Effects of polycarbosilane interface on oxidation, mechanical, and ablation properties of carbon fiber-reinforced composites

Polycarbosilane (PCS) was introduced onto carbon fibers as an interface layer to meet requirements for using carbon fiber-reinforced phenolic resin composites (CPR) at high temperatures. Bending strength of as-received CPR with PCS (CPRS) was 541 ± 16 MPa, which is lower than that of pure CPR. However, because of protective PCS interlayer, the strength of CPRS after oxidation at 800 °C for 0.5 h was 112 ± 4.3 MPa, which is about 60% higher than residual strength of pure CPR after oxidation under the same conditions. Resulting protective interlayer of PCS at high temperatures leads to fracture toughness improvement of approximately 40% for CPRS. CPRS showed better ablation resistance under oxyacetylene flame than did pure CPR. Comprehensive protective effects from PCS interlayer and resulting improved thermal conductivity of CPRS account for enhanced ablation resistance.