Static and dynamic mechanical properties of polyurea nanocomposites reinforced by polydopamine functionalized graphene oxide

Polyurea (PU) materials are widely used in civil and military fields owing to their excellent weather, wear and corrosion resistance, impact resistance and energy absorption ability. In this study, polyurea nanocomposites integrated with polydopamine functionalized graphene oxide (GO@PDA) were reported. The functionalization of graphene oxide (GO) with polydopamine was achieved under mild conditions to optimize the dispersion and interfacial compatibility of GO within the PU matrix, thereby reinforcing the mechanical properties of PU materials. The quasi-static and dynamic compressive behaviors of PU nanocomposites under various strain rates (0.001-7000 s-1) were comprehensively investigated through a universal testing machine and split Hopkinson pressure bar (SHPB), respectively. Results revealed a significant enhancement in the strain-rate sensitivity, flow strength, yield strength, and strain energy density with the increasing strain rate and GO@PDA content. Particularly, at a strain rate of 7000 s-1, GO@PDA1.0%/PU nanocomposite exhibited a remarkable increase of 33% and 54% in flow strength and yield strength, respectively. This remarable enhancement was closely related with the effective dispersion and superior interfacial compatibility between GO@PDA and PU matrix. Eventually, to offer a comprehensive understanding of the mechanical behavior of PU nanocomposites, a visco-hyperelastic intrinsic model was employed to accurately capture the mechanical response under various strain rates.