In addition, by comparing the tensile strength of these two samples at the same irradiation doses, it can be stated that the E51WB2 composite is stronger than its counterpart E51WB. [ABSTRACT FROM AUTHOR]

In the present work, a commercial epoxy based on epoxy anhydride and tertiary amine was modified by a metallic catalyst (Zn2+) to induce vitrimeric behavior by promoting the transesterification reaction. The effect of two different epoxy/acid ratios (1 and 0.6) at two different zinc acetate amounts (Zn(Ac)2) on the thermomechanical and viscoelastic performances of the epoxy vitrimers were investigated. Creep experiments showed an increase in molecular mobility above the critical “Vitrimeric” temperature (Tv) of 170 °C proportionally to the amount of Zn(Ac)2. A procedure based on Burger’s model was set up to investigate the effect of catalyst content on the vitrimer ability to flow as the effect of the dynamic exchange reaction. The analysis showed that in the case of a balanced epoxy/acid formulation, the amount of catalyst needed for promoting molecular mobility is 5%. This system showed a value of elastic modulus and dynamic viscosity at 170 °C of 9.50 MPa and 2.23 GPas, respectively. The material was easily thermoformed in compression molding, paving the way for the recyclability and weldability of the thermoset system.

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made by introducing a metal catalyst (Zn2+) and its carbon fibre composites, focusing on the healing capability of the system. The dynamic crosslinking networks endow vitrimers with interesting rheological behaviour; the capability of the formulated resin (AV-5) has been assessed by creep tests. The analysis showed increased molecular mobility above a topology freezing temperature (Tv). However, the reinforcement phase inhibits the flow capability, reducing the flow. The fracture behaviour of CFRP made with the vitrimeric resin has been investigated by Mode I and Mode II tests and compared with the conventional system. The repairability of the vitrimeric CFRP has been investigated by attempting to recover the delaminated samples, which yielded unsatisfactory results. Moreover, the healing efficiency of the modified epoxy composites has been assessed using the vitrimer as an adhesive layer. The joints were able to recover about 84% of the lap shear strength of the pristine system.

Date palm fibre is considered as an agricultural waste suitable as reinforcement for polymeric composites has received interest as an interior component in the automotive industry. The aim of this work to investigate the physical and mechanical properties of date palm fibre (leaf stalk, tree trunk, fruit stalk and leaf sheath) reinforced epoxy composites and date palm/bamboo hybrid composites suitable for non-structural and semi-structural applications. The different composites were fabricated using a hand lay-up technique in combination with compression moulding method. Date palm fibre/bamboo hybrid composite, and pure composites were characterized by various mechanical testing such as tensile, flexural and low-velocity impact testing. Exposure to liquid water and environmental conditions affect the durability of biobased composites. The water absorption behaviour and its effects on the thickness swelling, changes in density and physical performance of different composites were further investigated. The experimental results of the date palm fibre/bamboo hybrid composite exhibited the highest mechanical properties compared to date palm fibre composite without hybridisation. The tensile strength, flexural strength and impact toughness values for the date palm/bamboo hybrid composite were recorded at 39.16 MPa, 61.10 MPa and 12.70 J/m, respectively. Interestingly, the physical test of thickness swelling and water absorption results has indicated that date palm fibre/bamboo hybrid composite displayed 27.68% and 15.39% less when compared with single date palm fibre composite. Therefore, the results have discovered that the date palm fibre/bamboo hybrid composite has the prospective to be applied as a non-structural and semi-structural components.

"Green" thermally stable hardener was synthesized from a PET waste. The rigid molecular linear structure of the new hardener suggests that it will provide the polymer matrix with the necessary physical and mechanical characteristics. It also allows the expectation that cured matrix based on this hardener can provide increased toughness. New hardener was used as a curing agent for three epoxy resins—tetraglycidyl methylenedianiline (TGDMA, 111–117 EEW), diglycidylether of bisphenol A (DGEBA, 170-192 EEW) and solid epoxy resin (SER)—with a medium molecular weight (860–930 EEW) based on DGEBA. The mixtures were found to have the highest Tg for the DGEBA resin, and high of that for TGDMA and SER. According to the DMA analysis for two cured matrices, the hardener proved to be no worse than the standard ones, and made it possible to obtain cured matrices with excellent mechanical properties, which allows us to hope for further application of new hardener cured epoxy matrices in appropriate composite materials at high temperatures. [ABSTRACT FROM AUTHOR]

This work is aimed to synthesize novel structural epoxy nanocomposites containing graphene oxide (GO) and 3-(trimethoxysilyl) propyl methacrylate (TMSPMA) modified W2C. The coating resistance of EP-GO/TMSPMA-W2C was additionally noticed to be over 44.9% higher than that of pure matrix. The GO/TMSPMA-W2C was enriched in the degradation products, forming an excellent passive layer at the coating/steel interface. The newly designed EP-GO/TMSPMA-W2C nanocomposite coating had improved protection against corrosion and excellent hydrophobic characteristics (WCA: 159°). The incorporation of graphene oxide enveloped W2C in the epoxy matrix resulted in improved adhesion strength, tensile strength and hardness properties. [ABSTRACT FROM AUTHOR]