Paper Number
GG4
Session
Rheology of Gels, Glasses and Jammed Systems
Title
Evidence for chaotic behavior during the yielding of soft jammed matter
Presentation Date and Time
October 10, 2022 (Monday) 10:50
Track / Room
Track 3 / Sheraton 5
Authors
- Venerus, David C. (New Jersey Institute of Technology, Chemical & Materials Engineering)
- Machabeli, Otar (New Jersey Institute of Technology, Chemical & Materials Engineering)
- Bushiri, Daniela (New Jersey Institute of Technology, Chemical & Materials Engineering)
- Arzideh, Seyed Mahmoud (New Jersey Institute of Technology, Chemical & Materials Engineering)
Author and Affiliation Lines
David C. Venerus, Otar Machabeli, Daniela Bushiri and Seyed Mahmoud Arzideh
Chemical & Materials Engineering, New Jersey Institute of Technology, Newark, NJ 07102
Speaker / Presenter
Venerus, David C.
Keywords
gels; jammed systems
Text of Abstract
Soft jammed materials, which include emulsions, foams, and microgels, display complex rheological behavior that includes a yielding transition from an elastic solid to a viscous fluid. Most studies of this class of soft matter involve shear flows and only a handful report both shear and normal stresses. We present measurements of the shear stress and first and second normal stress differences for a Carbopol microgel in constant shear rate flows. Great effort has been made to eliminate experimental artifacts in these measurements, including one that appears to have previously been overlooked. The shear stress evolves through the yield point in a manner indicative of simple yield-stress fluid behavior. Prior to yielding, the normal stress differences are immeasurably small; beyond the yield point, they evolve in a reproducibly chaotic manner. Our results appear to be the first where the complete state of stress for a soft jammed material is measured prior to, at, and beyond the yield point, and have implications for the von Mises yielding criterion. These results further suggest that the designation of yield stress fluids as ‘simple’ based solely on shear stress behavior may be inadequate.