水泥基复合材料中钢纤维全场定向方法与增强机理研究

In conventional steel fiber reinforced cement-based composites, only the fibers that having direction the same or close to tensile stress effectively enhance the matrix. In this submission, it is attempted to investigate a novel All-field Aligned Steel Fiber Reinforced Cement-based Composite (AASFRC), in which steel fibers at any location have the same direction as that of the principle tensile stress..First, based on the numerical meso-structure model, which is derived from the interaction between steel fibers and matrix, the coupling effect between the orientation distribution of fibers and the stress field is analyzed. And the orientation distribution of steel fibers in AASFRC is optimized. As a result, the design methodology of AASFRC is proposed..Then, AASFRC specimens are prepared by aligning steel fibers using an assemble electromagnetic field. comparisons are made between the designed orientation of steel fibers and the actual orientation of steel fibers in AASFRC specimens, which is determined by X-ray computed tomography analysis. According to the comparisons, the electromagnetic field is optimized until the actual orientation distribution of steel fibers in specimens is the same as the designed fiber orientation. From the optimization process, the approach of preparing AASFRC is obtained..Finally, the mechanical properties of AASFRC are tested and comparisons are made with that of single-direction Aligned Steel Fiber Reinforced Cement-based Composite (ASFRC) and conventional Steel Fiber Reinforced Cement-based Composite (SFRC). In the tests, the Digital Image Correlation analysis, Acoustic Emission analysis and X-ray Computed Tomography analysis are performed to obtain the nature of the interaction between the macro- performance, meso-structure and deterioration process is explored. And the mechanism of AASFRC is disclosed..The output of this investigation includes the mechanism, properties and application technology of the AASFRC. And it is expected to achieve significant progress in the research of steel fiber reinforced cement-based composites.

传统钢纤维增强水泥基复合材料中，只有与拉应力方向一致的纤维能有效发挥增强作用。本项目试图突破传统模式，研究任意位置钢纤维与主拉应力方向一致的全场定向钢纤维增强水泥基复合材料（AASFRC）。首先，建立基于纤维与基体相互作用的细观数值模型，分析纤维方向与应力之间的耦合效应，优化纤维方向，掌握AASFRC设计方法。其次，研究磁场诱导钢纤维曲线定向和二维定向、进而全场定向的方法，通过X-CT分析钢纤维实际方向，优化定向参数，制备满足钢纤维全场定向要求的AASFRC，掌握制备方法。最后，进行全场定向、单向定向和随机乱向钢纤维增强水泥基复合材料的力学性能对比，通过数字图像相关方法、声发射和X-CT测试，分析宏观性能、细观结构与损伤过程之间的内在联系，揭示AASFRC的增强机理。通过本项目研究，有利于掌握AASFRC的理论、性能及应用技术，获得钢纤维增强水泥基复合材料研究的重大突破。

传统钢纤维增强水泥基复合材料构件中，因钢纤维方向与拉应力不一致而不能发挥增强作用，造成极大浪费。全场定向钢纤维增强水泥基复合材料构件中，任意位置钢纤维方向与拉应力一致，钢纤维增强作用充分发挥，构件力学性能较普通钢纤维混凝土大幅度提高，有必要系统研究钢纤维全场定向方法、增强作用与机理。.项目研究中，首先通过结构和数值分析，确定构件各处拉应力方向，以此作为钢纤维的方向场；其次，根据钢纤维定向要求，设计并构建了适用于各种常规构件的磁场装置，磁力线与构件中钢纤维方向场一致，在此基础上，制备了全场定向钢纤维增强水泥基复合材料简支梁、连续梁、轴拉圆孔板、双向板等常规构件，经检验钢纤维实际分布与设计基本一致，效果良好；然后，分析和测试了全场定向钢纤维增强水泥基复合材料构件的力学性能，与单向定向和随机乱向钢纤维试件相比，承载力分别提高30%、50%或更多，韧性提高一倍以上，全场定向钢纤维的增强作用大幅度提高；最后，分析了全场定向钢纤维水泥基复合材料的增强机理，与单向定向钢纤维相比，全场定向使所有位置的钢纤维增强作用得到进一步充分发挥，增强效果显著提高。项目成果在某市政桥梁伸缩缝钢纤维混凝土施工中使用，效果良好，通过工程使用，全面掌握全场定向钢纤维增强水泥基复合材料的施工技术。.全场定向钢纤维技术由于纤维增强作用充分发挥，结构或构件性能更高；保持性能不变时，可显著降低钢纤维用量，节约材料，降低成本，低碳节能。通过本项目研究，掌握了全场定向钢纤维混凝土的理论、性能及应用技术，可用于各种常规工程结构，获得钢纤维混凝土材料研究的重大突破。