Linking preform orientation to component distribution and ablation behavior of Cu-modified C/C-ZrC composites

Cu-modified C/C-ZrC composites are promising for thermal protection due to combined passive and active ablation resistance. However, the influence of preform orientation on Cu and ceramic distribution and ablation behavior is unclear, especially for 2.5D needle-punched fiber preform. In this work, Cu-modified C/C-ZrC composites were fabricated via reactive melt infiltration by varying infiltration direction and Cu powder placement using 2.5D needled preforms. Under XY-direction infiltration, Cu showed a fluctuating distribution with obvious local enrichment. This behavior was related to the relatively high through-thickness infiltration resistance. In contrast, Z-direction infiltration favored directional Cu migration. When combined with bottom Cu powder placement, it further produced a relatively stable through-thickness Cu gradient. Under an oxy-acetylene heat flux of 4.2 MW/m², the gradient-structured composite exhibited the lowest surface temperature and the lowest linear and mass ablation rates, while maintaining superior structural stability during both initial and cyclic ablation. Microstructural observations suggest that this improvement is related to a more stable oxide layer, reduced crack propagation, and better interfacial integrity between the oxide scale and substrate. Overall, preform orientation directly governs component distribution and ablation performance in Cu-modified C/C-ZrC composites, with the gradient structure offering enhanced thermal protection for extreme environments.