Finite element analysis of 3D braided composites based on three unit-cells models

3D braided composites have a skin-core structure and can be divided into three regions: interior, surface and corner. Each region is built up of identical unit-cells but the yarn configuration in the three regions is different thus must be treated separately. In this paper, three distinct solid structure models of unit-cell located in the interior, surface and corner regions of 3D braided composites are established first. With appropriate boundary conditions, the mechanical responses of 3D braided composites are simulated by using the finite element method. The deformation and stress distribution of the three unit-cell models are presented and the effects of the braiding angle and fiber volume fraction on the elastic constants of 3D braided composites are investigated in detail. Numerical results show that the three unit-cells have distinctive properties and the surface and corner unit cells are stiffer than the interior unit cell. Therefore, the effect of surface and corner regions on the mechanical properties of 3D braided composites must be considered in order to obtain accurate results. The calculated results show good agreement with available experiment data, thus verifies the applicability of the proposed three unit-cells models.