Subharmonic ultrasonic resonance method for damage recognition of imperfect adhesive interfaces

During the production and application of bonding structures, non-uniform adhesive coatings and deterioration of adhesive materials often lead to weak bonding damage at crucial interfaces, significantly impacting structural robustness. In this paper, a novel subharmonic ultrasonic resonance method is developed for damage identification in the interfacial weak bonding. Based on a nonlinear spring model of imperfect adhesive interfaces, the multi-scale method is used to explain the mechanism and the conditions for the generation of the subharmonic resonance. The ultrasonic resonance is employed to enhance the nonlinear response of imperfect adhesive interfaces efficiently, as nonlinear characteristics are not readily apparent in cases of the interfacial weak bonding damage. By analyzing the subharmonic ultrasonic resonance phenomenon in the spectrum, the interfacial weak bonding damage identification experiment for a carbon fiber reinforced plastic-aluminum plate bonding structure is carried out. The results demonstrate that ultrasonic resonance can lower the threshold for generating subharmonic resonance and the subharmonic ultrasonic resonance method significantly amplifies the nonlinear response at the damaged area, improving detection capabilities amidst noise interference. Moreover, the efficacy of the subharmonic ultrasonic resonance method in detecting and locating weak bonding damage is confirmed.