Paper Number
PO35 

Session
Poster Session

Title
How to make medium-amplitude oscillatory shear stress (MAOStress) measurements

Presentation Date and Time
October 13, 2021 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom 1-2-3-4

Authors (Click on name to view author profile)

  1. Ramlawi, Nabil (University of Illinois at Urbana-Champaign)
  2. Hossain, Tanver (University of Illinois at Urbana-Champaign, The Department of Mechanical Science and Engineering)
  3. Shetty, Abhishek (Anton Paar USA, Rheology)
  4. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Nabil Ramlawi1, Tanver Hossain1, Abhishek Shetty2 and Randy H. Ewoldt1
1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Rheology, Anton Paar USA, Ashland, VA 23005

Speaker / Presenter 
Ramlawi, Nabil

Keywords
gels; rheology methods

Text of Abstract
We report the first-ever complete measurement of MAOStress material functions, using PVA-Borax, a transiently crosslinked polymer network, and a stress controlled rheometer having an electronically commutated (EC) motor. Moreover, we outline experimental limit lines and their dependence on geometry and test conditions. These MAOStress measurements enable us to test theoretical interrelations between MAOStress and MAOStrain material functions derived by Lennon et al.[1]. Using our previously published MAOStrain data of PVA-Borax[2], we find good agreement between the inter-relation prediction and our measurements. Similar to the benefit of linear viscoelastic interrelations, we show how this weakly-nonlinear interrelation is useful for extending experimental accessibility and providing corroborating evidence for credible MAOStress and MAOStrain, which reveal material physics beyond linear viscoelasticity but at weakly-nonlinear conditions that are accessible to theory and detailed simulation[3]. [1] K. R. Lennon, G. H. Mckinley, and J. W. Swan, “Medium amplitude parallel superposition ( MAPS ) rheology . Part 1?: Mathematical framework and theoretical examples,” J. Rheol., vol. 551, no. 64, p. 551, 2020. [2] N. A. Bharadwaj, K. S. Schweizer, and R. H. Ewoldt, “A strain stiffening theory for transient polymer networks under asymptotically nonlinear oscillatory shear,” J. Rheol., vol. 61, no. 4, pp. 643–665, 2017. [3] R. H. Ewoldt and N. A. Bharadwaj, “Low-dimensional intrinsic material functions for nonlinear viscoelasticity,” Rheol. Acta, vol. 52, no. 3, pp. 201–219, 2013.