Continuum description of damage in ceramic-matrix composites

A constitutive law is proposed for Ceramic-Matrix Composites which models matrix-cracking, interface debonding and sliding, fiber-breakage, and fiber pull-out. These different mechanisms induce loss of stiffness, inelastic strains, hysteresis loops, and crack closure. The features are analyzed within the framework of Continuum Damage Mechanics by the introduction of physical internal variables identified previously in material science investigations. The procedure is applied to a SiC/SiC [0/90] laminate composite using the results of pure tension tests of two laminate orientations. Each test involves a series of loading and unloading sequences. In order to verify the material description the behavior of an Iosipescu shear test is predicted using a Finite Element calculation and the results are compared with experiment.