Metal foam obliterates bullets
phys.org
phys.org
The armour is a composite sandwich, with boron carbide on the front face (a hard ceramic), followed by the metal foam, and either aluminium or kevlar on the rear face.
The boron carbide layer blunts the bullet and distributes the compressive stress over a large area of the metal foam. The metal foam is made of 2mm-diameter hollow steel spheres in a stainless steel matrix (created using powder metallurgy). The metal foam deforms plastically under the compressive stress, absorbing the kinetic energy of the projectile (i.e. the spheres get crushed). The backplate provides tensile strength and stops the foam from tearing apart due to residual tensile stresses.
It's not like you want it to save your life more than once...
[1] <https://www.quora.com/Why-was-Dragon-Skin-armor-rejected-by-...
That said, the design is obviously way too heavy without anyone even needing to weigh it.
> Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball bearing)
I'm hoping they carried out their experiments (physical and simulation; in my book, FEA simulation results aren't "analytical") more carefully than they wrote the paper.
The foam does sound like a pretty interesting material! I've read about metal foams since my childhood, but the hollow-sphere-based foam seems significantly stronger than the more irregular foams.
* I'll give you "advance".
* I guess you dislike the lack of hyphen in "high performance"? But then you dislike the hyphen in "light-weight"? But no comment about "high impact"?
* The "its" is actually "correct" (standard) usage.
* No article on "powder metallurgy technique"? Okay, sure, but this is an incredibly common mistake, especially for non-native English speakers.
* I would think simulation results are "analytical" by virtue of not being physical. Seems fine to me.
Most people are only native speakers of one language. The amount of effort required to iron out these extremely minor "problems" (if you accept your English teacher's notion that there really is a right or wrong way of using English) in a second language is simply not worth it for most people. They still got their message across, don't they? Their research is still understood and made use of, isn't it? So why not let it slide?
Yes, these things can grate on my nerves, too. But were I writing formal papers in languages that aren't native to me I would only hope to do as well as these authors appear to have done.
The issue with "its" is that it's singular, but its antecedent (or postcedent, if you will) is "composite foams", which is plural, and used with the plural form of "have". So "its" here violates pronoun-antecedent agreement.
The problem with violating grammatical rules (whether they're the rules of academic English or of AAVE) is not that it's morally wrong; it's that it makes you hard to understand. In fact there are people who would have understood and made use of their research who will not do so. If the errors were more serious, the number of people thus excluded would be larger, but it's still nonzero. Some of those people will simply remain ignorant of the results these researchers attempted to publish; others will get them from another source, perhaps an experiment done by someone who was ignorant of the results, assuming that the results are correct. Perhaps metal-foam composites research will lag behind where it would have been with a more coherent paper, and alternative forms of armor (aerogels, say) will become dominant instead, and the researchers and their research will languish in obscurity.
Another part of the problem is that the sloppy abstract signals to readers that the researchers had very low standards for the paper—perhaps if I attempt to reproduce their results, I will discover that they misstated the composition of their strike plate, omitted crucial details like the density of the spheres or which stainless steel they used for the matrix and how they sintered it, or even incorrectly measured the deformation of the backplate.
If you're writing formal papers in languages that aren't native to you, you should find a native speaker to write or at least proofread your abstract, if not the entire paper. Some people do this professionally at a cost substantially lower than the cost of fabricating a stainless-steel foam, so even if you're living in Bhutan, you can contract a professional writer. But the authors of this paper are at NCSU, which has 34000 students, over 29000 from the US, so presumably they have at least 25000 functionally-literate native English speakers in their very own university, most of whom would be willing to work for well below market rate and many of whom are actually interested in learning to Do Science.
But they didn't care about communicating their results.
Our funding was a mixture of European Space Agency and a car conglomerate: light armour for space vehicles and crumple zones / reinforcement respectively (less acceptable to research military applications in EU in my experience).
You are technically correct, though based on common usage patio11 got their point across.
"Let me start by saying that it is not a crazy idea and is actually what I have been working on recently. I even have a proposal in DARPA on testing the performance of the material at supersonic speeds. At this time, our data covers up to a speed close to 1Km/s as you mentioned. We have not tested the performance at higher speed and that is what I was hoping to conduct soon."
(I asked if it could be used for space debris at 8-15km/s, and apologized for asking a crazy question)
Not for all types of radiation. Neutron radiation for example is absorbed better by a hydrogen rich material like say polyethylene. But then during absorbtion it would emit gamma rays sometimes, so metal shielding is needed as well.
The composite metal foam that was comparable to lead utilized steel with higher concentrations of tungsten and vanadium.
> The metal foam is made of 2mm-diameter hollow steel spheres in a stainless steel matrix (created using powder metallurgy).
Designers of spacecraft and lunar/Mars bases are likely pretty happy about this development.
Unfortunately I could only find the paywalled version here: http://www.sciencedirect.com/science/article/pii/S0969806X15...
http://www.digitalprognosis.com/album/images/iraqpics/the-st...
The slats are smaller than the height of the outer explosive and prematurely detonate it. As a result, the penetrator simply bounces off the armor harmlessly.
If the explosively formed jet forms more than a few inches from the armor, it's way less effective.
The "cage" slats can be effective against both.
http://www.cbsnews.com/news/us-sees-new-weapon-in-iraq-irani...
So, three projectiles in the same spot?
It was probably made the NIJ standard because it's the only somewhat common AP ammo a US cop is likely to go against on the street, as noted by extrapickles the serious AP ammo is a lot more expensive, and I'll add not really legal any more since there are some pistols that'll fire it.
Notably, ESAPI military equivalent plates also aren't certified to stop anything more serious than AP M2, and I assume again for the same reason, there is or was a lot of surplus AP M2 ammo out there at one time. In the US civilian marketplace it's pretty much dried up as I understand it, e.g. see the few hits this GunBroker.com search finds and the prices: http://www.gunbroker.com/Ammunition/BI.aspx?Keywords=ap+m2 and I can't find any demilled bullets there or with a couple of minutes of Google time, whereas they were commonly available not too many years ago, certainly within the last decade.
Even if I'm wrong, unless it catches somebody in the eye, I don't think those little fragments could do worse than a flesh wound.
How could this be extraordinarily effective at stopping bullets but not meaningfully improve survival? Fairly few American soldiers are killed by gunfire which directly strikes them; even fewer of these soldiers are killed by gunfire which directly strikes them on their armor. (This is partly because armor is fairly effective, partly because bullets are often non-fatal, and partly because medical care is very good.) Improved body armor may not meaningfully improve survival against other threats such as, for example, IEDs (once 60%+ of fatalities, down these days) or "the helicopter impacted terrain at a high rate of speed."
Something like this would be a great improvement over the very heavy homebrew plating that our guys in Iraq and Afghanistan were forced to improvise on their Humvees? I.e. before MRAP type vehicles made it into the field.
Lighter and better armor isn't just for people, it's also for vehicles.
http://www.ammochannel.com/30-06-30-cal-m2-ap-armor-piercing...
To hit someone in the eye, you've got to aim at their eye and land a round there. That is, accuracy at hitting a pre-specified target.
To hit armour in the same location twice, you need either two (or more rounds) delivered consistently on whatever happens to be where the first round lands. It's a case where being a Texas Sharpshooter actually works (painting bullseyes around the bullet holes you just shot into a barn).
A compound impactor with a leading and secondary round might work, for example. Difficult to package into a small-arms round, but possible. Keeping everything on the same impact point would be the crucial element.
(Unless you mean something that starts out the same size as the one in the video, in which case I can't imagine that two halves of a .30-06 would penetrate any better than one whole .30-06.)
http://www.tungsten-alloy.com/armor-piercing.htm
Another alternative, depleted uranium, relies on the exceptionally dense, and self-sharpening DU penetrator to defeat armour. Rather effectively.
And of course there are things like RPG-30 Kryuk to exploit that - fires two rounds, the first, triggering round is small and just enough to trigger the protective armor, and they're both fired at once from the same device to ensure that they hit the same spot just one of them tuned to hit juuuust a bit before the main round.
Really? That would be quite an achievement.
Also, how about glass foam? I imagine you can blow large and cheap hulls from foamed molten glass.