It says in the technical datasheet of Easy Composistes out-of-autoclave Prepreg XPREG XC110, that for curing the "minimum vacuum pressure is 10mbar". This is a pretty low value. There are many vacuum pumps that can only achieve 50mbar, for example.

So my question basically is: why so low? To reduce the probability for pinholes? Because the relative gain in pressure when going from a 50mbar vacuum pump to a 10mbar vacuum pump is very small when you compare it to the outside pressure of a thousand mbar (well: 960mbar where I live).

The reason for such a low vacuum is, being out of autoclave, you are only relying on the atmospheric pressure pressing on the bag (due to being under vacuum) where as under autoclave conditions, you could have several times that pressure forcing the pre-preg onto to mould. This means every bit of pressure counts in terms of helping ensure the resin flows to the surface and you avoid pinholes or voids on the laminate surface.Reducing the level of vacuum means more chance of pinholes.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant