Bullet-proof glass
2008-08-20

                                                                                               Bullet-proof glass

Security has been an international theme, whether ordinary people or heads of states, will be worried about security problems. And now face the rampant terrorists today, in particular the heads of state, whenever they travel time, they will take into account the problem of security, and their vehicles will must be especially protected, which is bullet-proof glass. What is bullet-proof glass

Strictly, bulletproof glass would be glass that is capable of stopping most manners of bullets fired at it. Such glass cannot currently be made in any usable thickness (if at all), so what is loosely called bulletproof glass is, within the industry, referred to as bullet-resistant glass. 

Bullet-resistant glass is usually constructed using a strong but transparent material such as polycarbonate thermoplastic or by using layers of laminated glass. The desired result is a material with an appearance and light-transmitting behavior of standard glass but offers varying degrees of protection from small arms fire. 

The polycarbonate layer, usually consisting of products such as Cyrolon, Lexan and Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet-resistant glass is usually 70–75 mm (2.8–3.0 in) thick.

Bullet-resistant glass constructed of laminated glass layers is built from glass sheets bonded together with polyvinyl butyric or polyurethane. This type of bullet-resistant glass has been in regular use on combat vehicles since World War II; it is typically about 100–120 mm (3.9–4.7 in) thick and is usually extremely heavy. How does "bulletproof" glass work The ability of bullet-resistant glass to stop a bullet is determined by the thickness of the glass. At first glance, bullet-resistant glass looks identical to an ordinary pane of glass, but that's where the similarities end. An ordinary piece of glass shatters when struck by a single bullet. Bullet resistant glass is designed to withstand one or several rounds of bullets depending on the thickness of the glass and the weapon being fired at it. So, what gives bullet-resistant glass the ability to stop bullets?

Different manufacturers make different variations of bullet-resistant glass, but it is basically made by layering a polycarbonate material between pieces of ordinary glass in a process called lamination. This process creates a glass-like material that is thicker than normal glass. Polycarbonate is a tough transparent plastic -- often known by the brand name Lexan, Tuffak or Cyrolon. Bullet-resistant glass is between 7 millimeters and 75 millimeters in thickness. A bullet fired at a sheet of bullet-resistant glass will pierce the outside layer of the glass, but the layered polycarbonate-glass material is able to absorb the bullet's energy and stop it before it exits the final layer. The ability of bullet-resistant glass to stop a bullet is determined by the thickness of the glass. A rifle bullet will collide with the glass with a lot more force than a bullet from a handgun, so a thicker piece of bullet-resistant glass would be needed to stop a rifle bullet as opposed to a handgun bullet.

There is also one-way bullet-resistant glass available, which has one side able to stop bullets, while the other side allows bullets to pass through it unaffected. This gives a person being shot at the ability to shoot back. This type of bullet-resistant glass is made by laminating a brittle sheet of material with a flexible material.

Imagine a car equipped with this one-way bullet-resistant glass. If a person outside the car shoots a bullet into the window, the bullet would strike the brittle side first. This brittle material would shatter around the point of impact and absorb some of the energy over a large area. The flexible material then absorbs the remaining energy of the bullet, stopping the bullet. A bullet fired from inside the same car would easily pass through the glass because the bullet's force is concentrated on a small area, which causes the material to flex. This causes the brittle material to break outwards, allowing the bullet to pierce the flexible material and strike its target. After the incident of 9.11, the United States has more to strengthen the security measures and technology. The improvement of bullet-resistant glass is as followed: Recent advances in bullet-resistant glass composition

U.S. military researchers are moving quickly to develop a new class of transparent amour incorporating aluminum oxynitride (Trade name: AlON) as the outside "strike plate" layer. It is much lighter and performs much better than traditional glass/polymer laminates. This allows aluminum oxynitride "glass" to defeat threats surpassing .50 caliber armor piercing rounds using material that is not prohibitively heavy.