Rate dependent piezoresistive characterization of smart aerospace sandwich structures embedded with reduced graphene oxide (rGO) coated fabric sensors

In this study, the piezoresistive performance of smart aerospace sandwich structures was investigated by conducting three-point bending tests at variable loading rates (0.2, 2.0, and 20 mm/min). A reduced graphene oxide (rGO) coated glass fabric piezoresistive sensor was embedded in the facesheet of a sandwich structure. An integrated framework was designed to measure piezoresistive performance of the sandwich structure i.e. from fabrication of facesheets to electromechanical testing. The three-point bending tests performed on beams consisting of the coated fabric sensors with several different geometries (variable beam widths and core thicknesses) showed that the piezoresistivity of the fabric sensors was inversely proportional to the loading rate. Moreover, the study showed that the rate dependency was prominent in beams with larger widths having maximum percent decrease of 43% in the piezoresistivity (core thickness of 3 mm) with increasing the loading rate. However, the normalized piezoresistivity with width of the beam was found to be consistent for different widths, showing good application of the fabric sensor with any arbitrary width of interest. Furthermore, the piezoresistivity rate dependency was more prevalent in the non-linear region with a maximum of 68% decrease in piezoresistivity as compared to 42% found for the elastic region (width 75 mm, thickness 5 mm).