Mixture model for thermo-chemo-mechanical processes in fluid-infused solids

This work presents a new thermodynamically consistent model for thermo-chemo-mechanical processes in open systems comprised of nonlinear elastic solids that are infused with reactive fluids and are undergoing large local strains. The interactions between different constituents of the material system are captured through locally homogenized mixture theory. The development of the formulation starts from constituent-wise balance equations for mass, momentum, and energy. The constitutive relations are derived to enforce non-negative entropy production and satisfy the second law of thermodynamics for the open system. The deformation due to thermal and chemical effects is carried out through a multiplicative split of the deformation gradient. Further assumptions on the fluid and solid material responses are introduced to specialize the model to a class of thermo-chemo-mechanical processes that arise in thermal oxidation of metallic and ceramic materials, lithiation of battery anodes, and other related problems. The model is implemented in the standard Galerkin finite element method using eight node hexahedral elements. A set of test cases involving fully coupled thermo-mechanical, chemo-mechanical, and thermo-chemical effects are analyzed. Numerical results obtained are in reasonable agreement with the experimental data for thermo-chemo-mechanical problems concerning the thermal oxidation of silicon carbide and FeCrAlY bond coat material in thermal barrier coatings.