Testing a shear-thickening fumed silica suspension with parallel superposition rheology

Abstract:

Shear thickening (ST) behavior shown by particle suspensions has been justified using a variety of mechanisms. Order-disorder transition, hydroclusters formation, grain inertia, or frictional jamming being the most representative. However, which one is the mechanism explaining the ST behavior and the evolution of the ST microstructure with shear of a specific material? ST mechanisms are usually requested to describe the onset of the ST behavior, but the evolution of the ST microstructure with shear has not been accurately tested. Superposition rheometry (SR) is a technique that could allow us to tackle this issue. It combines continuous and oscillatory shear. Therefore, the microstructure developed by the application of a continuous shear could be directly tested by the additional application of an oscillatory shear test. There are two different ways for the application of SR, parallel and perpendicular SR. In this work, small amplitude oscillatory shear (SAOS) has been superimposed in parallel to continuous shear with the objective to determine the evolution of the ST microstructure developed in a fumed silica suspension. Due to coupling effects, parallel SR results must be cautiously used from a quantitative point of view. Fortunately, qualitative analysis of the results is enough for the purpose of this research. The overall conclusion is that few and big hydroclusters built at the onset of the ST behavior, evolve towards many and small hydroclusters with increasing shear.

Año de publicación:

2022

Keywords:

• Fumed silica suspension
• Hydroclusters
• Parallel rheometry
• Shear-thickening

Fuente:

scopus