Abstract
There is a growing consensus that shear thickening of concentrated dispersions is driven by the formation of stress-induced frictional contacts. The Wyart-Cates (WC) model of this phenomenon, in which the microphysics of the contacts enters solely via the fraction f of contacts that are frictional, can successfully fit flow curves for suspensions of weakly polydisperse spheres. However, its validity for "real-life", polydisperse suspensions has yet to be seriously tested. By performing systematic simulations on bidisperse mixtures of spheres, we show that the WC model applies only in the monodisperse limit and fails when substantial bidispersity is introduced. We trace the failure of the model to its inability to distinguish large-large, large-small and small-small frictional contacts. By fitting our data using a polydisperse analogue of f that depends separately on the fraction of each of these contact types, we show that the WC picture of shear thickening is incomplete. Systematic experiments on model shear-Thickening suspensions corroborate our findings, but highlight important challenges in rigorously testing the WC model with real systems. Our results prompt new questions about the microphysics of thickening for both monodisperse and polydisperse systems.
| Original language | English |
|---|---|
| Pages (from-to) | 229-237 |
| Number of pages | 9 |
| Journal | Soft Matter |
| Volume | 16 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 2019 |
Bibliographical note
Funding Information:BMG and MH were funded by EPSRC EP/J007404/1. CJN was funded by EPSRC EP/N025318/1 and the Maudslay-Butler Research Fellowship at Pembroke College, Cambridge. LJS was funded by EPSRC SOFI CDT (EP/L015536/1). JS was funded by EPSRC EP/N025318/1 and The Royal Academy of Engineering/The Leverhulme Trust Senior Research Fellowship LTSRF1617/13/2. WCKP was funded by EPSRC EP/J007404/1 and EP/N025318/1. We thank Andrew Schofield for synthesising the particles, and John Royer, Dan Hodgson and an anonymous referee for helpful discussions. The simulation makes use of the LF-DEM code published in Mari et al.9 and available at https://bitbucket.org/rmari/lf_dem as well as LAMMPS.41
Publisher Copyright:
This journal is © The Royal Society of Chemistry.
Funding
BMG and MH were funded by EPSRC EP/J007404/1. CJN was funded by EPSRC EP/N025318/1 and the Maudslay-Butler Research Fellowship at Pembroke College, Cambridge. LJS was funded by EPSRC SOFI CDT (EP/L015536/1). JS was funded by EPSRC EP/N025318/1 and The Royal Academy of Engineering/The Leverhulme Trust Senior Research Fellowship LTSRF1617/13/2. WCKP was funded by EPSRC EP/J007404/1 and EP/N025318/1. We thank Andrew Schofield for synthesising the particles, and John Royer, Dan Hodgson and an anonymous referee for helpful discussions. The simulation makes use of the LF-DEM code published in Mari et al.9 and available at https://bitbucket.org/rmari/lf_dem as well as LAMMPS.41