Mechanical behavior of a carbon nanotube turf

Carbon nanotubes grown on a substrate form a turf – a complex structure of intertwined nanotubes cross-linked by adhesive contact. We analyze the physical mechanism of deformation on the basis of: (i) standard and continuous stiffness nanoindentation; and (ii) micromechanical scaling analysis. At moderate strains, deformation is fully reversible, comprising small viscoelastic relaxation caused by the thermally activated sliding of contacts. The pre-existing strain energy of bent nanotubes produces a high initial tangent modulus, followed by an order of magnitude decrease in the tangent modulus.