GL-P:
Well, if you're unsuccessful in getting that mandrel free, you may have to resort to chipping and scraping the epoxy resin and the carbon fiber off the metal. Rubber mallet, flat side of a chisel, gloves, lung, and eye-protection.
* Beats self with a clue-stick * Okay, I admit it, I am offically a senile old geezer. Gotta love those CRS situations. We're talking single layer composites, and if I remember correctly, 29mm in diameter here.
Wear heavy gloves to protect your hands from sharp fragments, and safety goggles to protect your eyes. Long sleeve shirt and a dust mask is mandatory. CF slivers are NOT fun, and are not covered under the "easy to remove" section of any first aid kit. Took me several hours to get a piece out of my arm once. Epoxy fragments are even less fun. So be careful.
Try this. Take a utility knife (Stanley (tm) type) and a lot of spare blades. Spray the blades with Silicone Spray Lubricant (Yet another DIY store trip) and polish them dry with a peice of paper towel. This not only gives you sharp blades (and keeps the ones you don't use from rusting), but also reduces the amount of surface area the epoxy can grab against as you're cutting (Silicone Spray will fill in the rough surface area of the steel, etc, ad nauseum). Then, using multiple light passes and a straight edge or steel rule [taped in place] to guide the blade, slice through the carbon/epoxy matrix along the mandrel (end to end). It'll probably take you 30 to 40 passes, and several blades. This will take you a while, but it'll save the mandrel. Once you get through the epoxy, try lifting one of the edges of the cut with the razor blade, wedging it open as you go, with toothpicks or dull utility knife blades at first. Assuming that you waxed the mandrel before laying up your fiber and epoxy, you should be able to peel the majority of it off. A single layer of cured carbon fiber (you did say 5.7oz, right?) isn't as stiff as most people think. It'll probably be about as hard to bend as heavy cardboard, crabshell (Crawfish?) or lobster shell.
Most people look at carbon fiber as being a very strong material, but it is actually a two-dimensional fabric of strings (err. most of it is 2-D anyway) that is only strong in tension. Like thin sheet metal (think car door panels, body work, etc), most of its strength and rigidity comes from the shape it is formed into. Once you cut a string under tension, it no longer supports anything.
Harm none,
ResearchWorm