speedkar9

Modern vehicles have two main types of glass on the body, the front, laminated windshield, and the side tempered glass.
These are both considered "safety" glass, and work in different ways to protect occupants from getting hurt when they break.


The front windshield is made of laminated glass. That is, two layers of regular glass sandwiched around a thin laminate layer.
The glass is prepared per DOT standards as marked on the bottom right:



The thin laminate layer helps to keep the glass together when an object strikes and cracks the glass.
Here I attempt to break the windshield using a toothbrush I borrowed from my brother:



After a few blows, you can see how the glass has held together. The glass has broken into relatively large pieces surrounding the impact zone but is held together.



Breaking through the second layer of glass gives us an idea of the gooey laminate layer in between. This is meant to held the pieces of glass together when broken, and form a barrier against object penetration.
That's how it protects occupants.



The side glass on most (regular) vehicles is tempered. Tempering is a heat treatment process that makes the glass much stronger. It is also less expensive than laminated glass, due to its simple construction.
Tempering is also considered a safety glass.



Again, I demonstrate how the glass will break by striking it with my brother's toothbrush. This glass was noticably harder to bust than the front windshield.



Here we see that the glass breaks into millions of small pieces. It made quite a mess.



Smaller tiny pieces of glass aren't as sharp and won't cut or harm you as easily as big shards. I also noticed the glass bits were breaking up on its own and jumping around, as if the heat treatment had it under stress and it was releasing that built up energy.



And that's pretty much how the glass on your vehicle is made to keep you safe!

Hoovey689

iTrader: (16)

I knew about the laminate, just replaced my windshield which had a 4 foot long crack that I finally got around to taking care of. The tempering of the side windows is something I learned today.

"Borrowed" hah.

riredale

Every auto glovebox should have a tiny emergency hammer. It is used to break the window glass if the car should ever enter the water.

As several Mythbusters episodes demonstrated, this is the ONLY way to reliably survive water immersion. You don't wait, you immediately take off your seat belt (or cut it off with the sharp blade built into many emergency hammers), take off the seat belts of the passengers, and smash a side window, which will shatter into tiny pieces. Don't bother with the windshield, which won't shatter. Don't try to open a door; you won't be able to. Don't "wait" until the car is full of water.

This all has to be done in a matter of seconds, as the car will immediately flip upside-down as it descends to the bottom of the body of water and everyone will become disoriented and panic-stricken. You can't wait.

These little hammers are available all over. I bought a bunch of them (orange, about 6" long) a few years ago and gave them out as Christmas presents.

speedkar9

That's also a good point about tempered glass. It's easier to escape in an emergency.