Ultrasonic evaluation of interfacial damage in adhesively bonded structure using quasi-static component of Lamb waves

To evaluate the interfacial debonding damage, this research explores the generation and propagation of Lamb wave-induced quasi-static component (QSC) in the adhesively bonded composite structures based on finite element (FE) simulation and experimental testing. Compared with the second harmonic generation (SHG) of Lamb waves, the QSC method does not require strict phase velocity matching, but only approximate group velocity matching. This characteristic substantially broadens the selectable range of fundamental Lamb wave modes, thereby enhancing the practical applicability of the QSC-based ultrasonic evaluation method. To evaluate the initiation and extension of debonding damage, a micro-crack is introduced in FE simulations. The simulation results demonstrate that QSC has higher sensitivity to the variation of crack length compared with SHG method, and the experimental investigations show a positive correlation between the acoustic nonlinearity parameter (ANP) and the increase in interfacial debonding area. The consistency between FE simulation and experimental data conclusively demonstrates that the QSC method provides a reliable and accurate nondestructive evaluation technique for characterizing interfacial debonding in the adhesively bonded composite structures.