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Shear Thickening Fluid Armour - Poject Idea

  1. Feb 6, 2008 #1
    Im currently doing an HND in chemical engineering and everyone in my class has to do a project of their own choice.
    Iv been doing a bit of reading on shear thickening fluids and their application to kevlar to increase its strength against ballistics.
    The STF is made up of silica particles (400-500nm) mixed with ethylene glycol, which is then diluted with ethanol for easier absorbtion into the kevlar.
    I was thinking of either doing stab tests or i have a shotgun which i could use (would have to do that at home, obviously)
    Im just trying to think what my variables would be in the experiment.
    What i had in mind was testing different layers & combinations.
    (1) kevlar layer
    (2) kevlar with absorbed STF
    (3) 2x kevlar layer + STF layer
    (4) STF layer + 2x kevlar layer
    (5) 5ml STF in 4 layers kevlar
    (6) 10ml STF in 4 layers kevlar
    (7) 15ml.......

    you get the idea

    I would have the layers fixed to a clay background, so i can measure the depth of the penetration which would reflect the how well the energy is dissipated.
    If the shotgun is too powerful, i could have an aluminium sheet in front to take some of the impact.

    The only problem with a shotgun is the pellet spread, it will be different from shot to shot. Not sure if that really matters though, i could just measure the deepest dent in the clay.

    So what do you folks think? Does it sound feesable or too far fetched?

    Im hoping to go to uni after college so i want to stand out in my class with a great project.

    Thanks for reading
    Last edited: Feb 6, 2008
  2. jcsd
  3. Feb 6, 2008 #2


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    This is precisely what Norman Wagner has patented (applied for). In his patent application he uses a 22 caliber 17 grain chisel pointed cylindrical projectile (NATO standard) aimed at a target as you have described. He even uses a clay witness behind the target to evaluate effectiveness of penetration. His gun is a helium gas type that accelerates the projectile to a speed of approximately 800 fps which he measures with a chronograph. To get the same penetration with a much larger projectile such as a shotgun slug, you would have to increase the velocity considerably. I wouldn't try the multipellet shell since you couldn't accurately measure the velocity and you wouldn't always have every pellet on target.

    If you have all that stuff, you are in a position to confirm (or refute) his results. That said, ballistics research is pretty difficult to do well. Good luck with it.
  4. Feb 6, 2008 #3


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    You probably don't want to use a shotgun for the tests, it's ballistic properties just aren't comparable to a handgun or rifle round.

    I would instead choose one or two guns that are popular in a wide variety of civilian and military applications, such as a .40 S&W handgun, a .45ACP handgun, a 9mm para handgun, or possibly for a rifle round a 5.56mm NATO (very similar to the .223 remington) round. These are all rounds that could be seen as candidates to be stopped by kevlar body armor, the rounds are available at most gun ranges, and weapons that shoot them are usually available as rentals. If you REALLY want brownie points, you might consider testing your prototype body armor against specifically military guns, such as an AK-47, which uses a 7.62x39mm round. Depending on the area, some large gun stores with ranges might have rental an AK-47's or AR-15's (civilian semi-auto version of the US military M-16, usually chambered for a .223 remington round).

    For the greatest weapon availability, I would be inclined to get in contact with either a gun shop or a shooting club, and ask about the possibility of having an owner of a gun you are interested in (or perhaps multiple people with several different kinds of firearms) shoot at your pre-made targets for you at a set distance at a firing range. I imagine that a gun/shooting club would be intrigued by your project, and would gladly volunteer their time and firearms if you bought the ammo (they might even spring for the ammo too). If worse comes to worse, rent a few guns at a local gun range and shoot them yourself.
    Last edited: Feb 6, 2008
  5. Feb 6, 2008 #4
    Unfortunately the UK is tight arsed when it comes to guns, so i doubt i would be able to get my hands on anything like that.

    Maybe i could change the aim of the project to see what the minimum thickness of STF treated material is required to stop the penatration from a shotgun.
    Or i could maybe test out different STF mixtures? Im sure iv read about using clay particles also in STF's.
    If you have any suggestions i would love to hear them, but most likely i could only carry out tests with 12 gauge pellet cartriges.
    Its also extremely difficult to get slug cartriges in the UK, very tight regulations, damm country!
  6. Feb 6, 2008 #5


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    Hmm, that does make things a might bit more difficult... I kind of sound like a wild gun-slinging American huh?

    Maybe talk to the police dept. to see if they would be willing to shoot up a few targets for you? You don't have to do the shooting, you just need to find someone that can. If you're inquisitive but not pushy, and are upfront in saying you're trying to develop an advaced material for next-generation body armor, you might be able to get somewhere. I just think your tests will have a lot more credibility if you test your material against a round a bullet-proof vest might actually come in contact with...

    But if bird shot ends up being all you have access to no matter what, seeing what thickness STF material stops a shotgun blast at close range versus standard Kevlar could be the next best thing. I suspect a much thinner amount of STF would stop a shotgun blast when compared to what would be required for say a .45acp round or .40S&W.

    Are you able to find .22LR rifles or handguns? Those might suffice for small-scale experiments.
    Last edited: Feb 6, 2008
  7. Feb 6, 2008 #6


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    I would recommend just placing the gun at a distance which minimizes the shot spread. You should be able to keep it down to an inch or so at a reasonable range. Of course, that mainly depends upon what sort of choke you have.
  8. Feb 7, 2008 #7
    Mech Engineer: I'v found the website of a local rifle range so i might take a drive and check it out.


    Not sure if my local police station would have facilities to fire any weapons since they dont even carry guns. How boring!

    Danger: My dad reckons the same, he has different chokes that can be used. Just hope i dont get lead shot coming back in my face at close range :P

    Firstly i better make sure my teacher is happy with this project, he did sound interested when i mentioned it.
  9. Feb 7, 2008 #8


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    As with any experimentation involving weapons, I would recommend clamping the gun into a padded vise with a nice long string tied to the trigger.
    The shooting range is a better choice, though, if they're willing to help you. For one thing, you'll have a wide variety of ammunition available.
  10. Feb 7, 2008 #9


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    Now you're on to something!
  11. Feb 7, 2008 #10
    I'll e-mail the club once my teacher gives the go ahead.

    Few question about this experiment though:

    How strong actually is this stuff? I mean i dont want to turn up and have bullets go through my targest and have to go away and increase thickness and STF amount etc.

    How should i make these targets? I can just imagine bullets pushing my kevlar targets through the clay. should i have a thick steel or wooden block behind the clay?

    Do you think i should just test each target once? I mean, if i shot multiple identical targets, should i get penatration depths that are reasonabnly close? Not sure if the bullet velocity will vary from round to round. Testing each target a few times would take ages, since i would have to remould and flatten the clay for the next shot.

    If you can think of any other problems i may encounter then let me know.
  12. Feb 7, 2008 #11


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    Don't ever shoot twice at the same area, since the impact damages the fibres. (You can, of course, do that in order to determine the effects of the subsequent shots, but not as a standard test of the material itself.)
    Whatever they use at the rifle range will be more than adequate for your backstop. If you're going to do it on your own, I'd try to locate a bunch of railway ties and stack them up at least 2 deep (depending upon calibre). The best thing would be a nice dirt embankment if you have access to something like a ditch or quarry.
    Even with a good stopper, make sure that there's nothing within a couple of miles downrange in case you happen to miss it completely. That can happen from an equipment malfunction no matter how good a shot you are.
  13. Feb 7, 2008 #12


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    Not sure if this site can be of any use to you, but i have gotten some pretty heavy thread from them.
    I also wonder if you might weave some of your own target patches, and what size thread you are using in the material you currently have?
    Give Wes a call if you have questions, he has been friendly with me, and given some good information.


  14. Apr 10, 2009 #13
    What dose the chemicials consist of?? What type of silica is used?? Have you got the project to work??
  15. May 8, 2009 #14
    Did you ever figureout how to make Shear Thickening Fluid???
  16. Dec 4, 2009 #15
    I have done a fair amount of research on shear-thickening fluids, and have found the best chemicals to use are polyethylene glycol and silica. Dilute the mixture in ethanol and soak the Kevlar fabric. Once soaked, dry the Kevlar in a drying oven to evaporate the ethanol, and you will be left with treated Kevlar. If you do use the shotgun, I would recommend testing from a close range (3 meters maximum from muzzle to target), but I do not recommend being close to the shotgun when fired. A vice would be a good idea with a string trigger-pulling system set up so that you could stand to the side or behind an approx. 1cm-thick piece of plywood.

    The close range will transfer maximum energy into a small area, but the small size of shotgun pellets will encourage bounces. You should begin with using a separate test piece with each individual shot. "Danger" is correct.

    As for the clay backing, I would use a 10cmx10cmx30-40cm block of clay, with the Kevlar on the small 10x10 face. A well-mounted wooden backing for support may help. Metal would be more difficult to work with, and unnecessarily strong. Best of luck, and I will do my best to answer any other questions you may have.
  17. Dec 20, 2009 #16
    Thanks for the input Smith and everyoe else.
    Unfortunately I never got the go-adead for this project as my tutor thought it would be too difficult and time consuming, plus they were meant to observe my work in college. I ended up doing HPLC analysis on various different types of chocolate (for theobromine and caffeine concentrations).
    That was about a year and a half ago, now im half way through the 3rd year of the degree, woop!
    I might still give this a go in the summer when i'm off, just for fun :biggrin:
  18. Jul 10, 2011 #17
    How much Ethanol did you use too how much STF ?

    How Pure does the Ethanol have too be?
  19. Jul 10, 2011 #18

    I've been waiting on some new responses from this topic for a while. Question? From the sound of it you must have your STF down pack? As for your question I think you need somewhere 90-100% pure Ethanol. I've been looking for the right Silica on my need. Wondering do I need to use nano or micro silica around 300nm -500nm? I have the PEG Polyethylene Glycol 200mw. This would be a good project if I had the right stuff. I would find a way to make this even better. Good luck!
  20. Jul 10, 2011 #19
  21. Jul 10, 2011 #20
    That stuff on ebay may just be Corn Starch my friend. It's too powdery looking for one. Also the fact that it uses water. As for the 95 % rubbing alcohol the same as Ethanol? No I don't think it is the same but another form of alcohol. I think the drinking type is close enough. This might help friend. http://en.wikipedia.org/wiki/Ethanol
  22. Jul 10, 2011 #21
    "absolute alcohol" should work then, Its 95 per cent Ethanol.I dont think i can find that kinda thing in the canadian Liquer stores.

    I heard i can find Ethanol in hardware stores.
    I asked the Ebay Seller about the STF ingredients and waiting for reply.

    I only found out about the potential for powerful STF's yesterday.
    Expect allot more people too gain interest and search for this very Thread too learn what we have learned so far.

    Im looking into Ethanol Fueled Fireplaces and checking how pure the fuel is, maybe that will work
  23. Jul 10, 2011 #22
    I've been doing my research for about a year. I cam across a video on youtube showing STF. Cool stuff but a pain to do yourself if your not a chemist or really good in science. Though I'm not a chemist I can follow directions well. The key to this project is to have the right Silica and liquids. The Cornstarch STF is easy to make though it dose spoil so it's not a good long lasting result. Let me know how it all goes and be careful. Do your research also.
  24. Jul 11, 2011 #23
    I need a Permit too get Ethanol where i am from... However Denatured Alcohol should work, its 90 percent Ethanol right?

    I have not been told the STF ingredients yet and I will let you know if its Nano Silica or Cornmeal as soon as the seller responds.

    I hope some one responds with the correct Ethanol to STF ratio or i may have too take random guess's. I dont know how much i must dilute the Sheer Fluid before i soak the kevlar..
  25. Jul 11, 2011 #24
    Did you look over the Wiki link I sent you? You can get all the info you need on Ethanol. Also be careful as that stuff is flammable. Yes keep me posted.
  26. Jul 12, 2011 #25
    http://www.che.udel.edu/research_groups/wagner/website/awards_files/ADVANCED%20BODY%20ARMOR%20UTILIZING%20SHEAR%20THICKENING%20FLUIDS-Army%20conference%202002.pdf [Broken]

    I found a Recipe Book! :surprised

    I got the ethanol ratio Finnaly. Im a bit worried about the thickening fluid now, i think it has too be nano and i dont think there is nano particles on Ebay. I have yet too get a Conformation from the STF seller.
    Last edited by a moderator: May 5, 2017
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