427 AE Characterization of Bending Fracture Behavior of 3D-SiC/SiC Composites

The fracture behavior of the SiC/SiC composites was examined by 4-point bending tests. The AE signals detected during the tests were processed by AE wavelet analysis, which extracted the first and second major frequencies from continuous wavelet transform (CWT) diagram. Consequently, the two-frequency combination analysis can detect local frequency components and characterize a wavelet diagram well. A history of these major frequencies was correlated to initiation and propagation of microdameges, such as cracks in SiC matrix, crack propagation along thickness and fiber buckling. Although other microdamages, such as fiber breaks and pull-out of fiber, have not been correlated to the AE signals, the results suggest that the two-frequency combination analysis based on CWT, i.e. Projected Wavelet Transformation (PWT) analysis, has great potential to characterize the micro-damages of the composites.