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Good Damping

Carbon bicycle frames have the unusual property that they are superior to aluminum frames in high-frequency absorption. A cyclist on a carbon-frame bike will feel tarmac chatter far less than on an aluminum-frame bike. The frame yields at these high frequencies, isolating the rider from them.

High Strength

Yet carbon frames are also famously solid. A carbon-frame bike remains solid underneath a cyclist using arm muscles, efficiently transferring all their power to the drivetrain with little perceptible frame bending.

Question

How can a material be good at damping, yet also be strong?

Credit for this phrasing of the question goes to TimWescott.

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    $\begingroup$ I don't see why you think they are related unless you associate damping with soft rubber foam. I am also not sure if "strong" is necessarily your intent. Are you sure you don't aren't wondering about stiffness/rigidity which is different than being strong? $\endgroup$
    – DKNguyen
    Apr 14, 2023 at 22:02

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Calling it "yielding" is incorrect because yielding is a permanent deformation. The damping you are speaking of is how lossy the elastic deformation is.

It should be related to the molecular structure of the material when it deforms against itself and how much energy is lost when that happens. If little energy is lost it can ring like a bell. If a lot of energy is lost it doesn't (with that energy being converted to heat...sort of like a solid's equivalent of viscosity I guess).

As you can see this is separate from the amount of force it takes to deform/bend something. If it takes a lot of force to bend but it dissipates a lot of energy during deformation it will still be quite solid yet damping.

If it does not dissipate a lot of energy when deforming, it is like a coil spring. We all know if deform a spring and release it, it keeps on springing which is why springs aren't used alone for suspension system; You add dampers to dissipate the energy.

I can't think of an example off the top of my head of something that is less rigid but has low energy loss during deformation. Likely because with less rigid materials it is easy to apply enough force to enter the non-elastic regions.

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The trick is in the angle of winding the layers of carbon fiber lamination, or layup.

A tube of the bike could possibly be wound up of layers of 0 , 20, 45 degrees, and even different materials having the optimal shear, tensile modulus appropriate for that angle.

So, for example, much of the stiffness of the tube against, say, torsion is due to the 45-degree layup.

Furthermore, because different materials strain differently, there is inherent energy absorption during deformation.

Some of the winding gets altered and improved after stress tests, even along the length of the tube, say when the tube is attached to the saddle.

A carbon fiber layup example showing the orientation of layers. The image shows a total of 8 layers of varying carbon fiber directional layup. Image from Velocite (Velocite, 2015)

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tube

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