To the OP: This is what it looks like when you "troll" members of a forum, whether you intend to or not.
I haven't hit the "red flag" button yet, but you are inviting it.
You are providing too little information for us to help you.
I believe what the OP is working with is called "foamed aluminum core"
Modeling this should be done as a monolithic set of properties. Modeling in any way other than that is nonsense since the material is basically a sponge.
Fatigue is not applicable to this material in the typical sense of the word. It's not really "fatigue" when it is so vastly full of flaws, inclusions, voids already. Concepts such as "notches" are irrelevant when every surface is as rough as sandpaper. I can't deny that growth of a crack in your material isn't similar to fatigue. The problem is that the stress models that define the behaviour of fatigue mathematically are not based on this kind of geometry, and can't be forced into it either.
I don't see the point of discussing with Hexcel because this isn't a product they make so they wouldn't know anything more about it than a web search I just did. I don't know what it's normally used for. Could be great for sound isolation when you absolutely cannot use a non-metallic barrier (for whatever reason). Just guessing. I would never have heard about it either, except for someone who asked if it would be good for impact energy absorption. "Maybe, but impossible to apply quality control, so not worth trying".
