Characterization of Bending Fracture of Stress Biased Piezoelectric Composite Actuators by Acoustic Emission

In this work, the bending fracture process of a stress biased piezoelectric composite actuator (PCA) under a three-point bending load have been characterized with the aid of acoustic emission (AE) monitoring. The AE signal from the monolithic PZT wafer at the maximum bending load shows the characteristics of high amplitude and long duration with a low dominant frequency band confirmed by a fast Fourier transform. For PCAs, the AE signals emitted in stage II have amplitude higher than 80 dB and a low dominant frequency band characteristic. Such signals are due to the brittle fracturing in the PZT layer and/or the growth of delamination between the PZT and the fiber composite layers. The signals with high amplitude and a high dominant frequency band in stage III generate by the fiber breakages hindering the main crack propagation in the glass bottom layer along with the macro-delamination between the PZT layer and the fiber composite layer. Based on the AE analysis and fracture observations, the bending fracture process of stress-biased PCAs has been reasonably characterized.