Integrity of graphite/epoxy laminate embedded with piezoelectric sensor/actuator under monotonic and fatigue loads

This study investigated the integrity of the host graphite/epoxy laminate as well as of the embedded active PZT sensor/actuator under monotonic and fatigue loads. For this, graphite/epoxy (AS4/3501-6) laminates were fabricated where the commercially available piezoelectric device in the pre-pack-aged form was embedded. Two lay-ups were tested: [0/+/-45/90]s or [0/0/+/-45/0/0/90]s. The piezoelectric actuator/sensor was embedded in two ways: one method involved placing them into a cut-out area in the two middle 90degrees plies, and the second one involved insertion between the two middle 90degrees plies without any cut-out. Ultimate tensile strength and Young's modulus of the tested laminates were not affected due to insertion of the piezoelectric actuator/sensor using either of the embedding techniques. There was also no degradation in the fatigue strength/lives of the tested laminates due to insertion of the piezoelectric actuator/sensor. Furthermore, these were not affected by the embedding method (i.e. cut-out versus simple insertion method). Also, the integrity of the embedded piezoelectric actuator/sensor was preserved when mechanically fatigued or loaded monotonically to the maximum stress level equal to its operational design limit.