Dynamics and Progression of Micro-fractures in C/C Composite Studied by AE Waveform Simulation

Abstract

Utilizing the waveform simulation method of bulkwave Acoustic Emission (AE) signals, dynamics (kinetics and kinematics) and progression of microfractures in an unidirectional C/C composite were studied. Frequency and orientation dependence of longitudinal (P-) wave velocity and attenuation were measured utilizing a laser ultrasonic system. Fracture dynamics were studied by the P-waveform simulation so that the computed P-wave amplitude and rise time best matches the monitored values. Here, both the response delay and the attenuation were taken into account. Progression of four fracture types, i.e., matrix crack (Type-1), fiber and inter-laminar debonding (Type-2 and -3) and fiber disbonding (Type-4) during four-point bending were revealed. A sudden propagation of large inter-laminar delamination occurred after the succession of small matrix cracks and inter-laminar debondings.