Signature of jamming under steady shear in dense particulate suspensions

TL;DR

This study investigates the shear-thickening and shear jamming behaviors in dense particulate suspensions, demonstrating how flow-induced failures weaken the solid-like state and proposing a rheology-based method to predict shear jamming onset.

Contribution

It introduces a rheology-based approach to predict shear jamming onset in dense suspensions, supported by experimental data and optical imaging, expanding understanding of DST and SJ phenomena.

Findings

Krieger-Dougherty relation describes viscosity at low shear stress.

Deviations at high shear stress indicate flow-induced weakening of shear jamming.

Proposed method predicts shear jamming onset from steady-state rheology.

Abstract

Under an increasing applied shear stress ($\sigma$), viscosity of many dense particulate suspensions increases drastically beyond a stress onset ($\sigma_0$), a phenomenon known as discontinuous shear-thickening (DST). Recent studies point out that some suspensions can transform into a stress induced solid-like shear jammed (SJ) state at high particle volume fraction ($\phi$). 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 $\sigma$ values the viscosity of the suspensions as a function of $\phi$ can be well described by Krieger-Dougherty (KD) relation. However, for higher values of $\sigma$ ($>> \sigma_0$), KD relation systematically overestimates the measured viscosity, particularly for higher $\phi$ 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.