三维链网模型及短纤维增强复合材料行为预测

IMECH-IR > 力学所知识产出(1956-2008)

	三维链网模型及短纤维增强复合材料行为预测
	刘晓宇
导师	梁乃刚
	2001
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位类别	博士
英文摘要	以模拟短纤维增强复合材料正常服役与损伤破坏全寿命期力学行为为目标，本文的工作要点如下：1．提出了三维材料模型，建立了三维链网模型理论，构造了三维链网体胞，给出了体胞几何、物理参数的标定公式，证明该体胞能精确模拟泊松比从0-1／2的材料行为，文献中以往模型模拟泊松比的范围只能是0-1／3。进一步提出了简化三维链网模型，能够实现高计算精度、低计算费用的统一。2．开发了三维链网模型数值模拟软件，采用可视化界面实现前、后处理操作。该软件成为模拟非均匀介质，特别是短纤维复合材料，力学行为的有效工具。3．开展了用三维链网模型模拟短纤维增强复合材料的可行性研究，证明了三维链网模型具有与有限元同等水平的求解能力和计算精度。验证了一维链单元模拟针状增强体的可行性。实现对增强体体积份数高、排列不规则的工程复合材料模拟。与常规有限元离散比较，模拟短纤维增强复合材料的计算规模能降低两个数量级以上。4．研究了短纤维增强复合材料应变分布的统计规律，得到了局部应变统计量与宏观应变的关系，导出刚度张量的显示表达式。可以预测增强体任意分布、任意加载方式下材料的刚度，理论预测结果与实验吻合。5．模拟了短纤维增强复合材料塑性变形行为，给出了单取向增强体复合材料的弹塑性本构关系。数值模拟及理论预测结果与实验结果吻合。6．研究了材料损伤破坏过程，精确再现脆性断裂过程中的应力重分配，实现从群体微裂纹萌生、扩展、汇合到破坏的损伤演化全过程数值模拟。; Aimed at simulating the mechanical behavior of short-fiber reinforced composites (SFRC) in normal service and whole damage process, the present study focuses attention on the following points: 1. Based on a 3-D network material model developed in the present study, a 3-D network cell is suggested with its geometrical and physical parameters calibrated. It is proved that the 3-D network cell is able to exactly simulate materials with arbitrary Poisson ratio from 0 to 1/2, whereas the models in literatures are only suitable for materials with Poisson ratio from 0 to 1/3. A simplified model with high accuracy is also proposed to reduce computation cost. 2. A numerical simulation software based on the 3-D network theory is coded and the pre-treatment and post- treatment are dealt with a modern visualized operating interface. The software becomes an effective tool to simulate the mechanical behavior of heterogeneous media, especially of SFRC. 4. The feasibility for the 3-D network model to simulate SFRC is investigated. It is proved that 3-D network model possesses the same theoretical capacity and accuracy as conventional finite element models. The feasibility for the one-dimensional components of the 3-D network cell to simulate the needle-like reinforcers is also verified. Prediction is realized for determining the mechanical properties and behavior of engineering composites, in which needle-like reinforcers with high volume fraction are irregularly distributed in 3-D space. Compared with conventional finite element models, the computation scale can be reduced at least by 90%. 5. The strain distribution regularity of SFRC is studied, and the relation between the statistical value of local strain and macroscopic strain is obtained. An explicit stiffness tensor is derived to predict stiffness modulus of composite with arbitrary reinforcer orientation under any loading condition. The prediction is in good agreements with experiments. 5. The plastic behavior of SFRC is simulated, and the elasto-plastic constitutive relation of composites with unidirectionally oriented reinforcers is derived. The numerical results and theoretical prediction are in good agreements with those of experiments. 6. In the investigation on the damage process of heterogeneous materials, stress re distribution is accurately reproduced during brittle fracture. The whole damage evolution is numerically simulated thought-out crack initiation, growth, propagation, coalition up to rupture.
索取号	29966
语种	中文
文献类型	学位论文
条目标识符	http://dspace.imech.ac.cn/handle/311007/23480
专题	力学所知识产出(1956-2008)
推荐引用方式 GB/T 7714	刘晓宇. 三维链网模型及短纤维增强复合材料行为预测[D]. 北京. 中国科学院研究生院,2001.

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