Enhanced ablation resistance of carbon/phenolic composites based on mesophase pitch reinforced particles

Phenolic resin (PR)-based composites are the main materials used in thermal protection system (TPS) at present. However, the low graphitization degree of the char layer formed by PR easily leads to cracks and other defects. In this study, carbon/phenolic composites were modified by mesophase pitch (MP) to improve the structural strength, fracture toughness and crack propagation resistance. The ablation rate was significantly decreased after MP modification compared with the blank sample. With the increase of MP, the size of cracks and char blocks on the ablation center of the composites were reduced, and the surface was flat and dense. The Interlaminar shear strength (ILSS) of carbonized composites (5 wt% MP) were 9.79 MPa, and the flexural strength was 121.5 MPa, which improved 62.9% and 40.8% relative to the pure sample. The flexural strength of 5 wt% MP-reinforced carbon/phenolic composites reached 525.6 MPa, which was 26.9% higher than that of pure carbon/phenolic composites, mainly due to the particle reinforcement effect of MP distributed between carbon fibers. The above results show that the carbon/phenolic composites modified by MP has great application prospects in the field of aircraft thermal protection.