Talk Composites - The Forum for Advanced Composites

Weird fiberglass panel issue

http://www.talkcomposites.com/Topic39519.aspx

By raygun - 11/19/2020 2:35:09 PM

I'm getting ready to make a mold from the hood of my 2011 Corvette. When I bought the car in April, it had a weird matte vinyl wrap on the hood. When I removed said wrap (ugh), I found an odd grid of what I thought, at the time, were scratches.
Since I've finally found time to get started on the planned carbon hood with some heat extraction, I took a closer look at the hood. These don't really look like scratches so much as CSM. They also line up with the reinforcement on the bottom of the panel.
I cannot, for the life of me, figure out what could possibly cause this. I posted a question on one of the Facebook groups. It turns out that a lot of Corvette owners have this issue, in the pattern and same places on the hood. Someone suggested that it may be related to heat from storing the car in direct sunlight. That strikes me as weird.




And on someone else's car:

I love the car, but... lovely GM quality strikes again.
Any ideas what could cause this? Also, I'm worried that buffing and preparing the surface may just make it worse. I'd appreciate any advice y'all might have  as to cause and possible solutions. I'd really like to clean this up before making a mold.
By Hanaldo - 11/23/2020 2:44:49 AM

 
raygun - 11/22/2020 1:55:23 PM
 
Hanaldo - 11/21/2020 6:24:04 AM
No, you can't really avoid it (it happens to big car manufacturers, they would stop it if they could) its just a side effect of bonding panels. You need a strong adhesive to bond the panels, but those adhesives shrink. So using one with very low shrink will help, but they all shrink to some extent so it isn't completely avoidable.

This looks especially bad though, it shouldn't be so bad. Hard to know why it is this bad without knowing what materials were used and how everything was made. I would hazard a guess at quite thin fibreglass skins in combination with poorer quality materials and someone being very heavy handed on the adhesive gun. Also potentially parts that have gotten hotter than the resins/adhesives maximum service temperature. 


Well, that's disappointing. But, there's no getting around physics & chemistry.
Maybe I should just rivet inner and outer panels together. BigGrin

Haha yeh that would  look worse 🤣

I feel I've made you more worried about it than you need to be. It is not really possible to avoid it altogether - it is possible to avoid it happening to this extent. It should not be so noticeable, generally it is one of those things that you only see if you are looking for it and you catch the reflection at the right angle.