Macro-and Micro-analysis Of Mechanical Properties Of Woven Composites

Mechanical properties of woven composites were studied theoretically, numerically and experimentally in this thesis.The method for determining the micro architectures of various 2D and 3D woven composites via weave parameters has been presented. Based on this method, a FEM model library has been built by using PCL(Patran Command Language). With this library, micro FEM models of woven composites could be generated automatically. Most micro mechanical analyses of textile composites are based on cell model method. The applicability of this method depends largely on boundary conditions applied on the cell. In this thesis the criterion of selecting unit cell and general periodic boundary condition is discussed. Analysis focused on the effects of free boundary, local damage and random stacking on the average stiffness and micro stress distributions of composites. The modifications of boundary conditions in these cases were suggested.Viscoelastic properties of 3D woven composites were investigated in multi-scope. Firstly, visco-constitutive law of resin material was constructed which verified by experimental data. Then transverse isotropic viscoelastic theoretic-al model of yarn was suggested. This model was corrected by 3D micro FEM. Finally, creep behavior of a 3D woven composite has been researched and its characterized displacement/time curves under various loading density was obtained. A micro FEM model, combining with the constitutions of resin and yarn suggested previously was constructed to simulate the creep test numerically.