三维四向编织复合材料刚度和强度的理论预测

以单胞模型为基础，将三维四向编织复合材料中相同走向的纤维束视为单向复合材料，利用桥联模型确定了单向复合材料的柔度矩阵，再将具有不同材料主向的单向复合材料的刚度矩阵通过体积平均，得到了三维四向编织复合材料的总体刚度矩阵，从而得到其工程弹性常数．然后，以单向复合材料为基础，基于等应变假设和桥联模型，确定出材料内各组分（纤维束和基体）的细观应力分布，且对纤维束采用Hoffman失效准则，对基体采用Mises失效准则，预报了三维四向编织复合材料的拉伸强度．

Theoretical Prediction of the Stiffness and Strength of Three-Dimensional and Four-Directional Braided Composites

Based on unit cell model,the 3D 4-directional braided composites can be simplified as unidirectional composites with different local axial coordinate system and the compliance matrix of unidirectional composites can be defined utilizing the bridge model.The total stiffness matrix of braided composites can be obtained by the volume average stiffness of unidirectional composites with different local axial coordinate systems and the engineering elastic constants of braided composites were computed further.Based on the iso-strain assumption and the bridge model,the stress distribution of fiber bundle and matrix of different unidirectional composites can be determined and the tensile strength of 3D 4-directional braided composites was predicted by means of the Hoffman.s failure criterion for the fiber bundle and Mises.failure criterion for the matrix.