Abstract
An ultra-stable instrumented nano-indentation tester (UNHT, Anton Paar) was used to study extremely long (30000 seconds) indentation creep of polymers. Total drift rate, measured on fused silica and sapphire samples, was less than 0.2 pm/second for up to 10 hours, enabling collection of valid, low-uncertainty, long-term creep data - orders of magnitude longer than previously possible. Fits of the popular N element Kelvin model to indentation creep data gave values of instant elastic modulus E0 and infinite modulus E∞ strongly dependent on the time-span of data fitted. Comparison with the long-term experimental data showed that the model was unable to use short term data to predict creep at the much longer times required by industry. A new analysis method is proposed to obtain a better estimate of the true value of infinite modulus, E∞, which is the simplest indicator of maximum dimensional change of polymeric material components subject to long-term stress.
| Original language | English |
|---|---|
| Pages (from-to) | 297-309 |
| Number of pages | 13 |
| Journal | Polymer Testing |
| Volume | 70 |
| Early online date | 26 Jul 2018 |
| DOIs | |
| Publication status | Published - Sept 2018 |
Bibliographical note
NOTICE: this is the author’s version of a work that was accepted for publication in Polymer Testing. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Polymer Testing, Vol 70, 2018. DOI: 10.1016/j.polymertesting.2018.07.022© 2017, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
- indentation
- long-term creep
- viscoelastic
- modulus
ASJC Scopus subject areas
- Polymers and Plastics
- Surfaces, Coatings and Films