The present work examines the quasi-static delamination behaviour of CFRP laminated composites under various delamination modes. The simulation is conducted under mode I, mode II, and mixed-mode (I/II) loadings using the different specimen configurations, respectively. For each configuration, the cohesive zone model is used to do finite element modelling of the specimens. The quasi-static behaviour of delamination is simulated using a bilinear cohesive model. A study is conducted on the variable SDEG (scalar stiffness degradation) to assess damage evolution. Additionally, the influence of interfacial strengths on delamination propagation for various modes of loading is also studied. The resulting simulation forecasts are in close agreement with the reported data in the literature. The beginning of process of delamination was slightly delayed at lower interfacial strength values due to the progressive decrease of stiffness before starting of damage following the crack’s expansion.