中文摘要：

聚合物基体的变形局部化在复合材料破坏过程中起着重要作用。采用有限元分析方法, 借助用户材料子程序（UMAT）, 描述了具有应变软化特点的高聚物弹塑性的本构关系, 研究了纤维/环氧树脂复合材料在拉伸破坏过程中基体局部变形的演化规律, 分析了基体的局部应变软化对纤维/环氧树脂复合材料应力的影响。结果表明： 纤维的应力分布及基体的塑性变形具有不均匀性; 基体局部变形降低了邻近断点的完好纤维的应力集中程度; 随着纤维间距的增加, 邻近断点的完好纤维的应力集中区域变宽, 而且应力集中程度降低。

英文摘要：

The localized deformation of matrix plays an important role in determining the failure process of composites. In the current work, based on the finite element analysis, a proper elasto-plastic constitutive model considering the softening after yielding was introduced using the user-defined material mechanical behavior （UMAT） subroutine. Then the evolution of the localized deformation of matrix during the unidirectional tensile test of the fiber/epoxy composites was presented. The effect of the post-yield softening character of the polymer matrix on the loading transfer in the fiber/epoxy composites was studied. The results show that the stress distributions of fiber and the plastic deformation of matrix are nonuniform. The localized deformation of matrix reduces the degree of the stress concentration of the adjacent fiber. The range of the stress concentration in adjacent fiber becomes wider, while the stress concentration degree degrades, with the inter-fiber spacing increasing.