Continuum modeling of Soft Glassy Materials under shear

TL;DR

This paper introduces a continuum fluidity model for Soft Glassy Materials that captures complex shear-induced phenomena like stress overshoot, shear banding, and boundary effects, providing a versatile framework for understanding their transient flow behaviors.

Contribution

The paper presents a spatially-resolved fluidity model incorporating non-local effects to accurately describe shear-induced yielding and complex flow phenomena in SGMs.

Findings

Quantitative agreement with observed stress overshoot behavior

Model captures shear-banding and transient fluidization times

Includes boundary effects like elasto-hydrodynamic slippage

Abstract

Soft Glassy Materials (SGM) consist in dense amorphous assemblies of colloidal particles of multiple shapes, elasticity, and interactions, which confer upon them solid-like properties at rest. They are ubiquitously encountered in modern engineering, including additive manufacturing, semi-solid flow cells, dip-coating, adhesive locomotion, where they are subjected to complex mechanical histories. Such processes often include a solid-to-liquid transition induced by large enough shear, which results in complex transient phenomena such as non-monotonic stress responses, i.e., stress overshoot, and spatially heterogeneous flows, e.g., shear-banding or brittle failure. In the present article, we propose a pedagogical introduction to a continuum model based on a spatially-resolved fluidity approach that we recently introduced to rationalize shear-induced yielding in SGMs. Our model, which relies upon non-local effects, quantitatively captures salient features associated with such complex flows, including the rate dependence of the stress overshoot, as well as transient shear-banded flows together with nontrivial scaling laws for fluidization times. This approach offers a versatile framework to account for subtle effects, such as avalanche-like phenomena, or the impact of boundary conditions, which we illustrate by including in our model the elasto-hydrodynamic slippage of soft particles compressed against solid surfaces.