Glass transitions and shear thickening suspension rheology

TL;DR

This paper introduces schematic mode coupling theory models to describe shear thickening and jamming in colloidal suspensions, predicting various rheological behaviors including discontinuous shear thickening and stress-induced jamming.

Contribution

It develops a simplified MCT-based model capturing shear thickening and jamming, highlighting a stress-induced glass transition distinct from traditional hydrodynamic mechanisms.

Findings

Predicts S-shaped flow curves indicating discontinuous shear thickening

Shows stress-induced transition from fluid to jammed state with zero flow

Aligns qualitatively with experimental observations on dense colloids near the glass transition

Abstract

We introduce a class of simple models for shear thickening and/ or `jamming' in colloidal suspensions. These are based on schematic mode coupling theory (MCT) of the glass transition, having a memory term that depends on a density variable, and on both the shear stress and the shear rate. (Tensorial aspects of the rheology, such as normal stresses, are ignored for simplicity.) We calculate steady-state flow curves and correlation functions. Depending on model parameters, we find a range of rheological behaviours, including `S-shaped' flow curves, indicating discontinuous shear thickening, and stress-induced transitions from a fluid to a nonergodic (jammed) state, showing zero flow rate in an interval of applied stress. The shear thickening and jamming scenarios that we explore appear broadly consistent with experiments on dense colloids close to the glass transition, despite the fact that we ignore hydrodynamic interactions. In particular, the jamming transition we propose is conceptually quite different from various hydrodynamic mechanisms of shear thickening in the literature, although the latter might remain pertinent at lower colloid densities. Our jammed state is a stress-induced glass, but its nonergodicity transitions have an analytical structure distinct from that of the conventional MCT glass transition.