纤维增强金属基复合材料整体蠕变性能的细观力学分析

A Micromechanics Analysis on Overall Creep Properties of Fiber-Reinforced Metal-Matrix Composites

高温下金属基复合材料的蠕变主要由基体蠕变和界面扩散蠕变两部分构成,以往的研究中常常只考虑其中一种蠕变机理,从而导致得到的规律具有较大的局限性.本文提出了一种可预测金属基复合材料整体蠕变性能的细观力学方法,同时考虑了基体蠕变和界面扩散蠕变两种蠕变机理,导出了具有张量形式并满足不可压缩性的界面扩散蠕变应变表达式.采用Mori-Tanaka法和自洽法二者结果的平均以便更准确地计算纤维中的应力,揭示了两种蠕变机理相互影响的竞争关系.研究了恒定双轴荷载下的总体蠕变和固定位移约束下的应力松弛这两种常见蠕变问题,探究了基体蠕变与界面扩散蠕变两种蠕变机理在总蠕变中发挥的作用,考察了不同加载条件和不同纤维体积分数对复合材料整体蠕变行为的影响.

The creep of metal matrix composites at high temperatures is mainly composed of matrix creep and interfacial diffusion creep.In previous studies,only one of these two creep mechanisms was considered,leading to limited understanding of the overall creep behaviors of composites.In this paper,a micromechanics method was proposed,which is capable of predicting the overall creep performance of the metal-matrix composites.In this method,both matrix creep and interfacial diffusion creep are considered,and the tensor-form strain expression adhering to the incompressibility for the interfacial diffusion creep is derived.The stress in fibers is accurately calculated by averaging the results from Mori-Tanaka method and the self-consistent scheme.The competition relationship between the two creep mechanisms is revealed.Two commonly encountered creep problems,i.e.,the overall creep under constant biaxial loading and the stress relaxation under fixed displacement constraints,are studied.The effects of the matrix creep and the interfacial diffusion creep on the overall macroscopic creep are explored.The influences of the loading conditions and the fiber volume fraction on the overall creep behaviors of composite materials are examined.