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Description
Title: | Elastic stiffening in PVA-Borax studied with experimental medium amplitude oscillatory shear |
Author(s): | Carey-De La Torre, Olivia |
Advisor(s): | Ewoldt, Randy H. |
Department / Program: | Mechanical Sci & Engineering |
Discipline: | Mechanical Engineering |
Degree Granting Institution: | University of Illinois at Urbana-Champaign |
Degree: | M.S. |
Genre: | Thesis |
Subject(s): | Stiffening
Asymptotic nonlinearity Medium amplitude oscillatory shear (MAOS) |
Abstract: | In this thesis, we seek to understand the mechanisms of strain-stiffening and shear-thickening often observed in transient or associative polymer hydrogels; specifically, Poly(vinyl) alcohol (PVA) crosslinked with Sodium tetraborate (Borax), or PVA-Borax. We use medium amplitude oscillatory shear (MAOS) as a tool to measure asymptotically nonlinear viscoelastic material functions across a range of compositions of PVA-Borax with storage moduli ranging from $G_0 \approx 100-3000$~Pa. The material functions can be related to model parameters to gain physical insight into the structure of the material system. We demonstrate that with a "good" structure-rheology model \cite{AshwinModel}, a single nonlinear parameter scales the asymptotically nonlinear material functions, and we argue that finite-extensibility is the sub-dominant cause of nonlinearity ($<5$\%) compared to stretch-induced crosslinking. Furthermore, we validate the model by using first-harmonic MAOS measures to predict third-harmonic MAOS via a single nonlinear model parameter. Finally, we define a universal nonlinear parameter to compare the strength of nonlinearities across a range of strain-stiffening materials. |
Issue Date: | 2017-09-20 |
Type: | Text |
URI: | http://hdl.handle.net/2142/99288 |
Rights Information: | Copyright 2017 Olivia Carey-De La Torre |
Date Available in IDEALS: | 2018-03-13 |
Date Deposited: | 2017-12 |
This item appears in the following Collection(s)
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Dissertations and Theses - Mechanical Science and Engineering
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Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois