is CF airtight?

[stroker]

Anyone know if carbon fiber is gas (atmosphere) permeable under pressure? If you made a cylinder or tank made of CF would air leak through the CF?

[datachicane]

I've used CF scuba tanks, and there's CF propane tanks out there, so yeah, I guess. I'm not certain if either of those use internal linings, but IIUC the resins used would dictate permeability (since the CF is basically just a matrix).

[cameraman]

The paint ball players use cf nitrogen tanks at 4500 psi to refill their guns. They don't leak.

[datachicane]

Heck, for that matter the 787 is a big, pressurized CF cylinder, right?

[miatanut]

I think the F1 tanks (like the one used for the pneumatic valves) have aluminum liners. Depending on the resins to hold the pressure in a fire could be a bad idea. Even if the resins soften in a fire, the layup would still give a lot of strength to reinforce the aluminum liner.

[Elmo T]

I think the F1 tanks (like the one used for the pneumatic valves) have aluminum liners. Depending on the resins to hold the pressure in a fire could be a bad idea. Even if the resins soften in a fire, the layup would still give a lot of strength to reinforce the aluminum liner.

The air packs we use for firefighting are similar: aluminum, wrapped in carbon fiber, then wrapped in a fiberglass resin. Pure carbon fiber would, I think, be subject to fragmentation on its own.

Here is the mfg info on our current cylinders:


Like all MSA fully-wound composite cylinders, Carbon-Wrapped Cylinders are made with a seamless aluminum liner that is precision-formed by a six-step process with quality control inspections all along the way. After forming the neck of the liner by a computer-controlled spinning process, the cylinder is wound thousands of times with high-strength carbon fibers impregnated with epoxy resin. The process is then completed with a final overwrap of fiberglass fibers for enhanced abrasion resistance. As a final touch, MSA added a "glow-in-the-dark" luminescent band for improved visibility at night.

[Ankf00]

Depending on the resins to hold the pressure in a fire could be a bad idea. Even if the resins soften in a fire, the layup would still give a lot of strength to reinforce the aluminum liner.

the resins aren't holding any pressure though, the fiber takes the stress. increasing ductility at high temp also depends on the resin material, never heard of CF which wasn't cured in an autoclave, the resin is going to be set after

[cameraman]

You don't generally see unlined cf tanks, if for no other reason that you need to have threads to screw on the regulator. It will also depend on the gas involved. Hydrogen in an unlined cf tank probably wouldn't work too well and I can think of some gases that would probably react with the resins with suboptimal results:eek:. The answer will depend on the application.

[stroker]

You don't generally see unlined cf tanks, if for no other reason that you need to have threads to screw on the regulator. It will also depend on the gas involved. Hydrogen in an unlined cf tank probably wouldn't work too well and I can think of some gases that would probably react with the resins with suboptimal results:eek:. The answer will depend on the application.

Helium is what I had in mind, specifically...

[miatanut]

the resins aren't holding any pressure though, the fiber takes the stress. increasing ductility at high temp also depends on the resin material, never heard of CF which wasn't cured in an autoclave, the resin is going to be set after

If the resins melted into glop, all you'd have is fabric (a very strong fabric) trying to hold a gas.

Does the curing process raise the melting point significantly?