It is easy to find on Google that the tensile strength of graphene is 130,000 MPa. But what is it's compressive strength?
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asked Sep 5, 2021 at 16:22
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$\begingroup$ It does not seem defined anywhere, although it is used to increase the compressive strength of the concrete. I guess it is mainly caused by its lack of toughness in fracture. However, this source claims the compressive strength of ((modified?) graphene is 361 MPa. onlinelibrary.wiley.com/doi/abs/10.1002/adma.201201519 $\endgroup$– r13Commented Sep 5, 2021 at 18:16
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$\begingroup$ I'm trying to make graphine as a material in onshape, so I, too, want to know as much about it as possible. $\endgroup$– Mr. UnknownCommented Jan 2 at 23:26
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2 Answers
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Graphene is an allotrope of carbon (same as diamond, graphite and fullerenes ), (allotrope to my mind is a fancy way of saying that the molecules can be arranged in different configurations). Graphene in particular arranges the molecules of carbon in a two dimensional hexagonal lattice.
Figure: hehagonal lattice of carbon (source Graphene-info)
In essence it looks like very thin surface, very much like a thin sheet of paper, with a dimension of 1-2 [nm] (or 1-2 millionth of a mm). Therefore, it has a similar behavior to a piece of paper. I.e.
- the tensile force required for failure for a sheet of paper is well defined.
- the compressive force required to fail (through crumbling) varies depending on the dimensions and the support. I.e. buckling becomes the dominant method.
I.e. a longer sheet would fail under its own weight.
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For comparison purposes, Diamond, has the following lattice. The lattice is face-centered cubic Bravais lattice
Figure: Diamond lattice(source uiuc.edu)
The three dimensional nature of this structure allows the creation of 3d objects (with varying thicknesses).
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$\begingroup$ What abouit the analogy of a rolled up sheet of paper? Does that allow to overcome buckling? $\endgroup$ Commented Sep 6, 2021 at 8:05
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$\begingroup$ I think you are talking about graphene nanotubes. Typically the graphene nanotubes are between 30 and 100 nm. However, similar problems occur in the definition of the compressive load. I.e. if you take a straw (which is a sheet of plastic rolled), the length of the straw has a significant effect on the collapse. Additionally, if you make the straw walls thin you get 2d buckling. $\endgroup$– NMechCommented Sep 6, 2021 at 8:09
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A fiber as thin as a few atoms doesn't have a comprehensive strength by itself. it will buckle or break and crash into tiny microscopic particles that are dangerous if breathed by the workers.
it depends on how it is embeded in resin and what is the compressive strength of the resin.
also because of the density of the composite material which is usually low the compresive strength i lower significantly.
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$\begingroup$ It's possible we simply don't know it because we don't have enough of it to measure with. $\endgroup$– DKNguyenCommented Sep 5, 2021 at 19:35
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$\begingroup$ @DKNguyen, we do have enough of it. We simply don't want to fuse together back millions of fibers, its just defying the purpose. the tinsile strength is due to atomic mesh of carbon. we need to keep it. $\endgroup$– kamranCommented Sep 5, 2021 at 19:47