A dynamic jamming point for shear thickening suspensions

TL;DR

This paper investigates the critical behavior of shear thickening suspensions, revealing a diverging slope and viscosity at a critical packing fraction, and introduces a dynamic jamming phase diagram linking shear thickening to jamming states.

Contribution

It presents the first detailed rheometry analysis of critical behavior in shear thickening suspensions and proposes a dynamic jamming phase diagram.

Findings

Diverging slope of viscosity curve at critical packing fraction

Viscosity and yield stress diverge at the critical point

Shear thickening transitions to shear thinning beyond the critical packing fraction

Abstract

We report on rheometry measurements to characterize critical behavior in two model shear thickening suspensions: cornstarch in water and glass spheres in oil. The slope of the shear thickening part of the viscosity curve is found to increase dramatically with packing fraction and diverge at a critical packing fraction phi_c. The magnitude of the viscosity and the yield stress are also found to have scalings that diverge at phi_c. We observe shear thickening as long as the yield stress is less than the stress at the viscosity maximum. Above this point the suspensions transition to purely shear thinning. Based on these data we present a dynamic jamming phase diagram for suspensions and show that a limiting case of shear thickening corresponds to a jammed state.