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Volume 8, Issue 1        January/February 2006

Off the Line
   oem glass manufacturing news

RussCors@aol.com

 

Going Ballistics
by Russ Corsi

What is ballistics (armored) glass? Is this product bulletproof?

Although it is not known exactly when the first armored glass products were produced, it’s believed to be either immediately before or during World War II. With initial products appearing as tank gun sites, the federal government asked several glass manufacturers to develop bullet-resistant transparencies for presidential and select government vehicles. Relying primarily on aircraft technologies, the first bullet-resistant products featured multiple layers of glass (several inches thick) utilizing a CIP (cast in place) interlayer to glue the glass plies together. Vehicle door openings had to be radically altered to accept the glass while thick plies of steel were strategically secured to the vehicle to minimize the likelihood of a projectile entering it. Needless to say, radical modifications to the vehicles’ suspension systems were also required to accept the significant increase in weight. 

The successful launch of these initial government vehicles signaled the beginning of what is know as “bullet-proof” glass. In reality, there is no such thing, because someone will always develop a bigger and more powerful bullet designed to penetrate each and every version of upgraded “bullet-resistant” glass. 

Product innovations saw the multiple plies of glass and CIP evolve into the utilization of PVB and other sheet interlayers with the all-glass units; followed by the introduction of polycarbonate as the innermost ply of the laminate. The strength of the polycarbonate allowed the glass manufacturers to reduce the weight of the windows while offering the same degree of armored protection. The multiple layers of glass and interlayer absorb the energy of the projectile while the polycarbonate stops it from entering the vehicle. (It should be noted that the polycarbonate can be scratched easily, necessitating the application of a scratch resistant coating on the exposed surface.) 

Most quality glass manufacturers offer various “levels” of protection, through increasing the layers/thicknesses of the glass, interlayers and polycarbonate. Base products are designed to stop multiple hits of 9 mm rounds while the high end products can be expected to stop multiple hits from 7.62 M or .30 caliber rounds.

Individuals who purchase armored vehicles typically prefer that their vehicle not give any outward appearance that it is “special.” Glass color and tints will usually give the same appearance as the normal OEM product. Typically, even the ceramic peripheral paint bands duplicate the original product. In addition, the glass is required to exhibit no more distortion than the typical original equipment product. 

Many vehicle modifiers are now using multiple plies of a lighter fiber glass product instead of the traditional, heavier steel products in many of the non-glass areas. As one might expect, blowout-resistant tires are also added during the retrofitting process. 

The auto glass replacement industry needs to be aware that armored glass cannot be retrofitted into a conventional glass opening on the average citizen’s vehicle. In addition, replacing armored glass is no easy task. In the event that a customer shows up at your shop with a broken piece of glass that the glass technician has determined is bullet resistant, the tech should immediately advise the customer to go back to the vehicle supplier to have the glass replaced. Most glass suppliers are contractually required to sell the armored glass only to the companies that built/modified the vehicles in the first place. So even if the technician is skilled enough to replace the damaged glass, it would be very difficult, if not impossible, to acquire the replacement glass. 

Although demand for armored personal vehicles may not be as high as it is in the Middle East and other dangerous parts of the world, there is a growing trend in North America to add laminated door glass to many new vehicles as well as to retrofit existing ones that did not come off the assembly line with laminated glass. Marketed as a “smash-and-grab” deterrent, this product also significantly reduces the noise level in the vehicle and the amount of UV rays. The glass plies are typically heat-strengthened (sort of between annealed and fully tempered) with the overall glass thickness thin enough to fit in normal door glass channels. Although this product does not stop bullet rounds, it does make it a little more difficult for a thief to break into the vehicle to either steal it or remove the contents. 

Russ Corsi retired as manager, technical services, from PPG Industries’ Automotive Replacement Glass business unit after 31 years in the glass industry. He now serves as a consultant to the industry. 


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