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Paper Stronger Than Cast Iron
TaeKwonDood writes "All paper is made of cellulose, which at the nanoscale level is quite strong, but paper processing makes large, fragile fibers that break easily. Researchers in Sweden have have come up with a manufacturing process that keeps the fibers small, resulting in 'nanopaper' with over 1.6 times the tensile strength of cast iron (214 megapascals vs. 130 mPa). And since cellulose is the most abundant organic compound on the planet, it's cheap to use compared to other exotic, expensive-to-produce options — such as carbon nanotubes."
> 214 megapascals vs. 130 mPa
214 megapascal (singular, it's a unit) is about 1.6*10^9 more than 130 millipascal. Use your units properly.
This is hardly surprising given that the source for most paper is wood, and wood has the highest tensile strength of any building material known to man based either on weight or cross sectional area.
Not a lot of our building techniques rely primarily on tensile strength, most rely on spanning gaps with weight bearing members. But if you have to hang something heavy, Wood is your friend.
Tensile strength does come into play on collapsing structures, as weight bearing members are removed, and buildings end up hanging from their walls or rafters. Firefighters really dislike entering steel framed buildings, when fighting active fires because steel softens and collapses without warning, where as wood groans and snaps and gives ample warning that it is about to collapse.
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Oops, just RTFA'd. They didn't show that paper was as strong as paper. They made paper twice as strong as old "high strength" paper. Which still has very, very little tensile strength. Comparing to cast iron really doesn't help their case.
With the paper there is the advantage that small particle sizes dramaticly increase strength.
Tm
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There's actually an anime with a paper-powered superhero.
http://www.youtube.com/watch?v=L5Lxn5y2Xe8
wood has the highest tensile strength of any building material known to man based either on weight or cross sectional area.
No, steel does. That's why I-beams are steel, not wood. It's also why the cables in suspension bridges are steel, not wood poles.
Not a lot of our building techniques rely primarily on tensile strength, most rely on spanning gaps with weight bearing members.
And what determines how well you can span a gap? A combination of compressive and tensile strength. You need to revise your beam bending...
Tensile strength does come into play on collapsing structures, as weight bearing members are removed, and buildings end up hanging from their walls or rafters.
So what does some in to play? Probably a mixture of tensile and compressive strength, depending on what is failing and why.
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Awesome anime - did they ever do more?
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But... cast iron has the tensile strength on the order of concrete.
I think you might be two orders of magnitude off. Cast iron shows up as having around 130 to 200MPa (depending on your figures), concrete shows up at 3MPa. Having used it, cast iron can be pretty cheesy stuff. But I imagine that strength-to-weight is pretty good.
it's "*badum-psht*"
Icebike wrote
>...wood has the highest tensile strength of any building material known to man based either on weight or cross sectional area.
I Think your estimate of wood is much too high. Wikipedia's article of tensile strength http://en.wikipedia.org/wiki/Tensile_strength lists pine wood at 40 MPa I know there are some woods that are significantly stronger but still.
For comparison some other tensile strengths listed in MPa are:
Cast Iron 200
structural steel 400
steel piano wire 2500
Concrete 3
HDPE plastic 37
Aluminum Aloy 455
Glass 4710
Carbon fiber 5650
Carbon nanotubes 63000
If nothing else, it will revolutionize the packaging industry. Strong cardboard boxes are a holy grail of packaging.
Other uses? Paper airplanes, coat it with plastic and make a really cheap fishing boat, tape that won't break, temporary floor, single-use knife, non-toxic circuit board for cheap toys... This is a breakthrough in the highest meaning of the word.
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Even when adjusting for weight, the tensile strength of wood isn't so great compared to S-glass or carbon fiber. And when adjusting for cross sectional area, the tensile strength of wood fares even worse because it has a lot of air in its pores.
The same weight of wood would be stronger.
But not the same cross-sectional size.
If it's loaded in pure tension, you're right, wood is stronger per unit weight. However one thing that you have be careful of with wood beams is that wood has a very low shear strength which makes beams fail at much lower loads than you would expect from the tensile strength alone. It also isn't very strong in tension across the grain which limits your design freedom.
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This comparison is highly suspicuous. You do not use cast iron for anything that needs tensile strenght, as it breaks too easily. Wrought iron is a whole different matter and is what is used in construction of cars, ships, girders, and the like. Cast iron in the shape of a pice of paper could easily broken by hand without tools.
It seems aluminum alloy has about twice the tensile strength of cast iron. Ever tried to rip tinfoil? Not that difficult.
Side note: mPA is milipascals, not megapascals.
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...Jules Verne wrote about a heavier-than-air airship that was made from paper, treated with glue and pressed into shape. the resulting material was "as strong as the best steels, and much lighter", to quote the author.
the novel is called Robur-le-Conquerant (Robur the Conqueror) (1886)
You'd be surprised...
In the UK at least half of all domestic construction uses timber frame for the load-bearing structure with simple block and render for the outer skin which provides none of the structural support. Come up to Scotland and practically every building less than 5 storeys high is made using a timber frame.
The trick in making a building fireproof isn't in making the structure fireproof, but in stopping the fire from getting to the structure in the first place. That's the why every wall and ceiling is made from plasterboard of some kind, because they provide the 30 and 60 mins of fire resistance, not the studs or the joists.
I'd provide figures to back my assertions, but my books and magazines are in another office.
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