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Vacuum Bagging

  • Friday, 25th January 2019
  • Reading time: about 2 minutes


This is basically an extension of the wet lay-up process described above 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.

Materials Options

Resins: Primarily epoxy and phenolic. Polyesters and vinylesters may have problems due to excessive extraction of styrene from the resin by the vacuum pump. 
Fibres: The consolidation pressures mean that a variety of heavy fabrics can be wet-out. 
Cores: Any.

Main Advantages

  1. Higher fibre content laminates can usually be achieved than with standard wet lay-up techniques. 
  2. Lower void contents are achieved than with wet lay-up. 
  3. Better fibre wet-out due to pressure and resin flow throughout structural fibres, with excess into bagging materials. 
  4. Health and safety: The vacuum bag reduces the amount of volatiles emitted during cure.

Main Disadvantages

  1. The extra process adds cost both in labour and in disposable bagging materials 
  2. A higher level of skill is required by the operators 
  3. Mixing and control of resin content still largely determined by operator skill

Typical Applications

Large, one-off cruising boats, racecar components, core-bonding in production boats.

Published courtesy of David Cripps, Gurit

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