Paper Number
SC15 

Session
Suspensions, Colloids, and Granular Materials

Title
Two-step relaxation of shear-thickening dense suspensions

Presentation Date and Time
October 12, 2021 (Tuesday) 9:50

Track / Room
Track 5 / Ballroom 6

Authors (Click on name to view author profile)

1. Griese, Andrew (MIT)
2. Cho, Jae Hyung (Massachusetts Institute of Technology, Mechanical Engineering)
3. Peters, Ivo (University of Southampton)
4. Bischofberger, Irmgard (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Andrew Griese¹, Jae Hyung Cho¹, Ivo Peters² and Irmgard Bischofberger^1
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; ²University of Southampton, Southampton, United Kingdom

Speaker / Presenter 
Bischofberger, Irmgard

Keywords
suspensions

Text of Abstract
While the steady-state rheological properties of dense suspensions exhibiting discontinuous shear thickening (DST) have been studied extensively, the transient responses of these systems remain largely unexplored. We investigate the two-step exponential stress relaxation of shear-thickening aqueous cornstarch suspensions upon flow cessation. We reach a steady-state flow before the flow cessation by imposing a constant stress, rather than a constant shear rate, to enable access to the system at or near the critical shear rate at which DST is observed. Our experiments show that the characteristic timescale of the first relaxation step varies linearly with the apparent viscosity of the suspension in the steady state, which indicates that the system relaxes like a Maxwellian viscoelastic fluid. The characteristic timescale of the second relaxation step, in contrast, varies linearly with the reciprocal of the critical shear rate, which hints at the breakdown of the frictional contact network due to interparticle repulsions. We compare these results in stress-controlled experiments with those in rate-controlled experiments to further verify our hypotheses.