Construction of an Abaqus Parallel Rheological Framework (PRF) material model to describe the complicated PTFE stress response.
The stress strain response of the plastic, synthetic fluoropolymer of tetrafluoroethylene (PTFE), is very complicated. It doesn’t behave exactly like a hyper-elastic rubber nor does it behave like a classic thermoplastic. Our testing programs have shown that even very small strains result in some plastic set.
The use cases for PTFE are varied but often involve large strains and the need to capture the deformed stiffness, load and unload, of the material AFTER a large initial deformation.
The Abaqus parallel rheological framework (PRF) allows us to combine native material models in Abaqus. In this case, the Marlow hyperelastic model is combined with Mullins softening, Johnson-Cook plasticity and a couple of Power Law visco-elastic legs to create a stable, realistic PTFE behavior description.
The tool that makes this possible is the 3D Experience Material Calibration application. Here is a screen shot from this application:
The particular case above is just an example from material we purchased from McMaster-Carr, not a customer’s data. However, the behavior is similar. With additional effort, we were also successful in adding additional strain rates to this model.
Feel free to contact us about material modelling projects. Also drop us a note if you’d like us to share this material model and underlying PTFE data.
Here is the material model form, abbreviated:
*MATERIAL, NAME = “PTFE Case 1”
*HYPERELASTIC, MARLOW, MODULI = INSTANTANEOUS
*UNIAXIALTESTDATA
0, 0
0.65641741032, 0.000721863
1.39761572412, 0.001536959
2.2345449861, 0.002457331
………. more rows
14.62089520752, 0.28223261
15.5389469634, 0.361574333
16.1124171453, 0.470418595
16.2218136486, 0.500486267
*MULLINSEFFECT
1.00000018813934, 0.111904153234089, 0.605449831804942
*VISCOELASTIC, NONLINEAR, NETWORKID = 1, LAW = POWER LAW, SRATIO = 0.159562556518645
6.95004185875384, 2.90147696995603, -0.495539407318264, 0, 1
*VISCOELASTIC, NONLINEAR, NETWORKID = 2, LAW = POWER LAW, SRATIO = 0.286681335001964
4.04212306992274, 2.10784709008935, -0.907640199150582, 0, 1
*PLASTIC, HARDENING = JOHNSON COOK
14.0716522407142, 163.95207861071, 3.51411555245135E-07, 0, 1499.85, 999.85
*RATEDEPENDENT, TYPE = JOHNSON COOK
7.93305315300565E-06, 0.33770945152831
