Preparation And Performance Study Of Thick-film Resistive Strain Sensor On Different Substrate

This research aims to take advantage of the high sensitivity, stability and lowtemperature coefficient of resistance?TCR? of thick film resistors?TFRs? to developa strain sensor for structural health monitoring in civil engineering.Compared to other conductive composites, the most important feature ofthick film resistors is the good durability, it is very suitable for long-term monitoring.Thick-film resistors were printed and fired on natural stones, stainless-steel and aluminasubstrates in this research.Natural stone and stainless steel have a lower modulus ofelasticity than alumina, the steel also has a higher mechanical (flexural) strength and anintrinsic robustness. The main contents include:(1)By screening a variety kinds of stone and metal, gabbro and sandstone wereselected as the stone substate.201,304and430stainless steel were selected as the metalsubstrate.Mineral composition of gabbro and sandstone were analyzed. After theignition?the elastic modulus of both two stone substrate were close to concrete.(2)Thick film strain sensors on different substrates were produced by the screenprinting method. Surfaces and interfaces of thick film resistors on different substratewere studied by ultra-depth microscopy and SEM. Thick film resistor on gabbrosubstrate generate large amounts of microcracks. The main factors affecting the qualityof the thick-film resistor was the compatibility of linear expansion coefficient betweenthe paste and the substrate.(3)The gauge factor, resistance stability and multi-week cyclic loading performance ofTFRs on different substrates were tested. The performance of thick film resistors onceramic substrate is most stable. The types of substrate had no significant effect on thevalue of gauge factor. Using stainless steel as substrate can significantly improve theultimate strain rate of thick film resistive sensor. Appropriate surface oxidation of the201stainless steel improved the binding properties between the dielectric layer andsubstrate. The microcrack of resistor layer on gabbro substrate enables the gaugefactor of the sensor increased dramatically (reach512), but due to the randomness of themicrocrack, the gauge factor is not a fixed value. The gauge factor of embedded TFRson gravel substrate reached11.76, The gauge factor of embedded TFRson ceramic substrate dropped to0.5027. (4)The influence of temperature and humidity on thick film resistors were tested.The TCR of TFRS on201stainless steelsubstrate and gabbro substrate were negative?others were positive. The resistance of thick film resistor remain stable when therelative humidity below60%. Once the relative humidity exceed60%, resistance ofthick film resistor decreased with the increases of relative humidity.