# What is the strongest and lightest material?

I have heard titanium is the strongest and the lightest material. It is used for my glasses' frame. Is it true that it is the strongest and the lightest as well?

Strongest, the biggest forces can it bear without damage or breaking $$\frac{Newton}{m^2}$$.

Lightest, the least weight of a certain volume of material $$\frac{kg}{m^3}$$.

i.e.: a material is quite strong to bear some load, but also heavy at the same time. Another material is light enough, but can not bear any load. So, what I am asking is what is the strongest material but lightest as well.

• It's very unclear what you mean. For example balsa wood is more than 30 times "lighter" (less dense) and twice as strong weight-for-weight, compared with titanium. But it's not a material you would want to use to make either spectacle frames or parts of jet engines! Spider silk is even "better" than balsa, and Kevlar is much better than any of the above. Commented Dec 28, 2018 at 0:41
• google on "strength-to-weight ratio", you'll get a list of these. Commented Dec 28, 2018 at 1:05
• Please see this answer. It gives you a nice graph: engineering.stackexchange.com/a/490/33
– hazzey
Commented Dec 28, 2018 at 1:55
• If din't the explanation in the link suspected duplicate, there is no answer for the question. But however, that chard gave detail info of every material, what is their density and the their strength. Commented Dec 28, 2018 at 2:38
• Try looking at magnesium
– Fred
Commented Dec 28, 2018 at 3:26

## 3 Answers

Your question does not have a definitive answer, as the lightest material known is far from the strongest. On the contrary, there is a correlation between density and strength, meaning that in general denser materials are stronger than those that are less dense.

You might want to look in to Ashby diagrams, a plot where two properties are plotted against each other for many materials. In this case a Strength-Density-Diagram would be advisable.

On this site, you can find a variety of these plots.

A second more "numeric" might be to look up the breaking length of materials, which is a theoretical calculation for how long of a bar you could make out of a certain material until it fails under its own weight. There are some astonishing numbers.

The calculation is pretty easy, You get the force exerted by the bar itself $$F_T=\rho\cdot A\cdot g\cdot L$$, where $$\rho$$ is the density, $$A$$ is the cross-sectional area, $$g$$ is the gravitational acceleration and $$L$$ is the length of the bar. On the other hand you get the maximum force the bar can support $$F_R=R\cdot A$$, where $$R$$ is the maximum bearable stress (i.e. ultimate tensile strength, UTS). If you set the forces equal you get $$F_T=\rho\cdot A\cdot g\cdot L = R\cdot A = F_R$$ As you can see the area cancels out and if you solve for $$L$$ you get $$L=\frac{R}{\rho\cdot g}$$ which means the breaking length of a material is only defined by its UTS and density (assumed $$g$$ is constant).

There's a neat table on Wikipedia on breaking length / specific strength (which is just $$=\frac{R}{\rho}$$) but there surely are other sources as well.

If you are asking for 2 different materials, the lightest and the strongest one, well...

The lightest material is hydrogen gas (2g/mol, or 2g/24l at normal condition). The lightest pure metal is lithium (number 3 in the periodic table, it is even lighter than oxygen gas, by the way). According to this source, the lattice of nickel phosphorous tubes (Microlattice) is the lightest one. No information is given on its precise number though

According to source #2, graphene (practically carbon) is the strongest material known to mankind (of course, producing it is very expensive).

But, if you ask for the lightest material among the strongest materials, based on a set requirement, then there is insufficient data to answer that.

"Strongest, lightest" glass frame solid material will be some polymer, not titanium. For composites, carbon fiber likely the best, but I doubt it is made into glass frames. Beryllium will be the best metal, but I doubt it is made into glass frames. Magnesium would also be good but I doubt it is made into glass frames. High strength steel would be excellent, possibly the best; however because stress is so low and steel is so strong the section sizes would be fine wires, totally unsuited for glass frames. So, if you want a material you can buy today as glass frames ,likely titanium is it.