Carbon strength under pressure. How much carbon?

General Composites Discussions Engineering Talk
#1

Im looking to make á few intake manifolds for cars. Lets say I have a wax mold, I will coat this mold in cf and when complete melt out the wax.
For the runners I intend to use woven tubes, I will slide them over the wax mold cinch them and epoxy them.
For the plenum I intend to use carbon fiber fabric.
When complete I will bond in annodized aluminum or plastic mounts for the throttle body and the injectors.

For my application I will have constant pressure of say 15 psi and a peak pressure of never more than 25psi.

What density carbon fiber should I use for both the runners and plenum and with how many layers on each? What if i was to go for 40 psi max pressure?

this is what my manifold looks like:

thanks in advance!

#2

There are a myriad of ways to approach and build this. None quick to detail here. A naturally aspirated plenum is difficult enough but a boosted version requires engineering x10.

1)-You’ll need to consider waste gate failures and boost spike conditions.
2)-You’ll need to research component attachments and hardware.
3)- You’ll need to explore clamshell or piece work assembly or perhaps pre-preg one piece and autoclave.
4)-You may have to consider building or re-engineering how each runner attaches to the plenum chamber while keeping things true and square for no leaks.
5)-Don’t forget that the larger flat planes will need structure to avoid ballooning under boost.

Then again, since the M50 manifolds are a carbon plastic that tends to crack…you could simply wrap them with CF wetted with resin and vacuum bag and post cure to re-enforce and already developed part. But that is if weight isn’t a big concern.

#3

Hi,

This is something I’ve been thinking about as well recently and think I have come up with a reasonable (pretty basic) way to solve it- or at least get a first basic layup using FEA and CLT.

Can you upload a few more pictures please with as many dimensions as you can add in MS paint and I’ll knock up a CAD & FEA model. Some “square on” orthographic photos would really help a lot too.

Cheers,

Andy

#4

Hi, any luck with a few more pics and dimensions please?