Carbon fiber is nasty stuff, I'd avoid it.
I'd also avoid phenolic sheet, here's what the EPA has to say.
Phenol is considered to be quite toxic to humans via oral exposure. Anorexia, progressive weight loss, diarrhea, vertigo, salivation, a dark coloration of the urine, and blood and liver effects have been reported in chronically (long-term) exposed humans.
An easy to work with material is 1/16" Aluminum sheet, it's readily available and cheap. I think I paid a couple dollars each for 5 x 10 chunks of 1/16" aluminum sheet.
