Ultrasonic Lamb wave-based debonding monitoring of advanced honeycomb sandwich composite structures

Honeycomb sandwich composites are extensively used in military shelters, aerospace structures, ground transportation structures, auto-racing bodies, ship panels, and other special purpose structures requiring lightweight construction materials. But debondings at the face-sheet-to-core junctions frequently occur due to the variable operating and loading conditions, which may menace the safety and overall integrity of the structural assembly. This paper aims to effectively identify such hidden debonding regions in these advanced structures, using Lamb wave-based monitoring technique. A semianalytical analysis of Lamb wave dispersion in a healthy sandwich structure is carried out to identify various Lamb modes and to study their propagation phenomenon. A combined finite element-based simulation and experimental analysis of Lamb wave propagation in sandwich panels (healthy and with debonding) are then carried out using piezoelectric transducer networks. It is observed that the presence of debonding significantly reduces the propagating Lamb wave mode amplitudes. A debonding detection algorithm, which uses the differential changes in Lamb mode amplitudes, is applied to efficiently identify single and multiple debonding regions in the structure.