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. 

I think in this particular case it is bridging at the edge of the core. you will never have 100 % uniform pressure over this transition. At what angle is the core cut?

If it is resin starvation then you have to use an additional glue film between core and prepreg. the safest way would be to cure in two cycles, first the outer skin, then remove the peel ply, add glue film, core and backing layer and back in the autoclave.

Thank you, we will try to make it in two cycles now!

Lesters idea is sound.  Tapering the core so there is no bridging can help, as can using adhesive films and multi shot processing.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant