Lightweight SiBCN-modified carbon-bonded carbon fiber composites with directional heat-leading function for efficient thermal protection

Hypersonic vehicles are subjected to critical aerodynamic heating during flight, posing a substantial challenge for the design of thermal protection systems (TPS). Carbon-bonded carbon fiber (CBCF) composites are highly valued materials for TPS in aerospace and military contexts due to their lightweight structure and exceptional dimensional stability at elevated temperatures. However, they are constrained by a limited capacity for in-plane heat dissipation, which restricts their application under extreme thermal gradients. Therefore, incorporating enhanced in-plane directional heat leading capabilities into CBCF composite designs represents a highly innovative approach that is expected to alleviate local thermal stress and achieve efficient thermal management. Herein, we propose a multifunctional design strategy by fabricating SiBCN-modified carbon-bonded carbon fiber composites (CBCF/SiBCN) through integrating high-efficiency in-plane heat conduction pathways with anisotropic thermal insulation structure. The preparation process, microscopic morphology, mechanical response and thermal performance of the CBCF/SiBCN composites were systematically investigated. The fabricated samples exhibited compressive strengths of 4.05–4.36 MPa in the in-plane direction and 1.30–1.36 MPa in the through-the-thickness direction, while maintaining a low density of 0.48–0.49 g·cm^-3. Notably, the in-plane thermal conductivity of CBCF/SiBCN reached to 60.9–61.5 W·m^-1·K^-1 while remaining at 0.08 W·m^-1·K^-1 in the direction of thermal insulation, demonstrating a typical anisotropy and indicating significant potential for effective thermal management. The paper introduces an innovative design that focus on the development of in-plane directional heat leading properties for thermal insulating composites, which potentially meets the critical requirements for thermal protection in aerospace applications.