Numerical analysis of unidirectional carbon-fibre/epoxy composite laminates under low velocity impacts of different forms

Based on the stress initial damage criterion and the improved sudden reduction model of material stiffness, a user-defined subroutine (VUMAT) was written for the constitutive equation of unidirectional carbon-fibre/epoxy layers and combined with the VUMAT of the exponential cohesive zone model for interfacial layers, the VUMAT of laminates was implemented in ABAQUS/Explicit to investigate the dynamic mechanical properties of unidirectional carbon-fibre/epoxy composite laminates under low velocity impacts of different forms. First, the finite element method was conducted on the composite laminates with a stacking sequence of [45/0/-45/90]2S on a single impact to verify the correctness of VUMAT. Additionally, the impact response of the composite laminates was simulated with a [0/90/0/90]2S layup, and the mechanical behavior of the two laminates was analyzed. Moreover, the study also focused on the multiple low velocity impacts at different impact angles between the impactor and composite laminates with the two stacking sequences. The results illustrate that the numerical results correlate well with experimental results in the literature; when the initial impact energy is at the same level, composite laminates with the [0/90/0/90]2S layup have higher energy absorption than laminates with the stacking sequence of [45/0/-45/90]2S and the energy absorption of laminates under multiple impacts is higher than under a single impact. In addition, the larger the angle between the impactor and laminates is, the larger the contact force, energy absorption, and delamination area of laminates. The simulation results of this study provide an appropriate reference for the low velocity impact of unidirectional carbon-fibre/epoxy composite laminates.