Endothermic mechanism of silica/phenolic composite under ablative environment

Based on endothermic mechanism of silica/phenolic composite during ablation process, a theoretical prediction approach to analyzing the endothermic mechanism of materials under ablative environment was presented by combining surface ablation theory with boundary layer aerodynamics, and the semi-empirical formula of mass injection factor was used. The theoretical prediction approach was validated by means of oxyacetylene flame dynamic ablation experiment. According to the energy conservation principle of ablative material surface under steady-state of ablation condition, the proportion formula of each endothermic mechanism and the total heat absorption was derived. Under a given ablation environment condition, the proportion of each endothermic mechanism in the total heat absorption was predicted. The results show that the evaporation of melting silica fiber is the main endothermic mechanism, which account for 44.9% of the total heat absorption. The heat absorption of heat capacity of ablator occupies 22.3%, and heat radiation is up to 20.1% of the total heat absorption. Thermal decomposition of the resin gives the small contribution to the total heat absorption, which is 1.0%, while the thermal blockage effect of the pyrolysis gases injected into boundary layer account for a higher proportion of 11.7% to the total heat absorption.