CF Laminate Adhesive

[Coasty]

I made a laminated sheet from 3 layers of 5.7 oz CF cloth and laminating epoxy. I laid this between 2 pieces of acetate sheet and placed a 50 pound weight on top and allowed it to cure overnight. This sheet was this cut into sections that will be assembled into a heli frame. Trouble is I'm having trouble getting CA or epoxy to hold and I believe that this is due to the (very) smooth finish.

I wondering the fix is to simply roughen up the area to be sanded - or should they somehow be prepped or primed in some other manner? This is my first time to experiment with assembling a structure with CF laminate so any advise would be appreciated.

[davidfee]

Yes, you must scuff the areas to be bonded with sandpaper. You should also clean away any debris or oil with acetone or denatured alcohol. Don't use 5 minute epoxy (you didn't say you were) or CA for structural joints on composite panels, since they are both rather weak. Use laminating epoxy thickened with colloidal silica, short milled glass or carbon fibers, or cotton flox.

Good luck,
-David

[davidfee]

3M also makes a great adhesive for applications like this. It's called DP-460 and has excellent peel and shear strength, for use in bonding composites and metals. It comes in special tubes which require a $40 applicator gun though.

-David

[Coasty]

I'll try the sanding and cleaning with acetone this evening - thanks for the info.

[Coasty]

Yep - that works. Sanded the surface and cleaned with acetone. Tried both CA and epoxy and now the joints are very strong - thanks!