三维机织复合材料的一个细观力学模型

根据三维机织复合材料中细观几何和变形的周期性，提出了一种反映细观周期约束条件的组合梁单元模型，该模型既考虑了纤维束的偏轴拉压效应，又考虑了纤维束的弯／剪耦合效应和纤维束之间的相互作用，可以描述纤维束和基体中的细观应力分布。针对一种典型的三维机织复合材料，研究了根据编织参数确定材料细观结构的方法，在此基础上选取材料中最小周期的一段纤维束作为分析胞元，用上述模型分析了面内拉伸荷载下胞元中各相材料的细观应力，进而得到材料平均的宏观模量。材料试验和二维细观有限元分析证明了本模型的可靠性。研究表明，三维机织复合材料中，纤维束拉、弯耦合效应引起的细观应力在应力分析中不可忽略。

Micro Mechanical Model of 3D Woven Composites

A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.