A previous work4 outlined a new approach for perform microscale simulations of space craft thermal protection system (TPS) materials. This approach uses the Direct Simulation Monte Carlo (DSMC) method to accurately model the flow of gas through the porous media, which in many cases is rarefied. In this paper, we outline an efficient and robust new method for allowing the fibers in a microstructure to ablate due to chemical reactions at the surface. This method is applied to doing high fidelity coupled gas and material simulations, and the results of these qualitatively reproduce the expected morphologies in the diffusion limited and reaction limited regimes. The approach is also applied to simulating the flow through microstructures obtained from X-ray computed micro-tomography. The results show that these simulations are feasible at relevant scales and conditions.