Bioinspired fabrication of lightweight gradient ceramizable phenolic aerogel composites with exceptional ablation resistance and thermal insulation for superior thermal protection system

Lightweight carbon fabric-reinforced phenolic aerogel composites (LCPA) have been considered as the promising candidates for thermal protection materials at ultra-high temperatures due to their low density and good ablation property. However, the application of LCPA was restricted by its complex fabrication process, poor antioxidation performance and poor mechanical robustness. This work offered a bionic strategy for producing gradient ceramizable phenolic aerogel composites (GCPAs) by the combination of antioxidative coating treatment and ceramic slurry manipulation, achieving simultaneously low density, mechanical robustness, superior ablation resistance and thermal insulation. The composite had a substantially lower density (0.76 g/cm³) than the homogeneous ceramizable polymer matrix composite. The mass and linear ablation rates of the obtained composite after ablation at 2500 ℃ for 20 s were 0.083 g/s and 0.046 mm/s, decreased by 27.0 % and 33.7 % compared with those of the primary phenolic aerogel composite. The enhanced ablation and thermal insulation performance was due to the combination of multiphase ceramic layer formed on the composite surface at high temperature and the abundant micro-nano pores/ interfaces inside the composite. This work has great prospects in the fabrication of lightweight phenolic aerogel composites applied in thermal protection system fields.