None needed. Carbon fiber is a very stable material, like G10, or FRN.
If you're looking for something to keep it from getting scratched, probably something that offers a clear coat like paint clear coat (what is often used on bicycles with raw CF). Helicopter tape is also common in high abrasion spots on bikes, like where cables rub. I would think a polyurethane coat wouldn't be bad either, I just don't think it would last well.
It's really a non-issue, IMO.