Modified electromechanical impedance-based disbond monitoring for honeycomb sandwich composite structure

The increasing use of honeycomb sandwich composites in industries has attracted much interest in its structural health monitoring (SHM) for the localization and quantification of disbond on skin-core interface. The disbond monitoring in sandwich composites is more complicated than that in laminates. In this paper, a comprehensive active monitoring scheme (CAMS) and direct coupling mechanical impedance (DCMI) signatures extraction approach are proposed. It is developed from a modified electromechanical impedance (EMI) analytical model to extract more useful signatures from measured raw signatures (RS). A damage index (DI), root mean square deviation (RMSD), is adopted to locate and quantify the disbond extent inside structures. Experiments are conducted on a honeycomb sandwich composite with a 4 x 4 sensors array mounted on top skin to validate the effectiveness of proposed monitoring scheme. The experimental results show that both disbond location and severity on skin-core interface can be monitored efficaciously.