Contactless characterization of the adhesion of thermoplastic welded composite assemblies with Lamb waves based inverse method

Interest in detecting defects and evaluating the mechanical strength of assemblies using non-destructive methods has grown considerably during the last years. In this context, the present work describes a characterization method based on the propagation of Lamb waves to quantify the adhesion of ThermoPlastic (TP) welded composite assemblies. The propagating ultrasonic guided waves within the multilayered anisotropic composites are excited and detected with the help of Air-Coupled ultrasonic Transducers (ACT). Then, an adapted analytical model is used to investigate the influence of the mechanical properties corresponding to the welding layer. Theoretical and experimental data are compared by considering the wavenumber dispersion curves, where guided modes are considered over different frequency domains. Finally, the welding layer stiffness properties are estimated using an optimization method on various welded samples of different qualities.