Rock chip to carbon fiber - options?

[SSTAT]

Hi all -

Had the whole car clear bra'd and then went on the Hot Rod Power Tour. Great trip. But... no clear bra where the rock hit the carbon fiber, or the windshield where it left a nice crack. Here's a pic -



1. So I know they has to use a special clear on the carbon fiber otherwise it turned yellow, does chevy off this as a touch up?
2. Assuming they have this, would you just touch it up and hope it goes under the lifted area or would you try to remove the lifted area first? The carbon under the chip truly doesn't look damaged, and I think if not for the lifted clear I doubt you could hardly see it unless you were looking. The rock actually hit a spot before this one where there was clear bra and no damage there.

I'll take any advice, thanks -

[scottcolem]

its a resin thats used to bond the carbon then clear coated. from the looks of the pic you should just be able to touch it up with a little clear then sand and buff it out. wont even be able to tell after your finished

[ChrisBlair]

I was a composites technician for years

Scott is spot on, it's carbon fiber in a resin matrix, and first thing I'd try is what Scott suggested- a little clear as in, dip a clean tool like those used to sculpt clay in some clear and then carefully press- not wipe- it on. Once the c/f is 'wet' again it will probably be invisible. I'd suggest not trying a resin, it's messy and you don't know what resin it was.

...or remove it and do a VARTM on it, good as new ! (joking)

Don't get a c/f splinter. Take my word on it. (not joking)

[SSTAT]

Great info, thanks. So you think the clear will soak up under the clear that has lifted (the white ring)? I'm afraid of an air bubble getting trapped under there then not being being able to correct it. Paint is the one thing on cars I don't do. Ok, besides transmissions...

[ChrisBlair]

Nothing should 'soak in'; the resin should already have impregnated the c/f, the c/f should be "full" if you see what I mean. Don't think of it as a layer of resin on the top and bottom and fiber in the middle. No air should be able to migrate. I don't see anything to suggest a void (air bubble) would be introduced to this processed laminate: nothing is making the air invade the part.

I still have some c/f samples at work, including stuff that is only staged (not fully cured) that would help to illustrate but I'm on vacation and sorry but I'm going NOWHERE NEAR that place for two weeks, lol . But the parts would look very different although they are made from the same stuff exactly- the 'staged' stuff looks like a woven basket. The processed stuff looks like your part: the resin flowed during processing.

My guess is that this part of yours is a uni-directional tape called 'prepreg'; that means 'carbon fiber that has been pre-impregnated with resin before panel lay-up', instead of using a resin matrix that must invade the c/f during processing such as 'VARTM' which is 'Vacuum Assisted Room Temperature Molding', for example, in which you have a dry fiber structure and a supply of resin that is drawn through the part. Prepreg helps eliminate voids among other things. But anyway, what you're seeing is this:

The composite structure gets a nice pretty layer of resin 'on top' visually but the resin should be all through the c/f; this is the point and this is what makes c/f very strong in relation to weight. It is processed under pressure and heat. Now, in your photo, the c/f does indeed look a bit 'dry' to me but I don't know the resin, the type of fiber, the process they used etc. It could just be how the light is playing in the pic and it may be that a tiny bit of c/f was 'peeled away' and the damage just looks dry, which is my first guess.

But I wouldn't let any of that worry me. It's secondary structure, not a major strengthening piece.

What I'm trying to say is that the part isn't 'weakened' in a meaningful way, it just looks different and your goal here is to duplicate the appearance. Take some rattle can clear coat, spray it into the can cap, and use some tool to transfer the clear to the part. The repair is small and the clear should flow a bit, but be careful about too much- don't make a run. I'd say an artist's paint brush would be good but wouldn't that be a kick in the nuts to get a bristle on the repair!

[kbob]

I think if that were mine I would 2000 grit sand it to remove the lifted clear coat then reapply new clear to that little section. Then rubbing compound to make the new clear shine like the original.

[SSTAT]

OK I am resurrecting this thread with some good news. I finally got up the nerve to try to fix the chip at the top of this thread. I started by trying to lift and snap off the lifted clear with the tip of a razor blade, it worked at first but then just lifted even more clear making the hole even bigger, so then I just cut the lifted clear out directly with the blade. Then I put about 3 coats of clear down in the hole on top of the CF. This built up edges around the edge of the hole so then I started sanding with 320 (yikes right?). Then it was wavy so I did three more cycles of clear and sanding with 320. Then I wet sanded with 1200 until it looked evened out, then 2000, then 3M polish 4 or 5 times. I truly cant believe how great this came out:

after I finished with the 320, scary, I've never dug into beautiful brand new car paint like this in my life:


After I finished with the 2000: you can see the original hole but the surface is glass smooth. Even after the polish if you try hard to can see this ghost circle in the clear.


After the polish:

[Kevlar382]

Before the 2012s were even out I posted that chipping the CF was one of my biggest fears. Had a hand fully of people tell me that there was no way a stone could hit that far up the hood. Guess I better get at covered with clear film.

[KaBoom1701]

This is one of my fears as well....

Has anyone covered their CF hood vents with protective film? Can this be done? Anyone know how much?

Thx

[SSTAT]

The cf HAD clear bra on it when this happened. But the kit only covers the big flat surfaces when you look down on the cf, the kit didnt include the verticle sides like where mine was hit. However, the rock that caused that chip hit the cf an inch or so ahead first on an area with clear bra which damaged the clear bra but the cf under was undamaged.

[SSTAT]

And again, the rock then went on crack my windshield. Paid over a k for clear bra then one rock hits thee times, twice in places without clear bra and badly damaged :( I dont play the lottery.

[KaBoom1701]

I just replaced my windshield last month...I feel your pain....