Parameterized meso-scale modeling and experimental study on the tensile damage evolution and strength of 3D five-directional braided composites

A parametric finite element model (FEM) of three-dimensional five-directional (3D5d) braided composites was established considering the yarn space contact relationship. By adopting reasonable damage criteria and boundary conditions, the damage behavior and mechanical properties of FEM under tensile loading were investigated. The finite element prediction results are consistent with the experiments, indicating that the FEM can effectively predict the progressive damage and strength of 3D5d braided composites. Damage evolution shows that the main failure modes with small braiding angles include tensile failure of braiding yarn and axial yarn, while the large braiding angles are tensile shear failure of braiding yarn. As the fiber volume fraction increases, the initial damage location of the FEM changes from the intersection of braiding yarn/axial yarn to the junction among the braiding yarns. The stress-strain curves results show that the 3D5d braided composites exhibit brittle fracture characteristics under longitudinal tensile loading, and the mechanical properties are significantly correlated with the braiding angle and fiber volume fraction. In addition, the tensile properties of 3D5d braided composites are also compared with those of three-dimensional four-directional (3D4d) braided composites.