Stiffness, Energy Dissipation, and Hyperelasticity in Hierarchical Multilayer Composite Nanocoated Open-Cell Polyurethane Foams

The manufacturing, testing, and modeling of a class of open-cell polyurethane (PU) foams doped with multiwalled carbon nanotubes (MWCNTs) and nano-PU dispersions (PUDs) and subjected to quasistatic cycling compressive loading at large deformations are described. The doped nanoink foams are produced using a multiple-step dip coating technique that makes the development of nano-based porous materials by postprocessing existing off-the-shelf open-cell foams possible. Tests are conducted up to 18.5% of compressive strain to identify loading/unloading moduli and energy absorbed after five cycles of stabilization. Hyperelastic Ogden models also considering the Mullins effect for cyclic loading are used to identify the constitutive parameters for these foams. The results show that the use of MWCNT layers provides an effective increase in the stiffness and energy absorbed compared with pristine and nano-PUDs-treated foams. The volume average energy absorbed after the stabilization cycles is increased by 200% compared with the pristine foam when the MWCNT layers are used. The parameters of the constitutive models extracted from the tests show that these nanoink foams are modeled following state-of-the-art hyperelastic representations.