Rationalized Improvement of Tsai–Wu Failure Criterion Considering Different Failure Modes of Composite Materials

Abstract Different failure modes are not explicitly accounted for in the Tsai–Wu failure criterion for composite materials, and the factor F12 in the expression cannot be determined by the basic strength values of the materials. In view of these two shortcomings of the Tsai–Wu criterion, an improved criterion was proposed based on the reasonable assumption that composites exhibit infinite strength under pure hydrostatic pressure. Some coefficients in the quadratic tensor expression of the Tsai–Wu failure criterion are redetermined using the basic strength value of the material, including the coefficient F12, under four different stress states (fiber tension and compression, matrix tension and compression). The reconstructed Tsai–Wu failure criterion can distinguish the failure modes based on different coefficient values under different stress states. In the progressive damage analysis of composite materials, the stiffness can be reduced in different manners based on each failure mode. Experimental verification for different kinds of unidirectional composites under various stress states was conducted, demonstrating that the improved Tsai–Wu failure criterion has a better prediction ability and accuracy than the original criterion.