Talk Composites - The Forum for Advanced Composites

Prepreg with foam core dry spots?

http://www.talkcomposites.com/Topic36352.aspx

By Merit Fernhout - 4/24/2020 7:35:33 AM

We are trying to make a round disc of two layers of prepreg (Deltapreg GG200T DT120) with a core of 5 mm AIREX C71 foam. The foam is cut in a circle end the edges are cut diagonally. There is also a hole made in the middle of the foam to make space for a big head. However when the disc comes out of the oven, it is clearly visible where the foam is. At the edges of the foam it looks like there was not enough resin on the outside of the disk, since little holes are visible. This has happenend twice now (see finished product on the foto, with also a visible line of holes on the outer edge).

We think this might happend because the foam absorbs too much resin out of the prepreg. Is there a way to solve this? We thought maybe first coating the edge of the foam with epoxy and letting it dry? However this will maybe add a little bit of weight. 
By Fasta - 5/4/2020 9:18:15 AM

 
Warren (Staff) - 4/27/2020 12:00:14 PM
Lesters idea is sound.  Tapering the core so there is no bridging can help, as can using adhesive films and multi shot processing.

You can also cook the foam disc alone first on your mould as this will soften the foam a give the foam an almost moulded smooth finish. It will then take up less resin when you cook it with the carbon.