Proposal of Numerical Experiment for Discrete Fracture of Fiber Reinforced Composites

为了评价复合材料的强度和韧性，进行了以下研究：1.使用光滑试样对单向碳纤维增强塑料进行拉伸试验，2.双悬臂梁试件裂纹尖端的有限元应力分析; 3.微观裂纹的原子分析和概率分析; 4.断裂过程的数值模拟在第一项研究中，单向碳纤维增强塑料的横向拉伸试验进行了使用光滑试样，并通过显微镜观察了多个小裂纹起源于碳纤维和基体的界面。在第二项研究中，对单向碳纤维复合材料双悬臂梁试件的裂纹尖端应力进行了有限元分析。研究了纤维对应力分布的影响，讨论了传统断裂力学对复合材料的适用性。第三部分对微裂纹进行了原子分析和概率分析。阐明了微裂纹的定义，提出了一种由微裂纹的截面分布确定内部微裂纹分布的方法，并对微裂纹的萌生和扩展进行了数值模拟。成功地模拟了微裂纹的离散断裂。

In order to evaluate the strength and toughness of composite materials, the following studies were carried out.1.Tensile tests of unidirectionally-carbon-fiber-reinforced plastic using smooth specimens, and the observation of fracture process.2.Stress analysis at the crack tip of Double Cantilever Beam specimen by means of Finite Element Method.3.Atomic and probabilistic analyzes on microcroaking.4.Numerical simulation of discrete fracture due to multiple microcracks.In the first study, transverse tensile tests of unidirectionally-carbon-fiber-reinforced plastic were carried out using smooth specimens, and the multiple small cracks initiated at the interface of carbon fiber and matrix were observed by means of microscope. The fracture process was discussed based on the observation results.In the second study, finite element analysis of the stress at the crack tip of Double Cantilever Beam specimen of unidirectionally-carbon-fiber-reinforced plastic was carried out. The effect of fibers on the stress distribution was examined and the applicability of conventional fracture mechanics to the composite material was discussed.In the third study, atomic and probabilistic analyzes on the microcrack were carrid out. The definition of microcrack was clarified and a method for determination of the distribution of internal microcracks from their cross-sectional distribution was proposed.In the last study, numerical simulation of the initiation and propagation of microcracks was carried out. The discrete fracture by microcracking was successfully simulated.