纤维取向分布对水泥基复合材料力学性能的影响及其评价方法的研究进展

Review on the Effect of Fiber Orientation Distribution on MechanicalPerformance of Cement-based Composites and Its Evaluated Methods

纤维增强水泥基复合材料是以水泥净浆、砂浆或混凝土为基材,外掺钢纤维、聚乙烯醇纤维或碳纤维等纤维,从而提升基材力学性能和耐久性能的一种新型水泥基复合材料。基于纤维增强基体理论,当纤维均匀分布且取向平行于基体受力方向时,其在微观层面能有效抑制因水泥基复合材料内部拉应力低而产生的微裂缝,同时传递裂缝间的应力以防止其进一步发展;在宏观层面,纤维可显著提高水泥基复合材料的抗拉抗弯强度及延性。然而,纤维的类型、长径比和掺量以及施工工艺等因素均会影响纤维在基体中取向分布,严重削弱其在微裂缝间的桥接作用,增加其掺量。这不仅对水泥基复合材料的抗拉抗弯强度、韧性增强效果等工作性能造成不利影响,而且提高其生产成本,极大限制其应用。基于国内外学者对纤维取向分布与水泥基复合材料的力学性能之间的关系的大量探究,本文系统阐述了纤维取向和空间分布对水泥基复合材料力学性能的影响,总结了影响纤维取向分布的主要因素,同时介绍了评价纤维在基体中取向分布情况的各类检测手段,并分析了不同检测手段的优劣性,最后论述了当前纤维取向分布预测模型的发展现状。本文可为调控纤维在水泥基复合材料取向分布、提升结构的抗拉抗弯强度及韧性、降低纤维增强水泥基复合材料的生产成本的相关研究提供参考。

Fiber-reinforced cement-based composites,employing the cement paste,mortar or concrete as the base material and adulterated by various types of fibers,such as steel fiber,polyvinyl alcohol fiber,carbon fiber etc.,to improve mechanical properties and durability of the base material,is a new type of cement-based composites.Based on the fiber-reinforced matrix theory,when fibers are uniformly distributed and their orientation is parallel to the direction of the matrix,they can effectively restrain the micro-fracture caused by the low tensile stress in cement-based composites and transfer the stress between the micro-fracture to prevent its further development at a micro level,while they can significantly improve the tensile and bending strength as well as ductility of cement-based composites at a macro level.However,the factors,such as types,the aspect ratio and dosages of fibers as well as the construction technology,affect the fiber orientation distribution in the matrix,severely weakening the fiber bridging action between the micro-fracture and increasing the fiber content,which not only adversely influences the tensile and bending strength as well as ductility-enhancing effect of cement-based composites,but also increases their production cost and greatly restricts their application.Based on a large amount of recent research on the relationship between fiber orientation distribution and mechanical properties of cement-based composites by domestic and foreign scholars,this paper systematically summarizes the influence of orientation and spatial distribution for fibers on mechanical properties of cement-based composites,and summarizes the main factors affecting fiber orientation distribution.At the same time,various detection methods for evaluating fiber orientation distribution in matrix are introduced,and the advantages and disadvantages of different detection methods are analyzed.Finally,the development status of prediction models for fiber orientation distribution is discussed.This paper can provide reference for controlling the orientation distribution of fiber in cement-based composites,improving the tensile and bending strength as well as ductility of structures and reducing the production cost of fiber-reinforced cement-based composites.