Debonding localization in connected panels using nonlinear pseudo-forces across higher to sideband harmonics

Given the critical importance of structural integrity and safety, there is significant demand to localise local debondings in laminated panels. The existing linear pseudo-force (LPF) model treats local damage as virtual forces applied exclusively within the damage regions, enabling localised damage. However, this model fails to account for the nonlinearities arising from the “breathing” behaviour of debondings. To address this limitation, this study extends the concept of LPF into the nonlinear pseudo-force (NPF). Superior to the existing LPF model, the NPF model can extract both linear and nonlinear damage features, providing a more comprehensive approach to localising debondings in laminated panels. The NPFs are reconstructed from nonlinear operating deflection shapes across higher to sideband harmonics. Damage indices (DIs) are established using the NPFs associated with successive higher harmonics or neighbouring sideband harmonics. Peaks arising in the DIs can distinctly characterise the spatial features of debondings. The approach is experimentally verified on a laminated panel with a “breathing” debond using laser-scanning measurements. The results confirm that the NPF approach can effectively characterise the locations and sizes of debondings in laminated panels.