What is bullet proof glass and how does it work?

[htebazile]

I know that it is a mixture of layers of glass and a polycarbonate, and obviously the more layers the greater the bullet resistance. And that you need a lot of heat and pressure to bond the layers together, what else is there to know?

[ecoli]

It always shows up right when the hero is about the shoot the villian from the other side of a window.

[htebazile]

hehe , yeah it sure does!

You know you can get stuff which means the good guys can shoot at the bad guys through the glass, but the bullets fired by the bad guys at the good guys don't get through! sweet huh?

[5614]

Not much more to know.

The first layer of glass when hit by a bullet will possibly shatter and then the rest of the energy from the bullet is absorbed in the polycarbonate layer.

To stop higher energy bullets (ie. from a rifle instead of a handgun) a similar combination of layers of glass and polycarbonate is used, except more layers.

http://science.howstuffworks.com/question476.htm

You know you can get stuff which means the good guys can shoot at the bad guys through the glass, but the bullets fired by the bad guys at the good guys don't get through! sweet huh?Yep, neat stuff, explained how on that link above.

[RyanJ]

http://science.howstuffworks.com/question476.htm

Good link :)

http://en.wikipedia.org/wiki/Bulletproof_glass

I wonder if an aerogell could repace these...

Cheers,

Ryan Jones

[5614]

I wonder if an aerogell could repace these...
Maybe not an aerogel (they're so cool!) but they could be replaced with liquids.

Liquid body armour has been made/tested already, see here:
Slashdot: http://science.slashdot.org/article.pl?sid=04/04/23/2149209
Slashdot links to this for more detail: http://www.military.com/NewsContent/0,13319,usa3_042104.00.html
Similar article here: http://www.dcmilitary.com/army/pentagram/9_17/national_news/28729-1.html

[YT2095]

actualy there`s no such thing as "Bullet Proof" glass, it`s just a name used, it`s actualy Bullet Resistant, and effectively works by spreading the projectiles energy outwards, effectively "wasting" it.
trust me, repeated hits in the same place even with a low velocity round WILL actualy go Through the window, yes, even a .22 cal !

[RyanJ]

Liquid armour would begood becaue liquids are not compressable and would take the full force of the impact... very nice :D

Cheers,

Ryan Jones

[YT2095]

that`s great if you don`t mind windows that are about half a metre thick and weigh a tonne! LOL :)

[Cloud]

that`s great if you don`t mind windows that are about half a metre thick and weigh a tonne! LOL :)

I don't get it - I'm sure the bullet can go through that.:confused:
Do you mean to say just one big thick sheet of glass thats 50cm thick?

As for the liquid idea - yes. Thats the stuff.
I'm just wondering - what liquid would be used
(some kind of liquid-metal mixture)

[YT2095]

half a metre thick and heavy was for the liquid idea (like a fish tank), even then it would only be good against a single shot, it`s really impractical.

[Cap'n Refsmmat]

Indeed. According to New Scientist, you'd need about a meter of water to stop a bullet.

As for bulletproof glass, the polycarbonate layer keeps the glass from shattering. It simply holds the glass shards together, so that they don't go flying everywhere.

[5614]

With a normal window if you make one crack then the crack can spread and cause the whole window to break... but if you have multiple layers of glass (and polycarbonate) then the one crack (caused by the bullet) will spread across that sheet of glass, but not the whole window (multiple layers) so the effect will not be as destructive on the window as a whole.

[tomheppy]

im doing a project on bulletpproof glass for my physics.I have found out the energy of the bullet but i need to somehow apply this to the energy needing to break the bulletproof glass.I have found out fracture energy ,is this the amount of energy to break the glass or what?Any suggestions would be most appreicated.

Tom H

[5614]

http://en.wikipedia.org/wiki/Fracture_mechanics

And see this section: http://en.wikipedia.org/wiki/Fracture_mechanics#Griffith.27s_Crack_Theory:_Stra in_Energy_Release_Rate
for a part about fracture energy.

[michaeldennis83]

Bullet proof glass (http://www.bulletproofspecs.com) can also be made of acrylic or or glass clad polycarbonate and goes from levels 1 - 8.

[brassmonkey]

I know that it is a mixture of layers of glass and a polycarbonate, and obviously the more layers the greater the bullet resistance. And that you need a lot of heat and pressure to bond the layers together, what else is there to know?

Currently there is no such thing as "bullet proof glass."

[Lance]

I saw a humvee window hit by a rifle round. It didn't really shatter but it created these sort of permanent waves in the glass around the impact site.

[DrP]

I saw a humvee window hit by a rifle round. It didn't really shatter but it created these sort of permanent waves in the glass around the impact site.


That would be the quantum freeze field generators coming into effect arround the window frames (ALL hunvee's have them nowadays ;)) - it creats a quantum time freeze arround the impact site that slows the bullet impact right down. Thus it freezes the ripples from the impact into the glass rather than allowing the shatter. Genious really.

[Lance]

That would be the quantum freeze field generators coming into effect arround the window frames (ALL hunvee's have them nowadays ;)) - it creats a quantum time freeze arround the impact site that slows the bullet impact right down. Thus it freezes the ripples from the impact into the glass rather than allowing the shatter. Genious really.

Lol. I'm sure. The glass is also around 4" thick. There's a running joke that when an up-armored Humvee is hit by an IED and completely destroyed the windows are the only thing left intact.