Discontinuous ablation behavior of four-directional dual-matrix C/C composites under dual-pulse solid rocket motors

• Four-directional dual-matrix C/C composites exhibit a unique hexagonal carbon rod structure surrounded by a dense PyC wall, contributing to their ablation resistance. • The linear ablation rates after pulse I and pulse II were 0.068 mm/s and 0.113 mm/s, respectively, indicating a discontinuous ablation behavior under dual-pulse conditions. • A cellular-like PyC layer and nanowire structures form on the throat convergent section during post-combustion cooling, while cracks and delamination occur in the divergent section. • Ablation under dual-pulse SRM conditions involves a complex multi-mechanism process including ultra-high temperatures, high-speed gas scouring, thermochemical oxidation, and thermal shock.