Wikipedia wont help that much because a lot of the Carbon fibre sheet is pre impregnated with the resin and just requires heat and pressure to make the bond. Though you will find that the resin used is part of the manufacturing process and therefore cloaked in manufacturers non disclosure.
All that said the longest length of metal I have ever put in the wrist of a gun stock is six inches by 10mm (three eighths of an inch diameter). Though it was not a solid piece of Marine grade 316 stainless steel rod I put a 6mm hole through making a tube to reduce the weigh and still giving enough support for the break because Marine grade stainless is dam tough. So carbon fibre rod held no interest because I doubt that there was much different in weight but a good difference in cost, also as I said stainless is far less reactive.
