Strain sensing behaviors of epoxy nanocomposites with carbon nanotubes under cyclic deformation.

The strain sensing behavior of multi-walled carbon nanotubes (MWCNT)/epoxy (EP) conductive composites subjected to tensile strain was studied in detail. With increasing the load to rupture, the responsivity (ΔR/R 0 , R 0 is the original resistance, ΔR is instantaneous change in resistance) increased in a linear fashion and then began to decrease at a critical strain ( ε c ), which was remarkably different from the thermoplastic conductive composites only with a monotonic increase of the responsivity. It was attributed to the decrease of the nanotube contact points, the increase in the gaps before ε c , and the reorientation and violent alignment of nanotubes in the zones of high local deformation (after ε c ). In addition, when the extension-retraction cycles were applied, the values of max ΔR/R 0 showed a distinct tendency with different strains around the ε c . These behaviors were attributed to the competition of network destruction and reconstruction during the cyclic deformation. The mechanism of this unique sensing behavior was proposed as well. [ABSTRACT FROM AUTHOR]