Printed strain gauges embedded in organic coatings - Analysis of gauge factor and temperature dependence

In this work, we present a method for the realization of printed strain gauges on pre-coated sheet steel substrates. The state of the art is to glue strain gauges on foil onto a substrate. This, however, has inherent disadvantages in terms of force coupling between the bent substrate and the glued strain gauge sensors. The fact that the glue and the substrate have in general different moduli of elasticity affects the achievable gauge factor of the final sensor stack. The method presented in this work circumvents these problems completely by eliminating the gluing process and integrating the sensor into a cover layer on the substrate. In the considered case, the substrate is a steel sheet with an organic coating. We integrate the sensor in this coating by screen-printing it on a pre-coated layer. The results in terms of the various determined gauge factors including the influence of a top coating layer, as well as temperature dependences of the strain sensors fabricated with carbon black and silver ink are presented in this work.