Dynamic Stress Damage Behavior of UHTC-Modified C/C Composites by Reactive Melt Infiltration Method

Carbon/carbon (C/C) composites modified with ultra-high temperature ceramics (UHTCs) are indispensable thermal-structural materials. However, their performance under dynamic stress threats encountered in aerospace applications, ranging from macro-impact to supersonic particle erosion, remains poorly understood. Multi-scale impact tests (low-velocity drop-hammer: 3.1–4.4 m/s; medium-velocity particle erosion: 20–40 m/s; supersonic particle erosion: 383 m/s) demonstrated a significant decline in the protective efficacy (normalized damage difference, β) with increasing velocity and decreasing scale. Finite element analysis (FEA), together with micro-CT and TEM characterization, revealed the underlying mechanism: while the modification enhances compressive energy absorption and local hardness, this advantage is progressively counteracted at higher velocities and smaller scales by the amplified brittleness of the ceramics and the detrimental role of compliant carbon-rich regions. These findings establish a velocity/scale performance boundary for current UHTC modifications and provide critical guidelines for designing next-generation C/C composites resistant to multi-mode dynamic threats.