Mechanical behavior of triaxial woven fabric (TWF) composites

This study is to explore the mechanical behavior of TWF composites. It covers following five aspects: (1) Two finite element models (Superelement 1 and Superelement 2) were developed for prediction of mechanical behavior of TWF composites. Superelement 1 is a 15-node superelement constructed of six identical 8-node 3D isoparametric elements and three identical 4-node 2D isoparametric laminate elements. Superelement 2 is similar to the first element except that this element takes into account the geometric and material properties of the twisted yarns. The assembly is done by the pseudo element technique suggested herein and the static condensation procedure. Superelement 1 can be used for the vibration analysis with some economy of computer space and time. Superelement 2 can be used for detailed stress analysis and for strength prediction. Although these two elements are developed for the TWF composites, they can be applicable for analytical models for other materials and structures made of other types of textile composites. (2) A series of experiments were done to obtain the tensile elastic constants of the TWF composites done by another person. Finite element models (Superelement 1 and Superelement 2) developed for the TWF composites were used to provide results for comparison with experiments. The effects of sizes and aspect ratios of TWF panels on their Young's modulus and Poisson's ratio are studied. (3) Thermal deformation behavior of TWF composites is modeled using Superelement 2. Thermal deformation behavior and Thermal Expansion Coefficients (TECs) of the TWF composites are evaluated. Effects of the aspect ratios and size of the panels on the TECs are studied. (4) The mechanical behavior of a sector of the reflector subjected to uniform pressure is studied by modeling several different-scale sectors using Super-finite elements. (5) Progressive failure of TWF composite panels subjected to uni-axial extension is studied numerically and experimentally. TWF panel is discretized respectively using linear and nonlinear Super-Finite-Elements proposed here. Tensor polynomial progressive failure procedure is employed with maximum stress, Hoffman and Tsai-Wu criteria. Two displacement-loading cases were considered. The first and ultimate failure loads, maximum extension displacement, locations and modes of failure are estimated and compared well with experimental data.