A shell/3D modeling technique for the analysis of delaminated composite laminates

A shell/3D modeling technique was developed for which a local three-dimensi onal solid finite element model is used only in the immediate vicinity of t he delamination front. The goal was to combine the accuracy of the full thr ee-dimensional solution with the computational efficiency of a plate or she ll finite element model. Multi-point constraints provided a kinematically c ompatible interface between the local three-dimensional model and the globa l structural model which has been meshed with plate or shell finite element s. Double cantilever beam (DCB), end notched flexure (ENF), and single leg bending (SLB) specimens were modeled using the shell/3D technique to study the feasibility for pure mode I (DCB), mode II (ENF) and mixed mode I/II (S LB) cases. Mixed mode strain energy release rate distributions were compute d across the width of the specimens using the virtual crack closure techniq ue. Specimens with a unidirectional layup and with a multidirectional layup where the delamination is located between two non-zero degree plies were s imulated. For a local three-dimensional model, extending to a minimum of ab out three specimen thicknesses on either side of the delamination front, th e results were in good agreement with mixed mode strain energy release rate s obtained from computations where the entire specimen had been modeled wit h solid elements. For large built-up composite structures modeled with plat e elements, the shell/SD modeling technique offers a great potential for re ducing the model size, since only a relatively small section in the vicinit y of the delamination front needs to be modeled with solid elements. Publis hed by Elsevier Science Ltd.