Modern windshields are typically made from a laminated safety glass. It’s comprised of two layers of glass heat pressed together with a thin layer of vinyl in between. This middle layer of windshield glass technology is what enables it to take the force of a stone without total destruction. Only the outer layer of glass will crack.
In the event of a more severe impact, the entire windshield may shatter, but will remain intact. The inner vinyl layer works as a sort of glue keeping the pieces bonded together. The side and rear windows of a vehicle are made of tempered glass. Heating the glass to very high temperatures and immediately cooling it, makes the glass becomes much stronger. This treatment means that it’s like to only shatter into very small, dull pieces to prevent injury.
One-way Bulletproof Glass in Armored Cars
Traditional bulletproof glass stops the passage of bullets from either side. One-way bulletproof glass, however, stops bullets from entering from the outside but allows them to exit from the inside. This protects the passengers inside an armored vehicle while allowing bodyguards to fire out of the vehicle.
One-way bulletproof glass is composed of two layers. The outside layer – on the threat side – is a brittle glass and the inside layer is a flexible polycarbonate. A bullet striking the brittle external layer causes the glass to shatter, absorbing some of the bullet’s energy by spreading the force over a larger area. The flexible polycarbonate layer then stops the bullet. Bullets shot from the inside of an armored car are able to penetrate the bulletproof glass because they strike the polycarbonate layer first with more focused energy. The brittle glass layer then breaks outward allowing the bullet to pass through with minor energy loss.
New Windshield Technology: “Nuclear Explosion-Proof Glass”
Recently, Tesla unveiled a new electric semi truck, complete with an “explosion-proof glass” windshield. The new Tesla armor glass has been shown to withstand the impact of a tow hitch without cracking. The news of explosion-proof glass has created a lot of interest from people who want to test its effectiveness.
The intention of the new glass is simply to reduce cracked windshields. Semis have a very large pane of glass and cracks can put them temporarily out of commission, costing drivers and their employers time and money.
The market for armored vehicles is quite broad. If you’re in need of additional protection, learn more about armoring your car with bulletproof security.
Photo by Vcx (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons