A USER DEFINED MATERIAL MODEL FOR SIMULATION OF VARIABLE MIXED MODE DELAMINATION IN AN EXPLICIT FEM CODE

Abstract

Delamination, a common failure mechanism for composite materials, more than often grows in a variable mode ratio, especially in impact problem. The majority of numerical models present in literature and cohesive elements available in commercial FEM packages don’t account for the correct dissipation of energy when crack propagation takes place in a variable mixed mode ratio, and permit the restoration of the cohesive state which violates the principles of thermodynamics. Thus a material model, developed for an explicit FEM code, is implemented using ABAQUS subroutine VUMAT. The implemented material model is then validated against numerous published result and applied in a number of experimental and aerospace test coupons. The implemented shows excellent coherence with published results and is ideally suited for dealing with problems involving variable mixed mode delamination.