Hi guys.
I have to do a carbon plenum wet laying for an atmosferic V6 with ETB.
My plan was a initial and final layers of 200gr and 4 layers of 450gr in between, with 1 extra layer of 450 in some curves.
For each layer i was thinking on doing the following  ->
for the bottom part of the plenum one across long sides of the and one on each shorter side with an extra strap of about 7cm wide to overlay the union in each corner

Will you do it like this or differently ?

 

That would be massively strong with that layup.  For a simple airbox over ITB's we produced in pre-preg, we used a single 210g and a single 450g cloth to give a 0.75mm overall thickness. 
You could do another layer of 450g or a layer of 210g on the inside if you wanted it particularly strong. As long as the plenum/airbox is not restrictive for airflow, there should not be any significant vacuum in it loading up the carbon.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

+x

 

Warren (Staff) - 11/18/2021 5:25:37 PM

That would be massively strong with that layup.  For a simple airbox over ITB's we produced in pre-preg, we used a single 210g and a single 450g cloth to give a 0.75mm overall thickness. 
You could do another layer of 450g or a layer of 210g on the inside if you wanted it particularly strong. As long as the plenum/airbox is not restrictive for airflow, there should not be any significant vacuum in it loading up the carbon.

Hi warren, thanks for the response.
Actually this engine is driven by ETB with restrictive inlet, naturally aspirated, there is vacuum generated inside plenum.
The first try with 3/4 layers of 200 gr collapsed the bottom part of plenum, thats why i upgraded to 2 layes of 200 and 4 of 400 gr.
what do you think ??
Note that i will not use prepag but rather hand layup with vacuum.
Somebody told me to also to reinforce the longs side walls with honeycomb but i would rather increase carbon thickness...
pic of the original broken bottom part.


 

Definitely more layers.  Probably 2-3mm thick.  In broad brush terms, carbon is similar strength to aluminium and a cast or welded plenum would likely be 3mm or thicker to handle decent levels of vacuum or boost. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

+x

 

Warren (Staff) - 11/23/2021 5:24:32 PM

Definitely more layers.  Probably 2-3mm thick.  In broad brush terms, carbon is similar strength to aluminium and a cast or welded plenum would likely be 3mm or thicker to handle decent levels of vacuum or boost. 

to be fair - the wall thickness of such a cast part is probably just as much dictated through manufacturing limitations.

Your part would however immensely benefit from a sandwich construction. With that geometry it would also be quite easy to manufacture. I would however use a rohacell or similar and not a honeycomb. That seems just like a struggle and end up heavier.

I make carbon plenums and intercooler piping for turbocharged race cars running 2-3 bar boost and in excess of 700hp - monolithic carbon layup for 2mm wall thickness. I use pre-preg, so for wet-lay I probably would consider going an extra 0.5-1mm thickness.

Your geometry won't be helping you here, flat walls will fail easier than walls with some curvature to them. So if changing the shape slightly and making new tooling to incorporate some curvature is an option, then you can save a bit of weight/material that way. Otherwise, your suggested layup sounds fine. You could also do a rohacell core as Lester suggested, but I do prefer to do these sorts of parts monolithic.