Contact-driven dynamics of delaminated laminates using 3D degenerated shells

A numerical framework is presented for analyzing the dynamic behavior of composite beams and plates containing single or multiple delamination interfaces using the sub-laminate concept. Degenerated 3D shell elements are combined with Lagrange multiplier contact constraints to represent independent sub-laminates and prevent interpenetration across damaged interfaces. Validation is carried out through comparisons with published experiments and Abaqus simulations. The dynamic response is examined in two stages. First, free vibration is studied using free mode analysis (FMA), where interfaces remain unconstrained, and constrained mode analysis (CMA), where non-penetration is enforced during the eigenvalue solution. Second, transient behavior is investigated through FMA and dynamic contact analysis (DCA), in which contact is activated adaptively at nodes that violate the gap condition during time stepping. Comparisons between FMA, CMA, and DCA quantify the influence of delamination size, location, interface depth, boundary proximity and excitation frequency on modal characteristics and breathing response. The results show frequency shifts, mode-shape modification, and transient displacement patterns and confirm that contact effects intensify for larger delaminations, higher excitation frequencies and interfaces close to supports or surface layers. The framework provides a consistent approach for modelling breathing-induced nonlinearity and predicting both modal and transient responses in delaminated composite laminates.