Good morning,

I have to build a +- 2.5 liter CF air tank that hold 10 bars continuously.
My plan is to shape a cylinder (7.5 cm diameter and 15cm long) in a block of foam that need to resist epoxy resin under vacuum, wrap it with 6 layers of CF, after cooking I will drill two holes where I will later install some plugs, filling through them acetone to dissolve the foam and get a final clean inside piece.

My questions are :

- is my plan the easiest or do you have a better idea ?
- which foam to use (I want to avoid glue in the process and 10cm height is your only option) ?
- how many layers of 400gr CF would you recommend (my intention is 6) ?

Thanks for your kind advice.

               

You can think of it this way ..  Hand layup CF with vacuum has a slightly better strength than the same thickness in aluminium--

6 layers of standard 200gsm twill will give you roughly 1,5 mm thickness which will probably not be enough to have a safety margin ..

I would make such a "tank" by first laying up 2 layers of standard CF cloth, then ppel-ply, then vacuum ..

Once cured, I would wind on two layers of CF tow ... Hard .. while applying resin .. This will give the "tank" a very high "hoop-strength"  Start at one end, then go back over the first layer and keep the winding tight .. keep the tension on by clamping the "loose end" of the tow .. then let it cure to a tack, and apply an outer layer of Carbon/kevlar mix .. (to avoid sharp shards of CF IF the tank "breaks")

This way you will have a tank that has a good safety margin for the 10 Bar ...

You may want to think about making metal (stainless steel)  threaded adapters an integrated part of the layup.. it will be less prone to cracking along the strees points that wil always be present when drilling and gluing them in ..

Please post pics e.t.c.  here -- of your experiments. 

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Thanks Dravis. Original tank is made of 5mm alloy... Do you know where I can purchase a 20x20x20 block of foam please ?

These types of thing are made as Dravis mentioned by winding tow onto a former, otherwise known as filament winding.