Mechanics of Multi-Walled Carbon Nanotubes Under Uniaxial Compression

We report shell buckling instabilities observed experimentally in multi-walled carbon nanotubes subjected to uniaxial compression and interpret the results using insights from elasticity theory and molecular dynamics simulations. Uniform hexagonal arrays of vertically-oriented, freestanding multi-walled carbon nanotubes were grown in a self-assembled, highly-ordered nanoporous alumina matrix and then placed under uniaxial compression using a nanoindenter. Both flat and spherical nanoindenter tips were used to compress many nanotubes at once, and individual nanotube behavior could be deduced from the bulk force-vs.-displacement data by using the uniformity of the nanotube arrays and the geometry of the tips. Buckling instabilities are evident in the measured force-vs.-displacement behavior. A consideration of thin shell elasticity theory and molecular dynamics models provides guidelines for interpreting the experimental results. Excellent agreement is found between the experimentally measured critical buckling loads and those predicted by theory.