University Makes Bulletproof 3D Prints

Researchers at Rice University are studying 3D printing plastic structures that mimic tubulanes — theoretical nanotube structures predicted to have extraordinary strength. The result has been very strong and very compressible structures that can actually resist bullets.

As an experiment, the researchers fired projectiles at 5.8 km/s at a block of plastic and at a block of simulated tubulanes. The structure of the tubulane block stopped the bullet at the second layer with no significant structural damage beyond the second layer. The reference block had a large hole and cracks throughout its volume.

It isn’t the strength of the material here but the topology that is interesting, because material like this should scale well if something larger or smaller is required. The latticework also makes the material very compressible as you can see in the video below.

The researchers hope to find uses for the material in fields as diverse as aerospace, automotive, sports, packaging, civil engineering, and biomedical applications. Meanwhile, you can only wonder what would happen if you could actually make the structure from carbon nanotubes.

You’d think bulletproof material is a new idea, but it turns out it isn’t at all. Kevlar — what you usually find in a  modern bulletproof vest — protects against a lot more than bullets.

68 thoughts on “University Makes Bulletproof 3D Prints

  1. “The result has been very strong and very compressible structures that can actually resist bullets.”

    @Al, bulletproof is not the same as “bullet resistant”

    1. Bullet proof is generally a marketing term that is used to describe something that is actually only bullet resistant. Calling something bullet proof is generally specious at best.

    2. One of my coworkers used to work at White Sands, and would take his lunch break and sit on big chunks of target metal on the range. He described seeing 2cm holes punched through meter thick chunks of steel, probably by rocket propelled shaped charges, and concluded there was no such thing as bulletproof.

        1. Don’t you get it? He’s saying that it’s just a matter of force. A bulet “proof” vest will only RESIST a certain amount of bullets. If the caliber goes up, the bullet(/force) resistance goes down. If the projectile changes to a more aggressive type, the resistance again goes down. Plus there are projectiles specially designed for for penetrating bullet “proof” vest, with deadly force, on the first hit

          Even armored vehicles only have a certain bullet resistance, nothing is bullet proof!

  2. A more realistic control subject would be a block of plastic that was printed out. I doubt very much that the solid plastic block is realistically representative of the plastic that was used for printing.

    1. Indeed. A solid block will just crack and “shatter” on the initial impact, while any FDM 3D print will have hollow areas and much less likely to crack like this. Compare it with a normal 3D print of the same size and weight, that would be a proper control to see if the shape makes a difference.

      1. The solution is to preemptively equip all 3D printers with 3D printed block wearing 3D printed guns, to destroy any bad 3D printed block with a gun that might be printed. That way the bad blocks would think twice before gunning their matrix, and it would be a proof the 3D printer printing process is perfect in printing good blocks with guns.

  3. Wish there were more talk about what a tubulane is instead of (or at least in addition to) the same presser everyone is posting. Material topology is definitely worth an article. As are the ludweig tubes used in this type of experiment.

    1. I can’t vouch for what Rice did, but NASA has a hypervelocity impact gun that can fire at 24,000 fps. That’s about 7.3km/s. The one at White Sands can do about 8.5km/s. They use a two-stage gas gun design.

      These are used to study what happens when a little pebble hits your spaceship. So, actually not so revolutionary.

      1. “I felt the need” to comment again, because I didn’t want you to think that my innitial, verb-lacking post, was a dig against your journalistic abilities. I don’t have access to the original article, and simply was quite impressed with the claims made. I’ll admit I did go to the linked article and cross checked the velocity claimed.
        What I wonder is if F=m*A, and I think most would agree it does (although the why behind this has me a little puzzled) what the weight of the projectile was. At hypersonic speeds I can imagine all sorts of factors that might *cushion* the impact. Perhaps even shock waves that resonate inside the tubing? Damn those paywalls!

        1. Some very quick and VERY dirty calculations:

          1.8mm aluminum projectile:

          If it happens to be shaped like a boattail bullet, probably looking on the order of 3 to 5 grains ( 1 grain = 1/7000 lb)…. That’s just comparing the grain weight of several standard lead rifle bullets to their diameter, and noting that the density of lead is 4.2x the density of aluminum

          If it was fired in one of the 7ft hypervelocity test chambers, that’s going to require between 15,000 and 20,000 pounds of force…. Or ballpark of 4,000 to 5,000 pounds for a 30ft chamber

          ….Or maybe this is one of the problems I got wrong because I couldn’t check the answer in the back of the book….

        2. >I don’t have access to the original article

          Have you heard of Sci Hub? It lets you search for articles by DOI (or URL) and obtain the full text for free. It’s an amazing resource and as an added benefit hurts large publishing houses (who inadequately compensate the researchers whose papers they sell). Really worth looking into.

          Here’s the full text for the above article:
          Wiki page for Sci Hub:

      2. I suspect it is 580 m/s or about 1900 ft/s, which is in the range of a 22 magnum rimfire. The 5.8km/s is like Mach 19. That is research gas-gun velocity and would obliterate the target. Since they are talking about bullets, the most common are the 40gr 22 (2.6 grams), 55 grain 5.56 (3.65 grams) and when concerned about personal armor, the 115gr 9mm (7.5 grams). Momentum for these at 5.8km/s is in kg-m/s 15, 21, and 43.5. That is a lot – as in a 2 pound brick going 100 miles per hour. Kinetic energy is 43, 61, and 126 kilo joules respectively. Someone dropped a digit or decimal point?

        1. A bit more: I wonder if the tiny aluminum projectile vaporized on impact. At the stated speed, a 1g bit of aluminum will have a kinetic energy of 17,000 joules. Heat of vaporization of aluminum is 293kj per mole. A mole of aluminum is 27 grams. So, a 1g projectile is 1/27 of a mole and at 5.8km/s has over 1.5 times the heat of vaporization of the projectile. It nearly all gets turned into heat on impact. Unless the target material uses a great deal of energy in deforming and breaking, vapor?

          As a repairable/replaceable meteorite shield you print in space, it is pretty interesting.

  4. for a week now I have wanted to badly to write an email to the author of that article to let her know that 20,000 feet per second for a gun is (thus far in history) impossible by a factor of roughly 3X. This demonstrates the stupidity of “journalists”. But I’m not really shocked that she’s from the UK where they have virtually no experience with firearms but love to spout shit!

    1. See my comment above. Hypervelocity impact guns are relatively common in certain fields, so I assume (but don’t know) that Rice either has one or borrowed time on the one at JSC or somewhere else.

    2. Fun fact: NASA has a light gas “gun” capable of propelling projectiles to 8.5 km/s.

      But you are absolutely correct that most “journalists” can’t operate a calculator to do basic fact checking, as most conventional small arms are sub 3000 fps.

    3. If you would read the original scientific article, you wouldn’t be so negative: “A 1.8 mm aluminum bullet was shot against the 3D printed tubulanes with a hypervelocity of 5.8 km s−1 (Mach ≈ 17) in vacuum conditions”. But yeah, it’s just easier to bash blindly at things that do not fit one’s own expectations.

        1. The full paragraph, from the paper, on this topic is as follows:

          “The hypervelocity impact tests were carried out with specially designed two-stage gas gun (LGG) at Rice University. The bullet shot through the vacuum chamber and its velocity was captured by two laser stations. The distance between the two lasers (d) was known and the bullet travel time (t) between these two lasers was accurately captured by lasers. Thus, the velocity of the bullet (v) was simply calculated based on the simple formula v=d/t. All tests were done with a 1.8 mm Al bullet with a velocity of 5.77 km s−1 and 9.8 mg weight.”

          Seems the Dunning-Kruger is strong with Chris N.

    4. You’re right to doubt journalistic fact-checking, particularly when:
      – there’s been a conversion involving a non-metric unit
      – non-journalistic units are involved (which in the U.K. are the length of a double-decker bus, the weight of an elephant, and an area the size of Wales)
      – “cancer” or “diet” is used in the headline
      – the story relates to politics

      But that doesn’t relinquish us of the responsibility of doing our own fact checking.

    5. When things don’t pass the sniff test (as here) your best bet is to then dig deeper and follow your instincts. Sometimes you find that you were correct, so you get to post smug comments. Sometimes you find that you were wrong, and you get to learn something.

      But that first step — the digging deeper — is critical.

      1. Maybe not. If people hadn’t gone off on this tangent, I would not have learned we have guns that can shoot at 8.5km/s, since I never would have gone down this rabbit hole myself.

        1. Here’s some more rabbit hole if you’re interested in the general subject: project harp, gerald bull, and project babylon. People built hypervelocity cannons big enough to put stuff into space, although not into orbit, and were working on orbital versions when the project came to a sudden halt because the designer was assassinated.

    6. In the UK, we are fully aware of the mechanics and physics of firearms. After all they have been around for 100’s of years and really are not that complex. However unlike our American cousins we are also aware of the human cost of them being used, which is why we want no truck with them.

      But as has been pointed out there are many methods of propelling a mechanism at hypersonic speeds beyond the application of Nitrocellulose or whatever, and I assume the applications they are looking at need to be tested well beyond the speed obtained from your average glock.

      However I understand your confusion. After all most of the world does not revolve about how many firearms you can own

      1. I know dozens of British people who would love to own hundreds of guns, but even if the laws were changed to allow for more freedoms… these people are too poor to even afford one. It’s a common theme. Once the empire cut back on slavery and stealing resources from colonies, profits really tanked. Luckily, their rich bring in tourist money and being part of the EU gives them power over the real EU nations like Germany. God forbid if they were stupid enough to ever leave the EU. With enough luck though, they might become relevant again, like that time before they effectively lost WWII and needed the USA to save them. Now that they’re effectively just English speaking French, it doesn’t look good though.

        FYI, most hypergun tech was developed in the USA.

      2. In the US a “silencer” for a rifle is regulated the same as a machine gun, with stringent checks, a $200 tax stamp, and a very long wait. In the EU (including England as the moment) the same “moderators” are over the counter items highly recommended (or required) for hearing protection and noise control. I know loads of folks who hunt and sheet regularly in Britain, and who have permits for rather exotic weapons as well.

        Anyway, I wonder if the tiny aluminum projectile vaporized on impact. At the stated speed, a 1g bit of aluminum will have a kinetic energy of 17,000 joules. Heat of vaporization of aluminum is 293kj per mole. A mole of aluminum is 27 grams. So, a 1g projectile is 1/27 of a mole and at 5.8km/s has over 1.5 times the heat of vaporization of the projectile. It nearly all gets turned into heat on impact. Unless the target material uses a great deal of energy in deforming and breaking, vapor?

    1. Also, will it resist slower, heavier projectiles like 9mm JHP or FMJ round nose? What filament type was used? If they used PLA or ABS and it resists common pistol bullets, and the STL can be copied and pasted to make large panels, hello cheap-ish and relatively lightweight vehicle armor.

      1. The yellow print isn’t PLA, as they compress it. And PLA doesn’t do that, it would explode if you do that.

        However, the gray print shown at the top photo, how those layers look and break, that looks a lot more like PLA.

        But it is all guessing work without access to the actual paper. Which is pay-walled, to ensure we cannot point out the flaws in it and invalidate it.

      2. “hello cheap-ish and relatively lightweight vehicle armor.”

        Yeah, that’s what I was thinking too!
        Now, can it be made light enough as well to allow the vehicle to float if 007’s Aston-Martin is forced off a dock or bridge?

    2. And if they aren’t to be had (and fair enough, they probably want to reap the rewards of this research) then who wants to help independently develop something similar?? I bet we can do it. Maybe we can crack some hydrogen and build a light gas gun to test it too.

  5. So would these ultra hard polymers be good for shielding spacecraft from nano meteorites, or would it just result in additional space debris. And if it does result is additional debris, will the debris be low velocity.

  6. You folks are just too lazy to follow two links on Wikipedia and keep your attention span in that time?

    (Folks, sorry to be so harsh, but hey…)

    Elsewhere on the comments there was already a link to the Hypervelocity Wikipedia page [1]. From there, there’s a link to the Light-gas gun [2] Wikipedia page with some pics of those guns used to achieve those velocities (and diagrams, and explanations, and all that).

    One of the pictured guns sits at… yes, Rice University! (now: attention span… yes, that’s the Rice University where those prints have been made).



    1. I don’t think they’re really trying to imply it’s for that kind of bullet, except perhaps as a figure of speech. It’s a hypervelocity projectile. They use them to test all sorts of new materials in novel physical extremes. Does the term bullet actually restrict it to a chemical cartridge like in most traditional small arms?

      Also geez, gun people are just always champing at the bit to pick apart gun stuff online. It’s always the main subject of discussion when it comes up.

  7. This is the sort of material that the tiles on the space shuttle should be made of. Imagine if Columbia could have printed a replacement tile for the one damaged on its wing. They cant carry spares to each panel, but they can store the shape, and print on demand. Granted they’d have to be using a material other than plastic to resist the heat of re-entry, but i’m sure theres some sort of printable ceramic composite available.

    1. That’s what I was thinking. But there are a lot of follow up questions too. Does the structure need to have a specific hole/ wall thickness ratio and can the strength be improved with filament containing kevlar? Does the structure need to be a rigid Z/Y/X or can the tubes contour to the panel shape? Can it resist a 30-06? 5.56? 9mm? If so, at what thicknesses?

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