Electromechanical properties of carbon-nanostructured elastomeric composites measured by digital image correlation

Abstract Tensile mechanical and piezoresistive properties of elastomeric (thermoplastic polyurethane) nanocomposites in film form, made of multiwall carbon nanotubes, multilayer graphene sheets and hybrid combinations of both are investigated using digital image correlation (DIC) for strain measurement. For the hybrid materials, the mechanical and piezoresistive responses are dominated by the carbon nanotube network. Comparison between strain measurement conducted using DIC and the crosshead displacement (CHD) of the universal testing machine, indicate that the error in the piezoresistive gage factor (sensitivity) incurred by the use of CHD is proportional to that of the elastic modulus, and it can be as large as 40% for these films. This error incurred when using CHD, could be largely suppressed by proper calibration of the length of the gage section of the tensile coupons, and such a calibration can be conducted based on the average strain fields and elastic modulus measured by DIC.