Influence of boundary conditions on yielding in a soft glassy material

TL;DR

This study examines how boundary conditions influence yielding in a soft glassy material, revealing that wall slip can cause macroscopic fragmentation and fluidization, highlighting the importance of boundary effects in jammed materials.

Contribution

It demonstrates the significant impact of boundary conditions on yielding behavior and introduces the concept of a characteristic length related to cooperativity effects.

Findings

Rough walls cause shear localization in the material.

Smooth walls lead to macroscopic fragmentation and eventual fluidization.

Boundary conditions drastically alter the yielding process.

Abstract

The yielding behavior of a sheared Laponite suspension is investigated within a 1 mm gap under two different boundary conditions. No-slip conditions, ensured by using rough walls, lead to shear localization as already reported in various soft glassy materials. When apparent wall slip is allowed using a smooth geometry, the sample is shown to break up into macroscopic solid pieces that get slowly eroded by the surrounding fluidized material up to the point where the whole sample is fluid. Such a drastic effect of boundary conditions on yielding suggests the existence of some macroscopic characteristic length that could be connected to cooperativity effects in jammed materials under shear.