On the separation of carbon nanotubes

The energy density and forces required to separate nanoropes into individual nanotubes was examined by studying both the dilatation separation of arrays and the peeling of a pair of single wall carbon nanotubes. The cohesive energy per unit length was determined from the universal graphitic potential. The magnitude of the peeling force for a pair of tubes configured in a double cantilever beam was calculated over a range of peeling lengths using a cohesive zone model, and compared to predictions from linear elastic fracture mechanics. The results of the analysis reveal that a linear elastic fracture model that incorporates an inherent initial crack length yields a reasonable estimation of the peeling force–deformation response. The energy of separation for the dilatation mechanism was shown to be a strong function of the array size with twice the energy density necessary to separate an array of three CNT as compared to separation of a large array. Estimates of the energy of peeling separation of 0.30 nJ/m is in good agreement with previous work.