Bullet Proof Materials By Kevin Helms, Josh Borrajo, Karan Kanagasabapathy, Raghid Mardini ENGR45, Fall 2011 SRJC.

Bullet Proof Materials

By Kevin Helms, Josh Borrajo, Karan Kanagasabapathy, Raghid Mardini

ENGR45, Fall 2011SRJC

Bullet Proof Glass

Bulletproof glass is an optically transparent material that is resistant to being penetrated by bullets.

It’s better referred to as bullet resistant glass, because it’s not completely impenetrable.

It has applications in places where you need the protection of a bullet resistant material, without sacrificing the advantage of optical clarity.

For example it has uses in the military, defense and security, and in transaction windows at places like banks, gas stations, and other business that have a high probability of being robbed.

It’s made out of multiple materials layered and joined together, because no one material has the properties needed to stop a bullet.

http://www.atkinsonsmirrorandglass.com/glassgeek/laminated-glass.shtml

Polycarbonate Polycarbonate is a thermoplastic polymer.

Polymers are large molecules composed of repeating structural units in long chains.

There are both natural and synthetic polymers. Examples of natural polymers include wood, rubber, cotton, wool, leather, and silk. Synthetic examples include polycarbonate, plexiglass, and PVC.

Thermoplastic polymers are a type of polymer than liquefy when heated and harden when cooled, a process that is completely reversible and may be repeated.

Polycarbonate has an ideal application in bulletproof glass, in that it has a very high strength, and is also optically transparent.

Polycarbonate is often used as the “soft” material in bulletproof glass because it can flex back while holding shards of broken glass in place.

Polycarbonate is 30x stronger than acrylic, which is 17x stronger than a sheet of glass of equal thickness.

http://polycarbonate-pc-sheets.com/polycarbonate-sheets-pc-sheets/polycarbonate-solid-sheet/

Laminated Glass Laminated Glass is a type of safety glass that holds together when shattered.

Laminated glass is treated with a layer of polyvinyl butyral that holds the pieces together when it’s shattered.

Polyvinyl butyral is a resin that can provide a strong bond between two layers of material. It’s tough and ductile, which when bonded between two layers of glass, prevents the brittle cracks from passing from one side of the laminate to the other.

This makes the glass stronger, and also prevents it from breaking into large sharp pieces when it does fracture.

It’s commonly used in windshields in cars.


http://en.wikipedia.org/wiki/File:Windshield-spiderweb.jpg

How It’s MadeThe two (or more) materials are then layered and molded together under heat and pressure to create a solid block of bullet resistant material.

Most often it’s just layers of glass, PVB(the material they laminate glass to make it laminated glass), and polycarbonate.

However different manufacturers have different formulas for making their own brands of bullet proof glass which could differ by layering, materials used or both.

Depending on how it’s made and the thickness of the final product, the glass is rated on the level of protection it offers.

http://glassshieldco.com/en/production/

How It WorksGlass is brittle and it does not have a good orderly crystalline structure. If it did, it would be like a metal steel, where it dents and deforms instead of shattering.

This allows the glass to absorb the bullet’s energy by transferring the kinetic energy of the bullet into shattering the glass.

The softer plastic layer reinforces the glass by holding it in place and allowing the glass to flex back as it absorbs the impact.

The polycarbonate and laminate also spreads the force of the bullet laterally across the entire glass surface.

Layering these in multiple sheets allows the window to use properties of both materials more effectively; such as the glass on the backside shattering while the undamaged Plexiglas holds together the window. This also allows the glass to stop more that one bullet.

Since polycarbonate is very strong, and it does not shatter like glass it’s an excellent candidate for bulletproofing.

http://www.pointblanksolutionsinc.com/paca/HowhardArmorWorks.php

Our ExperimentOriginally wanted to test different materials, of different thicknesses, in different series of layers.

We also wanted to test with two types of guns and multiple shots.

However too expensive, and time consuming.

Small scale experiment with BB gun.

We decided to use Plexiglas (acrylic) and regular glass.

Wanted to test how well these materials stood up to bullets, and put the current technique to the test to try and understand how hard and soft layering works.

Our Experiment (Small Scale)

First we tested method using a BB gun

Used basic concept of bullet proof glass and layered hard material (aluminum foil) and soft material (saran wrap).

Projectile penetrated differently based on layer combinations

Results of BB gun testing

SSHH (Went through)

HHSS (Went through)

HSHS (Went through)

SHSH (Went through)

SHSHS (Went through first four layers)

HSHSH (Only went through first layer of Aluminum)

It took 4 layers of Aluminum foil alone to stop the BB

or and 8 layers of only plastic wrap to stop BB.

Large Scale Set Up

Used Plexiglas and standard glass in the place of polycarbonate and tempered glass.

¼ inch thickness

More affordable, but much weaker.

Used .22 mm rifle.

Fired 1 bullet at each of the 7 different set-ups from about 10 meters away.

Set-upsA: 1 layer of acrylic

AA: 2 layers of acrylic

GG: 2 layers of glass

GA: 2 layers (glass/acrylic)

GAGA: 4 layers (glass/acrylic/glass/acrylic)

AGAG: 4 layers (acrylic/glass/acrylic/glass)

GGAA: 4 layers (glass/glass/acrylic/acrylic)

G=Glass A=Acrylic

A

AA

The bullet went through the backboard, which means AA is too weak to stop the bullet.

GG

Bullet bounced off wood, which means that GG is more effective than AA.

GA

Bullet bounce off backboard, with less damage to the window. The ‘A’ layer supported the glass

AGAG

Stopped the bullet, but the back glass shattered; not practical.

GAGA

Stopped the bullet with no interior damage.

GGAA

Stopped the bullet. Same concept as GA, but we had to increase thickness to stop bullet.

What we found out

Karan likes guns!

Alternating layers is more effective.

Having the hard material first was much more effective.

Acrylic instead of polycarbonate still allowed us to stop a bullet, but we had to increase thickness

Glass shattering absorbs most of the impact, and in most trials the Plexiglas was unaffected.

Other applications!

Bullet proof glass in aircrafts

Partitioning followed by integration

http://www.ideationtriz.com/images/Bullet-proof_windows.gif

• Bullet-proof glass used on fighter aircraft initially had a serious defect. When a bullet hits the glass a network of cracks would form and obstruct vision.

• Now the windows are formed of smaller panes of glass, cemented to an acrylic plastic sheet. Transparent adhesive is used to join the edges of the glass panes. When a bullet hits, only the affected pane is covered by cracks.

• Think about possible nanotechnology applications!

ALONALON is a special variant of alumina (aluminum oxynitride). A white chalk-like powder is heated to thousands of degrees in a furnace and treated with nitrogen in a process that allows the ALON to turn into a transparent material which - similar to other ceramics - has a rigid crystalline structure that gives it strength.

When polished to remove tiny surface defects, the ALON material resembles sapphire - a gem prized for its hardness and resistance to scratches.

ALON has proven to be a remarkable bullet-resilient material. In tests, a "sandwich" of transparent ALON, glass and a polymer laminate survived multiple hits from .30-caliber armor.

The difference: The ALON laminate provides the same antiballistic performance at half the weight comparing it with traditional bulletproof glass materials.

One-way Bulletproof GlassWhat is it made of?

One-way bullet-resistant glass is manufactured by creating a brittle layer coated with a flexible material only on one side.

Another method is by making a series of:polycarbonate

acrylic

glass layers merged in a special manufacturing process

Held together by special glue

How does it workONE WAY SIDE

Polycarbonate material compresses, acrylic stretches

Bullet passes through soft polycarbonate layer and into acrylic layer which weakens as it stretches

Bullet shatters acrylic, continuing with no loss of velocity or deflection

PROTECTIVE SIDE

When bullet strikes the acrylic outer layer (brittle, but very strong when compressed), it compresses, denses/strengthens, and absorbs/distributes the energy.

The polycarbonate layer, which has flexible characteristics, stretches as it dissipates the remaining bullet energy with no full penetration

Spider webbing occurs on impact side, but inside glass remains smooth and undamaged.

http://www.thearmourgroup.com/images/products/glass/hdr_productspage.jpg

More Applications!Gaddafi’s dictator auditorium!

Popemobile!

http://upload.wikimedia.org/wikipedia/commons/0/03/Popemobile_passes_the_White_House.jpg

http://cdn6.wn.com/pd/2f/01/f335aba948225ff3bef0ddb0b866_grande.jpg

Special ThanksArch’s Glass

Tap Plastics

Dan

Sources


http://www.pointblanksolutionsinc.com/paca/HowhardArmorWorks.php


http://abcnews.go.com/Technology/FutureTech/story?id=1245087&page=1