Enhanced energy dissipation in periodic epoxy nanoframes.

Periodic nanostructures fabricated by interference lithography can be precisely designed to have a specific cell geometry, topology, and porosity in contrast to typical stochastic cellular materials. We use nanoindentation to elucidate the mechanical characteristics of the nanoframe as a function of its relative density and model the deformation behavior via numerical simulations. The nanoframe exhibits a scaling exponent of relative modulus versus relative density of 1.26, which is less sensitive than for conventional foams. Moreover, the nanoframe shows large mechanical energy dissipation/volume (up to 4.5 MJ/m(3)), comparable to the highest values achieved in the conventional polymer foams but at a far smaller strain. Counterintuitively, a nanoframe of smaller relative density can dissipate more energy per volume because the geometry of the nanoframe evolves during deformation to engage more of the material in plastic deformation. The results demonstrate how geometrical control at the nano- and microstructural scale can tailor modulus and energy dissipation and suggest means for engineering of mechanically superior materials in the future.