what is the difference between carbon fibre and fibre glass?

Discuss light weight issues concerning mountain bikes & parts.

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Stylomilo
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Joined: Tue Nov 11, 2003 11:14 pm
Location: Singapore

by Stylomilo

im trying to make my project plan in making fibre glass frame. but i just need to know what is between in both of them. :D

thanks :D :) :P :o :lol: :twisted:
crashman
Crashman like crashing, feel the rythem and ride.

nikh
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Joined: Fri Jun 27, 2003 8:05 pm

by nikh

I would try doing some research on fibre glass before you even think about using it.

The internet is full of wonderful information, I tend to use Google a lot.
PLAY DARTS! *WARNING* MUST HAVE A SENSE OF HUMOR TO PLAY!!!

by Weenie


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Stylomilo
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by Stylomilo

yeap. find this website interesting but i still dont understand. :cry: Seems complicated.

http://www.bme.szm.sk/
http://www.bme.szm.sk/carbonframe.htm
Crashman like crashing, feel the rythem and ride.

nikh
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by nikh

He's using carbon fibre not fibre glass.
PLAY DARTS! *WARNING* MUST HAVE A SENSE OF HUMOR TO PLAY!!!

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Frankie - B
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by Frankie - B

those articles are amazing! :shock:

Can't help you with the fibre glass question though. Why don't you mail this fella?
'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'

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Ivan
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by Ivan

The carbon fibre we know is a composite material made of carbon fibres and epoxy resin. Fibre glass is a composite material made of glass fibres in a epoxy resin. Compared to carbon fibres, glass fibres have a much higher strain. This means you can elongate them more before they brake. However, carbon fibres can take a much higher load at yield (max. load) and have a much higher E-modulus then glass fibres, so carbon fibres are stiffer.
Glass fibres:
Max load: 1700-3500 MPa
E-modulus: 71 GPA
% strain: 2-5

Carbon fibres:
Max load: 1500-6000 MPa
E-modulus: 200-700 GPa
% strain: 0.5-2

Keep in mind that not only the fibres are important for a composite material but the resin is also very important.
I have much more info about this but i do not wish to share this on the net, PM me if you need more info.

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Stylomilo
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by Stylomilo

wow Ivan. thanks for sharing your useful info. im glad to hear it. :D Not only i project my frame but v-brakes as well. :twisted:
Crashman like crashing, feel the rythem and ride.

DeepWalletDave
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Location: Los Angelas

by DeepWalletDave

Glass fibers are made from silica derived extrusions, and carbon fiber, at least eh higher quality fiber, is, now you're goign to lvoe this, as I have it comitted to memory so hopefully one day in my life I could wow somebody...it is made the the pyrolotici degradation of polyacrylonitrile. PAN for short.

Your frame will weigh a ton. Most manufacturers use prepreg, which is an abbreviation of preimpregnated, meaning the fibers are already laid up with the right amount of resin in it, and it is refrigerated in rolled sheet form. Next comes molds that costs tens of thousands of dollars. Fiber sheets are laid over bladders tubes, then this is set in half of a mold, the other half is placed together, then the bladders are inflated to conform teh carbon sheets to the mold shape. Then the whole system is heated in an oven and cured. Sheets of the carbon fiber come in various fiber orientations, such as straight, crow weave, cross harness, satin-8, unidirectional, etc.....these are all employed and based upon finite analysis CAD-CAM calculations, the fibers and weave styles are layered as needed.

All fo this is really beyond the expertise of the average hobbyist without a huge investment. If you figure what your time is worth in money doing what your job is, if you took that money and bought a carbon fiber frame, you would be better off.

nicrump
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by nicrump

Fiberglass is for fishing rods, boats and surfboards. Stick with Carbon fiber and two part epoxy resins. If you want to “one up” that masterpiece of a frame you referenced, spend some time researching various processes for “compacting” fibers and “evacuating” air and excess resins. Take that frame one step further, engineer the laminate so you can “wash” out the foam core and make a lighter frame.

If you are going to build a frame and don’t want to do a face plant, research and learn these topics before trying to build a frame. Contrary to opinion, its not rocket science and only slightly more difficult than baking pastries. Just requires some understanding, skills and a steep learning curve.

1. Fiber, K count, weave’s and non weaves (uni)
2. Epoxy resins, how they cure, are they the right mechanical properties for the fiber and load and what are their service temp ranges.
3. Fiber science, learn where the strength is in the fiber and how to create a strong “isotropic” laminate of multiple plies of various orientations.
4. Compaction compaction compaction. And air evacuation
5. Resin fiber ratios.

I have said enough, get going and learn.

nicrump
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by nicrump

p.s., in reply to DeepWalletDave,

Image

This was my first engineering prototype of a full carbon frame. It weighs 1170 grams and rides pretty nice. I made it for well under $600.

It’s not a great representation of what I do now as I have improved on it dramatically. But it shows that someone without the million dollar resources (hobbyist) could make a pretty nice carbon frame if he puts his mind to it.

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Bruiser
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by Bruiser

How many building hours would that frame require?

Do the larger builders have a mechanical process to build the frames on mass?

Cheers

Brian

nicrump
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by nicrump

That first frame had about 20 hour of actual hands on. But I was already a skilled framebuilder at the time. so jig set up, mitering and so forth was easy.

Most of the Asian bikes are bladder so there is a lot of fiber placement into molds. There is technology for automated fiber placement but I seriously doubt its used in the bicycle industry as its very expensive and for large scale. By that I mean huge parts like jet fuselage sections or jet engine cowlings.

I am willing to bet most Asian builders hand place fiber into the molds. Labor is cheap for them.

I am sure at some point in the near future it will be more or less automated but not till the volumes justify it. As it stands now, carbon is still a very low percentage of the total of bike coming out of Asia.

by Weenie


compositepro
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Joined: Tue Apr 06, 2004 10:45 pm

by compositepro

check here this is how most the guys do it

but not all we have other tricks of the trade and materials

http://www.closedmold.com/RON%20SAMPE%2 ... /frame.htm

http://www.closedmold.com/
cp

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