Delamination is a phenomenon of degradation of composite laminates that may lead structures to failure or that may reduce their stiffness and strength. Finite element analysis using the Cohesive Zone Method (CZM) is a widely used method for analyzing delamination in laminated composites. The aim of this thesis is to examine the effect of DCB geometry and mesh size on the delamination length of the cohesive material and to present the numerical model closest to the our experimental result. In order to eliminate the convergence problem of the mesh size, which is the main factor for the estimation of the process length, we prefer explicit analysis instead of implicit analysis.