Paper-Thin Graphene Material Ten Times Stronger Than steel

[dragon]

Kind of niffty when you think of the applications

Researchers at the University of Technology Sydney have created a new material that is lighter, less dense, harder, and stronger than steel. But this material isn’t one of those breakthroughs that only sounds good on paper. It is paper, and it could be a game-changer for materials science if it can live up to researchers’ hopes.

This graphene paper is constructed of graphite reformed by chemical processes into monolayer hexagonal carbon lattices stacked as thin as a sheet of paper, and it is remarkably strong. To quote a press release from UTS:


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Compared to steel, the prepared GP is six times lighter, five to six times lower density, two times harder with 10 times higher tensile strength and 13 times higher bending rigidity.
That’s no incremental improvement on the qualities of steel, but a huge leap forward in terms of overall material strength (plus, like paper, it is flexible). And because it is graphene, it is also imbued with some interesting electrical, thermal, and mechanical properties.

But perhaps best of all, graphene paper not outrageously difficult or expensive to manufacture, and as such it could have huge implications for the aviation and automotive industries, where manufacturers have already been turning to composites and carbon fiber materials to cut weight and thus increase fuel economies

link

[Broomstick]

How brittle is it?

There are several ways to evaluate strength - compressive, tensile, shear, etc. Different qualities are required for different applications.

[dragon]

How brittle is it?

There are several ways to evaluate strength - compressive, tensile, shear, etc. Different qualities are required for different applications.

six times lighter, five to six times lower density, two times harder with 10 times higher tensile strength and 13 times higher bending rigidity

Well 10 times higher tensile strength easy enough to figure out
The 13 times bending rigidity, also know as Flexural rigidity, depends on Young's Modulus, thickness and Poisson's Ratio.
the weight and denisity also easy enough to know.

edit ok the actual paper for Advanced mechanical properties of graphene paper can be found here
link

but they want you to pay of course. But the outline is listed and it looks like they only tested III.RESULTS AND DISCUSSION
A.Physical and structural characterization
B.Tensile test
C.Indentation test
D.Bending test

[dragon]

ok found a site where you can read and download the paper
link

[Broomstick]

So... what about applications where ability to flex without breaking is important, rather than pure rigidity? (and yes, I'm probably not expressing myself well on a technical level because I'm not a metallurgist) Springs, for example, where ability to repeatedly flex is important? How well does it work in those applications? If it doesn't perform as well as, say, spring steel in that application that would be important to know, wouldn't it? It makes a difference for landing gear in airplanes, as the example that comes first to my mind.

[dragon]

not a clue but I'm not a material engineer so I have not a clue.

[Imperial528]

I've heard a lot about graphene, mostly due to having a friend who's obsessed with it, and although I can't source this information, this is what I know about the material:

A single sheet is made up of interlocking carbon molecules and is 1 molecule thick.

To pierce a 100 micrometer thick sheet layer with a sharpened pencil (or rather, a pencil-shaped object, since the pencil would break) you would need to apply a force of 20Kn (kilonewtons).

The electrical properties of graphene change based on how you cut it, e.g., a long, thin strip of graphene conducts differently than a wide sheet, and the differences based on shape can be used to make circuits out of the material, allowing for things like paper-thin Ipads. It's most useful as an electrical component, rather than a structural one, although you can probably make solar sails out of it.

I'm afraid I can't recall anything more specific than that at the moment, and I can't remember the source articles my friend got this information from (he told it to me), but I can ask him, since he's writing a research paper about graphene (high school research paper, so it's basically just written from sources).

[Coriolis]

So... what about applications where ability to flex without breaking is important, rather than pure rigidity? (and yes, I'm probably not expressing myself well on a technical level because I'm not a metallurgist) Springs, for example, where ability to repeatedly flex is important? How well does it work in those applications? If it doesn't perform as well as, say, spring steel in that application that would be important to know, wouldn't it? It makes a difference for landing gear in airplanes, as the example that comes first to my mind.

With something as stiff as graphene, you'd turn it into a composite for structural applications. I can't imagine that it would fare well while being flexed. First, you suspend it in something flexible, like an epoxy matrix (similar to rebar in concrete). That way, you get the flexibility of the epoxy while you retain the graphene's strength. Obviously, you'll end up with a material that's neither as flexible as epoxy nor as strong as graphene, but you get the best of both worlds.

If you want to make, for example, a spring, you can take a sheet of your composite and cut it into strips. You can then take those strips and arrange them in a helix as so:

link here because image is massive

[Broomstick]

That still doesn't mean it will perform as well as metals for spring applications.

Hey, I love new materials as much as anyone, but I'm always skeptical about the claims made for them. Sure, composites are lighter and stronger (in some ways) than steel but I've yet to see an airplane that uses composites for landing gear rather metal due to the need for repeated flexing. Even on the very small airplanes I fly steel is the material of choice despite the weight penalty because so far nothing else performs better. Heck, I've flown an airplane were the entire airframe, including the main spar, was composites epoxied together except the landing gear, which was very mundane spring steel.

I'm also curious about the way the material fails. Things like wood, cloth, and metal fail in a manner where, if you bother to look, you can detect war and imminent problems. It's been a problem that with composites they can fail without (apparently) any warning. This can limit where they are used. You can repair wood, cloth, and metal constructions, but some composites are extremely difficult or effectively impossible to repair.

Then there is the matter of when the shit hits the fan, or the vehicle hits a wall (or tree or mountainside, or...) I've seen the aftermath of both airplane and car accidents. Wood and metal, because they bend and flex before breaking, tend to "soak up" some of the impact, which can save the life of the occupants. Current composites shatter, in some cases very like glass, and provide little or no "crumple zone" type protection. As a result of this, I've seen some small aircraft designed with a steel roll cage around the cockpit because otherwise the pilot/passengers have no protection in the event of an accident (which needn't be a crash from altitude - people have been known to hit the side of buildings while moving around on the ground, or collide with other vehicles on the ground). Modern cars are likewise designed to protect the occupants, with "crumple zones" sacrificed to reduce the forces on the "cockpit" and reinforcement (typically steel again) around the people inside.

Which is why I ask about this new graphene material. It may, in fact, be very strong in many ways but if an impact can shatter it, then it will affect where it is used in building things. Glass is also very strong in many ways, but due to the way it fails we limit where we use it. It would fantastic if the failure mode of graphene was less problematic than that of, say, carbon composite or fiberglass, but so far I haven't heard the answer to that question.

[dragon]

True it needs further testing but initial results look promosing at least for certain applications.

[Broomstick]

Unquestionably, there will be uses found for it. I just don't want to see the usual "Wonder Material Does Everything" hype, because frankly I find it irksome and tiresome.

[Coriolis]

That still doesn't mean it will perform as well as metals for spring applications.

Oh, I never meant to imply that graphene's going to compete with metals. There is no way graphene (or composites for that matter) can fully replace metals in some functions (such as springs). I'm just lifting ideas off the top of my head. Most likely, graphene's going to be used in applications that require an incredibly thin, conductive material (such as organic flexible LEDs and the like). Yes, graphene has nice mechanical properties, but much of current research is being geared towards thin-film technologies.

[Jaepheth]

One thing about steel is that it fails 'nicely'.

A lot of these super materials are fine and dandy when they're working, but then fail suddenly and catastrophically.
Put too much force on steel (sheer, compression, or tension) and it'll bend or deform; thus giving you some warning before it fails completely. It's an important feature for real-world/everyday applications.

[General Trelane (Retired)]

What you're trying to describe is "ductility". A ductile material will experience significant plastic deformation before rupture whereas a brittle material will not, so yes, a ductile failure will give plenty of warning before rupture occurs.

But there is "fatigue" to be considered. Materials under cyclic repeated stresses (like aircraft landing gear) can fail even though the stresses never exceeded their ultimate or even their yield strengths; such a fatigue failure is also sudden and catastrophic and even looks very much like a brittle failure. And if the material never yielded (plastically deformed), there is no warning either.

[Broomstick]

Impending metal fatigue actually can be detected, even if not with the naked eye. Testing for it in aircraft is routine.

[Starglider]

But there is "fatigue" to be considered. Materials under cyclic repeated stresses (like aircraft landing gear) can fail even though the stresses never exceeded their ultimate or even their yield strengths; such a fatigue failure is also sudden and catastrophic and even looks very much like a brittle failure.

Isn't that another reason to use steel even though it's heavier than aluminium? Steel has a lower fatigue limit below which negligible crack growth occurs, unlike aluminium.

[Tolya]

Excuse me, but isn't graphene known since 2004? What is the big fuss in the news? Did Aussies invent something already known for 7 years? Or is it something new?

I though the big news on graphene right now is that some Polish scientists have developed a way to mass produce it and are seeking to obtain a patent for it.

Linky