基于三维结构演化表征的复合材料损伤机制研究

发布时间：2018-01-08 11:00

本文关键词：基于三维结构演化表征的复合材料损伤机制研究　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：人工制造复合材料和自然界中生物复合材料由于具有优异力学性能而为力学家和材料科学家所广泛关注。复合材料这种优异性能与其微结构组织形态、分布、以及它们之间的相互作用密切相联。因此,研究复合材料三维微结构在载荷作用下的演化过程以及相互作用机理,对于深入认识复合材料的损伤机制和力学性能分析,进而实现结构优化设计具有重要的理论意义和工程应用价值。本文针对具有简单结构的单纤维复合材料、规则交错叠片文石纤维结构的凤凰螺贝壳和复杂三维随机结构的短纤维增强复合材料开展了相关研究工作。通过亚微米分辨率的同步辐射CT实验,获得相应材料内部三维形貌演化图像(如孔洞产生、微裂纹萌生、扩展等),数值化提取真实微结构形貌和微结构变形演化信息,得到与材料力学性能相关的力学参量,结合相应的力学模型,分析揭示了复合材料不同三维结构之间的相互作用机理以及孔洞、微裂纹等萌生、扩展、演化的损伤机制。本文的主要研究内容和创新点如下:一、提出了应变集中累积诱导的微裂纹萌生机制以及纤维界面变形局部化的远程损伤机制。1)开展了单纤维复合材料损伤演化的同步辐射CT实验研究,获得了微裂纹萌生、扩展和破坏过程中的三维形貌及变形演化图像,观察到了裂纹萌生前基体内部局部大变形现象,据此提出了应变集中累积诱导的微裂纹萌生机制。2)当裂纹扩展至纤维与基体之间的界面区域,产生了局部非线性变形现象,提出裂纹尖端影响下的纤维界面变形局部化的远程损伤机制。二、揭示了交错叠片文石纤维结构微裂纹路径偏转的增韧机理。1)实验获得了凤凰螺贝壳中的三维微裂纹形貌演化,观察到了反"C"型裂纹这一特殊的损伤演化现象,提出了第一级文石纤维结构薄弱层多重开裂增韧机制。2)基于凤凰螺加载实验中观察到的网状裂纹形貌,提出了第二级文石纤维结构桥接裂纹面增韧机制。三、研究了短纤维复合材料的微损伤过程的关键机制,提出了"纤维端部聚集引发孔洞连通"的裂纹萌生模式。1)基于SR-CT实验观察到纤维端部与孔洞之间的接触关系,提出剪应力集中导致孔洞萌生的机制。研究与分析表明:纤维长度和取向决定了纤维端部的剪应力集中程度,从而也导致是否诱发孔洞萌生。2)实验观察到产生微裂纹的纤维端部聚集现象,据此提出了"纤维端部聚集引发孔洞贯通"的裂纹萌生模式。在这个模式中,相邻纤维端部临界距离le和纤维端部聚集数目Ne这两个关键结构参数起着决定性作用。最后,对全文的工作进行了总结,展示了本文的主要研究内容和结果,并提出了未来工作的方向和研究思路。
[Abstract]:Artificial biological composite in nature and due to their excellent mechanical properties as scientists and materials scientists concern. Distribution of the composite material of excellent properties and microstructure, morphology, and their interactions are closely linked. Therefore, research on evolution process of composite 3D micro structure under load and the interaction mechanism, to further understand the damage mechanism and the mechanical properties of the composite analysis, so as to realize the structure optimization design has important theoretical significance and practical value. Based on the single fiber composite material has the advantages of simple structure, short fiber cross laminated shell epidromis aragonite fiber structure and complex structure of three-dimensional random reinforced composite the material is studied by experiment. The sub micron resolution of synchrotron radiation CT, to obtain the corresponding material The three-dimensional morphology evolution images of internal material (such as holes generated micro crack initiation, propagation, etc.) numerical extraction of real deformation evolution of microstructure morphology and microstructure, mechanical parameters associated with the mechanical properties of the material, combined with the corresponding mechanics model, analysis between composite materials of different three-dimensional structure and interaction mechanism void, initiation and propagation of micro cracks and damage evolution mechanism. The main research contents and innovations are as follows: first, the micro crack initiation induced by strain concentration accumulation mechanism and damage mechanism of remote fiber interface deformation localization.1) carried out the research of synchrotron radiation CT single fiber composite damage evolution. The micro crack initiation, propagation and evolution of 3D image deformation and failure process, the crack was observed in the matrix of local adorable deformation phenomenon, put forward The micro crack initiation mechanism of strain concentration accumulation induced by.2) when the interface area between the crack extension to the fiber and the base deformation phenomenon of local nonlinear, remote damage mechanism of fiber interface is proposed under the influence of crack tip deformation localization. Two,.1 reveals the toughening mechanism of staggered laminated aragonite fiber structure of micro crack path deflection the evolution of 3D) Phoenix screw in the shell micro crack morphology, observed the reverse "C" crack evolution this special damage phenomenon, put forward the first level of aragonite fiber structural weak layer multiple cracking toughening mechanism of.2 mesh) Phoenix screw loading crack morphology observed in experiments based on the proposed second level structure of aragonite fibers bridging the crack surface toughening mechanism. Three, study the key mechanism of short fiber composite micro damage process, put forward the "end of the fiber aggregation caused by pore connectivity. Crack initiation mode.1) SR-CT observed the contact relationships between the fiber end and hole based on the proposed shear stress concentration mechanism leading to the initiation of the void. Research and analysis shows that the fiber length and orientation determines the shear stress concentration degree of the fiber ends, which also led to the initiation of the void is not induced by.2) experimental observation to produce the phenomenon of micro crack fiber ends together, put forward "fiber end crack void coalescence induced aggregation" initiation mode. In this mode, the adjacent fiber end critical distance le and fiber end aggregation number Ne the two key structural parameters play a decisive role. Finally, the full text of the work summarized, shows the main research contents and results, and put forward the future direction and research work.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB33;TB301

【参考文献】