• • Linear ablation rates of 0.068 mm/s (pulse I) and 0.113 mm/s (pulse II) demonstrate a 66% increase in ablation rate under dual-pulse conditions, indicating cumulative damage that must be accounted for in thermal protection design.
• • The formation of a cellular-like PyC layer and carbon nanowires in the convergent section, catalyzed by ferrocene derivatives, reveals a deposition mechanism that can mitigate ablation but requires controlled pyrolysis conditions.
• • Debonding at matrix-fiber, carbon rod-PyC, and within the PDC matrix interfaces led to crack initiation and delamination in the divergent section, highlighting the need for improved interfacial bonding to prevent mechanical erosion.
• • The ablation process is characterized as discontinuous, involving high-temperature/high-velocity gas erosion, thermochemical ablation by oxygen-containing species, and thermal shock, necessitating multi-mechanism modeling for accurate lifetime prediction.