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12.7X99 Vs Composite With "foamed" Energy-Absorbing Layer


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Jacob Marx, Marc Portanova and Afsaneh Rabiei have published their findings regarding a composite armor structure consisting of a boron carbide faceplate, a "foamed" energy-absorbing interlayer and an aluminum backing plate, with most of their attention on the novel energy-absorbing layer.

Phys.org wrote up an article about their findings, though the headline is a little misleading. The interlayer is not quite "foamed" like most people think of it, but rather a composite of hollow hardened steel microspheres sintered in a metallic matrix.

 

The mass efficiency of their system vs 12.7x99mm (Ball and AP) varies between tests, but averages out to about 2.1. It's hard to tell from their figures, but my first attempt to calculate its thickness efficiency puts it at about 1.3. I'd like to revisit that to get a higher confidence figure.

The article is here:
https://phys.org/news/2019-06-metal-foam-caliber-rounds-steel.html

Their findings were published in Composite Structures (2019). I have a copy archived here:
http://ciar.org/ttk/mbt/papers/misc/paper.x.armor.ballistic_performance_of_composite_metal_foam_against_large_caliber_threats.marx_portanova_rabiei.2019.pdf

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Jacob Marx, Marc Portanova and Afsaneh Rabiei have published their findings regarding a composite armor structure consisting of a boron carbide faceplate, a "foamed" energy-absorbing interlayer and an aluminum backing plate, with most of their attention on the novel energy-absorbing layer.

 

Phys.org wrote up an article about their findings, though the headline is a little misleading. The interlayer is not quite "foamed" like most people think of it, but rather a composite of hollow hardened steel microspheres sintered in a metallic matrix.

 

The mass efficiency of their system vs 12.7x99mm (Ball and AP) varies between tests, but averages out to about 2.1. It's hard to tell from their figures, but my first attempt to calculate its thickness efficiency puts it at about 1.3. I'd like to revisit that to get a higher confidence figure.

 

The article is here:

https://phys.org/news/2019-06-metal-foam-caliber-rounds-steel.html

 

Their findings were published in Composite Structures (2019). I have a copy archived here:

http://ciar.org/ttk/mbt/papers/misc/paper.x.armor.ballistic_performance_of_composite_metal_foam_against_large_caliber_threats.marx_portanova_rabiei.2019.pdf

 

 

 

Her team also showed that CMF could stop a 7.62 x 63 millimeter M2 armor piercing projectile at a total thickness of less than an inch, while the indentation on the back was less than 8 millimeters. For context, the National Institute of Justice standard allows up to 44 millimeters indentation in the back of armor.

Perhaps they mean 44mm diameter indentation? I find it hard to believe that a <25mm plate could have a indentation nearly twice the thickness of the plate projecting beyond the surface of the plate. That would be some serious plastic deformation without perforation.

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Perhaps they mean 44mm diameter indentation? I find it hard to believe that a <25mm plate could have a indentation nearly twice the thickness of the plate projecting beyond the surface of the plate. That would be some serious plastic deformation without perforation.

That seems odd to me, too, but appears to be correct.

 

From https://www.ncjrs.gov/pdffiles/169587.pdf

 

Types I, II­A, II, and III­A armor are required to prevent penetration from the impact of six

bullets at specified velocities and locations for two types of ammunition. Two of the impacts in

each six-shot sequence must be at a 30º angle. Furthermore, the deformation of the backing

material (a measure of blunt trauma protection) must not exceed 44mm (1.73 in). The armor

must meet these requirements while both dry and wet.

 

My take-away there is that the standard imposes a limit unlikely to be surpassed by any armor system. Maybe a multi-layer polymer film (UHMW-HDPE or PP) would stretch that much without perforation, or a flexible woven fiber aramid layer might deflect that much, but not a metallic plate.

 

(edited for brevity)

Edited by TTK Ciar
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Perhaps they mean 44mm diameter indentation? I find it hard to believe that a <25mm plate could have a indentation nearly twice the thickness of the plate projecting beyond the surface of the plate. That would be some serious plastic deformation without perforation.

That seems odd to me, too, but appears to be correct.

 

From https://www.ncjrs.gov/pdffiles/169587.pdf

 

Types I, II­A, II, and III­A armor are required to prevent penetration from the impact of six

bullets at specified velocities and locations for two types of ammunition. Two of the impacts in

each six-shot sequence must be at a 30º angle. Furthermore, the deformation of the backing

material (a measure of blunt trauma protection) must not exceed 44mm (1.73 in). The armor

must meet these requirements while both dry and wet.

 

My take-away there is that the standard imposes a limit unlikely to be surpassed by any armor system. Maybe a multi-layer polymer film (UHMW-HDPE or PP) would stretch that much without perforation, or a flexible woven fiber aramid layer might deflect that much, but not a metallic plate.

 

(edited for brevity)

 

Now I see the problem. The article conflated the idea of using metal foam for vehicle armor with the standards meant for personal body armor. It should be noted that contemporary infantry are wearing Type IV body armor.

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