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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 piezoresistive effect of short cut carbon fiber reinforced cement-based composites (CFRC) was studied experimentally, and the whole conversion process of positive and negative piezoresistive effects was obtained. The formation mechanism of this phenomenon is discussed from the perspective of tunnel effect and pore connectivity. The results show that under continuous drying and unidirectional cyclic loading, the piezoresistive effect of CFRC changes with the change of water content. In most cases, the volume resistivity of CFRC decreases monotonously with compressive strain, and the piezoresistive effect is positive. The smaller the water content, the more obvious positive pressure hindering effect. When the water content decreases to about 3.19% ~ 4.04%, the volume resistivity of CFRC increases monotonously with the compressive strain, and the piezoresistive effect is negative. Compared with the positive piezoresistive effect, negative piezoresistive effect is stronger. The positive and negative piezoresistive effects of CFRC and their mutual conversion are the inevitable results of interaction between tunneling effect and pore connectivity.