Finite element modelling of damage progression in non-crimp fabric reinforced composites

Progressive failure of non-crimp fabric composite laminate was studied using finite element analysis with stress-based failure criteria. The laminate was loaded in tension and has the lay-up of [0/90]s with both in-phase and out-of-phase placed transverse-tow layers considered. The finite element model was created from a cross-section Representative Volume Element of the laminate. Damage analysis was first carried out using the Maximum Stress failure criterion. After damage was detected within the laminate, point-wise selective stiffness degradation was applied to the model through a user-defined material subroutine. For the material under study, it has been shown that damage initially occurs in either the transverse tows or the resin pockets, and gradually spreads across the transverse tows and resin pockets. As the load reaches a critical point, damage finally progresses into the longitudinal tows and causes laminate failure very quickly. Stages of damage evolution, from initiation until final failure, are reflected in the knee behaviour of the overall load–strain trace. Studies show that tow shape plays a role in the failure progress, especially the load levels for initial and final failure. Analyses using different combinations of failure criteria for the tows and resin pockets were performed and the results were addressed in terms of the location of initial damage and the load levels of initial damage and final failure.