Snap-fit design and semi-crystalline polymers

[BiPolarMoment]

I have a snap fit concept that is fixed at both ends(deflects in the center) and I have very few options for changing the cross section or amount it needs to deflect. However, I would like to minimize the length necessary to deflect my prescribed amount without failing (FOS approximately 1).

I'm trying to approximate this as a simple fixed-fixed beam, but how well do traditional stress/strain equations translate over to a semi-crystalline material(PEEK), especially as it nears the yield limit? Are there other obvious resources for evaluating the performance in a situation like this?

Now the other problem is that I would be simulating this using a constant cross-section beam (i.e. no "hook" that is on the actual design) so while I can reduce the stress in that situation by reducing the thickness of the beam I create a worry that the stress concentration at the back of the snap fit "hook" flat may become critical. Because iterative prototyping would be idea it is financially unfeasible, so I'm trying to at least get a best guess before breaking the bank.

I attached a picture of the feature for reference.

 

[Pud]

In a critical application, get the material supplier to check your design. They tend to have the "real" data, and the experience. And usually it's free!

You will (likely) have specify their material.
And you can then blame them if it's wrong!

http://www.tynevalleyplastics.co.uk