I know that PVC is easier to go to Lowes or a plumbing supply store and get, but given that you are going to have to have a flange on at least one end (and maybe it's easiest if you put a flange on both, and use big ol' allthread rods to pull the end flanges tight), it might be safer and easier to just get some schedule 40 steel pipe, weld (or have a competent pressure-vessel welder weld) a cap on one end, a flange on the other, and go for it. A blind flange with a two threaded fittings on it (you could seal weld the threads), a 3/4 inch ball valve, a pressure gage, AND A PRESSURE RELIEF VALVE SET TO 110psi, and you'd be in pretty good shape.
If the eight inch size is about right, you might want to find a dead air compressor, the dual tube design, and salvage the pressure vessels. Flange on one end, salvage the relief valve (which is sized properly for that vessel - cool!) and youd be good to go more cheaply.
At eight inches diameter, and about three feet long, and 100 psi, you are getting pretty close to the 1.5 cubic foot/150psi exemption limit on ASME Boiler and Pressure vessel code (you'd have to be less than 4 foot long or so to avoid having to register the design and have a PE evaluate, approve, and stamp your drawing). There's a reason for those thresholds - the amount of energy released is limited. And you are getting close to those limits. An 8 inch diameter PVC pipe at 100psi would be, err, either memorable, or the last thing you remember.
I'd go with steel pipe myself.
Jim
PS I would think that you'd want a vacuum on your carbon layup to cure it. Or is the pressure used as a clamp?