Patent: nodes vs grid for edge effect

[TTK Ciar]

I was cruising armor patents and stumbled on this:

 

http://www.freepatentsonline.com/6912944.html

 

This in particular caught my eye:

an integral ceramic plate a plurality of interconnected ceramic components providing said integral plate, said ceramic plate having a deflecting front surface or a flat front surface, and a rear surface, said front surface having a plurality of nodes thereon;

....

an integral ceramic plate comprising a plurality of interconnected ceramic components providing said integral plate, said ceramic plate having a deflecting front surface or a flat front surface, and a rear surface, said front surface having a plurality of nodes thereon;

....

In other embodiments (not shown), the shape, size, distribution pattern, and density of distribution of the nodes may be varied by those skilled in the art to achieve improved deflecting and defeating capabilities.

....

In comparison to the prior art, ceramic components devoid of nodes, the personnel ceramic armour system shows reduced depth of penetration or no penetration.

 

A ceramic component devoid of nodes can only protect an object from the threat of a level IV armour-piercing projectile having a diameter of 7.62 mm. In comparison, the use of a single layer of a MAP ceramic component system can deflect and defeat a threat posed by a level V armour-piercing projectile having a diameter of 12.5 mm.

....

The effectiveness of a ceramic component, and of an armour using such ceramic components, in protecting an object from the impact of projectile is improved by providing nodes on the front surface of the ceramic base. The provision of nodes adds the deflecting capability to the ceramic component and to the armour using ceramic components. The nodes change the angle of the impacted projectile and retard the passage of the projectile through the ceramic component. The projectile is then easily defeated. The presence of nodes on the ceramic component disclosed in the present invention is more effective in protecting an object than a ceramic component devoid of nodes, thereby eliminating the need for using thicker ceramic components for protecting an object from the same level of threat.

What it seems to be describing is using studs ("nodes"), rather than a grid or perforated plate, to induce the edge effect in the penetrator, spaced out across the surface of the armor such that the penetrator must strike one.

 

A quick pen-and-paper sketch and some math demonstrates that such an arrangement is considerably more mass-efficient than a bi-axially asymmetrical grid. A grid with 12.7mm x 38mm aperatures and 3mm wide walls weighs about four times as much as 5mm diameter conical studs arranged in a triangular pattern 12.7mm apart.

 

Furthermore, the use of conical studs offers an elegant means of tuning this "spoiler" layer against threats of different diameters. To spoil 12.7mm and 7.62mm threats, studs could be fashioned such that their tips are 12.7mm apart, but the cone walls lower down on the studs' lengths are only 7.62mm apart. This would provide additional mass savings, as the worst-case stud material depth offered to the 7.62mm threat would be less than that offered to the wider 12.7mm threat.

 

The patent *seems* to be claiming that a ceramic thickness sufficient to stop a 7.62mm threat will stop a 12.7mm threat when these "nodes" are present, but without knowing exactly which projectiles are being compared (7.62mm tungsten core vs 12.7mm lead core, perhaps) it cannot be ascertained whether these studs are affording a 1.2x, 2.0x, or more improvement in protection.

 

The diagrams referenced in the patent text can be viewed here:

http://www.freepatentsonline.com/6912944.pdf

 

Cheers,

-- TTK

Edited October 7, 2006 by TTK Ciar

[jwduquette1]

Interesting. Thanks TTK. If only we had some ballistic testing data on the system.

[Mobius]

.50cal rounds are 12.7mm not 12.5mm.

"Missed by that much."

Edited October 12, 2006 by Mobius

[Sebastian Balos]

I was cruising armor patents and stumbled on this:

 

http://www.freepatentsonline.com/6912944.html

 

This in particular caught my eye:

 

What it seems to be describing is using studs ("nodes"), rather than a grid or perforated plate, to induce the edge effect in the penetrator, spaced out across the surface of the armor such that the penetrator must strike one.

 

A quick pen-and-paper sketch and some math demonstrates that such an arrangement is considerably more mass-efficient than a bi-axially asymmetrical grid.  A grid with 12.7mm x 38mm aperatures and 3mm wide walls weighs about four times as much as 5mm diameter conical studs arranged in a triangular pattern 12.7mm apart.

 

Furthermore, the use of conical studs offers an elegant means of tuning this "spoiler" layer against threats of different diameters.  To spoil 12.7mm and 7.62mm threats, studs could be fashioned such that their tips are 12.7mm apart, but the cone walls lower down on the studs' lengths are only 7.62mm apart.  This would provide additional mass savings, as the worst-case stud material depth offered to the 7.62mm threat would be less than that offered to the wider 12.7mm threat.

 

The patent *seems* to be claiming that a ceramic thickness sufficient to stop a 7.62mm threat will stop a 12.7mm threat when these "nodes" are present, but without knowing exactly which projectiles are being compared (7.62mm tungsten core vs 12.7mm lead core, perhaps) it cannot be ascertained whether these studs are affording a 1.2x, 2.0x, or more improvement in protection.

 

The diagrams referenced in the patent text can be viewed here:

http://www.freepatentsonline.com/6912944.pdf

 

Cheers,

-- TTK

376794[/snapback]

 

 

Interesting, I'm sorry I was absent for some time and didn't participate.

 

If it really works, using studs instead of perforations is interesting and might give some benefits regarding mass efficiency, but what worries me is the cost and complexity of manufacturing such a complex shape out of ceramics. Large and complex chapes are pretty hard to obtain if you want a high quality material with homogenous and thus less brittle structure.

I'd propose using a different method, which might prove to be more cost efficient. I'd use a perforated plate (preferably Al-alloy), with partial perforations (not all the way through), into which small ceramic segments would be inserted. This way, you could use smaller amount of higher quality ceramics at even lower weight (2.7 g/cc for Al-alloy against 3.5-3.9 for Al2O3 ceramics), combined to a better multi-hit capability due to a higher ductility of Al-alloy compared to ceramics. Furthermore, the bach side of this arrangement is smooth, alloying it to be combined with non-explosive reactive armor, i.e., to be backed by rubber or polymer layer, and finally, another metal layer.

 

Regards, Sebastian

[wooki]

Interesting, I'm sorry I was absent for some time and didn't participate.

 

If it really works, using studs instead of perforations is interesting and might give some benefits regarding mass efficiency, but what worries me is the cost and complexity of manufacturing such a complex shape out of ceramics. Large and complex chapes are pretty hard to obtain if you want a high quality material with homogenous and thus less brittle structure.

I'd propose using a different method, which might prove to be more cost efficient. I'd use a perforated plate (preferably Al-alloy), with partial perforations (not all the way through), into which small ceramic segments would be inserted. This way, you could use smaller amount of higher quality ceramics at even lower weight (2.7 g/cc for Al-alloy against 3.5-3.9 for Al2O3 ceramics), combined to a better multi-hit capability due to a higher ductility of Al-alloy compared to ceramics. Furthermore, the bach side of this arrangement is smooth, alloying it to be combined with non-explosive reactive armor, i.e., to be backed by rubber or polymer layer, and finally, another metal layer.

 

Regards, Sebastian

378762[/snapback]

No, the nodes (as described) would not significantly increase cost. Especially with variable rate pressureless sintering.

 

cheers

 

 

W

[Luckyorwhat]

So are they talking about comes, pyramids, or something else? Cones are mentioned here, but the patent shows semi-spheres, or oblong domes? As well, do they have a cavity in the middle at the top, or a nipple?

Edited October 15, 2006 by Luckyorwhat

[Sebastian Balos]

I must admit I've never heard of sintering that does not include pressure. Sintering involves pressure and temperature by itself. Can you elaborate? How are the pores between ceramic pellets reduced without pressure?

 

Anyway, ceramics are significantly more expensive than Al-alloys (5-20 times).

 

Regards, Sebastian

 

 

 

No, the nodes (as described) would not significantly increase cost. Especially with variable rate pressureless sintering.

 

cheers

W

379655[/snapback]

[EchoFiveMike]

I would think that a ceramic rod inserted into a cup on steel armour would be most effective; you could then couple the ceramic rod to the armour using a ceramic ring, sized to whatever diameter need to defeat threats that could potentially make it past the extended rods.

 

Wouldn't the greater ductility of steel make it more effective than Al in this application? S/F....Ken M

[TTK Ciar]

Sorry for not chiming in 'til now .. work has been keeping me pretty busy. What time the office doesn't consume, my wife wants for herself, and tanknet gets squeezed out..

 

I don't know how much incorporating nodes as part of a sintered ceramic tile would increase their cost .. I'm not up on the latest fab technologies.

 

The nodes wouldn't need to be ceramic, though. Ceramics would offer superior mass efficiency, perhaps, but the nodes contribute so little mass to the overall armor system that one would see diminishing returns by pursuing an extremely mass-efficient spoiler system. The principle described in the patent would apply equally, I think, to nodes of steel or aluminum or other lower-cost material laid over the ceramic component. A node-based system would be less massive than a grid-based system of same material, so a steel grid could be replaced by steel nodes, for improved mass efficiency, an aluminum grid could be replaced by aluminum nodes, etc.

 

Sparsely embedding ceramic studs in an aluminum plate is an appealing proposition, Sebastian. It would avoid the need for a specialized sintering system, and could be easily assembled from off-the-shelf materials. The ceramic studs would benefit some from containment, though harder materials do better at containment than softer materials like aluminum, and it seems like one could use a lower-density material to simply hold the studs in place .. perhaps the ceramic studs could be enclosed in steel or titanium, and the capsules held in place by a plastic component? Though that would involve more steps in the fabrication process than your aluminum plate, and drive up costs.

 

E5M, I'm not sure what you're proposing, wrt coupling the ceramic node with the armor via a ceramic ring. Could you explain?

 

The greater strength and hardness of steel would make it a more effective containment material than Al, but Al alloys suitable for armor are generally more ductile than armor steels .. I think the greater ductility could work for you if it successfully kept the node from detaching from the armor system.

 

I'm also thinking that the higher density and hardness of a steel component surrounding the spoiler node might reduce the edge effect benefit -- you want one part of the penetrator to interact with a resistant body while the other part meets less resistance, so that the disparity induces yaw and shearing forces within the penetrator body. A plastic or aluminum structural component would impose less resistance on the part not interacting with the ceramic spoiler node. But perhaps compared to the resistance imposed by the ceramic, the difference between the resistances imposed by aluminum and steel is less significant? I'm not sure.

 

OTOH, metallic conical nodes adhered to the armor's frontmost layer would be pretty easy to fab, and the material cost would be low. We have that IJIE paper from Chocran + friends to quantify the benefits of using steel and aluminum spoiler material, but they didn't test ceramics .. maybe we can extrapolate some numbers? Then some estimates of the benefits of these different approaches could be compared against their costs (both, mass-wise and financial).

 

-- TTK

[EchoFiveMike]

Something like this, for ease of replacement/assembly. The ceramic can be contained within a steel shell, which can be externally threaded for troops in the field to replace. The base sockets can be welded to the base armour plate.

 

The idea being that the long rod will interact with a larger diameter(greater threat) projectile at a increased standoff from the armour while the larger diameter shorter ring is still thick enough to defeat lessor threats while saving overall mass. Depending on length of the rods, this may also provide useful effects against shaped charges, such as disruption of the cone, fuze shorting, etc etc etc.

 

The alloys I'm familiar with are 4140, 4150 and 4340 steels and 6061 and 7075 aluminums, generally T6 hardness.

 

7075 vs 6061 Comparison Chart:

Alloy Tensile Strength Yield Strength Brinell Hardness

6061-T6 45,000 PSI 40,000 PSI 95

7075-T6 83,000 PSI 73,000 PSI 150

 

Seems to suck hard across the board compared to the steel components I routinely use. This being for 4340, for example

 

TYPICAL PROPERTIES: ASTM A434 CLASS BD (Approximate - not for specification) Tensile (psi) Yield (psi) Elongation

140,000 110,000 14%

 

Admittedly, for a given mass you get greater volume of Al alloys but given aluminum's low strength and hardness, I don't see that being a good choice here. S/F.....Ken M

Edited October 17, 2006 by EchoFiveMike