Inverse Determination Of Interfacial Properties of a Bonded Structure Using Lamb Waves Generated By Laser Lateral Excitation

Abstract

Nondestructive testing of the adhesive bond properties of a bonded structure is essential in aviation, automotive, and other industries. In this study, a Lamb wave–based quantitative characterization method is proposed to determine the interfacial stiffness of bonded structures. A theoretical model is established, with which the dispersion relationship of Lamb waves in a bonded structure is investigated. Different interfacial states ranging from a perfect bond to a weak bond are simulated, and the numerical results show the sensitivity of Lamb waves to interfacial stiffness. A lateral excitation method is proposed to enhance the excitation of the interfacial sensitive Lamb wave modes, and laser ultrasonic experiments show the enhancement of the Lamb wave signals on aluminum-epoxy-aluminum samples generated by the lateral excitation method. Then, a rapid construction method of inversion objective function is presented to reconstruct the interfacial stiffness coefficient of a bonded structure, and its functionality is validated via finite element simulations. Finally, the interfacial properties of the samples are reconstructed using the inversion scheme.