Experimental Research Of Sensing Characteristic About Polymer Based Carbon Fiber Sensitive Layer

With the support of NSFC (National Natural Science Foundation of China) Funding:Sense theory and imaging of sensitive layers formed by composites for the stress monitoring of nuclear safety shell (project NO.50878169), aiming at condition monitoring of structures, we designed carbon fiber polymer-matrix sensitive layers with local overlap to monitor the deformation and damage of structures, meanwhile made exploratory theoretical analysis and experiments researching.The primary works we did are as follow:1. Taking into the different kinds of carbon fibers and disparity of length of the local overlap will impact piezoresistence of sensitive layers,therefor the specimens were fabricated with different carbon fibers and different length of local overlap. Then they were stuck on the surface of bars. The experimental discovery by voltammetry is that the electric resistance of the same specimen is small different with different currents, the greater electric resistance follows the small current.2. Through uniaxial tension and cyclic loading experiments researched the piezoresistance of the specimens, generalized the variation of resistance as the load; studying the relationship between the gauge factor and the length of the local overlap. We found that the minimum length has the maximum gauge factor; sensor stability of the sensitive layers has no significant relationship with the length of length of the local overlap, the sensor stability of all specimens is good. We explain the change of the resistance according to the resistance model of the local overlap.3. Testing the stability of the specimens when the load of uniaxial tension is constant.The curve about the change of the resistance under the constant load condition demonstrate that output values of the sensitive layers are almost steady.4. We concluded the law of the resistance's variation under the condition that the temperature is rising or keeping constant. The experimental data indicate that when the temperature is rising the resistance of the sensitive layers will rising as well, the temperature is higher the step of the increased resistance is greater, the amount of the increased resistance is proportional to the length of local overlap. When the temperature below 80℃and keep constant the stability of the resistance of the sensitive layers is well, temperature above 80℃the stability will reduce.