
Porous, 3D forms of graphene can be 10 times as strong as steel but much lighter - mattiemass
http://news.mit.edu/2017/3-d-graphene-strongest-lightest-materials-0106
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knicholes
So this is just saying that the shape of a material determines its strength?
From what I gathered from the video, they didn't actually use graphene in
these objects.

I was reading a introductory book on metallurgy over the holidays and realized
that I had no idea what "stretching" was. I still hardly have any idea, but
from what I was able to gather from the book, in steel at least, when
stretched, there are these molecular "fault-lines" that can shift and still
stay stable without actually breaking. Apparently, steel can be put under
stress to fall to this final state to avoid further shifting during use in
machines and whatnot.

Maybe I'm completely missing the point and the plastic is somehow stronger
than steel, but the quote

>"You can replace the material itself with anything," MIT's head of Civil and
Environmental Engineering said. "The geometry is the dominant factor."

makes me think that this is the case?

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Chris2048
But the article says:

> In its two-dimensional form, graphene is thought to be the strongest of all
> known materials

Doesn't this imply it is stronger than steel in 2 dimensions?

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knicholes
I think this implies that GRAPHENE is stronger than steel, but this 3d printed
thermoplastic is definitely not stronger than steel given the same shape.

~~~
Chris2048
What I mean is "in 2 dimensions" may be relevant, since the shape seems to be
a 2D sheet folded into 3D space.

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rsfern
The original journal article is open access [0], and I think it's pretty well-
written and accessible.

This is a really great example of theory-driven materials design.

[0]:
[http://advances.sciencemag.org/content/3/1/e1601536.full](http://advances.sciencemag.org/content/3/1/e1601536.full)

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tlb
(ten times stronger than _mild_ steel, at 2.7 GPa tensile yield.) Nobody is
deciding between mild steel and graphene. Comparing to PAN carbon fiber (which
can achieve 7.0 GPa yield with careful manufacture) would be more useful.

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hardwaresofton
_> MIT says that this is because the thinner walls allow the structure to
deform gradually while the thicker one stores the deformation energy, which
releases all at once_

I'm not sure that's the failure mode I want load-bearing things to have...

~~~
dTal
It's a perfectly fine failure mode in applications where failure of any type
is automatically catastrophic anyway - for instance, a submarine's pressure
hull.

~~~
hardwaresofton
I don't know much about submarines, but I assume that you mean once the
pressure hull is penetrated, the resulting pressure difference will quickly
make short work of the hull.

My point was that, if I could _choose_ the failure mode, I wouldn't pick fail-
all-at-once, if I could avoid it (for most things that bear load). If I could
design/create a pressure hull that somehow didn't fail all at once, I think
everyone would be happy?

~~~
Retric
If it was torpedoed a moderate diffence in hole size is not going to matter. A
larger issue would be how flammable this stuff is.

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zwieback
Is it just me or are prestigious institutions such as MIT frittering away
their respectability with press briefs such as this?

~~~
forgotpwagain
You should compare the actual university press release [0] to the article
written by an external organization above.

[0] [http://news.mit.edu/2017/3-d-graphene-strongest-lightest-
mat...](http://news.mit.edu/2017/3-d-graphene-strongest-lightest-
materials-0106)

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imaginenore
Yes, yes, graphene is awesome, we know. Can you make cheap sheets of it?

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Pica_soO
Imagine the burj al arab ten times higher.

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varenc
I don't know if the writer really understood what's going on there. Those
models are just plastic. Understanding how to make strong shapes is useful for
eventually building real structures with graphene in the future, but nothing
about that research used graphene.

I think they're saying that if that plastic model was graphene then it would
be 5% as dense and 10x as strong as steel...but no such thing was actually
created. The title here is pretty click baity.

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Breefield
Title is very click-bait. The MIT News article it links to is much more
informative: [http://news.mit.edu/2017/3-d-graphene-strongest-lightest-
mat...](http://news.mit.edu/2017/3-d-graphene-strongest-lightest-
materials-0106)

~~~
gene-h
So they show that a graphene gyroid structure could be quite strong
compressively. Now, the challenge is actually make such a structure. Making a
template for graphene to grow on like this is bound to be quite challenging,
minimizing the amount of defects in such structure even more so!

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ChuckMcM
Yes that was what I got out of it, and at the same time I am totally updating
the Slicer infill pattern on my 3D printer to make stronger structures :-)

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gene-h
While this is worth trying for the sheer coolness of it, I'm a bit skeptical
about how it will perform. For FDM things are much weaker in the Z-direction
than they are in the x-y plane.

~~~
ChuckMcM
Exactly correct, the Z direction is a challenge in FDM printing. I built some
"strength tester" forms (basically thinks I could crush or pull apart or bend)
to understand what sort of structural stability could be expected out of a
given filament and the process in general.

