I am using a layer of the surface carbon with 2 layers of 400 gsm prepreg. I used the same material from the same role successfully in the past at the same temperature and cure time. 150f and 200 f. I use an aluminum mold under constant vacuum. The only change in procedure has been time since last used (about 4 months). The carbon is probably 8 months old or so, and has been frozen when not used. The carbon failed to cure. It is quite bizarre. Any ideas would help. Typically when the shelf life is exceeded the carbon cures, this seemed to dot he opposite. There were no unusual signs prior to the baking. I have made numerous successful parts using this procedure, this is my first odd failure of this type.