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采用四电极法测量碳纳米管水泥基复合材料的电阻及循环荷载作用下电阻率的变化规律,研究环境及疲劳荷载对复合材料的电阻率及压敏性能的影响规律。主要研究了温度(20,30,40,50℃)、含水率(0%~6.4%)、温度-含水率耦合以及疲劳荷载作用对复合材料的导电性与压敏性的影响。结果表明,环境及疲劳荷载对于复合材料电阻及其压敏性具有显著的影响。复合材料的电阻率随含水率的增加而降低,当复合材料含水率从1.3%提高到5.8%,其电阻率降低46%;在荷载作用下,其电阻率变化随着含水率的增加呈现先增加后减小的趋势;随着温度的增加,复合材料电阻率降低,压敏性提高,在20℃到50℃范围内复合材料电阻率及循环荷载下电阻变化率均与温度呈良好的线性关系,相关系数均超过0.99,当温度从20℃升高到50℃,复合材料电阻率降低35%,荷载作用下电阻变化率提高84%,表明高温情况下复合材料具有更好的压敏性;在温度-含水率耦合作用下,随着含水率增加,压敏性对温度的灵敏度呈近似直线下降趋势,相关系数为0.915;复合材料的电阻率及压敏性随着疲劳次数的增加而增加。复合材料电阻及压敏性的变化主要是由隧道效应及内部微裂纹发展造成的。
The four-electrode method was used to measure the resistance of carbon nanotube-cement-based composites and the variation of resistivity under cyclic loading. The effects of environmental and fatigue loading on the resistivity and pressure-sensitive properties of the composites were studied. The effects of temperature (20,30,40,50 ℃), moisture content (0% ~ 6.4%), temperature-water content coupling and fatigue loading on the electrical conductivity and pressure sensitivity of the composites were studied. The results show that the environmental and fatigue loads have a significant effect on the resistance of composite materials and their pressure-sensitive properties. The resistivity of the composites decreases with the increase of water content. When the moisture content of the composites increases from 1.3% to 5.8%, the resistivity of the composites decreases 46%. The resistivity changes with the increase of water content Increase and then decrease; with the increase of temperature, the resistivity of the composite decreases and the pressure sensitivity increases. The resistivity of the composite and the change rate of resistance under cyclic loading show good linearity with temperature at 20 ℃ to 50 ℃ The correlation coefficient and the correlation coefficient all exceed 0.99. When the temperature rises from 20 ℃ to 50 ℃, the resistivity of the composite decreases 35% and the resistance change rate increases 84% under the load, indicating that the composite has better pressure sensitivity under high temperature Under the coupling of temperature and water content, the sensitivity of pressure sensitivity to temperature decreases linearly with the increase of water content, and the correlation coefficient is 0.915. The resistivity and pressure sensitivity of composites increase with the increase of fatigue frequency increase. The change of composite resistance and pressure sensitivity is mainly caused by the tunneling effect and the development of internal microcracks.