Fiber Reinforced Epoxy Composite Laminates Research Articles

Mechanical Properties of Basalt / Chopped E-Glass Fiber and Graphite Powder Reinforced Hybrid Composites

In the current investigation an effort has put to study the effect of E-glass chopped mat and graphite powder in variations of 5g, 10g, and 15g on the tensile and flexural behavior of a basalt fiber-reinforced epoxy composite laminate reinforced with E-Glass fiber and Graphite powder. Hand layup technique has been used for the fabrication of the composites. Tensile, flexural, impact, and hardness tests were done on the Basalt/E-glass/Graphite epoxy composite in accordance with ASTM standards. The results indicate significant improvement in tensile strength, impact strength and hardness when E-glass was incorporated in the basalt/epoxy composite. However, basalt/E-glass/10% graphite epoxy composite was shown to have a greater flexural strength. An excellent dispersion of the reinforcements in the polymeric matrix, which elevated surface area for solid interfacial contact and effective load transmission, could possibly be accountable for the improved performance of the laminates that were successfully developed.

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.

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.

High‐velocity ballistic response of AA 1100‐H14 based carbon‐fiber metal laminates: An experimental investigation

AbstractA detailed experimental investigation was carried out for the high‐velocity ballistic response of AA 1100‐H14 based carbon‐fiber metal laminates (FMLs). FMLs with different metal volume fractions and the same thickness of carbon‐epoxy fiber laminates were tested to examine the surface and internal damage. The ballistic performance parameters, namely % escalation in absorbed energy, specific energy absorbed, ballistic limit, specific perforation energy, first cracking energy, and global deformation profile, were studied and a comparison was drawn with pure carbons fiber reinforced epoxy composite laminates. Despite having greater thickness, pure carbon fiber‐reinforced epoxy composite laminates absorbed less impact energy than FMLs and failed catastrophically. For FMLs, the % escalation in the absorbed energy and the specific energy absorption kept increasing with the increasing impact velocity until the onset of perforation. Once the perforation started, both these parameters showed a decreasing trend. Thick FMLs absorbed a good amount of energy, leading to projectile recoil suffering minimal damage. The ballistic velocity, specific perforation energy, and first cracking energy on the front and rear face of FMLs layers showed an increasing trend. The minimum for the thinner and maximum for the thicker FMLs attributed to the large thickness and more metal volume fraction. Contrary to the large deformation of the impacting points, pure carbon fiber‐reinforced epoxy composite laminates showed very minimal deformation as compared to FMLs. The brittle nature of the epoxy resin resisted the deformation to a large extent leading to less energy absorption.Highlights High‐velocity ballistic response of AA 1100‐H14 based carbon‐FMLs was investigated. Ballistic performance parameters of FMLs were studied and was compared with carbons fiber reinforced composite laminates. The ballistic limit of FMLs showed a direct dependence its thickness and metal volume fraction. In the absence of any metallic layer, pure carbons fiber reinforced composite laminates absorbed less impact energy.

High performance shape-adjustable structural lithium-ion battery based on hybrid fiber reinforced epoxy composite

High performance shape-adjustable structural batteries with both excellent electrochemical performances and mechanical properties, and compatible with conventional batteries and composite processing techniques, are highly attractive for next generation electrical vehicles and electrical aircrafts. Herein, a high-performance structural lithium-ion battery composite (SLBC) is developed by encapsulating commercial-available battery core materials with hybrid fiber reinforced epoxy composite laminate shells, which can be assembled into desired irregular shapes with the conventional vacuum bagging technique. Firstly, the laminate shell layout with the combination of glass fiber woven fabric (GFWF) and carbon fiber woven fabric (CFWF) is designed and optimized. Meanwhile, a PET film is employed to wrap the battery core materials, which enables processing of the SLBC with liquid electrolyte in ambient condition. The SLBC obtained demonstrates both prominent mechanical (flexural strength of 211.7 MPa and flexural modulus of 7.7 GPa) and electrochemical properties (an initial discharge capacity of 98.5 mAh/g at 0.2C, a high energy density of 314.5 Wh kg−1, and a good cycling performance) owing to the hybrid design of CFWF and GFWF as well as a sealed environment to guarantee the battery operate well. Impressively, the in-situ mechano-electrochemical measurements are assessed under the out-of-plane compressive stress and the flexural stress conditions. These results show that the SLBC under loading can maintain stable electrochemical performance even at a high out-of-plane compressive stress of 20 MPa and a high flexural stress of 150 MPa. Furthermore, the SLBC can also maintain the excellent discharge capacity when subjected to a high impact energy, which is promising in next generation electrical vehicles. Finally, the wave-like SLBC fabricated demonstrates the effectiveness in withstanding loads and driving electric fan simultaneously, which is promising in next generation electrical vehicles..

Effect of current intensity on properties of the carbon fiber fabric and composites

The carbon fiber fabric was electrified at the current intensities of 4 A for 1 h, 8 A for1 h, 16 A for 1 h and 16 A for 2 h, and then the carbon fiber reinforced epoxy composite laminates (CF/EP) were prepared. The effects of different current intensities on the surface temperature of the carbon fiber fabric, the micro morphology of the carbon fiber, the mechanical properties of CF/EP composites and the fracture morphology of the tensile specimens were studied. The significance of the effect of current intensities on the mechanical properties of CF/EP was investigated by means of quantitative statistical analysis. The results show that the maximum surface temperature of the carbon fiber fabric during heating is 115 °C ~125 °C; At significance level α= 0.01, the mechanical properties of CF/EP composites were not significantly affected by different current intensities; The surface micro morphology of the carbon fiber fabric treated with current intensity of 4 A for 1 h, 8 A for 1 h and 16 A for 1 h was not significantly different from that of untreated. After current intensity of 16 A for 2 h, the surface grooves were deepened and the surface granular protrusions were increased; No obvious difference was observed in the fracture morphology of samples with different current intensity. The results show that in the self heating process of carbon fiber composites, when the current intensity of single-layer carbon fiber fabric is less than 16 A and 2 h, it will have no significant impact on the properties of the composites.

Characterization of nonlinear viscoelastic behaviors of CF/EP laminates with consideration to physical aging effect under thermo-mechanical loading

The characterization of the time-dependent deformation of fiber-reinforced polymer laminates is critical when evaluating the reliability of composite structures over long-term service lifetime. Several isothermal tensile creep tests under different temperatures and mechanical load levels for two types of carbon fiber-reinforced epoxy composite laminates are conducted in this work. The results indicate that the composites deformed in a time-dependent way and their axial strains are non-monotonic, which implies that both the creep temperature effect and physical aging effect come into play and the creep deformation was affected by the physical aging within the range of loads and temperatures involved in the tests. To formulate this kind of time-dependent behavior, a phenomenological nonlinear viscoelastic constitutive model of single-integral form was proposed and the effective time theory was introduced to describe the effects of temperature, stress, and physical aging. The measured strain was departed into two parts, one is the creep strain and the other is caused by the physical aging effect. The model was implemented within a finite element software by employing a recursive-iterative algorithm and was verified by comparing the simulation results with the experimental ones.

Influence of MXene and carbon nanotube on the mechanical properties of sisal fibre/glass fibre reinforced epoxy composite laminates

The present experimental work investigates the influence of E-glass fiber hybridization on the tensile and bending characteristics of sisal fiber reinforced epoxy polymeric composite laminates. The bi-directional sisal fiber was treated with an alkali (NaOH) and laminated specimens were fabricated by using hand-layup method. Furthermore, the present investigation extends to explore the effect of introducing Carbon nanotube (CNT) and MXene (Ti3C2Tx) nanoparticles on the elastic behavior of glass-sisal fiber hybrid composites. The nano-fillers were dispersed and blended with the neat epoxy by using sonication method. The multiscale structure of the MXene dispersed hybrid plates were examined by using scanning electron microscopy. It was found that the tensile strength of the sisal/glass fibers laminate got enhanced by 42% upon reinforcing MXene. In addition, it was observed that the bending strength and bending modulus of sisal/glass fibers laminate was increased by 34% and 30% respectively, when using MXene nanoparticles were reinforced into the matrix. Based on the experimental results, it was inferred that the surface characteristics of the MXene and CNT nanoparticles play a significant role in improving the tensile and flexural properties of the sisal/fiberglass reinforced hybrid laminate.

Quantitative identification of damage in composite structures using sparse sensor arrays and multi-domain-feature fusion of guided waves

Damage detection techniques using Lamb waves have shown excellent capabilities in the diagnosis of composite structures. However, structural health monitoring of composite structures is challenging, especially for damage classification. This study proposes a machine learning-based method with a sparse sensor array to achieve quantitative classification of the damage location and severity on a composite plate. First, multi features extraction is used to construct a support vector machine (SVM) damage localization model. Second, optimal path extraction combined with principal component analysis (PCA) is used to construct an SVM model for classification. To reduce the operational burden of structures, the sparse array is employed. To improve the damage classification accuracy, Fisher clustering is proposed to extract the optimal detection path. Then, PCA is used to achieve data fusion. Experimental results on a glass fiber-reinforced epoxy composite laminate plate demonstrate that the proposed technique can accurately locate and classify the quantitative artificial damage.

Fiber bridging mechanism in moisture‐induced mode I delamination in carbon/epoxy composites: Finite element analysis and experimental investigation

AbstractProlonged exposure of fiber reinforced composite structures to high moisture and temperature in outdoor environment could lead to the degradation of mechanical properties of the materials. To provides reliable prediction of the delamination behavior as the moisture progressively ingresses into the composites, we proposed a Bilinear‐Exponential Traction‐Separation (BETS) law‐which can account for the fiber bridging mechanism‐for investigating the mode I delamination of unidirectional carbon fiber reinforced epoxy composite laminates in wet states. Finite element analysis (FEA) of the delamination model was conducted to evaluate the effects of moisture content on the global force‐displacement curves. A cohesive zone model (CZM) was used to describe the delamination behavior at the interface. With regard to the force‐displacement curves, the BETS law agrees well with results from experimental study (using the double cantilever beam testing on the wet specimens) at both the elastic and failure regions. The delamination model governed by the BETS law also showed good agreement with the crack length versus the crosshead displacement. The FE model that considered the inputs from the BETS law yielded prediction about the evolution of the damage parameter and crack growth profile. In particular, the predicted crack extension increases linearly with increasing crosshead displacement. The proposed BETS law has the advantage of not requiring crack growth monitoring during experiment, and only one fitting parameter was needed to describe the bridging law at different moisture content levels.

Effect of carbon nanotube surface treatment on the dynamic mechanical properties of a hybrid carbon/epoxy composite laminate

The objective of the current investigation is to evaluate the dynamic mechanical properties of a hybrid carbon fiber reinforced epoxy composite laminate containing CNT-rich interlayers, where the CNTs were prepared with ten different surface treatments and two different degrees of alignment. The surface treatments, including surfactants and oxidation, alter the CNT/epoxy stress transfer characteristics. Testing was done in uniaxial tension at different temperatures, loading frequencies and in dry and wet conditions. In the case of imperfectly aligned CNT yarn interlayers, the best surfactant, which was Triton X-100, increased the loss modulus by 182% over the baseline (no CNTs) and increased the storage modulus by 2.2%. Oxidation of the CNTs increased the loss modulus by 219% and the storage modulus by 2.3%, versus the baseline. Highly aligned CNT film provides higher loss modulus (+44%) and storage modulus (+8.4%) than imperfectly aligned CNT yarns, for the case of no surface treatment. Alignment of the CNTs also reduces the sensitivity of dynamic properties to temperature change and moisture content. CNT interlayers reduce the frequency dependency of the dynamic properties. Improvements in damping with surface treatments are hypothesized to be due to improved epoxy impregnation of the condensed CNTs.

Investigation of the effect of steel fiber (200 mesh size) hybridization on properties of steel/glass fiber and steel/basalt fiber reinforced epoxy composite laminates

AbstractSteel fiber is the most common metal fiber used due to its cost‐effectiveness, high performance, and availability despite its heavyweight. This study is an attempt to evaluate the mechanical properties of steel/glass fiber and steel/basalt fiber‐reinforced epoxy composites. The symmetric hybrid laminates were produced by replacing the innermost 1, 2, 3, and 4 layers of steel fiber (200 mesh size) with basalt and glass fiber layers. The specimens were subjected to tensile, flexural, and Charpy impact tests in accordance with relevant ASTM standards. Moreover, fracture surfaces were analyzed, and the micrographs were obtained using a scanning electron microscope. The results showed that a high improvement in tensile strength was achieved with BS1–E (1 layer steel mesh–8 layers basalt) and GS1–E (1 layer steel mesh–8 layers glass) hybrid composites, with an increase of 528% and 233%, respectively, compared to steel fiber reinforced epoxy composites. Similarly, BS1–E and GS1–E hybrid composites showed the highest flexural strength increase of 82.2% and 66.8%, respectively, compared to steel fiber reinforced epoxy composites. Consequently, the potential to hybridize steel fiber with glass fiber and basalt fiber could create new materials with unique physical structures and synergistic effects on mechanical properties.

Effect of ply orientation, staking sequence and notch geometry on the failure behaviour of glass fibre-reinforced epoxy composite laminates: A numerical investigation

A detailed numerical failure analysis was conducted for unidirectional glass fibre-reinforced epoxy composite laminates having an elliptical cut-out at the centre using Hashin’s damage model. The major axis, a, of the elliptical cut-out was fixed while the minor axis, b, was varied in such a way, that its upper extreme represented a situation of the plate with a circular hole, while the lower extreme of it represented the presence of a sharp crack in the structure. For angle ply cases, plies oriented along the material direction predicted an ever-increasing load replicating an elastic analysis without any damage accumulation. Such exceptionally higher stiffness and resistance to deformation were much anticipated, as the uni-axial tensile load was applied along fibre direction which shares a large portion of the load in comparison to the matrix material. While the plies oriented perpendicular to the direction of the material behaved as the weakest stack-up sequence in resisting uni-axial tensile load. Multi-angle hybrid composites predicted uneven failure behaviour. For the different combinations of multi-angle layups and minor axis, b, different trends for peak loads were observed. Interestingly, extension-shear coupling was observed for a few configurations which were marginally negligible for others. The variation of opening stress along the transverse direction predicts some very interesting observations. For the higher value of b, the opening stress decreases as we moved away from the irregularity. However, the situation of a plate with a sharp crack (b → 0) showed the effect of crack tip blunting. Near the vicinity of the sharp crack, the opening stress first dropped, then picked up, and again kept on decreasing as we move away. The drop in the stress near the vicinity of the sharp crack is attributed to the blunting of the crack tip.

Metal surface nanopatterning for enhanced interfacial adhesion in fiber metal laminates

A nano-scale electrochemical sculpture (denoted here as NES) method has been developed to create TiO2 nanotube arrays on the surface of titanium sheets for improved bonding between titanium and carbon fiber reinforced epoxy composite laminates. For comparison, other surface treatments including anodization in NaOH, Na2SiO3, Na2C4H4O6 and EDTA electrolyte (denoted as NaTESi) and electrochemical etching in alkali solution (denoted as ALK) were carried out to investigate their effects on the surface morphology, wettability and the shear strength between titanium sheets and epoxy resin. The results from single-lap tests showed that the apparent shear strengths between titanium sheet and epoxy with NaTESi, ALK and optimized NES treatments have been improved by 37.2%, 53.9%, and 70.9%, respectively, in comparison with that of non-treated pristine samples. The samples in single-lap tests showed a mixture mode of cohesive and interfacial failures where the interfacial failure occurred at the epoxy/metal-oxide interface and the oxide films formed during the surface treatments remained intact. Utilizing the treated titanium sheets, fiber metal laminates (FMLs) were fabricated and their interlaminar shear strengths (ILSS) were found to increase by 43.5%, 56.1%, and 75.0%, respectively, compared to pristine samples, showing the promise of the nano-patterning technique.

Experimental investigations on flexural behaviour of delaminated carbon/epoxy composite using three dimensional digital image correlation

In semi automated manufacturing processes of multilayered carbon fiber reinforced composites, defects are induced. These defects cause reduction in service life of the products and lead to decrease in structural performance. In the present work, carbon fiber reinforced epoxy composite laminate with a stacking sequence of [0/0//45/−45/90/45/−45/90/90/−45/45/90/−45/45/0/0] was fabricated by hand lay-up method using vacuum bagging technique. An artificial defect to create pre-delamination was located in this composite between 0° and 45° plies at the centre of laminate. Experiments were conducted in four-point bending to determine the stiffness behavior of composite laminate and study other damage patterns occurred due to the existence of pre-delamination. The probable reasons for occurrence of other damage forms are explained in detail. Three-dimensional digital image correlation (DIC) technique was employed to determine displacements and strains of the specimen. The out of plane displacement due to local buckling against the bending load was also quantified.

Mechanical Properties of E-Glass Fiber - Basalt Fiber Reinforced Polymer Matrix Composite

Composite materials have significant role in automobile and aerospace applications because of their attractive mechanical properties compared. This fascinating properties attracted several industries especially automotive sectors. In contrast to metallic alloys, composite materials composed of individual constituent elements with distinguishable interfaces and chemical identities, however, when combined e-glass and basalt fiber, they will produce superior properties. The fundamental advantage of composite materials is their high specific strength and specific stiffness, which emphasis on its weight saving potential in the finished part. Two principal constituent elements of composites are matrix and reinforcement materials. In the present work, an attempt has been made to understand the advancements achieved in the combination of e-glass fiber and basalt fiber composites. Based on the comprehensive literature review, it is observed that broad work was done on the manufacturing techniques and characterization of the composites, however, limited works were carried out in analyzing the tensile, flexural and shear strength properties of differently oriented fibers in the laminated composites. In this paper, focus was given in fabricating and characterizing the glass fiber reinforced epoxy composite laminates with different fiber orientations, thereby, examining the mechanical properties of prepared laminates for tensile and bending strengths.

Rate-related study on the ply orientation of carbon fiber reinforced epoxy composite laminates

In many practical situations, composite structures are often subjected to complex impact loadings ranging from low to high strain rates. Therefore, it is necessary to characterize the mechanical performance of composite materials at different strain rate. In this paper, carbon fiber-reinforced epoxy laminates with different stacking sequences and ply orientations under dynamic impact loadings were investigated by split Hopkinson pressure bar (SHPB) apparatus. Dynamic results were compared with quasi-static compression results. The experimental results show that the strength of specimens increased with the increase of strain rate. Specifically, the stacking sequence and ply orientation of composite laminates have great impacts on their strain rate sensitivities. Moreover, the failure modes of specimens under quasi-static and dynamic impact loadings were compared and analyzed from both macroscopic and microscopic scales. The fracture surface morphology show that the interface between fiber and matrix tends to be a ductile failure mode under higher strain rates. Finally, through optimization design, the balance point between strength and toughness of the composite laminate was investigated and suggested.

Study on Effect of Fiber Orientation on Flexural Properties of Glass Fiber Reinforced Epoxy Composite Laminates for Structural Applications

Composite laminate design is an important procedure in defining the mechanical properties of laminated composite structure to be used in multi-directional service loading application. Composite technologies or manufacturers who is lack of knowledge regarding the importance of laminate design, tend to develop a composite structure that will collapse or fail below the service requirement. The purpose of this study is to determine the effect of fiber orientation on flexural properties of the designed glass fiber reinforced epoxy laminated composite. Six sets of laminates with different fiber orientation and sequence were simulated using CompositeStar© software to determine its flexural properties. Samples were fabricated to verify the simulated data and were tested in accordance to ASTM D2344. Moreover, crack pattern within the samples after the flexural test is studied. From the simulated results, it shows that laminates which have fiber in tri-direction and quasi-direction display a higher flexural modulus and strength compared to laminates with fiber in uni-directional and bi-directional. In addition, data from tested fabricated laminates samples displayed the same modulus patterns against the simulated data, with variants from 8% to 35%. Additionally, it is found that samples with fiber in ±45 direction shows a transverse and shear cracking which prolonged the cracking propagation before the samples show a complete failure.

Penetration Mechanics of GLARE™ Fiber-Metal Laminates upon Collision with Micrometeoroids

The spacecraft designed for long-duration service are susceptible to hypervelocity impacts of micrometeoroids and orbiting space debris. Such impacts on spacecraft structures can cause spacecraft failure and loss of life. In order to adequately protect the spacecraft bulkhead and flight critical systems, many high-strength composite materials have been developed for debris bumper. GLAss fiber REinforced aluminum is one of the high-performance composites. The review of articles, however, yielded no single study, which has been dedicated to interrogate the damage mechanics of GLAss fiber REinforced aluminum upon collision with micrometeoroids. This study, therefore, aimed at the numerical investigation of penetration phenomena of thick GLAss fiber REinforced aluminum 5-6/5-0.4 laminates upon hypervelocity impact of a projectile. The numerical study employed a predictive model that merged the smoothed particle hydrodynamics and the finite element methods. The model could predict the colossal damage modes of GLAss fiber REinforced aluminum. As seen, the normal impact of a 2 mm diameter spherical 2024-T3 aluminum projectile on GLAss fiber REinforced aluminum, at a relative velocity of 7.11 km/s, resulted into membrane stretching and fiber failure of the glass fiber reinforced epoxy composite laminates. By contrast, the aluminum layers experienced an enormous strain-rate and consequently, suffered thinning, fracture and large mass erosion. The perpetual release waves fragmented the projectile and dispersed the projectile mass prior to the further penetration of GLAss fiber REinforced aluminum. To verify the accuracy of the numerical model, experiments had been conducted by using a two-stage light-gas gun. The experiments generated damage modes of GLAss fiber REinforced aluminum in good correspondence to that of the predictive model. Yet, disparity between the estimations of experiments and simulations had been apparent, which is anticipated due to the phase change of material had not been accounted for in the analysis.

Effect of Healing Agent Filled Microcapsules on Tensile Strength of Glass Fibre Reinforced Epoxy Composite Laminate

This work focuses on the study of variation in behaviour of Glass Fiber Reinforced Epoxy Composite laminate in the presence of healing agent filled microcapsules. Healing capacity was tested for the newly developed laminate with capsules. Two types of microcapsules were made and included in the resin system. One type consists of healing agent and other type consists of curing agent. These capsules were blended in the ratio of 10:3 in the resin system and laminate was fabricated by hand lay-up technique. Initially, the effect of microcapsules on the tensile properties of glass fiber epoxy composites was studied. No conspicuous variation was discerned in the tensile nature. The healing ability of the laminate was checked by producing minor indentation damage on the surface of the laminate with a 0.5 mm ball indenter. It was noticed that 80% of the indentation was recovered within the time span of 48 hours and 93% of healing efficiency was attained. FE analysis was performed with MIDAS NFX software to confirm the results. Both experimental and FE analysis results were observed to be identical.