Carbon Fiber Plenum (Plys)

[thescreensavers]

How many Layers of Carbon do teams with carbon fiber intakes do their plenum's with?

[Dash]

It depends on the weave really. We had some really thin stuff a few years back and ended up doing like 5 layers ( no core ). I'd imagine if it was thicker we could have done less, or put stiffeners in it.

[Owen Thomas]

Dash is right, it depends on your layup practices/materials.

All I can say is, use an extra layer from what you think is good. Our CF plenum imploded last year at competition. Not fun.

[dmacke]

I believe our team uses 5 layers as well. We've never had any problems with strength or sealing.

[thescreensavers]

Ouch that sucks Owen, how many layers did you guys use?

Did you use Resin or Epoxy?

We are going with how many layers we think + 2 heh, we don't want it flexing.

We haven't tested it yet but do we have to worry too much about radiant heat from the engine? We have aluminum runners and so we are thinking of making something to slow heat transfer to the runners and plenum (basically our gasket material)

The Worst time for heat would probably be during the driver change up for endurance.

[Owen Thomas]

We used 2 or 3 layers, I believe it was either resin infused transfer or wet layup with bleeder cloth. The layup was decent, but if I recall we had to "paint" it with resin afterwards since it didn't quite seal properly. Obviously, I would recommend at least 4 layers now.

We use Vinyl ester resin for CFRP runners since it is gasoline resistant, and I cannot recall if we used epoxy or polyester resin for the plenum. Epoxy *should* be used. Either way, make sure you clear coat the outer surface so it doesn't delaminate in the sun.

From my experience, the heat transfer into the plenum shouldn't cause an issue. Your aluminum runners might get a bit hot, but the only downside I can think to that is small displacement of your injectors. Probably not a big deal.

[Dewi Griffiths]

Hi guys,

I'm unsure of the amount of ply's on our plenums, but then again we haven't been using them for a few years. Instead we use rapid prototyped versions.

Similar to the discussion of number of ply's, how thin are people going with RP plenums? Or do you think this deserves a thread of its own?

http://fsae.com/eve/forums/a/t...20897151#48520897151 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/48520897151?r=48520897151#48520897151)

Quotes here of 5mm/0.25 inch but would be nice to compare to others.

[jlangholzj]

Originally posted by Dewi Griffiths:
Hi guys,

I'm unsure of the amount of ply's on our plenums, but then again we haven't been using them for a few years. Instead we use rapid prototyped versions.

Similar to the discussion of number of ply's, how thin are people going with RP plenums? Or do you think this deserves a thread of its own?

http://fsae.com/eve/forums/a/t...20897151#48520897151 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/48520897151?r=48520897151#48520897151)

Quotes here of 5mm/0.25 inch but would be nice to compare to others.

Just got ours back on tuesday. Looks bitchin! ...besides the point.... I went with a 5mm thickness on all of my parts as well and I can say that it is quite beefy, but in a good way. I'm thinking that if I get creative next year that I could go to 2mm with some additional webbing on the outside.

First iteration though, 5mm would be a great target.

[Dewi Griffiths]

Awesome stuff! Ours is in that ballpark too. Scope for smaller but it's acceptable for the moment.
I'll have a word tomorrow with someone who would know about the number of ply's. He's designed and made several.

[Kevin Hayward]

The number of plys will depend greatly on the shape of the plenum. Have a simple look at the stresses and deflection in a pressure vessel shape vs. a flattened box shape when you apply an internal vacuum. With a pressure vessel shape only 2 plys might be necessary, but with some of the shapes I've seen you would need up to 10 for even close to similar performance.

Kev

[mech5496]

On Kevins post, we used to use a shperical plenum. 3 plies were enough...

[Rory Hourihan]

We got our plenum 3d printed then used 3 layers of a bidirectional carbon fiber over top, plus one more layer for a nice finish, then dissolved the 3d printed mold out of the carbon fiber

[Loz]

Some of the responses make it seem as though there is only one "type" of carbon fibre reinforcement in existence or only one type of rapid prototyping material available.

The question is about as arbitrary as asking someone “how many eggs do you add to your cake?”.

The answer to both questions is hugely based on material selection and to a lesser extent manufacturing process used. To say that 3, 4, 5, 6, etc layers of reinforcement is required is completely misleading without any specification of fibre type of reinforcement perform.

There are lots of different fibres, with vastly differing strengths, stiffness’s and diameters, as well as lots of different reinforcement types, weaves, tows, thicknesses, weights etc, all of which have an effect on the number of plies used in a given layup. Then there is the question of resin types and the complexity of answer balloons out even further... Always remember that material properties of a reinforced composite part are not determined until the completion of fabrication and there are a lot of factors prior to that stage that contribute to the performance of the final product.

The same can be said for a rapid prototyped part, it all depends on the material used, the process used for manufacture and the design that ties it all together. Fortunately many of the rapid prototype base materials and manufacturing processes lead to a final material which is closer to an idealised isotropic material than the predominantly anisotropic reinforced composite.

[MCoach]

Any boosted applications in here?

Just something to consider.

[CorbinJ PBR]

A good way to be sure is to do some CLT calculations (If someone on your team has taken a composites class). If you know the minimum pressure, you can simplify the plenum to a beam with a distributed load using the approximate maximum width of the plenum as the length of the beam. you can then select an arbitrary width (since we are dealing with pressure) and then use the pressure and area to solve for the distributed load. Solve for the max bending moment and plug it into your CLT calcs to see if it fails. Like most complex composite problems there will be many other factors effecting the results but this method is much simpler than doing FEA . The curvature will add a lot of stiffness and strength so you can have confidence that indication of not failing from hand calcs will very likey hold true. All this may seem unnecessary but JUDGES LOVE IT, we always get asked about if we've done any analysis on our plenum and our steering wheel so it's a good thing to be able to show them.

@Owen Thomas.

Was that at Michigan last year? I may have seen that and it did not look like fun.

[Owen Thomas]

@Corbin,

It was at Lincoln, but you may well have seen it. If I recall you guys dropped by our paddock a couple times after it happened. Our intake was smoking for about 15 minutes after we patched it with aluminum, scrap carbon, and some seriously hot-mixed resin. It was quite the sight.