A diffusion, oxidation reaction and large viscoelastic deformation coupled model with applications to SiC fiber oxidation

In this paper, we present a continuum-level thermodynamically consistent oxidation model that couples large viscoelastic deformation, diffusion and oxidation reaction. Constitutive equations are derived by means of the free energy inequality. The Eyring model for the shear stress dependence of viscosity is adopted to describe the viscous deformation. Subsequently, this model is applied to study the oxidation processes of SiC fibers. A sharp interface between the oxide and substrate naturally develops and propagates forward during the oxidation process. Furthermore, the stresses at the outer surface change from the initial compressive state to tensile due to the viscous deformation and significant volumetric swelling at the interface, which may explain the surface cracking observed in experiments. Notably, the present model can be conveniently used to simulate the oxidation processes that involve complex geometrical shapes without the need to mark and track the interface artificially.