Experimental test of a frictional contact model for shear thickening in concentrated colloidal suspensions

Abstract

Rheological experiments on model and industrial colloidal dispersions that exhibit reversible shear thickening are compared to a recent model that correlates simulation results for the shear rheology of bidisperse suspensions of particles with varying levels of contact friction. Comparisons are presented with rheological results for a variety of colloidal dispersions varying from model systems to industrially relevant, commercial dispersions where both shear and first normal stress differences are available. Particle-scale measurements of particle friction coefficients are provided through a survey of the literature. The comparisons show under which conditions the model can quantitatively describe the measured rheology and how the model can be used to correlate data for systems with more complex interactions when allowances are made for effective volume fractions and adjustments in friction coefficients. Discrepancies evident in comparisons for the first normal stress differences highlight the importance of enhanced hydrodynamic friction in many systems, especially for continuous shear thickening, in qualitative agreement with recent simulations that incorporate enhanced lubrication hydrodynamics due to elastohydrodynamics or particle roughness. Finally, a literature survey of measurements of jamming volume fractions and particle friction coefficients indicates that the model overestimates the experimentally observed jamming volume fraction. The comparisons presented in this work provide quantitative information valuable for those modeling suspension processing as well as suggestions for further model improvement.