

Even graphene has weak spots - rosser
http://news.rice.edu/2013/03/28/even-graphene-has-weak-spots/

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hkmurakami
_> The kryptonite to this Superman of materials is in the form of a seven-atom
ring that inevitably occurs at the junctions of grain boundaries in graphene,
where the regular array of hexagonal units is interrupted. At these points,
under tension, polycrystalline graphene has about half the strength of
pristine samples of the material._

 _> The lines in polycrystalline sheets are called grain boundaries, and the
atoms at these boundaries are occasionally forced to change the way they bond
by the unbreakable rules of topology. Most common of the “defects” in graphene
formation studied by Yakobson’s group are adjacent five- and seven-atom rings
that are a little weaker than the hexagons around them._

Honestly, the findings seem pretty standard and are in line with material
properties of more traditional polycrystalline or even amorphous materials.
With all sorts of material failure modes, it's these "pressure points" that
are the first point of failure.

(Note: I've done Carbon Nanotube research in the past and hence I'm familiar
with this kind of material, but I'm by no means a materials science or
mechanical engineering expert)

I've done these kinds of CVD depositions (used to make these graphene sheets
discussed in the OP) myself, and imperfections (which are visible under TEM
microscopy) are the norm.

