Reproducibility and embedding effects on static performace of 3D printed strain gauges

The recent advantages of Additive Manufacturing technology are raising the possibility to co-print different materials and built-in strain sensors directly into 3D printed structures. While geometry, build-orientation, and printing parameters have been widely studied, repeatability, stability, embedding effects, and reproducibility of 3D-printed strain gauge have not yet been investigated, exhaustively. The research was focused on the assessment of the inter-day variation of static performance of conductive PLA (Polylactic Acid) strain sensors with different embedded designs. A four-point bending test was conducted through a dedicated test machine. Two designs were tested twice both under tensile and compressive loads. In the first design, the sensing gauge was superficially embedded over the non-conductive structure. While in the second design, the sensing filament was completely embedded into the base structure. Initial resistance value, hysteresis, and linearity errors as well as stability were analyzed. Lower linearity error was observed in the embedded gauge design, while good stability was reported considering both the hysteresis and linearity errors and the initial resistance value. The promising results promote future investigation on the inter-day stability of 3D-printed strain gauges and favor the applications in smart structures with embedded sensory elements over time.