Rheological Signature of Frictional Interactions in Shear Thickening Suspensions

John R. Royer, Daniel L. Blair, Steven D. Hudson

Research output: Contribution to journalArticlepeer-review

Abstract

Colloidal shear thickening presents a significant challenge because the macroscopic rheology becomes increasingly controlled by the microscopic details of short ranged particle interactions in the shear thickening regime. Our measurements here of the first normal stress difference over a wide range of particle volume fractions elucidate the relative contributions from hydrodynamic lubrication and frictional contact forces, which have been debated. At moderate volume fractions we find N< 0, consistent with hydrodynamic models; however, at higher volume fractions and shear stresses these models break down and we instead observe dilation (N1 > 0), indicating frictional contact networks. Remarkably, there is no signature of this transition in the viscosity; instead, this change in the sign of Noccurs while the shear thickening remains continuous. These results suggest a scenario where shear thickening is driven primarily by the formation of frictional contacts, with hydrodynamic forces playing a supporting role at lower concentrations. Motivated by this picture, we introduce a simple model that combines these frictional and hydrodynamic contributions and accurately fits the measured viscosity over a wide range of particle volume fractions and shear stress.
Original languageEnglish
Article number188301
Number of pages5
JournalPhysical Review Letters
Volume116
Issue number18
Early online date5 May 2016
DOIs
Publication statusPublished - 6 May 2016

Keywords

  • colloids
  • Rheology
  • shear thickening

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