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The Secret Strength of Gnashing Teeth:
The strength of teeth is told on the scale of millimeters. Porcelain smiles are kind of like ceramics—except that while china plates shatter when smashed against each other, our teeth don't, and it's because they are full of defects.
Those defects are what inspired the latest paper led by Susanta Ghosh, assistant professor in the Department of Mechanical Engineering-Engineering Mechanics. The research came out recently in the journal Mechanics of Materials. Along with a team of dedicated graduate students—Upendra Yadav, Mark Coldren and Praveen Bulusu—and fellow mechanical engineer Trisha Sain, Ghosh examined what's called the microarchitecture of brittle materials like glass and ceramics.
"Since the time of alchemists people have tried to create new materials," Ghosh said. "What they did was at the chemical level and we work at the microscale. Changing the geometries—the microarchitecture—of a material is a new paradigm and opens up many new possibilities because we're working with well-known materials."
[...] Stronger glass brings us back to teeth—and seashells. On the micro level, the primary hard and brittle components of teeth and shells have weak interfaces or defects. These interfaces are filled with soft polymers. As teeth gnash and shells bump, the soft spots cushion the hard plates, letting them slide past one another. Under further deformation, they get interlocked like hook-and-loop fasteners or Velcro, thus carrying huge loads. But while chewing, no one would be able to see the shape of a tooth change with the naked eye. The shifting microarchitecture happens on the scale of microns, and its interlocking structure rebounds until a sticky caramel or rogue popcorn kernel pushes the sliding plates to the breaking point.
That breaking point is what Ghosh studies. Researchers in the field have found in experiments that adding small defects to glass can increase the strength of the material 200 times over. That means that the soft defects slow down the failure, guiding the propagation of cracks, and increases the energy absorption in the brittle material.
"The failure process is irreversible and complicated because the architectures that trap the crack through a predetermined path can be curved and complex," Ghosh said. "The models we work with try to describe fracture propagation and the contact mechanics at the interface between two hard-brittle building blocks."
Better to bend than break.
(Score: 1, Insightful) by Anonymous Coward on Thursday September 12 2019, @08:20AM (3 children)
Needless to say, this is very interesting information although probably quite useless for most of us. But it tells you that composite materials are far superior.
But it's also funny how people view improvements as "defects". What is a permanent magnet but a large defective set of small magnets?
(Score: 2) by HiThere on Thursday September 12 2019, @06:02PM
No. It tells you that composite materials *CAN* be superior. At least if flexibility and shock resistance is important. This is usually, but not always, true.
The difference between "are superior" and "can be superior" is quite significant. Lots of composite materials are generally inferior. The ones that are superior have a supportive internal structure making them superior. And also just about everything that isn't man made is a composite material. Look closely at a block of granite, e.g.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by bzipitidoo on Friday September 13 2019, @02:42AM (1 child)
Dude, this is one of those overlooked areas of material science that could revolutionize a lot of things. Sea shells are hard, but unlike our porcelain and glass, they don't shatter. About the best we have been able to do is the car windshield, in which a layer of plastic mostly holds the pieces in place when something shatters it.
Imagine no more windows cracked in half or worse because one rock hit it. No more broken windows because a neighborhood kid hit a baseball through it. Dropping a dinner plate or drinking glass will seldom break it. It'd be bigger than the switch from silverware to stainless steelware. You may have heard of the crap our grandparents had to do to maintain the silverware-- that whole "polishing the silver" thing that we no longer have to bother with, because stainless steel is so much, much, much better. Another huge win would be stronger concrete slab foundations for buildings. Not good for foundation repair companies, but very good for everyone else.
And if all that's not enough, wouldn't this be fantastic for our smartphones and tablets? What's the top reason for smartphone replacement? Broken screen?
(Score: 0) by Anonymous Coward on Friday September 13 2019, @10:11AM
What about gorilla glass or bullet proof glass.
https://en.wikipedia.org/wiki/Bulletproof_glass [wikipedia.org]
Also it should be noted that care needs to be taken to ensure the material is clear, transparent, and doesn't distort the light. If you have different materials mixed with different refractive indexes the light can get distorted.
Let's not forget that steel itself is an alloy.
Nothing in this paper is really all that new or revolutionary. Be wary of research that simply rediscovers the fact that the sky is blue and the grass is green. We know already.