Paper Number
SC9 

Session
Suspensions, Colloids, and Granular Materials

Title
Experimental tests of frictional contact models for suspensions

Presentation Date and Time
October 21, 2019 (Monday) 2:45

Track / Room
Track 2 / Room 304

Authors (Click on name to view author profile)

1. Lee, Yu-Fan (University of Delaware, Chemical and Biomolecular Engineering)
2. Luo, Yimin (University of Delaware, Chemical and Biomolecular Engineering)
3. Hsu, Chiao-Peng (ETH Zurich, Department of Materials)
4. Brown, Scott C. (The Chemours Company)
5. Dennis, Kimberly A. (University of Delaware, Chemical and Biomolecular Engineering)
6. Isa, Lucio (ETH Zurich, Department of Materials)
7. Furst, Eric M. (University of Delaware, Chemical and Biomolecular Engineering)
8. Wagner, Norman J. (University of Delaware, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Yu-Fan Lee¹, Yimin Luo¹, Chiao-Peng Hsu², Scott C. Brown³, Kimberly A. Dennis¹, Lucio Isa², Eric M. Furst¹, and Norman J. Wagner^1
1Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716; ²Department of Materials, ETH Zurich, Zurich 8093, Switzerland; ³The Chemours Company, Wilmington, DE 19805

Speaker / Presenter 
Lee, Yu-Fan

Text of Abstract
The shear-thickening of dense colloidal suspensions is an active topic of research to understand the non-linear flow response. Efforts in theoretical models and simulations have been made to examine the essential physics thought to be controlled by nanometer scale inter-particle forces, including lubrication hydrodynamics and frictional contact forces. At high stresses and concentrations, the particles are in close enough proximity and form transient structures called hydroclusters, which manifests in shear-thickening. Recently, there has been significant effort in exploring the possible role of contact friction in shear thickening. Wyart and Cates propose an increase in fraction of frictional contact with increasing stress as the source of the shear thickening viscosity. Further work by Morris and co-workers suggest that the jamming volume fraction, where the suspension ceases to flow, depends on the friction at particle-particle contact. These authors performed simulations by varying contact friction coefficients to correlate with the jamming volume fraction. What is lacking, however, are experiments on model suspensions with known levels of contact friction where the full rheological stress tensor under shear is measured. Recent characterization of coated colloidal particles provides a reference for a system with low surface friction, while estimates of surface friction for the uncoated particles provides a reference for a suspension with higher friction. Further research of this work studies the relationship between contact friction, jamming volume fraction, and shear thickening rheology by studying model suspensions with known surface properties of systematically varying contact friction coefficients, as typically measured by particle atomic force microscopy. The shear rheology of suspensions of particles with varying surface chemistry that exhibit a variation in jamming fractions and contact friction coefficients is characterized to understand the mechanistic role of frictional contact in shear thickening.