| Conductive polymer composites are a class of new functional materials with important value in theoretical research and broad application prospects. Because of its good flexibility and piezoresistive effect, it can be used in flexible pressure sensor as sensitive material. However, when silicon rubber is used as matrix of the pressure-sensitive composite materials, the matrix materials influenced the composite materials’s performance inevitably. The resistance of pressure-sensitive composite materials in constant stress(strain) appears the time dependence, which seriously affects the sensor precision. At present, the majority of solutions are adding nanometer dioxide particles such as SiO2in the material. On the one hand, it reduces the mechanical flexibility of the material. On the other hand, it only weakens the impact but not eliminates. Therefore, quantitative research on this material for the piezoresistive effect of time dependence is necessary.The flexible sensor’s monitoring the stress relaxation is a big problem. To solve this difficult problem, a calibration algorithm of stress relaxation monitoring is designed based on the research on piezoresistive time-varying characteristic of conductive polymer composites. It can be used to monitor the stress relaxation among the narrow surface layers of the large equipment in the national defense and industry. Besides, the key technology can also be used in some fields such as artificial electronic skin development.The five main contents of this article are as follows:(1)Preparating the sample of conductive silicone rubber filled carbon nanotubes macromolecule composite material, and obtaining the resistance, stress and strain data which is changed with time during compression stress relaxation.(2)Based on the analysis of the relaxation experiment results, the thesis finds the characteristics of resistance-stress-strain-time during loading process and constant strain process. Besides, the effects of the carbon nanotubes concentration, load speed and initial stress on the resistance relaxation experiment are analyzed.(3)Through the research of piezoresistive time-varying characteristic of conductive polymer composites, the thesis designs the approximation formula which describes the relationship between resistance relaxation and stress relaxation in the process of compress stress relaxation of the composite. It has high plot precision and promotes further study. Besides, it reveals the rules how concentration, rate and initial stress influence the key parameter of the approximation formula.(4)Based on research of the conductive polymer composite pressure resistance, the thesis designes a calibration algorithm of the stress relaxation based on the piezoresistive properties and time dependence of composite materials.(5)The thesis makes preliminary qualitative research on the relationship between composite material internal structure and the macroscopic electric properties during compression stress relaxation. Besides, the thesis analyses the effect of concentration and strain rate of the carbon nanotubes on the number of conductive destruction and restruction channels.This research results provide the theoretical foundation and experimental basis for the conductivity and resistance time dependence of pressure-sensitive composite materials, and provide technical foundation to develop the flexible pressure sensor based on conductive polymer composites which is used to test stress relaxation. |
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