A study of frictional contact effects on modal dissipation characteristics in a debonded structure

Interlaminar debonding modifies the dynamic behavior of laminated structures by altering stiffness, modal characteristics, and associated dissipation mechanisms. Among these, interfacial friction plays an important but still insufficiently understood role in modal damping variations, particularly in nonlinear regimes. This study examines the nonlinear dynamic response of a beam with interlaminar debonding, with particular emphasis on friction-induced modal damping and the contribution of superharmonic components. A time–frequency framework is employed to characterize frictional dissipation through reconstructed hysteresis loops, and a pseudo-modal damping index is defined based on the modal strain energy. Finite element simulations incorporating contact and Coulomb friction are used to investigate the effects of friction level, debonding pattern, size, and position. The results show that frictional contact introduces clear nonlinear features that substantially modify the modal dissipation pattern. In addition, dissipation varies non-monotonically with friction level, indicating the existence of optimal conditions for maximizing hysteretic energy loss. Parametric analyses further reveal that the orientation, location, and size of the debonded region strongly influence friction-induced modal damping and damage-sensitive vibration features. The proposed framework provides a modal-based interpretation of friction-driven damping by accounting for superharmonic contributions and establishes a foundation for the development of vibration-based damage-detection and structural health-monitoring strategies.