Yield stress and elastic modulus of suspensions of noncolloidal particles in yield stress fluids

TL;DR

This study experimentally investigates how noncolloidal particles affect the yield stress and elastic modulus of suspensions in yield stress fluids, establishing universal relationships independent of material specifics.

Contribution

It develops procedures to isolate mechanical effects and relates suspension properties to particle concentration and fluid mechanics, applicable across various materials.

Findings

Elastic modulus follows Krieger-Dougherty law with concentration.

Yield stress relates to elastic modulus through a simple law.

Results are consistent with micromechanical analysis.

Abstract

We study experimentally the behavior of isotropic suspensions of noncolloidal particles in yield stress fluids. This problem has been poorly studied in the literature, and only on specific materials. In this paper, we manage to develop procedures and materials that allow us to focus on the purely mechanical contribution of the particles to the yield stress fluid behavior, independently of the physicochemical properties of the materials. This allows us to relate the macroscopic properties of these suspensions to the mechanical properties of the yield stress fluid and the particle volume fraction, and to provide results applicable to any noncolloidal particle in any yield stress fluid. We find that the elastic modulus-concentration relationship follows a Krieger-Dougherty law, and we show that the yield stress-concentration relationship is related to the elastic modulus-concentration relationship through a very simple law, in agreement with results from a micromechanical analysis.