Numerical study of the mixed-mode delamination of generally-shaped composite interfaces

In recent years, several engineering components are made of high performance laminated composites and adhesively bonded interfaces. These laminated structures are known to suffer the non-linear and irreversible delamination process, including the formation and propagation of inter-laminar cracks, up to the complete detachment of the adhering parts. In this context, we develop a new numerical formulation based on the generalized differential quadrature (GDQ) approach to determine the delamination onset and propagation along weak interfaces of arbitrary shape, made of composite materials and subjected to mixed-mode conditions. The interfacial problem is addressed by concentrating all non-linearities at the interface. This means that interfaces are considered as an assemblage of two sublaminates, partly bonded together by an elastic interface, here modelled as a continuous distribution of elastic springs acting along the normal and/or tangential direction, depending on the selected mixed-mode condition. A large parametric study is here performed to predict the local and global response in terms of interfacial stresses, internal forces and displacements, as well as in terms of compliance, energy release rate, mode mixity angle, and load-deflection curves. The feasibility of the proposed formulation is also verified through a convergence analysis, for the simplest case of straight composite adherends. The available literature and the analytical predictions based on the enhanced beam approach is here handled for comparative purposes. The excellent agreement between the proposed numerical approach and the analytical one, confirms the feasibility and accuracy of the proposed formulation when studying the delamination phenomena occurring within composite materials or laminated joints of general shapes.