Fiber-reinforced Epoxy Research Articles

Efficient degradation of amine cured epoxy resin via the cleavage of C-N bond by amphiphilic dodecylbenzenesulfonic acid

Amine-cured epoxy resin (EP) is often compounded with carbon fiber (CF) used for wind power blades due to its excellent performance. However, the insolubility and infusibility of service-life-expired carbon fiber reinforced epoxy resin (CFREP) hinder its sustainable recycling. We reported a new strategy for efficient degradation of EP and CFREP with 0.5 mol% amphiphilic dodecylbenzenesulfonic acid (DBSA) in aqueous system. It was found that the strong lipophilicity of DBSA accelerated its enrichment on EP surface, and further promoted the diffusion of DBSA and H2O to the resin bulk phase. As a result, the degradation ratio of the EP powder reached 100 % at 190 °C only in 10 h. The characterization of FT-IR and NMR proved that the degradation mechanism of EP was the selective cleavage of C-N bond catalyzed by H+. The resin degradation products (RDP) containing active hydrogen were used to prepare polyurethane (PU) with good mechanical properties. This method achieves complete recycling of waste CFREP in aqueous systems.

POSS-polyurethane prepolymer strengthened and toughened CF/epoxy resin composites for room and simulated Arctic ambient temperature

As an important material candidate for automotive, aviation, and aerospace, the wide application of carbon fiber-reinforced epoxy resin composites (CFRPs) was important. However, restricted by the low toughness. Herein, octaaminopropyl cage polysilsesquioxane-polyurethane prepolymer (POSS-PU) was synthesized by in-situ polymerization of PU on the POSS, and then employed as the modifier for epoxy resin (EP). Compared to pristine EP, the toughness of the 7.5 wt% POSS0.5-PU/EP was increased by 115.3 % without compromising the tensile strength and Tg. The unnotched impact strength, interlaminar shear strength (ILSS), and flexural strength of the CFRPs prepared from the modified EP were increased by 73.5 %, 7.5 %, and 42.4 %, compared to CF/EP. Additionally, the mechanical properties of CFRPs maintained a substantial improvement under low-temperature, and the CF/7.5 wt% POSS0.5-PU/EP was increased by 72.9 % (impact strength) and 21.7 % (ILSS), compared to those of CF/EP. Compared to the improvement in the toughness of CFRPs at room temperature, the retention rate of toughness enhancement at low temperature was approximately 100 %. CFRPs prepared by POSSx-PU/EP offered outstanding mechanical properties and hence showed great potential for future industrial applications.

Mechanical and Tribological Behavior of Graphene Oxide Supported Aramid Fiber Reinforced Epoxy Resin

Mechanical and Tribological Behavior of Graphene Oxide Supported Aramid Fiber Reinforced Epoxy Resin

Армированные композитные материалы на основе фосфорсодержащих связующих с перспективными физико-механическими и пожаробезопасными свойствами

In this work, a comparative analysis of the properties of glass fiber-reinforced epoxy resin (ED-20) composites and composites based on glass fiber-reinforced phosphorus-containing ester methacrylate oligomers (PEAO) was carried out. Reinforced fiberglass plastics made on the basis of PEAO have demonstrated promising fireproof characteristics, especially in limited oxygen index and smoke emission tests. It is also worth noting that the mechanical properties of materials based on phosphorus-containing ester-acrylate resins are outstanding. The samples of a widely used glass fiber reinforced epoxy resin ED-20 with 9,10-dihydro-9-hydroxy-10-phosphaphenanthrene-10-oxide-4,4`-diaminodiphenylmethane (DDM-DOPO) additive demonstrated lower flammability compared to the samples without fire retardant additives. A mixture of DDM-DOPO and graphene added to the samples led to a low smoke generation rate of the samples; however, the rate was 1.5-2 times higher than that of the samples based on phosphorus-containing ester methacrylate resins. The addition of fire retardants has reduced the mechanical properties of fiberglass plastics based on epoxy resin, which can be a problem for the use of these materials in the aviation industry. These results clearly show better prospects of using fiberglass-reinforced plastics based on phosphorus-containing ester methacrylate oligomers in comparison with modified plastics based on the widely used epoxy resin.

GO-tagged PEI sizing agent imparts self-healing and excellent mechanical properties to carbon fiber reinforced epoxy laminates.

Carbon fiber-reinforced epoxy (CFRE) laminates have attracted significant attention as a structural material specifically in the aerospace industry. In recent times, various strategies have been developed to modify the carbon fiber (CF) surface as the interface between the epoxy matrix and CFs plays a pivotal role in determining the overall performance of CFRE laminates. In the present work, graphene oxide (GO) was used to tag a polyetherimide (PEI, termed BA) containing exchangeable bonds and was employed as a sizing agent to improve the interfacial adhesion between CFs and epoxy. This unique GO-tagged-BA sizing agent termed BAGO significantly enhanced the mechanical properties of CFRE laminates by promoting stronger interactions between CFs and the epoxy matrix. The successful synthesis of BAGO was verified by Fourier-transform infrared spectroscopy. Additionally, the partial reduction of GO owing to this tagging with BA was further confirmed by X-ray diffraction and Raman spectroscopy, and the thermal stability of this unique sizing agent was evaluated using thermogravimetric analysis. The amount of GO in BAGO was optimized as 0.25 wt% of BA termed 0.25-BAGO. The 0.25-BAGO sizing agent resulted in a significant increase in surface roughness, from 15 nm to 140 nm, and surface energy, from 13.2 to 34.7 mN m-1 of CF. The laminates prepared from 0.25-BAGO exhibited a remarkable 40% increase in flexural strength (FS) and a 35% increase in interlaminar shear strength (ILSS) due to interfacial strengthening between epoxy and CFs. In addition, these laminates exhibited a self-healing efficiency of 51% in ILSS due to the presence of dynamic disulfide bonds in BAGO. Interestingly, the laminates with 0.25-BAGO exhibited enhanced Joule heating and enhanced deicing, though the EMI shielding efficiency slightly declined.

Processing and characterization of flame-retardant natural fibre-reinforced epoxy composites and construction of selection charts for engineering applications

Processing and characterization of flame-retardant natural fibre-reinforced epoxy composites and construction of selection charts for engineering applications

Effect of tapered natural fiber on elastic properties of sisal fiber-reinforced composite: An experimental and micromechanics approach

In the characterization of natural fiber-reinforced composites, it is crucial to consider the nonuniform cross-section of fibers extracted from plants or leaves, which results from the inherent variation in fiber diameter. This variation is a key aspect of the actual reinforcement behavior, and disregarding it by assuming a uniform cross-section can violate the physical understanding of the composite’s mechanics. This study focuses on characterizing the elastic properties of a natural tapered sisal fiber-reinforced epoxy composite, taking into account the variation in fiber diameter along its length. To achieve this, both experimental, analytical, and micromechanics methods are employed. The experimental approach involves conducting tests to measure the mechanical properties of the composite, while the micromechanics analysis provides a framework to understand the reinforcement behavior and predict the composite’s mechanical response. The study aims to identify and present various elastic properties of the composite, including the longitudinal modulus, transverse modulus, in-plane and out-of-plane shear modulus, and major and minor Poisson’s ratios. The fiber taper angle has a significant effect on longitudinal and transverse modulus and interfacial stresses. The longitudinal modulus experiences a reduction of 25.9% when increasing the taper angle from [Formula: see text] to [Formula: see text] at a higher fiber volume fraction (40%). However, at a lower volume fraction of the same fiber (10%), the reduction in modulus is limited to 5.74%. Similarly, the transverse modulus is also affected by the taper angle. At the higher fiber volume fraction, there is a decrease of 24.52%, whereas at the lower volume fraction and higher taper angle of the fiber, the decrement is 4.94%.

Effects of Alkali Treatment on the Mechanical, Chemical, and Thermal Properties of Aramid and Grass Fiber-Reinforced Epoxy Hybrid Composites

Effects of Alkali Treatment on the Mechanical, Chemical, and Thermal Properties of Aramid and Grass Fiber-Reinforced Epoxy Hybrid Composites

Elastic properties evaluation of banana-hemp fiber-based hybrid composite with nano-titanium oxide filler: Analytical and Simulation Study

In recent years, nano-filler-based hybrid composites have gained significant attention from the research community; The nano-filler-based hybrid composites can have potential applications in numerous sectors. Nano-fillers are bringing a leading development in material science and natural fibers-based composites. The present study considers the impact of various weight percentages of nano-titanium oxide (NTiO2) fillers (2%, 4%, and 6%) on the elastic features of novel hybridized banana-hemp fiber-reinforced epoxy composites. The proposed composite is analyzed for its elastic properties like longitudinal and transverse elastic modulus, axial Poisson's ratio, and axial shear modulus using homogenized micromechanical models, namely, Mori-Tanaka (M-T) model, Generalized self-consistent (G-SC) model and Modified Halpin-Tsai (M-HTS) model. The composite is modeled using one layer of banana fiber, one layer of NTiO2 and epoxy, and one layer of hemp fiber. All three layers of the composite are arranged in the sequence of banana fiber at 450, a layer of NTiO2 and epoxy at 00, and hemp fiber at 450. The proposed composite's vector sum deformation and strength are examined by employing the ANSYS APDL application. The results obtained in this study are compared with the experimental work mentioned in the literature. The composite reinforced with six weight% NTiO2 has the highest mechanical strength, and the modified Halpin-Tsai (M-HTS) model is the most effective in calculating the elastic features of the proposed composite. In addition to the above, the hybridization effect for the proposed composite is also estimated to analyze the tensile failure strain of banana and hemp fiber in the proposed hybrid composite structure.

Exploring the Mechanical Properties and Water Absorption Behavior of Keratin Fiber-Reinforced Epoxy Composites: Insights into Sustainable Manufacturing

Exploring the Mechanical Properties and Water Absorption Behavior of Keratin Fiber-Reinforced Epoxy Composites: Insights into Sustainable Manufacturing

Mechanical and Tribological Properties of Carbon Fiber/Glass Fiber-Reinforced Epoxy Hybrid Composites Filled with Al2O3 Particles

In this study, we produced Aluminum oxide (Al2O3) reinforced carbon fiber and glass fiber reinforced polymer (CFRP, GFRP) composites and investigated mechanical and tribological properties. Al2O3 was dispersed in epoxy resin using a mechanical stirrer. The composites are produced via the hand lay-up method and dried at room temperature for 48 hours. The properties of composites were determined via Archimedes’ method, flexural, impact, hardness and wear tests. The highest flexural strength and hardness were found at 946.3 MPa and 48.7 HBA for 3 wt.% Al2O3 reinforced CFRP, respectively. The highest impact strength was observed at 187.4 kJ/m2 for an un-reinforced GFRP composite. The lowest Coefficient of Friction (COF) and wear depth was found 3 wt.% Al2O3 reinforced GFRP composites.

Analysis and Development of Military Helmet Using Date Palm Fibre Reinforced Epoxy Composite

The study discusses on analysis, fabrication and characterization of military helmet using date palm fibre reinforced with epoxy. The study is aimed at identifying the possibility of using the locally available material such as date palm fibre for the production of military protective helmet. Composite plates were prepared using Date palm fibre (DFE) reinforced with epoxy with varying composition. Six samples were produced and cut into the required size and shape for testing mechanical properties (impact strength ASTM D-156, Hardness ASTM D-2240, tensile strength ASTM D-638 and flexural strength ASTM D-790) of the material. Based on the result obtained, sample label S3 has 20% DFE and 80% epoxy has the highest impact strength of 0.225 J/mm2, hardness 70 Hv, tensile strength 25.87 N/mm2 and flexural strength. The scan electron microscopy (SEM) was carried on the selected sample in which voids were observed in the image which could be instrumental to air trapped in the composite during mixing which might have escaped during curing at high temperature living the void in the sample. The helmet was produced using the selected sample with a thickness of 8mm while that of Daungkumsawat, et al (2020) has a thickness of 6.94mm

A facile and efficient solvothermal degradation route for carbon fiber reinforced epoxy resin composite waste

Carbon fiber reinforced epoxy resin composite (CF/EP) is widely used in aerospace applications, automotive industry, construction engineering and many other important sectors, for it has excellent mechanical properties and corrosion resistance. However, the three-dimensional cross-linked structure of the cured epoxy resin determines its insolubility and non-melting characteristics, which makes it challenging to efficiently degrade CF/EP waste and recycle the high-value carbon fibers. In this study we propose a strategy that degrades the CF/EP waste via a facile and efficient solvothermal degradation route. The results showed that the degradation ratio of the resin increased significantly with the rise in reaction temperature. When the reaction temperature reached 180 °C there were no obvious resin residues on the surface of the recycled carbon fibers. It was found that the recycled carbon fibers were not obviously damaged during the solvothermal degradation process, as shown by the scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman analyses.

Experimental and simulation study on surface material stripping of glass fiber reinforced composites by baking soda abrasive jetting technology

Glass fiber reinforced composites (GFRP) working in a specific environment require regular inspection and maintenance. It is necessary to remove the surface material of fiber reinforced composites to check the fracture of fibers and the damage to matrix that binds fibers in this process. In this paper, the baking soda abrasive jetting was utilized to strip the surface material of glass fiber reinforced epoxy resin (GFREP). The stripping effects of baking soda abrasive jetting technology under different jetting parameters (fiber orientation, jet angle, jet pressure) were explored, and the optimum stripping conditions were determined as parallel to the fiber, 30°, 0.4 MPa. Compared with the chemical stripping method (phenol-dichloromethane), baking soda abrasive jetting can better retain epoxy resin between glass fibers. The LS-DYNA was applied to simulate the erosion process of a single abrasive particle under the optimum stripping condition. The plastic deformation of the matrix and the slight bending deformation of the glass fiber under abrasive impact were observed.

Dynamic characterization and damage analysis for the thermoplastic fiber-reinforced epoxy composites exposed to repeated low velocity impact

In the current study, contrary to conventional fiber-reinforced composites, polyamide fiber was used as reinforcement material, and the effects of thermoplastic fiber reinforcement on repeated low velocity impact (LVI) responses of composites were examined. In this regard, polyamide fiber-reinforced composites were fabricated using the vacuum-assisted hand lay-up method (VAHLM) and then exposed to repeated LVI loadings. Experimental tests were performed on the specimens for 100 impacts with a constant velocity of 3 m/s, which is equivalent to 25.2 J, and the impacts of repeated LVI loadings on the dynamic responses such as peak force, energy absorbing/rebounding, total impulse, bending stiffness and contact stiffness were examined. Moreover, the damage mechanisms resulting from the relative damage accumulation depending on the impact numbers were examined. According to the findings, the thermoplastic polyamide fibers absorbed more than 60% of the applied energy, and the absorbed energy increased with ascending impact number. Furthermore, the thermoplastic fiber-reinforced epoxy composites gained stiffness with increasing impact, which was linked to the thermoplastic chain structure. Despite quite a number of impact loadings, no serious damage mechanisms such as fiber breakage, perforation, or penetration were observed, and the specimens maintained their structural integrity. Due to the higher energy absorption of thermoplastics, the utilization of polyamide fibers in composites has been found to be well suited for applications subjected to repeated impacts.

Investigation of failure behavior of glass fiber reinforced epoxy laminate under fatigue loading

Purpose This study aims to evaluate the failure behavior of glass fiber-reinforced epoxy (GFRE) laminate subjected to cyclic loading conditions. It involves experimental investigation and statistical analysis using Weibull distribution to characterize the failure behavior of the GFRE composite laminate. Design/methodology/approach Fatigue tests were conducted using a tension–tension loading scheme at a frequency of 2 Hz and a loading ratio (R) of 0.1. The tests were performed at five different stress levels, corresponding to 50%–90% of the ultimate tensile strength (UTS). Failure behavior was assessed through cyclic stress-strain hysteresis plots, dynamic modulus behavior and scanning electron microscopy (SEM) analysis of fracture surfaces. Findings The study identified common modes of failure, including fiber pullouts, fiber breakage and matrix cracking. At low stress levels, fiber breakage, matrix cracking and fiber pullouts occurred due to high shear stresses at the fiber–matrix interface. Conversely, at high stress levels, fiber breakage and matrix cracking predominated. Higher stress levels led to larger stress-strain hysteresis loops, indicating increased energy dissipation during cyclic loading. High stress levels were associated with a more significant decrease in stiffness over time, implying a shorter fatigue life, while lower stress levels resulted in a gradual decline in stiffness, leading to extended fatigue life. Originality/value This study makes a valuable contribution to understanding fatigue behavior under tension–tension loading conditions, coupled with an in-depth analysis of the failure mechanism in GFRE composite laminate at different stress levels. The fatigue behavior is scrutinized through stress-strain hysteresis plots and dynamic modulus versus normalized cycles plots. Furthermore, the characterization of the failure mechanism is enhanced by using SEM imaging of fractured specimens. The Weibull distribution approach is used to obtain a reliable estimate of fatigue life.

Damage accumulation and failure mechanism of glass/epoxy composite laminates subjected to repeated low velocity impacts

Abstract In this work, the damage accumulation and failure mechanism of glass fiber-reinforced epoxy composite laminates under repeated low velocity impacts were studied considering the influence of stacking sequence. The typical sandwich-like [0°2/90°2]s, angle-ply [±45°]2s and quasi-isotropic [0°/−45°/45°/90°]s laminates were tested at 20 J impact energy. The impact responses including contact force–time/central displacement and energy–time curves were recorded. The tendencies of the peak contact force, maximum displacement, bending stiffness, and energy dissipation with the increase in impact number were analyzed. Damage induced in the laminates was further evaluated. The results show that the impact resistance of the sandwich-like laminate is the weakest with the lowest peak load and the highest energy dissipation. The impact resistance of the quasi-isotropic laminate is better relative to the angle-ply laminate before the occurrence of fiber breakage, whereas the damage tolerance of the angle-ply laminate is higher with relatively slower damage accumulation at subsequent impacts.

Mechanical and thermo-mechanical behaviors of snake grass fiber-reinforced epoxy composite

Snake grass fiber was used as a supporting material in an epoxy matrix. The goal was to develop a lightweight structural material. To enhance the interfacial bonding between the snake grass (Sansevieria ehrenbergii) fiber and polymer matrices, the fiber underwent chemical treatment with NaOH. Samples were prepared with both neat and treated fibers mixed with epoxy at various volume percentages. The mechanical properties of snake grass fiber exhibited improvement with increasing fiber length and fixation, reaching optimal values at 20 mm length and 20% v/v fixation. Dynamic mechanical analysis (DMA) demonstrated superior energy absorption by the composite up to 140 °C, irrespective of repetition. Thermogravimetric analysis (TGA) indicated rapid degradation of untreated fiber with a residue level of 0.2%, while the snake grass composite (25% v/v) exhibited stable residue content at 11%. Microscopic evaluation using a scanning electron microscope provided insights into the morphology of the fiber surface.

Degradation behavior and ageing mechanism of E-glass fiber reinforced epoxy resin composite pipes under accelerated thermal ageing conditions

In this work, accelerated ageing experiments with circulating air and simulated oilfield water were carried out at 95 °C on aromatic amine-cured GFRP pipes used in oilfield environments, with effective ageing times of 5000 h and 3000 h respectively. The differences in ageing behavior and ageing mechanisms of the GFRP tubes at different times under the two conditions were then analyzed and discussed. The changes in the apparent morphology and microstructure of the samples after thermal ageing were first observed using optical microscopy and scanning electron microscopy, and the results demonstrated that the thermal oxygen environment triggered more drastic color changes and obvious oxidation layers. The resin matrix manifests a large number of nano-scale micropores and modest matrix shrinkage pores in the micron size range, this is accompanied by damage to the fiber cross-section. Hydrothermal ageing causes further dissolution of the surface resin and dissolution of the exposed fibers. ATR-FTIR analysis verifies the increase in CO bonding of the ester group during thermal oxidation and the decreasing strength of the C–O–C and C–H bonds, while the behavior of ageing water absorption and glass fiber hydrolysis is illustrated by changes in the intensity of the –OH and Si–O characteristic bands. NMR hydrogen spectroscopy verified the formation of amides, methyl ethers and carboxylic acids in the thermal oxidation products of epoxy resins. Furthermore, the decay pattern of the circumferential tensile strength indicates that the hydrothermal environment has a more significant effect on the mechanical properties of GFRP pipes, which is attributed to the physical dissolution of the surface resin, significant hydrolytic damage to the surface exposed fibers, and the combined damage to the resin-fiber interfacial bonding by chloride ions in simulated oilfield water.

Continuum Mechanics Models for Describing the Creep and Physical Aging Behaviors of Laminated Composites

Two types of carbon fiber-reinforced epoxy composite laminates are chosen for long-term tensile creep tests under different temperatures and load levels. Their time-dependent and non-monotonic deformations indicate clearly both temperature effect and physical aging effect. To characterize these viscoelastic behavior, two phenomenological constitutive models and one physical model are developed. The linear viscoelastic model based on the Boltzmann superposition principle is able to describe reasonably the deformations at relatively lower stress levels and temperatures. The nonlinear viscoelastic model of Schapery’s single-integral form, together with a usage of effective time theory, could describe nicely all the effects of temperature, stress, and physical aging. The physical model based on Ngai’s coupling mechanism concept is further combined with the framework of Schapery’s nonlinear viscoelastic theory, which may provide certain physical understanding about the effect of aging behavior on long-term creep deformation of the laminated composites. Numerical modelling by finite element method are implemented, and comparisons between the experimental and simulation results are demonstrated.