Structural modeling and mechanical characterizing of three-dimensional four-step braided composites: A review

The unique structural features of three-dimensional (3D) braided preforms determine an array of excellent mechanical properties of 3D braided composites, such as high strength and low density, great damage tolerance and fatigue performance. In the present paper, the studies relevant to the structural modeling of 3D braided preforms in recent decades, including fiber inclination model, helix model, three unit cell model, multi-unit cell model, digital element method, etc. have been reviewed and classified into three types, i.e., mechanical equivalence models, unit cell geometrical models and yarn geometrical models. Based on the models, mechanical characterizations of 3D braided composites have been reviewed and discussed.