Neither have I. Protecting Gorilla-glass with more Gorilla-glass always seemed like a pretty futile exercise to me.
McBryce.
Actually if stuck together with a non rigid adhesive it adds a lot of extra strength. That is why windshields and bulletproof glass are laminated.
Kind of. Car windscreens are mainly laminated to keep the glass together after it has shattered instead of having a wall of shards flying towards you if something breaks the windscreen.
McBryce.
It's both. They're stronger and large shards are kept captive. If it were just the shard protection, they'd be made of tempered glass that shatters into tiny grit like the side windows.
In many modern cars, the windshield(s) is/are actually part of the stiffness of the monocoque; it provides part of the roof crush support that used to be entirely provided by traditional A/B/C pillar design.
There was a lawsuit a decade or so back in which a replacement windshield popped out of a vehicle during an accident due to improper installation, and the roof of the vehicle collapsed breaking the driver's neck, when according to the manufacturer, it should have maintained integrity. Lots of investigation, enginerding, etc... but ultimately it was found that the windshield was cemented in place improperly, making the glass company liable.
mnem
Front windscreens are made of tempered glass and shatter in cubes just like the side glass, and although they do offer some physical strength / stiffness to the vehicle during a rollover, this factor is ignored in the mathematics because the pillars need to be able to support the weight of the vehicle even when all windows have failed. So it's a bonus, but not essential.
McBryce.
Car windscreens have not been made from toughened / tempered glass for many years. They are made from laminated glass with very few exceptions (it is mandated for car windscreens in most countries).
The added strength when bonded in is imprtant to many car designs.
EDIT, Cerebus beat me to it.
Cars still use tempered glass, as this is what makes the glass break in cubes rather than long sharp shards. Lamination is usually only on the front windscreen but some manufacturers have started using it on side windows too which can be a problem. The windscreen of course adds strength to the design, I wasn't saying it didn't. I was just pointing out that the pillars still have to be designed strong enough to support the vehicle if the glass is missing / broken. The stiffness, especially in X/Y plane torsion is the main structural component of the windscreen.
I think that you are talking about the older type of cars that used a rubber surround to hold the windscreen in place. Modern cars are laminated and are held in place by a special type of adhesive and designed to prevent passengers from going through the glass and being ejected into the path of the vehicle in the event of an accident. Hence, why you can often see vehicles which have massive cracks in their windscreens, and the screen has not shattered into the cubes you mention like the door windows do. The side windows are so designed as they may be used as an emergency escape hatch in the event of the doors jamming each other shut after an accident, and you can buy special glass hammers to keep in the car for such an incident and hitting the side glass with the pointed part of the hammer will cause the glass to shatter and present a means of escape from the vehicle.
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No, I mean current windscreens with bonding. Yes, they crack, but they don't shatter. The type of "chip" you get in a front windscreen could never happen with a standard pain of glass, even laminated glass, so the glass definitively has some level of tempering.
McBryce.
P.s. I am in discussions later this week with a Saint Cobain Engineer. I'll ask him exactly what process they are using on windscreens today.
P.p.s. Maybe I'm not explaining this properly, let's try with pictures. This is how standard glass breaks: Long sharp shards along the stress lines. And the other picture is how a windscreen breaks: Stress evenly spread across the entire surface. Not quite the "sugar effect" you get from breaking a side window, but far from standard glass too.
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Both those photos show plain un-toughened/tempered glass. One is two layers laminated together with more damage. Toughened glass has internal stresses that cause the whole piece to shatter once the oter layer is fractured. The fact that modern car windscreens can have a single crack is evidence that they are not toughened. Maybe we have a language / terminology issues here.
By toughened / tempered I mean glass that has been heated beyond it's transition temperature and then rapidly cooled.
It is easilly detected by viewing through a linear polarising filter. This causes the internal stress pattern to appear.