Models for EDPM

[craigj]

Dear Group,

I am looking for initial material model constants for an FEM simulation involving a Shore 55A EPDM (greater than 25% strain, static loading). Eventually I am going to have some "real" testing done, but right now I just want to get my model set-up and all the bugs worked out.

My FEM program is Ansys 8.1 and I would like to use an existing material model like Ogden or MR.

Does anyone have constants that I can use for my intial run that will get me in the right ballpark? In addition can anyone point me to papers that specifically discuss material properties of EDPM rubber?

Thank you :!:
CJ

[Jorgen]

Hello CJ,

Good questions. Without more information about your EPDM, and without doing a literature search, I think it is difficult to provide a reliable material model that will provide accurate predictions for your material. I would recommend that you perform a few key experiments to obtain the material response of your material.

My understanding is that there are no well developed guidlines for how to translate Shore hardness to Young's modulus (or shear modulus). And without that info, the Shore hardness value provides more of a qualitatitive comparison between materials than a value that can be used for material model calibration.

As a rough starting point, you can use the material parameters for the Neo-Hookean model that are given on the
Materials and Models (http://www.polymerfem.com/modules.php?name=Materials_Models) pages for elastomers. For the NH model, the two material parameters that are given are for the shear modulus and the bulk modulus.

[eddy]

For EPDM Sponge rubber Blatz-Ko and Hyperfoam model in Ansys suits better.Because these models are used for compressible materials.
Following paper may help:

D.A.Wagner, K.N. Morman, Y.Gur and M.R.Koka
Finite Element Analysis and Design.
Nonlinear analysis of automotive door weatherstrip seals.