Plain Woven Carbon Fiber Research Articles

Bending Properties of CFRTP Laminate Using CNT Grafted Carbon Fiber

Carbon Fiber Reinforced Thermoplastics (CFRTP), which have a short production cycle time and high specific strength and stiffness, are focused on in the automobile industry. Generally, the mechanical properties of FRP are affected by the interfacial strength between the reinforcing fiber and matrix, so the control of the interfacial strength between the reinforcing fiber and matrix is important. Compared to CFRP with epoxy resin, the interfacial strength between the reinforcing fiber and matrix of CFRTP is relatively low. Recently, a method to improve the interfacial strength between the reinforcing fiber and matrix by grafting Carbon Nanotube (CNT) on the carbon fiber has been developed. In this study, the bending properties of CFRTP laminates using CNT grafted plain woven carbon fiber fabric were clarified. Bending strength of CFRTP laminates using CNT grafted plain woven carbon fiber fabric were higher than that using as-received plain woven carbon fiber fabric.

Effect of fiber orientation on the compressive response of plain weave carbon fiber/epoxy composites submitted to high strain rates

Composite materials undergo intricate damage processes, which are accentuated when these materials are exposed to impact loading conditions. In this context, this work aims to study the behavior of fiber reinforced polymer composites submitted to high strain rate in compression. A composite laminate plate was obtained using a plain weave carbon fiber fabric and an epoxy resin as matrix. The Split Hopkinson Pressure Bar (SHPB) technique was used to apply compressive loads at three different strain rates and in six different directions (0°, 15°, 30°, 45°, 60° and 75°) relative to the warp. The compressive failure modes were studied using a high speed camera to record the SHPB test. With increasing strain rates, it was possible to identify a transition from longitudinal cracking failure to delamination buckling failures. Similarly, the off-axis loading conditions (mainly for 45°) resulted in extension-shear coupling effects, which promoted the delamination buckling failures.

Effect of manufacturing defect on mechanical performance of plain weave carbon/epoxy composite based on 3D geometrical reconstruction

The investigation on the effect of manufacturing defect on the mechanical performance of composite is essential for the design and application in practice. In this study, the plain weave carbon fiber reinforced polymer (CFRP) laminates are fabricated by the autoclave process and vacuum bag process (VBP), respectively. Uniaxial tensile testes are conducted with a digital image correlation (DIC) system to obtain the macroscopic mechanical performance and local strain distribution. The internal microdefects of composite laminates are captured by micron-resolution computed tomography (μCT) detection technique, including the size and distribution of void, total volume fraction and geometrical parameters of yarns. Based on the Texgen software and Monte-Carlo algorithm, virtual samples with various void contents are constructed to evaluate the impact of defect using finite element solver ABAQUS/Standard. To substantiate this work, we present a comparative study considering both autoclave and VBP. The effect of void defect on the mechanical performances of CFRP laminate is analyzed through finite element method (FEM). The results reveal that the effect of void defect on the surface strain distribution of laminate is significant, especially the value of maximum strain, which will increase obviously with the void defect content. In addition, the overall stiffness predicted by numerical simulation, taking the effect of void defect into account, is lower than that of theoretical.

Bending behavior of single hat-shaped composite T-joints under out-of-plane loading for lightweight automobile structures

This paper presents an analytical, numerical, and experimental study on the failure behavior of single hat-shaped T-joints made of plain woven carbon fiber polymer (T300/epoxy 618) and subjected to out-of-plane bending. The T-joint is manufactured by vacuum bag molding process at room temperature. An analytical model is developed to analyze the experimental results and to establish the associated failure criteria. Two failure modes: (a) laminate buckling and (b) laminate crushing are considered, and the theoretical relationships for predicting the failure load associated with each of the two modes were developed. The experimental data correlate closely with the analytically predicted behavior, including failure mode and bending stiffness. In particular, both laminate buckling and laminate crushing are observed during the experiment with laminate crushing being the final failure mode, which can be considered to be the most important failure mode of the fabricated T-joint. In addition, numerical simulations based on the finite element method and the Hashin damage criteria also accurately predict the flexural modulus, the peak load, and failure locations of the T-joint obtained in the test.

Prediction of the Elastic Properties of a Plain Woven Carbon Fiber Reinforced Composite with Internal Geometric Variability

A statistical analysis of the yarn parameters of a plain woven carbon fiber reinforced polymer composite was conducted using X-ray micro-computed tomography data. An algorithm based on the correlated Gaussian random sequence was proposed to construct statistically equivalent yarns, which were introduced into a numerical multiscale model. A representative volume element was created to evaluate the macroscopic elastic properties of the composite. The predicted elastic constants showed a good agreement with experimental data obtained from tensile, compressive, and shear tests. This showed the importance of considering internal geometric variability for obtaining accurate simulation results. Finally, the performance of an electric vehicle back door made of the composite material was calculated by finite element analysis. The weight of the back door system was reduced by 47.45%, and performance results showed an excellent prospect of using lightweight composites.

Failure Behaviour of Aluminium/CFRP Laminates with Varying Fibre Orientation in Quasi-static Indentation Test

The response of the aluminium/carbon laminate was examined by an experimental work. The investigation on fibre metal laminate behaviour was done through an indentation test in a quasi-static loading. The hybrid laminate was fabricated by a compression moulding technique and used two types of carbon fibre orientations; plain weave and unidirectional. The plain weave orientation is dry fibre, and unidirectional orientation is prepreg type fibre. The plain weave carbon fibre and aluminium alloy 2024-0 was laminated by using thermoset epoxy while the unidirectional carbon fibre was pressed by using a hot press machine and cured under a specific temperature and pressure. A compression moulding technique was used for the FML fabrication. The aluminium sheet metal has been roughening by a metal sanding method which to improve the bonding between the fibre and metal layer. The main objective of this paper is to determine the failure response of the laminate under five variation of the crosshead speeds in the quasi-static loading. Based on the experimental data of the test, the result of 1 mm/min in the plain weave CFRP has lower loading than unidirectional fibre which the value of both was 4.11 kN and 4.69 kN, respectively.

Effect of stacking angles on mechanical properties and damage propagation of plain woven carbon fiber laminates

Damage propagation induced failure is a predominant damage mechanism. This study is aimed at assessing the damage state and damage propagation induced failure with different stacking angles, of woven carbon fiber/epoxy laminates subjected to quasi-static tensile and bending load. Different stages of damage processing and damage behavior under the bending load are investigated by Scanning Electron Microscopy (SEM). The woven carbon fiber/epoxy laminates which are stacked at six different angles (0°, 15°, 30°, 45°, 60°, 75°) with eight plies have been analyzed: [0]8, [15]8, [30]8, [45]8, [60]8, [75]8. Three-point bending test and quasi-static tensile test are used in validating the woven carbon fiber/epoxy laminates’ mechanical properties. Furthermore, the damage propagation and failure modes observed under flexural loading is correlated with flexural force and load-displacement behaviour respectively for the laminates. The experimental results have indicated that [45]8 laminate exhibits the best flexural performance in terms of energy absorption duo to its pseudo-ductile behaviour but the tensile strength and flexural strength drastically decreased compared to [0]8 laminate. Finally, SEM micrographs of specimens and fracture surfaces are used to reveal the different types of damage of the laminates with different stacking angles.

Acoustic Emission from Microcrack Initiation in Polymer Matrix Composites in Short Beam Shear Test

Acoustic emission (AE) was applied for detection of microcrack initiation in carbon fiber reinforced polymer composites subjected to shear stresses. Experimental materials were prepared from polyester bonded unidirectional (1D) non-crimp fabric and 2D plain-weave carbon fiber fabrics, using the resin transfer moulding technology. Control of epoxy resin/carbon textile proportions enabled variation of fiber volume content from small (34/35% for 2D/1D), through medium (51%) to high (68%). Rectangular samples (45 times 4 times 2 mm) were cut from 1D plates along [0] and across [90] fibers. Similar size samples from 2D plates were cut along warp/weft axes as well as in two orthogonal bias directions. Selected side surfaces were polished for microscopic (SEM) observations. Short-beam-strength tests were performed in 3-point bending (l/h=4), with two AE sensors attached for damage monitoring, which allowed to interrupt loading sequence before final failure. The acoustic emission historic index was the most effective AE parameter in damage initiation control. Microcracks developing on polished composite side-surfaces were observed under the SEM and direct microscopic evidence confirmed fiber debonding to be the principal mechanism of crack initiation in these materials and testing conditions before any further damage.

A multi-physics process model for simulating the manufacture of resin-infused composite aerostructures

The increasing demand for large, complex and low-cost composite aerostructures has motivated advances in the simulation of liquid composite moulding techniques with textile reinforcement materials. This work outlines the development and validation of a multi-physics process model that better simulates infusion behaviour through a complex preform compared with traditional models used in industry that do not account for fabric deformation. By combining the results of a preform draping model with deformation-dependent permeability properties, the shape and local flow characteristics of a deformed textile reinforcement have been more realistically defined for infusion. Simulated shear deformation results were used to define the distributed permeability properties across the fabric domain of the infusion model. Full-scale vacuum infusion experiments were conducted for a complex double dome geometry using a plain weave carbon fibre material. The multi-physics process model showed significant improvement over basic models, since it is able to account for the change in flow behaviour that results from local fabric deformation.

Multiscale modeling of PVDF matrix carbon fiber composites

Self-sensing carbon fiber reinforced composites have the potential to enable structural health monitoring that is inherent to the composite material rather than requiring external or embedded sensors. It has been demonstrated that a self-sensing carbon fiber reinforced polymer composite can be created by using the piezoelectric polymer polyvinylidene difluoride (PVDF) as the matrix material and using a Kevlar layer to separate two carbon fiber layers. In this configuration, the electrically conductive carbon fiber layers act as electrodes and the Kevlar layer acts as a dielectric to prevent the electrical shorting of the carbon fiber layers. This composite material has been characterized experimentally for its effective d33 and d31 piezoelectric coefficients. However, for design purposes, it is desirable to obtain a predictive model of the effective piezoelectric coefficients for the final smart composite material. Also, the inverse problem can be solved to determine the degree of polarization obtained in the PVDF material during polarization by comparing the effective d33 and d31 values obtained in experiment to those predicted by the finite element model. In this study, a multiscale micromechanics and coupled piezoelectric-mechanical finite element modeling approach is introduced to predict the mechanical and piezoelectric performance of a plain weave carbon fiber reinforced PVDF composite. The modeling results show good agreement with the experimental results for the mechanical and electrical properties of the composite. In addition, the degree of polarization of the PVDF component of the composite is predicted using this multiscale modeling approach and shows that there is opportunity to drastically improve the smart composite’s performance by improving the polarization procedure.

Three-dimensional-linked carbon fiber-carbon nanotube hybrid structure for enhancing thermal conductivity of silicon carbonitride matrix composites

In this paper, a novel three-dimensional-linked (3D-linked) carbon fiber-carbon nanotube (Cf-CNT) hybrid structure is presented to improve the through-thickness thermal properties of polymer derived silicon carbonitride matrix composites. Comparing with pristine plain woven carbon fiber, the pores in the criss-cross position are fully filled with carbon nanotubes (CNT) in the presented Cf-CNT hybrid structure. CNT can be integrated in between the plain woven carbon fibers and generate a 3D-linked Cf-CNT hybrid network structure. Thanks to the percolating network of CNT and the densification effect, the through-thickness thermal conductivity of the resultant ceramic matrix composites is improved significantly, which is enhanced by 10% with short CNT and by 31% with long CNT, respectively. The thermal conductivity is found to increase with temperature from 100 to 900 °C for these composites. Multiphysics simulation is conducted to reveal the effects of the 3D-linked Cf-CNT hybrid structure on the thermal conductivity at various temperatures, which are consistent with experimental results.

Effect of Press Slide Speed and Stroke on Cup Forming Using a Plain-Woven Carbon Fiber Thermoplastic Composite Sheet

Carbon-fiber-reinforced thermoplastic (CFRTP) is viewed as a prospective material for high-cycle production of CFRP parts. This paper deals with a process whereby a preheated thermoplastic plain-woven carbon fiber fabric sheet is formed into a circular cup by a mechanical servo-press. The effects of press parameters, specifically the bottom dead center and slide speed in the forming of CFRTP cup, on the press load, pressure, internal temperature, shape accuracy, and internal structure have been investigated. A plain-woven carbon-fiber-reinforced PA6 thermoplastic sheet was used. The sheet consisted of four layers of woven 3K carbon and had a thickness of 1 mm. The sheet was heated to 320°C under a halogen heater so that it would be around the recommended temperature for forming 260°C after transfer to the mold. The sheet was pressed into a circular cup shape by a cold mold while the periphery was cramped by a heated holder so as not to cool the sheet before it was pulled into the mold cave. Die clearance was designed considering the thickness increase due to the fiber concentration during the forming. By increasing the slide stroke to the bottom dead center, the applied press load was increased and the internal structure was improved, showing no voids. By increasing the slide speed, the final press load was reduced and shape accuracy was improved through a good pressure distribution on the mold. Measurement of the surface temperature of the sheet during the forming revealed that it remained in the melting region of the resin in the case of fast slide speed, but dropped below the melting temperature in the case of low slide speed. This difference apparently led to spring-in or spring-back after the forming. The experimental results indicate that appropriate balance among press speed, bottom dead center, and sheet temperature is important in the high-cycle forming of CFRTP.

Carbon/epoxy composite delamination analysis by acoustic emission method under various environmental conditions

New multifunctional materials for aerospace industry with exceptional properties must be tested under various environmental conditions to find out possible scatter factors for evaluated properties. Delamination is a typical damage mode observed for laminated composites. Therefore, reliable information regarding the delamination growth behaviour is needed for all operational environments of an aircraft operated at cryogenic and elevated temperatures. In this paper, delamination crack growth monitoring in a climatic chamber on double-cantilever beam (DCB) specimens using optical devices and acoustic emission (AE) techniques is described. A relationship between cumulative AE energy, events localization, clusters, and crack growth in a plain-weave carbon fibre–reinforced epoxy is investigated under constant displacement rate loading at + 80 °C, and − 55 °C. Test results are evaluated for specimens with multi-walled carbon nanotubes (MWCNT) in the microstructure and for a reference material. The mechanical properties during delamination are represented by fracture toughness GIC, and they are also correlated with the AE data. The elevated test temperature caused a decreased rate of released AE energy. The crack growth in material with more significant fibre breakage caused increase of the AE release rate.

Influence of locational states of submicron fibers added into matrix on mechanical properties of plain-woven Carbon Fiber Composite

AbstractThe aim of this study was to show the influence of locational states of submicron fibers added into epoxy matrix on mechanical properties of modified plane-woven carbon fiber reinforced plastic (CFRP). To change the locational states of submicron fibers, two kinds of fabrication processes were applied in preparing specimen by hand lay-up method. Submicron fibers were simply added into epoxy resin with ethanol after they were stirred by a dispersion process using homogenizer to be located far from the interface between reinforcement and matrix. In contrast, submicron fibers were attached onto the carbon fibers by injecting from a spray nozzle accompanying with ethanol to be located near the interface, after they were tentatively contained in ethanol. The plain-woven CFRP plates were fabricated by hand lay-up method and cured at 80 degree-C for 1 hour and then at 150 degree-C for 3 hours. After curing, the plain-woven CFRP plates were cut into the dimension of specimen. Tensile shear strength and Mode-II fracture toughness of CFRP were determined by tensile lap-shear test and End-notched flexure(ENF) test, respectively. When submicron fibers were located far from the interface between carbon fibers and epoxy resin, tensile shear strength and Mode-II fracture toughness of CFRP were improved 30% and 18% compared with those of unmodified case. The improvement ratio in modified case was rather low (about few percentages) in the case where submicron fibers were located near the interface. The result suggested that crack propagation should be prevented when submicron fibers were existed far from the interface due to the effective stress state around the crack tip.

Effect of fine particle incorporation into matrix on mechanical properties of plain woven carbon fiber reinforced plastics fabricated with vacuum assisted resin transfer molding

Purpose of this study is to improve mechanical properties of the carbon fiber reinforced plastic laminates (CFRP), such as inter-laminar fracture properties, by addition of fine particle to matrix resin. Vinyl ester was used for the CFRP matrix and two types of fine particle, alumina and silicon rubber were used for the modifier. CFRP laminates were fabricated with vacuum assisted resin transfer molding. Single end notched bending tests on resin specimens, and tensile, three point bending, double cantilever bending and end notched flexural tests were conducted on CFRP laminates to investigate the effect of particle incorporation on mechanical properties CFRP laminates. In situ observation was also conducted during tests to discuss the role of fine particles. From the results, soft particle, such as silicon rubber, is effective to improve mode I inter-laminar fracture toughness through cavitation formation. Rigid particles, such as alumina, could improve mode II inter-laminar fracture toughness by bridging between crack surfaces.

Evaluation of Mechanical Properties of Hybrid Fiber Reinforced Polymer Composites and their Architecture

Traditional fiber reinforced polymer (FRP) composite that is often fabricated from single type of reinforcement has shown its ability to replace the conventional metallic material counterparts. However, due to several stringent requirements on ductility, this has affected the performance of FRP composites for the structural applications. Therefore, hybrid composites, which combine two or more fiber reinforcements, have been introduced in order to overcome the short of traditional FRP composites. This paper investigates the mechanical properties of three different arrangements of hybrid composites made from glass fiber (plain-woven and stitched bi-axial ±45˚) and plain-woven carbon fiber. Vacuum assisted resin transfer moulding method was employed to fabricate the hybrid composite panels. Mechanical properties such as tensile strength, flexural strength and volume fraction of the hybrid composites were determined per ASTM standards. Experimental results indicate that the [CWW]6 arrangement, where C and W are weaved carbon fiber and glass fiber respectively, were superior in terms of mechanical properties.

Crack Growth Monitoring of CFRP Composites Loaded in Different Environmental Conditions Using Acoustic Emission Method

New materials developed for aerospace structures continuously improve aircraft safety. New multifunctional nanostructured materials with exceptional properties must be tested and validated to exploit their full potential. Delamination is a typical damage mode for laminated composites. Therefore, reliable information regarding crack growth behaviour is needed for all operational environments of an aircraft operated at room temperature, as well as at cryogenic and elevated temperatures. In this paper, crack growth monitoring in a climatic chamber on double-cantilever beam (DCB) specimens using optical devices and acoustic emission (AE) techniques are described. A relationship between cumulative AE energy and crack growth in a plain-weave carbon fibre–reinforced epoxy is investigated under constant displacement rate loading at +80°C and -55°C. Test results are evaluated for specimens with nanofillers in the microstructure and for a reference material. The mechanical properties during delamination are represented by fracture toughness GIC, and they are also correlated with the AE data. The elevated test temperature caused a decreased rate of released AE energy. The results are affected by both temperature and material.

Flexural Property and Mode I Interlaminar Fracture Toughness of Plain Woven Carbon Fiber Reinforced Plastics after Water Absorption and Freezing

In this study, the effects of water absorption and freezing on flexural property and mode I interlaminar fracture toughness of Carbon Fiber Reinforced Plastics (CFRP) were investigated. Plain woven carbon fiber was used as reinforcement. Epoxy resin was used as matrix. Water absorption test was conducted at 90°C for 24, 100, 250 and 500 hrs. After water absorption, the specimens were kept under-15°C for 24 hrs. Static three point flexural and Double Cantilever Beam (DCB) tests were conducted after water absorption and freezing. As a result, flexural strength and mode I interlaminar fracture toughness of CFRP after water absorption and freezing decreased with an increase of immersion time. Flexural modulus of CFRP did not change after water absorption and freezing. And flexural strength and mode I interlaminar fracture toughness of frozen CFRP after water absorption were lower than those of water absorbed CFRP. From the observation using scanning electron microscope, it is understood that the water absorption and freezing affects the interfacial adhesion between fiber and matrix.

The effects of Z-stitching density on thermophysical properties of plain woven carbon fiber reinforced silicon carbide composites

Three types of plain woven carbon fiber reinforced silicon carbide composites (C/SiCs) with 4, 9, and 16 Z-stitching/cm2 densities (S4, S9 and S16) were fabricated by chemical vapor infiltration. The results indicated that the activation energies for thermal diffusive mechanism transition of S9 and S16 increased by 151 and 192% compared with that of S4, respectively. With the increase of Z-stitching density, the positive effects of “pore” phase, in-plane fibers and Z-yarns on thermal conductivity were enhanced. Compared with that of S4, the through-thickness thermal conductivities of S9 and S16 increased by approximately 0.3 and 0.5W/m°C in the temperature range 200–1400°C, respectively. The thermal expansions of these composites were mainly determined by SiC matrix. The increase of structural integrity and decrease of SiC amount reduced the in-plane coefficient of thermal expansion (CTE) with the increase of Z-stitching. Compared with that of S4, the in-plane CTEs of S9 and S16 decreased by about 0.4 and 0.7×10−6°C−1 in the same temperature range, respectively.

Interlaminar shear damage mechanisms of a 2D-C/SiC composite at elevated temperature in vacuum

The aim of the study is to reveal the damage mechanisms of a plain woven carbon fiber cloth reinforced silicon carbide composite (2D-C/SiC) under interlaminar shear stress at elevated temperature. The interlaminar shear tests were carried out by compression of a double-notched specimen. Damage mechanisms were revealed by loading/unloading experiments. The damage evolution mainly involves the initiation and propagation of intra-bundle cracks, matrix cracking and emergence of the cracks. Release of the residual thermal stresses in the matrix and improved bonding of fiber/matrix interface enhance the resistance to initiate cracks. More cracks could be generated above the preparation temperature, and result in the degradation in interlaminar shear strength and crack initiation stress.