I actually sat on an iPad Pro and bent it. It bent back. 
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.
Yes but you don’t really want absolute strength for screens. They’re not designed to catch bricks or bullets like windscreens and bullet proof glass.
You need maximum surface hardness with some ability to bend. Most of the things that screw up screens are tiny sharp impacts, scratches and bending in real usage. Thus you end up with various ceramic glass hybrids rather than laminates. All laminates do in this circumstance is chip irreparably.
Erm, no ceramic glass hybrids here, whatever the marketing wank says. Gorilla glass and friends are "
chemically toughened glass" where some of the atoms in the surface layer of glass have been replaced by physically bigger atoms* while leaving the underlying bulk glass untouched, thus building in some compressive force into the outer layer of the glass. The glass remains roughly as hard or soft as it was in the beginning. It still scratches, but the compressive forces in the outer layer close the scratches after they have happened so that they don't propagate and turn into cracks.
So your
toughened glass actual gets as many scratches as your untoughened glass you just don't see them because they are either squeezed shut (a minor effect) or because scratches too small to see don't propagate into cracks that are big enough to see, driven by Griffith crack propagation (where bonds break, releasing the surface energy of the material, which breaks more bonds, which releases more surface energy etc. etc.). There is a critical length of crack in any material where if the crack stops forming before reaching that length you're OK, if it doesn't the crack propagates to catastrophic failure. For the details in full see "The New Science of Strong Materials
Or why you don't fall through the floor" by J.E. Gordon, a book everybody who aspires to call themselves an engineer ought to have read. Similar processes underlie why glass fibres aren't brittle, and why combining brittle plastic resins (epoxy, polyester) with floppy but strong fibres (carbon fibre, glass fibre) creates tough materials, it's all about stopping
crack propagation.
* The classic way of doing this is to put soda glass into a fused potassium salt and leave it there for a while. Some sodium atoms leach out of the glass, some potassium atoms which are larger than sodium atoms leach in (aided by the higher temperature). When you take it out and it all cools down the potassium atoms wedged into the glass apply a compressive force to the outer layer, but the inner layer that was too far away hasn't had any diffusion and so acts as the backbone for the (now slightly larger but still intimately attached) outer layer of glass to push against. The secret sauce of Gorilla glass and all the other proprietary chemically toughed glasses is what species you infuse, and how. Some toughened glasses are made with deep ion deposition
a la semiconductor doping.
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