Shakie

4 hours ago, Alzoc said:

Since this thread is more or less our general armor thread:

 

http://www.opex360.com/2017/12/17/pme-francaise-a-mis-point-blindage-plus-resistant-et-deux-plus-leger/

 

B4C ceramic claimed to have 20% more hardness than the typical B4C while being twice as light.

 

To achieve that they start with a nano powder of B4C and to keep the grain at a nano scale they use a flash sintering process (Pulsed current in a high pressure environment) claimed to be 20 times faster than usual process (so the grain don't have time to grow I guess).

 

No idea about the maximum size and the shape of the finished product.

I didn't think anyone actually used B4C in tank armour due to its cost? I thought they only used it to absorb neutrons in the event of a nuclear detonation.

1 hour ago, Collimatrix said:

 

Welcome to SH Shakie!

1)  I think @Bronezhilet had some papers on testing different materials in NERA arrays.  It looked like most of the materials were organic polymers, so rubber is probably not far off the mark ever if it isn't 100% ideal.  To be honest, I'm not sure exactly what's going on when the interlayers in NERA vaporize.  I'm not sure if it's just dissociating under the energy, or whether it's actually undergoing some sort of exothermic reaction like the fluorocarbon/metal mixtures in reactive shaped charge liners are.  I know that there have been experiments with doping the rubber layers in NERA with a bit of high explosive to give it some more kick.  In the experiment I saw, it didn't work particularly well.

 

2)  I believe that the heavy ERA designed specifically to counter KEPs is designed to snap the projectile.  Other reactive armors don't necessarily work the same way.  I've seen papers on ERA with low-density ceramic and polymer flyer plates, and it apparently works as well as steel on a weight basis.  Look up "The Defeat of Shaped Charge Jets by Explosively Driven Ceramic and Glass Plates" by Paul Hazell if you have access to journals and you're curious.  That said, there may be some use of heavier materials in reactive armor arrays.  @SH_MM is of the opinion that the depleted uranium in the Abrams' armor is incorporated into some sort of NERA, although I personally suspect otherwise.

3)  I was actually under the impression that the kevlar was providing energy for the movement of the metal plates, but I would have to double-check because I am not sure.  Aramids have very strong chemical bonds, and if those bonds were to come apart under the energy provided by an incoming penetrator, they should provide lots of energy for the plates.

I see. I was under the impression that NERA worked basically the same way as ERA; just with less energy and multi-hit capability. I thought that was why there had to be air gaps between NERA sandwiches, so that the metal plates have something to expand into, rather than getting squashed against each other.

Also, I'm not sure if there's a separate thread for this, but here's my first (not to scale) attempt at armour design, I would appreciate it if someone would critique it. First, you have ceramic tiles encased in staballoy (the green/black layer) to break up the incoming projectile. Next there's the NERA (dark grey/brown layers), with rubber sandwiched between HHS plates and kevlar layers. Note that some of them are parallel to the first layer, while others are perpendicular; this is to put any incoming projectiles under as much stress/strain as possible. Then at the very back there's an air gap followed by a slab of Ti-6Al-4V to catch any remaining fragments. Finally, this whole arrangement, which is 400mm thick total, would be arranged in multiple layers to defeat multi-segment KEPs. For example, 3 identical such armour arrays could be arranged back-to-back, for 1200mm thick armour in total, and can defeat 3-segment KEPs. This would also keep production costs down since each layer is identical. Something similar could be used for the turret as well, though you'd have to arrange it carefully to manage the sheer bulkiness. I also haven't worked out how heavy it is.

Hi everyone,

This is my first post, but I've been lurking for quite a while. I was just wondering what the best materials are for making NERA out of, disregarding the costs? It seems to me that for the middle, reactive layer, you need to consider both how quickly it expands when struck, and also how much it expands (i.e. maximise the expanded volume:unexpanded volume ratio). I have no idea what the best material for this is, I assume the fact that's its usually rubber is simply to keep the costs down.

Because the purpose of NERA is to both force more of the expanding metal plates into the path of the KEP/HEAT jet, and to snap it in half, it stands to reason the best material for said plates would be something hard and dense; staballoy for example. It increases the weight, but due to the way NERA increases the protection for a given thickness of metal, and because the armor is mostly air anyway, surely it would be more efficient overall to use fewer layers of staballoy than more layers of steel NERA. Again, presumably the main everyone uses steel is simply to keep the costs down. Or am I just completely wrong?

Also, another question; there was another post showing how some NERA systems have kevlar embedded in them, between the rubber and steel layers, with claims of up to 60% increased protection compared to regular NERA. How exactly does kevlar increase the efficiency of NERA so dramatically?