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.