Detection and Damage Monitoring in Composite Structures Using Piezoelectrics

Piezoelectric-fiber-composite Transducers (PFCT) are an ideal choice for composite structures application, as they are highly flexible, easily embeddable, and have high compatibility with composite structures; and they provide manufacturing flexibility. The major objective of this research is to use PFCTs as an embedded sensor within the composite structures. As embedded sensors PFCTs are able to perform important functions, such as: (i) monitor the stress/strain levels inside the structures continuously and (ii) detect the damages inside the composite structures. Initially, tensile tests are carried out to investigate the effect of the embedded PFCT sensor on the tensile strength of an impregnated glass fiber-epoxy prepreg composite laminate. It is found that by embedding a PFCT sensor inside the composite structure reduces the ultimate strength and modulus of the overall structure about 2.5% and 7.5% respectively. Then tests are performed to investigate the ability of the embedded PFCT sensor to detect the changes in the applied stress/strain. It was found that these sensors are effectively able to detect the changes in the applied stress/strain. A linear relationship has been observed between the applied input mechanical stress and the sensor generated voltage output. Finally, experiments are performed using the embedded PFCT sensors to detect the damages inside the composite structure using the modal analysis and impact methods. From the results of these experiments, it is concluded that embedded PFCT sensors are able to detect the damages using the above methods effectively.