Against the surface of the last laminate, a peel ply can be applied. Peel ply serves two functions. First, it eliminates or reduces the need for sanding or grinding prior to secondary bonding operations. Second, peel ply may be left on the laminate. This will keep it clean until the next step in construction.
Peel Plies are woven fabrics which are generally applied as the first material in the composite laminate bagging sequence. They are designed to be peeled from the surface following cure to leave a textured surface, which is clean and contaminant free. This surface is then ideally prepared for secondary bonding, filling, or painting and does not usually require any further mechanical abrasion. The textured surface left on the laminate is an imprint of the weave of the peel ply and therefore fine weaves will impart a finely textured surface. Peel plies are usually made from polyamide (nylon) or polyester fibers. Polyamide fabrics are more commonly used, though polyester fabrics must be used with phenol-based resin systems. It is important to store peel plies in a cool and dry environment, ensuring the fabric is kept clean and free from possible contamination.
Breather Cloth is a material, which will not compress under pressure to the extent that air cannot be drawn through it. Often, an otherwise perfectly sealed bag will not develop full vacuum pressure because the bag under the hose fitting is pinched off preventing the evacuation of air from the rest of the part.