Carbon fiber fuel tank 4

[Bozo_Sam]

Hi There,

we are developing the carbon fiber fuel tank for vehicle application. We are worried about the chemical resistance of the CF tank. The tank would be made for the USA market, where gasoline can contain up to 15% of ethanol. I have come across some articles that the presence of ethanol in the fuel could potential problem for the CF tanks. Does anyone have any experience with that? If maybe anyone would know of the coating we could use for than to make is more resistant to the gasoline, that would be much appreciated.

thanks in advance.

Bozo

 

[LittleInch]

You're designing a fuel tank for motor vehicles and you need to come onto an engineering forum website for this level of design information????

Really?

I struggle to take this seriously, especially for the US market where any minor fault will have your arse sued off before you can make any money.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

Not only lining the tank but electrical isolation of fittings as well. Most all metals will corrode rapidly in contact with CF and water (especially salt water).
And you might need to plan on E85 as well.
Start searching for coatings used in the handling and storage of ethanol.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Check with your supplier but epoxy trains are not affected by ethanol except at elevated temperature.

Conductivity is a good thing in fuel tanks.

Permeability is an issue with "plastic" tanks. It may not meet emissions requirements for production vehicles. It may discolor over time.

 

[BrianPetersen]

What is the purpose of making the tank out of carbon fiber?

Lots and lots of automotive fuel tanks are made of plastic nowadays. No idea what exact material they use; you can google-search as well as I can.

 

[TugboatEng]

It's a strange thing, for decades off-road motorcycles have used polypropylene gas tanks. Then, Ducati and BMW put them on their road going bikes starting in the mid-2000's. Both made by Acerbis Plastics. Acerbis Plastics has also been making dirt bike tanks for decades. Anyways, the tanks swole up and couldn't be reinstalled after removal. Everybody blamed the ethanol while my 35 year old dirt bikes that also rub on pump gas never had issue. They blamed a coating failure on the tank. The old dirt bike tanks are uncoated, they just discolor and don't swell. Still, everybody blames the ethanol.

I blame defective evaporative emissions controls.

 

[Bozo_Sam]

Thanks for all the answers. I can see that the debate has gone a bit off. In the meanwhile, I have found an appropriate and tested coating that should protest the tank against ethanol.

https://www.caswelleurope.co.uk/ethanol-proof-fuel-tank-sealer/

Maybe someone needs this info at any point.

good luck!

 

[CWB1]

If you need a cheaper/easier/safer prototyping solution then look into tank bladders. On projects where there is any risk of a tank failure during test bladders are typically installed rather than coating the tank.

 

[TugboatEng]

Bozo, those tank coatings are problematic and if they start to flake or peel it will ruin your tank. Carbon fiber with epoxy resin IS compatible with ethanol. No coating is required. You do need to look in to the permeability of your particular pre-preg.

 

[EdStainless]

I talked with a friend who has some experience with this. Selecting the correct resin appears to be the key, and the inside surface must be resin rich so that there is zero risk of CF in contact with the fuel.

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P.E. Metallurgy, consulting work welcomed

 

[BrianGar]

If F1 dont use it...dont use it... they dont use it.

Brian,

 

[SwinnyGG]

If F1 dont use it...dont use it... they dont use it.

F1 doesn't use rigid carbon tanks because the rules say they can't- not necessarily because that wouldn't be the best solution. Fuel systems in F1 (and in every other serious racing class) are heavily regulated to avoid teams compromising driver safety to increase performance.

 

[BrianGar]

''Fuel systems in F1 (and in every other serious racing class) are heavily regulated to avoid teams compromising driver safety to increase performance''

'we are developing the carbon fiber fuel tank for vehicle application'

Which is why you shouldn't use one.

Brian,

 

[EHudson]

There are emission requirements for fuel systems. Lots of tanks are blow molded with multiple layers containing different resins that are resistant to hydrocarbons, alcohols and other components. It is not a simple stamping any more.

 

[SwinnyGG]

The driver safety requirements in F1 are quite a bit different than for road cars... F1 rules don't let them use stamped steel tanks either, which have been used on road cars for 100 years with acceptable safety.

 

[TugboatEng]

And now polypropylene fuel tanks are common in german made cars.

 

[GregLocock]

Single layer tanks haven't been emissions compliant for 2 decades or more.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Stephan Nelle]

Rhino 9700 is popular among the kit airplane crowd for coating composite wet wing fuel tanks. 100LL and Jet-A don't contain ethanol, but it might be worth talking to the manufacturer.

https://coatings.rhinolinings.com/p.../rhino-9700-thixotropic-epoxy-coating/144/167

https://www.kitplanes.com/rapid-prototyping-and-experimental-design-17/