A novel finite element method for predicting the tensile properties of 3D braided composites

A novel unit-cell model which considers the structure interference of braiding yarns in the external region is proposed to describe the geometric structure of 3D braided composites. Based on the multi-scale homogenization theory, mesoscopic structure finite element analysis model is established to predict the stiffness matrix of unit-cells. Periodic boundary conditions are applied on the periodic surfaces of unit-cells to reflect the repeating feature. And the node deformation matching equations are applied on the internal connected faces of the surface unit-cell and the corner-cell, so that the displacement continuity conditions and traction continuity conditions are satisfied. In allusion to 3D braided composites with small braiding angle, principal tensile strength forecasting model is developed.