failure model of viscous polymer

[lwn]

Dear All:

I just have a question. Do you have any suggetion to the failure of viscous polymer materials? I am trying to simulate the deformation of polymer materials, characterized by visco-elastic (or visco-plastic model). But right now I only have a single value of shear stress strength. I think the stress strength should be rate-dependent, is it right? Which kind of test should be used to determine it?

Thank you.

David

[Jorgen]

Hi David,

There is not a single answer to your question. The best failure model will depend on the type of polymer, the loading conditions, and the environment.

I recently performed a study (http://www.polymerfem.com/modules.php?name=Downloads&d_op=getit&lid=39) where we studied the failure of UHMWPE under monotonic loading to failure in different loading modes. The results from that study indicated that certain failure conditions are more accurate than others. For example, the chain stretch was a better predictor than the Mises stress or the max applied strains. We also showed that in our case the applied loading rate did not influence the observed failures.

What type of polymer are you studying? What loading (monotonic or cyclic) are you interested in?

- Jorgen

[polydamage]

Dear All:

I just have a question. Do you have any suggetion to the failure of viscous polymer materials? I am trying to simulate the deformation of polymer materials, characterized by visco-elastic (or visco-plastic model). But right now I only have a single value of shear stress strength. I think the stress strength should be rate-dependent, is it right? Which kind of test should be used to determine it?

Thank you.

David

Just try a test with different loading rates (preferably displcement controlled) and see whether you get same slope for the stress strain curve. If they turn out to be different indeed if you have a visco elastic or plastic model they have to be different else it doesnt make sense to call it a visco -elastic or plastic....

cheers