Properties Of Plain-weave Composites Research Articles

A multi-scale uncertainty quantification model encompassing minimum-size unit cells for effective properties of plain woven composites

The uncertainty quantification is crucial to the high-precision prediction of composites’ effective properties. However, the unclear input uncertainties of multiscale parameters, complex uncertainty propagations of inter-scale correlations, and unaffordable computational cost of massive simulations are three primary problems at present. In this work, an innovative model with high accuracy and feasible cost for the mechanical property prediction of plain woven composites is developed encompassing minimum-size unit cells and multi-scale uncertainty quantification. For the accuracy holding, an uncertainty analysis process consists of the traceability description, inter-scale propagation and quantification is established. The uncertainties of geometry are described by uniform distributions for fiber, fiber bundle and composite scales, respectively; that of constituent properties is described by normal distributions for fiber and matrix, and its propagations to bundle and composite scales are realized by Nataf transformation methods with the consideration of parameter correlations. For the cost control, minimum-size unit cells are formulated by exhaustive analysis of structural symmetries to reduce the computational cost without accuracy compromising for the single simulation, and 1/8 and 1/16 unit cells compared with traditional full-size ones are obtained. The evolution convergence for statistical uncertainties of effective properties is finally obtained with totally reduced computational cost of 89%.

Prediction of elastic properties of woven polymer composites using micromechanical models and measured microstructural parameters

Prediction of elastic properties of plain weave composites using two well-known micromechanical models is addressed, along with a dedicated finite element model of the unit cell which includes details of the woven architecture. Predictions of micromechanical models are carried out using geometric input parameters statistically measured from micrographies of the unit cell of the plain weave composite and compared to finite element predictions and to measured elastic properties of an E-glass/vinyl ester plain weave composite. The micromechanical models predict that the width and thickness of the yarn in the fill and warp directions greatly influence the elastic properties and anisotropy of the plain weave composite. Good agreement between all approaches and the measured values is observed for the in-plane elastic properties, as long as the input geometric parameters of the unit cell required for the models are measured with statistical rigor. However, transverse shear moduli are not accurately predicted by the examined micromechanical models, only by the finite element method. Reasons for such discrepancies are discussed and supported by modeling findings and digital image correlation full field strain maps.

Progressive damage analysis for fatigue life prediction in plain weave composites: A multi-scale approach

This study introduces an analytical micromechanical model considering progressive damage designed to predict the elastic and strength properties of plain weave composites subjected to fatigue loading. The presented model is composed of a multi-scale micromechanical model, wherein a progressive damage mechanism has been incorporated. During the development of this multi-scale micromechanical model, a representative volume element was chosen and homogenized, utilizing assumptions pertaining to identical out-of-plane stresses and in-plane strains. These assumptions satisfy the conditions of equilibrium and displacement continuity in the representative volume element and, through a three-step process, enhance the model’s accuracy in applying the damage model and predicting the elastic properties of plain weave composites under static loading. Subsequently, the damage mechanism was progressively developed by accounting for the crucial role of matrix crack growth. This was achieved by employing the kinetic theory of fracture for polymers and integrating it with the multi-scale micromechanical model. Ultimately, the elastic and strength properties of plain weave composites under fatigue loading were predicted. A comparison of the results derived from the present model with those available in the literature demonstrated a high degree of agreement.

Evolution of process-induced strain/stress field in plain woven composite antenna reflector by fusing multiscale numerical model and experimental data

This paper investigates the evolution of the process-induced strain/stress field in plain woven composite antenna reflectors by fusing the numerical simulation and the experimental data. In the numerical simulation, a new multiscale curing process model of plain woven composite reflectors is proposed for process-induced strain/stress prediction. Specifically, representative volume elements at three scales are established and solved to capture the effective properties of plain woven composites. Further, a novel interface layer with cure-dependent parameters is used to emulate the tool-part interaction. In the experiment, the fiber Bragg grating sensor network is embedded into the composite reflector to measure the process-induced strains. Some of the measurements are fused into the curing process model by the optimization-based fusion method. The fused model was used to predict the full-field strain and stress, and the results indicate that areas with larger curvatures experience greater strain and stress due to the interaction between the tool and the part.

Comparisons of influence of random defects on the impact compressive behavior of three different textile structural composites

Carbon fiber breakage as one kind of defects that inevitably exists in composites has a distinct effect on the mechanical properties of textile structural composites. This paper investigated the influence mechanisms of random defects on compressive properties of plain woven composites, angle interlock woven composites and braided composites with the numerical simulation method. Based on the actual geometrical architecture of the plain woven, angle interlock woven and braided preforms, three microstructural models were built separately to simulate the impact compressive behavior of each composite. Random defects with different volume fractions ranging from 2% to 10% were introduced into the fiber tows in each microstructural model using the Monte Carlo method. The results reveal that random defects in fiber tows give rise to various reductions of the compressive strength and modulus due to the different fiber orientations and fracture mechanisms. Compared with the ideal model, the proposed finite element analysis (FEA) model introducing random defects can more accurately predict the compressive strength, compressive modulus and damage pattern of textile structural composites.

Development and Validation of Multiscale Thermo-Elasto-Viscoplastic Analysis Method for Plain-Woven Composites

In this study, the analysis method for thermomechanical properties of plain-woven composites is developed, and applied to thermoelastoviscoplastic analysis of plain-woven glass fiber-reinforced plastic (GFRP) composites. For this, a time-dependent constitutive equation depending on temperature for matrix materials is incorporated into the micro/meso/macro-scale thermo-elastic homogenization method for plain-woven composites developed by our research group. This method enables us to analyze thermoelastoviscoplastic properties in not only fiber bundles but also fibers and matrix materials in fiber bundles, as well as macroscopic thermal properties. This method is then applied to the thermal expansion analysis of a plain-woven GFRP composite subjected to a macroscopic temperature change from 25°C to 80°C before it is cooled to 25°C. Comparing the analysis results with experimental data, we validate the present method. It is also shown that the present method can evaluate themal residual stress and strain in the composite.

Multi-scale constitutive modeling of natural fiber fabric reinforced composites

Natural fiber reinforced structural composites have a hierarchical structure made from stacked fabrics of interwoven yarns formed by twisting together discontinuous natural fibers. We develop multi-scale constitutive models to investigate the mechanical properties of plain woven composites. The multi-scale constitutive modeling is carried out in two steps: the effective micromechanical properties of a micro-scale representative volume element (RVE) of the twisted yarn are calculated using an orientation averaging method, which are subsequently transferred to a meso-scale RVE of the final composite to compute the elastic constants by homogenization over the RVE. 3D finite element models of the meso-scale RVEs of composites are developed to verify the accuracy of the proposed model. The multi-scale modeling results show that the yarn twist angle has significant effects on the elastic properties of the composites. The predicted results from the multi-scale constitutive model show good agreements with that from finite element analysis and experiment.

Influence of the fiber/matrix strength on the mechanical properties of a glass fiber/thermoplastic-matrix plain weave fabric composite

In this work, we analyze the influence of different fiber surface treatments on the mechanical properties of plain weave composites. The reinforcement is a glass fibers fabric and the matrix is an acrylic polymer. Until very recently, this thermoplastic polymer family was not used in composite industry. It is therefore necessary to study if the existing fiber surface treatments are suitable for acrylic resins or if new ones have to be found. At the macroscale, composite materials corresponding to different fiber surface treatments were characterized with: (i) monotonic in-plane shear tests and (ii) heat-build up fatigue measurements on specimens with ±45° fiber orientations with respect to the tensile force. At the mesoscale (fabric scale), the development of damage was experimentally analyzed from (i) 3-D DIC (Digital Image Correlation) full-field strain measurements with spatial resolution smaller than the textile repeating unit and (ii) X-ray microtomography. We show that the analyzed composite materials exhibit linear viscoelastic behavior until a given stress threshold above which damage develops in the material. It was also found that the application on the fibers of a coupling agent specifically developed for promoting the bond between glass fibers and acrylic resins improves the composite mechanical properties, in particular the fatigue properties.

Effective properties for plain weave composites through-thickness reinforced with carbon nanotube forests

Abstract In this paper, an analytical approach is proposed to study the elastic properties of plain weave unit cells with reinforcing single-walled carbon nanotube forests of different growing patterns on the warp and weft carbon yarns. For the carbon nanotube-reinforced polymer matrix in which the carbon fibers are embedded, its properties can be evaluated using a modified rule of mixture. A numerical study using the present analytical approach reveals that for the cases considered, only a small increase in the nanotube volume fraction can result in a remarkable increase in the out-of-plane Young’s modulus and a slight increase in the out-of-plane shear modulus but a decrease in the out-of-plane Poisson’s ratios for the plain weave composite. The existence of carbon nanotube forests does not significantly affect the effective in-plane properties of plain weave composites. It is also noted from the present numerical study that the effective properties of plain weave composites with nanotube forest reinforcement are closely related to the nanotube volume fraction, growing or distribution patterns, but slightly affected by the orientations of carbon nanotubes.

Micromechanical Models for Bending Behavior of Woven Composites

Thin woven composites have been popular for space structures due to the symmetrical and balanced properties. Although in-plane properties of these materials can be calcu- lated accurately using the classical lamination theory (CLT), the corresponding bending properties lack any accuracy for one or two-ply woven laminates. Experiments on thin laminates made from woven composites disagree with the estimates of bending stifiness and strains using CLT. Such estimates can result in errors of up to 200% in the maximum bending strains or stresses, and up to 400% in the bending stifinesses. This is because CLT assumes that the flbers and the matrix are uniformly distributed in each lamina, and relies on this uniformity in the integration of the transformed laminate stifinesses over the thickness of the laminate. However, a thin laminate made from fabrics in fact con- sists of bundles of flbers that are typically much thinner than the overall thickness of the laminate; these bundles are not homogenous through the thickness. This paper presents micromechanical models for bending behavior of woven composites considering the flber bundles and the matrix and their interactions. Finite element models are developed to estimate the bending properties of plain weave composites. The results are compared to experimental data, showing very good agreement particularly for a lamina.

Integrated micro/macro-mechanical model of woven fabric composites under large deformation

Thermoforming of woven composite panels generally involves significant in-plane shear deformation, and induces additional anisotropy into the composites. In our previous paper, a new constitutive model for macro-mechanically characterizing the non-orthogonal material behavior under large deformation was proposed. In the present work, we develop an integrated micro- and macro-constitutive model to predict the mechanical properties of woven composites during large deformation based on the microstructure of composites, i.e., the dimensions of fibers, yarns and unit cell, the material properties of composite constituents, as well as the orientation of yarns. The modeling strategy starts with a geometrical description of the yarn and the unit cell during a trellising shear deformation. Following this, a mechanistic analysis on a unit cell has been conducted to determine the equivalent shear properties of woven composites used in our non-orthogonal model. Meanwhile, a simple and conventional analytical technique is applied to predict the tensile properties of woven composites. The proposed integrated micro/macro-model shows excellent agreement with the experimental data and the 3D finite element results. Finally, a parametric study is performed using the presented models to investigate the effects of major geometrical parameters and material properties of the constituents on the shear properties of plain weave composites.

Mechanical Properties of Plain Woven Composites with Flexible Interphase

Mechanical Properties of Plain Woven Composites with Flexible Interphase

Micromechanics models for the elastic constants and failure strengths of plain weave composites

In this paper, two models are presented for plain weave composites. One is finite element analysis (FEA) model for elastic constants, namely, sinusoidal yarn model. Another is analytical model for failure strengths, namely, sinusoidal beam model. The FEA model is generated by interfacing an in-house computer code with FEA software strand6, and the analytical model is developed using the theory of elasticity. Numerical studies are carried out using the present models to investigate the effects of some major geometrical parameters on the properties of plain weave composites. It is concluded that the failure strengths are closely related to the fiber volume fraction of a yarn, and the mechanical properties are closely related to the overall fiber volume fraction of the composites. An experimental testing program is conducted for T300/934 plain weave composites to validate the developed models. A good agreement exists between the predicted and measured results.