Constitutive Formulation of the Mechanical Properties of Synthetic Hydrogels

Abstract

This study attempts to define a universal description of the constitutive formulation of mechanical properties of synthetic hydrogels that can be manufactured as load-bearing structures to replace diseased or damaged soft tissues. While the strain energy density function (SEF) describing the elastic properties of a soft tissue generally depends on two invariants, we propose a SEF that depends on only the first strain invariant. This allows quantifying the SEF from data of a uniaxial extension test. The single invariant SEF was used to predict the mechanical response of a thick-walled tube inflated by an internal pressure. The results show excellent concordance with recorded experimental data, indicating that the mechanical properties of elastic hydrogels can be accurately represented by a SEF that is an exponential function of the first strain invariant with two material constants.