Fabrication and Characterization of Boron‐Modified Resorcinol–Furfural Aerogel Composites for Aerospace Ablation Applications

ABSTRACT Ablative polymeric composites were fabricated by impregnating resorcinol–furfural (RF) and phenylboronic acid‐modified RF (RFB) matrices into needle‐punched carbon fiber felts. The effect of boron incorporation on microstructure, thermal stability, mechanical behavior, and ablation performance was systematically investigated. Scanning electron microscopy (SEM) results showed reduced matrix defects and improved fiber–matrix adhesion after boron modification, while thermogravimetric analysis (TGA) revealed an increase in char yield from 36.5% to 39.79%. Although increased hexamethylenetetramine (HMTA) content led to reduced flexural strength due to enhanced porosity, boron incorporation improved structural integrity. The composites exhibited low densities (0.41–0.57 g cm −3 ), indicating suitability for lightweight thermal protection systems. Under oxyacetylene flame (~2070°C–2730°C), boron modification significantly improved thermal shielding, reducing the surface and mid‐surface temperatures from 2603.3°C (C‐RF8) to 2070.9°C (C‐RFB20) and from 241.7°C (C‐RF8) to 127.4°C (C‐RFB20), respectively. The C‐RFB25 composite exhibited low ablation rates (0.00658 mm s −1 and 0.0242 g s −1 ) and maintained a low back‐surface temperature (~26.5°C). The enhanced ablation resistance is attributed to the formation of a stable char layer and boron‐derived phases (B 2 O 3 ), which effectively seal cracks, suppress oxidation, and reduce heat transfer. These findings highlight the critical role of boron modification and interfacial engineering in the design of advanced ablative composites for high‐temperature applications.