Electromechanical fatigue behavior of graphite/epoxy laminate embedded with piezoelectric actuator

Fatigue behavior of graphite/epoxy laminate, having [0/±45/90]S lay-up and embedded with piezoelectric (lead zirconate-titanate, PZT) actuator, was investigated under combined mechanical and electrical cycling loading condition, and in only mechanical fatigue condition. The PZT was inserted into a cutout area in the two middle 90° plies. Experiments involved cycling of specimens at different maximum stress levels along with the excitation of the embedded actuator from -10 V to -100 V or 10 V to 100 V, which resulted in either in-phase or out-of-phase electrically induced strain relative to the applied mechanical loading or strain. In general, embedded PZT performed better in the out-of-phase than in the in-phase electromechanical fatigue condition. The fatigue life of the embedded PZT was more than one million cycles, for the applied maximum stress level well above its design limit in the out-of phase electromechanical and in only mechanical fatigue conditions. The embedded PZT failed before one million cycles during the in-phase test at the applied maximum stress equal to its design limit. Above this stress level, a sharp reduction in the fatigue life occurred during the in-phase electromechanical cycling condition.