A study of the damage progression from notches in an oxide/oxide ceramic–matrix composite using ultrasonic C-scans

The damage progression from notches during quasi-monotonic loading was investigated in an oxide/oxide ceramic–matrix composite using ultrasonic C-scans. Test specimens were monotonically loaded, removed from the test machine, then ultrasonically C-scanned using a through transmission, reflector plate method. The level of ultrasonic attenuation was monitored as a function of applied stress and correlated with the damage observed within the composite. Results of the study showed that the ultrasonic technique successfully monitored the progressive matrix cracking prior to the peak load in specimens tested at 23 °C. Close to the peak load, fiber breakage occurred near the notch tip, which was not indicated by the ultrasonic C-scans. At 950 °C, damage progressed from the notch as a single dominant crack. The extent of enhanced ultrasonic attenuation in the C-scans correlated well with the crack length from the notch.