Raw carbon. clear coat needed?

[mathias720]

Hello i am thinking about doing a Raw carbon finish on my sram red crankset as i am running shimano for the rest of the parts.
do you have to clearcoat it or can you let the surface be raw with no finish?
it would be alot easier as i can do the soda blasting myself but cant paint it, and the weight of the clearcoat off-course?

what will happen if you let it stay Raw? maybe something with the UV

[eucalyptus]

The resin will react with UV and turn yellow

Either clear coat (weight is like non existent) or use UV protective wax (this had to be done in intervals to maintain protection)

[matcav]

would it have just a cosmetic effect (yellow-ish reflex) or would it comes also with structural / safety issues?

[Rishie]

I've done this a few years ago. Aerospace 303 to protect seems to do the job with no yellowing.

[Maddie]

I also did this years ago without any protection on the surface at all. No yellowing, and my bikes see a lot of sun. Sram seems to be using UV resistant resin

[mathias720]

seems like i just gotta go do it and dont paint it.
how is the aerospace 303, does it change the surface any way ?

[Juanmoretime]

I too ran a raw carbon fork for years and used the 303 on it once a week. Looked beautiful to me and did not yellow.

[PyotrGhimme]

It depends on the type of lesin used.
Generally speaking, prolonged exposure to UV do make mechanical properties of CFRP
“Deteriorate”. As far as I know, decades ago, there’s a huge jumbo air accident with numerous casualties . It was caused due to the uv induced deterioration of CFRP parts used in vertical stabilizer.

[bremerradkurier]

It depends on the type of lesin used.
Generally speaking, prolonged exposure to UV do make mechanical properties of CFRP
“Deteriorate”. As far as I know, decades ago, there’s a huge jumbo air accident with numerous casualties . It was caused due to the uv induced deterioration of CFRP parts used in vertical stabilizer.

I guess UV detoriation in aircraft components would in general be more frequent given their operating altitude vs. cyclists.

[Rishie]

seems like i just gotta go do it and dont paint it.
how is the aerospace 303, does it change the surface any way ?

Nope. It's just a protective coating. Goes in easy and can be taken off similarly.

[Pyotrump]

It depends on the type of lesin used.
Generally speaking, prolonged exposure to UV do make mechanical properties of CFRP
“Deteriorate”. As far as I know, decades ago, there’s a huge jumbo air accident with numerous casualties . It was caused due to the uv induced deterioration of CFRP parts used in vertical stabilizer.

I have to edit my statement haha. That accident I mentioned is about American Airlines Flight 587.
this was caused by overuse of vertical stabiliser not by the UV-damage to composite. However it is still true that UV can damage CFRP.

[Maddie]

However it is still true that UV can damage CFRP.

Please show some examples from 2010 or later.

This aerospace303 stuff needs to be reapplied every 30 days. Come on guys, who does that? While the application of this product doesn't hurt, I much rather believe that the resins themselves are already uv stable. I build some carbon parts and even the resins I use are uv stable.

[Pyotrump]

However it is still true that UV can damage CFRP.

Please show some examples from 2010 or later.

This aerospace303 stuff needs to be reapplied every 30 days. Come on guys, who does that? While the application of this product doesn't hurt, I much rather believe that the resins themselves are already uv stable. I build some carbon parts and even the resins I use are uv stable.

Khaleel, Salah Mahdi, Tim Hilditch, Riyadh Al-Ameri, and Bernard Rolfe. “Influence of Ultraviolet Radiation on the Morphological and Mechanical Properties of Carbon Fiber-Reinforced Polymers.” SAE International Journal of Materials and Manufacturing 13, no. 3 (2020): 229–40. https://www.jstor.org/stable/27033973.

Zhao, Jun, Gaochuang Cai, Lu Cui, Amir Si Larbi, and Konstantinos Daniel Tsavdaridis. 2017. "Deterioration of Basic Properties of the Materials in FRP-Strengthening RC Structures under Ultraviolet Exposure" Polymers 9, no. 9: 402. https://doi.org/10.3390/polym9090402

Various studies show that the ultimate tensile strength and modulus of FRP(CFRP, GFRP, etc,.) sheets decrease with UV exposure time.

+ I want to point out there're some UV resistant epoxies nowadays.
++ UV can damage the polymers but the damage is rather slow and kinda natural phenomenon.

[Monticola]

Raoul Luescher recommends to seal cut (not sure if it's applicable to sanded) carbon parts because the resin is hydrophilic:
https://www.youtube.com/watch?v=ieeCqlQy5sY

[Klaster_1]

and the weight of the clearcoat off-course?

When a paint shop stripped my frame, I asked them to use the very minimum amount of clearcoat. They ended up using less than 10 milliliters for the whole frameset.