# Materials with a high compressive strength to weight ratio

We know about extremely strong materials such as carbon nanotubes. However, this is only in tension. What are some high strength-to-weight materials (both available and hypothetical) in uniaxial compression?

Such a material would be useful in supertall structures and vacuum airships.

Of my research, PVC pipe seems to be a good bet at 100MPa and only 1.3 g/cm^3. However, this is still inadequate for a vacuum airship.

Beryllium is also a likely candidate as it is 1400MPa and only 1.85 c/cm^3, making it doable in a vacuum airship. However, it is very toxic to work with (I don't know if bulk beryllium is safe) and expensive.

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 Odd thought that might make this easier to find: the speed of longitudinal pressure waves (sound) is the bulk modulous/density (which is close to what you want). Perhaps you can find a tabulation of the speed of sound in colids and simple look up the ration you want for the strong candidates. Added: Ah...it is the P-wave modulous over density that you want, which implies that the speed of sound is a good figure of merit here. – dmckee♦ Jan 22 at 2:14

Relying on the claims I made in my comment about the relation between some of the moduli and the speed of pressure waves, I tried searching the web for tables of the speed of sound in solid materials, and found (as I thought I recalled) that diamond is clear winner amung traditional materials with $v_s = 12,000\text{ m/s}$.
However, WolframAlpha says the highest is $18,350\text{ m/s}$ for "carbon" without saying what bulk material. I woud assume nanotubes or graphene.