Abstract
In this paper, a finite element model with a prestressed unit cell is proposed to predict the elastic constants of 3D four-directional braided composites. Firstly, a finite element unit cell model with damage constitutive for 3D four-directional braided composites is established to investigate the influence of the prestresses in the unit cell. Secondly, the elastic constants of 3D four-directional braided composites are predicted with and without the prestresses in the unit cell. Finally, the influences of the braided direction and fibre content on the elastic constants of 3D four-directional braided composites are discussed. The results will provide an important guidance for designing and evaluating the mechanical properties of 3D four-directional braided composites.