Assessment of degraded stiffness matrices for composite laminates under low-velocity impact based on modified characteristic length model

Abstract

This study aims to evaluate the applicability of the degraded stiffness matrix and the redefined characteristic length models in the finite element analysis of composite laminates under low-velocity impact. Implemented by the user-defined VUMAT subroutine in ABAQUS, various damage models are used to predict the damage behavior in the composite laminates, meanwhile, the user-defined VUCHARLENGTH subroutine is applied to define the characteristic length to match the damage mode. Cohesive elements are inserted between the adjacent piles to model the delamination. The applicability of different damage models is investigated by comparing the global mechanical response and local damage behavior. A new characteristic length calculation method is proposed to apply in the low-velocity impact simulation for laminates. The numerical results show that the degraded stiffness matrix proposed by both Maimi and Matzenmiller can accurately predict the global mechanical responses in the complicated damage accumulation case, while the model of PEE (the principle of energy equivalence) and Linde aren’t suitable for the low-velocity impact simulation. As for the characteristic length model, the redefined characteristic length model can obtain more accurate global mechanical responses with the impact energy increasing compared with the predictions of default characteristic length model.