Talk Composites - The Forum for Advanced Composites

Keeping the carbon on the flanges during layup

http://www.talkcomposites.com/Topic20861.aspx

By mrlindeman - 3/20/2016 7:12:07 PM

I have been running into a persistent issue with some proof in concept work I am doing.

Materials:

C&J Composites epoxy 2-1 part resin.
2 X 2 3K 5.7 OZ carbon fabric.

6 inch by 3 inch half round mold. 

This mold is taken off of a tube. Its a 1 piece half round shape. It is a gel coat finish with one inch flanges.

The mold is prepped with a thin coat of resin and 2nd stage cured to tack. Then the first layer of carbon goes in.

The problem I am having with this and many other molds is, that once the carbon is pressed into the mold and the edges are folded over to tack to the flanges; there is lifting in the bend which caused voids on the edges. Even at full tack it still lifts. When more layers and resin is applied the issue gets worse. The remainder of the part looks almost perfect but any contours like this cause the fabric to peel slightly and cure with dry areas.

This is a hand layup and with vacuum it would not be an issue, but I am trying to figure out how this is done successfully in a strictly hand layup process.

Thanks for any help. My digi-cam is dead so unfortunately pics are not an option. 
By Fasta - 6/19/2016 2:58:20 AM

You could also consider a silicone intensifier where you would have an inner silicone block that clamps on the back of the laminate until cured.

Layup a dummy part in your mould to match the finished part thickness and then pour cast a silicone into the back of the part, even include the flange if you dam the edges to stop it flowing out. The silicone block can be clamped down with something flat like plywood or other.

Something else to try is maybe looking at your laminate orientation. If the the fibres are running directly square over your flange corners then this is a more difficult and sharper corner for the fibre than if your material were at 45 degrees. The softer angle across the corners is easier for the fibres.

Also maybe finding lighter/softer fabrics. Finishing the last ply with fibreglass instead of carbon or just adding a little thickening addative to the resin will make it a bit sticker and help it stay in place.