Modification of Longitudinal Modulus of 3D Full Five Directional Braided Composite Materials Base on Energy Theory

The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.