Embedded piezoelectric transducers for structural health monitoring

This paper presents theoretical and experimental results of embedding a piezo-platelet interdigital transducer (IDT) into a 3.4 mm thick plate of Ciba-Geigy Hard-set (CY1301/HY1300) epoxy resin. The piezo-platelet IDT comprises an ensemble of piezoceramic platelets embedded in an epoxy matrix. A combination of linear systems and finite element modeling has been employed to predict the theoretical surface displacement response at the plate surfaces. For a transducer positioned exactly at the centre of a plate, the surface displacement profile on both plate surfaces is symmetric. However, when the transducer position deviates from the centre, symmetric and asymmetric Lamb modes will simultaneously be generated in the plate. In addition, it is shown that off-resonance operation is essential for symmetric mode generation. Finally, an IDT is embedded in a carbon-fibre reinforced composite plate and generation of ultrasonic Lamb waves is demonstrated.