Metal Foam Armor?

NCSU has developed a Stainless Steel Foam armor plate.

New research from North Carolina State University and the U.S. Army's Aviation Applied Technology Directorate shows that stainless steel composite metal foam (CMF) can block blast pressure and fragmentation at 5,000 feet per second from high explosive incendiary (HEI) rounds that detonate only 18 inches away.

I was just thinking of metal foams the other day, in an totally unrelated way, and then this came up.

Many military vehicles use armor made of rolled homogeneous steel, which weighs three times as much as our steel-CMF," Rabiei says. "Based on tests like these, we believe we can replace that rolled steel with steel-CMF without sacrificing safety, better blocking not only the fragments but also the blast waves that are responsible for trauma such as major brain injuries. That would reduce vehicle weight significantly, improving fuel mileage and vehicle performance."

For this study, researchers fired a 23×152 millimeter (mm) HEI round -- often used in anti-aircraft weapons -- into an aluminum strikeplate that was 2.3 mm thick. 10-inch by 10-inch steel-CMF plates -- either 9.5 mm or 16.75 mm thick -- were placed 18 inches from the aluminum strikeplate. The researchers assessed that the steel-CMF held up against the wave of blast pressure and against the copper and steel fragments created by the exploding round, as well as aluminum from the strikeplate.

"Both thicknesses of steel-CMF stopped the blastwave, and the 16.75 mm steel-CMF stopped all of the fragments from 15 mm2 to over 150 mm2 sizes," Rabiei says. "The 9.5 mm steel-CMF stopped most, but not all, of the fragments. Based on the results, a 10 mm steel-CMF plate would have stopped all of the frag sizes."

Very very interesting stuff, 3/8" of ss foam stopped the blast wave and most fragments from a 152mm AA round, thats pretty impressive.
Lightweight metal foam blocks blastwave, debris from high-explosive rounds

a reply to: punkinworks10

Here’s a short video showing the foam. It’s pretty impressive stuff, imho. (Video is from 2016)

I have several initial thoughts, but I'd have to see the actual set up first, and I have to be somewhat careful on the topic. But composite metal foams combined with metal - or ceramic- strike plates and a spall liner is definitely a thing making headway. My guess is this is a steel strike plate in front of a CMF (the aluminum strike plate referenced in the test is the target for the AA round). So in appplication, it won't replace metal armour, but it might let you get away with rather less thick strikeplates offering similar protection, and superior spall protection at less weight.

a reply to: TerryDon79

That's her ESAPI test. Same principles involved, but different application. That was level III protection for body armour. It had a ceramic strike plate, I believe, and a kevlar spall protector.

a reply to: RadioRobert

Oh ok. I thought it was used in the same way.

Still, no less impressive.

a reply to: punkinworks10

"We have developed two technologies for manufacturing CMFs," Rabiei says. "One is based on casting a low melting point matrix material, such as aluminum, around hollow spheres made of a material with a higher melting point, such as steel. This creates aluminum-steel CMFs, for example. The other technique is based on sintering, or baking, the matrix powder around prefabricated hollow spheres. This creates CMFs such as steel-steel, which consist of steel hollow spheres in a steel matrix."

phys.org - Metal foam handles heat better than steel, study finds.


That was March 2016. I thought, "Hey, that is kind of cool! I wonder what else they would use it for?" Now, a couple years later they have a good use!"

I think it will be a combination of materials that will be used. Like 2 graphene layers can stop bullets. Next CMF armor in ceramic packets. Then maybe even something else. Maybe large holed CMF then smaller holed CMF?

There was the guy at Kansas State that made liquid polymer filled with various elements that when baked turned into a high temperature ceramic. I was thinking "pipe coating" but why not armor?

Cool stuff!

The context I was thinking of metal foam in, was that of an idea from one if my fave SciFi authors, Peter Hamilton.
In his "Commonwealth" series, foamed metal ingots are used to deliver metals, that are processed in space, to earth.
Million ton foamed ingots are de-orbited from LEO, and dropped into the ocean, where they float and are towed to port for further processing.

a reply to: punkinworks10

I don't know how much volume of water a million tons of foamed metal would displace, but it'd be a lot. Wouldn't want to live on the coast in that world

Add that with this...

This is the world’s first 3D Printer designed to print in continuous CARBON FIBRE. Want to print parts, tooling, and fixtures with a higher strength-to-weight ratio than 6061-T6 Aluminium? With a special blend of thermoplastics which hardens during the printing process? Carbon Fibre 3D Printing has hit the Australian market and 3D Prototyping are able to assist with your parts manufacturing.

Carbon Fibre 3D printing

Carbon fibre composites are used generally as a stiffener and spall catcher behind ceramic strike plates. You typically want a layer of kevlar behind that because hard carbon fibres fracture easily under point pressure creating more spall (helps stop big hunks of metal and ceramic when the ceramic cracks to dissipate energy, but also produces smaller spall of its own with less energy). In this case you'd have the CMF performing that role essentially and doing a better job of energy dissipation. You could use a sheet of flexible carbon fibre instead of aramids like kevlar as a spall catcher and trauma plate behind something like CMF (or hi-hard or ceramic or whatever), but composites (like the 3d printing) are prone to cracking and producing spall.

I have more questions than answers on this particular CMF, but I haven't seen anything questionable about how it works in general. I'm no longer working directly on ballistics science, and I'm not sure how much I know is still proprietary, so I'm equal parts curious and hesitant to provide examples or specific questions.

I would love to see this tried with Titanium or Cermet's(whatever happened to those? They were popping up as the next big thing in armour in the late 80's or early 90's I recall). Imagine the weight saving on an A-10 if you could replace the Ti bathtub with one made of the SS foams or even a Ti foam. You could probably cut the combat weight of an M1 Abrams or similar Western tank by 30-50% which would have huge implications. The list goes on and on.

a reply to: Blackfinger
I had to look it up because alloy tables is not something you look at after TAFE training unless you are a sheety. But 6061-T6 isn't as strong as 2024-T3, still its impressive nonetheless and will only get better.

a reply to: thebozeian

Again, no longer my area, but my guess is this isn't going to be as useful against a large penetrator for say an MBT. But it might find use on IFV's and up armoured HMMWV's. Maybe as a layer of protection under or as part of another system for MBT protection. This is all about attenuation and stopping frags and spall. Can't do that until you stop the projectile.

a reply to: RadioRobert
True, as part of a system on an MBT it would be useful. Maybe a replacement for certain layers in Chobham style armours or combined with an Active APS system? Certainly IFV type vehicles would benefit greatly from it as they have also ballooned in weight over the last 40 years. I wonder what the thermal properties of such foam materials are? There may be other applications in aerospace other than armour that they would prove useful at.

a reply to: thebozeian
6061,s good for fairings ,fluid tanks and castings..Strongest aluminium is 7075 with its high tensile strength.Is a b@stard to bend in T3 condition.

7075 aluminium alloy's composition roughly includes 5.6–6.1% zinc, 2.1–2.5% magnesium, 1.2–1.6% copper, and less than a half percent of silicon, iron, manganese, titanium, chromium, and other metals. It is produced in many tempers, some of which are 7075-0, 7075-T6, 7075-T651.

I can see the powdered foam as a good filler for layered armour in aircraft..The Bf109 used layered sheets of aluminium (off memory about 27 sheets) to protect the pilot from behind the seat.

Why dont we just use titanium?

Its super light..

And ive watched countless youtube videos of .50 cal rounds bouncing off relatively thin titanium plates.

It seriously makes me wonder why we dont have titanium body armor with kevlar and padding behind it. Its bullet proof.

Sure titanium is expensive.. but its a whole hell of a lot lighter and the reduced weight would save $$.

The big reason? Cost. Titanium is quite expensive. It is quite hard to machine. It also isn't that amazing ballistically in thin sheets, I promise. It's not really better than Hi-hard because of its density. It's lighter than most metal armour, but it isn't exactly light. Typically heavier than most ceramics for the same level of Vo. For body armour, you actually have to deal accutely with energy dissipation as well as stopping the round, and that is generally bulky. It doesn't do any good to stop a round if your insides get turned into jelly. It's comparatively brittle which helps for the first hit, but really hurts after multiple hits. It's splendid for many uses. On a vehicle you can mount it so that preexisting structure is absorbing the stresses, and it is lighter than steel equivalence. But on body armor, it isn't that great. And on the whole ability-weight-cost triangle thing, it loses out in most applications.

Why machine when you can print?
Titanium infused 3D Filament

metal foam with silicon carbide

Another version of the substance.

Material Science was one of my interesting courses. (Not my major, just a requirement.)

a reply to: punkinworks10

Slightly off topic but i wonder how long before this gets into the hands of an SCA member or LARPer and they make body armour from it...