Damage Size Quantification Using Lamb Waves by Analytical Model Identification

Composite materials are subject to internal damages that can threaten structural integrity while being invisible to the naked eye. StructuralHealth Monitoring (SHM) allows to ensure in real-time that aircraft substructures can still perform their function. Among all the technologies used in SHM, the emission/reception of Lamb waves are very popular. Algorithms using Lamb waves for damage detection and localization already exist in the literature but damage size estimation is still an open problem. In this paper, we propose an approach to quantify delamination damage size by relying on an analytical scattering model. The structure considered is a plate equipped with piezoelectric transducers (PZT) acting both as actuators and sensors. We use the framework of the Mindlin-Kane plate theory to describe S0-mode Lamb wave propagation. The damage considered is a cylindrical inhomogeneity where the mechanical properties are different from the rest of the plate. The analytical model takes into account the signal emission by a PZT, the scattering by the damage, and the reception by a sensor PZT. This model is then used in an identification process to estimate the size of the damage by minimizing a dedicated cost function. The proposed approach is applied on aluminum plate simulation data.