Yielding in a strongly aggregated colloidal gel. Part I: 2D simulations

Abstract

We investigate the microstructure details and the mechanical response under uniaxial compression of a strongly aggregating colloidal dispersion. The numerical simulations account for short-range interparticle attraction, normal and tangential deformation at particle contacts, sliding and rolling resistance (RR), and preparation conditions. The compression rates are small so that hydrodynamic interactions are negligible. In the absence of RR, the average coordination number varies only slightly with compaction while the variation is significant in its presence. The particle contact distribution is isotropic throughout the consolidation process, irrespective of the magnitude of the parameters. In this limit of strong aggregation, the elastic modulus is a weak function of the magnitude of attraction. It is shown that the yield strain does not change significantly during the entire consolidation process, and the value in the presence of RR is marginally higher than in its absence. However, the yield stress increases with volume fraction which is a direct consequence of the increased elastic modulus. The yield stress, both in the presence and absence of RR, scales similarly with volume fraction. The overall power law exponent of 5.7 of the yield stress in the presence of RR as a function of volume fraction is in good agreement with previous simulation results.