How does paper survive?

**p.dath** · 6th January 2014, 12:01

I was watching a TV program yesterday called Mayday about airplane crashes. One of the crashes was caused by a murder/suicide by a passenger, and they put the jet into a direct nose dive at full power. The plane hit the ground with a force of 5,000 g (yes, 5,000 times the force of gravity). The plane had exceeded mach 1 at the point of impact.

The impact was so hard that the plane was shredded. The murder weapon, a 44 calibre pistol had it's short barrel broken. They couldn't identify anything that look like a human body or a bit of a body. Everything was pulverized beyond recognition.

Everything - except a lot of paper. In fact, they even found the suicide note. The paper wasn't even torn or marked. The crash site was surrounded by what looked like shrapnel from the plane being ripped apart - and lots of sheets of paper.

I sat there wondering how it is that with the engineering knowledge that society posses that all the different materials failed (under an huge impact load to be fair) but something as flimsy as paper survived undamaged. I'd tried doing some Googling about the forces that paper can withstand, but I mostly came up with unrelated searches (everything is a research "paper").

I did some thinking, and I'm guessing that paper has a very low shear force (which is why you can cut it with sissers and tear it) but can withstand a lot of compression force (try squashing a flat sheet of A4 paper between your hands).

It kind of makes me wonder if paper is really that resilient to huge compression forces that perhaps there is something we have overlooked about it that could be incorporated into other materials to make them withstand considerably higher compression forces.

So, anyone keen to swap their helmet for a paper hat?

**bogan** · 6th January 2014, 12:11

I know right, and have you seen the metal paper they make? It's called shim steel, even stronger than normal paper. You know what we need, is to make planes out of this shim steel stuff, maybe we could form it into beams and things with good structural rigidity (which of course would no longer be fit for shims, so would just be called steel), and perhaps rivet more of the thin stuff to it for aerodynamics

**BuzzardNZ** · 6th January 2014, 12:23

Originally Posted by p.dath

So, anyone keen to swap their helmet for a paper hat?

A wooden one might work. How about you try hollowing out a coconut shell and wear that?

**vifferman** · 6th January 2014, 12:44

Originally Posted by p.dath

I sat there wondering how it is that with the engineering knowledge that society posses that all the different materials failed (under an huge impact load to be fair) but something as flimsy as paper survived undamaged. I'd tried doing some Googling about the forces that paper can withstand, but I mostly came up with unrelated searches (everything is a research "paper").

I did some thinking, and I'm guessing that paper has a very low shear force (which is why you can cut it with sissers and tear it) but can withstand a lot of compression force (try squashing a flat sheet of A4 paper between your hands).

Your 'logic' is not very logical, and is in fact flawed (you've thought in the wrong direction). Firstly, if there were individual sheets of paper (unlikely to have been many, apart from passenger lists, documents, etc., they would have survived anyway (short of being burnt) because they have very low mass (and therefore inertia) and a fairly high surface area, yet are very flexible. They were also probably largely unconfined (free to move around), and the shock waves from the impact would have blown them in all directions. Much of the paper present would have probably been torn from books and magazines on board the plane - so there's your shearing).
In any case - other similar low mass, low strength objects would have survived too if present - like unconstrained/unconfined feathers, styrofoam, hair, sheets of cotton, vinyl and other fabric.
The paper isn't that strong, and if confined at the edges (like the sheets of aluminium the aircraft was clad with), would have been subject to tearing, puncturing, etc. (pages ripped from books and magazines).
If you took the same paper, and glued it to other sheets (essentially what 'customwood' is), and made bits of the plane out of it, it would have been stronger, but suffered much the same fate as other materials.

**FlangMasterJ** · 6th January 2014, 14:32

Umm because it's paper. Throw a sheet of paper at the ground as hard as you can, what happens? It sails off in random directions then floats to the ground

**Virago** · 6th January 2014, 14:47

Vifferman got it in one.

A sheet of paper has low mass, therefore low inertia.

It's the same principle that allows an insect to simply walk away from a fall that would kill a human.

**Banditbandit** · 6th January 2014, 15:04

Try Newtonian physics ... F=M x A

M= mass (of the paper) F= Force A= Acceleration ...

So paper is very very light - bugger all mass ... the force = bugger all x the acceleration (or in this case deceleration) ...

Not hard to see how paper survives such an impact

**Big Dave** · 6th January 2014, 16:08

Tax invoices and GST receipts.
They possess the same anti-matter as odd socks.

Ubiquitous until actually required.

**Kickaha** · 6th January 2014, 16:37

Originally Posted by Banditbandit

Try Newtonian physics ... F=M x A

M= mass (of the paper) F= Force A= Acceleration ...

So paper is very very light - bugger all mass ... the force = bugger all x the acceleration (or in this case deceleration) ...

Not hard to see how paper survives such an impact

Yeah, try that with your fucking Kindle

**jasonu** · 6th January 2014, 17:06

Originally Posted by bogan

I know right, and have you seen the metal paper they make? It's called shim steel, even stronger than normal paper. You know what we need, is to make planes out of this shim steel stuff, maybe we could form it into beams and things with good structural rigidity (which of course would no longer be fit for shims, so would just be called steel), and perhaps rivet more of the thin stuff to it for aerodynamics

No they should make planes, trains and space shuttles out of 'black box' material. That part always seems to survive a crash.