热机械循环载荷下短纤维增强金属基复合材料性能分析

ANALYSIS OF SHORT FIBER REINFORCED METAL MATRIX COMPOSITES’PROPERTIES UNDER THERMO MECHANICAL CYCLIC LOADING

从复合材料内部组分的细观力学关系入手,选取代表体积元,基于Eshelby椭圆夹杂理论和瞬时体积平均的概念,通过集中张量描述纤维与基体以及纤维与纤维间的相互作用,并把在弹性范围内得到的各集中张量推广到弹塑性范围内,建立能够在弹塑性范围内分析热机械循环载荷作用下短纤维增强金属基复合材料的性质的模型。为了接近工程实际,假设纤维始终保持线弹性,对基体材料采用能反映bauschinger效应的混合硬化模型,依据基体的弹塑性状态决定复合材料整体的弹塑性状态。在塑性范围内,从各向异性的角度出发,采用增量法迭代得出每个加载步结束时复合材料整体以及各相的应力应变增量。编写控制应变和温度加载条件下,计算复合材料应力应变响应的程序,着重讨论纤维的外形、空间分布、体积百分比以及温度载荷对复合材料宏观性质的影响,并与相关的实验结果和数值结果进行比较。

Based on the internal micromechanical relation of composites and the Eshelby's solution of an ellipsoidal inclusion, the thermo-mechanical-cyclic constitutive equation of composites in the elasto-plastic range is established by selecting a representative volume, and employing the concept of instantaneous average over the volume and an extension of concentration tensors, which are used to described the interaction between fibers and matrix. To realistically model fiber composites in engineering application, it is assumed that the fiber phase always remains linearly elasticity and the matrix obeys the combined hardening model during the elasto-plastic response. Since the composites are completely anisotropic, an iterative method is derived to calculate the increments of stress and strain of composites at the end of each loading step. Through the numerical procedure, the elasto-plastical response of composites under different loading conditions, and the influence of fiber architecture (i.e. shape, volume fraction and the distribution of fiber orientation) are investigated. The performance of this method is compared with experimental and other numerical simulation results.