Reinforced Epoxy Composites Research Articles

Conventional Thermoset Composites and Their Sustainable Alternatives with Vitrimer Matrix—Waste Management/Recycling Options with Focus on Carbon Fiber Reinforced Epoxy Resin Composites

Carbon-fiber-reinforced polymers (CFRPs) with epoxy matrices are widely applied in high-performance structural applications and represent one of the biggest classes of materials with urgent need for end-of-life management. Available waste management methodologies for conventional thermoset composites with a focus on CFRPs are briefly reviewed and their limitations are highlighted. In the quest to obtain materials with mechanical performance, thermal stability, and sustainability, the research community has turned its interest to develop polymer composites with adaptable and dynamic networks in their matrix, and lately also at an interface/interphase level. The current review focuses on the life extension/waste management options that are opened through the introduction of covalent adaptable networks in the epoxy matrix of CFRPs. The processing conditions that are applied for the healing/repairing, welding/reshaping, and/or recycling of CFRPs are presented in detail, and compared based on the most common dynamic exchange reactions.

Effects of the Rate Dependency of a Matrix Material on the Tensile Response of Plain Weave Carbon Fabric Reinforced Epoxy Composites

Effects of the Rate Dependency of a Matrix Material on the Tensile Response of Plain Weave Carbon Fabric Reinforced Epoxy Composites

Facial functionalization carbon fiber with MnO2 nanosheets for high‐performance epoxy composites with excellent flame retardancy and mechanical properties

AbstractThe carbon fiber (CF) reinforced epoxy composites possess exceptional and distinctive properties as advanced composite materials. However, the flammability of epoxy resin and inadequate interfacial bonding between the resin and CF often impose limitations on their broader application. Herein, in order to enhance the flame retardancy of EP composites effectively, a hierarchical reinforcement was developed by facilely growing MnO2 nanosheets onto CF surface through an in situ process. Owing to their synergistic effects of physical barrier and chemical catalytic behavior, the presence of MnO2 nanosheets can effectively retard the combustion process by facilitating charring formation and suppressing heat and smoke release. Specifically, compared to the Untreated CF, the modified fiber reinforced composites exhibited significantly improved fire safety with reduction of 76.23%, 51.5% and 23.1% in peak heat release rate, total heat release and peak smoke production rate, respectively. Additionally, incorporating MnO2 nanosheets significantly enhanced mechanical properties of the composites, leading to remarkable enhancements of 41.8% in flexural strength and 28.14% in interlaminar shear strength. This study proposes an effective strategy for achieving outstanding flame retardancy and mechanical performance, thereby introducing an innovative concept for the production of high‐performance CF reinforced polymer composites.Highlights Growth of MnO2 nanoparticles enhanced the mechanical properties of the CF/EP composites. The CF‐MnO2/EP composites showed excellent flame retardancy. The flame retardant mechanism of CF‐MnO2/EP composites were analyzed. Highlight the potential application of MnO2 in the field of flame retardancy.

Friction Behaviors and Wear Mechanisms of Carbon Fiber Reinforced Composites for Bridge Cable.

Carbon fiber reinforced epoxy resin composites (CFRP) demonstrate superior wear resistance and fatigue durability, which are anticipated to markedly enhance the service life of structures under complex conditions. In the present paper, the friction behaviors and wear mechanisms of CFRP under different applied loads, sliding speeds, service temperatures, and water lubrication were studied and analyzed in detail. The results indicated that the tribological properties of CFRP were predominantly influenced by the applied loads, as the tangential displacement generated significant shear stress at the interface of the friction pair. Serviced temperature was the next most impactful factor, while the influence of water lubrication remained minimal. Moreover, when subjected to a load of 2000 g, the wear rate and scratch width of the samples exhibited increases of 158% and 113%, respectively, compared to those loaded with 500 g. This observed escalation in wear characteristics can be attributed to irreversible debonding damage at the fiber/resin interface, leading to severe delamination wear. At elevated temperatures of 100 °C and 120 °C, the wear rate of CFRP increased by 75% and 112% compared to that at room temperature. This augmentation in wear was attributed to the transition of the epoxy resin from a glassy to an elastic state, which facilitated enhanced fatigue wear. Furthermore, both sliding speed and water lubrication displayed a negligible influence on the friction coefficient of CFRP, particularly under water lubrication conditions at 60 °C, where the friction coefficient was only 15%. This was because the lubricant properties and thermal management provided by the water molecules, which mitigated the frictional interactions, led to only minor abrasive wear. In contrast, the wear rate of CFRP at a sliding speed of 120 mm/s was found to be 74% greater than that observed at 60 mm/s. This significant increase can be attributed to the disparity in sliding rates, which induced uncoordinated deformation in the surface and subsurface of the CFRP, resulting in adhesive wear.

Graphene nanoplatelets inclusion effects on mechanical properties of the hybrid kevlar/basalt fiber reinforced epoxy composites

Abstract This study experimentally examined the effects of hybridizing Basalt and Kevlar fibers on the tensile, and flexural performance of composite materials with the inclusion of Graphene nanoplatelets (GnPs). Various hybrid composites were fabricated, incorporating Basalt and Kevlar fiber composites with 1, 3, and 5 wt% of GnPs as well as without GnPs, as well as hybrid composites featuring different weight content of GnPs reinforcing with with Basalt and Kevlar fibers. The findings of this study indicated that the mechanical properties of epoxy resin were significantly enhanced through the synergistic effects of hybridization with basalt and Kevlar fibers, as well as the incorporation of graphene nanoplatelets (GnPs). The significant increasing in mechanical properties was attributed to the strong interfacial interactions between the epoxy matrix and GnPs nanoparticles, which facilitate improved stress transfer from the fibers and nanoparticles to the matrix. This enhanced stress transfer capability accounts for the superior resistance to fiber pullout observed in composites reinforced with GnPs compared to those without nanoparticles.

Improving interlaminar fracture toughness and compression after impact strength of carbon fiber reinforced epoxy composites by interleaving electrospinning polyethersulfone nanofiber

AbstractThe effect of membrane thickness of electrospinning polyethersulfone (PES) nanofiber membranes on interlayer toughness and impact resistance of carbon fiber reinforced epoxy resin (CF/EP) composites are researched. Intercalation composites with different nanofiber membrane thicknesses, ranging from 10 to 50 μm, are tested at mode I and mode II interlaminar fracture toughness. The impact resistance of nanofiber membranes with different thicknesses is evaluated by the compression after impact (CAI) strength test. Moreover, nanofiber toughening contributions are investigated using the crack path and surface analysis. Results indicate that PES nanofibers increase the toughness of interlayer resin and change the interlaminar crack propagation path of CF/EP composites. The optimum nanofiber membrane thickness for mode I (GI = + 58%) and CAI (CAI strength = + 33%) is 50 μm, while for mode II is 30 μm (GII = + 16.4%). The storage modulus of CF/EP composites increases with the increase of nanofiber membrane thickness. The study also confirms the insertion of a nanofiber membrane slightly improves the tensile strength and interlaminar shear strength (ILSS) of the CF/EP composites.Highlights PES nanofiber membranes of different thicknesses were inserted into the CF/EP. CAI and GI improved by 33% and 58%, respectively of CF/EP composites. The relationship between interlayer fracture toughness and CAI was discussed.

Effect of hollow beads content in aluminum oxide hollow beads reinforced epoxy composites on mechanical and energy absorption properties of the composites

AbstractAluminum oxide hollow microbeads/epoxy resin composite is a kind of epoxy resin‐based multi‐porous energy‐absorbing material. This study improved the brittleness and toughness of epoxy resin. Adding hollow aluminum oxide microbeads with different mass fractions increased the energy absorption capacity. Quasi‐static compression tests were carried out at room temperature to test the compression properties of epoxy resin/hollow microbead composites. The composites′ energy absorption properties and energy absorption efficiency were analyzed and calculated using the obtained compression curves. The fracture characteristics and microscopic morphology of the composite specimens were observed by scanning electron microscopy. It was found that aluminum oxide hollow microbeads, as reinforcement material, can effectively improve the brittleness and yield strength of epoxy resin materials and enhance the energy absorption performance and energy absorption efficiency of composite materials. With the increase in the mass fraction of hollow microbeads, the energy absorption performance of the composite material first increases and then decreases. Its performance is the most significant when the mass fraction of aluminum oxide hollow microbeads is 10 %.

Enhancing the mechanical properties of flax fiber-reinforced epoxy composites through cellulose nanofiber incorporation

Cellulose nanofibers (CNFs) have attracted significant attention as effective reinforcements for polymer composites because of their outstanding mechanical and structural properties. This study explored the incorporation of CNFs into flax fiber reinforced epoxy composites to enhance their overall performance. To overcome the challenges of CNFs dispersion, an innovative approach was developed in which CNFs were preloaded onto flax fabrics before resin infusion using vacuum assisted resin transfer molding (VARTM) method. The morphological, mechanical, structural and thermal properties of the composites were comprehensively evaluated for various CNFs loadings (0.1, 0.3, and 0.5 wt%). Remarkably, a 0.3 wt% CNFs loading was found to significantly optimize the composite's Young's modulus, achieving a notable improvement of 204.02 %. This study underscores the potential of CNFs enhanced flax fabric composites for developing high-performance sustainable materials suitable for wide range of technical applications.

Effect of titanium oxide nano‐filler on mechanical and sliding wear properties of hairy cotton grass fibre reinforced epoxy composites

AbstractThis study explores the synergistic influence of hybridizing titanium oxide (TiO2) filler on the mechanical properties and sliding wear behavior of epoxy composites reinforced with hairy cotton grass (HCG) fibres. The experimental results reveals that the combination with 9 wt‐% HCG/4 wt‐% titanium oxide observed better mechanical results (tensile‐51.03 MPa, flexural‐28.66 MPa, and impact energy‐3.1 J) whereas higher hardness (40.77 HV) achieved at 9 wt‐% hairy cotton grass/6 wt‐% titanium oxide composites. There is deterioration in mechanical results at higher titanium oxide (6 wt‐%) loading due to uneven distribution and particle agglomeration in hairy cotton grass‐epoxy composites. The design of expert was generated by using control parameters, sliding velocity (1 m ⋅ s−1–4 m ⋅ s−1), TiO2 content (0 wt‐%–6 wt‐%), and normal load (15 N–30 N) respectively. The optimization of the sliding wear rate was analysed by the Taguchi approach followed by an analysis of variance used for evaluating the significant of control parameters. The results showed a combination with significance sliding velocity of 1 ms−1 (78.15 %)>titanium oxide content of 6 wt‐% (20.28 %) >normal load of 30 N (1.57 %) exhibited an optimum value of specific wear rate.

A statistical approach to predict flexural strength and flame retardation properties for natural fibre/ epoxy composites

This research investigates the development of a mathematical model to predict the influence of flame retardants (FR) on the mechanical and flame retardancy performance of natural fibre reinforced thermosetting composites. The study focuses on two types of FRs: Diammonium Phosphate (DAP) and silica fumes that were added to Jute reinforced epoxy composites (JRECs). Two mathematical models were established based on three variables and two measured responses. The variables include FRs type, FR content, and FR method of preparation, while the measured responses are Limiting oxygen index (LOI) and Flexural strength (FS). The models were developed using a statistical approach based on multiple linear regression fitting and validated using analysis of variance (ANOVA) technique. The developed models were verified using experimental result data from literature and the analysis of these models showed that the maximum discrepancy between the observed and predicted values for relative LOI and relative FS was within the range of [Formula: see text] 6% and [Formula: see text] 5%, respectively. This research contributes to the understanding of the impact of FRs on the mechanical and flame retardancy performance of natural fibre reinforced thermosetting composites, which can aid in the design and development of safer and more efficient composite materials.

Synthesis, characterization and mechanical properties evaluation of muntingia calabura fibre reinforced epoxy composites: Fibre treatment comparison with NaOH and KOH

Numerous studies demonstrate that the alteration in the fibre surface caused by the alkali treatment enhances the mechanical capabilities. Muntingia calabura is the novel fibre was used in the present study. The present work illustrates the mechanical and characterization of NaOH and KOH treated muntingia calabura fibre reinforced epoxy composites. Muntingia calabura fibre is extracted from the bark of muntingia calabura plant. The collected fibres are treated with 10% alkali solution and then fibre–epoxy composites are fabricated with different fibre loadings, evaluated the mechanical properties of the Muntingia calabura fibre–epoxy composites. The interfacial bonding between the Muntingia calabura fibre and epoxy (LY-5052) observed with the morphological study. Using thermo gravimetric and infrared spectroscopy, the degradation behaviour and thermal stability of the Muntingia calabura fibre composites and the functional chemicals included in them are investigated respectively. The composites exhibit maximum tensile and flexural strengths of 84 MPa and 185 MPa, respectively, at 20 weight percent of the fibre content treated with NaOH. At 15 weight percent of the fibre content treated with NaOH, the composites have a maximum impact strength of 19.5 J/m2. It was found that the thermal stability of fibre composites treated with KOH and NaOH ranged from 250 to 400 degrees Celsius.

Investigation of mechanical properties of terminalia arjuna and moringa oleifera fiber reinforced epoxy composite

Investigation of mechanical properties of terminalia arjuna and moringa oleifera fiber reinforced epoxy composite

Hygrothermal aging on the mechanical property and degradation mechanism of carbon fiber reinforced epoxy composites modified by nylon 6

Nylon 6 (PA6) with excellent fracture toughness and hygrothermal resistance is added to the high-strength/modulus carbon fiber reinforced epoxy resin as a filler, which is expected to signally improve the thermal and mechanical properties. In the present paper, epoxy resin was reinforced by short carbon fibers and PA6 fillers of different content, and nylon 6 modified carbon fiber-epoxy resin (PA6CFEP) composite was successfully prepared. Water absorption behavior, thermal and mechanical performance evolution, degradation mechanism, as well as micro-structure and micro-morphology analysis of PA6CFEP before and after hygrothermal aging at 20/40/60 °C for 120 days were discussed and analyzed. The results showed that the water absorption law of PA6CFEP immersed in water solution accorded with the modified Fick's diffusion model, and the quasi-equilibrium water absorption (M∞) was 3.49%. Additionally, the maximum water absorption (Mmax) and diffusion coefficient (D) of the sample at 60 °C increased by 45.98% and 6.39% compared with those at 20 °C. Based on the optimal PA6 content (7.5 wt%), the fracture toughness of PA6CFEP-7.5 was 198.6% higher than that of the control sample, which was an increase in tensile strength (34.0%) and elongation at break (77.3%). Furthermore, the PA6 addition increased the Tg of PA6CFEP by a maximum percentage of 4.9%, which indicated that PA6 had excellent thermodynamic compatibility with the epoxy resin. After hygrothermal aging of PA6CFEP-7.5 for 120 days at 60 °C, the tensile strength, bending strength and Tg decreased by 36.5%, 38.3% and 16.9% compared to the control samples. This was because water molecules had the etching effect on the polymer chain of the resin, eventually led to the resin hydrolysis and filler/resin interface de-bonding. Finally, the fundamental reason for the degradation of the thermal and mechanical properties of PA6CFEP was that water molecules formed new hydrogen bonds (maximum increase 62.9%) with polymer chains and PA6 fillers, destroying the original cross-linking density of resin in the hygrothermal aging process. The water molecules infiltrated the available space of the resin matrix, leading to a reduction in the inter-chain force of the resin molecules.

Study on enhancing mechanical and thermal properties of carbon fiber reinforced epoxy composite through zinc oxide nanofiller

This study investigates the enhancement of mechanical and thermal properties of carbon fiber reinforced epoxy composites by incorporating zinc oxide (ZnO) nanofillers. The composites were developed by adding 3–15 g of ZnO nanoparticles into the epoxy matrix and were evaluated through experimental testing. The results showed significant improvements in mechanical performance, with the maximum tensile strength of 112.49 MPa and flexural strength of 114.82 MPa at the 15 g ZnO concentration. SEM analysis revealed a reduction in void content and improved fiber-matrix adhesion, enhancing load transfer. Thermal conductivity is 13.47 W/mK, while the coefficient of linear thermal expansion is 9.29 × 10−5/°C, indicating superior thermal stability. TGA analysis demonstrated a shift in decomposition temperature from 310 to 375 °C, confirming enhanced thermal stability. These results highlight the positive influence of ZnO nanofillers on both the mechanical and thermal properties of carbon fiber reinforced epoxy composites, making them more suitable for advanced structural applications.

A novel phosphorus/boron-containing flame retardant for improving the flame retardancy of ramie fiber reinforced epoxy composites

As a kind of plant fiber, ramie fibers (RFs) are widely used in fiber reinforced resin matrix composites, however, both of RFs and resin matrix are flammable. Enhancing the flame retardancy of ramie fiber reinforced epoxy composites is important. In this study, a highly efficient flame retardant, PBXY, was synthesized from phytic acid, boric acid, and xylitol to improve the flame retardancy of ramie fibers, and flame-retardant ramie fiber reinforced epoxy composites (EP/RF-PBXYs) with different weight gain were prepared by coating PBXY on the surface of ramie fibers. The effects of different weight gain of PBXY on the thermal stability, flame retardancy, and mechanical properties of EP/RF-PBXYs were investigated. Compared with that of EP/RF, the limiting oxygen index value of EP/RF-PBXY2 was increased from 23.0 % to 31.4 % and a UL-94 V-0 rating was obtained, the total heat release and total smoke production were reduced by 33.2 % and 31.0 %. However, the presence of PBXY had a negative effect on the mechanical properties of EP/RF when the weight gain of PBXY was more than 10 wt% (related to RFs). This study offers a promising avenue to improve the flame-retardant resistance of EP/RF.

Compressive behaviors and deformation mechanism of carbon fiber reinforced epoxy composites: A microscopic and molecular dynamics perspective

AbstractInvestigating the macro‐mechanical properties of polymer composites at the nanoscale is a challenging topic. Here we report the compressive performances of carbon fiber‐reinforced epoxy composites using molecular dynamics (MD) simulations. The evolution of microstructure and microscopic energy, including free volume, radius of gyration, dihedral angle, potential energy, and interaction energy, has been investigated to characterize compressive behaviors at the nanoscale. Molecular chains gradually bend, and the movement space of the molecular chains decreases during compression loading. The radius of gyration and dihedral angle are deformed into a state of irreversible plasticity to accommodate the microstructural transformation. The interaction energy increases and subsequently declines as the carbon fiber/epoxy interface gets closer, reflecting the transition of the internal structure. The inhomogeneity and interfacial concentration distribution of stress, and local molecular stiffness under various strains have been obtained to reveal the nanoscopic mechanism of epoxy failure and interface delamination during compression. This study reveals the compression behaviors and deformation mechanism of carbon fiber‐reinforced epoxy composites at the molecular level, providing directions and possibilities for molecular design and structural optimization of composites.Highlights The nanoscopic compression deformation of CFRP composites is studied. Microstructural evolution and conformation transformation are revealed. The evolution and transition of microscopic energy are analyzed. Micro‐mechanism of epoxy deformation and interface delamination is elucidated.

Enhancing directional thermal conductivity in hexagonal boron nitride reinforced epoxy composites through robust interfacial bonding

AbstractEstablishing a robust interfacial bond between hexagonal boron nitride (h‐BN) plates and the epoxy matrix is essential for enhancing heat transfer, which is difficult because of h‐BN's low‐surface energy, tendency to clump together, and the chemical inertness of the epoxy matrix. This research shows different techniques for treating the surface of h‐BN fillers by applying acids and thermal processes to activate the surface. The silanization process was used to increase the silane content on the surface of activated h‐BN in order to make it more compatible with the epoxy matrix. X‐ray photoelectron spectroscopy analysis revealed silicon peaks (Si2s peak at 150.1 eV and Si2p peak at 100.3 eV) in the spectrum of silane‐treated samples. Heat treatment resulted in the production of more oxygen molecules on the shell of h‐BN compared to the acid treatment. Here, the primary focus was on examining how surface treatment affects thermal conductivity (TC) performance in both in‐plane and through‐thickness paths. There was an increase in the epoxy's TC perpendicular to the plane, going from 0.21 to 0.47 (W/mK), showing a remarkable 123.8% enhancement by adding 10 wt% of silane‐modified‐thermal treated h‐BN particles. The improvement resulted from effectively silanizing the exterior boundary of h‐BN particles, enhancing connection and distribution in the epoxy matrix. Surface modification of h‐BN‐epoxy composites improves TC, leading to better heat conduction in thermal management systems, benefiting industries like aerospace, automotive, and energy systems.Highlights Silanization of h‐BN for better filler‐matrix bonding leading to improved heat transfer Boosting thermal conductivity in the through‐thickness direction with surface‐modified h‐BN Significant improvement in through‐thickness thermal conductivity with treated h‐BN. Thermal treatment of h‐BN produced better oxygenation than acid treatment. Application in aerospace and automotive through improved heat transfer.

Multi-scale fatigue damage analysis in filament-wound carbon fiber reinforced epoxy composites for hydrogen storage tanks

This article presents the findings of a multi-scale experimental study on carbon fiber-reinforced epoxy composites (CFRP) used in lightweight hydrogen storage pressure vessels produced via filament winding. The research employs a combination of tension-tension load-controlled fatigue tests and high-resolution physical-chemical characterization and porosity quantification to assess the impact of porosity on mechanical performance. The findings demonstrate that porosity has a detrimental impact on mechanical properties, acting as nucleation sites for damage mechanisms such as crack initiation, fiber-matrix separation and fiber breakage. At the mesoscopic level, microdefects coalesce into transverse cracks and delamination, resulting in complex failure modes under cyclic loading. The results of the tensile tests demonstrated that the orientation of the fibers has a significant impact on the mechanical behavior of the material. The ±15° configuration demonstrated superior tensile strength and modulus, while the ±30° and multilayer configurations exhibited higher ductility. The results of the fatigue testing confirmed that fiber orientation has a significant impact on fatigue life, with the ±15° configuration proving to be the most resistant. Microscopic analysis indicated that pores act as damage initiation points, accelerating failure through matrix cracking, fiber-matrix debonding, and delamination. This study highlights the need for improved porosity control during manufacturing to enhance the durability of hydrogen storage systems. Additionally, it provides valuable insights for optimizing fiber orientation to improve fatigue performance in practical applications.

Investigation on the mechanical, water absorption, and tribological performance of calotropis gigantea and abaca fiber reinforced epoxy composites

Investigation on the mechanical, water absorption, and tribological performance of calotropis gigantea and abaca fiber reinforced epoxy composites

Experimental characterization of hemp woven fabric reinforced epoxy resin composites produced without heat treatment

Experimental characterization of hemp woven fabric reinforced epoxy resin composites produced without heat treatment