An anisotropic constitutive model for fiber reinforced salt-sensitive hydrogels

In this work, an anisotropic constitutive model for equilibrium swelling of cellulose-reinforced salt-sensitive hydrogels is proposed and its capability is verified using the experimental data. This model is able to predict the swelling behavior of salt-sensitive hydrogels reinforced with fibers in different types of orientation such as perfectly aligned, uniform in-plane, and uniform volumetric. The model is implemented numerically in the finite element method framework. Several related parameters i.e., swelling ratio, principal stretches, true concentration of counter-ion and co-ion, and salt concentration are investigated both analytically and through finite element method (FEM). Good agreement between the analytical and numerical results indicates that the model can be used for simulating more complex structures including multi-layer strips and sheets. The results show that adding cellulose fibers to the hydrogel’s medium leads to a significant enhancement in the strength of the material while preserving the inherent flexibility of the hydrogel.