Electro-mechanical impedance measurements as a possible SHM method for sandwich debonding detection

The present article addresses the evaluation of the electro-mechanical (E/M) impedance method as a Structure Health Monitoring (SHM) method to detect and classify damage, more specific, the debonding of a face layer. In the study the considered structure is simplified as a circular sandwich panel of constant thickness, consisting of isotropic face layers and a honeycomb core. The debonding is assumed to be circular and situated at the center of the panel, only variable in its radius. The article starts with a brief introduction to the basic idea of SHM and the fundamentals of the E/M impedance method. Further, the idealized setting is investigated by two sets of experiments whose results are analyzed by typically used damage metrics and by considering both analytical and numerical models. A coupled-field FEM model is developed and compared to the experimental results. Furthermore, an analytical model is derived to evaluate the experimental and numerical results. All results are presented and discussed extensively on pursuing the objective to detect and classify the size of a debonding. Finally, it is shown how a model based approach can predict the presence but also the size of a debonding in the considered sandwich panels based on the E/M impedance measurements.