Paper Number
RS6
Session
Techniques and Methods: Rheometry & Spectroscopy/Microscopy
Title
Experimentally decomposing MAOS responses into recoverable and unrecoverable components unifies physical interpretations of nonlinear material functions
Presentation Date and Time
October 11, 2022 (Tuesday) 11:30
Track / Room
Track 6 / Mayfair
Authors
- Shim, Yul Hui (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Singh, Piyush K. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Yul Hui Shim, Piyush K. Singh and Simon A. Rogers
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Shim, Yul Hui
Keywords
experimental methods; polymer solutions
Text of Abstract
Dynamic oscillatory shear testing has been widely used to characterize viscoelastic responses of soft materials and is often divided into small-, medium-, and large-amplitude regimes (SAOS, MAOS, and LAOS). While SAOS is a commonly performed test with accepted analysis and interpretation, understanding MAOS and LAOS is still an active area of research. While numerous mathematical formalisms have been proposed, a consensus is still missing. Recent advances in our understanding of the nonlinear behavior in the LAOS regime have been made using iterative recovery tests. Recovery rheology decomposes the strain into two parts, allowing a clear interpretation of the nonlinear behavior in terms of sequences of recoverable and unrecoverable processes. In this study, we use recovery rheology to the study the MAOS response of a PVA / Borax putty and worm-like micelles. In addition to a storage modulus that is proportional to energy stored elastically, recovery rheology includes two contributions to the loss modulus associated with the rates at which strain is acquired recoverably and unrecoverably. We show that two mathematical formalisms, the Chebyshev and sequence of physical processes analyses, provide competing interpretations when they are calculated in terms of the total strain but give the same interpretations of the elastic and two viscous properties when calculated in terms of the decomposed strains. We therefore show that what has often been treated as a mathematical problem can instead be solved experimentally by including the extra information provided by recovery rheology.