I have a Marsh grapefruit tree, fruiting now (southern hemisphere) as it happens, and I note that it produces particularly pithy progeny. (Ignoring for the moment that Pomelo is one of the parents of the modern grapefruit.)
I don't have a convenient 10 metre drop to test this, and while I have no reason to doubt the veracity of this citation, I'm now consumed with curiosity why this plant has evolved to have this feature.
I expect it's quite an expensive adaptation, and given that modern specimens are the result of a lot of cross-breeding over the years to have juicier pulp and a lower ratio of skin/pith to pulp (ie. reduced resistance to damage) it presumably was even more expensive in ancestor plants.
Standard fruit purpose is to have animals unwittingly propagate the plant -- entice something to eat the fruit, and some time / distance later, deposit the seeds in a fertiliser ball. How does protecting the pulp from these kind of damage assist with that -- unless ancestor trees were spectacularly tall, and ancestor consumers fantastically fastidious on fruit quality.
https://hortscans.ces.ncsu.edu/uploads/t/h/thermal__51bf44b0...
It's not clear why this matters from the paper, in that it sounds like (but not spelled out) that they are perhaps trying to refrigerate fruit for transport, where the transport itself is not actively refrigerated, merely insulated, so the reduction to target temperature has to occur before shipping. However this was published in 1970, and I'd assume in that part of the world refrigerated shipping and (large) storage was not uncommon?
Aside #1 - undamaged grapefruit will happily store at room temperature for 6 weeks or more, and be the tastier for it.
Aside #2 - received wisdom is that grapefruit, and perhaps most citrus, benefit from one or more frosts to 'sweeten up', though I have never understood the mechanisms for this claim, or how high-water fruit does not burst its vesicles and then deteriorate rapidly.
TFA and this paper you cited may speak to the latter (the fruit content does not freeze overnight as the thermal inertia is so high), and might partially debunk the former.
> fantastically fastidious on fruit quality
Great alliterations. Great writing all around. This just made my night.
https://en.wikipedia.org/wiki/Pomelo#/media/File:Citrus_gran...
Flavor-wise it undoubtedly is.
Grapefruit didn't evolve naturally. In fact, it's only a couple of hundred years old. It's the way it is because of human intervention.
Grapefruit are a cross, probably, of pomelo and a sweet orange - as you say, not all that long ago. While some grapefruit varieties are quite pithy, pomelos (that I've seen) are very pithy - hence the 'this can only have been even more expensive a protective layer in earlier versions of this plant'.
The question still stands - why is this adaptation useful, given it's probably expensive. (That assumption of mine may be entirely wrong.)
Early species would have been shorter, and all species in the history of this would have fruited long before the individual trees reached 10 metres (I'm guessing even in ideal conditions that implies 10+ years growth). Most would-be consumers of the fruit would be able to reach fruit within the first metre or so (if unable to climb or fly) and anywhere in the tree otherwise.
> "Security applications such as doors or barriers (as protection from forcible entry attacks) are obvious ones. However, our material technology could also be useful for enhancing the cutting resistance of shoe soles or protective clothing. Workers could benefit from non-cuttable elbow pads or forearm guards in environments with industrial tools."
As someone who cares so much about digital security, physical security feels good.
It'd make a very heavy but uncuttable door, but you can't make hinges or locks out of it. It would be a good material to make safes out of; those already have thick walls of composite materials designed to blunt drill bits.
Is there any reason to think that it's impossible to scale it down? e.g. for PPE, 5mm ceramic spheres in a 1cm-thick Aluminimum foam with some 1mm steel plates on either side?
sounds like the modern "ceramic in a metal matrix" tank armor:
https://en.wikipedia.org/wiki/Chobham_armour
"The (pulverised) ceramic also strongly abrades any penetrator. Against lighter projectiles the hardness of the tiles causes a "shatter gap" effect: a higher velocity will, within a certain velocity range (the "gap"), not lead to a deeper penetration but destroy the projectile itself instead."
From the article on the material
"Water jets were also found to be ineffective because the curved surfaces of the ceramic spheres widen the jet, which substantially reduces its speed and weakens its cutting capacity."
Not just water jet, the ceramic/metal armor withstands even shaped charge jet :
"Because the ceramic is so brittle the entrance channel of a shaped charge jet is not smooth—as it would be when penetrating a metal—but ragged, causing extreme asymmetric pressures which disturb the geometry of the jet, on which its penetrative capabilities are critically dependent as its mass is relatively low. This initiates a vicious circle as the disturbed jet causes still greater irregularities in the ceramic, until in the end it is defeated. The newer composites, though tougher, optimise this effect as tiles made with them have a layered internal structure conducive to it, causing "crack deflection".[2] This mechanism—using the jet's own energy against it—has caused the effects of Chobham to be compared to those of reactive armour."
It was abandoned not because ineffectiveness but because construction difficulties, uniformity of the embedded spheres was hard to maintain
If you have a nice road bike with very clean tires people generally will not mind you bringing it into places with you consistently.
No matter how good your lock is, if somebody REALLY wants the bike (for the value of its components) they'll just saw the frame in half.
Edit: I am wrong!
Of course, maybe a core of this stuff with an outer shell of hardened steel.
I remember hearing about thieves spraying down those u-lock style locks with refrigerant, then tapping them with a hammer. They would shatter like glass.
Safes and vaults might be a good application.
Anyone that owns heavy equipment carries insurance covering damage, theft, and liability. Otherwise it’s rented and Sunbelt or whoever is on the hook to replace it.
Safe and vaults, sure.
What about an angle grinder disc made of this new material?
One way to make something resist abrasives is for it to be/sustain very high temperatures. If you can survive a hotter temperature than the abrasive (quite low for diamond, higher for sapphire) then it will be much less effective.
When pausing the video it looks like a conventional cut off wheel.
Diamond blades are not especially good at cutting. They only used when absolutely necessary, ie when your material is extremely hard. Diamond sublimates at low temperatures, it dulls quickly because of the fracture planes, and it's so weak and brittle that only tiny grains can survive being used to cut.
The alumina spheres they use are softer than diamond, but handle the cutting environment much better. Zirconia wheels handle cutting even better (up to 10x better) than alumina, but its softer. No idea what would be ideal.
Loading a power washer with some expensive abrasives would still cut this fairly quickly, and a thermic torch would cut it very quickly. Kind of requires you to not care about what's actually on the inside, though.
Also, even if you just looked at the angle grinder video, you can see the claims aren’t really as presented. It’s very cutable, it just happens to eventually dull the cutter eventually. That’s what, a 2” billet they have there?
For their demo on a similar thickness steel plate, I think that most people would have an extremely hard time getting that far in 17-4PH steel let alone SS6xx like Inconel or any one of 100 different steels.
Mostly you would stop from boredom even in a world where the grinder wasn’t similarly full or broken by the time you gave up.
I’m certain this is a novel approach with their “jelly filled with nuggets” but it’s still jelly... let me know when they embed nugget in steel.
My second was:
"New non-cuttable bike lock defeated by ______"
{freezing, shock, heat, _ }
Great engineering regardless, would love to work on a project like this.
It's odd that the title says "non-cuttable" and the tests they carried out in the article are all attacking it from one side, when most people will think of something like scissors that exert a high compressive force to shear the material.
To me, this material sounds more like it's highly abrasion-resistant than "non-cuttable".
The ceramic balls though, hoo boy. Here's one with a ceramic bearing ball vs a high speed air ram: https://www.youtube.com/watch?v=A6nvM7pYBGc
Now that is pretty interesting.
It seems they tuned the material to resist the angle grinder, drill and water jet but it would be interesting to see its ballistic resistance.
I note that they didn't really cover that territory, and wonder if that was lack of facilities or avoiding the tough questions.
Maybe in a sense, but I think not really. Bullet-proof vests aren't necessarily (usually?) stab proof. (And vice-versa of course.)
Being accepted in SciRep this material has to have some merit but I am unable to see it.
Is the structure even scalable to smaller objects? The other comments talking about bike looks did not read the paper it seems.
"Cutting resistant" might be a better description, and it is an interesting material regardless
Sounds like it works for applications where you need something to absorb "stopping" energy but without wearing out (too much)
This only talks about the cellular structure, not the overall material structure, but would this mean that the material would start to deform under a heavier strain? Does that mean it would make sense to not use this material alone, but rather with other materials to make a strong product, e.g. a bike lock with this material on the outside of a thin but rigid pure metal core?
So the material stops the cutting action, by having air sacs inside itself, where the particulate inside would melt from the friction, and cause the cutter blade to jam itself up.
People do that? Also, how does it work?
Edit: The principle is actually somewhat similar to the anti-drill protection on door locks - a small disc in front of the lock with a slit that the key goes through. The disc makes it hard to drill through the lock, because it spins together with the drill.
What if you can't get your picks into the keyhole?
I saw a lock that had a tubular key, and an airlock-like mechanism between the place the actual keyhole and the opening for you to insert the key. You would insert the key, and then activate the airlock-like mechanism which would transport the key to the keyhole.
There was then a mechanism to rotate the thing that was holding the key so as to unlock the lock.
The actual keyhole in this lock was never exposed to the outside.
They're probably breaking in hoping to steal tools to sell. If they had decent tools they would have already sold them. It's not impossible but well-equipped tweakers are far less likely than other kinds of thief.
On the other hand they're batshit crazy enough to try other means, why bother trying to break into a storage unit when you can chain the door handle to your (also stolen) car and rip the whole unit door off.
Bullet proof vests?
Ammunition?
