多相纤维增强酚醛树脂低密度烧蚀防热复合材料高温压缩性能及损伤机制

低密度烧蚀防热材料是航天飞行器热防护系统的关键候选材料，其高温力学性能是热防护结构在气动热载荷下结构完整性的关键。本文针对多相纤维增强酚醛树脂低密度烧蚀防热复合材料开展高温压缩性能实验，获得了其压缩强度随温度的变化规律，结合热重、SEM分析了力载荷、热解及氧化反应对压缩强度的影响，揭示了软相碳层弥合和纤维脱黏、拔出两种韧化机制，为多相纤维增强酚醛树脂低密度烧蚀防热复合材料在热防护系统的工程应用提供实验数据支撑。 

High temperature compressive property and damage mechanism of low density multiphase fiber reinforced phenolic resin ablative thermal protective composite

Low-density ablative thermal protection material is a key candidate material for spacecraft thermal protection systems. Its excellent high-temperature mechanical properties are the key to structural integrity of thermal protection structures under aerodynamic thermal loading. In this paper, the low-density ablation thermal protection composite of multiphase fibers reinforced phenolic resin composite was used to carry out compression experiments at high temperatures to obtain the variation law of the compressive strength with temperature. The influence of force load, pyrolysis and oxidation reaction on compressive strength was analysised by thermogravity and SEM. Two kinds toughening mechanisms of soft phase carbon layer bridging and fiber debonding and pull-out are revealed, which provides experimental data support for the application of the composite in thermal protection systems.