Pore scale heat transfer and flow mechanism of ablation process for low density resin based thermal protection materials

Understanding the heat transfer and flow mechanisms during ablation is essential for designing efficient thermal protection systems. Low-density needled quartz felt/phenolic resin (NQF/PR) materials, known for their low thermal conductivity and lightweight properties, are widely used in aerospace vehicles such as hypersonic glide bodies. Due to the nonlinear, multi-physics, and multi-scale nature of the ablation process, the pore-scale mechanisms—such as resin pyrolysis, gas flow through the porous matrix, and heat transfer between resin and fibers—remain unclear. This study conducts ablation experiments and material characterization to examine the physical properties of NQF/PR. Using CT scans on samples exposed to medium-low heat flux, the pore-scale structure is reconstructed. Based on this, a pore-scale evolution model is developed that incorporates fiber and pore geometry and tracks dynamic property changes during ablation. The model accurately captures the thermal response of NQF/PR. Results show that the ablative surface initially becomes denser before transitioning to a more porous structure. Macroscopic pores formed during ablation lead to gas aggregation and influence pyrolysis gas escape velocity. These insights enhance the understanding of ablative behavior and may provide a useful reference for future studies on the design of NQF/PR-based thermal protection systems.