Shell Buckling of Imperfect Multiwalled Carbon Nanotubes—Experiments and Analysis

Experiments were conducted in which multiwalled carbon nanotubes were subjected to uniaxial compression and shell-buckling loads were measured. A comparison with existing theoretical models shows that the predictions are about 40–50% smaller than the experimentally measured buckling loads. This is in contrast to the classical elastic shell studies in which the experimental values were always substantially lower than the predicted values due to imperfection sensitivity. It is proposed that the discrepancy between the predicted and measured value might be due to imperfections in the multiwalled nanotubes in the form of sp ³ bonds between the tube walls, which introduce shear coupling between them. An analytical model is presented to estimate the effect of the shear coupling on the critical buckling strain, which shows that the contribution from shear coupling increases linearly with the effective shear modulus between the walls. Further, this contribution increases with the number of walls; the increment from each additional wall progressively decreases.