A damage-induced short-circuit diffusion model applied to the oxidation calculation of ceramic matrix composites (CMCs)

In this paper, a chemo-thermal-mechanical coupled constitutive model is proposed for CMCs in an oxidizing environment. For ceramic matrix, the initiation and evolution of micro-cracks are described by a damage constitutive model. The diffusion coefficient of O₂ molecules in the ceramic matrix is modelled as a function of the damage factor based on the simplifying assumption for the actual physical processes. For reinforcement materials, the oxidation reaction is taken into account, and an oxidation degree-dependent orthotropic constitutive model is adopted. Furthermore, the corresponding finite element calculation procedure is developed based on the Galerkin method and the Newton-Raphson iteration scheme. Then, as examples, the coupled failure problems of a SiC-coated C fibre monofilament and a representative volume cell (RVC) of C/SiC composites, and the oxidation process of C/SiC specimens, are studied in depth.