Mechanical properties of 3D 4-directional braided composites with a central circular hole under tension

3D braided composites are suitable for components that are prone to stress concentration owing to their low delaminating tendency and high damage tolerance. However, there are few researches that have investigated the mechanical properties of the braided composites with holes in multi-scale. In this article, an analysis method is proposed for the mechanical properties of 3D 4-directional braided composites with a central circular hole. The macro equivalent stiffness of the composites is calculated by homogenization method. Based on the modified Lekhnitskii theory, the transverse and tangential stresses at the hole edge of braided composite plates are attained. The models of meso unit cells with different braided angles are established, and the strength of the composites is predicted by Tsai-Wu criterion. The point stress criterion, the average stress criterion, and the progressive damage analysis method on the basis of different failure criteria are adopted to study the tensile strength of the braided composite plates with a hole, respectively. The study of mechanical properties of 3D 4-directional braided composites with a circular hole under tension in the article provides theoretical and simulation methods for such problems in engineering.