yezard

i want to build a carbon fibre frame and want some advice about how to go about building it.
i have looked at many websites out there which are very helpful but from what i gather carbon frames are imesly strong (if built properly) but have poor impact strength and if you hit a log u render the frame useless.
so it got me thinking if i can use both carbon and kevlar for a frame, the carbon will give the frame its strength whilst the kevlar should aid in some of the impacts that may occur.
i have used carbon fibre in the past and will be vacuum baging my layers of carbon to consolidate the layers properly

i know many out there will disscourage me and say building a frame is not worth it but i still want to try
any ideas whether this will work?

unterhausen

I had the same thought 30 years ago, so it's not without merit. Kevlar is used occasionally, but I don't think it's that useful. It's not going to stop a point load from crushing the tube, which seems to be the main failure mode of carbon in a crash.

Canaboo

Carbon tends to crush because it is not supported from the inside. Building a bike using a strong impact resistant marine foam as the core and a kevlar/carbon combo as the shell should greatly alleviate that. The core being left in place can offset the slightly greater weight. It takes less carbon etc if there is a core.
You can buy carbon/kevlar cloth that is woven together. Some carbon bikes do include kevlar, although it seems pretty rare.
The Cheetah TT bikes are a carbon/kevlar mix.
https://www.catbikes.ch/

yezard

thank you for your advice.
yes i am thinking of laying my carbon/kevlar cloth over a foam core i will build a jig first to align every thing and then fiberglass everything in place. i am planing to vacuum bag the frame to eliminate excess epoxy and consolidate the layers properly. as for the carbon i will buy carbon tape (unidirectional), carbon cloth (twill or plain) and a kelvlar carbon woven cloth all probably around 200-300 gsm i am planning to lay the cloth in different directions-is this ok or would a different weave pattern be better i have used multiaxial in the past and i really liked it since it does not snag or deforme when wetting out the only problem is that i can not find it anywhere
does anyone know any good sources of carbon fibre cloth?

space_mage

It seems to me like no major manufacturers are using kevlar as a reinforcement. I ride a Look KG86 which has kevlar reinforcement but they don't do that anymore. I did read (somewhere?) that it has good shock/vibration absorbing properties, which makes me think about using a couple plies in the seatstays and seat tube. I'm in the process of research and design for my own composite frame and I'm not sure if the kevlar will really be worth the bother. I've also read that it's a lot harder to wet out compared to carbon.

yezard

ok thanks space_mage i may re-consider using kevlar
for the time being though this bike will have to be on hold since i think more research is required and i need to find a good source of carbon fibre
again thanks for the info

Shadow7874

uscomposites sells carbon/kevlar hybrids. Ive never used it personally (nor do i know much about it at all) but a few guys in the jet ski industry have used it and say its good stuff. And considering the type of jet skiing they do i would trust it.

https://uscomposites.com/hybrids.html

miamijim

Miyata used a very thin base aluminum tube for their carbon frames back in the days of early mass production.

https://4.bp.blogspot.com/_whtVpXkKwl...0-h/img186.jpg

space_mage

The miyata tube thing is really cool! That's an interesting way to avoid using a mold if you're making round profile tubes.

ultraman6970

always you can get a broken AL frame, make zillions of holes to it to take some weight off the frame and use that as a core for your frame?

Seattle Forrest

I have one of these:



It's carbon/kevlar, around a foam core - the blades and the shaft both. It holds most of my body weight when I get in and out of the kayak, and while it's been in impacts bad enough to break pieces off the ends, on the whole the thing is in great shape.

I think the carbon kayaks have kevlar in the mix, too. Mine is resin, so I can't say much, except that even sea kayaks ( as opposed to river ones ) are expected to bottom out sometimes. Carbon bikes are usually pampered, never crashed or dropped, etc.

yezard

wow thanks for that, the Miyata thing look very interesting but i cant see me replicating that at home, as for the carbon kevlar hybrid i may give it a go i am in the process of building a cnc machine so if all goes to plan i am hoping to machine a very accurate foam core and then lay my fibres on top
that looks soo kool 'Seattle Forrest' carbon fibre looks so great there is really no comprimise for looks and performance

ultraman6970

Hmm what about honeycomb carbon structure? U get the crash resistance using this, then wrap it big time with uni carbon tape. Or use honeycomb as structure, it might be stiffer than foam and might save time in the cutting dept, or spending money in a cnc cutting machine?

Too many ways to do the same i guess

yezard

yeah thats a good idea 'ultraman' but i dont think i have the patience to make a honeycomb stucture- as for the carbon honeycomb structure do you mean something like this https://www.bmeres.com/c-thruframe.htm
as for the cnc machine i want to build it anyway- but im hoping that i can machine some interesting shapes that i can build my bike around so i can truly customize the bike's look
your so right there are truly many ways to build my bike but i want to build it strong becuase i can do some very reckless things sometimes when riding and the last thing i want is coming home carrying pieces of my bike-lol