Manufacturing Process
Vacuum bagging
Vacuum Bagging
This process is basically an extension of the wet lay-up process where pressure is applied to the laminate once laid-up in order to improve its consolidation. This is achieved by sealing a plastic film over the wet laid-up laminate and onto the tool. The air under the bag is extracted by a vacuum pump and thus up to one atmosphere of pressure can be applied to the laminate to consolidate it.


Related book or publications

Phenolic Liquid Resin Hand Lay-Up Techniques


Table 1:  Consumable materials and equipment required for vacuum bagging [reference]
Peel-ply A sacrificial open weave fibreglass or perforated heat-set nylon ply placed between the laminate and the bleeder/breather to provide the textured and clean surface necessary for further lamination or secondary bonding.
Bleeder cloth A non-structural fabric designed to absorb excess resin and reactants from the laminate.  This may also act as the breather cloth.
Breather cloth A loose weave or non-woven porous material use to provide a gas flow path over the laminate both to permit the escape of air, reactants, moisture and volatiles and to ensure uniform vacuum pressure across the component.  This may also act as the bleeder cloth.
Release film A (perforated) sheet of material placed between the laminate and the mould surfaces to prevent adhesion.
Edge dams Profile used to define the edge of the component
Caul plate A mould or tool placed on top of the laminate inside the bag to define the second surface.
Intensifiers Generally hard rubber profiles incorporated in the bag to consolidate the laminate at sharp radii.
Bagging film The membrane which permits a vacuum to be drawn within the bag.
Tacky tape Adhesive strip used to bond the bag to the tool and provide a vacuum seal.
Breach unit A connector through the bagging film to permit a vacuum to be drawn.
Vacuum pipes The link between the breach unit and the vacuum pump.
Resin trap A container in the vacuum line to collect any excess resin before it can damage the vacuum pump.
Vacuum pump Generally a high-volume pump (absolute vacuum is rarely required) suitable for continuous running.  For some slow-curing epoxy resins twenty-four operation may be needed.
Pressure gauges Generally clock-type gauges attached via a breach unit connection.

Benifits of this process Typical Applications:  
Large products possible
Top-quality products through the use of prepregs
Clean production method
Low molding costs
Large, one-off cruising boats, racecar components, core-bonding in production boats



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Reference: netcomposites and John Summerscales



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