Microstructure and finite element analysis of 3D five-directional braided composites

Microstructure of 3D five-directional braided composites determines its mechanical properties. Microscopic evidence of the microstructure reveals that the cross-sections of the axial yarn are variable along its central axial due to the lateral compression from the adjacent braiding yarns. On the basis of microscopic observations, a dense but non-intersecting geometry internal unit cell model of 3D five-directional braided composites is established. By using the unti-cell model, a 3D mesomechanical FEA is proposed to predict the effective elastic properties of 3D five-directional braided composites. Compared with existing model, present model is more effective to calculate the mechanical properties of 3D five-directional braided composites with more than 50% fiber volume fraction.