Constraints effects in swollen particulate composites with hyperelastic polymer matrix of finite extensibility modeled by FEM

The class of particulate composites with cross-linked hyperelastic polymer matrix and non-deformable filler particles represents many important biopolymer and engineering materials. At application conditions, the matrix is either in the swollen state, or the swollen state is utilized for matrix characterization. In this contribution, a numerical model for simulation of equilibrium stress-strain and swelling behavior of this composite material was developed based on finite element method using COMSOL Multiphysics® software. In the constitutive equations (Gibbs energy), the elastic contribution is based on statistical-mechanical model of a network composed of freely jointed chains of finite extensibility and polymer-solvent mixing term is derived from the Flory-Huggins lattice model. A perfect adhesion of matrix-to-particle is assumed. The adhesion of matrix to stiff surface generates stress and degree-of-swelling fields in the composite. The existence of these fields determines the mechanical and swelling properties of the composite. Spatial distribution of filler particles in the composite plays an important role.