The aim of this study is to investigate fully reversed electric fatigue behavior of a piezoelectric composite actuator (PCA). For that purpose, fatigue tests with different loading conditions have been conducted and the performance degradation has been monitored. During a preset number of loading cycles, non-destructive acoustic emission (AE) tests were used for monitoring the damage evolution in real time. The displacement-cycle curves were obtained in fully reversed cyclic bending loading. The microstructures and fracture surfaces of PCA were examined to reveal their fatigue damage mechanism. The results indicated that the AE technique was applicable to fatigue damage assessment in the piezoelectric composite actuator. It was shown that the initial damage mechanism of PCAs under fully reversed electric cyclic loading originated from the transgranular fracture in the PZT ceramic layer; with increasing cycles, local intergranular cracking initiated and the either developed onto the surface of the PZT ceramic layer or propagated into the internal layer, which were some different depending on the drive frequencies and the lay-up sequence of the PCA.

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