Finite element prediction of the impact compressive properties of three-dimensional braided composites using multi-scale model

This paper presents a comprehensive study aimed at the compressive properties of three-dimensional (3D) braided composites subjected to quasi-static and high strain rate loadings using finite element method from fiber/matrix scale to composite scale. It focuses on a computationally efficient multi-scale methodology for prediction of the effective elastic properties and the failure strength of 3D braided composites. First, finite element models with strain rate sensitive elasto-plastic constitutive relationship and ductile and shear failure criterion were established to investigate the mechanical properties and failure mechanism. Second, the failure mechanism in micro-scale fiber/matrix was investigated. The mechanical properties of the interior unit cell, surface unit cell and corner unit cell were predicted and compared, which shows that the surface and corner region of braided preform play an important role during both quasi-static and high strain rate loading. The results obtained from the whole structure heterogeneous composite model and the homogeneous composite model were also analyzed and compared. Finally, the numerical results were verified by the experimental data and the results are encouraging. This method can provide an important guidance for evaluating the mechanical properties and selecting structural parameters for braided composites.