Experimental study of the mechanical erosion behavior of silicone rubber thermal protection system materials in high-temperature and high-speed two-phase flow environment

The mechanical erosion caused by gas flow in ramjet engines leads to thermal protection structure failure of silicone rubber thermal protection system (TPS) materials. In this study, mechanical erosion behavior of silicone rubber TPS materials was assessed in a high-temperature (2300 K) high-speed (300 m/s) gas-liquid (Al₂O₃ liquid phase particles) two-phase flow environment using a self-developed device. By comparing the ablated surface morphology and pore structure, it was observed that blowholes formed by the escape of pyrolysis gas, denudation pits caused by gas-phase, and erosion pits induced by liquid-phase particles all contribute to the degradation of the protective barrier effect of the molten SiO₂ layer. This degradation compromises its ability to block oxidizing components and adhere to resist particle erosion. The introduction of oxidizing components alters the pore structure within the ceramic layer, while particle erosion has a more destructive impact. The overall porosity in the central area of the two-phase flow test specimen is 2.37 times higher than that of the pure gas phase specimen. Theoretical analysis results indicate that momentum and energy transfer during the impact of Al₂O₃ liquid phase particles on the ablated surface are influenced by post-impact particle motion states, providing novel insights for enhancing mechanical erosion resistance performance of silicone rubber TPS materials.