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

先进复合材料的疲劳断裂机理（微观、细观和宏观方法）

基本信息

批准号：
09305010
负责人：
JONO Masahiro
金额：
$ 18.82万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09305010/
关键词：
Fatigue Strength Fatigue Crack Growth Delamination Crack FRP MMC 3% Silicon Iron Microscopic Observation Slip Deformation き裂開閉口微少き裂層間はく離き裂進展 FRP き裂開閉口挙動

项目摘要

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

在静态蠕变条件下，对单向碳纤维增强热塑性塑料（CFRTP）进行了高温（473 K）复合型分层裂纹扩展试验。裂纹扩展速率da/dt随着混合模式比G D2 I D2/G D2 II D2的减小而以总能量释放速率G D2 I D2的模式I分量表示变高。这意味着裂纹扩展速率被总能量释放速率的模式II分量G D2 II D2加速。结果表明，Ⅱ型裂纹尖端的蠕变变形区大于Ⅰ型裂纹尖端的蠕变变形区。对晶须增强铸造6061铝基复合材料、颗粒增强粉末冶金和铸造2024铝基复合材料进行了反向平面弯曲试验，研究了SiC颗粒增强铝基复合材料的拉伸断口形貌，发现基体沿着主应力方向被拉伸，断裂发生在纤维与基体界面处。 ...更多信息表面缺口试样。采用塑性复制技术对疲劳小裂纹的萌生和扩展行为进行了连续监测和详细研究。晶须增强铸造复合材料的裂纹萌生机制是SiC晶须在制造过程中形成的块状体与基体之间的界面开裂，颗粒增强粉末冶金复合材料的裂纹萌生机制是SiC增强颗粒附近基体的循环滑移变形。两种材料的疲劳强度均高于未增强的合金，这是由于SiC晶须或紧密结合的基体/颗粒界面限制了基体的循环变形，从而导致疲劳裂纹的延迟或萌生。采用伺服液压疲劳加载系统，对取向3%硅铁进行了恒幅疲劳裂纹扩展试验。疲劳裂纹尖端周围的试样表面的配置被转移到一个薄的复制膜，并通过原子力显微镜（AFM）检查。沿两个优选滑移方向（±55°）沿着清晰地观察到从裂纹边缘发出的离散滑移线。这意味着两个优先滑移同时以几乎相同的程度起作用，疲劳裂纹以近I型扩展。在加载和卸载过程中连续观察到滑移变形，发现疲劳裂纹尖端后的滑移作用导致裂纹闭合，而裂纹尖端的滑移作用导致裂纹扩展。利用图像处理技术定量测量了一个循环过程中的表面位移。载荷与滑移变形的关系模式与载荷与裂纹尖端张开位移CTOD的关系模式具有良好的相关性，裂纹尖端附近的滑移距离对应于理想的CTOD。少