Synergistic toughening and thermal stabilization of ESR/PR composites via epoxidized hollow glass fiber reinforcement

Thermal protection materials for high-speed aerospace vehicles require a combination of excellent heat resistance, mechanical reliability, and lightweight characteristics. In this work, epoxidized hollow glass fibers (HGF) were incorporated into an epoxy silicone resin/phenolic resin (ESR/PR) hybrid resin matrix to overcome the intrinsic brittleness and high density of conventional phenolic-based composites. The successful grafting of epoxy functional groups onto the fiber surface enables strong interfacial bonding through co-crosslinking reactions with the ESR/PR matrix. Meanwhile, the hollow structure of HGF reduces density and provides intrinsic thermal insulation. The optimized ESR/PR-15HGF composite exhibits a tensile strength of 50.4 MPa (12.5 % improvement compared to ESR/PR matrix), elongation at break of 3.2 %, and a high specific strength of 3.97 × 10 4 m 2 /s 2 , achieving superior performance at lower filler content compared to solid glass fiber systems. Thermogravimetric analysis further reveals enhanced thermal stability, with a higher decomposition temperature (428 °C) and increased char yield (78.6 %). These improvements arise from the synergistic effects of enhanced interfacial interactions, fiber reinforcement, and hollow structure-induced thermal insulation, offering a promising strategy for advanced lightweight thermal protection materials.