DrBoost
DrBoost Dork
4/15/10 9:58 a.m.

Not those cool pep-boys CF stickers you put on the side of a Focus but the real deal. I'm thinking about making a mold from a bowl from fiberglass then using that mold to make a CF bowl for a project. I've never worked with FG but I can learn, is CF vastly easier or harder to work with? Where would I go about getting, say a yard of the fabric?

Thanks guy and gals.

cghstang
cghstang Reader
4/15/10 10:06 a.m.

Working with Carbon Fiber is just like working with Fiberglass. Wear a respirator and long sleeves unless you like itchy lungs and arms. (I did and engineering co-op at a small composites place and layed up lots of stuff in carbon and glass)

Try boat repair shops for scraps of fabric.

oldtin
oldtin Reader
4/15/10 11:03 a.m.

Supplies and info - epoxy resin works better with cf than polyester resin.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/15/10 11:06 a.m.

I worked with a guy named Carbon McGillis once.

4cylndrfury
4cylndrfury SuperDork
4/15/10 11:13 a.m.

Best prices, customer service, and availability: http://sollercomposites.com/

VERY similar process to fiberglass. Pot time on resin is a bit less, and the resin is a bit thinner than FG resin, but otherwise very similar. Tape the edges of cut material to avoid fraying. Carnuba wax makes a great mold release. Youll need sharp shears to cut it.

Please take and post pics!

DrBoost
DrBoost Dork
4/15/10 11:16 a.m.

Ok so here's a more specific question. What I'm trying to do is make a bowl for a centrifuge and I'm wondering if it will be rigid enough. I can buy aluminum bowls (cut from billet) but they are about $500! CF is very rigid and strong but do you think a 8" bowl will handle about 3750 rpm with a few cups of oil in it without flexing and going all catty-whompus?

4cylndrfury
4cylndrfury SuperDork
4/15/10 11:19 a.m.

I can cast you a bowl

DrBoost
DrBoost Dork
4/15/10 12:30 p.m.
4cylndrfury wrote: I can cast you a bowl

Really, PM me.

wearymicrobe
wearymicrobe Reader
4/15/10 1:10 p.m.
DrBoost wrote: Ok so here's a more specific question. What I'm trying to do is make a bowl for a centrifuge and I'm wondering if it will be rigid enough. I can buy aluminum bowls (cut from billet) but they are about $500! CF is very rigid and strong but do you think a 8" bowl will handle about 3750 rpm with a few cups of oil in it without flexing and going all catty-whompus?

WE have ultrafuges that produce 100,000g with carbon inserts so 3750rpm at 8 inches will hold just fine.

Centrifuges are cheap and plentiful on www.labx.com ww.dovebid.com no need to reinvent the wheel so to speak.

benzbaron
benzbaron HalfDork
4/15/10 1:25 p.m.

My father does a lot of testing on carbon fiber and worked at an area where they laid it up for projects. They vacuum bag it. I think they lay it up and one of the main concerns for structural CF is the way the layers intersect. I guess the cloth is very strong one way but pretty weak the other way. They overcome this by changing the direction of the strong direction from layer to lay so the strong direction intersects either perpenpendicular or at and angle. Kind of hard to explain. I guess at his work they had a department where they digest the resin to inspect the fiber, sounds like a great job.

The only other thing I know if you need a special drill bit to drill into it, I think one with 3 flutes. Lastly carbon fiber dust if really nasty stuff and my father has scars in his arms from getting fibers in his skin.

96DXCivic
96DXCivic Dork
4/15/10 1:34 p.m.

I have worked with carbon fiber a fair bit. Like cghstang said if you are cutting wear a lot of protection. That E36 M3 inches. You do not need a special drill bit to drill but it will eat thru normal drill bits pretty quickly. I would use epoxy resin. I have used some U.S. Composites and West Systems resins both are pretty good. It depends on the weave of carbon fiber on which way is the "strong direction". The saturation of the resin and getting the correct mixture of hardener to resin is important in the strength of the material.

DrBoost
DrBoost Dork
4/15/10 1:55 p.m.
wearymicrobe wrote:
DrBoost wrote: Ok so here's a more specific question. What I'm trying to do is make a bowl for a centrifuge and I'm wondering if it will be rigid enough. I can buy aluminum bowls (cut from billet) but they are about $500! CF is very rigid and strong but do you think a 8" bowl will handle about 3750 rpm with a few cups of oil in it without flexing and going all catty-whompus?
WE have ultrafuges that produce 100,000g with carbon inserts so 3750rpm at 8 inches will hold just fine. Centrifuges are cheap and plentiful on www.labx.com ww.dovebid.com no need to reinvent the wheel so to speak.

Thanks for the links. Unfortunately those are medical 'fuges for spinning test tubes and what not. I'm looking for a disc type that I can introduce a steady stream of oil into to clean it. I have a home-brew that will work but the bowl is not going to work. I am hoping to make one on the cheap-ish. Those ones in labx and dovebid are expensive as well. The cheapest one I have found commercially available is just under a grand. I'm trying to grassroots it.

96DXCivic
96DXCivic Dork
4/15/10 2:00 p.m.

I have had a lot of luck ordering from US Composites. How big do these bowls need to be?

Tetzuoe
Tetzuoe Reader
4/15/10 2:02 p.m.
Giant Purple Snorklewacker wrote: I worked with a guy named Carbon McGillis once.

Invite him to bowling. /problem

hamburglar
hamburglar New Reader
4/15/10 2:05 p.m.

You guys are forgetting one very important thing about carbon and composites in general: fibre volume fraction. Essentially, you want to pack as much carbon in your structure with a minimal amount of resin. This is why vacuum bagging is better than just plain layup, you can squeeze more resin out of the part. It's also why moulding composites in a press is an even better idea. Then there's the whole porosity issue, and trying to avoid internal stress concentrations (read: bubbles).

Then there's selecting the proper resin for your application. Notwithstanding temperature or environment, the big factor is strength. If you use inferior resin, you might be better off with an inferior fibre (say glass) since it could be the weakest link in the chain.

For your application, since you're wanting to make something fairly structural, I'd suggest staying away from carbon as far as DIY goes. This isn't quite the same as making a body panel for your car. My point is: you may end up spending a lot of money and effort trying to get something to work whereas just using an existing (metal) piece would be cheaper.

To answer your original question, I have not worked with carbon myself, but have designed a few pieces...

96DXCivic
96DXCivic Dork
4/15/10 2:47 p.m.

Vacuum bagging isn't hard. If the part is small enough you can use a food saver. That works well but you will need breather bleeder material and peel-ply. If you are thinking about a plain wet layup, I won't bother.

4cylndrfury
4cylndrfury SuperDork
4/15/10 3:02 p.m.

Youve got PM

4cylndrfury
4cylndrfury SuperDork
4/15/10 3:05 p.m.
hamburglar wrote: You guys are forgetting one very important thing about carbon and composites in general: fibre volume fraction. Essentially, you want to pack as much carbon in your structure with a minimal amount of resin. This is why vacuum bagging is better than just plain layup, you can squeeze more resin out of the part. It's also why moulding composites in a press is an even better idea. Then there's the whole porosity issue, and trying to avoid internal stress concentrations (read: bubbles). Then there's selecting the proper resin for your application. Notwithstanding temperature or environment, the big factor is strength. If you use inferior resin, you might be better off with an inferior fibre (say glass) since it could be the weakest link in the chain. For your application, since you're wanting to make something fairly structural, I'd suggest staying away from carbon as far as DIY goes. This isn't quite the same as making a body panel for your car. My point is: you may end up spending a lot of money and effort trying to get something to work whereas just using an existing (metal) piece would be cheaper. To answer your original question, I have not worked with carbon myself, but have designed a few pieces...

Manually pressing with a proper mold and die is often an acceptable method of removing/managing/equalizing resin content between the layers as well.

hamburglar
hamburglar New Reader
4/16/10 11:42 a.m.

agreed on the manual pressing, its all about leverage right...

that being said, who want to bother making a proper mould for a one off part? I say stick to metal!

4cylndrfury
4cylndrfury SuperDork
4/16/10 11:46 a.m.

Yeah, metal is often easier for one off stuff. However, now that the good doctor has identified a market, perhaps investing in a decent 2 part press mold could be a lucrative venture!

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/16/10 12:33 p.m.

Here is why you should use steel: Massive fail

DILYSI Dave
DILYSI Dave SuperDork
4/16/10 1:55 p.m.

Be careful using a DIY composite if this thing is generating real forces. Would hate for you to have 1/3rd of a CF bowl imbedded in your skull next time you log on.

CLNSC3
CLNSC3 Reader
4/17/10 4:03 a.m.

I have a got a great book on carbon fiber fabrication...I will go find it and add the title to my edited post!

I have not started working with it yet, only because I do not have a suitable work area...

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