An efficient approach for modeling interlaminar damage in composite laminates with explicit finite element codes

A computationally efficient technique for the analysis of delamination in composite structures with the explicit finite element method is proposed. In the approach, the in-plane and the out-of-plane stiffness of a composite laminate are represented by different material phases. The laminate is seen as a stack of sub-laminates modeled by 2D elements that carry the in-plane stress components. These sub-laminates are connected together with three-dimensional elements that carry the out-of-plane stress components and account for the transverse shear stiffness. Cohesive zone models are adapted to represent the interlaminar damage within the connection elements. The principal advantage of this hybrid modeling technique is that interlaminar damage can be modeled without introducing zero-thickness cohesive elements, which are characterized by means of very large penalty stiffnesses. Consequently, the material stiffness is specified according to physical considerations and, therefore, stable time steps in explicit analyses are not affected by non-physical stiffnesses. The theoretical aspects of the modeling technique and the assessment of a laminate's model are introduced. Then, three different test cases are considered to confirm that the correct kinematic response is achieved and to demonstrate that sequences of complex delamination events can be predicted accurately and efficiently.