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Automobile Windshield As a Safety Device
By gguild | February 27, 2008
The Modern Automobile Windshield Is Actually A Safety Device
An automobile windshield is much more than just a piece of glass that protects a driver from the wind; it is much more than something that keeps the bugs away. A windshield, actually, is the key piece of safety equipment installed on any automobile. Believe it or not, it is actually the strength of the automobile windshield that allows some of the other restraining systems in today’s cars to function properly. The advancements in making a piece of glass for a modern windshield are important to the automobile both in terms of body strength and passenger safety.
Is All Automobile Windshield Glass The Same?
Often people use the terms, safety glass and laminated glass interchangeably, but they are not the same. Safety glass is layered and during the manufacturing process, what would become the outside surface of the glass is rapidly cooled. This causes internal stress in the layering of the glass. The strength of glass actually increases under stress. If safety glass is impacted enough to break, the stored stress on the inside of the glass is released and the glass essentially fractures and crumbles into countless little quarter-inch squares. When safety glass crumbles it does so without forming shards of sharp-edged glass than can be hurled through the passenger area of the car. Safety glass is typically used in the side windows and rear windows of automobiles but not in windshields.
How Is The Windshield Made Differenty Than Other Automobile Glass?
Windshields are made of laminated glass. The layers of glass are sandwiched over a material called PVB (poly vinyl butyral) that makes up the plasticized center sheet that is the core of the windshield. Without the PVB center, on impact the windshield would shatter, sending deadly spalling (flying glass shards) at high speeds into the driver and passenger area.
What Keeps An Automobile’s Windshield From Popping Out?
An automobile windshield is designed never to pop out. Windows in large vehicles such as trucks, buses, and recreational vehicles may be installed differently because of the rough-road shock and other flexing needed in that particular type of vehicle; however, in an automobile, a lot of bad things happen if the windshield pops out.
A special adhesive has been developed to satisfy the peculiar bonding needs of holding smooth windshield glass to rough metal car bodies. The adhesive, urethane, has some interesting properties. Urethane is very strong but it is also flexible (not rigid). Most adhesives that would strongly bond glass to metal and then be subjected to jarring winds and rough roads would cause the glass the crack and break under stress. Urethane allows for a flexible sealing around the glass the will not allow the metal to shock or stress it, but will also not allow the glass to work free. It binds with hundreds and hundreds of pounds of pressure per square inch.
What If The Automobile Windshield Does Pop Out?
Laminated windshield glass, combined with urethane glass bonding adhesive, is the key to strength and safety in the modern automobile. Aside from the practical, daily function of windshields shielding the driver from the winds, the other primary function of the windshield is to assure than the driver and passengers stay within the automobile at the time of a collision. Ten percent of automobile accidents involve rollovers that tend to pop windshields and windows and throw people from the vehicle. Statistics show that only about one in four people will survive an accident if thrown from the vehicle. Therefore, statistically, you have a four times better chance of survival in an accident if the windshield does not pop off the automobile and you are retained inside the passenger area.
Windshields Provide Structural Strength To The Automobile
Your windshield is actually one of your automobile’s primary safety devices. It adds both to the structural integrity of the automobile itself (especially the roof), and it helps to retain passengers inside the car. Most modern automobiles can have up to 40% of the exterior surrounding the passengers made up of glass, which is good because automotive glass is very strong and gets stronger under stress. In addition, about 20% of the overall structural strength of the car is in the windshield. In addition to holding out the weather, a properly mounted windshield keeps the roof of the automobile from collapsing such as would occur in a rollover accident. Besides the obvious damage of the roof caving in on the heads of the driver and passengers, a crushed roof can inhibit rescuers from getting to you in time. Other safety devices such as airbags are less effective without a strongly and properly bonded windshield on your automobile. Without a good bond at the windshield, the deployment of the airbag could pop the windshield and the useful protection the airbag provides would be expended out the hole and over the hood of the car.
How Important Is It That A Windshield Installer Be Specially Trained?
A properly trained professional is required to assure a properly installed windshield. Proper windshield installation is absolutely critical to safety. Since part of an automobile’s structural integrity comes from the strength of the glass surrounding the passengers and since that integrity is only maintained when the windshield is in place, a windshield that pops out because of inferior bonding materials can easily allow a passenger to be thrown or crushed.
Would you trust a high school kid at the car wash to replace your windshield? Of course not. Would you trust yourself to do it? Probably not. Then realize the importance of seeking an NGA trained and authorized technician to handle this task. It is far too important to treat lightly. Follow, to the letter, the advice for aftercare given by your technician. It is extremely important for the success of the bonding and the safety of you and your passengers.
Aren’t There Government Regulations Regarding Windshield Installation?
No. That is why the NGA certification is so important. Look for the logo. Ask for verification of certification. Body shops and glass shops can be held liable when not following standards, but by then, it’s too late. The unnecessary damage is done.
Automobile windshields are both passenger restraint systems and structural integrity enhancements—not just another piece of glass. Without a properly mounted and sealed windshield, your life is at risk while you travel down the road. In a serious accident, a professionally bonded windshield is the last barrier separating you and your family from tragedy,