Health Monitoring of Sandwich Plates Based on the Analysis of the Interaction of Lamb Waves with Damages

摘要

Sandwich structures we are interested in (glass fibers skins and foam core) are very sensitive to low velocity impacts. These impacts induce debonding between the skins and the core and a crush of the foam, which are not visible from the outside. We propose a health monitoring system to localize these damages and estimate their size. This system is based on thin piezoelectric discs bonded on the skins and used as transducers, making it possible to generate and detect Lamb waves propagating in the sandwich. Experiments show that it is possible to choose waves having interaction with the particular damages of this sandwich. From the comparison of the waves for a non-damaged and a damaged plate, it seems possible to identify the damage. In order to analyze the interaction of Lamb waves with the defect, and define and optimize identification procedures for these defects, we have done f.e.m. computations which make it possible to obtain theoretical background to the analysis of the experimental data and propose an identification procedure of defects. When applied to numerically simulated experimental data, the identification procedure for defects give quite good results