Prepreg is a fabric or tape that is impregnated with a resin
during the manufacturing process. The resin system is
already mixed and is in the B stage cure. Store the prepreg
material in a freezer below 0 °F to prevent further curing
of the resin. The material is typically placed on a roll and a
backing material is placed on one side of the material so that
the prepreg does not stick together. The prepreg material is
sticky and adheres to other plies easily during the stack-up
process. You must remove the prepreg from the freezer and
let the material thaw, which might take 8 hours for a full
roll. Store the prepreg materials in a sealed, moisture proof
bag. Do not open these bags until the material is completely
thawed, to prevent contamination of the material by moisture.