Release film

The release film is used to isolate the part from the gas permeable layer and to control the amount of resin that leaks out. The release film has small holes in a known pattern that can squeeze trapped air and excess resin out of the laminate. For prepreg parts in autoclaves (or very thin parts compacted in ovens), non-porous release membranes are usually used. By keeping all the resin in the part, the weight and fiber volume fraction can be well controlled and predicted. This is only applicable where there is no need to extract trapped air or volatile gases. In autoclaves, pressure can keep these potentially volatile materials liquid or compress them into smaller volumes. Release membranes can be used in the perfusion process and their main advantage is the ability to keep the resin supply very even and make it easier to remove the flowing medium from thin and fragile laminates. It does extend the distance between the flow front and the fully wet laminate, so if you don't pay attention to resin breakage, it could get you in trouble!