Multiphysics modeling for local structural heat source and high-speed airflow coupled ablation behavior of the lightweight quartz fiber-reinforced phenolic (LQFRP) composite

When the lightweight quartz fiber-reinforced phenolic (LQFRP) composite is subjected to the combined effect of a local structural heat source and high-speed airflow, its ablation behavior exhibits significant localized characteristics and strong coupled effect. In this study, we have developed a bidirectional loosely coupled numerical model that integrates thermal, fluid, solid and ablation phenomena to solve the ablation-through problem of the LQFRP composite. The model takes into account the mechanisms of pyrolysis, oxidation, sublimation, and thermal mechanical erosion that occur during the ablation process of the LQFRP composite. The results suggest that the local structural heat source plays a crucial role in the erosion and retreat of the LQFRP composite. The morphology of the ablation pit shows a noticeable asymmetry, which is attributed to the aerodynamic heat and force. As a result of the local structural heat source, the fluid temperature downstream of the ablation pit is higher compared to that upstream of the ablation pit. The fluid that flows downstream of the ablation pit undergoes significant compression, leading to the formation of an oblique shock wave. The distribution of resin pyrolysis degree within the LQFRP composite is influenced by internal heat conduction. This study will offer valuable insights and guidance for the practical application of the LQFRP composite in the ultra-high temperature field.