Laminated Side Glass

"fink stinger" (finkstinger) 10/01/2013 at 12:47 • Filed to: None

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Another little nugged that jumped out at me during the flurry of terrible imagery from this weekend's motorcycle madness is that Range Rover apparently uses laminated glass in the side windows (highlight not mine as this image is from a new article that was pointing out the unfortunate wife and child):

Seems like we had this discussion about Bentley or Rolls a year or two ago, but I cannot find it and can't remember the details. Is this a luxury thing? It has to make windows much more expensive to design and manufacture when plain old safety glass is a perfectly acceptable solution for side glass. As an engineer, I can't think of an upside, but can come with quite a few downsides...which, as an engineer, troubles me.

Does anyone know why? To try to keep the unbelted fleshy blobs inside during rollovers? To render the Life Hammer completely ineffective during an underwater escape? To keep low-flying albatrosses or deer from smashing through? To make sure the side curtain air bags always have something to push against? (<=Sorry, had to throw a serious one in there)

Mattbob > fink stinger 10/01/2013 at 12:50

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Well safety glass isn't really all that safe. It's still pretty sharp. I would say it is to prevent glass from shotgunning in the occupants face and eyes.

Casper > fink stinger 10/01/2013 at 12:51

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I would propose the following thoughts:

A) Crushing a side window, even a laminated one, will make it flexible and move out of the way for an escape (windshields are different since they are glued in place).

B) Probably more for safety to keep flying glass and body parts inside the car. Might also be a theft deterrent.

Chris Clarke > fink stinger 10/01/2013 at 12:51

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From the way I understand it, its to protect the driver from being covered in shards of glass in the event that a thug/squid/asshat smashes in your window. Maybe that's not it.

TheOnelectronic > fink stinger 10/01/2013 at 12:53

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I thought safety glass WAS laminated glass. What's the difference?

fink stinger > TheOnelectronic 10/01/2013 at 12:58

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Well, you are right. It's an old habit that tempered==safety and laminated==laminated. There is a pretty decent description at http://en.wikipedia.org/wiki/Safety_gl…

Just substitute tempered for safety in my original post.

DasWauto > TheOnelectronic 10/01/2013 at 12:59

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Safety glass often just means it is tempered. Tempered glass breaks into a million tiny pieces rather than large sharp shards to minimize harm cause by the broken glass.

Windshields are laminated safety glass. Shatters into a million tiny pieces but is held together by the laminating plastic layer(s).

rotundapig > fink stinger 10/01/2013 at 13:01

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I would think it also does a better job of sound deadening/insulation.

fink stinger > Casper 10/01/2013 at 13:04

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To your point A: I have never tried to kick out a laminated side glass, but have tried to kick out plain tempered side glass...and it is pretty tough to do (read: practically impossible with hands or feet). A ball peen hammer knocks out tempered glass pretty handily, especially from the inside. It sure seems like knocking out laminated glass would be MUCH more difficult no matter what tool you were using.

To your point B: As a non-criminal, I didn't consider the theft component. You are right...it would make the "smash and grab" less likely.

Takuro Spirit > rotundapig 10/01/2013 at 13:08

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This.

Casper > fink stinger 10/01/2013 at 13:09

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Yeah, you won't be kicking out glass. I carry a Benchmade Triage as my "just in case" tool because it also has a glass break on it. If I were to use it to break a window like that, it would then let me start pulling the glass down (like in the picture).

This is actually why I always carry a knife with me... this and first aid situations. If I come across a car crash (as I have in the past) I want the option to break the glass with something other than a rock or my arm (probably breaking my arm in the process).

fink stinger > rotundapig 10/01/2013 at 13:11

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It's possible, but I have to think that the effects would be virtually negligible.

That does bring up the idea that maybe they are putting heating elements in for defrosting and/or UV coatings that would be better protected inside the glass than on the surface where they can be worn away with cleaning.

fink stinger > Casper 10/01/2013 at 13:21

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Now I am curious about how this stuff 'breaks'. Smashing out a windshield is not trivial. To break enough glass away that you could take a knife to the laminating layer means someone has really imparted a lot of energy into it...by hitting it really hard multiple times with something like a baseball bat or once with their entire body while going about 40-50 mph. Initially, you just get a bunch of larger cracks in the glass instead of the shower of 1/4" chips like with unlaminated tempered glass.

Does side glass behave like a windshield when you impact it? I guess one big difference would be that a windshield is glued into the structure and the side glass just floats in it's frame. From the video of those guys pounding it out with their helmets, it sure doesn't look like it just breaks and falls out of the way very easily.

Casper > fink stinger 10/01/2013 at 13:30

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No. The side windows are only attached at the base. Windshields are glued all the way around. So when you break a windshield it becomes flexible, but still glued in place. Side windows are not held by the top or sides, so when they become flexible they can be pulled down and in/out.

Glass is so hard because it stores massive amounts of energy in tension. That's why it's hard to break with a thrown object. The object transfers it's energy into the glass but the glass transfers even more energy back and bounces it off. Now, glass also shatters because a small flaw due to a crack or chip means the tension will be released in the form of large cracks as soon as it has opportunity. That is why if you want to break a window you need a fine, hard, point. That way you only have to overcome the energy of a very small surface point to break it.

Notbisondelta > fink stinger 10/01/2013 at 14:03

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There is also the chance of it just being tinted. Someone broke into my car like that and the window was still in one piece because of the tint film. And this was on a late 90's Corolla. And they were clearly beating on it to get in.

Kugelblitz > fink stinger 10/01/2013 at 15:53

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I noticed a few other broken windows when I altered the levels on a captured image here. I also saw Dad getting pummeled top left. Ugh.