Failure locus of 3D four-directional braided composites under biaxial loading

The failure locus of 3D braided four-directional composites under complex loadings, such as tension-shear, compression-shear and tension-tension, can be obtained by micromechanical computation model. A finite element model of representative volume cell (RVC) of the braided composites, explicitly taking into account the braid yarn and matrix, is chosen to analyze the mechanical response. The failure mechanisms of the braided composites observed in experiment can be reproduced by the numerical computation in which the mesoscopic damage models of the braid yarn and matrix are developed. Several failure points of the braided composites under the biaxial loadings can be obtained when different stress ratios are imposed upon the RVC. In comparison with the Tsai-Wu and Tsai-Hahn criteria, the numerical failure loci of the braided composites except the tension-tension results are in good agreement with those results. It can be pointed out that the failure loci of the braided composites can be obtained by the numerical fitting of a large number of the failure points which are calculated by the numerical model.