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。单向碳纤维增强塑料的光面拉伸试验及断裂过程观察用有限元法分析双悬臂梁试件裂纹尖端的应力。微裂纹的原子与概率分析。多微裂纹离散断裂的数值模拟。研究一采用光滑试样进行单向碳纤维增强塑料的横向拉伸试验，通过显微镜观察碳纤维与基体界面处萌生的多个小裂纹。根据观察结果对断裂过程进行了讨论。第二项研究对单向碳纤维增强塑料双悬臂梁试件裂纹尖端应力进行了有限元分析。研究了纤维对复合材料应力分布的影响，讨论了传统断裂力学对复合材料的适用性。在第三项研究中，对微裂纹进行了原子分析和概率分析。澄清了微裂纹的定义，提出了一种利用微裂纹的截面分布来确定内部微裂纹分布的方法。最后，对微裂纹的萌生和扩展过程进行了数值模拟。成功地模拟了微裂纹引起的离散断裂。

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.