Three theoretical microstructural models were constructed based on manufacturing three-dimensional seven-directional (3D7d) braided preforms, and their relationships with braiding angles, fiber volume fractions, and yarn filling factor were investigated. The influences of braiding parameters, loading directions, and braiding structure on the performances of 3D7d braided composites were predicted in combination with a bridging model. The results concluded that the longitudinal modulus and tensile strength decreased with increasing braiding angles, while the transverse modulus and strength were opposite, and the performances of composites were better at higher fiber volume fractions. Compared with 3D4d braided composites, the transverse strength of 3D7d braided composites improved significantly. Furthermore, the three microstructural models were damaged in the order of interior, surface, and corner unit cell models during tensile loading. Especially, the fifth and seventh yarns within unit cell models were damaged firstly under longitudinal and transverse loads, respectively. This method adopted in this work provides a basis for predicting the mechanical properties of 3D7d braided composites.

基于制造三维七向 (3D7d) 编织预制件构建了三种理论微观结构模型，并研究了它们与编织角度、纤维体积分数和纱线填充因子的关系。结合桥接模型预测了编织参数、加载方向和编织结构对 3D7d 编织复合材料性能的影响。结果表明，纵向模量和拉伸强度随着编织角度的增加而降低，而横向模量和强度则相反，纤维体积分数越高，复合材料的性能越好。与3D4d编织复合材料相比，3D7d编织复合材料的横向强度显着提高。此外，在拉伸加载过程中，三个微观结构模型按内部、表面和角单元模型的顺序损坏。特别是，单元电池模型中的第五根和第七根纱线分别在纵向和横向载荷下首先损坏。本工作采用的这种方法为预测3D7d编织复合材料的力学性能提供了依据。