Preparation, Thermal, Mechanical, and Ablative Properties of a Bis‐Silane Modified Phenolic Resin Aerogel and Its Quartz Fiber Composite Material

ABSTRACT As the velocity of aerospace vehicles increases and the service environment of thermal protection systems (TPS) becomes more severe, there is an urgent need to develop lightweight materials that are resistant to ablation in oxidizing atmospheres over extended periods. This study employs a sol–gel method combined with atmospheric pressure drying (APD) to incorporate dimethoxymethylphenylsilane (DMMPS) and the silane coupling agent 3‐isocyanatopropyltrimethoxysilane (IPTS) for preparing a bis‐silane‐modified phenolic resin aerogel (DPRA x ) and its quartz fiber composite (DPRA x /QF). IPTS enhances the compatibility between siloxane and resin, improving mechanical and thermal properties. The aerogels exhibit low density (0.38–0.47 g/cm 3 ) and high porosity (> 70%). DPRA 5 shows enhanced thermal stability (57.62% char yield at 1000°C in N 2 ) and mechanical strength (compressive strength: 10.28 MPa; flexural strength: 9.16 MPa). Its composite displays excellent ablation resistance, with a backside temperature below 100°C under 44 kW stable output power and only 69°C after 2 min of 1300°C butane flame ablation. The dual‐silane modification synergistically improves high‐temperature stability and ablation performance, demonstrating potential for aerospace thermal protection systems.