A nonlinear finite thickness cohesive interface element for modeling delamination in fibre-reinforced composite laminates

Delamination events are major issues which notably affect the integrity of composite structures. To minimize the experimental efforts, there is an increasing demand for developing reliable numerical tools that can accurately simulate delamination initiation and propagation under mixed-mode loading conditions. The current investigation is concerned with the formulation and the finite element (FE) implementation of a new nonlinear finite thickness cohesive interface model for delamination analysis of fibre-reinforced composite laminates relying on the solid shell concept. The incorporation of geometrically nonlinear effects into the proposed interface formulation is motivated by the recent trend of producing composite structures that can experience large displacements prior to failure, as is the case of postbuckling in stiffened panels. The inelastic material behavior of the interface is modeled using two standard nonlinear decohesion laws: (i) an exponential-based, and (ii) a polynomial-based interface laws. Finally, the performance of the proposed interface element is demonstrated by means of several examples focusing on double cantilever beam (DCB) and rib-stiffened specimens. A excellent level of accuracy is achieved when comparing the numerical predictions and the available experimental data.