Silly Putty as body armor

[Belrix]

Silly putty is wierd stuff. Push slowly and it deforms, whack it with a hammer and it shatters.

There's probably a good technical term for this but in general, it's fun, wierd, stuff.

A cop friend has a body armor vest with steel plates in it, it's bulky and doesn't move well. (They make him buy it himself, too - it's not issued. Cheap bastards!) I was thinking that there should be some cool silly-putty-like material that a vest could be made with- under normal movement it should flex and move but hit quickly it should be stiff.

Anything out there like this?

[Squink]

You bet there's stuff like that out there!

Liquid Armor (http://www.sciencentral.com/articles/view.php3?type=article&article_id=218392807) The liquid - called shear thickening fluid is actually a mixture of hard nanoparticles and nonevaporating liquid. It flows normally under low-energy conditions, but when agitated or hit with an impact it stiffens and behaves like a solid. This temporary stiffening occurs less than a millisecond after impact, and is caused by the nanoparticles forming tiny clusters inside the fluid. "The particles jam up forming a log jam structure that prevents things from penetrating through them,"

Video: Liquid armor (http://video.google.com/videoplay?docid=5469322483836077126&q=liquid+armor)

[Q.E.D.]

There's probably a good technical term for this..
Viscoelastic.
Anything out there like this?
Yep (http://www.freepatentsonline.com/5738925.html). I don't know if it's of practical use yet.

[CynicalGabe]

There's probably a good technical term for this but in general, it's fun, wierd, stuff.



Viscoelastic
Actually, I think Non-Newtonian fluid (http://en.wikipedia.org/wiki/Non-Newtonian_fluid) is a better descriptor.

[CalMeacham]

Thixotropy is the term you're looking for.

[Q.E.D.]

Thixotropy is the term you're looking for.
That's the opposite of what Silly Putty does, though. A thixotropic material is stiff when let to stand, but thins out when agitated or stirred. Silly putty is semi-solid, normally, but gets stiffer when struck.
Actually, I think Non-Newtonian fluid is a better descriptor.
Non-Newtonian fluid describes a wide range of materials with properties ranging from viscoelastic to thixotropic.

[CalMeacham]

That's the opposite of what Silly Putty does, though. A thixotropic material is stiff when let to stand, but thins out when agitated or stirred. Silly putty is semi-solid, normally, but gets stiffer when struck.


Not true. Silly putty is stiff when it stands -- it flows slowly with time to fill that egg container, but it's a slow flow. When worked slowly silly putty thins out (it's only when struck rapidly that it shatters). A lot of paints are thixotropic -- they spread when you work them slowly with a brush, but gel when standing. The refeerences in Jearl Walker's Flying Circyus of Physics call Silly Putty thixotropic.

[galt]

It's a Dilatant (http://en.wikipedia.org/wiki/Dilatant) material.

[WhyNot]

It's a practical application for oobleck! (http://sciconn.mcb.arizona.edu/oobleck/oobleck.html)

[Q.E.D.]

It's a Dilatant (http://en.wikipedia.org/wiki/Dilatant) material.
Well, if Cal is right about the material thinning out when worked slowly, and I've no reason to doubt that he is, then that's not quite right, either. It seems to have properties of several different classes of materials, and not really belonging to any one of them. In that case, Gabe's "Non-Newtonian fluid" is probably about the most accurate classification, after all.

[CalMeacham]

In that case, Gabe's "Non-Newtonian fluid" is probably about the most accurate classification, after all.

Could be. Silly Putty is weird stuff, any way you look at it.

I'm so dense that it was years before I realized that "Silly" Putty was probably inspired by "sili-"cone putty.

[galt]

I'm not sure it's correct to say it "thins out" when worked slowly. It flows/deforms slowly, like an extremely thick liquid. If you attempt to deform it too quickly, it breaks sharply. I have a hunk of it right here if you want me to perform any experiments. :D

[Belrix]

Could be. Silly Putty is weird stuff, any way you look at it.

I'm so dense that it was years before I realized that "Silly" Putty was probably inspired by "sili-"cone putty.
:smack:

...and I never made the connection until right now! (not that I really made a connection as had it made for me.)

[chorpler]

Wow, more Larry Niven stuff come to life. This sounds exactly like the "impact armor" he had Louis Wu wearing in the Ringworld sequels -- ordinarily it was pretty soft and flexible, but if something like a bullet hit it, it would go instantly rigid and protect the user.

[BMalion]

so it's a Viscoelastic, non-newtonian, thixotropic, dilatantic, oobleckian substance, right?

[Raguleader]

What properties does it possessed when placed on a treadmill?

*ducks and flees*

But seriously, does anybody have a sizable quantity of silly putty and a gun that we could use for experimenting? Even if it doesn't work, it should be entertaining.

[HeyHomie]

But seriously, does anybody have a sizable quantity of silly putty and a gun that we could use for experimenting? Even if it doesn't work, it should be entertaining.

E-mail Mythbusters. Now.







Now!!!

[Antigen]

so it's a Viscoelastic, non-newtonian, thixotropic, dilatantic, oobleckian substance, right?

No, it's a soquid.

[Princhester]

E-mail Mythbusters. Now.

My thought exactly. Q.E.D., paging Q.E.D!

[MaryEFoo]

Squink's cite:
"but when agitated or hit with an impact it stiffens and behaves like a solid. This temporary stiffening occurs less than a millisecond after impact, "

How far does a pistol bullet travel in a millisecond?

[Suburban Plankton]

How far does a pistol bullet travel in a millisecond?
It depends on the gun, but 1000 feet per second is a good number to start with. Given that speed, we're looking at one foot in a millisecond.

That's gonna take a lot of silly putty.

[Squink]

we're looking at one foot in a millisecond.
That's gonna take a lot of silly putty.The stiffening occurs by a physical jamming mechanism which depends on deformation of the material. The faster the deformation, the faster the material stiffens. Still, the guy in the link probably should have said microseconds. If you examine the video, it looks like the stuff flexes an inch or two before the bullet bounces off. Using 1000fps, 2 inches would represent about 160 microseconds.
Two inches could still hurt a lot, say on a bone, but it's impossible to tell from the video how the back of the material is supported, and that's important in getting more than a rough guess of the timeframe involved, as well as in evaluating whether the stuff would provide effective armor to a human.

[commasense]

If you want to play around with a viscoelastic material and don't have a kilo of Silly Putty lying around, check in the kitchen for a box of cornstarch. As we learn from those two noted scientists, Penn & Teller, in their journal Penn and Teller's How to Play With Your Food )1992), if you add a cup and a half of water to a box of cornstarch, the mixture is viscoelastic.

It appears to be a thick liquid, and you can easily move your fingers through it slowly. But if you smack or punch it suddenly, it becomes rigid. Hit it hard enough and you can even get it to form cracks. P&T suggest taking a glob and patting it into a ball, then tossing it to an unsuspecting friend. It'll pass through his fingers.

A quote from the book explaining the science behind it: "The cornstarch forms really long-chain molecules. When the gunk is diluted or deformed gently and slowly, these honking chains can rearrange themselves and stay liquid. But, when there's enough of these molecules crammed together and the impact is fast and hard enough, they don't have the time or room to rearrange their big old selves. They stay all tangled, and the viscosity becomes enormous. With violence all around it, the slime cops to a solid."

After buying the book I got some cornstarch and spent a couple of hours playing with the stuff. It's very entertaining. (I stopped short of shooting it with a pistol.)

[gazpacho]

It depends on the gun, but 1000 feet per second is a good number to start with. Given that speed, we're looking at one foot in a millisecond.

That's gonna take a lot of silly putty.
http://www.crayolastore.com/product_detail.asp?T1=CRA+08-0001-0-001&.
5 pounds for $80. I think I saw it cheaper in bigger quantities elsewhere before but I cannot find it now.

[gazpacho]

This is a video of throwing 50 pounds of silly putty off a building. Dow Corning 3179 Dilatant Compound is reported to be silly putty.

http://www.fugly.com/videos/5586/50-lbs-of-dow-corning-dilatant-compound-3179-coral-putty.html

[CynicalGabe]

If I were a scientist, and I'd gone through 3178 compounds to invent silly putty... I think I'd have to kill myself.

[Sublight]

Crazy Aaron's Thinking Putty (http://www.puttyworld.com/index.html) 5 pounds for $100-$140, depending on type.

If you go to their "tricks" page, they have several videos of people shooting huge wads of putty from a potato cannon. If you do a bullet-proofing experiment, be sure to send them a copy of the footage.

[Waverly]

Viscoelastic. Actually, I think Non-Newtonian fluid (http://en.wikipedia.org/wiki/Non-Newtonian_fluid) is a better descriptor. Thixotropy is the term you're looking for.Christ. Google hounds: the net is a wonderful place, but it is full of incorrect information. Sometimes (gasp!) you need to know what you are doing. I know, I know, wouldn’t it be wonderful if google could make everyone an authority?!

I don’t care what wiki says. Viscoelastic is general term for materials with viscous and elastic properties. The stress/shear curve could be doing any number of things. Non-newtonian is also a generic term for a non-linear response to shear. Thixotropic is dead wrong. This is shear thinning.

Dilatant is shear thickening. Low and behold, if you use a non-google patent miner, you would find several patents and applications for armor using dilatant materials. It’s not a new idea, but I don’t think any practical applications exist yet.

[HeyHomie]

E-mail Mythbusters. Now.


I went to the Discovery Channel website and didn't see a way to contact Adam & Jamie directly. However, I did post the following message on the Mythbusters message board.


On another message board, there is a thread discussing whether or not Silly Putty can stop a bullett.

This would be a perfect myth for Adam & Jamie to try to bust.

How does someone suggest a myth directly to them (or to the producers)?

[commasense]

I went to the Discovery Channel website and didn't see a way to contact Adam & Jamie directly. However, I did post the following message on the Mythbusters message board.Well, being as Q.E.D. has contributed to this thread, I think we have an inside track to the producers.

If I can add my own two cents to the idea, although the people who made the video that gazpacho linked to obviously went to some trouble, it leaves a lot to be desired: no close-ups, no ultra slo-mo. A few serious experiments by the Mythbusters with the stuff, dropping it from great heights, testing its properties, concluding with shooting at it with a gun, could make a couple of very good (and not too expensive) segments for the show.

Whaddya say, Q? Will you pass it along for us?

[Waverly]

However, I did post the following message on the Mythbusters message board.No, silly putty cannot stop a bullet. The problem with the silly putty armor approach is that after a certain point, the projectile is going to interact with the dilatant material as if it were a brittle solid. The shear rate will exceed the rate at which the polymer chains can slide paste one another, and the material cracks or shatters. The material isn't even necessarily that tough at these high shears.

The patents typically involve a composite approach. Picture a pillowcase made out of Kevlar, with the pillow made of silly putty. Now you have the beginnings of a solution. The putty will absorb some kinetic energy before brittle failure, and then you rely upon the kevlar penetration barrier. I still think this approach is limited.

Better would be a multilayer sandwich structure, with alternating layers of penetration barriers (Kelvar) and/or impact resistors (epoxy coated carbon fiber) and kinetic energy dissipators (in our example, silly putty).

Most practical would be composite honeycomb structures filled with silly putty, faced with Kevlar or carbon composite, and stacked in multiple plies. It would not be too great an engineering problem to squeegee silly putty into open cells before laminating on the cap face. I didn't find a patent for this approach, but I wouldn't be surprised to learn that there were applications under review.

[CynicalGabe]

Christ. Google hounds: the net is a wonderful place, but it is full of incorrect information. Sometimes (gasp!) you need to know what you are doing. I know, I know, wouldn’t it be wonderful if google could make everyone an authority?!


My apologies, Master. We bow before your superior wisdom.

[Waverly]

I think you should reserve the Master talk for Cecil, or your favorite dominatrix.

I don’t have an objection to google-assisted wags and the like as long as it’s clear that is what they are. The best forum for getting a factual response to a unique question doesn’t work so well otherwise.

[Terminus Est]

What properties does it possessed when placed on a treadmill?

It would become endochronic (http://en.wikipedia.org/wiki/The_Endochronic_Properties_of_Resublimated_Thiotimoline).

[HeyHomie]

Well, being as Q.E.D. has contributed to this thread, I think we have an inside track to the producers.


How so? Does he work for The Discovery Channel or something?

[chorpler]

How so? Does he work for The Discovery Channel or something?

Q.E.D. was recently hired as a writer or researcher or something for the Mythbusters show. Way awesome.

I'd search for the thread where he announced it, but I gotta run.

[galt]

I don’t care what wiki says. Viscoelastic is general term for materials with viscous and elastic properties. The stress/shear curve could be doing any number of things. Non-newtonian is also a generic term for a non-linear response to shear. Thixotropic is dead wrong. This is shear thinning.

Dilatant is shear thickening. Low and behold, if you use a non-google patent miner, you would find several patents and applications for armor using dilatant materials. It’s not a new idea, but I don’t think any practical applications exist yet.You're a little unclear: are you saying that dilatant is the correct term?

I, personally, was not going on a google search when I suggested that term. I was going on the fact that I have participated in an order of 100 lbs of "coral-colored dilatant compound 3179" from Dow Corning, which lends some (but not total) credence to the idea that "dilatant" is the proper term.

For what it's worth, the Crazy Aaron's Thinking Putty FAQ doesn't mention compound 3179 but it does tell the familiar story of the origin of a "Bouncing Putty" at Dow Corning and says that this putty is the primary ingredient in Thinking Putty.

[Cagey Drifter]

did I read something about using spiderwebs for this? or am I dreaming?

[Waverly]

You're a little unclear: are you saying that dilatant is the correct term?Yeah, you have it right.

[First Amongst Daves]

did I read something about using spiderwebs for this? or am I dreaming?

Catching fighter jets on aircraft carriers?

[Belrix]

Since the thread was bumped...

I can't help thinking that this topic is a little out of Mythbuster's scope. While interesting & fun science, it's there's no myth to be busted on this.

-B

[anamnesis]

did I read something about using spiderwebs for this? or am I dreaming?There's always been pseudo-scientific speculation into applying the structural properties of spider silk to the creation of materials with high tensile strength, but I think it's mostly reserved for comic strips (Spiderman) and sci-fi fantasy tech. I think I recall something called "carbon-fiber arachno-weave" which was used to make strong but incredibly light armor in some fictional SF universe ... an anime freak friend of mine told me about it. Honest. :)

Regarding the dilatant body armor/Mythbusters discussion, I know there was there an episode dedicated to the history and future of body armor on one of the edutainment networks recently ... A&E, History Channel, Discovery ... ? I don't know if it was Modern Marvels, or Battle Gear, or Mail Call ... each network has their own little weapons technology shows and they all sort of blend together in my mind, but they discussed the topic of dilatant kevlar materials which were lightweight and flexible, but which could absorb and/or deflect high-speed projectiles. Quite similar to what was shown in that Google Video that Squink posted a few days ago ...

[Chronos]

did I read something about using spiderwebs for this? or am I dreaming?Spiderwebs are one of the strongest and toughest fibers known, so it wouldn't surprise me if someone had considered making some sort of armor out of them. However, they're very difficult to synthesize or cultivate in sufficient quantities, and I think in the past few years they've developed synthetic nanofiber composites which are even stronger and tougher.

[Squink]

Spiderwebs are one of the strongest and toughest fibers known But they're pretty stretchy (http://www.tiem.utk.edu/~mbeals/spider.html), which isn't normally something you'd want in body armor. Who cares if it stops a bullet after it travels 12 inches beyond the point of impact?

[Richard Pearse]

I saw a guy on TV recently who had invented a beenie for skiers and snowboarders that had a layer of silly putty type material in it. The idea being that when their head hits something hard and unforgiving the beenie will take the impact. But it doesn't look like you're wearing a helmet, so you don't lose the cool factor of skiing.