PTFE at high strain rates.

[PS]

Hello Forum members,

I am working on an application with pressurized PTFE-nozzles in the temperature
range 20 - 100 deg.C.

Does anyone know of a good modeling approach for Fluoropolymers (unfilled-
PTFE) under high strain rates 10 - 500 /s, with a maximum strain of 0.1 - 0.2.

Is there a saturation of the stiffening of the PTFE material for higher strain-rates?

Does the DNF model accurately capture the viscoelastic effects at these strain-
rates, or is there a better model?

Does anyone know of any empirical data for PTFE at these strain rates?

Grateful for comments and suggestions, thanks!

[Jorgen]

Hi PS,

The problem that you are describing sounds quite similar to a problem that I recently worked on. In my case I had a PTFE seal that was exposed to temperatures ranging from 20 to 100 deg C, and medium to large strains. The main difference in my case was that the strains rates were rather small compared to yours.

When I worked on this project I developed a specific user-material model for the PTFE (the DNF model, see papers in the downloads (http://www.polymerfem.com/modules.php?name=Downloads&d_op=getit&lid=43) section).

The DNF model is really powerful at predicting the response of PTFE and other fluoropolymers. Also, since the DNF model is based on the same micromechanism inspired equations for the flow behavior as the Bergstrom-Boyce model, it is very likely that the DNF model also very accurately captures the behavior at high strain rates, such as 10 to 500/s.

In my experience, most thermoplastics (including PTFE) is not experiencing a significant saturation in stiffening at the strain rates that you mentioned.

I have seen experimental data for different thermoplastics and rubbers at the strain rates that you are interested in, but not specifically for PTFE.

Best of luck,
Jorgen