基于真实三维微观结构研究SiCp/Mg复合材料细观力学性能

The mechanical and physical properties of SiCp/Mg composites seriously depend on its microstructures, characterizating and predicting the structure design, property evolution and damage failure of composites should be based on the accurately characterization of composite microstructures， Therefore, the related model of "three dimensional microstructure-visual presentation-mechanical properties" i.e. the forward materials prediction and the reverse materials design model, was built by combining serial section-based three dimensional reconstruction, molecular dynamics simulation and finite element analysis. Firstly, the three dimensional real microstructures of SiC reinforcement particles, Mg alloy matrix and interface were built by using serial section-based three dimensional reconstruction and molecular dynamics simulation. The three dimensional shape of composite microstructures can be visualized. Then, based on the real three dimensional microstructures of composites, the effects of the microstructures of SiC reinforcement particles, Mg alloy matrix and interface on the micro-macro mechanical properties, physical properties and deformation failure mechanism of SiCp/Mg composites were researched by using finite element analysis. Moreover, the quantitative relationship between the microstructure and the macroscopic properties of SiCp/Mg composites were established. In the study, the inadequate microscopic information in the micromechanical research of composites was overcome, and it also provided the important theoretical foundations for the structure optimization, failure analysis and preparation process of SiCp/Mg composites, and so on.

SiCp/Mg复合材料内部的微观结构严重影响复合材料力学性能和物理性能，对其结构设计、性能演化、损伤失效的表征与预报必须建立在准确表征复合材料微观结构基础上。所以，本项目把连续切片三维重构、分子动力学和有限元分析相结合建立"三维微观结构-可视化演示-力学性能"相关联的正向材料预测与反向材料设计模型。首先，采用连续切片三维重构和分子动力学建立SiC增强颗粒、Mg合金基体及界面三维真实微观结构，实现SiCp/Mg复合材料微观结构三维可视化；然后，基于真实三维微观结构，借助有限元揭示SiC增强颗粒、Mg合金基体、界面等微观结构对SiCp/Mg复合材料宏微观力学性能、物理性能、变形失效机理的影响，定量建立SiCp/Mg复合材料微观结构与宏观性能之间关系。该研究克服了复合材料细观力学研究中微观信息考虑不足，为SiCp/Mg复合材料结构优化、失效分析、制备工艺等提供重要的理论依据。

本项目研究内容有：借助图像处理和识别技术，分别建立颗粒增强镁基、铝基复合材料真实微观结构的有限元模型，运用该模型分析计算颗粒增强复合材料在不同应变速率为下的动态力学性能；在真实微观有限元模型基础上运用子模型技术，并借助子模型分析技术研究复合材料增强颗粒对其微观结构失效的影响。获取的研究结果有：运用真实微观结构有限元模型研究发现，低体积分数的颗粒增强复合材料流变应力随着应变速率的增加呈现先升高后降低的趋势，在较高应变率下，颗粒增强复合材料流变应力出现降低趋势是由于复合材料内部损失或基体热软化甚至局部熔化导致的。当应变低于0.62 时，带有棱角的颗粒比圆形颗粒强化效果好，当应变大于0.62 时，情况正好相反；借助子模型分析技术研究复合材料增强颗粒对其微观结构失效的影响。研究结果表明，增强颗粒为正四边形时，颗粒增强复合材料基体容易发生失效。颗粒团簇提高复合材料刚度，但降低了复合材料失效应变。当颗粒增强金属基复合材料达到失效状态， 增强颗粒密度越大，复合材料失效面积增大。