Carbon Fiber crack repair

General Composites Discussions Composites Talk
#1

Greetings! I am not a carbon maker myself just seeking some help to people who I think would know most about them though!

I bought a carbon roof, overall condition is okay, just some minor set back that is not noticeable in a few feet. Up close you can see 1 large crack on the side, and small ones all the around the roof. My problem is the long crack, it seems like it has gone through all the way down to the carbon itself. Is there a way to fill the crack? Do you just sand it and hope the clear coat can get through or do I need resin? How do you spray the clear? Do you sand first, then buff, then respray the clear? Here are some pics

LONG CRACK

Here’s a sample of the crack that goes around the roof. Seems like these are sandable then buffable

Here’s a big crack but I believe weather trim will cover this part but might as well fix it.

#2

As far as I can see it’s the clear coat that’s cracked. Sand it back and paint a new clear. I can’t see or it’s a real crack on the last picture. Be carefull with sanding the clear down that you don’t damage the carbon fiber. If you have no experience with this and you don’t want to screw up your carbon roof bring it to a specialist.

#3

Ny saying “be careful not to damage your CARBON FIBER” do you mean down to the fiber cloth themselves or just to the epoxy resin of the carbon fiber? How can i tell if i’m sanding the clear coat or the epoxy resin already?

#4

He means be careful you’re not sanding the fibers themselves. I don’t know how to effectively describe this on a forum but you can tell you’re getting close to the fibers when they start looking “dry”.

I know my explanation isn’t that good. Hopefully someone posts in this thread and gives a better one!

#5

If dry sanding , you’ll see the weave pattern begin to distort when you’re about to burn through the fibers .

If wet sanding , you’ll see the carbon grit load up on the sandpaper . Just check it frequently and keep wiping it down with a clean sponge . Either way I would try to repair it installed so that the pressure you’re applying on it doesn’t damage it more . It’s hard to tell how thick it is from the pic or how sturdy it may be .

#6

Yeh if you’re wet sanding, the dirty water will be a milky sort of white until you go through to the carbon, where the water will start to go grey.

#7

Carbon fiber/Kevlar race kayak Repair: [ame=“http://www.youtube.com/watch?v=Xm2Ezo70vFI”]How to Repair a Damaged Composite Canoe or Kayak - Carbon/Kevlar Fibre - YouTube[/ame]

OR! You can sand even make a small groove (cut in bevel) into the crack and make a epoxy putty with bubble glass powder,graphite powder,fiber glass powderr and aerosil/cabosil/fume silicia. You can heat the putty with a heat gun to increase the polymerization. Fill up the crack and put a small release demold film and tape the release film with a masking tape. Et voila! The crack is filled up with a simple super strength epoxy putty :slight_smile:

#8

That’s not a good solution for this and will make it even worse.
This are coating cracks and not in the product itself.

#9

Helped me get an idea though :). I will sand it a little see if the cracks go away, if not, i will have to dremel the cracks a little bit and fill it with resin see if it seeps all the way down

#10

If you have enough mil thickness to dremel into the crack and not cut through the carbon fabric below , it is going to eventually crack again anyway . The strength of a composite is in the proper fabric/resin ratio and excess pooled resin above that offers no benefits . Those spots are always the first to show surface blemishes and damage since they are the weakest areas in the composite matrix .