Piezoelectric fiber composite strip transducer design considerations for generating lamb waves

Lamb waves have great promise among the various active monitoring schemes being researched for Structural Health Monitoring. Planar Lamb wave excitation using surface-bonded piezoelectric strips to function as comb transducers is investigated numerically for both the fundamental symmetric S0 and the antisymmetric A0 wave modes. This comb-type transducer is comprised of multiple piezoelectric elements, which are piezoelectric fiber composites sandwiched between electrodes. These transducer strips reduce the wiring requirements, can conform to curved surfaces, and the properties can be tailored to suit the application. Transducer variables are many; here fiber orientation, volume fraction, poling directions, and electrode locations are investigated. Specifically, piezocomposite properties are estimated through micromechanical modeling for input to finite element analysis of Lamb wave generation and propagation. For this multiphysics problem, the finite element analysis employs co-simulation using ABAQUS Standard and ABAQUS Explicit to simulate transient wave propagation from a strip transducer on a plate. In the finite element results, the amplitude of the Lamb wave at a prescribed distance from the transducer is evaluated to characterize the effectiveness of the composite comb transducer. Furthermore, results show that there are a number of cases where composite actuators provide a large amplitude response. After considering piezoelectric fiber direction, poling direction, and electric field direction, it appears that fiber, polarization, and activation electric fields through the thickness of the transducer represent the optimal design.