Numerical and Experimental Study of First Symmetric and Antisymmetric Lamb Wave Modes Generated and Received by Dual-PZTs in a Composite Plate

Structural Health Monitoring is a multidisciplinary field that provides processes whose aim is to monitor damages within structures. Most damage indexes are calculated using Lamb wave signals generated and received by surface-mounted piezoceramic transducers (PZT). The symmetric and antisymmetric Lamb wave modes have different velocities and tend to highlight different kinds of damages. In most SHM applications, a narrowband tone burst with a single frequency component is used as excitation signal. Using two dual PZTs (concentric disc and ring) allows one to tune the emitted signal properly in order to favor antisymmetric or symmetric mode propagation, and to decompose both mode contributions in the received signal. Hence those easy-to-settle devices enable one to detect small damages with appropriate frequencies while guarantying optimal energy efficiency in emission and reception. In this article, a simple model based on the Kirchhoff-Love beam theory is used to estimate the amplitude of the S and A waves generated by a dual PZT mounted on a composite plate. This estimation is confronted to experimental measurements obtained with a laser Doppler vibrometer (for the A mode only). Due to the limited prediction capabilities of the analytical model, a numerical model based on finite element simulations (FEM) in SDTools is introduced. First results indicate good agreement between simulation and measurements. In future studies, the best sensor/actuator combination, the maximum distance between transducers as well as the frequencies to be used for pitch-catch and pulse-echo configurations in a context of delamination detection for SHM application will be determined.