Asymptotic expansion homogenization for simulating progressive damage of 3D braided composites

In order to study tensile strength of 3D braided composites in the microscope view, non-linear progressive damages under tensile loading steps are conducted in this article. Micro-stress is simulated firstly by the method of Asymptotic Expansion Homogenization (AEH) combined with finite-element analysis. A criterion is approached to determine damage and its mode of each element, and stiffness degradation is implemented for the damaged elements with geometric damage theory. Furthermore, the tensile strengths are predicted from calculated stress–strain curves. From simulation, the damage mode for small braiding angle and large braiding angle is different at all. More damage elements are observed in face cell than in body cell. The tensile strength decreases with increase of braiding angle, but the fracture strain has different development. It is verified that 3D braided composites with small braiding angle have better strength but poorer ductility than the composites with large braiding angle.