I have an idea to make a component out of carbon fiber and in the past i would have carved up some foam for a core and overlaid epoxy and glass or carbon fiber.

Now that I have a 3D printer, I am considering printing the core and overlay with cloth and epoxy.

When searching the forum, I found only references to using 3D printing for a mold.  Maybe I did not search correctly.  Has there been anyone with experience doing this?  The core would be in several pieces and bonded together.  Preferably PLA and West System epoxy.

You may be interested in Slicer designed specifically for lightweight/stiff panels, eq perfect fit for 3D printed composite cores - it aims to compete with structural foams/honeycombs in performance.
It's of course it's perfectly doable to slice your core model with any other slicer, but because of classic slicing process limitations, the core with sufficient stiffness will end-up significantly heavier then strictly needed - fine for pattern/dimensional prototype, less then stellar for functional prototype/production part.