Quasi-static and dynamic analysis of delamination growth using new interfacial decohesion elements

In this paper, a modified adaptive decohesion element is presented. The new elements are developed and implemented in LS-DYNA, as a user defined material subroutine (UMAT), to stabilize the finite element simulations of delamination propagation in composite laminates under transverse loads. In this model, a presoftening zone is proposed ahead of the existing softening zone. In this pre-softening zone, the initial stiffness and the interface strength are gradually decreased. The onset displacement corresponding to the onset damage is not changed in the proposed model. In addition, the critical energy release rate of the materials is kept constant. Moreover, the constitutive equation of the new decohesion model is developed to be depended on the opening velocity of the displacement jump. The traction based model includes a cohesive zone viscosity parameter (η ) to vary the degree of rate dependence and to adjust the maximum traction. The numerical simulation results of DCB in Mode-I is presented to illustrate the validity of the new model. It is shown that the proposed model brings stable simulations, overcome the numerical instability and can be widely used in quasi-static, dynamic and impact problems.