Directional shear-jamming

TL;DR

This paper investigates shear reversals in dense suspensions of elliptical particles, revealing a new directional fragility linked to particle orientation and reorientation, leading to shear-jamming in the reversed direction.

Contribution

It introduces the concept of directional fragility in shear flows of elliptical particles and links it to particle orientation and reorientation effects.

Findings

Elliptical particles exhibit shear-direction-dependent flow and jamming behavior.

Shear stress reversal causes reorientation and increased contacts, leading to shear-jamming.

This fragility is absent in isotropic particle suspensions.

Abstract

In this work we, study shear reversals of dense non-Brownian suspensions composed of cohesionless elliptical particles. By numerical simulations, we show that a new fragility appears for frictionless ellipses in the flowing states, where particles can flow indefinitely in one direction at applied shear stresses but shear-jams in the other direction upon shear stress reversal. This new fragility, absent in the isotropic particle case, is linked to the directional order of the elongated particles at steady shear and its reorientation at shear stress reversal, which forces the suspensions to pass through a more disordered state with an increased number of contacts in which it might get arrested.