How to model PET above Tg for static analysis on Ansys Workbench

[andradesilva]

Dear Colleages,

I am modeling PET at a temperature above Tg in ANSYS Workbench. PET behaves as Viscoelastic above Tg. I want to do a static analysis (Mechanical loadings). What material model should I use?

I found out that the following material models are available:

Prony Shear Relaxation
Prony Volumetric Relaxation
William-Landel-Ferry Shift Function
Tool-Narayanaswamy Shift Function
Tool-Narayanaswamy w/Fictive Temperature Shift Function

I have the values of the parameters for the WLF material model. However, it does not support stress analysis.

Also, there is Shear data and Bulk data, supposely from experimental tests. As an alternative, is there any database available with values obtained from experimental tests, by other scientists?

Thanks in advance

Best regards,
AndradeSilva,PhD

 

[rickfischer51]

First, PET is also viscoelastic below Tg, as are all thermoplastics. And, can you catch viscoelastic response with a static analysis? How much strain are you expecting? Is your loading long term or short term?

Rick Fischer
Principal Engineer
Argonne National Laboratory