Woven Fabric Composite Materials Research Articles

Fiber Reorientation in Laminated and Woven Composites for Finite Element Simulations

A simple technique for fiber reorientation in laminated and woven composite material is presented in this paper. This technique is suitable for nonlinear finite element simulations of composite structure failure. The developed technique is implemented in the nonlinear explicit finite element code DYNA3D to demonstrate the effect of the fiber reorientation on the behavior of laminated composite materials in crash simulations. The same technique is added to a woven fabric composite material micromechanical model to account for the change of the model geometry. Using an incremental approach programmed in the MATLAB software, the stiffness change of the woven composite micromechanical model as a function of the yarn tow reorientation is investigated. Significant change in the elastic properties is observed as a result of the scissoring effect and fiber reorientation in woven fabric composites.

A three-constituent multicontinuum theory for woven fabric composite materials

Multicontinuum theory (MCT) refers to the use of phase averaged constituent stress/strain fields for predicting failure in composite structural analysis. Given the composite material mechanical properties as well as those of the constituents, well known closed form algebraic expressions exist to decompose the composite stress/strain fields down to the constituent level. Recent research indicates constituent based failure algorithms show a great deal of promise in predicting material failure when coupled to nonlinear finite element codes. A limitation of MCT is that the traditional constituent decomposition is only valid for materials composed of two constituents. In this paper, the MCT decomposition is generalized to handle composite materials composed of three constituents. The application of interest is a woven fabric composite material. The three constituents consist of the warp bundles, fill bundles, and pure matrix pockets. Numerical results are presented for the proposed three-constituent decomposition and are shown to be in good agreement with phase averaged stresses obtained from direct volume averaging of finite element micromechanics models.

Strength Simulation of Woven Fabric Composite Materials with Material Nonlinearity Using Micromechanics Based Model

The objective of the current investigation is to predict failure strength of woven composites, which considers the 2D extent of woven fabric, based on micro-mechanics. The formulation has an interface with nonlinear finite element codes. At each load increment, global stresses and strains are communicated to the representative cell and subsequently distributed to each subcell. Once stresses and strains are associated to a subcell they can be distributed to each constituent of the subcell (i.e., fill, warp, and resin). Consequently, micro-failure criteria (MFC) are defined for each constituents of a subcell and the proper stiffness degradation is modeled. Different stages of failure such as warp transverse failure, fill transverse failure, failure of pure matrix in longitudinal and shear, shear failure in fill and warp, and fiber in fill and warp in longitudinal tension are considered. Good correlation is observed between the predicted and the experimental results presented in the published literature. This material model is suitable for implicit failure analysis under static loads and is being modified for explicit finite element codes to deal with problems such as crashworthiness and impact.

Finite element analysis of damaged woven fabric composite materials

Since fiber reinforced composite materials have been used in main parts of structures, an accurate evaluation of their mechanical characteristics becomes very important. Due to their anisotropic nature and complicated architecture, it is very difficult to reveal the damage mechanisms of these materials from the results of mechanical tests. Therefore, there is a need to conduct reliable simulations and analytical evaluations. In this paper, the damage behavior of FRP is simulated by finite element analysis using an anisotropic damage model based on damage mechanics. The proposed procedure is applied to an example; the finite element analysis of microscopic damage propagation in woven fabric composites. Experimental tests have been conducted to evaluate the validity of the proposed method. It is recognized that there is a good agreement between the computational and experimental results, and that the proposed simulation method is very useful for the evaluation of damage mechanisms.

Materially and geometrically non-linear woven composite micro-mechanical model with failure for finite element simulations

A computational micro-mechanical material model of woven fabric composite material is developed to simulate failure. The material model is based on repeated unit cell approach. The fiber reorientation is accounted for in the effective stiffness calculation. Material non-linearity due to the shear stresses in the impregnated yarns and the matrix material is included in the model. Micro-mechanical failure criteria determine the stiffness degradation for the constituent materials. The developed material model with failure is programmed as user-defined sub-routine in the LS-DYNA finite element code with explicit time integration. The code is used to simulate the failure behavior of woven composite structures. The results of finite element simulations are compared with available test results. The model shows good agreement with the experimental results and good computational efficiency required for finite element simulations of woven composite structures.

Comparative study of predictive methods for woven fabric composite elastic properties

Several methods used to predict the elastic properties of woven fabric composite materials are compared and a new one is presented. The compared methods are the method of cells and the four-cell method presented earlier by the principle author and the three-dimensional finite element method. The new method is a simplified version of the method of cells for woven composites. The four-cell method and the simplified method of cells are the most computationally efficient method as compared to other methods. Specifically, the four-cell method can directly be used in finite element codes to predict structural behavior of components mode of woven composites. Where as the local/global finite element/finite element procedure is very costly which prohibits using it in structural analysis of woven composites. Numerical results are generated for engineering constants by the considered methods and compared to each other. Good agreements are obtained using the presented new method with respect to the other methods of cells and the finite element results.

On the Damage Behavior of Fiber Reinforced Composite Materials

Since fiber reinforced composite materials have been used in main parts of structures, an accurate evaluation of their mechanical characteristics becomes very important. Due to their anisotropic nature and complicated architecture, it is very difficult to reveal the damage mechanism of these materials from the results of mechanical tests. Therefore, there is always a big need to conduct reliable simulations and analytical evaluations. In this paper, the damage behavior of FRP is simulated by finite element analysis using an anisotropic damage model based on damage mechanics. The proposed procedure is applied to two examples; the finite element analysis aided AE damage simulation and the finite element analysis of microscopic damage propagation in woven fabric composite materials. Experimental tests in both cases have been conducted to evaluate the validity of the proposed method. It is recognized that there is a good agreement between the analytical and experimental results, and that the proposed simulation method is very useful for the evaluation of damage mechanism.

織物複合材料の損傷進展解析ならびにその場ＳＥＭ観察

Although woven fabric composite materials have high performance, it is very difficult to reveal their mechanical behaviours due to the geometric complexity by theoretical analysis. Especially under damage development, several kinds of failure mode such as matrix cracking, fiber breaking and transverse cracking in fiber bundle affect the mechanical behaviour strongly. In order to analyze the mechanical behaviour, three-dimensional finite element analytical procedure based on damage mechanics has been developed. In this paper, the developed procedure is applied to plain woven fabric composites, and the mechanical behaviour under damage development by on-axis tensile load has been analyzed. On the other hand, on-axis tensile test has been performed in SEM and the damage development at the edge cross-section of specimen has been observed. As a result, it can be confirmed that the calculational and the experimental results have a good agreement. Then, the mechanical behaviour depends on the edge effect of free side surface. Therefore the effect of free edge has been evaluated quantitatively by numerical analysis from comparison with mechanical behaviour under periodic boundary condition without free side surface. From the above results, it is recognized that the proposed procedure is very useful for the material design of woven fabric composite materials.

Comparison of the ±45° Tensile and Iosipescu Shear Tests for Woven Fabric Composite Materials

The mechanical response of a woven eight-harness satin graphite/polyimide composite has been investigated by performing ±45° tensile and Iosipescu shear tests at room temperature. Nonlinear finite element simulations of the tests have been conducted to determine internal stress distributions in the ±45° tensile and Iosipescu fabric specimens as a function of load. In the experimental part of this study, a series of tensile and Iosipescu shear tests have been performed. Acoustic emission techniques have been employed to monitor damage initiation and progression in the composite. The finite element computations have shown that the internal stress distributions in the Iosipescu and tensile fabric specimens are significantly different. In the gage sections of Iosipescu specimens, the state of stress is essentially pure shear, whereas the tensile tests generate biaxial stress conditions. It has been shown in this research that the shear strength of the composite determined from the maximum loads obtained from the Iosipescu shear tests is significantly higher than the shear strength obtained from the ±45° tensile tests. Moreover, the initiation of intralaminar damage in the tensile specimens occurs at much lower loads than in the Iosipescu specimens. It appears that the ±45° tensile test significantly underestimates the shear strength of the composite evaluated from the onset of intralaminar damage and the maximum loads.

Discussion of “Woven fabric composite material model with material non-linearity for non-linear finite element simulation” by Tabiei and Jiang [Int. J. Solids Struct. 36 (1999) 2757–2771

Discussion of “Woven fabric composite material model with material non-linearity for non-linear finite element simulation” by Tabiei and Jiang [Int. J. Solids Struct. 36 (1999) 2757–2771

K-0921 重合メッシュ法による織物複合材料の局所的損傷進展解析(J05-2 強度・破壊機構解析(1))(J05 複合材料の加工と評価)

There have been many reports on the numerical analysis of damage propagation in woven fabric composite materials. However, most of them studied the behaviors under in-plane loading conditions including tension, compression and shearing. Because composite materials are often used as plates and shells, their out-of-plane bending behaviors are important. To study the micro- or mesoscopic damage propagation under bending, the consideration of micro-macro coupling is a critical issue. A small region to consider the microscopic behavior is subject to macroscopic non-uniform strain field under bending. Therefore, the conventional homogenizing technique is not applicable. In this paper, we propose a new computational method named finite element mesh superposition method to solve this problem. A two-dimensional example of plain woven fabric composites is shown in this paper.

Process induced stress for woven fabric thick section composite structures

A semi-numerical model was developed to simulate processing induced stress for woven fabric composite material structures. The approach consists three main parts. The first part was the simulation of resin chemical kinetic cure behavior and micromechanics for cure dependent resin and glass fiber. The second was the analytical extension of TEXCAD woven fabric micromechanics model (Naik RA. TEXCAD-Textile Composite Analysis for Design. NASA report 4639, December 1994) to cure dependent textile unit cell model. The last was the introducing of the effective unit cell properties to finite element structure modeling. Cure dependent material response includes thermoset resin hardening and volumetric shrinkage during cure. The approach was incrementally employed whereby the model predicts the composite fabric unit cell effective modulus, processing-induced strains and stresses (thermal expansion and chemical shrinkage) during cure. Case studies were presented which illustrate the effective modulus and processing stress/strain development during cure for a plain weave S2-glass/vinyl–ester composite laminate. An understanding of the complex relationships between cure, modulus and processing-induced stress/strain development represents a significant step towards optimizing processing strategies for thick-section woven fabric composite structures.

Mesoscopic Strength Evaluation of Woven Fabric Composite Materials by Homogenization Method and Anisotropic Damage Mechanics.

In this paper, a woven structure consisting of fiber bundles is defined as a mesostructure and we evaluate the strength of woven fabric composite materials mesoscopically by the homogenization method and anisotropic damage mechanics. A numerical simulation system for virtual strength test has been developed to predict the initial mesoscopic fracture, the fractured location in both macro and mesostructure and the fracture mode. The mesoscopic fracture mode is shown schematically, which greatly aids in the understanding of the mesomechanics of woven fabric composite materials. This system is effective for material and structure design and proves the necessity of considering the interaction between macro-and mesostructures. Furthermore, the formulation and a numerical example for mesoscopic fracture propagation considering the fracture mode are shown.

Three-Dimensional Microstructural Design of Woven Fabric Composite Materials by Homogenization Method. 2nd Report. Detailed Analysis of Microscopic Behavior under Bending Load.

For design and development of advanced textile composite materials, evaluation of their bending strength is essential. However, as far as we know, there has been no literature on the numerical simulation predicting the bending strength of textile composites. In this paper, we show a methodology for calculation of the bending strength for woven fabric composite materials by the homogenization method. Both the location and the cause of microscopic fracture in a fiber bundle and resin are discussed in detail. The effect of the pitch of woven fabrics on the bending characteristics is also noted.

Homogenization Analysis Method for Composites Considering Geometrical Nonlinearity and Fracture of Microstructure.

For the design and production of new advanced composite materials and structures, the need for numerical simulations of their mechanical behaviors is increasing. There are two requirements for the simulation. First, microstructural architectures must be considered. The homogenization analysis method, which is an applied mathematical method developed from late 1970's to early 1980's, seems to be the most appropriate method for modelling microstructures in current literature. The second requirement is the solution of nonlinear problems. Therefore, we have developed a nonlinear homogenization method where both geometrical nonlinearity due to large deformation of microstructures and material nonlinearity due to microscopic fractures are considered. The new formulation of the nonlinear homogenization method is based on a stepwise linear algorithm with initial stresses. Two examples, i. e., biomechanical problem and fracture behavior of woven fabric composite material, were solved.

微視破壊を考慮した均質化法による織物複合材料の非線形解析

Textile composites are becoming more and more important in engineering field. Need for computational simulations of their mechanical behaviors is also growing. In this study, a nonlinear homogenization method has been developed for the analysis of fracture behaviors of woven fabric composite materials.First, the mechanical behaviors of flat plates made from woven fabric composite materials were analyzed under various loading conditions, and then the reduction of modulus of elasticity by microscopic fracture was calculated precisely. Next, the nonlinear fracture analysis of a plate with an open hole was carried out. It is revealed that the knee points and notched strength are able to be predicted.

Three-Dimensional Microstructural Design of Woven Fabric Composite Materials by the Homogenization Method. 1st Report. Effect of Mismatched Lay-Up of Woven Fabrics on the Strength.

The strength of woven fabric composite materials depends on their microstructural geometry. However, the conventional methods for mechanical analysis, which have been widely used to date, are insufficient because they cannot take into account the three-dimensional microstructure. In this study, the three-dimensional homogenization method is shown to be effective for determination of the material constants, microscopic stresses and strength. It has been found that the transverse stress in the lamination direction plays an important role in the fracture of both the fiber bundle and the resin. Also, the effect of the mismatched lay-up on the strength has been investigated. It was predicted that the mismatched lay-up causes a reduction in strength and a difference of crack initiation in the resin. These simulations provide a new concept for the microstructural design of composite materials.

On deformation of woven fabric-reinforced thermoplastic composites during stamp-forming

The processability of woven glass fabric-reinforced composite plates by three-dimensional stamp-forming into spherical caps is theoretically considered from a geometrical point of view before and after the deformation process. For doing this, tensile properties of the material were measured under similar heat conditions as in the relevant stamp-forming process. Stretch in the fibre direction was found to be smaller than the maximum elastic extension of the glass fibres. Reduction of the angle between the crossing fibres was quite large when the satin woven fabric composite was pulled in the 45° direction. In theory, the material is assumed to attain maximum stretch along the meridian in the fibre direction on the formed dome. The curve in the flat plate before the deformation process, which will be formed into a parallel of latitude of the dome after stamp-forming, is obtained by an iteration scheme on the condition that the deformed length of the curve is equal to the circumferential length of the curve of constant latitude. A possible deformation of the spherical dome without serious wrinkling is obtained. The flexibility of the satin woven fabric composite material is found to be sufficient for the plate to be formed into a hemisphere, as long as the working condition is well controlled. A possible working condition during the stamp-forming is proposed.

Evaluation of woven fabric composites for automotive applications

This paper summarizes the results of a recent study [1] funded by the National Science Foundation to investigate the feasibility of woven fabric composite materials for automotive applications. By identifying the advantages and limitations associated with woven fabric composites and by comparison with current automotive materials, the potential for successful application of these materials is investigated. In particular, strength, fatigue, moldability, and cost effectiveness have been identified as critical indicators of the potential for these materials in automotive applications. The results of an experimental evaluation of the static and fatigue properties of woven composites and comparable unidirectional tape composite laminates are discussed. An analytic model designed to quantify the effect of fabric weave configuration on relative conformability to complex geometries is also presented. Preliminary component designs utilizing woven fabric composites are considered in terms of potential weight savings, potential fabrication methods, and projected cost effectiveness. Finally, the key factors impeding the successful implementation of these materials in particular automotive structural applications are identified and reviewed.