Multi-scale modeling of moving interface problems with flux and field jumps: Application to oxidative degradation of ceramic matrix composites

摘要

Problems involving reaction and species diffusion involve field and flux jumps at a moving reaction front. In multi-scale problems such as carbon fiber composite oxidation, these effects need to be tracked at the microscopic scale of individual carbon fibers. A multi-scale model is derived in this paper for predicting species distribution in such problems using a fully coupled multi-scale homogenization approach. The homogenized fluxes from the micro-scale are derived using Hill's macro-homogeneity condition accounting for both flux jumps and species density field jumps at the reacting interface in the micro-scale unit cell. At the macro-scale, the competition between the transport of reacting species (oxygen) and the reaction product (carbon dioxide) is modeled using homogenized mass conservation equations. The moving reaction front in carbon fibers at the micro-scale is tracked using level set method and an adaptive meshing strategy. The macroscopic weight loss of the composite when exposed to oxygen is simulated as a function of time using a coupled finite element methodology at various locations in a validated macroscopic model.