Too few resin in laminate?

[arneansper]

I'm trying to figure out if I should use some home-made laminate or not.

I took two layers of Ukrainian 120gr/m2 unidirectional carbon, wetted them out from bottom to top (rolled resin on table and then rolled the carbon until the resin came through carbon), rolled more resin on the top. Then I blotted the carbon using tissue paper and heavy roller, put two layers of blotted carbon together and laminated between two layers of peel-ply. I also warmed the layup in the beginning of bagging to make resin thinner and make it flow under vacuum. I used very slow resin.

After bagging the peel-ply was uniformly soaked by resin.

Now, my problem(?) is that the laminate came out too light. I calculated the carbon weight as 20.5gr. The resulting laminate weighted 22.5gr. I cannot believe the 91% carbon content. I thought that more like 50% would be normal for carbon laminates.

I cut thin tapered strips from the laminate and they seem to have nice uniform bend - I do not see any soft spots. I believe the carbon threads are fully soaked. But I'm afraid there might be some voids between threads.

Strips are ment to be used as sparcaps for SuperGee wing and will be bonded to the core using resin. Should I add some extra resin to compensate for potential lack of resin in laminate? Or should I make new laminate without blotting?

How big is the carbon content in industrially made laminates?

regards,
Arne

[chetosmachine]

As a general rule, weight how much carbon fiber you will use. Then mix the equal amount of resin, and use all the resin. Use heat to make the resin as thin as you can, then do the laminate. All the resin excess will be soaked with the toilet paper, but make sure you use almost all the resin.
I don't believe you have 90% of fibre content. Make sure you weight the dry carbon properly, because 10% of resin doesn't make miracles. You can't wet 20g of carbon with only 2g of resin..... that means that if you break it, you will see LOTS of fibres dry....
First make sure you did a 10% laminate, if so, discard it. Sometimes it's better to remake it than use and it then find it was poorly made :o
regards,
Chets

[arneansper]

Thanks for reply.

I made a new piece of laminate today. This time I weighted the carbon - it was 23.6 gr - so my calculations for the first patch were correct and this is really 120gr/m2 carbon.

Mixed 42 gr of resin. Some of the resin was trapped in the roller and some on the sheet but the carbon was really wet after rolling. Used full vacuum and heated the layup. Peel-ply was completely saturated with resin.

Result - 4% increase of weight. Laminate looks nice, breaks are sharp, without long (dry) threads. So it looks like the carbon content is really ~90%. Very strange result.

regards,
Arne