Abstract
In this paper, the potential of using ethylene-vinyl acetate (EVA) filled with multi-wall carbon nanotubes (MWCNT) composites for strain sensing was investigated. Stress relaxation experiments were conducted on injection-molded samples, and the stress and electrical resistance were measured in situ during the relaxation process. Based on the experimental results, it was found that the electrical resistance of the EVA/MWCNT composite increases with increasing strain, and exponentially decreases with relaxation time, indicating the capacitive behavior of MWCNTs. The maximum electrical conductivity of 7.35×10-4 S/cm was obtained for the EVA/MWCNT composite with 5 wt.% at 180°C, whereas higher piezo-resistive sensitivity was obtained for the composite with 3 wt.%. The electrical percolation threshold was found to increase from 0.223 wt.% at 140°C to 0.994 wt.% at 180°C.
Keywords: strain sensing; conductivity; stress relaxation; carbon nanotubes; polymer