Hello Jorgen:

Thank you for your reply. I have since registered at the website and have incorporated their stress/strain data into my model, along with UHMWPE data supplied by one of your papers on this website.

In regards to modeling the PEEK and UHWMPE:

1.) For element formulation, I am using 8 node elements since 10 nodes is computationally expensive at this point. I do have a thin PEEK section that for all intents and purposes can be described as a cantilever beam loaded at its end in my construct, so I have used an incompatible mode formulation to hopefully account for any significant bending. This is also a static analysis.

2.) For material formulation, at first I used a linear material formulation, however I felt this was not capturing what was occuring at this thin section, so now I am using an multilinear material formulation without large displacements/strains to see if I can capture what is occuring at this thin section.

The issue that I am having at this point is this: in the test lab, this thin PEEK section is not undergoing any plastic deformation but my FE model is predicting yield at loads smaller than in the test lab. Also, the UHMWPE is in contact with and bending this thin PEEK section. I am not sure if I am capturing what is occuring with the UHMWPE since I can see the deformation due to contact with the PEEK on the UHMWPE peice and not in the FE model. Since both of these materials exhibit some viscoelasticity, due you think the loading rates given for the published material properties has a great effect on the results or should I start to think about a more advanced material formulation?

Sorry for the long explanation, I hope I did not confuse the subject. Your help is greatly appreciated.

Thanks,

Tim