Deformation Behavior of Fiber-Reinforced Hydrogel Structures

Proposed herein is a new theory for the anisotropic deformation of fiber-reinforced hydrogels. This new model takes into account the real fabrication of the fiber-reinforced hydrogels, in which the hydrogels are polymerized with fibers and polymer solutions. The new free energy function is established by adding the anisotropic free energy component contributed by fibers into the Flory-Rehner model. The proposed model is implemented through a user-defined material subroutine (UMAT) in the finite element software package ABAQUS. In particular, the consistent tangent modulus is derived in detail. Then, several illustrative examples with analytical and numerical results are demonstrated. In order to study deformation behavior of natural materials, we design some simple bilayer structures to mimic the opening of seedpods and the closure of flowers, in which the buckling behavior of fiber-reinforced hydrogels have been demonstrated. We hope that the proposed approach may help to study more complex deformation phenomena in hydrogel structures.