Debonding localisation in connected panels using nonlinear pseudo-forces reconstructed across fundamental to higher harmonics

Given the critical importance of structural integrity and safety, there is a significant demand for localising local debondings in connected panels. Non-contact laser scanning enables high-spatial-resolution structural operating deflection shapes (ODSs), allowing for precise localisation of debonding edges. Linear pseudo-forces (LPFs) and nonlinear pseudo-forces (NPFs) have been recently proposed for structural damage localisation, which are reconstructed using linear ODSs at linear harmonics and nonlinear ODSs at neighbouring sideband harmonics, respectively. This study focuses on reconstructing the NPFs using ODSs across fundamental to higher harmonics, with the goal of localising debondings in connected panels. Such NPFs can extract both linear and nonlinear damage features from the corresponding linear and nonlinear ODSs, respectively. Therefore, this study offers a more comprehensive approach for characterising debonding spatial configurations. The capability of the NPF approach is demonstrated through simulations and experiments of laminated panels with ‘breathing’ debondings using the finite element method and laser scanning measurement, respectively. Additionally, the approach is experimentally validated for its applicability to bolted panels with debondings caused by local bolt looseness. The findings demonstrate that the debonding spatial configurations can be comprehensively characterised.