liquid armor

[angelo]

http://www.military.com/NewsContent/0,13319,usa3_042104.00.html

Maybe we can improvise it?

But it would seem a little difficult if possible.

[Small Town]

Has anyone else here ever played with cornflour and water?

Now hear me out, mix them to form a thin paste and when you apply pressure it becomes hard, let go and its becomes fluid again. I'd say this technology is based on the same principles, only they use a much finer solid suspended in a different liquid.

That leads me to assume that once we fully understand the design it would be fairly simple to produce.

[mongo blongo]

Yes I agree with you. There is a name for the kind of liquid which behaves like a solid and a liquid but I can't remember.

[JoeJablomy]

What they're going for here is a thixotropic fluid (literally, a "shear-thickening fluid" that becomes more viscous as you apply more shear, like by moving things (i.e. fibers) through it). I don't know where to get <I>poly</I>ethylene glycol, but I think they said in an earlier paper that their silica particles came from Nissan Chemical, or somesuch. Just look for small, hard spherical particles. Lighter ones, like alumina, might be better.
I really don't know why this research deserves a prize, though. Unless there have been significant improvements, this stuff is still as heavy per protected area/level of protection as plain kevlar. Interestingly, the materials might be cheaper.
-----------------
In fact,
"The shear thickening fluid (STF) used in the targets is
composed of silica particles (Nissan Chemicals MP4540)
suspended in ethylene glycol, at a volume fraction of
approximately 0.57. The average particle diameter, as
measured using dynamic light scattering, was determined
to be 446 nm."

I guess you might be able to use anti-freeze (might; the news article said it was non-toxic).

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Have a :) nice day!

[nbk2000]

Nightstalker posted details of this a while back, under a thread about body armor, I believe, with more discussion.

[Jome skanish]

When I was a kid we used a stone-tumbler (strangely enough :-) to polish (sp?) stones. In the first stages of the process, where the stones basically just gets rounder, a ultra-hard powder (silicone carbide) is used. I don't know exactly how hard it is, but I've been told it's about as hard as saphire!
This could be used as the "powder" component of the armor.

One thing I'm wondering of is why the other component has to be liquid, perhaps any material that is non-brittle, "elasticly" soft and miscible with the powder could be used. I think I have a theory of how it works:

When the bullet hits the material, the "liquid" or whatever it is gets pressed out of the spaces between the powder, and the mechanical propeties changes from "particles that CAN move around eachother" to particles that cant, because they're slightly to close. When that happens, the material (suspension) acts as a solid and stops the bullet.

It's a bit OT, but I think I have read that the israelis had some kind of "explosive sheets" covering their tanks, (called "active armor) perhaps to mess-up the shape of any armor penetrating round hitting it. Could something like this be used to "air-bag" the force of a hit in the other material so that it does'nt hurt you?

[vulture]

Siliciumcarbide is nearly as hard as diamond, H9,6 vs H10 for diamond.
SiO2 = H7 for example.

I've been discussing this with Jacks Complete IIRC in another armor thread, the conclusion pretty much was that forming it into desired shape is nearly impossible.

[Harpoon]

Reactive armor or explosive reactive armour (ERA), is a type of armour used primarily on tanks to lessen the damage from explosions caused from missile warheads, exploding shellss, grenades, or launched bombs.
Reactive armor's protective mechanism involves producing an explosion or other such reaction when it is impacted by a weapon, "pushing back" against it. This is particularly effective against shaped charge warheads, in which the warhead directs a focused jet of molten metal against the armor; reactive armor's reaction disrupts the jet before it reaches the armor's surface.

Modern ERA such as the Russian Kontakt-5 is made up of "bricks" of explosive sandwiched between two metal plates. The plates are arranged in such a way as to move sideways rapidly when the explosive detonates. This will force an incoming KE-penetrator or shaped charge jet to cut through more armour than the thickness of the plating itself, since "new" plating is constantly fed into the penetrating body. A KE-penerator will also be subjected to powerful sideways forces, which might be large enough to cut the rod into two or more pieces. This will significantly reduce the penetrating capabilities of the penetrator, since the penetrating force will be dissipated over a larger volume of armour.

ERA bricks are used as add-on armour to the most vulnerable parts of an armoured vehicle or tank. They require fairly heavy armour on the vehicle itself, since the exploding ERA would otherwise damage the vehicle and injure or kill the personnel inside.

Recent research has produced the idea of Electric Reactive Armour, where the armour is made up of two electrically charged plates separated by an insulator. When an incoming body penetrates the two plates and closes the circuit, a high voltage jolt will supposedly vaporize the penetrator and significantly reduce the resulting penetration. It is not public knowledge whether this is supposed to function against both KE-penetrators and shaped charges, or shaped charges alone. This technology has yet to be introduced on any operational platform.


I believe that electric reactive armour has also been discussed on this forum...

[akinrog]

One thing I'm wondering of is why the other component has to be liquid, ......

Actually other component of this armor is not liquid but a gell-like compount. From the definition of thixotropy we understood that this type of compounds actually gell or emulsion type of substances. IMHO, the polyethylene glycol is not a long chain polymer otherwise it might set.

[Tuatara]

I have some Cab-o-Sil fumed silica in my chem collection. Its used as a thixotropic agent for thickening paint, so it may work for this application too. Any ideas on how one could test this sort of thing? I have no guns ...

[Wes80]

Its the wrong way around, thixotropic referes to it getting thinner with shear stress. Liquids that thicken due to shear stress are refered to as rheopectic or harden on impact as dilatant.

Dilatant liquids are what your after, I posted a topic on dilatant tamping quite a while ago.

[teshilo]

I listen what ,in XX sentury small wars guerillas used as field expedient armor
in armored cars sheep wool soaked water with little oil.Bullets very hardly penetrate these stuff.

[Jacks Complete]

The joy of having a liquid component is that you can make your armour really flexible. You bend, it bends. Yet when hit by a bullet, <i>it stops solid for only as long as it takes to stop the bullet!</i> :cool:

Makes your life far easier. Also, it is self-repairing, as it will flow under gravity to fill the hole (which hopefully isn't all the way through!) or dents, and you don't need to panic about dropping the trauma plate and shattering it, putting on a little weight, etc. It might even be slightly lighter.

Using SiC might work in this case, since you would want it to be a powder. The only problems might be if particle shape and size were a factor. SiC is a face centered cubic, which forms small cubes, whereas diamond forms rhombuses (iirc). I have no idea whether this would affect things, but it might.

As for the liquid, I vote for silly putty... :D

[Jome skanish]

Jacks Complete:
You are right. I I did not think of the particle shape of the solid powder! If the particles are more or less able to "roll away" when put under pressure, this will have great effect on their behavior when used in this form of armour. Cubes are more like spheres than rombs, and I guess they will not be as good.

The best "particle shape" would be cluster or needle formed cristalls, or perhaps thin sheets. One could perhaps use metal shavings and convert to something harder? That messed-up looking shape would be ideal for this purpose!

[Jacks Complete]

Indeed. Some cunningly constructed particle that was grown from fused silica or some other incredibly strong materials (on the nano scale) would be ideal. You would probably want something that looked like * or x, or perhaps a random shape like a snowflake, but in 3D. Of course, you might find it better to use something that gripped on one axis, but not another, so that it was more flexible in one direction.

[JoeJablomy]

I'm almost certain they use spherical particles, because kevlar at least is vulnerable to abrasion. If you have a bunch of small particles worked into it and then move around...

But as for 3-D stacking/interlocking shapes, there are probably a bunch of options. Some that come to mind are highly stellated tetrahedral shapes, or similar to two bars joined at the midpoints at 90 degree angles, possibly with the ends bent out.
Another problem with complicated shapes like these, though, is that they will be much more prone to breaking under impact because of all the bits sticking out, unlike round particles that will simply settle under the load unless it's right on top of them.

[Jacks Complete]

Isn't that a research topic and a half!

I think the worry about abrasion wouldn't be worth it. A nano-particle as hard as a diamond rubbing against another particle, whilst lubricated with some kind of fluid. It isn't going to be an issue. The wear rate will be tiny, much the same as it is in a car gearbox or whatever.

The nanoparticles will be far tougher than you would think - in fact they are almost indestructable. Think about trying to break sand. You just about can't, in compression. In bulk, it is glass, which is used for armoured glass, or as ceramic plates when crystalline. But I also know that coarse builders sand has very different characteristics to smooth childrens sand that has been acid washed, which are both very different to the smooth sand found on old sand dunes. The material is the same, but the particle size and, more importantly, the roughness of each particle, are very different. The coarse builders sand is called coarse or sharp sand for that very reason.

[JoeJablomy]

I'm not worried as much about the particles breaking as the fibers getting scored and weakened.

[Jacks Complete]

Sorry, you lost me - what fibres? There aren't any in this design. The whole thing consists of a mix of "particles and oil" contained in a bag of some form that shapes it to your body.

[deadsea]

There are fibres mentioned in the article. There's a kevelar vest that the solution is supposed to be applied to. As it is a mix of particles and a liquid i think the particles would float or sink depending on the releative densities. The vest wouldn't have to be that thick as it probaly just functions as a backing or something for the mix to adhere to. Without the vest for the solution to cling to all you would have is a big bag of oil with sand at the bottom.. Not the best candidate for armour i guess :D ..

[JoeJablomy]

No, it consists of kevlar wetted with EG or DEG containing solid particles. The STF is only going to solidify in a conical path in front of the bullet, so either you have a layer of this stuff multiple inches thick, or you have a small wad of gunk propelled into you with the bullet -unless it's contained with normal ballistic fabric, in which case it reduces the point load on the fabric and reinforces it all around the impact zone where it's stretching. Also, without the cloth, the STF would just fall into a blob at the bottom of your armor "bag" it's contained in. As I was saying, the STF replaces about half the kevlar, so the resulting armor is about as heavy but not as thick, so it's more flexible. Still no lighter to cover yourself in.
I just noticed the particles used here are pretty small -referred to as a concentrated colloidal fluid- with a 446nm average size. As to their shape, they're probably either prismatic crystals or little round blobs. My impression has always been the blobs.

"This study reports the ballistic penetration
performance of a composite material composed of woven
Kevlar® fabric impregnated with a colloidal shear
thickening fluid. The impregnated Kevlar fabric offers
equivalent low velocity ballistic performance, on an areal
density basis, to neat Kevlar fabric. Compared to neat
Kevlar fabric, however, the STF-impregnated composites
require fewer layers of Kevlar, resulting in a more flexible
and less bulky body armor material. Possible
mechanisms responsible for the enhanced ballistic
performance of the STF-Kevlar composite are identified."

"The performance enhancement
provided by the STF may be due to an increase in the yarn
pullout force upon transition of the STF to its rigid state."