| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 5179053 | Polymer | 2016 | 11 Pages |
•A modified WLF model including pressure effect is proposed for nearly incompressible polymers.•A test procedure for extracting the model parameters is proposed and experimentally validated for polyurea.•A simplified form of the model is developed and yields good approximate results, compared to the full form.•Both forms can accurately predict the pressure shift factor data from confined compression tests of polyurea, reported elsewhere.
The combined effect of pressure and temperature on the mechanical behavior of polyurea is characterized and integrated into a constitutive model based on Williams-Landel-Ferry (WLF) equation. An increase in pressure is related to a decrease in temperature, both pressure and temperature affecting the polymer's molecular free volume and thereby introducing a pressure-dependent term into the WLF equation. The model is derived based on Fillers and Tschoegl's original work, regarding the free volume as a state variable. The model provides a closed-form expression for the time scale shift factor for equivalent temperature in terms of temperature and pressure and its three-dimensional surface representation. The prediction of the present model agrees well with pressure shift factor data obtained from confined compression tests of polyurea, reported elsewhere, confirming our constitutive model and its experimental calibration procedure. A simplified model of the pressure effect is also developed which yields good approximate results.
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