Fatigue Fracture Mechanism of Advanced Composite Materials (Micro-, Meso- and Macroscopic Approach)

在elevated temperature （473 K） were carried out using unidirectionally carbon fiber reinforced thermoplastics （CFRTP） under static creep condition。The crack propagation rate， da/dt， became higher in terms of mode I component of total energy release rate， GイD2IイエD2， as mixed mode ratio， GイD2IイエD2/GイD2 IIイエD2， decreased。This implied that crack propagation rate was accelerated by mode II component of total energy release rate， GイイD2IIイエD2。它发现了一个由模式I组成的CreativeDeformation区域周围的裂缝尖端比模式I大。分形观测显示，矩阵沿着光纤和矩阵之间的接口延伸了主要压力和断裂的方向，反向平面弯曲测试对SiC强化铝复合物的三种作用，命名为whisker强化铸造6061铝复合物，和颗粒强化P/M和铸造2024铝复合物，具有浅 ... More 表面标记的特殊物质。小肥胖裂缝的启动和增长行为是由塑料复制技术和详细调查连续监测的。在一个Whisker再注入铸造复合物中发现裂纹启动机制在矩阵和SiC Whisker之间的接口裂纹，在哪里SiC Whisker的Lump是在制造过程中合成的，以及在粒子再注入P/M复合物中，在矩阵中循环滑动变形在基体中的SiC再注入粒子中。两种材料的疲劳强度高于未经重新输入的合金，即SiC威士忌或严格边界矩阵/粒子接口的限制性矩阵的循环变形，在延迟或疲劳裂纹启动中结果。当在一个粒子重新注入铸造复合脂肪裂纹容易在矩阵/粒子接口的铸造缺陷时，这个预先裂纹启动结果是在最低的裂纹启动强度下。脂肪裂纹增长测试在恒定的增量加载下被用于一个以颗粒为导向的3%硅铁使用servo-hydraulic脂肪加载系统。特定表面的缺陷裂缝尖端的配置被转移到一个薄的复制片，并通过原子力显微镜（AFM）的意义进行了测试。Discrete slip lines which emanated from crack edges were observed clearly along the two preferred slip directions （±55°）。这意味着两个首选的滑动操作到几乎唯一的明显范围同样和肥胖的裂缝grew在接近模式I。加载和卸载期间的滑动变形是成功的，它发现了在裂缝封闭中发现的滑动背后的动作，以及在裂缝生长中传播的裂缝尖端。在一个周期内，表面置换是通过使用图像处理技术来量化的。加载和滑动变形之间的关系模式与加载和裂缝打开之间的关系、CTOD以及裂缝尖端与理想CTOD之间的滑动距离相关。Less（低）

Mixed mode delamination crack growth tests at elevated temperature (473K) were carried out using unidirectionally carbon fiber reinforced thermoplastics (CFRTP) under static creep condition. The crack propagation rate, da/dt, became higher in terms of mode I component of total energy release rate, GィイD2IィエD2, as mixed mode ratio, GィイD2IィエD2/GィイD2IIィエD2, decreased. This implied that crack propagation rate was accelerated by mode II component of total energy release rate, GィイD2IIィエD2. It was found that creep deformation area around the crack tip by mode II component was larger than that by mode I. Fractographic observation showed that matrices were elongated along the direction of main stress and fracture occurred at the interface between fiber and matrix.Reversed plane bending tests were conducted on three kinds of SiC reinforced aluminum composites, namely whisker reinforced casting 6061 aluminum composite, and particle reinforced P/M and casting 2024 aluminum composites, with shallow … More surface-notched specimens. Initiation and growth behavior of small fatigue cracks were continuously monitored by a plastic replication technique and investigated in detail. Crack initiation mechanism on a whisker reinforced casting composite was found characterized by the interface cracking between matrix and SiC whiskers, where the lump of SiC whiskers was composed in a manufacturing process, and that on particle reinforced P/M composite was cycle slip deformation in matrix in the vicinity of SiC reinforcement particle. Fatigue strength of both materials was higher than that of unreinforced alloy due to the fact that SiC whiskers or tightly bounded matrix/particle interface restricted cyclic deformation of matrix, which resulted in the delay or fatigue crack initiation. While in a particle reinforced casting composite fatigue crack easily initiated at a casting defect at matrix/particle interface, and this premature crack initiation resulted in the lowest crack initiation strength.Fatigue crack growth test under constant amplitude loading was conduced on a grain-oriented 3% silicon iron using servo-hydraulic fatigue loading system. The configuration of specimen surface around fatigue crack tip was transferred to a thin replica film and examined by means of an atomic force microscope (AFM). Discrete slip lines which emanated from crack edges were observed clearly along the two preferred slip directions (±55°). It implies that two preferential slips operated to almost identical extent simultaneously and fatigue crack grew in near mode I. The slip deformation during loading and unloading was observed successively and it was found that the operation of slips behind the fatigue crack tip resulted in crack closure and that at the crack tip brought about crack growth. The surface displacement during one cycle was measured quantitatively by using image processing technique. The pattern of the relationship between load and slip deformation was correlated well with that between load and crack tip opening displacement, CTOD, and the slipping distance near the crack tip corresponded to the ideal CTOD. Less