PVA纤维直径对水泥基复合材料抗拉性能的影响

研究了由2种性能相似、直径不同的聚乙烯醇(PVA)纤维增强的水泥基复合材料的单轴抗拉性能.试验结果表明:材料抗拉性能受纤维直径影响显著,在基材配比、纤维掺量均相同时,采用直径较大(d_f=39μm)PVA纤维的复合可获得应变硬化与多点开裂模式,其极限抗拉应变可达到2.6%;而采用直径较小(d_f=15μm)PVA纤维的复合材料却表现出明显的应变软化与单点开裂模式,其极限抗拉应变仅为0.1%左右;当采用细PVA纤维时,复合材料的抗拉强度有所提高;其主要原因是纤维的粗细影响了纤维的桥接应力.保证纤维从水泥石中拔出而非断裂是优化纤维桥接性能的基本条件.

Tensile Properties of Fiber Reinforced Cement Composite with Different PVA Fibers

The tensile properties of cementitious composites reinforced by two kinds of polyvinyl alcohol (PVA)fibers respectively were studied.Experimental results show that the tensile performance of the composites may be greatly influenced by the dimension of the fibers.If the fiber with diameter of 39 μm is used,the strain hardening and multiple cracking performances can be obtained under tensile load and the ultimate tensile strain may achieve 2.6%.By contrast,if the PVA fiber with diameter of 15 μm iS used,the composite behaves significant strain softening and single cracking model.The ultimate tensile strain a-ehieved iS only about 0.1%.The tensile strength of the composite reinforced with thinner fibers increases a little bit than that with the coarser one.The reasons of above different tensile performance are that the differences in crack bridging of the two composites.Crack bridging stress in composite is greatly controlled by the number of fibers bridging the cracks.Thinner fibers used in composite may lead less fibers to bridge the cracks due to fiber breakage.The fundamental requirement to enhance the crack bridging properties is to ensure fiber pull-out instead of breakage.