Carbon Fiber Repair?

[PJ]

So, does anyone know how to repair cracked carbon fiber parts?

Got some minor crash damage to a nice component and want to salvage it, but not sure how to fix it.

Was thinking about slapping on some fiberglass in the cracked area...but don't want to add alot of extra weight.

Thoughts?

[cornercamping]

A friend of mine has a 748 that has carbon everything.  Every crash repair pretty much is just sanding it down, and putting another layer of resin on it.  No glass reinforcement.  The gas tank on the bike has to have like 30 additional layers over the years on it.  You can still see the carbon too  8) I say just put the parts together, and re-resin over the damage.  Make sure to just sand it, and clean it really good prior to applying resin.

Use polyester resin and MEK for a good solid overlay.  :D

[cornercamping]

Oh yeah, and if you really want to reinforce the damage, most fiber glass/carbon fiber places have "carbon fiber tape' you can use.  It's a roll (about 5 ft. long) of carbon fiber "tape."  It's usally available in 1" or 2" wide x 5 ft.  It's real carbon fiber cloth that you can use to fix broken parts.  Just put down a quick layer of resin on the broken part, apply the "tape" and then resin over the tape.  Good as new.  It's not really tape, just looks like a roll of black tape.  It's just precut carbon cloth strip.  Sorry, trying to make sure you understand what I mean.  
We don't bother sanding it down after the last layer though.  Too much work for a part that will probably get broke next weekend..  :-/

[Nate R]

Polyester resin will bond well with cured polyester, but NOT with cured Epoxy.

Carbon is usually done with an epoxy resin.

Rough up the area, 36-60 grit sandpaper would work.

If you want, I can send you some scraps of carbon you can use to reinforce. Free. Just give me an address, and about how much and about what size.

Then, get some epoxy resin, and lay up a couple layers of carbon on the backside of the part around the damaged area, if there is a backside.

If it's bodywork, make sure you tape the hole or whatever in front with some scotch tape or the like. Then later, peel the tape off, and smooth the outer surface with bondo, if it's painted.

What kind of part is cracked?  I might be able to repair it.