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Scientists develop 'unbreakable' glass almost as tough as steel

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Re: Scientists develop 'unbreakable' glass almost as tough as steel

#61

Post by vlehto »

Someone1234 wrote: post #9

This is cool regardless. But I am interested in cost and weight. If it is too costly we might only see it used in niche applications (e.g. aircraft windows?). But even then if it weighs more than regular glass it may not even be utilised there. I'd like to see it used on vehicle front windshields, cracks are a constant pain in the butt, and they can leave the rear window and side windows as regular glass for emergenc…

Glass has density of ~2,5 kg/liter. It's made of silica, that has density of ~2,6. This has about 50% of Alumina in it with typical density of ~4.

So it's likely it would be around 3,3. More than aluminum, less than titanium.

But it's supposedly about ~20 times more rigid than regular glass. For rigidity limited structure, you could make it so much thinner that you get significant weight savings. This could be important for glass fiber structures. Fiber vs. fiber, glass has been able to compete in strength with carbon fiber, but lack of rigidity is the downside. Increase of stiffness might allow for usage of stiffer "matrix" (glue that holds the fibers together). That should increase overall strength. This limitation exists because if matrix is stiffer than the fibers, the structure will rip itself apart under load.

For strength or hardness limited designs, impossible to say. The article says nothing about it. Alumina is one of the hardest substances around, but I would not make any assumptions based on that. Typically it's more about structure than the molecules involved.

For creep and fatigue resistant designs, bulk glasses are pretty useless because of their amorphous structure. Fibers can be used in fatigue situation though. Again the increase in stiffness and the possible increase of matrix stiffness could improve the situation. But the real thing here is how well the matrix can bind to the fibers. That again is impossible to tell.

Windshields? It's big trade off really. Soft amorphic materials scratch easily. (By definition "hardness" is resistance to identation. Just add movement and you have scratching.) Typically "hard" amorphic materials suffer from cracking. This is because hardness usually comes with decreased ductility. But fracture toughness is function of stiffness and ductility. So this material could(?!?) improve hardness while being about as easy cracking as old windshiels. This would be good idea as windshield is mostly mode of fracture limited design. (It matters more how your windshield breaks, than how much energy it takes to break it.)

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#62

Post by vlehto »

Natsu wrote: post #53
Johnny555 wrote: post #24

Earlier quoted context omitted.

I don't think that safely fracturing when struck by a human is the safety function referred to in the linked article - once a person hits the windshield, the primary safety mechanisms (seatbelts, airbags, and structural integrity of the car) have already failed, so whatever happens at the windshield will make little difference. What the article says is that the safety role of a windshield (besides not breaking into d…

Windshields are laminated safety glass, which it sounds like you might be confusing with tempered safety glass. There's a huge difference in how those break. Laminated glass remains in one solid mass held together by the plastic sheet in the middle, while tempered glass explodes into tiny pieces that are sharp but not overly harmful. Ordinary annealed glass breaks into long, dagger-like pieces that are dangerously sh…

I thought windshields are tempered and laminated. Not that it significantly changes what you said. Just explains why occasional shards flying away from windshields are not that sharp.

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#64

Post by daughart »

qnaal wrote: post #47
such_a_casual wrote: post #21

I wonder if it's safe to smoke out of.

aluminum is a known neurotoxin

Only at very high concentrations: Adverse neurological effects have been observed in rats and mice at doses of 100–200 mg Al/kg/day, while the USDA limit is 0.10–0.12 mg Al/kg/day for adult (25–30- and 70+-year-old) males and females. Aluminum is the 3rd most common element in the Earth's crust and humans have evolved given a certain level of environmental exposure. (http://www.atsdr.cdc.gov/toxprofiles/tp22-c2.pdf)

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#65

Post by blt »

vlehto wrote: post #52
blt wrote: post #37

Earlier quoted context omitted.

Don't think it's nitpicking at all. I came away unsure whether the new material is hard (scratch resistant) or tough (won't shatter when dropped). An article about a new material that doesn't make the distinction fails fundamentally.

You might find it interesting that toughness and "won't shatter when dropped" are different things. Toughness(G) = slowly absorb energy without fracture. Shattering is more dependable of: Fracture toughness(Kc) = (E*G)^0,5 Where E = modulus. That explains why plastics with low E shatter easily while being tough. Metals have additional hardening methods that allow them to go beyond this rule. PS. Your knowledge on the…

None taken, thanks for the info!

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#66

Post by Johnny555 »

Someone wrote: post #54
Johnny555 wrote: post #51

Earlier quoted context omitted.

Well, no my analysis points out that the main safety purpose of windshield glass is to protect the structural integrity of the occupant cage -- it can't both protect against outside impact and penetration while also being a soft cushion for peoples heads to impact.

A window could give way in either direction without being penetrated, for example by stretching out and permanently deforming. Risk for people inside is that it would give too much way, so that that pole hits your head.

If it's flexible it's not going to support the roof in a rollover -- the windshield is a structural part of the occupant cage.

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#68

Post by Natsu »

vlehto wrote: post #62
Natsu wrote: post #53

Earlier quoted context omitted.

Windshields are laminated safety glass, which it sounds like you might be confusing with tempered safety glass. There's a huge difference in how those break. Laminated glass remains in one solid mass held together by the plastic sheet in the middle, while tempered glass explodes into tiny pieces that are sharp but not overly harmful. Ordinary annealed glass breaks into long, dagger-like pieces that are dangerously sh…

I thought windshields are tempered and laminated. Not that it significantly changes what you said. Just explains why occasional shards flying away from windshields are not that sharp.

I have never heard of a glass that's tempered & laminated. I'm not sure you could temper a glass flat enough to laminate it, either--it moves on rollers during the entire tempering process to keep it (mostly) flat, but it's nowhere near as flat as it is coming from the float plant and distortion is measured as part of the QC process.

You also can't temper any laminate that I know of--the liner would simply melt and cause a mess in the furnace. Our tempering furnace operated in the 700-800F range.

They might seam the edges of the laminate, though, like you do with annealed glass before tempering. I didn't work with windshields, only window glass, including some 6mm clear tempered that went to Google.

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#69

Post by vlehto »

Natsu wrote: post #68
vlehto wrote: post #62

Earlier quoted context omitted.

I thought windshields are tempered and laminated. Not that it significantly changes what you said. Just explains why occasional shards flying away from windshields are not that sharp.

I have never heard of a glass that's tempered & laminated. I'm not sure you could temper a glass flat enough to laminate it, either--it moves on rollers during the entire tempering process to keep it (mostly) flat, but it's nowhere near as flat as it is coming from the float plant and distortion is measured as part of the QC process. You also can't temper any laminate that I know of--the liner would simply melt and c…

Tempered laminated exists. But I can't find anything about it being used in car windshields. My bad, sorry.

The way I would do it would be chemical tempering before laminating. Then you probably have lot less warping.

Re: Scientists develop 'unbreakable' glass almost as tough as steel

#70

Post by Natsu »

vlehto wrote: post #69
Natsu wrote: post #68

Earlier quoted context omitted.

I have never heard of a glass that's tempered & laminated. I'm not sure you could temper a glass flat enough to laminate it, either--it moves on rollers during the entire tempering process to keep it (mostly) flat, but it's nowhere near as flat as it is coming from the float plant and distortion is measured as part of the QC process. You also can't temper any laminate that I know of--the liner would simply melt and c…

Tempered laminated exists. But I can't find anything about it being used in car windshields. My bad, sorry. The way I would do it would be chemical tempering before laminating. Then you probably have lot less warping.

Yes, the break pattern of a windshield is consistent with annealed glass. If it were tempered, the entire window could become an opaque white whenever it was damaged by a rock and that just wouldn't be safe. Not that the 'spiderweb' pattern is easy to see through, but it's better than being fully opaque.

I'm not familiar with any tempered laminates as we never made such, but a chemical process sounds more reasonable than trying to get laminated glass through a tempering furnace or laminate two tempered lites.

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