Multimode guided wave extraction capabilities using embedded thin film sensors in a composite laminated beam

Abstract A novel method to extract individual wave modes from the ultrasonic multimode guided wave response sensed by embedded piezoelectric sensors is presented. Multimode response involving two fundamental modes, i.e., flexural and axial, and two higher-order wave-modes, i.e., shear and thickness contraction have been considered in the present work. The model is based on higher order beam theory which uses wave kinematics to extract individual wave modes from the multimode response. Further, a numerical finite element model is employed to validate the deformation profile of this analytical model. The embedment of thin film sensors at the same location but within different layers produce signals that exhibit a relative difference in the phase and amplitude due to kinematics. The sensor signals are then post-processed to obtain individual Lamb wave modes. Experiments are carried out to validate the procedure for extracting individual guided wave mode response. The method is independent of sampling rate and works in the presence of complicated mode converted responses. Electronic analog circuits can also be used to perform operations on sensor signals before analog-to-digital conversion, thereby eliminating digital signal processing and the requirement of onboard computers for structural health monitoring especially in aircraft. Such capability minimizes power consumption and weight since we may be able to avoid the use of a computer.