Modelling of the mechanical behavior and damage processes of fibrous ceramic matrix composites: application to a 2-D SiC/SiC

A continuum damage mechanics constitutive model is developed to describe th e mechanical behavior of fiber-reinforced ceramic matrix composites submitt ed to complex multiaxial loadings. This model relies on the use of a phenom enological internal damage variable defined as the change of the compliance tensor induced by any given loading. Microstructural observations of the d amage entities provide qualitative data allowing us to formulate physically founded simplifying hypotheses. The evolution laws of scalar damage variab les derived from the components of the compliance tensor are established wi thin a classical thermodynamic framework, using coupled multicriteria expre ssed in the space of the associated thermodynamic forces. Damage deactivati on processes related to the unilateral crack closure effect observed under compressive loadings are introduced through the definition of effective com pliance tensor components. This approach is applied to a 2-D woven SiC/SiC composite processed by chemical vapor infiltration (CVI). Major advantages and drawbacks of the proposed approach as observed from various validation tests are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.