Paper Stronger Than Cast Iron 327
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."
Milli-pascal? (Score:5, Informative)
214 megapascal (singular, it's a unit) is about 1.6*10^9 more than 130 millipascal. Use your units properly.
Re:First! (Score:3, Informative)
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.
Re:Don't they realize... (Score:5, Informative)
One point about grey cast iron (Score:5, Informative)
With the paper there is the advantage that small particle sizes dramaticly increase strength.
Re:Milli-pascal? (Score:5, Informative)
Also most steels are above 400 MPa (some as high as 1800) so this isn't that strong, in fact Aluminum alloys can reach into the 400 MPa range.
Cast Iron (in its 2 major forms grey & white cast) is very brittle and therefore does not have good tensile strength. However compressive strength and its good vibration tolerance is why a lot of large machining equipment uses a cast iron base.
cast iron? (Score:5, Informative)
Tm
Re:Iron Man's nemesis... PAPER MAN (Score:2, Informative)
http://www.youtube.com/watch?v=L5Lxn5y2Xe8
Re:First! (Score:5, Informative)
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.
Re:Iron Man's nemesis... PAPER MAN (Score:5, Informative)
Awesome anime - did they ever do more?
Re:Don't they realize... (Score:5, Informative)
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.
next time (Score:2, Informative)
Re:First! (Score:5, Informative)
>...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
Re:Great, but is it fireproof? (Score:4, Informative)
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.
What is Tensile Strength (Score:5, Informative)
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.
Re:First! (Score:5, Informative)
But not the same cross-sectional size.
Re:Milli-pascal? (Score:3, Informative)
Re:cast iron? (Score:5, Informative)
Think of a thin stationary engine housing with fins to dissipate heat -- you usually don't care if the fins are within 0.25" of where they're supposed to be; as long as air can pass over them they can do their job. As far as the important surfaces, such as the ones that hold the bearings or that mate with another housing, sure, you'll have to machine those. But if you had to machine all those fins from a solid steel block, or cut a bunch and weld them all on, you'd easily spend three times the money on labor and tooling and have a part that doesn't last as long as a casting.
There are many different alloys of cast iron, and they each have their own set of properties. All are much harder than ordinary steels, and usually have excellent wear resistance. Some alloys allow for more intricate castings. Some are easier to machine. And some, such as white iron, are extremely brittle and almost worthless in tensile strength, but can be treated to crazy levels of hardness. It all depends on your application, and in which properties you require. Steel can't simply be "dropped-in" as a replacement material. Hell, sometimes you can't even substitute ductile cast iron for malleable cast iron.
And I wouldn't count on being able to substitute paper for cast iron, either!
Re:First! (Score:5, Informative)
Cast iron is not very strong... (Score:3, Informative)
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.
122 years earlier... (Score:2, Informative)
the novel is called Robur-le-Conquerant (Robur the Conqueror) (1886)
Re:Great, but is it fireproof? (Score:3, Informative)
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.
Re:Milli-pascal? (Score:3, Informative)
Re:Cast iron is not very strong... (Score:3, Informative)
The aluminum found in aluminum foil would never be used in aircraft construction or anything else requiring strength. While I love materials science, TFA or the researchers (whoever chose this comparison w/ cast iron) are way off base here. Anyone who has worked with thin materials including cast iron knows that tensile and shear strengths do not scale and are not compatible among different metals (example: you can't replace thick aluminum with thinner steel because although the tensile strength may be higher, the shear strength will be lower. This is important in aircraft repair, as some members endure one or both stresses).
Also, tearing a sheet of foil constitutes shear stress, not tensile. A sheet of aluminum foil perfectly supported somehow on both ends so that the force was equal along its length would be stronger than you might imagine. Think of it this way:
12 inch sheet X
That gives you a wire with diameter of
-b
Re:First! (Score:3, Informative)