Micro-scale thermal-structural modeling for carbon fibers

With regards to Thermal Protection System, the thermal-structural responses of the modern ablative materials are of primary importance in many aspects, including material selection and sizing. Due to the intricate nature of its porous structure and complicated thermal conditions, ablative materials may exhibit unexpected behavior, which can potentially lead to material failure. In this study, two solvers – a direct simulation Monte Carlo solver and a finite-volume based Material Response solver – are coupled together to predict the micro-scale thermal-structural performance of a Thermal Protection System material. In this approach, individual fibers are modeled at the micro-scale, which provides valuable knowledge of the porous media behavior. Non-uniform boundary conditions, including the heat flux and external force, are captured by the Direct-Simulation Monte-Carlo solver, and the detailed thermal and structural performance of the fiber is captured by the Material Response solver. The results show that individual fibers do not fail based on temperature gradient and applied aerodynamic forces. However, it is shown that attachment points of the fibers are the most vulnerable. This vulnerability can lead to breakdown of the binders, which would separate fibers and cause material collapse.