Improved strain sensing capability of nano-carbon free-standing buckypapers based strain gauges

Abstract

Nano-carbons including carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) have been proved to have good strain sensing capability, but they are often made together with flexible substrates, which may limit their multifunctional applications such as internal sensors. In this study, free-standing CNT/GNP buckypapers (BPs) with various weight ratios were prepared by filtrating their suspensions. Relative resistance variation depending on tensile strain of the obtained BPs was examined to evaluate their strain sensing capability, e.g. gauge factor (GF) and linearity (r2) within the whole testing strain range. Results show that enhanced strain sensing capability of the hybrid BPs is obtained, with a maximum GF of 8.18, and r2 of 0.999, respectively, in a relatively large strain range from 0% to 2%, when the GNP loading reaches 50 wt%. Moreover, in situ strain sensing capability of the hybrid BPs was practically monitored by sticking them onto the surfaces of epoxy resin. As expected, the hybrid BPs exhibit a relatively high in situ GF of 10.83 and r2 of 0.987, as well as excellent repeatability and stability. Excellent strain sensing capability of the free-standing BPs reveal that they have potential applications in the fields of internal and external strain or damage monitoring.