聚乙烯醇—钢纤维混杂增强水泥基复合材料力学性能研究

发布时间：2018-06-15 10:43

本文选题：聚乙烯醇-钢纤维混杂增强水泥基复合材料 + 基材强度　；参考：《清华大学》2016年博士论文

【摘要】：高延性低干缩纤维增强水泥基复合材料(LSECC)是为了克服混凝土的脆性,解决传统高延性纤维增强复合材料(ECC)收缩问题而发展起来的新型土木工程材料。但高强LSECC依靠单掺聚乙烯醇纤维难以保留高延性特征,不能适应高强高延性的工程需求。本研究旨在通过混杂聚乙烯醇纤维和钢纤维,实现LSECC高强度与高延性的匹配。基于此目的,对聚乙烯醇-钢纤维混杂增强水泥基复合材料力学性能开展了系统的试验研究和理论模拟分析,同时针对工程实际问题开展了LSECC材料的工程应用研究。在LSECC中聚乙烯醇纤维掺量不变的基础上,试验测试了混杂纤维复合材料的轴拉、抗弯、抗压基本力学性能,重点关注基材强度(4个水胶比)、钢纤维添加量(体积掺量0-1.0%)对复合材料力学性能的影响。结果表明,随钢纤维添加量增加,开裂强度、极限强度和极限拉应变同时提高,裂纹宽度显著降低。基材强度越高,钢纤维作用越明显。本研究获得了抗压强度70 MPa、极限拉应变10000-18000微应变、裂纹宽度30-60?m的高强高延低缝宽混杂纤维水泥基材料。基于预切口梁抗弯试验,逆推求解了混杂纤维复合材料裂纹间桥接应力-裂纹宽度关系,并借鉴已有纤维桥接应力理论模型,建立了基于纤维、基材、界面参数的应力-裂纹宽度关系。通过理论模型分析了钢纤维尺寸对桥接应力的影响。建立了基于断裂力学原理的混杂纤维复合材料抗弯性能预测模型,模拟了混杂纤维复合材料抗弯性能,模拟结果与抗弯试验结果吻合良好。经钢纤维尺寸优化的混杂体系抗弯性能显著提升。该模型建立了水泥基材、纤维和界面参数与宏观力学性能的联系,为构建基于性能的混杂纤维复合材料设计方法提供了基础。针对工程实际问题,开展了LSECC在混凝土结构防护面层和混凝土路面板延性接缝两个方面的应用研究。首先,通过模拟和试验研究了LSECC-混凝土复合梁抗弯性能,结果显示在混凝土底部复合LSECC可有效提升复合梁抗弯性能,同时分析了材料强度、LSECC层厚对复合梁抗弯性能的影响。其次,提出了采用LSECC延性段取代混凝土路面切缝的无缝路面设计理念,通过模拟试验和试点工程验证了设计理念的可行性,结果显示,延性段通过形成细微裂纹吸收两侧混凝土路面板变形,有效防止混凝土板开裂,无缝混凝土路面得以实现。
[Abstract]:High ductility and low shrinkage fiber reinforced cement matrix composite (LSECC) is a new type of civil engineering material developed to overcome the brittleness of concrete and to solve the shrinkage problem of traditional high ductile fiber reinforced composites (ECC). But high strength LSECC is difficult to retain high ductility and can not adapt to high strength and ductility depending on the single doped polyvinyl alcohol fiber. The purpose of this study is to realize the matching of high strength and high ductility of LSECC through hybrid polyvinyl alcohol fiber and steel fiber. Based on this purpose, the mechanical properties of the polyvinyl alcohol steel fiber reinforced cement matrix composites are systematically studied and theoretically simulated, and the LSECC materials are carried out for the practical problems of the engineering. On the basis of the constant mixing of polyvinyl alcohol fiber in LSECC, the basic mechanical properties of the hybrid fiber composites were tested on the basis of the constant mixing of the polyvinyl alcohol fiber. The effect of the base material strength (4 water to rubber ratio) and the amount of steel fiber added (volume content 0-1.0%) on the mechanical properties of the composites was mainly concerned. The increasing of the dimension, the cracking strength, the ultimate strength and the ultimate tensile strain at the same time, the crack width decreased significantly. The higher the base material strength, the more obvious the effect of the steel fiber. This study obtained the compressive strength 70 MPa, the ultimate tensile strain 10000-18000 micro strain, the crack width 30-60? M high strength and low slit wide hybrid fiber cement base material. The relationship between the stress crack width of the bridge between the cracks and the stress crack width of the hybrid fiber composite material is solved by the inverse bending test, and the relationship between the stress and the crack width based on the fiber, substrate and interface parameters is established for reference. The influence of the steel fiber size on the bridge stress is analyzed by the theoretical model. The bending performance of hybrid fiber composites is simulated by the fracture mechanics principle. The bending properties of hybrid fiber composites are simulated. The simulation results are in good agreement with the bending test results. The flexural performance of the hybrid system is greatly improved by the steel fiber size optimization. The model has established the base material, fiber and interface parameters and macroscopic mechanical properties of the model. It provides a basis for the construction of performance based hybrid fiber composite design method. In view of the practical problems of engineering, the application of LSECC in two aspects of concrete structure protection surface layer and concrete pavement slab ductile joint is carried out. First, the bending performance of LSECC- concrete composite beams is studied by simulation and test, and the results are studied. It is shown that composite LSECC at the bottom of concrete can effectively improve the bending resistance of composite beams. At the same time, the effect of material strength and LSECC layer thickness on the bending resistance of composite beams is analyzed. Secondly, a seamless pavement design concept is put forward to replace the slit of concrete pavement with LSECC ductility section. The feasibility of the design concept is verified by the simulation test and pilot project. The results show that the ductility section can effectively prevent the cracking of the concrete slab through the formation of fine cracks in the concrete pavement slab on both sides, and the seamless concrete pavement can be realized.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU528.04

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