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Vacuum Bag Terms

  • Thursday, 24th January 2019
  • Reading time: about 3 minutes

Bleeder: A nonstructural layer of material used in the manufacturing of composite parts to allow the escape of excess gas and resin during cure. The bleeder material is removed after the curing process is completed and the excess resin taken with it.

Breather: A loosely woven or nonwoven material that acts as a continuous vacuum path over a part but does not come in contact with the resin.

Mold Release Agent: A material applied to mold surfaces to facilitate the release of the molded article. Liquid, paste, spray and solid release materials are all common in composite fabrication.

Peel Ply: A sacrificial nylon, polyester or non-porous Teflon ply that is placed over the outer plies of a laminate during lay-up. When the resin has cured the peel ply is removed. The results are a smooth surface that is easily prepared for subsequent bonding or painting.

Perforated Release Film: A solid release film that has been perforated with a uniform hole pattern comprised of usually 0.015” or 0.045”. Hole spacing ranges from 0.25” to 8” spacing. The effect is to restrict the amount of resin bleed that is able to pass through the film.

Solid Film: A barrier between the bleeder and breather layer to prevent the excess resin absorbed into the bleeder from soaking into the breather. The solid film is sized smaller than the bleeder and breather to allow an air path connecting both.

Tool: A structure, also referred to as a mold, that provides a specific size and shape in or over which a lay-up is formed, shaped and cured.

Vacuum Bagging Film: An airtight flexible sheet placed over a lay-up and sealed along its edges. The bag is fitted with vacuum ports and connected to a vacuum source. During the cure the bag is evacuated and the lay-up is compacted under atmospheric or autoclave pressure. Vacuum is applied to the bag during the entire cure cycle.

Vacuum Port: A machined or cast metal fitting that connects the vacuum bag to the vacuum source. The vacuum source can be a vacuum pump or a compressed air venturi. The port is connected to the vacuum source with a reinforced hose. Both the hoses and ports typically incorporate fittings that allow the hoses to be removed without losing the vacuum.

Vacuum Sealant Tape: A thick rubber based adhesive tape that is sticky on sides and used to form a seal between the vacuum bag and the tool surface. It has the ability to remain soft and pliable at temperatures in excess of 350ºF.

Published courtesy of Abaris Training Resources, Inc

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