Modeling of carbon nanotube clamping in tensile tests

In this paper, the stress distributions in carbon nanotube clamps such as those formed by the electron beam induced deposition (EBID) technique are analyzed and the contributing factors, including nanotube position, stiffness of clamp material, and thickness of the clamping pad between the AFM tip and the nanotube are examined for the case of tensile loading of the nanotube. The nanotube is modeled at the atomistic scale by the molecular structural mechanics approach and is assumed to be defect free. The clamp material is analyzed by the continuum finite element method. The nanotube and the clamp are assumed to be bonded perfectly to each other. This bonding condition sets the upper limit of clamping capacity. The simulation results indicate that the location and intensity of stress concentration are sensitive to the nanotube orientation. Misaligned nanotubes are likely to break near the edge of the clamp. The clamp material with a lower stiffness (for the stiffness range studied) and a thicker clamping pad between the nanotube and the AFM tip reduce the magnitude of stress concentrations in the clamp.