植物纤维层次多尺度计算分析及其增强水泥基复合材料研究

Compared to conventional synthetic fiber materials, natural fibers?are low in density and cost, high in tensile strength, and biodegradable, thus are suitable reinforcements for developing environment-friendly composites. They have attracted much attention of researchers in material science and engineering throughout the world.?In this project, we forcus on the microstructure study of two natural fibers including bamboo fiber and hemp fiber and their reinforced composites. Theoretical, numerical analysis and experimental observation will be conducted on these natural materials to characterize their hierarchical and multi-scale structure by optional scale definition, establish the corresponding composite microstructure numerical model based on finite element technique, analyze related mechanical properties of each layer of the natural fibers and reveal the nature of the load transfer and excellent mechanical properties of the fibers between different layers. Also, from the viewpoint of composite, the corresponding relation of effective mechanical properties of fibers and their microstructures are determined. Besides, the microstructures of bamboo and hemp fibers are compared to show their difference of mechanical properties. Subsequently, based on the research results on the hierarchical characteristic of the natural fibers, the cement-based natural fiber reinforced composites shown in practical and large scale are developed by introducing the hierarchical multi-scale structure of the natural fibers, and the corresponding design theory and numerical analysis method are established to determine the equivalent properties of such natural fiber reinforced composites. Meanwhile, the effects of fiber mictostructure, distribution, volume fraction and so on are considered to show the interaction of fibers and matrix and load transfer between them. Also, the effects of bamboo and hemp fibers on the composites are studied to show their difference. As a result, the environment-friendly engineering natural composites are developed in the project according to proper usage of natural fibers.

和人工合成纤维相比，植物纤维易从植物中提取分离，具有较小的密度、较高的拉伸强度、可生物降解、造价低廉，因此非常适合作为环境友好型复合材料的增强体。本项目以竹纤维和苎麻纤维及其增强复合材料为研究对象，从植物纤维的微结构多尺度构型出发，利用理论、实验和数值计算方法系统研究植物纤维的层次结构特征和多尺度特点，进行合理的尺度划分，构建植物纤维层次多尺度有限元计算力学模型，并在不同尺度下分析材料的力学特性，研究各层级间的荷载传递机制，揭示植物纤维优异力学性能的本质，建立纤维整体力学性能和层次微结构之间的定量关系，比较分析两种植物纤维微结构导致的力学性能差异；然后进行尺度递推，研究实际尺度的植物纤维增强水泥基复合材料，分析基体相和纤维间的相互作用规律，从机理上解释复合材料的整体力学性能和植物纤维微结构之间的关系，并比较不同增强相对复合材料性能的影响，为科学选择植物纤维和设计复合材料提供技术依据。

和人工合成纤维相比，植物纤维易从植物中提取分离，具有较小的密度、较高的拉伸强度、可生物降解、造价低廉，因此非常适合作为环境友好型复合材料的增强体。本项目以苎麻纤维及其增强复合材料为研究对象，从植物纤维的微结构多尺度构型出发，利用实验和数值计算方法系统研究植物纤维的层次结构特征和多尺度特点，进行合理的尺度划分，构建植物纤维层次多尺度有限元计算力学模型，并在不同尺度下分析材料的力学特性，研究各层级间的荷载传递机制，揭示植物纤维优异力学性能的本质，建立纤维整体力学性能和层次微结构之间的定量关系，比较分析两种植物纤维微结构导致的力学性能差异；然后进行尺度递推，研究实际尺度的植物纤维增强水泥基复合材料，分析基体相和纤维间及多个纤维之间的相互作用规律，从机理上解释复合材料的整体力学性能和植物纤维微结构之间的关系，并比较不同增强相对复合材料性能的影响，为科学选择植物纤维和设计复合材料提供技术依据。此外，为了提高计算效率，研究了具有多边形构造特征的基于基本解的杂交有限单元理论，并构造出了特殊的纤维/基体杂交单元和纤维/界面层杂交单元用于植物纤维增强复合材料的高效计算分析。