Signature of jamming under steady shear in dense particulate suspensions

Abstract

Under an increasing applied shear stress (), the viscosity of many dense particulate suspensions increases drastically beyond a stress onset (), a phenomenon known as discontinuous shear-thickening. Recent studies point out that some suspensions can transform into a stress induced solid-like shear jammed (SJ) state at high particle volume fraction (). SJ state develops a finite yield stress and hence is distinct from a shear-thickened state. Here, we study the steady state shear-thickening behaviour of dense suspensions formed by dispersing colloidal polystyrene particles (PS) in polyethylene glycol (PEG). We find that for small values the viscosity of the suspensions as a function of can be well described by Krieger–Dougherty (KD) relation. However, for higher values of (), KD relation systematically overestimates the measured viscosity, particularly for higher values. This systematic deviation can be rationalized by the weakening of the sample due to flow induced failures of the solid-like SJ state. Using Wyart–Cates model, we propose a method to predict the SJ onset from the steady state rheology measurements. Our results are further supported by in situ optical imaging of the sample boundary under shear.