Plain Weave Fabric Composites Research Articles

Assessment of tensile behaviour of plain weave fabric CFRP composites using acoustic emission technique and deep learning

The applications of Carbon Fibre Reinforced Plastic (CFRP) composites in aerospace applications have increased exponentially in the last decade. CFRP composites are now replacing conventional materials used in high temperature applications. Different types and strategies of reinforcements are used in these composites to improve their applicability to high temperature applications. One of the reinforcement strategies that has been used frequently in the recent years is the plain weave fabric configuration of reinforcing fibres in polymer matrix. A comprehensive damage assessment is essential to evaluate the characteristics of these composites at elevated temperatures. The Acoustic Emission (AE) signals generated during the damage evolution stages are used for studying the damage evolution stages when the plain weave fabric composites are tested at temperatures close to their glass transition state. A new information-theoretic parameter, Lempel-Ziv (LZ) complexity and the deep learning neural network is used for understanding the damage evolution stages. Furthermore, the neural network is used for validating the utilization of LZ complexity as a potential AE parameter for damage classification applications. The results are promising with the damage classification strategy using LZ complexity exhibits an accuracy of 85.1% which is validated through the neural network.

Predicting the tensile stiffness and strength properties of plain woven carbon fiber/epoxy laminates: a practical analytical approach and experimental validations

The difficulties in establishing an analytical model for plain woven fabric composites (PWFC) and its implementation are well-accepted due to the complexity of yarn architecture, approximations assumed, and lack of experimental validations. In this paper, a practical engineering approach is proposed to predict the tensile properties of PWFC. The approach assumes PWFC as cross-ply, the undulation angle an elliptical shape. The approach tremendously simplifies the calculation keeping a close agreement with the tensile experimental results of PWFC. The approach is remarkably compatible with other theoretical models and experiments that existed in the literature.

Effects of Open-Hole and Reinforcement on the Bearing Performance of the Plain-Woven Fabric Composite I-Section Beams under Shear Load

In this article, experiments and finite-element (FE) analyses have been conducted in order to study the effects of open-hole and reinforcement on the buckling and failure of the plain-woven fabric (PWF) composite I-section beams under shear load. With the shear experiments, the buckling and failure characteristics of the PWF composite beams have been obtained, and experimental results of the beams in perfect conditions are compared with the results from the specimens with open-hole and reinforcement in the web region. FE analyses for the composite beams are then carried out with the assistance of the multi-scale method proposed for the PWF composites. With the comparison between the experimental and numerical results, the composite beams’ FE models and the utilized calculation methods are proved to be feasible. According to the parametric study based on the validated models and the multi-scale methods, it is found that the existence of the open-hole decreases the flexural rigidity of the beams’ web region and introduces the stress concentration, which further reduces the structural stability and the shear carrying capacity of the composite beams. With the effects of restraining the structural off-plane deformation and relieving the hole-edge stress concentration, the intercalation reinforcement could effectively improve the bearing performance of the PWF composite beams with open-holes.

Investigation of Interlaminar Shear Properties of CFRP Composites at Elevated Temperatures Using the Lempel-Ziv Complexity of Acoustic Emission Signals.

Three-point bending tests on Short Beam Shear (SBS) specimens are performed to investigate the interlaminar shear properties of plain weave fabric CFRP composites. The tests are performed in a controlled environmental chamber at two different elevated temperatures. The interlaminar shear properties of the specimens remain largely unaffected by the testing temperature. However, the SEM micrographs show different damage progressions between the specimens tested at 100 °C and 120 °C. Fibre ruptures and longer delamination between the plies, as a result of a high temperature, are observed in the specimens tested at 120 °C, which are not observed in the specimens tested at 100 °C. In addition, the acoustic emission activities during the tests are investigated by using piezoelectric sensors. The information-theoretic parameter, the Lempel-Ziv (LZ) complexity, is calculated for the recorded acoustic signals. The LZ Complexities are used for identifying the occurrence of the first delamination failure in the specimens. Additionally, the two features of the acoustic signals, LZ complexity and Weighted Peak Frequency (W.P-Freq), are used for distinguishing the different damage sources in the CFRP specimens. The results are well-supported by the time-frequency analysis of the acoustic signals using a Continuous Wavelet Transform (CWT).

Experimental investigation of the effect of weave type on the mechanical properties of woven hemp fabric/epoxy composites

Natural fiber composites have a growing popularity as alternative materials to petroleum-based plastics and glass fiber reinforced composites due to various economic and environmental reasons. Textile preforms such as woven, knitted, braided, nonwoven, and multiaxial fabrics are commonly used in composite industry due to their high mechanical properties, tailorability, ease of handling during production, and versatility in material design. A range of properties can be obtained by varying the weave pattern and fabric architecture in woven fabric composites. In this study, epoxy composites reinforced with hemp woven fabrics with four different weave types were produced. The weave types chosen were quasi-unidirectional (UD), plain, basket 2/2, and twill 2/2 which are commonly used in the composite industry. Fabric properties such as yarn angle, yarn density, and crimp ratio were determined to evaluate their possible effect on composite properties. Tensile and three-point flexural tests were conducted in order to determine the effect of weave type on the mechanical properties of the resulting composites. It was found that UD composites show the highest tensile strength, tensile modulus, flexural strength, and flexural modulus in the 0° (yarn) direction. Plain weave fabric composites showed the second highest tensile and flexural strength and moduli followed by basket 2/2 weave composites. Composites reinforced with twill 2/2 woven fabrics showed the lowest mechanical properties due to high yarn crimp and yarn angle, less balanced structure, and resulting shear forces involved during various loading conditions.

Many-objective design optimisation of a plain weave fabric composite

Plain weave fabrics provide low-cost composites used in many applications. Their mechanical properties are dependent on the weave and the yarn dimensions, which provides a complex design space to ensure optimal properties for a given application. Genetic Algorithms are commonly used in the literature to optimise the performance of composite materials but are currently limited to two or three objectives, where the optimisation may improve the specified properties but degrade others. In this paper 9 top performing Genetic Algorithms are benchmarked to find designs that respectively satisfy five-objective, three-objective and bi-objective formulations. The results show that the consideration of the five-objective problem is important, since the designs for the five-objective formulation give a wider range of results. These results do not include designs from the optimisation with the more limited objectives, meaning that these designs would need to be redesigned to be practical and demonstrating the benefits of optimisation with more objectives. cMLSGA is shown to be the strongest solver for these problems, contradicting the findings from the Evolutionary Computation literature. When compared with a current weave pattern, the five-objective optimisation provides 101 designs which improve all 5 material properties, with up to 76.61% improvements on the four mechanical properties and a maximum 37.73% reduction on areal density; there are weave patterns with designs that are specific to each of the properties individually.

Effect of Defects on Progressive Failure Behavior of Plain Weave Textile Composites.

Various types of internal defects occur during manufacturing and handling of composite materials. It is practically impossible to manufacture composite structures without defects, making it crucial to understand the effect of defects on their failure behavior to maintain structural safety. In this work, the effect of pre-defects on the failure behavior of plain weave textile composites was studied. Unit cell configurations with symmetric, in-phase, and shifted fiber tow arrangements were considered. Inter-laced warp and fill tows and matrix pockets of plain weave unit cells were modeled in three-dimensional finite elements, and cohesive elements were inserted between all bulk elements to account for the fracture modes of the fiber and matrix direction failure of warp and fill tows, matrix pocket failure, and interface failure. Unit cell models containing pre-defects of voids, tow-matrix pocket separation, warp-fill tow separation, and cracks in the warp and fill tows were analyzed, and their effects on progressive failure behavior were investigated in terms of the interaction between fiber tow arrangements and defects. Results indicated that initial failure occurred in matrix-direction failure mode in fill tows, whereas fiber tow-matrix pocket separation was the major failure mode under uniaxial tensile load. Furthermore, failure behavior was found to be highly dependent on the fiber tow arrangement pattern and the location of pre-defects.

A meso-mechanical material model describing a crash behavior of 2D plain weave fabric composites

In composite aircraft structures, woven carbon-fiber-reinforced composites are used as elements of the boxes to mitigate damage during crash events and provide a measure of protection for the passengers against abrupt decelerations. Due to their multi-scale damage effects and complex coupling between failure mechanisms, despite years of extensive works of researchers around the world, a complete and validated methodology for predicting crushing behavior of woven composite structures has not yet been achieved. In the present paper, experimental and numerical investigations were conducted. The principal contribution is to model and adapt failure mechanisms; fragmentation and kink-bandings, for plain weave fabric CFRP composites, within an advanced numerical model to predict the quasi-static crush behavior of hat-shape cross-section coupons. A meso-scale model, which accounts for intralaminar damage, implemented as a user subroutine VUMAT in Abaqus/Explicit was developed and used. Eight layers of stacked solid elements model were used with saw teeth type and 45° chamfer-type triggering mechanisms to ensure a continuous stable crushing mode of failure. A comparison with experimental and existing numerical model Abq_Ply_Fabric results confirms the computational tool’s accuracy.

A new constitutive model to predict effective elastic properties of plain weave fabric composites

In this study, a new constitutive model has been developed to predict the elastic behavior of plain weave textile composites, using the finite element (FE) method. The geometric conditions and basic assumptions of this model are based on the basics of a continuum theory developed for the plane curved composites. In this model, the mechanical properties of the weave region and pure matrix region is calculated separately and then imported for the FE analysis. This new constitutive model is used to implement the mechanical properties of weave region in the representative volume element (RVE). The constitutive relations are implemented as user-material subroutine code (UMAT) in ABAQUS FE software. The results of FE analysis have been compared with experimental results and other data available in the literature. These comparisons confirmed the capability of the presented model for the prediction of effective elastic properties of plain weave fabric composites.

Comparative Study of Energy Absorption Capability of Flat Plate Coupons Made by CFRP Plain Weave Fabric Composites

Despite years of governmental and academic institutions’ researches, no experimental standards are established for evaluating crush Specific Energy Absorption SEA for plain weave fabric woven carbon-fiber-reinforced composites used in modern aircraft structures as elements of the boxes to mitigate damage during crush events. At the laboratory scale, this paper proposes a comparative study of energy absorption capability of flat plate coupons made by CFRP plain weave fabric composites. A new fixture design and setup were created with hydraulic pressure and drop tower machines to carry out tests of flat plate composite specimens under quasi-static and low velocity on-axis crash loading. For investigating parameters sensibility of triggers and layups, numerical and experimental results of four trigger types and three stacking sequences were compared. A confrontation between experimental and pre-developed UL-Crush numerical material model results confirms that coupons with 0˚ oriented central plies and saw teeth or corrugated triggers dissipates higher energy during crush, compared to coupons with 90˚ or 45˚ oriented central plies and chamfer 45˚ or steeple triggers. An efficient and simplified experimental methodology was developed to measure and investigate different parameters influencing SEA of composites under crush load. Comparison between experimental and UL-Crush material model confirms the performance of such simulation tool.

Compression characteristics, energy absorption, and feasibility evaluation of egg-box panels made of long fibre prepreg sheets

In this study, the feasibility of using long-fibre-reinforced composites for preparing energy-absorbing structures with a complex geometry was verified by comparing the mechanical performance of two types of egg-box panels, fabricated using plain weave fabric composites (WSN3k, SK Chemical, Korea) and a long-fibre prepreg sheet (LFPS, SK Chemical, Korea). Two types of egg-box panels (large and small models) with different dimensions were prepared to determine the influence of the panel size on the collapsing behaviour and energy absorption rate of the panels. The failure modes at each deformation stage were identified through a multiply interrupted compression test. Furthermore, a high-density polyurethane foam was filled in the cavity of the egg-box panels to suppress premature buckling during crushing. The nominal stress–strain relationships of both types of egg-box panels were obtained through a compression test. Thus, the maximum compressive strength, plateau stress, and energy absorption rate of both types of egg-box panels were experimentally determined and compared. Accordingly, a method to apply LFPS in the fabrication of energy-absorbing structures with a complex geometry was suggested.

Multi-scale approach-based studies on the damage-healing and fracture behavior of plain woven textile composite

A study on the fracture and damage-healing behavior of plain woven textile composite (PWTC) is performed in the present work. The primary objective is to conduct 2D progressive failure analysis (PFA) under static in-plane loading conditions, progressive damage-healing analysis for different cyclic strain histories, and experimental fracture studies of PWTC material. A chain of equivalent cross-ply laminates (ECPL) consisting of warp and fill plies is considered as the modified representative volume element (RVE) of PWTC distributing matrix phase within warp and fill yarns. The 2D PFA, based on classical laminate theory (diffused cracking) by eliminating stiffness terms, is performed applying maximum stress theory to predict the macro-scale stress-strain behavior of PWTC. The 2D PFA of PWTC material behavior is implemented as ABAQUS® user material subroutines (UMAT and VUMAT), and the fracturing of PWTC notched bar is demonstrated for an illustration purpose. The novel multi-scale progressive damage-healing analysis is subsequently performed, by -order damage-healing effect tensor, applying Voigt approximation on ECPL model (self-healing in warp ply for an illustration purpose). The failure modes identified in numerical PFA are verified performing in-house experiments (through fractography).

Micromechanical model for rapid prediction of plain weave fabric composite strengths under biaxial tension

The biaxial properties of plain weave fabric composites are important as they are more representative of the performance under complex loading conditions. Experimental determination of these properties is difficult and Finite Element Analysis provides accurate prediction but is computationally expensive and requires skilled users. To provide a simple and rapid prediction of the strength of plain weave fabric composites under biaxial tension a novel micromechanical model is proposed in this paper. To predict the biaxial tensile strengths the minimum total complementary potential energy principle is used on a micromechanical unit cell where the orthogonally interlaced yarns are idealised as curved beams. The new model is verified with a finite element method model on three warp/weft biaxial loading ratios: 1:1, 2:1 (1:2) and 3:1 (1:3) and uniaxial experimental data. The model is verified on four types of material, ranging in mechanical properties from carbon to glass fibres, and 11 yarn specifications, including five cases compared to experimental results and six cases compared to the FE model, giving a mean error of 9.85% and a maximum error of 16.74% compared to experimental results and a mean error of 10.71% and a maximum error of 14.67% compared to the FE model, which demonstrates the effectiveness of the model. The standard deviation of prediction errors among the 11 cases is 2.66%, which demonstrates the robustness of the model for a range of applications. The proposed model is able to predict the uniaxial and biaxial tensile strengths without experimental investigations at the fabric and laminate level and only requires the yarn mechanical properties and specifications.

Entropy-damage mechanics for the failure investigation of plain weave fabric composites

Experimental investigation of recent research shows that the accumulated generated entropy during low-cycle fatigue due to irreversible thermodynamic processes could be a constant value as a material property in metals and composite laminates. The present study aims to evaluate the constancy of accumulated generated entropy in static loading in plain weave fabric composites. A unit-cell-based model, considering different defects, is assembled with continuum damage mechanics (CDM) at the tows level. Equivalent elastic properties of a layer, the initiation, and evolution of damage, as well as irreversible deformation in uniaxial tension and in-plane shear, are simulated in a meaningful physical scale up to the final failure. The obtained results will confirm that Accumulated Entropy Generation (AEG) can be an intrinsic material property in static loading and a measure of the final failure, which can be used in mixed loading conditions.

Multi-scale damage framework for textile composites: Application to plain woven composite

A damage mechanics-based progressive damage analysis (PDA) of plain woven textile composite (PWTC) is performed in this work. The primary objective is to identify the micro-scale and meso-scale failure modes, and compute the ultimate strength of PWTC under in-plane loadings. Multi-scale PDA is performed on an equivalent cross-ply laminate (ECPL) model by maximum stress theory to predict the meso-scale failure modes of PWTC. The damaged stiffness is computed by 3 different ways: 1) hypothesis of strain energy equivalence by proposed 4th order anisotropic damage tensor, 2) applying isotropic damage law, and 3) eliminating the stiffness terms. Novel multi-scale PDA approaches, applying Mori-Tanaka (MT) theory on ECPL model and on the quarter portion of representative volume element of PWTC, are performed to predict micro-scale failure modes. The macro-scale constitutive behaviour of PWTC is theoretically predicted and the corresponding strengths are computed. A user material (UMAT) subroutine is developed to validate the proposed constitutive behaviour of PWTC solving macro-scale boundary value problems in ABAQUS®. The PDA simulation results of 3D PWTC bar model are found to be reasonably matching with the in-house experiments.

Tensile Initial Damage and Final Failure Behaviors of Glass Plain-weave Fabric Composites in On- and Off-axis Directions

Mechanical properties and failure behavior of glass plain-weave fabric composites under on-axis (i.e. 0 and 90° direction) and off-axis (i.e. θ=5, 10, 15, 30, 45 and 60°) tensile loading conditions have been experimentally investigated. Acoustic emissions (AE) monitoring and step-by-step optical observation with interrupted tension tests were adopted to study the character and failure mechanisms of various fiber orientations. The experimental results indicate that both off-axis elastic modulus and strength degrade with increasing off-axis angle in all cases. There is a good agreement for the axial modulus Ex between the experimental results and theory results obtained from orthotropic linear elasticity theory. Adoption of the principal shear strength S45°=28.5 MPa which is evaluated using the tensile strength based on the 45° specimen allows better predictions of the off-axis tensile strengths by means of the Tsai-Hill failure criterion. Off-axis specimens exhibit lower knee point stress than on-axis ones and initial fracture strain monitored by AE (>75 dB) has a good fit to knee-point strain in this study. Tensile strength exhibits an increased tendency toward the delay of initial fracture behavior.

An analytical approach for predicting the tensile strength of plain weave fabric composites

To predict the strength of plain weave fabric composites (PWFCs) quickly, an analytical model was developed by simplifying it as a three‐layer orthogonal laminate (0°/90°/0°). The undulation effects of fibers were taken into account based on stiffness and strength degradation theory. Moreover, less memory space is occupied due to the symmetry in ply stacking of the simplified laminate model. A PWFC was taken as an example to obtain the undetermined coefficients in the proposed analytical model. In comparison with the available experiment results the prediction accuracy of our method was checked. It demonstrates that the prediction errors for tensile strength of PWFCs are less than 10%, while the total modeling and computing time is no more than 30 s. Therefore, the proposed model is very suitable for quick conceptual design in engineering applications of PWFCs. Moreover, it is easy to extend this model to predict strength of PWFCs with other woven patterns, for example, triaxial woven composites. POLYM. COMPOS., 40:2391–2399, 2019. © 2018 Society of Plastics Engineers

Effects of Fabric Counts and Weave Designs on the Properties of Laminated Woven Kenaf/Carbon Fibre Reinforced Epoxy Hybrid Composites

The effects of different fabric materials namely weave designs (plain and satin) and fabric counts (5 × 5 and 6 × 6) on the properties of laminated woven kenaf/carbon fibre reinforced epoxy hybrid composites were evaluated. The hybrid composites were fabricated from two types of fabric, i.e., woven kenaf that was made from a yarn of 500tex and carbon fibre, by using vacuum infusion technique and epoxy resin as matrix. The panels were tested for tensile, flexural, and impact strengths. The results have revealed that plain fabric is more suitable than satin fabric for obtaining high tensile and impact strengths. Using a fabric count of 5 × 5 has generated composites that are significantly higher in flexural modulus as compared to 6 × 6 which may be attributed to their structure and design. The scanned electron micrographs of the fractured surfaces of the composites demonstrated that plain woven fabric composites had better adhesion properties than satin woven fabric composites, as indicated by the presence of notably lower amount of fibre pull out.

An efficient homogenization technique for fiber tows in textile composites with emphasis on directionally dependent nonlinear stress–strain behavior

Now it is common to utilize a FE-based representative volume element (RVE) model to study the mechanical performances of textile composites. Complex architecture of fiber tows can be explicitly reflected in the RVE model, but a homogenization process for the tows, bundle of micrometer-scale fibers bound by a matrix material, is still required for the meso-scale model. We present a systematic yet simple approach to homogenize the fiber tow including directionally dependent nonlinear stress–strain responses. Nonlinear behavior of the matrix material is considered in the present homogenization method through the well defined Hill’s anisotropic plasticity model. Parameters required for the anisotropic plasticity model are obtained from virtual test results at the fiber/matrix level. Tension and shear tests on plain weave textile composites are performed to validate the present numerical approach. It is also demonstrated that the homogenization technique can also be utilized to isolate the matrix stress–strain curve from composite shear stress-shear strain data.

On the constitutive modelling and damage behaviour of plain woven textile composite

The present work deals with the constitutive modelling and progressive failure analysis (PFA) of plain woven textile composites (PWTC). Two novel approaches, equivalent cross ply laminate (ECPL) coupled with classical laminate theory and Mori–Tanaka theory, are developed to compute homogenized properties of PWTC lamina. The PFA of PWTC lamina is performed coupling isotropic damage mechanics with ECPL theory, and meso-scale failure modes are identified. The novelty in the proposed PFA is that, the stress-based failure is detected, and the strain-based damage evolution is computed. A user-defined material subroutine of PFA of PWTC lamina is finally developed and test problems are solved in ABAQUS. All the simulation results of the proposed approaches are finally compared with experiments and found to be closely matching.