Fabric Geometry Model Research Articles

Low-velocity drop weight impact behavior of Twaron® fabric investigated using experimental and numerical simulations

Low-velocity drop weight impact experiments of plain-woven Twaron® CT 612 at an impact energy of 15, 20, 30 J are carried out on a 9250HV drop weight impact tester. Specially treated specimens are designed and used to deal with boundary conditions because the fabric is too flexible and cannot be fixed precisely. Experimental results reaffirm that TwaronⓇ is an impact-rate-sensitive material and that a greater initial impact energy resulted in a larger breaking load, greater failure strain, larger energy absorption and shorter contact duration to the fabric in the impact process., The commercial code ANSYSⓇ-AUTODYN is employed for impact FE analysis on a physically based impact model which is designed basing on the fabric's geometry parameters and the experimental set-up. The dynamic mechanical parameters of TwaronⓇ is analyzed and applied to FE model to describe the rate-sensitive mechanical properties through a three-element spring-dashpot model. Standard earth gravity is applied to the impact model to reflect the impact process realistically as well. The results indicate that a remarkably close agreement is obtained between the simulation and experimental results in various impact scenarios. Thus, the energy absorption mechanisms and stress distributions during the impact process are clarified. The influence of specimen shape and size are also analyzed systemically. These results indicate that the present experimental set-up and the developed fabric geometry model are effective at investigating many additional mechanical problems in textile fabrics and/or flexible material structures.

Open-Hole 3D Braided Composites Strength Prediction and Stress Analysis

The stress concentration caused by notches is a common engineering issue for composite structure application. 3D braided composite possess excellent damage tolerance compared to common laminates. The tensile properties of 3D braided composite with open-hole and un-notched were experimentally examined. The mechanic properties of 3D braided composite in other directions are predicted using FGM (Fabric Geometry Model) and finite element analysis. The stress distributions around the hole and perpendicular to the loading direction are analyzed based on Abaqus software. The simulation results were compared with Lekhnitskii's analytical study. The open-hole strength of 3D braided composite was predicted respectively using Average stress failure criteria, Point stress failure criteria (PSC), and also the progressive failure analysis based on different failure criteria. The predicted strength results were compared to the experimental values. The results show the PSC predicted strength matched the experiment, while the progressive failure analysis can predict the failure initiation, propagation and final failure mode.

Open hole tension and compression behavior of 3D braided composites

AbstractThe damage tolerant behavior of 3D braided composites is evaluated in terms of the open‐hole notch strength test under tensile and compressive loading. The influence of fiber architecture is evaluated by comparing 3D braid with and without axial yarns as well as laminated composites based on ASTM quasi‐static tension and compression testing standard. The results show that the notched and un‐notched properties of the two types of 3D braided composites are similar under tension and compression loading. Comparing to laminates, both types of 3D braided composites demonstrated superior notch insensitivity than laminated composites. For the failure behavior of the 3D braided composites, under tension loading, crack of both notched specimens tends to propagate along the notch and finally render the specimen to failure. Clear cracks usually presented on the samples without axial yarns, while not for the specimens with axial yarn. Under compression loading, the two types of 3D braided composite are also macroscopically similar, showing transverse fracture. The modified Fabric Geometry Model is used to predict the tensile properties of 3D braided composite. The predicted and experimental results are shown to be in good agreement.

3D network structure and sensing performance of woven fabric as promising flexible strain sensor

A flexible strain sensor was developed through weaving conductive yarns to 3D woven fabric. The relationship between the sensing performance of the woven fabric and its 3D network structure containing yarn shrinkage and arrangement density, as well as fabric interweaving, was investigated according to Pierce’s fabric geometry model and the assumption of elastic strain of yarn. Based on such models and assumption, the theoretical results were verified by the experimental data from uniaxial stretching, and the trends of both results were consistent. The sensitivity of woven fabric on its elastic strain is relatively small (GF < 2) and nonlinearity. With the deformation of fabric geometry structure (Stage I) caused by stretching on warp direction, the shrinkage of weft yarn (cw) and interweaving points (nw) decreased or the arrangement density of warp yarn (Nj) increased, resulting in improved sensitivity on warp direction. At yarn deformation stage (Stage II), the increase in interweaving points (nw) or the decrease in arrangement density of warp yarn (Nj) could improve the sensitivity on warp direction. All the results provide a theory basis for the design and development of flexible strain sensor with promising application as wearable electronic device.

Simulation of heat transfer through woven fabrics based on the fabric geometry model

Numerical simulation is a rapid, effective, and low cost method to predict the heat transfer performance of fabrics. However, in previous research fabrics are usually assumed to be a uniform plate. Here, geometry models of 5/3 satin weave, double plain weave, and double twill glass fiber fabrics have been established based on the fabric thickness, yarn path and yarn cross-section shape. In the fabric unit, air occupies 60% to 80% by volume of the fabric unit. Therefore, the air in the fabric unit should be considered in the numerical simulation by finite element analysis. In this work, the fabric unit cells consisted of a yarn domain and an air domain. Based on the fabric unit cell model, the finite element method was used to predict the heat transfer through fabrics. The numerical temperature data are very close to the experiment data for glass fiber fabrics. Prediction results show that the temperature of 5/3 satin fabrics increase more rapidly than the double layer fabrics, and the heating rate of double twill fabric is lower than that for the double plain weave fabric, and they coincide well with the experiment data.

An analysis of the tensile properties of nanofiber mats

Nanofibers have gained increasing attention because of their potential for a wide range of applications. In order to fully exploit the potential of nanofibers, there is a need to understand the relationship between the mechanical properties, especially tensile properties, of an individual nanofiber and that of nanofiber assemblies. In this study, we examined the relationship between a single nanofiber and a nanofiber mat formed by randomly oriented nanofibers through geometric analysis. The analysis showed that the tensile strength of a randomly oriented nanofiber mat is a function of fiber packing density (porosity), test specimen dimension (width to length ratio), and the tensile strength of a single nanofiber. Similar relationship can also be derived for the elastic modulus of individual nanofibers and that of the nanofiber mats. Parametric study was carried out using this fabric geometry model and the applicability of the model was evaluated using published experimental data.

Regression‐based model for elastic constants of 2D braided/woven open mesh angle‐ply composites

AbstractThe elastic constants of closed mesh braided/woven fabrics are generally obtained from finite element analysis, fabric geometry model, and modified classical laminate plate theory. These models are complex and often impractical for industrial design purposes and do not address the cases of open mesh braided/woven fabrics. This paper proposes an alternative to existing models and software packages. Simple regression‐based empirical equations were developed to obtain Ex, Ey, Gxy, and νxy of braided/woven fabrics at any angle‐ply angle using the braid/weave unit cell volume fraction (Vf0), the fiber volume fraction (Vf), and the elastic constants of an equivalent angle‐ply laminate (E, E, G, ν). Design equation predictions were verified by comparing them to a previously validated modified classical laminate plate theory (CLPT) model using various fiber/resin combinations. Excellent agreement was found for each set of results. POLYM. COMPOS., 26:152–164, 2005. © 2005 Society of Plastics Engineers

Stiffness and failure modelling of 2D and 3D textile-reinforced composites by means of imbricate-type elements approaches

This paper discusses the stiffness and failure behaviour modelling of textile-reinforced composites (TRCs). Different numerical and semianalytical approaches, based on a multilevel geometrical meshing which allows considering mechanical phenomena encountered at the filament, the yarn and the unit cell levels, are developed. The cases of a 2D woven and a 3D braided composites are studied and their homogenised stiffness properties are compared to solutions provided by finite element methods and the fabric geometry model. The modelled failure of both the 2D and 3D TRC are compared to experimental data.

Elastic and damage behavior of three-dimensional woven composites incorporating solid rods

This articles examines the relationship between processing and performance of three-dimensional (3D) woven composites. Four types of fabrics were made with the solid rods incorporated in the axial direction. The first is a 3-axis orthogonal type having yarns in two weaving directions; the second is similar except that no beat-up is applied to the weaving yarns. The third type combines the rods in two directions. The last is a 5-axis type that adds two off-axis yarns to the first type. Both Kevlar and carbon tows were used in the rods and weaving yarns. No pressing force was applied during curing of the vinyl-ester resin to preserve the as-formed fabric configuration. Microstructures of the materials have been observed, and unit cells have been defined to model the composites. The fabric geometry model is adopted for predicting the elastic moduli. Material characterization has been carried out based on flexure and Izod impact tests. The dominant damage modes under the flexural and impact loads have been identified for each type of materials. The concept of weaker-plane that dictates material failure has been introduced for the multi-directionally reinforced composites. Weaving loops on fabric surfaces have been found to play a crucial role in the formation of cracks. Failure and the associated energy-absorbing mechanisms of the present materials have been discussed in detail.

Elastic moduli and damage mechanisms in 3D braided composites incorporating pultruded rods

This paper is aimed at elucidating the processing-property relationships of composites through experimental characterization. The fabrication processes involve three primary steps: the pultrusion of 1 mm diameter unidirectional rods, the formation of three-dimensional preforms incorporating the rods, and the impregnation of resin into the preforms. The use of the rods is intended to address crimp problems often seen in textile composites. A modified two-step set-up to incorporate the rods has been developed. A series of fabrics with varying braiding fibers, pitch lengths and braider sizes has been made to investigate their respective influence on processing and damage behavior. In comparison with conventional textile composites, the axial yarns are straight and are packed in a rather dense and orderly manner. The composite moduli have been analysed by using the fabric geometry model and compared with the experimental results. The material characterization has been carried out on the basis of flexure, short-beam and compression tests. Damage configurations and accumulation for each loading case have been examined. Unique features include pull-in and push-out of the rods, which are the dominant modes in the short-beam tests. Buckling of the rods is the major damage in the flexure and compression tests. The buckled rods form kink bands analogous to fiber microbuckling in compressed unidirectional composites. The kink bands were found to propagate along the interlacing loops on the surface. These unique damage characteristics associated with the use of the rods are discussed in detail.

Structure-Performance Analysis of Two-Dimensional Woven Fabric Composites

A revival of interest in woven fabric composites has been observed in recent years. However, our understanding of their elastic and strength behaviour is still in its infancy. Modelling starts with the creation of a three-dimensional geometric model of the fabric structure. This analysis results in a logical and automated partition of the unit cell into a number of micro-cells, and the prediction of local fibre volume fractions and yarn orientations. Through the application of a modified Fabric Geometry Model, the full set of elastic constants for the orthotropic material unit cell is obtained. A parametric study was performed to understand how the different geometric parameters of the fabric can be combined to determine the elastic behaviour of the composite material.

Structure-Performance Analysis of Two-Dimensional Woven Fabric Composites

A revival of interest in woven fabric composites has been observed in recent years. However, our understanding of their elastic and strength behaviour is still in its infancy. Modelling starts with the creation of a three-dimensional geometric model of the fabric structure. This analysis results in a logical and automated partition of the unit cell into a number of micro-cells, and the prediction of local fibre volume fractions and yarn orientations. Through the application of a modified Fabric Geometry Model, the full set of elastic constants for the orthotropic material unit cell is obtained. A parametric study was performed to understand how the different geometric parameters of the fabric can be combined to determine the elastic behaviour of the composite material.

Modification and application of a unit cell continuum model to predict the elastic properties of textile composites

The unit cell continuum model, presented by Foye, is based on the principles of finite element analysis using heterogeneous hexahedra brick elements to predict the elastic properties of textile composites. The use of heterogeneous elements, consisting of fibres, and matrix, often introduces mathematical instabilities in the solution due to the large difference in the stiffness of the fibres and matrix. This can reduce the accuracy of the results. In this paper a solution is presented to this problem. The solution is based on a micro-level homogenization approach utilizing a fabric geometry model. Moreover, this approach is integrated with a geometric model, based on processing science modelling, to ensure accurate representation of complex fabric preforms. Test results for in-plane elastic properties of a five-harness satin weave carbon/epoxy composite and a three-dimensional weave E-glass/poly(vinyl ester) composite were compared with mechanical predictions using this approach and gave matching results

A three-dimensional micromechanical analysis of woven-fabric composites: II. Elastic analysis

Textile modelling begins with the creation of a geometric model of the woven-fabric structure which results in the micro-cell meshing of the unit cell, and the prediction of the local fibre volume fractions, the fractional volumes and the yarn orientations. We shall demonstrate that the classic fabric geometry model, which links the fabric geometry with the three-dimensional stiffness matrix of the composite unit cell, is incapable of predicting correct shear moduli for woven-fabric composites. In this paper, a new analytical model is proposed to predict accurate values for all engineering constants. Comparisons with finite element models were performed to establish the validity of the theory. A user-friendly custom Microsoft Excel® application (TEXCOMP) has been developed to transform the model into a useful design tool.

Thermal conductivity of composite materials made from plain weaves and 3-D weaves

In this research activity, thermal conductivity of textile composites made from plain weaves and 3-D XYZ weaves is quantified. Plain weave composites are made from E-glass, Kevlar® and AS4 graphite fibers and epoxy resin. 3-D woven composites are manufactured from Toho graphite fibers and epoxy resin. The effect of fiber type and fiber volume fraction on the thermal conductivity of textile composites is investigated.The fabric Geometry Model is adapted to calculate the thermal conductivity of textile composites. Results using this tool are compared with experimental data and predictions using the Graphical Integrated Numerical Analysis. The analytical approach proved to be a good engineering tool to predict the thermal conductivity of textile composites.

A Self-Consistent Fabric Geometry Model: Modification and Application of a Fabric Geometry Model to Predict the Elastic Properties of Textile Composites

A method for predicting the elastic properties of textile-reinforced composites is presented with applications. The method is a modification of a Fabric Geometry Model (FGM) [1–3] that relates fiber architecture and material properties of textile-reinforced composites to its global stiffness matrix through micromechanics and stiffness averaging technique. The FGM, although proven to be a quick and successful method [4], suffers two major drawbacks: 1. incompatibility of the basic transverse isotropy assumption with the theoretical mathematical derivation, (i.e., the mathematical derivation produces elastic constants that do not exhibit transverse isotropy) and 2. inconsistency of the transformation matrices associated with the stiffness calculations (i.e., the technique is not sufficiently robust to handle all cases). In this paper, these problems are discussed and solutions are presented. Comparison between stiffness and compliance averaging approaches is investigated. Moreover, predictions using the Self-Consistent FGM are compared with experimental data available in literature.

Engineering Design of Tough Ceramic Matrix Composites for Turbine Components

This paper provides a review of the material design concepts for the toughening of ceramic matrix composites by three-dimensional fiber architecture. To establish a communication link between the structural and the materials engineers, an integrated design methodology is presented with an example. Through a Fabric Geometry Model (FGM), the contribution of three-dimensional fiber architecture is translated into a stiffness matrix for finite element structural analysis. With the feedback from the structural analysis, this design methodology provides an effective means to screen reinforcement materials systems for three-dimensional fabric-reinforced composite components.