Bullet-resistant glass is a glass product most commonly comprised of sheets of silica glass laminated to layers of polycarbonate with bonding ‘interlayers’ between them. These transparent materials together provide excellent ballistic protection.
At first glance, bullet-resistant glass may look very much like standard window glass; however, unlike standard windows, bullet-resistant glass is designed to withstand (“defeat”) one or several impacts from bullets. Of course, the ability of bullet-resistant glass to defeat attack depends on several variables including the type (caliber) of weapon used and thickness and composition of the ballistic glass.
Bullet-resistant glass is widely used not only by the military (architectural and vehicular) but also in government buildings such as prisons and courthouses as well as commercial buildings including banks and other high-value, high-risk institutions, residences and vehicles like cash transit trucks.
How it Works?
When struck by a bullet, the layers of glass and polycarbonate absorb and disperse the kinetic energy of the moving projectile.
The layers exposed to the projectile shatter, dissipating energy. Energy is also absorbed across the surfaces of the polycarbonate layers. As energy is absorbed and dispersed, the projectile slows until stopped, provided that a sufficient mass of ballistic material is present.
Threat Level and Test Procedures
In order to properly design bullet-resistant glass, required mass is calculated based on the characteristics of the specific threat(s) to be defeated. Projectile mass, shape and velocity (caliber), as well as number of strikes and spacing between strikes are all taken into consideration when designing the ballistic glass. Ballistic glass can also be designed to defeat the pressure waves that emanate from a blast, along with the fragments (shrapnel) often created by the blast. Tests are conducted to confirm the ballistic performance of selected materials against identified threats.
