M4 F80 M4 Carbon Roof Failure and Repair

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G3Carbon

Lurker
Aug 30, 2019
11
So, we've got a client who stopped by with what is one of the worst carbon failures I've ever seen.

It started with this:

[YT]

I've been doing this for 8 years and I've never seen a resin and carbon failure like this.

So, we took delivery of the car last week and now we're working on a complete re-lamination of the factory roof with fresh carbon fiber.

It's a LOT of work, it's not cheap, but it'll leave the owner with a roof with greater visual clarity and a MUCH longer life expectancy.

I'll attach some pics of our progress asap. :)

Enjoy!
 
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fmorelli

Colonel
Staff member
Aug 11, 2017
2,459
Virginia
May I take a guess to the process question? Maybe that's not actually epoxy layup resin you are pulling up. That's finish which BMW is spraying overtop of the carbon roof. That would bring this into a finish adhesion problem, not a structural carbon delamination failure (aside from the damage areas which you qualified as having taken a hit). If it turns out my wild guess is right, this could be covered under BMW warranty.

Filippo
 
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G3Carbon

Lurker
Aug 30, 2019
11
May I take a guess to the process question? Maybe that's not actually epoxy layup resin you are pulling up. That's finish which BMW is spraying overtop of the carbon roof. That would bring this into a finish adhesion problem, not a structural carbon delamination failure (aside from the damage areas which you qualified as having taken a hit). If it turns out my wild guess is right, this could be covered under BMW warranty.

Filippo
You know, I was thinking the same thing.

Understanding it's a single piece prepreg roof, it's most likely that it's some sort of top coat, given how it peeled like this.

What was most strange is how it peeled off and there was a TON of resin dust that came with it, which makes it all a little more unusual.

It should have been a warranty repair, I thought (2016 with 30k miles on it), but the owner was insistent when it came to fixing it and not going through the dealership.

Either way: more pics to follow. :)
 

G3Carbon

Lurker
Aug 30, 2019
11
Here's the first resin pour!!!

It ends abruptly because my tech (Ben) slipped and almost fell off the stool he was standing on. :D (he didn't get hurt, thankfully)

[YT]
 
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doublespaces

Administrator
Oct 18, 2016
7,765
AZ
So you lay up another layer of CF with new resin and then you're going to put a clear coat on top instead of whatever that film stuff was?
 
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G3Carbon

Lurker
Aug 30, 2019
11
So you lay up another layer of CF with new resin and then you're going to put a clear coat on top instead of whatever that film stuff was?
Actually, we use a non-epoxy system for film build and clarity, sand that back to the original shape, then clear coat it with urethane automotive clear.

I've got stuff on cars for 5+ years that look brand new, but we recommend reclearing every other year to maximize the life expectancy.
 
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Rob09msport

Major
Oct 28, 2017
1,711
Monroe CT
So, we've got a client who stopped by with what is one of the worst carbon failures I've ever seen.

It started with this:

[YT]

I've been doing this for 8 years and I've never seen a resin and carbon failure like this.

So, we took delivery of the car last week and now we're working on a complete re-lamination of the factory roof with fresh carbon fiber.

It's a LOT of work, it's not cheap, but it'll leave the owner with a roof with greater visual clarity and a MUCH longer life expectancy.

I'll attach some pics of our progress asap. :)

Enjoy!
BMW puts 8 yr on defects in finish I thought.
 

G3Carbon

Lurker
Aug 30, 2019
11
BMW puts 8 yr on defects in finish I thought.
Seemed odd to me, too, man.

Guy was adamant about not warranting it.

There was strike damage from road debris, so I even suggested he run it through his car insurance and he pushed back hard against that, too.

Some people have reasons for doing things that I don't always understand, bud.
 

Rob09msport

Major
Oct 28, 2017
1,711
Monroe CT
Seemed odd to me, too, man.

Guy was adamant about not warranting it.

There was strike damage from road debris, so I even suggested he run it through his car insurance and he pushed back hard against that, too.

Some people have reasons for doing things that I don't always understand, bud.
If I was local to someone able to do what you just did i understand. The dealer would not make look like that and if gonna keep car forever like i am with mine i get it.
 

fmorelli

Colonel
Staff member
Aug 11, 2017
2,459
Virginia
Nice. Curious which epoxy layup resin you used? (I work with silver tip a fair bit, but different application). Did you shoot a clear over it? UV cure? Just curious ... nice work!

Filippo
 

G3Carbon

Lurker
Aug 30, 2019
11
If I was local to someone able to do what you just did i understand. The dealer would not make look like that and if gonna keep car forever like i am with mine i get it.
That's the thing: the dealer repair protocol is to remove the roof completely, then bond in a new one.

It'd be a 100% perfect repair.
 

fmorelli

Colonel
Staff member
Aug 11, 2017
2,459
Virginia
Factory repair protocol is pretty inexpensive, eh? lol ... that would make sense if it was a structural failure. But this looked like a finish adhesion failure. I don't know if you ever concluded such? If it is an adhesion failure, that would be interesting. First off epoxy mix for such resin layups is exceptionally accurate activity by gram weight. I don't doubt that the manufacture process is highly controlled. Second, material bond failure would be unlikely in a single case - since these kinds of things almost always are a factor of 3 things: chemical bond issues, cure time, preparation. The latter two highly controlled in a manufacture environment. The first ... not always solved 100% (since you are in the finishing business, you are well aware e.g. Mercedes Mars Red as a recent example, where prolonged UV exposure presents a finish adhesion issue between base and clear coat.)

My very long winded way of saying ... I'm wondering if more of these are going to show up - and it's presenting as a chemical bond issue that becomes evident over prolonged UV exposure.

Filippo
 

G3Carbon

Lurker
Aug 30, 2019
11
Factory repair protocol is pretty inexpensive, eh? lol ... that would make sense if it was a structural failure. But this looked like a finish adhesion failure. I don't know if you ever concluded such? If it is an adhesion failure, that would be interesting. First off epoxy mix for such resin layups is exceptionally accurate activity by gram weight. I don't doubt that the manufacture process is highly controlled. Second, material bond failure would be unlikely in a single case - since these kinds of things almost always are a factor of 3 things: chemical bond issues, cure time, preparation. The latter two highly controlled in a manufacture environment. The first ... not always solved 100% (since you are in the finishing business, you are well aware e.g. Mercedes Mars Red as a recent example, where prolonged UV exposure presents a finish adhesion issue between base and clear coat.)

My very long winded way of saying ... I'm wondering if more of these are going to show up - and it's presenting as a chemical bond issue that becomes evident over prolonged UV exposure.

Filippo
I'd assume most, if not all of them are going to do something similar.

That having been said, I don't know I'd say BMW (or their external supplier in this case) isn't using a precisely controlled system here, given the fact that the roof is 1 piece pre-preg and I'm sure it's finished in an autoclave.

This isn't some backyard wet layup or vacuum infusion so much as it's top-tier auto manufacturer and one of its flagship cars.

To your point, this looks like a typical carbon fiber failure, as presented when subjected to too much UV and solar radiation when you don't clear coat them.

I do believe it's an adhesion issue between substrate and top coat, which, again, would suggest that more of these will likely pop up.
 
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