Impedance‐Based Characterization of Oxidation Damage in C f /SiC Ceramic Matrix Composites

Carbon fiber‐reinforced SiC ceramic matrix composites (C f /SiC composites) exhibit distinct oxidation damage characteristics at different temperatures, posing challenges for their nondestructive evaluation. This study combines impedance spectroscopy with microstructural characterization to assess oxidation damage in C f /SiC composites exposed to air at 800 and 1100°C. Microstructural observations showed that oxidation at 800°C predominantly degraded the carbon fibers and fiber/matrix interfaces. By contrast, oxidation at 1100°C promoted the growth of a surface SiO 2 layer, which partially impeded further oxygen ingress. Correlation analysis reveals that the low‐frequency capacitive response in the impedance spectroscopy was strongly associated with fiber/matrix interface oxidation and the resulting mass loss, whereas the high‐frequency capacitive response correlated closely with the thickness of the surface oxide layer. These findings demonstrate that impedance responses in different frequency ranges are selectively sensitive to distinct forms of oxidation damage. This work provides an experimental basis for the nondestructive characterization of oxidation damage in C f /SiC composites using impedance spectroscopy.