Torsional response and stiffening of individual multi-walled carbon nanotubes

TL;DR

This study characterizes the torsional response of multi-walled carbon nanotubes, revealing their torsional spring constants, shear moduli, and evidence of stiffening due to repeated flexing, advancing understanding of their mechanical properties.

Contribution

It provides experimental measurements of torsional spring constants and shear moduli of multi-walled carbon nanotubes, highlighting their stiffening behavior under repeated flexing.

Findings

Effective shear moduli vary broadly, with some near theoretical predictions.

Nanotubes exhibit stiffening behavior after repeated flexing.

Torsional spring constants are successfully measured using atomic-force-microscope techniques.

Abstract

We report on the characterization of torsional oscillators which use multi-walled carbon nanotubes as the spring elements. Through atomic-force-microscope force-distance measurements we are able to apply torsional strains to the nanotubes and measure their torsional spring constants and effective shear moduli. We find that the effective shear moduli cover a broad range, with the largest values near the theoretically predicted value. The data also suggest that the nanotubes are stiffened by repeated flexing.