How hard is it to custom fabricate parts out of carbon fiber? Are there
special tools required? Specifically, I am interested in trying to make my
own CF seat base.
Any suggestions on where to start? Or is this sort of thing generally
considered out of the reach of hobbyists?
-mg
Depending on how exacting your expectations are, carbon fiber can be a very accessable media. If you forgo vaucum baging for punctured tape, and use a disposable/consumable blank or very simple mold, and aren’t real conserned about a perfect finish, then the process can enter the realm of ‘easy’.
I’v only done research- but lots of it. For a while I was considering production… anyway, here are a bunch of links (I’m too tired to pontificate- somebody else pick up the mantel).
Of special interest will be David’s CF bike that he made in his garadge.
Night,
Christopher
carbonaluminium.zip (5.87 KB)
Couple links, specificly
Check out this one:
Small Scale Modeling of CF Parts
and
What you realy want to know- CF hand lay-up basics.
Sleeeeeep,
-C-
Michael-
Do you want to do a one off, or production? We should schedual an AIM session or ICQ to field questions and ideas.
Ok, I’m shutting this machine down. Real-ly.
-C-
Carbon Fiber is not too hard to get or use. I’ve been reinforcing my unicycle seats for years with glass, carbon, or kevlar, long before the carbon fiber base came out. I’ve also created a replacement seat bumper for my very old style miyata seat (which you can’t get replacement parts for anymore).
Anyways, pretty much all you need is some carbon fiber (or other choice of fiber such as glass or kevlar), some resin, a mold (or object to reinforce), a few tools to smooth out the finished product, latex gloves (as Dylan Wallinger would be sure to mention), a mixing cup, a big plastic bag, and a tub of water.
To make a mold you can use pretty much anything that you can use to get into the shape you want, whether it be wood, foam, fiber glass, wax, plastic, etc. Just make it the shape needed and put some mold release and wax on it so your finished product will separate from it.
To make the product, just cut the fabric carbon fiber, apply the resin to it (don’t use too much), and then lay it on the mold. Then put it in the plastic bag and dunk it in the water (which is the cheap and easy way to do a vacuum on it to get all the air out and hold it in place). You may want to use a rubber band to seal the bag as you do not want water to get in. When the piece is in the water, you’ll want to work with it to get everything in place and squeeze out some of the air and extra resin (if any). Let it cure for a while, then take it out, release it from the mold, and sand/grind, chisel anything to make it smooth.
Note: Carbon fiber is not very good to breath the dust from or to touch with bare hands as the slivers are sharp and well, it’s just not good. You may want to practice first with glass or kevlar.
Three words:
prepreg
mould
oven
Making something like you want by hand layup is easy enough as the others mentioned, but the mechanical properties are total junk. Your void content is huge, and your fiber volume fraction can become low. Not to mention the enormous mess that ensues. If you can score some prepreg, you are in business. Only a few things to contend with. You must keep it in a freezer or you have a really short shelf life (1-2 weeks vs 1-2 years) Also you need to have a bleeder and breather and pull vacuum to get good compaction and good volume fractions. I suppose you could use a female / male mould combination with clamps to avoid this. To prepreg’s favor when it is done right you have butt kicking fiber volume fractions, you can make parts much more quickly and with much less mess, you have awesome mechanical properties and it will be the lightest weight. Good luck.
-gauss
How 'bout 3 more words:
Expensive
Intensive
Expensive
I don’t think making aluminium molds and expansion bagging pre-preg in an oven for ultra low resin to carbon ratio’s is really a pedestrian home grown project. Take care when wetting out the fiber and design your form so that puncture tape works effectively and you can get reasonably void-free low resin level parts at a much much lower start-up cost; the technique has worked well for custom cycle and aircraft manufacturers- let alone a sadle base.
-Christopher
Yes, people always say that prepreg is expensive. In fact it is not as expensive as you think. It used to be dreadfully expensive, but now it is more reasonable. What used to be expensive was the materials and the moulding. The material costs are much lower now and also, there is no longer the need to use things like autoclaves when making prepreg (thank God). You can now do just as well with an oven and a vacuum pump. The thing that gets you when you make composites is the consumables. This isn’t a big issue with the hand layup. If you plan to make one thing one time then by all means use hand layup. If you plan to make iterations of a design, think you will make things in the future, or are concerned about quality, then consider alternatives, but this does mean investing in some things As Rysling Pashley mentioned hand layup is used for many things. There are an array of reasons that I won’t get into and they vary among applications.
If I were going to make a carbon fiber seat base though, I would use prepreg. The major setback is that you must buy a fair quantity and must have a place to keep it. This said, plus access to a vaccum pump, and you are making composites for a long time. As for a mould, you can do as you like, but I surely would not use an aluminum mould. I never have except for flat plates. In fact there is a really cool way to make an exact mould of an object for cheap, but it again involves use of a vacuum pump. Also don’t bake the stuff in your better half’s oven. If you use epoxy for a matrix, it poses a serious health hazard Anything that is exposed to uncured epoxy needs to also be cooked in the oven, or thrown away. You can make a really good oven out of light bulbs and insulation $100ish. Basically, with a little creativity you can make high quality prepreg parts for a reasonable cost if you know what you are doing.
-gauss
Re: Working with carbon fiber
— Gilby <Gilby.901aa@timelimit.unicyclist.com>
wrote:
> > reinforce), a few tools to smooth out the finished
> product, latex gloves
> (as Dylan Wallinger would be sure to mention), a
> mixing cup, a big
im not positive, but im assuming your mistaking me for
dylan. thats ok though.
later,
=====
Nick Cegelka
NickLikesFire AIM
Do You Yahoo!?
Yahoo! Health - Feel better, live better
Re: Re: Working with carbon fiber
Yeah… Sorry, I’m bad with names, especially with the added complexity of having real names hidden behind screen names and such.