Carbon - Vibrartion damping and Strength

[xak1]

I saw an old topic where there was an argument on if carbon really have better vibration damping than alu or titanium.  I have spoken to some highly qualified materials specialists at one of our universities.  I will try and explain in non-scientific terms, as I myself struggle to understand.

 

As carbon is a composite material, a lot of what is claimed wrt carbon (e.g. strength, flexibility) is actually dependent on how the carbon was composed (there are different processes, with different properties), but in general, it should have better vibration damping than aluminium.  The stucture of carbon basically consists of a hard molecule (skeleton) surrounded by some softer molecules (the resin binding it).  That is the reason why it will not break in a straight line, as when it breaks, it will turn away when it gets to the hard molecule, and follow the route of least existince.  As a result of this structure it also should have better vibration damping, as the impact will be absorbed better by the softer parts.

 

A case in point is tennis racquets, where aluminium was short-lived, as it caused tennis elbow as a result of the low damping capacity of aluminium.  See http://www.azom.com/details.asp?ArticleID=216.

 

I also asked about strength, and the opinion (they have never been on a bicycle) is that the welding process of aluminium will cause weakness in the frame - if one then uses the adage that a chain is just as strong as the weakest link, they feel that if a carbon frame is designed right, it could have superior strength.  The one weakness is that one has to design very carefully, as the strength is more uni-directional, but this is overcome with using different layers in different directions.  Carbon is also more brittle, therefore the need to keep to torques specifications - falling, in general, will, however, not cause a similar stress to this. i.e. crushing.

 

I suppose one can debate endlessly about this, but in the end when you buy a carbon frame or component, one must make sure that it is from a company that has a solid reputation in this field (tested by cyclists all over the world) - interesting is the fact that if you go on www.mtbr.com, one can pick up some manufacturers which carbon frames seem to break regularly, and others that never get a mention wrt breaking - it therefore seems to be much more in the design and manufacturing technique than in the material.

[Racer X]

Very illuminating, took me a few reads though

[GoLefty!!]

with a existentialism thrown in for good meaure