Theoretical prediction on the mechanical properties of 3D braided composites using a helix geometry model

In our previous work, we have established a three-dimensional (3D) finite element model (FEM) which precisely simulated the spatial configuration of the braiding yarns. This paper presents a theoretical model based upon the helix geometry unit cell for prediction of the effective elastic constants and the failure strength of 3D braided composites under uniaxial load through the stiffness volume average method and Tsai-Wu polynomial failure criterion. Comparisons between the theoretical and experimental results are conducted. The theoretical results show that the braid angle has significant influences on the mechanical properties of 3D braided composites.