Crack Modeling in Charring Ablation Materials

Modern Thermal Protection Systems (TPS) used for planetary exploration missions often utilize lightweight porous materials as their isolating layer. An unexpected failure of the TPS material could potentially result in disastrous loss and cause the mission to fail. Therefore, it is of paramount importance to accurately understand how and when these porous materials could break. In this study, a material property model is proposed to represent the widely used ablative materials. Based on that, a crack model is developed and implemented into a material response solver for the charring ablation problem. A replicate experimental case on FiberForm is conducted using the developed model. Results show that the proposed material property model and crack mechanism are very effective to capture the crack propagation within the material. Additional test results show that a higher level of scattering in material properties leads to more localized failures, earlier material breakage, and more crack branching. The impacts of the material ultimate strength and the level of loading strain rate are also numerically investigated. The ultimate strength is a direct factor determining if a crack can initiate while the strain rate can affect the crack propagation pattern.