Modal Acoustic Emission of Damage Accummulation in Woven SiC/SiC at Elevated Temperatures

Traditional [2] acoustic emission (AE) has been used to monitor the damage which occurs under tensile loading for ceramic composites tested at room temperature [3–9]. These studies have shown that AE is very effective at determining the onset of damage and to some extent the amount and type of damage (matrix cracking, fiber breaks, etc.ï). However, due to the modal nature of actual acoustic emission waveforms in thin plates [10–11], the ability to determine the precise location of the sources of the AE signals is very suspect. The dispersive differences in the extensional (symmetric) and flexural (antisymmetric) modes of the waveform as well as the change in the speed of sound due to the reduction in modulus of the composite as damage occurs account for the difficulty in precise source location