ABSTRACT
This chapter deals with constitutive modeling of the viscoplastic response of nanocomposite hydrogels under an arbitrary deformation with finite strains. Hydrogels are three-dimensional networks of polymer chains connected by physical and chemical cross-links. Mechanical properties of hydrogels have been a focus of attention in the past decade as these materials demonstrate potential for a wide range of applications including biomedical devices, drug delivery carriers, superabsorbent materials, filters and membranes for selective diffusion, sensors for on-line process monitoring, smart optical systems, and soft actuators. Macro-deformation of a nanocomposite hydrogel coincides with that of the equivalent medium. A constitutive model is developed in finite viscoplasticity of nanocomposite hydrogels under an arbitrary deformation with finite strains. Constitutive equations are derived by means of the free-energy imbalance equation. The free energy of a nanocomposite hydrogel equals the sum of strain energy density of the solid phase and the energy of mixing of the solid phase with solvent.
