Bike Forums - Does the type of carbon really make a difference?

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- - Does the type of carbon really make a difference? (https://www.bikeforums.net/road-cycling/450351-does-type-carbon-really-make-difference.html)

Quote:

Originally Posted by paul_858 (Post 7211150)

http://cchanphotography.com/biking/c...s/dsc_1001.jpg

Can't quite tell from the picture, but what kind of finish is that on the tubes? Unfinished? That's the design? Chances are they've mixed a fine charcoal colored powder into the resin to give it that dull matte look. Possible they created a CF tubing slightly oversized during manufacture, then sanded down to the final diameter.

Sounds to me like the quality of CF frames has too many variables, much like a cell phone contract,to really follow what your buying.Who honestly does a physical study on the fiber +resin content on there new weenie machine?I assume the quality changes with each frame made in a line of similar models.
You can bet your sweet chamois cover the manufactures like it this way,the "ole mushroom treatment".

Quote:

Originally Posted by jrennie (Post 7210868)

Custom builders bikes are also tuneable for different ride feel to user requests. I had very specific requests in my build and Brent selected the material best for the application. His tubes are unidirectional and come from Edge composites in Utah then hand wrapped instead of mono or lugged
http://i80.photobucket.com/albums/j1...s/000_0368.jpg

Brent? Which Brent are u referring to, Brent Steelman? Just curious that’s all .

sorry, Brent Ruegamer. www.ruesports.com

Quote:

Originally Posted by BananaTugger (Post 7209289)

M30S, T-700 and T-800 are simply manufacturer designations for that particular weight and modulus of carbon fibre.

What is more important to the use of carbon fiber in bicycles are the exact values of its weight, strength and modulus.

The Modulus of Elasticity (I'll just call it modulus), is how much the material stretches when stressed. This value is directly related to how stiff the material is. A high modulus material like Toray's M40 carbon fiber is very elastic and resilient compared to Toray's M30S carbon fiber, which is much stiffer and stronger in tension and torsion. Because the M30S fibers are stiffer, they are more likely to break when they are stressed to much. The M40 fibers will continue to stretch while not breaking when they reach their threshold. It is possible to deform high modulus fibres however.

Modulus is measured in GPa (Gigapascals). High Modulus materials are in the 250-350 GPa range, while low modulus/high strength materials are in the 100-250 GPa range.

Using a high modulus material reinforced by a low modulus/high strength material in certain areas is how most frames are constructed.

Using high modulus fibres for the seatstays will allow them to bend and give a little when they are compressed. Conversely, using low modulus/high strength fibers in an area that sees a lot of torsion and tension, like the bottom bracket or headtube, will make that area of the frame stiffer than the high modulus material would.

I've found that on a Taiwan bike manufacturer website. Even if there isnt all different type of carbon, it give's us an idea how it works

http://www.dynamic-bicycles.com/fron...ategory=300429

Here's also a link with good pics showing & explaining the difference between 1k 2k 3k 12k and UD (uni-directional)

http://www.storckbicycle.com/usa/ind...&s=carbonfiber

Quote:

Originally Posted by BananaTugger (Post 7209289)

so high modulus is more elastic and low modulus is more stiff.

i've seen descriptions of low density and high density. which one is better and used in the more expensive bikes?

Quote:

Originally Posted by coasting (Post 9545523)

so high modulus is more elastic and low modulus is more stiff.

That's what he's saying, but he's incorrect. Modulus is stress/strain - higher modulus is more stiff.

Unfortunately, comparing carbon fibers of different bikes tells you very little about what you really want to know - ride characteristics, stiffness, geometry, fit, etc..

Quote:

Originally Posted by BananaTugger (Post 7209289)

The Modulus of Elasticity (I'll just call it modulus), is how much the material stretches when stressed. This value is directly related to how stiff the material is. A high modulus material like Toray's M40 carbon fiber is very elastic and resilient compared to Toray's M30S carbon fiber, which is much stiffer and stronger in tension and torsion. Because the M30S fibers are stiffer, they are more likely to break when they are stressed to much. The M40 fibers will continue to stretch while not breaking when they reach their threshold. It is possible to deform high modulus fibres however.

1) M40 has a higher modulus than M30S - http://www.toraycfa.com/pdfs/Torayca...yDataSheet.pdf

2) You say that M30S is "much stiffer and stronger in tension and torsion". Incorrect. M30S is less stiff, but stronger (see above). It is meaningless to say that it is stronger in torsion; the individual fibers are not stressed in torsion.

3) "Because the M30S fibers are stiffer, they are more likely to break when they are stressed to much." This is incorrect. All carbon fibers are brittle. They do not have any meaningful plastic deformation.

4) "The M40 fibers will continue to stretch while not breaking when they reach their threshold. It is possible to deform high modulus fibres however." I am not sure what you mean by "their threshold"; it seems you are getting confused with the behavior of metallic structures (yield and plasticity). Carbon fibers do not plastically deform; they break when their threshold (ultimate strength) is exceeded.

Quote:

Originally Posted by BananaTugger (Post 7210009)

If a builder were to make a one-off, market practicality-be-damned frame of supreme lightweight and stiffness, they would use very expensive pan based T-800 unidirectional carbon fibre manufactured by Toray.

This stuff will run for about $2500 for 10 ounces or so.

A few manufacturers, or more precisely, frame builders, use this material in their frames, such as Spin, Crumpton and Storck.

Giant also purchases raw T-800 fibres from Toray and weaves them into a 1K pattern for their TCR Advanced frames and forks.

The unidirectional fibres would be layed into the mold with the fibres running along the length of the frame tubes.

This would make for a very stiff, and depending on the method of molding and construction, very light frame.

I think my Cyfac Gothica is made entirely out of T800 fiber, and the frame alone cost me over $6600.