Here’s how ‘bulletproof’ car windows are made – Jalopnik

When considering a new vehicle, the average buyer may want to research which popular car brands are known for safety. As such, they may ignore that regular automotive glass is a techno-chemical marvel made to withstand harsh conditions, suppress noise and protect occupants. Ballistic glass – the stuff of ‘bulletproof’ car windows – must (obviously) deal with specific forces far beyond standard car glass, but it is based on some of the same manufacturing principles as windshields.

‘Standard’ car glass is not one type of glass. It is designed to different specifications depending on where it is used in a vehicle. The glass of the rear and side windows is usually tempered, which means that it is manufactured using a thermal process in which the glass is heated to temperatures above 600 degrees Celsius during production. This makes it four to five times stronger than regular glass, while allowing it to break into small pieces from inside the vehicle, reducing the risk of injury to passengers.

Windshields go even further. They not only provide protection against UV rays and dirt, but also provide structural rigidity and tilt integrity. They are also the first thing a passenger airbag hits when it deploys. Windshields are usually a laminated sandwich of materials and are designed not to shatter thanks to a layer of polyvinyl butyral (PVB) resin pressed between sheets of glass for strength and flexibility.

Bulletproof glass – or more accurately bulletproof glass – takes similar signals from windshields. However, instead of being about 3mm thick, bulletproof glass can reach 39mm or more, with several layers of glass, polycarbonate and/or acrylic sheets designed to absorb energy and protect occupants from damage.

Bulletproof is a common term used to describe any glass that can stop a bullet, but technically resistance levels depend on the specifications the glass meets. Things like firearm types, ammunition, and bullet velocity can vary, so it’s impossible for all glass to be completely impenetrable. There are industry standards, such as UL 752 – which determine how many layers of resistance glass, PVB and other composites offer. This is why manufacturers will point out that “bulletproof” is the correct term – even though “bulletproof” is the term used to discuss the technology.

When it comes to stopping a bullet, bulletproof glass is meant to absorb the impact. In sports that require athletes to pass and catch, such as hockey, lacrosse, baseball and American football, having “soft hands” means they can safely control a moving puck or ball. This is exactly what bulletproof glass does, as the layers of glass and plastic work together to absorb a bullet’s momentum. The hard outer shell of glass or acrylic is the first barrier that cushions the initial impact of a bullet, causing it to deform and lose velocity. If that isn’t enough to stop the bullet, the subsequent layers will absorb the bullet’s travel.

Different manufacturers may use their own proprietary formulations and layer compositions, but the general idea of ​​softer center layers in bulletproof glass is the same: bend, but don’t break. As a bullet breaks through the outer shell, these connected inner layers will bend and act as a net that harnesses the bullet’s momentum. Each layer helps disperse the force of the bullet until it dissipates, causing it to stop.

These options may come with compromises. The thicker the shell and the more layers involved, the harder the glass can be to see through – and the heavier it can be. Many standard car windshields weigh about 25 pounds. For a windshield that can withstand a few gunshots of the highest caliber, that weight is closer to 500 pounds. That heaviness can require extensive adjustments to the frame, hinges and other components. But as technology evolves, some manufacturers are offering lighter designs that are even transferable between vehicles.

Making bulletproof car windows is only part of the armored vehicle equation. The rabbit hole of armored vehicle design can provide a speculative glimpse into the first presidential limousine, and it shows how Volvo upgraded its safety heritage by turning its XC60 and XC90 from normal SUVs into armored cars you can buy.