Disbond detection in adhesively bonded composite structures using vibration signatures

This paper presents a structural health monitoring technique based on analysis of the dynamic signature of the structure, which changes as damage occurs, due to alterations in structural properties such as stiffness and damping. Experiments performed on plate specimens and T-joint specimens which had various degrees of damage in the form of delaminations showed that it is possible to quantify the effect of damage on the acoustic response resulting from a tap in thick GFRP laminates. Subsequent experiments were conducted on adhesively bonded GFRP composite beam specimens with artificial delaminations of various sizes and locations embedded in the bondline. The specimens were excited using piezoelectric actuators bonded to the surface at various locations and the structural and acoustic responses were analysed. The results of these tests and analyses are presented and it is concluded that the structural and acoustic responses of such specimens to a piezoelectric actuator can be used to identify the presence of a delamination and may potentially be used to determine its size and location.