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New lightweight material is stronger than steel

news.mit.edu

61–70 of 162 posts

Re: New lightweight material is stronger than steel

#61
Just a heads up - strength is not a single metric. There is tensile (pulling), compression, and shear (sliding) strength. There's also Young's modulus (how much something stretches), fatigue limits (steel can work perpetually with deformations under a certain threshold).

There's also specific strength (strength per kg) vs strength per volume and strength per dollar.

Steel also comes in lots of different flavors, with very different (orders of magnitude) strengths.

Re: New lightweight material is stronger than steel

#62
post #2

> and can be easily manufactured in large quantities That seems promising. I have a couple of concerns - Can it be recycled? - How are new materials like this tested for toxicity?

The article mentions that it's melamine, which we currently find in Magic Erasers. It isn't recyclable or biodegradable, but seems to be non-toxic enough to be a regular fixture in the household cleaning arsenal.

It would be far better to use it as (long-lived) building material than as a sponge that quickly degrades and gets rinsed down the drain.

1. https://livegreen.recyclebank.com/column/because-you-asked/w...

Re: New lightweight material is stronger than steel

#63
post #49

Can't wait for 3D printed parts made out of this stuff. > the new material’s elastic modulus — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass. They also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel. That's g…

How does this compare with carbon fiber-epoxy laminate for elastic modulus? I don't have a ballpark figure for bulletproof glass. Looks like a typical carbon fiber laminate has similar, if slightly higher density (around 1.5 g/cm3).

[deleted]

Re: New lightweight material is stronger than steel

#64
post #39

Earlier quoted context omitted.

> a couple of concerns - Can it be recycled? Right. We have enough issues with plastic waste, without it having extra-ordinary strength.

It's possible the strength could reduce microplastics?

I imagine that even things that are nominally strong might be susceptible to things like UV. But IANAC.

Re: New lightweight material is stronger than steel

#66
Are there any samples big enough to be seen without a microscope? After a decade or more reading about nanotubes and graphene I'm a little jaded about "easily manufactured in large quantities". How long does it take to create a solid 1-foot cube? If you are comparing a new material to steel or concrete "large quantities" means multiple tons per hour. I'm going to need to see a sample bigger than a doorstop.

Re: New lightweight material is stronger than steel

#68
post #33
post #27

Earlier quoted context omitted.

It's hard to say without reading the paper itself, but in general one should be skeptical of claims that such-and-such material is stronger than steel. The properties that make steel interesting are not its elastic modulus or yield strength. This material is probably closer to graphite (which beats steel in elastic modulus and yeild strength) than something you would actually want to use in a structural application.…

I'm curious, in that case what properties do make steel interesting?

Some great answers here, but one other thing to add, is that it's also a material that's quite easy to recycle.

Re: New lightweight material is stronger than steel

#69

Just a heads up - strength is not a single metric. There is tensile (pulling), compression, and shear (sliding) strength. There's also Young's modulus (how much something stretches), fatigue limits (steel can work perpetually with deformations under a certain threshold). There's also specific strength (strength per kg) vs strength per volume and strength per dollar. Steel also comes in lots of different flavors, with…

Yeah I was annoyed about how the article didn’t say what strength they were measuring.

Not of course saying improvement in any of those metrics is bad, but the comparison being made needs to say what is being compared, and how it compares to the existing best in class.

Re: New lightweight material is stronger than steel

#70
post #2

> and can be easily manufactured in large quantities That seems promising. I have a couple of concerns - Can it be recycled? - How are new materials like this tested for toxicity?

It is quite certain that a 2-dimensional polymer cannot be recycled like metal, glass or a thermoplastic material, i.e. by remelting or by plastic deformation at high temperatures, because a 2-dimensional polymer cannot be deformed without breaking covalent bonds and it cannot flow in a liquid state.

So this new material might behave like the existing cured polymeric resins, e.g. epoxy resins, which form a 3-dimensional network of covalent bonds after curing, so they cannot be melted, and which when heated decompose before melting. Such materials can usually be recycled only by burning.

Nonetheless, there might be a more complex way to recycle the new materials, if the new materials would decompose in monomer molecules when heated or if there would exist some solvent able to break the bonds between monomer molecules, transforming the solid 2-dimensional polymer into a solution of the monomer molecules.

If such a method to depolymerize the 2-dimensional polymer would exist, the obtained monomer could be reused to synthesize again 2-dimensional polymers.

If the depolymerization is impossible then these materials would be used in the same way like the already existing and widely used insoluble and infusible polymeric resins.

More important for their success is what processing methods will be applicable for them. After the 2-dimensional sheets are formed, they cannot be processed by any of the popular methods, e.g. injection in a mold. The thermoset polymers behave similarly after curing, but they are produced in a state where they are only partially polymerized in 1-dimensional molecules, so they can be molded in the final shape and the complete polymerization happens later.

For now, it seems that these new 2-dimensional polymers can be made only as sheets, and then you must cut them in the shapes that you need, which will waste material in comparison with making the same shape from a thermoplastic or thermoset material.

Another problem not mentioned is that of the fracture toughness. They have made some tensile strength measurements and there is no doubt that the 2-dimensional polymers will have outstanding tensile strength. However the problem is which will be their fracture toughness for bending. Graphite has a similar structure and it also has excellent tensile strength in the direction parallel with the sheets, but it is also extremely fragile when you bend it.

An advantage of the 1-dimensional polymers is that they, like metals, can be deformed without breaking covalent bonds, which results in high fracture toughness for metals and 1-dimensional polymers, unlike the substances with 2-dimensional networks of covalent bonds (e.g. graphite) or 3-dimensional networks of covalent bonds (e.g. diamond), which are fragile.

So more research is needed to determine how useful these 2-dimensional polymers can really be.

In any case, just achieving their synthesis is already a very impressive result.

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