Analysis of Acoustic Emission energy release during static fatigue tests at intermediate temperatures on Ceramic Matrix Composites: Towards rupture time prediction

Ceramic Matrix Composites (CMCs) such as woven SiCf/[Si–B–C] are used in aeronautical engines. Expected lifetimes in service conditions are tens of thousands of hours and therefore unattainable in laboratory tests. This paper shows the potential of Acoustic Emission (AE) based approach to lifetime prediction of CMCs. The energy of AE events is used as a measure of stress-induced damage during static fatigue at intermediate temperatures. The energy released by sources was determined from the signal energy received by two sensors, the effects of attenuation due to propagation distance were eliminated. A method for real-time analysis of energy release has been developed. It allows the identification of a characteristic time at 55% of the measured rupture time. This characteristic time reflects a local critical behavior described by the Benioff law and it indicates a second damage phase when subcritical crack growth in fibers is predominant.