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...
> 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.
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).
"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.
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.
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.
