不同纤维增强水泥基复合材料的基本力学性能研究

Basic Mechanical Behavior of ECC Made with Different Types of Fibers

开展了使用6种不同纤维配置纤维增强水泥基复合材料ECC的基本力学性能研究.探讨了纤维直径、纤维长度及纤维种类对纤维临界体积率的影响.通过4点弯曲试验,量测了不同掺量及不同种类纤维制成的ECC试件荷载-跨中截面挠度曲线,观测了破坏形态及裂缝分布、开展情况.试验结果表明,纤维直径是临界体积率的主要影响因素,且与临界体积率呈线性关系.使用碳纤维CF、玄武岩纤维BF制备的ECC试件,破坏时没有呈现出多点开裂现象,为脆性破坏.使用聚乙烯醇纤维PVA和聚丙烯纤维PP制备的试件表现出了良好的延展性,其应变硬化指数和韧性指数均较高.PP纤维制备的试件破坏时裂缝数量少,最大裂缝宽度相对较宽,而PVA纤维制备的试件破坏时裂缝数量多,最大裂缝宽度较小.

The basic mechanical behavior of engineering cementitious composite( ECC) made with six different types of fibers was investigated experimentally.The influences of diameter and length of fiber and type of fiber on the critical volume fraction of fiber was analyzed. The load-deflection curves at the mid-span section of four-point bending ECC specimens were measured and the failure modes and the development and distribution of cracks were observed. The test results showed that the diameter of fiber was a main factor that affected the dispersion of fiber into the cement base.The linear relationship of the diameter of fiber and the critical volume fraction was established by regression of the experimental data. The brittle failure mode occurred in ECC specimens made with carbon fiber( CF) and basalt fiber( BF); While the ECC specimens made with polyvinyl alcohol( PVA) fiber and polypropylene( PP) fiber exhibited a good ductility. The values of strain hardening index and toughness index of PVA and PP specimens were higher than those of CF and BF specimens. Several wider cracks distributed on the surfaces of PP specimens but more micro cracks were seen in the pure flexural zone of PVA specimens.