Online guided wave-based debonding detection in honeycomb sandwich structures

Because of the complex nature of structural characteristics, damage detection in honeycomb sandwich structures inherently carries many challenges. In the study, effects of debonding on leaky guided wave propagation in honeycomb sandwich structures are first studied by using the finite element method. A surface-bonded piezoelectric wafer actuator/sensor network is used for elastic-guided wave propagation and reception in the composite. Experimental testing is then conducted to verify the numerical simulation and for damage detection. A damage localization image from each actuator-sensor pair is constructed by conducting probability analysis of differential features of transmitted guided waves in the structure with and without debonding. An image of the whole structure is then reconstructed by superimposing the image from each actuator-sensor pair. The quality of the final image is improved by using the image fusion technique. To detect multiple debondings in the honeycomb sandwich structure, a multilevel sensor network strategy is suggested for eliminating pseudoimages due to image coupling of multiple debondings. The final structure image demonstrates that the proposed method can provide quantitative information about location and size of debonding in the honeycomb sandwich structure.