I make a lot of prepreg sheets using glass plates on top and bottom. The prepreg is sandwiched in between and baked in the oven in a vacuum bag. I have an issue with the prepreg surface quality. The epoxy does not cover the whole prepreg sheet and I therefore do not get a flat and glossy finish. Check out the attached picture. You will be able to see the fibers on the surface of the prepreg. The epoxy does in part not cover all the fibers of the prepreg (ref. picture). Here is my question:

Is there a product that I can use to fill those epoxy gaps on a prepreg sheet and make it look smooth and glossy?

Looking forward to hear from you.

What pre-preg are you using, is it an OOA? Are you using a flashbreaker tape around the edges to keep resin bleed down? 

If you dont need high temperature capabilities, you can use virtually any epoxy to fill the voids, but it isn't as simple as it sounds - it won't finish as perfectly as the piece of glass you're using as your tool, you will need to do some refinishing work. You could use a self-levelling epoxy like EC's Glasscast or Art Resin, but these will add a significant amount of weight to the finished part.

Hi Hanaldo

Thank you for your reply. I use SGL OOA prepreg and yes, it is out of date but I kept it at -30°C so I believe it is still as new as it once was? Maybe, a not outdated prepreg would give a llittle bit a better surface finish. When fabricating the prepreg sheet with the glass plate, I also use two lateral glass bar barriers so that the epoxy can not flow perpendicular to the fiber direction. Coming back to the surface finish:

I thought there would be something better on the market that would facilitate the adjustment of the prepreg surface. I might try the EC, Glasscast and see if this is worth my time?

Suppose I manage to get a nice surface finish, what do you use to polish the surface, what would you recommend?