Why Don’t Car Windshields Shatter?

When considering why car windshields shatter, looking at how they behave under various extreme conditions is useful. You might recall scenes from movies where a villain shoots at a car’s windshield, and the bullet only creates a small cracked spot instead of shattering the glass entirely. Or, you may have seen depictions of crashes where the car windshield ends up severely cracked due to the collision but does not completely break, while all the car windows are broken and shattered.

These scenarios highlight car windshields’ unique construction and durability compared to other vehicle windows. Windshields are typically made from laminated glass, which consists of two glass layers bonded with a plastic interlayer. This design is specifically engineered to prevent the windshield from shattering into dangerous pieces upon impact. In the event of a bullet strike or a collision, the windshield may crack or even develop a web-like pattern of breaks, but it usually remains intact, preventing the glass from causing additional injuries.

Why Is That?

The simple answer is the windshield is built to be more resilient than other car windows to protect the driver and passengers.

A Brief History of Car Windshields

In the beginning, when cars first came on the scene, windshields were made of mundane plate glass. This worked fine for a while when cars were few, mostly because they were expensive and owned by the rich. However, it wasn’t until they became widespread and started crashing through reckless driving that the problem with ordinary glass became evident. The glass would shatter into multiple bits, severely injuring the passengers and the nearby pedestrians. If the impact were really strong, people would sometimes even go through the glass. Undoubtedly this posed a great safety risk.

Car Windshields Shatter

In 1903, while working in his lab, French chemist Edouard Benedictus accidentally dropped one of his cellulose-coated beakers. He noticed that, after the fall, the glass pieces clung together and more or less retained the same shape. Through intensive research and application, he was able to come up with a glass laminate prototype. By laminating the glass, he made it several times stronger and more resistant to damage.

Soon after, auto manufacturers started utilizing his invention to strengthen their windshields.

Over time, as technology has continued to evolve, his prototype has been tweaked and improved upon tremendously.

Today, windshields consist of two thin layers of glass with a thin layer of resin called polyvinyl butyral (PVB) holding the layers together.

In the event of an accident, the glass holds on to the resin layer as opposed to shattering it into shards and flying all over. This makes it safer for the passengers and everyone near the site.

Other Benefits of Laminated Glass

By including a layer of resin into the glass, windshields can last much longer than they initially did. Their longevity and durability mean car owners can carry out replacements after long periods. The windshield can also withstand a wide range of fluctuating temperatures without cracking, a phenomenon uncommon to ordinary glass.

The resin in the glass also provides added protection against UV rays. UV rays are responsible for causing a variety of skin cancers and mutations. Finally, laminated glass is relatively inexpensive. This is good news to car owners because they get to spend less on repairs, and, in case a full replacement is required, owners don’t have to foot exorbitant costs.

Without a doubt, Edouard Benedictus’ accidental invention has saved millions of lives on and off the road. It laid a solid foundation for the safety glass that’s used in all vehicles today.

Bama Auto Glass offers high-quality windshield repair and replacement services. For more inquiries about our services and a quote please contact us!