No abstract

Although indentation experiments have long been used to measure the hardness and Young's modulus, the utility of this technique in analyzing the complete elasticplastic response of materials under contact loading has only been realized in the past few years-mostly due to recent advances in testing equipment and analysis protocols. This paper provides a timely review of the recent progress made in this respect in extracting meaningful indentation stress-strain curves from the raw datasets measured in instrumented spherical nanoindentation experiments. These indentation stress-strain curves have produced highly reliable estimates of the indentation modulus and the indentation yield strength in the sample, as well as certain aspects of their post-yield

We report on the mechanical behavior of a dense brush of small-diameter (1-3 nm) noncatalytic multiwall (2-4 walls) carbon nanotubes (CNTs), with ~10 times higher density than CNT brushes produced by other methods. Under compression with spherical indenters of different radii, these highly dense CNT brushes exhibit a higher modulus (~17-20 GPa) and orders of magnitude higher resistance to buckling than vapor phase deposited CNT brushes or carbon walls. We also demonstrate the viscoelastic behavior, caused by the increased influence of the van der Waals' forces in these highly dense CNT brushes, showing their promise for energy-absorbing coatings.