基于复杂凸形硬/软化粒子微结构模型的颗粒材料传输性能研究

Granular materials such as cementitious materials, ceramics and glasses have been extensively used in industries. Transport properties of granular materials play an important role in their durability and server life. At a microscopic scale, granular materials are normally viewed as random packings of polydisperse hard/soft particles with different geometric morphologies representing various compositions. However, it is very difficult to characterize quantitatively relationships of transport properties and microstructures of granular materials with geometric configurations of particles, by experimental methods and spherical particle random packing models proposed so far. The ambition of this proposal is to develop a universal overlap detection algorithm of convex particles to simulate random packings of polydisperse complex convex hard/soft particles. Microstructural characteristics of hard particle phase, interface phase and soft particle phase will be quantitatively analyzed in granular materials, respectively, by combining with relevant theories and numerical simulation technologies. Subsequently, a theoretical predicting model for transport properties, microstructures and compositions of granular materials will be proposed by coupling the derived microstructural characteristics with transport properties, with composite theory applied. Furthermore, experimental studies on the chloride diffusion in cementitious materials will be presented to verify the reliability of the derived quantitative mechanism on the effects of geometric configurations of particles on microstructures and transport properties of granular materials. It is expected that this project will provide a theoretical support for improving the durability and service life of granular materials by optimizing structures of granular materials.

颗粒材料（如：水泥基材料、陶瓷、玻璃等）在国民生产中具有广泛的应用，其传输性能直接关系到材料结构的耐久性和服役寿命。在微观尺度上颗粒材料通常可以被看成由代表不同组份且形貌各异的多分散的硬/软化粒子随机堆积复合而成。但由于受到现有的实验手段和球形粒子随机堆积模型的局限，很难定量地表征含有粒子几何信息的颗粒材料微结构与其传输性能之间的关系。本项目拟从开发凸形粒子重叠检测的通用算法来建立复杂凸形硬/软化粒子随机堆积模型入手，结合相关理论和数值模拟试验定量地分析颗粒材料中硬化粒子、界面、软化粒子的各相微结构特征，利用复合材料理论将各相的微结构特征与材料的传输性能耦合，构建颗粒材料组成―微结构―传输性能之间的理论预测模型，并结合水泥基材料的氯离子扩散试验验证粒子的几何特征对颗粒材料的微结构和传输性能影响机制的可靠性，从而为通过优化颗粒材料的结构来提高其耐久性和服役寿命提供理论支持。

颗粒材料的宏观性能直接关系到其在工程应用中的耐久性和服役寿命。在微观尺度上颗粒材料通常是由形貌各异的多分散硬/软化粒子随机堆积而成。但受到现有的实验手段和球形粒子随机堆积模型的局限，很难定量地表征含有粒子几何信息的颗粒材料微结构与其传输性能之间的关系。本项目通过理论研究和数值模拟相结合的技术策略建立了单粒径和多粒径的复杂凸多面体、椭球、球柱体的硬化/软化粒子随机堆积模型，实现了大体积比凸形颗粒与界面组成的全级配混凝土三相复合微观结构模型；发展了弱界面体积分数的广义理论模型和数值框架，阐明了界面体积分数与颗粒组成之间的定量关联机制；首次提出了变指数的柱状孔隙逾渗阈值理论模型，高精度地预测了孔隙逾渗阈值、逾渗相变宽度和逾渗相关长度指数，攻克了柱状孔隙联通特征难以定量提取的技术瓶颈；建立了颗粒材料有效传输性能和弹性模量与其界面微结构和组成关联的多尺度理论框架；解决了界面微结构特征与材料传输性能和弹性性能难以定量关联的科学难题，揭示了颗粒的几何特性、分布细节以及界面微结构与颗粒材料传导率和弹性模量之间关联的内在机理。以第一作者(含通讯作者)在国际权威期刊Computer Methods in Applied Mechanics and Engineering (IF=3.95)、Composites Science and Technology (IF=4.87)、Materials & Design (IF=4.36)、Scientific Reports (IF=4.26)、Physical Review E等上共计发表SCI论文18篇；项目负责人分别受新加坡World Scientific出版社的SCI期刊《International Journal of Modern Physics B》和国内SCI期刊《物理学报》的邀请撰写颗粒材料计算力学的综述文章。参加国内外学术会议14次、邀请报告2次；申请发明专利4项、授权1项。获江苏省科学技术奖、江苏省教育科学研究成果奖（自然科学类）、江苏力学科学技术奖各一项。研究成果被国内外学者称为Xu 模型，并得到来自美国、英国、澳大利亚和中国的5位中外院士、8个国际SCI权威期刊编辑的正面高度评价和引用。培养研究生6名、博士后1名；项目负责人获江苏省自然科学优秀青年基金、入选江苏省六大人才高峰高层次人才培养对象。