Ultra-high-temperature stress-oxidation mechanisms and residual strength of C/SiC composites

Carbon fiber-reinforced silicon carbide (C/SiC) composites are highly promising candidates for structural components operating under coupled thermo-mechanical-chemical conditions. However, current understandings of their oxidation mechanisms are predominantly restricted to static environments and temperatures below 2000 °C. To address this gap, this study systematically investigates the stress-oxidation behavior of C/SiC composites across an unprecedented temperature range of 800 °C to 2500 °C in an atmospheric environment. The evolutionary oxidation mechanisms were characterized using X-ray computed tomography (CT) and scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Based on these observations, the evolution patterns of macroscopic oxidation damage under varying temperatures and applied stresses were quantitatively evaluated. Notably, the critical role of oxidation products generated during 1400 °C stress-oxidation in governing both the subsequent oxidation behavior and the macroscopic residual strength was elucidated. These findings provide profound insights into the ultra-high-temperature oxidation mechanisms and antioxidant strategies for C/SiC composites, offering a solid theoretical basis for the optimization of advanced thermal protection systems.