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I bought Bullet Proof Glass... and I am testing it

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Hon1nbo

Tue Jul 28 2009, 10:52PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

ok, so I just bought a 3x5 feet panel of at least level three bullet resistant glass for $100 (it is apparently rated for a shotgun as well, but it was sold as level three to be safe on specs) - the panel is one inch think

well: I want to test it out, as I will have some small square shaped remainder after cutting it to my needs, and I am wondering the best procedure to test it out, as I assume simply firing randomly won't give me accurate results as to what it can take

I plan to test a 9 mm, a .44, a shotgun (non-slug shell), and a .306 rifle from a longer distance than the handguns

should I be following a certain order when testing this? I don't want to have to cut a separate piece for eveyy different round, I just want to be able to test using one 12x12 inch cut at an outdoor range

Proud Mary

Tue Jul 28 2009, 11:49PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

It may well be that after the first shot that strain patterns form in the glass, so that what is true for shot A, will not be true for shots B & C until the glass fails altogether.

You may well be able to visualize these strain patterns with a polarizer.

There are very many variables in your proposed test, including such things as the hardness of the projectile, it's Young's modulus, its momentum, its angle of incidence - one could go on and on.

Leave it to a military ballistics laboratory with a big budget.

Sulaiman

Wed Jul 29 2009, 05:14AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Due to stupid vandals, UK trains have front windows that can protect from a brick at 100 mph
The 'bullet-proof-ness' comes from polycarbonate.
There is an exterior glass layer as a non-scratch surface. (windscreen wipers etc.)
There is no glass layer on the inner surface to preveny glass shrapnel.
So assming yours is similar, the first shot will shatter the glass layer.

P.S. The method of fixing the bullet proof glass to the metal frame affects durability.

Proud Mary

Wed Jul 29 2009, 07:27AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Bullet resistant glass is either of the type Sualiman describes, with a polycarbone inner layer, or is fabricated from thin glass sheet laminated with adhesive.

In the laminated type, delamination to varying degrees, combined with shatterring of one or more laminae means, as I first suggested, that the conditions of impact and penetration for shots successive to the first will keep degrading until total total failure occurs.

It would be interesting to determine the refractive index of the glass, and see how this changes proximate to damage areas.

Steve Conner

Wed Jul 29 2009, 09:25AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

How do you cut bulletproof glass? If it can stop a bullet, surely it can stop most tools, too.

And like other posters mentioned, the first shot will weaken the glass even if it doesn't break it, so the following shots won't be fair tests. The most scientific thing to do is probably to start with the most powerful gun you have, and if it can stand a shot from that, assume it could withstand all the others too, but then try them anyway for fun.

Or just shoot randomly at it with an assortment of weapons and post the footage on Youtube.

Proud Mary

Wed Jul 29 2009, 11:14AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Steve McConner wrote ...

How do you cut bulletproof glass? If it can stop a bullet, surely it can stop most tools, too.

Hardness, as in Mohs and Rockwell, is what makes the cutting hard work for a tungsten or diamond glass saw.

In bullet resistant glass, the glass must flex to absorb the shock load before it be punctured through and through, so we must distinguish between abrasion resistance, as in sawing, and point shock load resistance. where Young's Modulus and the other elastic moduli are at the fore.

Consider the case of helmets and body armour made of "Kevlar," which can be cut with a blade, but absorbs and dissipates shock loads before they can puncture the material through and through.

Hon1nbo

Wed Jul 29 2009, 06:03PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

ok, first the glass is cut using a circular saw, carbide blade with plenty of teeth, and with proper lubricant

also there is another type of bullet "proof" glass made from acrylic - it is the kind from which a bullet will likely bounce rather than be absorbed

also the rating system from the UL requires it being able to take three of the rated bullets in a triangle of I think 2 inch side length - and I plan to just start with the rated shotgun, then see if it takes a .44

the rest is simply for fun after that

Sulaiman

Thu Jul 30 2009, 05:34AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

The most important thing is ...................

video/slo-mo/freeze photography and posting it here for us to see !

Hon1nbo

Sat Sept 05 2009, 11:17PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

I made it to the range today, and I was in shock and awe at the glass performance - first, as expected, the rifles went right through - but we used full rounds and from a close distance, and this glass is not meant for rifles

second, once we switched to handguns the difference was IMMEDIATE! not a single handgun round went through, one of the 1-x12 inch pieces was shot at least six times and it wasn't until the last shot that the glass failed but still did NOT let the bullet through! (in the initial shots, there were no indentions greater than 1/10 of an inch. and most of the damage was caused AFTER failure when the glass struck the ground

we also took a 30-06 and a .308 to Apples, and a 20ga slug to a Watermelon (I was about five-seven feet from that one when I shot it!)

video should be up in a few days, all edited and time-warp like - but unfortunately my camera was not fast enough to get a clear shot of the bullet in frame because there was not enough light out and the camera won't go to a high enough frame rate to do it without enough light to get even a single frame

however, you guys should love the videos of the watermelon and apples... I'm thinking of Finale 1812 Overture, but it might be a little cliche in my movies...

Hon1nbo

Thu Sept 10 2009, 10:06PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

sorry for not getting photos and videos of the glass up yet, photographing these impact patterns is tricky and the video files are bogging my computer so I must use the school computers

for now, here is the video of the Watermelon and an attempt at Apples from YouTube

since my high speed camera cannot photograph the apples well enough, I will go again to the range and use my Custom High Speed Photography Setup with a contact sensor a few feet in front of the Apple, out of frame, and have the bullet penetrate it

I have to find a camera for rent that has a fast enough Shutter Response Time though!

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