Vacuum infusion bag - can external pressure help?

[R_Rose]

Vacuum bags are used to infuse various things with liquid resins such as fiberglass or carbon fiber. It seems that the higher the vacuum the better (and possibly faster) the infusion works. Could it be more effective to use a vacuum bag and also have the entire bag in a pressure chamber to get a higher total pressure for the infusion?

If the pump that was available could only produce 50% vacuum, could this be overcome by the pressure chamber and would the external pressure have the same effect on the infusion as a vacuum has?

 

[CWatters]

Short answer is yes.

What matters is the pressure differential between inside and out. At sea level the maximum pressure differential would be about 14psi (eg a perfect vacuum inside and 1 atmosphere outside). The only way you could increase this would be to use a pressure chamber.

 

[CWatters]

would the external pressure have the same effect on the infusion as a vacuum has?

In theory yes but in practice there might be some differences, particularly if you did not use a breather membrane inside to ensure the pressure differential was uniform over the surface of the laminate.