A subharmonic modulation-based approach for debonding damage detection of composite stiffened plates

As one of the high-strength structures of the aerospace composite panels, the bonding of the stiffened skins affects the mechanical properties of the overall structure. A nonlinear detection method based on subharmonic modulation is proposed in order to detect the debonding damage of composite stiffened structures in the present paper. The debonding damage interface is simplified to a two-degree-of-freedom nonlinear model using interface contact theory. The multi-scale method is employed to analyse the generation mechanism of subharmonic modulation. The experiment is performed on the composite stiffened plate. Then based on the frequency response function characteristics of in-situ piezoelectric actuator/sensor, both high- and low-frequency excitation signals are applied to the composite stiffened plate, and the debonding damage of stiffeners is identified by the subharmonic modulation component in the response signal spectrum. It is shown, both theoretically and experimentally, that the subharmonic modulation method can effectively detect the interfacial debonding damage of composite stiffened structures and is insusceptible to the interference of environmental noise and the inherent nonlinearity of materials.