Bike lay-up

General Composites Discussions Composites Talk
#1

Just wondering if anyone has any information on lay-ups for carbon mountain bikes?

Heres a few pics of Santa Cruz bikes cut-aways, interesting if nothing else:
http://www.pinkbike.com/news/santa-cruz-carbon-v-10-eurobike-2010.html
http://www.ecofriend.com/entry/santa-cruz-bicycles-debuts-carbon-fiber-nomad-c/

I see a lot of fibre layouts at 60 degs to the axial direction of tubes. Does anyone know what the layout is like throughout? I know at certain areas, the loading scenarios are multidirectional, hence the plain weave, but I would have expected a lot of UD axially along tubes as well as prob 30 degs, not 60 for torsion, maybe balanced with some 0/90. Any thoughts?

#2

Holy crap, they switched the V10 to all carbon? ftw!!!
Now, as for the layup. Who knows what is on the INSIDE stack. The outside might be 0/90 for show, and the inner layers might be something…but to know exactly how much PW or Uni is in one area, and what orientation, is only known to those who build it. Every bike will be different, along with every brand of carbon bike. It’s nice to see the thickness changes in the V10 photos, to know where to build up at least!

#3

you won’t be able to tell anything from looking at those cut-aways except where to put more or less material. It wouldn’t help even if you could because you don’t know the material characteristics. You will also be making your frame differently i. e. wet lay-up on foam instead of prepreg with bladder mold.
If you want to build a MTB for yourself, start by looking at the forces in different areas of the frame and make test sections. Try and break those with a defined force equal to what you would expect plus a safety factor. If it holds, increase your safety factor until it fails. When you’re sure you’ve got it right, make a frame and test again.
Your first frame is for destroying. Your second (if you’re lucky) will be for riding.
Have fun but protect your teeth!

#4

Ah yeah, I fully appreciate that the laminate orientation in those photos is total guesswork other than the surface layers, just wondering if anyone had some inside info :slight_smile:

I have a good idea of layups that I like for bikes and ones that have worked for me ( see http://www.comeraghcomposites.com) but just thought I would pop the question. Took it to a DH race last weekend and it got a serious thumping!

#5

I’m building a bike for my senior design project… the majority of the layers will be laid up axially. I’ve read that it is important to have at least 10% of the lay up schedule in each direction and no more than 4 layers of the same thickness in the same direction stacked… if that makes any sense. Other than that… do you know finite element method:o?

#6

Sweet jeebus, they’re doing 'em in cf now? I’ve always had a serious thing for the V-10 and Nomad…but the Switch and Slayer will have to do for now :wink:

I’d guess that they’re doing the frames with bladder moulding. To me, closed moulds would be the only good way to position metal inserts quickly and reliably in a mass production scenario.

Bladder moulding would be difficult to do on a diy-ers budget, but not impossible.

I’ve had a cf frame “on the go” for a few years now…I infused the seat tube and haven’t gone any further. I was planning on building the bike using braided and uni sleeves over a cnc machine’d foam core. Lately, though, I’ve been toying with the idea of making short lifespan bladder moulds using MDF. Bladders could be something as simple as inner tubes. At the very least, I’d like to try this for some of the lugs.

#7

fleisch, that sounds logical but preumably only applies to thin laminates? Im not using FEA, just lots of field testing, not a fan of FEA, so its good old practical testing and a bit of logic for now!

I have worked with MDF moulds before and they are nothing but a nightmare in my opinion! Always breaking in places, not easy to finish and seal, etc. Just dont like MDF :slight_smile: