High-Silica Fiber Felt/Ti3SiC2 Reinforced Phenolic Aerogel Composites for High-Temperature Thermal and Mechanical Performance

To address the critical limitation of insufficient high-temperature structural stability in traditional formaldehyde-resorcinol aerogels for thermal protection applications, this study designed and fabricated a high-silica fiber felt-reinforced phenolic aerogel composite capable of in situ ceramization. The thermal insulation performance, structural stability, mechanical properties, and oxidation resistance mechanism after heat treatment at 1000 °C for 600 s were systematically investigated. Results demonstrated tunable density (0.398–0.629 g·cm−3), low room-temperature thermal conductivity (0.0414 W·m−1·K−1), and a stabilized back temperature of 408.6 °C during butane torch flame testing. After high-temperature treatment, the composite series exhibited a minimum volume shrinkage of 13.9% and a maximum mass retention of 77.6%. Specifically, the compressive strength and specific strength of the HS/C-75 sample reached 4.39 and 1.96 times those of the HS/C-0 sample, respectively. Further analysis revealed that the synergistic effect between the skeletal support of high-silica fibers and the in situ-formed ceramic phase effectively suppressed thermal shrinkage and improved oxidation resistance, achieving an optimized balance between thermal insulation and mechanical integrity. This work provides a theoretical foundation and viable technical pathway for developing advanced thermal protection materials with enhanced stability and reliability.