Stiffness, energy dissipation and hyperelasticity in hierarchical multilayer composite nanocoated open cell polyurethane foams

The paper describes the manufacturing, testing and modelling of a class of open cell polyurethane foams doped with multi-walled carbon nanotubes and nano polyurethane dispersions and subjected to quasi-static cycling compressive loading at large deformations. The doped nano-ink foams are
produced using a multiple steps dip coating technique that makes possible the development of nanobased porous materials by post-processing existing off-the-shelf open cell foams. Tests are carried out up to 18.5% of compressive strain to identify loading/unloading moduli and energy absorbed
after 5 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 the multi-walled carbon nanotube layers provide an effective increase of the stiffness and
energy absorbed compared to pristine and nano polyurethane dispersions-treated foams. The volume average energy absorbed after the stabilization cycles is increased by 200% compared to the
pristine foam when the multi-walled carbon nanotube layers are used. The parameters of the constitutive models extracted from the tests show that these nano-ink foams can be modelled following state-of-the-art hyperelastic representations