A new cohesive model for simulating delamination propagation in composite laminates under transverse loads

In this paper, we propose a new cohesive model to stably and accurately simulate the delamination propagations in composite laminates under quasi-static and low-velocity impact transverse loads using comparatively coarse meshes. In this model, a pre-softening zone ahead of the existing traditional softening zone is proposed. In this pre-softening zone, the initial stiffnesses and the interface strengths at the integration points of cohesive elements are gradually reduced as the corresponding effective relative displacements at these points increase. However, the onset displacement corresponding to the onset damage is not changed in this model. Moreover, the fracture toughness of materials for determining the final displacement of complete decohesion is kept constant. This cohesive model is implemented in the explicit time integration scheme combined with a powerful three-dimensional (3D) hybrid finite element for evaluating the delamination propagations on interfaces in composite laminates. A DCB problem is employed to analyze the characteristics of the present cohesive model. In order to reduce the computational cost for dealing with more complex problems, a stress-based criterion is also adopted in our numerical model for evaluating various in-plane damages, such as matrix cracks, fiber breakage, etc, Finally, two experimental examples are employed to illustrate the validity of the present approach. (C) 2008 Elsevier Ltd. All rights reserved.