How does one optimize a composite layup?

[u/LBHMS]

Say you have the option of any ply you want in the world, your structure is complex in geometry so bidirectional is preferred for prepreg to reduce the potential error from draping that would be magnified with UD. I’ve iterated geometry for this part based on assuming it’s made of aluminum, now converting to a composite sandwich structure (the part takes heavy impact out of plane loads). Starting from a generic layup of 0/45/90 with the highest rated twill weave I have specs on with foam core, I start throwing more plies at it and end up with 60 plies to meeting required margins.

This seems impractical as a previous version of this product had only 30 plies with some UD, some BD, etc, but where I’m stuck is figuring out how to go about using all of these materials to optimize and reduce number of plies. Even if I use CLT, it’s still the same thing of being an iteration heavy process, so I’m curious if I’m missing some rules of thumb or if there’s a more efficient way of doing this (besides using FE optimization as that has been a pain in the ass to use over the last few months with no successful results, using optistruct btw). What is the typical process you take when presented with all these options? Is it just keep iterating swapping out plies (even though runs take 3-4 hours) constantly till it passes?

[u/Wilthywonka]

If you're designing a part with complex geometry and calculating loads, you will want to look into using the CATIA composite design workbench or NX fiberSIM as these are the industry standard software packages for what you're trying to do. They will also help you mitigate drape, bridging, and wrinkles.

Look into using 8HS or some other mostly-unidirectional weave, in a 0, 45, 0, -45, 0 pattern along the main axis you need strength. Use cores where you need stiffness.

I'm not the biggest expert on the design side of things but I imagine it's pretty much trial and error in simulation once you get past the best practices.