Abstract: To model the delamination initiation and propagation of the composite laminates, the cohesive element is often used. But, unfortunately, the numerical result may depend on element size, and it can′t model the interface failure caused by large compressive stress. Firstly, three models with different thickness of the cohesive element, i.e. the double cantilever beam model, the end-loaded split model and the dynamic impact model, are established to simulate the delamination evolution of the composite. The influences of the cohesive element thickness on the load-displacement curve and interface damage area are studied. Then, the constitutive relation of cohesive element is defined by the subroutine to consider the interface failure caused by compressive stress, and the impact of interface failure caused by compressive stress during impact response of composites is analyzed. The results show that the thickness of cohesive element has a significant influence on the interface damage area. Under conditions of the same loading, the damage area of the interface becomes smaller as the cohesive element thickness becomes larger. With the consideration of the interface layer failure caused by compressive stress, the interface damage area would be larger and the interface modes contains compression failure and shear failure.

Key words: delamination, cohesive element, element thickness, impact, damage area, failure mode