Inspired partly by the discussion on vacuum for lighter-than-air craft and my love of sci-fi robots, I have to ask: what is the maximum theoretical strength for materials?
In asking this, I’m assuming the laws of nature do not permit an infinitely-strong material, no matter what kind of unobtanium you build it out of. At the very least, compression forces can eventually turn your material into degenerate matter or black holes, but I’m sure the practical limit for real materials is much, much lower than that.
If the answer would be different for compression vs tension vs other measures of strength, I’m curious about any types we can put numbers to.
Feel free to include theoretical materials that might exist if we knew how to make them (things made out of elements we don’t have today, or Trek-style plasma fields or whatever, as long as its generally believed something like that could exist).
Correct. I think I’m right in saying that for real objects in the universe that have quantitative values about them, those values cannot ever be infinite.
The thing about “strength” is that materials are a lot like chains, only as strong as their weakest link. You can try to calculate the strength of a macroscopic material based on its atomic properies, but that will often be a massive overestimate. When they first tried to calculate the strength of metals based on atomic theory, in terms of shear strength required to plastically deform them, what they got was values of around 10,000 times the observed values. This was because as crystalline structures any imperfections in the structure would act as a weak point. These “dislocations” are always going to be there, and they are the reason that heat treating changes the strength of metals. The strongest thing possible (at least in tension) would probably be something like a carbon nanotube, but once again any structural damage on the microscopic level (by chemical reactions with the atmosphere, stray high energy particle messing up an atom, or even just bad “luck” with a weaknesses being formed by thermodynamic type jumps) will greatly weaken it.
The answer is certainly different for different materials. The highest compressive strength of any material would be the stuff of neutron star cores, but its shear strength is zero, being a superfluid.
This exactly correct. The “strongest” real world material would probably be a absolutely perfectly structurally uniform crystalline material, possibly some diamond like variant of carbon. Good luck manufacturing that in useful shapes and sizes.
At least as far as we know, the binding energy of molecules sets an upper limit on how strong a material could be, You can measure how much thermal or chemical energy is needed to break a bond and extrapolate that to an ideal maximum which as pointed out upthread we’re unlikely to ever actually see.
The only way a material could be stronger would be if it were held together by something other than the electron shells of atoms. If Nature wanted to really surprise us, it could turn out that there’s a way of creating stable chains of nucleons or quarks held together by energies comparable to the binding energy of an atomic nucleus. In the absence of any evidence for something like that, it’s chances hover around zero. ETA: it’s beyond my math skills but I wonder how strong a substance would be if 90% of it’s mass was binding energy.
Wow… 10,000 times is actually more than I would have guessed.
The presence of imperfections and real-world constraints is partly why I’m focusing on the theoretical strengths. If a metal/crystal 10,000 times stronger is theoretically achievable, then it would seem that we have a lot of room for potential development, even if that development is incrementally a few percent at a time.
Well for a metal, theoretical strength without dislocations is about E/15 (E is the elastic modulus). Just comparing that with actual strength of a random metal on www.matweb.com , it’s about 300 times as strong as the normal strength.