试验研究了短切碳纤维增强水泥基复合材料（CFRC）的压阻效应,获得了正、负两种压阻效应相互转换的全过程。从隧道效应和孔隙的连通性角度对该现象的产生机理进行了探讨。结果表明,在连续烘干和单向循环加载条件下,CFRC的压阻效应会随含水量变化而发生改变。多数情况下,CFRC的体积电阻率随压应变单调减少,压阻效应为正。含水量越少,正压阻效应越明显。当含水量减少到约3.19%~4.04%的范围时,CFRC的体积电阻率随压应变单调增加,压阻效应为负。与正压阻效应相比,负压阻效应表现更强。CFRC的正、负压阻效应及其相互转换是隧道效应和孔隙连通性两方面相互影响的必然结果。
The piezoresistivity of short carbon fiber reinforced cement-matrix composites（CFRC） was experimentally studied.The whole process of transition from positive to negative piezoresistivity was observed.The results show that under continuously drying and uniaxially cyclic loading,both positive and negative piezoresistivity occur in CFRC due to the variation of moisture content in the composites.For most cases the electrical resistivity of the composites decreases monotonically upon longitudinal compression,and piezoresistivity tends to be positive.However,its magnitude varies.Lower moisture content leads to stronger piezoresistivity.When moisture content reduces to about 3.19%~4.04%,the electrical resistivity of the composites increases monotonically upon compressive strain,and piezoresistivity tends to be negative.This effect is much stronger than that of positive piezoresistivity.It is proposed that the occurrence of these phenomena is attributable to both the tunneling effect between fibers and decreasing in pore network connectivity during compression.
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