Multiparticle finite element model of highly deformed hydrogel assemblies

Abstract: Packings of hydrogel particles, like any granular material, become rigid when volumetrically confined. At low confinement near the onset of rigidity, linear elastic contact mechanics should provide a good description of the interparticle forces. At higher confinement, the particles become strongly deformed and linear elastic contact mechanics no longer provides a reasonable description of the interparticle forces. Here, we report on simulations using a multiparticle finite element technique, employing the Flory-Rehner constitutive law, to model the full non-linear elastic deformation of all particles in the packing. We show that the shear modulus (μ) of the packing depends strongly on confining pressure (p) with a crossover from a low-pressure regime where μ ~ p^1/2 to a high-pressure strongly-faceted regime where μ ~ p^1/4 where interstitial space has essentially vanished and the facet geometry no longer evolves with pressure.