Effect of carbon nanotube doping on the energy dissipation and rate dependent deformation behavior of polyurethane foams

An experimental investigation is performed to characterize the effect of carbon nanotubes on the average mechanical properties of polyurethane foams. Polyurethane foams are doped with as-grown and oxidized carbon nanotubes at varying carbon nanotube concentrations. It is observed that the inclusion of carbon nanotubes up to a threshold concentration decreases the density of freely expanding polyurethane foams. Uniaxial and cyclic compression testing of foam samples is carried out to study their energy dissipation and rate dependent deformation behavior. While energy dissipation is observed to be higher in neat polyurethane foams, carbon nanotube reinforced foams show better recovery when compressed beyond elastic limit due to their stiffer foam cell walls. It is shown that incorporation of oxidized carbon nanotubes should be preferred over as grown carbon nanotubes to improve flexural, thermal and acoustic response of polyurethane foams. Scanning electron microscopy analysis of compressed samples reveals that cell shearing; cell bending and fracture at nodes are the predominant mode of deformation in all foam samples.