3D-Printed Strain Gauges Based on Conductive Filament for Experimental Stress Analysis

We present a method for manufacturing 3D-printed strain gauges by means of fused filament fabrication that are suitable for experimental stress analysis applications. The 3D-printed strain gauge (SG) is based on a multilayer structure, which is similar to the design of conventional metal foil SGs. This involves printing a meander-shaped measuring grid layer consisting of a conductive compound filament on a layer of non-conductive PLA that serves as a substrate. In order to evaluate the strain sensing behavior of the 3D-printed SG, it is bonded onto a steel plate by means of a cold curing superglue that undergoes a bending load of 30 N. Here, a finite element analysis is conducted for determining a proper position that ensures a high strain while not exceeding the yield strength. Our results show a reproducible behavior of the change in resistance of the 3D-printed SG in response to the bending load. Despite an existing creep that is based on the polymer properties of the filament, a linear behavior of the change in resistance linearity error of ±4 % is present. Furthermore, the sensitivity of the 3D-printed SG is four times higher than that of conventional metal foil strain gauges. Thus, these results confirm that the 3D-printed SG is a cost-effective alternative for strain sensing applications.