Research On Impedance Relaxation Of Viscoelastic Pressure-Sensitive Component

Conductive polymer composites have good flexibility and pressure-impedance sensitivity. Flexible pressure sensor can be used in a narrow surface layer between the complex machinery. Applications in the aerospace, defense and other areas are particularly important. Since the composite material is affected by the base material, it has viscoelasticity and time-dependence. It deteriorates sensor performance seriously. Therefore, it is necessary to study quantitatively this material time-dependence of the stress-impedance effect. It could get its stress relaxation feature through measuring impedance relaxation of composite. The impact of stress relaxation was eliminated without affecting the flexibility of sensor. Therefore, the research has important significance.In this thesis, a method of impedance-stress conversion was designed. It can realize stress relaxation monitoring through the impedance relaxation of composite. The main contents include:(1) Flexible pressure-sensitive component was made with multi-walled carbon nanotubes for conducting filler, silicone rubber for matrix materials, by using co-solution method, assisting with ultrasonic wave and stirring dispersion treatment. The "sandwich" type composite was designed and prepared, which were made by using silicone rubber specimens filled with carbon nanotubes (Carbon nanotubes and silicone rubber mass ratio: 0.08:1,0.12:1 and 0.16:1);(2) Stress relaxation experiment platform was built (loading stress 0.1 MPa～0.4MPa, loading speed 0.1mm/min～10mm/min). In the test, the data of impedance, stress, strain with time-varying should be acquired;(3) The relationship of impedance-stress-strain-time was quantitatively researched in the loading process and the relaxation process. Furthermore, the effects of the above characteristics of the relationship of the ratio of carbon nanotubes and silicon rubber, the initial stress relaxation, the loading speed would be researched;(4) Fitting function of composites impedance was established based on the variation of impedance and stress relaxation. Conductive mechanism of composites was preliminarily analyzed. The conversion method was designed to achieve stress monitoring and the relative error is less than 15%(Monitoring range:0.1MPa～0.4MPa).This research results provide the theoretical foundation and experimental basis for the conductivity, and impedance-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.