In regards to ERA

[IronsightSniper]

I was just curious about how much of an effect would changing the face plates of a say, 2nd or 3rd generation ERA would have against an incoming HEAT (tandem) or APFSDS projectiles. And before you assume it, this did come from those thought patterns that go "put DU in everything".

[Guest Jason L]

Flyer disruption is heavily dependant on velocity. DU being crazy dense would need more explosives to offer significant defeat advantages over steel or similar.

Edited September 24, 2011 by Jason L

[IronsightSniper]

Well it doesn't have to be DU specifically, what about other metals? Or perhaps some Ceramics (disregarding the sloped ceramic thingamajig).

[Guest Jason L]

Ceramics are interesting but explosive launch of brittle materials isn't really heavily studied. A paper that just came out this summer showed that certain ceramics have similar performance to steel in ERA configurations.

 

There is compelling evidence to suggest that a design optimum is highest dynamic strength for the lowest density, which points to materials like Ti-alloys, HSLA steels, and possibly even higher strength aluminum as being superior to mild steel.

 

Certainly, good design is definitely more important than the particular material selection though.

[Art40]

HSLA steel is not a good idea.

Standard density of steel and relatively low strength (up to 590MPa yield stress, twice less than armor steel)

[Guest Jason L]

HSLA steel is not a good idea.

Standard density of steel and relatively low strength (up to 590MPa yield stress, twice less than armor steel)

 

Compared to mild steel it is, which is what the basis of comparison is. Also, to get 4340 (close enough to RHA) up to ~1GPa you need to heat treat the shit out of it, 900 series alloys have similar strengths to 4340 when 4340 is at a lower degree of HT.

[TTK Ciar]

Ceramics are interesting but explosive launch of brittle materials isn't really heavily studied. A paper that just came out this summer showed that certain ceramics have similar performance to steel in ERA configurations.

 

There is compelling evidence to suggest that a design optimum is highest dynamic strength for the lowest density, which points to materials like Ti-alloys, HSLA steels, and possibly even higher strength aluminum as being superior to mild steel.

 

Certainly, good design is definitely more important than the particular material selection though.

Jason, I have been wondering about this. Is it strength that is needed, or resilience (the product of strength and ductility)? If the object is to avoid the fly plate from particulating, I would think resilience would matter, and as you suggest titanium and aluminum alloys would fare well.

 

On the other hand, polymers such as polycarbonate, polyurethane, and UHMW-HDPE are even more resilient than the best aluminum formulations, and in some cases may be compounded with ceramic granules (though such composites have lower resilience than the unfilled matrix). HDPE cannot, but PU and PC bond well with a variety of ceramics.

 

An extrusion of 50%/50% composition by weight of 50-mesh boron carbide granules and polycarbonate should provide a density of between 1.8 and 2.0 g/cc, an elongation-to-break of around 30%-40%, and an ultimate tensile strength of about 11kpsi, but I'm not sure what it would do to its modulus of elasticity.

 

Static ceramic/polymer composite armors of 80% ceramic / 20% matrix generally have about 90% of the mass efficiency of the same type of ceramic sintered into whole pieces, so at a guess a 50% B4C / 50% PC formulation would have a ME of 60% of sintered B4C, added to this the resistance contributed by the PC proportional to its mass (PC has a ME of about 2.0). I have been unable to find the mass efficiency of boron carbide against HEAT penetration, just aluminum oxide (which does not bond well with PC) and silicon carbide (which is much more dense).

 

Jason, you know more about ERA than I do, do you think a ceramic/polymer composite might have utility as a fly plate material? Or if not, then what of a ceramic/metal composite?

[Guest Jason L]

Jason, I have been wondering about this. Is it strength that is needed, or resilience (the product of strength and ductility)? If the object is to avoid the fly plate from particulating, I would think resilience would matter, and as you suggest titanium and aluminum alloys would fare well.

 

It is dynamic strength that is needed, which is the magical parameter that is closely related to spall strength and rupture under high strain rate load. Remember that resilience is essentially an "energy absorption until failure" parameter, which isn't directly useful for shock processes and similar high strain rate loading because of the way energy gets imparted and partitioned there.

 

Dynamic ductility is significant but we're finding out I think that's largely due to mesoscale mechanics: adiabatic shear banding, etc. In very simple hole growth models for thin plate perforation its dynamic strength that figures most prominently though.

 

On the other hand, polymers such as polycarbonate, polyurethane, and UHMW-HDPE are even more resilient than the best aluminum formulations, and in some cases may be compounded with ceramic granules (though such composites have lower resilience than the unfilled matrix). HDPE cannot, but PU and PC bond well with a variety of ceramics.

 

An extrusion of 50%/50% composition by weight of 50-mesh boron carbide granules and polycarbonate should provide a density of between 1.8 and 2.0 g/cc, an elongation-to-break of around 30%-40%, and an ultimate tensile strength of about 11kpsi, but I'm not sure what it would do to its modulus of elasticity.

 

Static ceramic/polymer composite armors of 80% ceramic / 20% matrix generally have about 90% of the mass efficiency of the same type of ceramic sintered into whole pieces, so at a guess a 50% B4C / 50% PC formulation would have a ME of 60% of sintered B4C, added to this the resistance contributed by the PC proportional to its mass (PC has a ME of about 2.0). I have been unable to find the mass efficiency of boron carbide against HEAT penetration, just aluminum oxide (which does not bond well with PC) and silicon carbide (which is much more dense).

 

Jason, you know more about ERA than I do, do you think a ceramic/polymer composite might have utility as a fly plate material? Or if not, then what of a ceramic/metal composite?

 

For ERA the material also needs to survive explosive launch beyond it's penetration resistance. Plastics have very low spall strengths (on the order of 0.5 GPa) which means its devilishly hard to launch an intact piece of plastic with explosives. If you try to incorporate ceramic granules you then have to worry about impedance mismatching breaking your plastic-granule interfaces on launch. Unless you can find some way of incorporating deliberate spall failure into penetrator defeat, or find some way of delaying spall failure until defeat is accomplished I think plastics are out for ERA.

 

Same problem for Ceramic-metal composites: your material interface has to survive explosive launch which is complicated by impedance mismatches and layer/granule bonding. Someone will undoubtedly try, but just using relatively monolithic ceramics is pretty new for ERA.

 

 

 

 

 

 

 

Edited November 28, 2011 by Jason L

[lemd]

Jason, what is the current level of Western (NATO) ERA technology, compares to Russian and Ukraine? I don't mean actual kits but theoretically, can western creates ERA as good as the latest of Russian?

[Guest Jason L]

Jason, what is the current level of Western (NATO) ERA technology, compares to Russian and Ukraine? I don't mean actual kits but theoretically, can western creates ERA as good as the latest of Russian?

 

Even without having access to stuff that is surely classified I'd confidently say that our theoretical/design knowledge is as good as anyone else, it's not an especially hard system to understand or model. There really just is no impetus to develop actual kits given we can just license existing ones from friendly nations.

[Harkonnen]

Flyer disruption is heavily dependant on velocity. DU being crazy dense would need more explosives to offer significant defeat advantages over steel or similar.

 

And what makes "DU crazy dense" comparing to tungsten alloy?

[Guest Jason L]

And what makes "DU crazy dense" comparing to tungsten alloy?

 

It doesn't but do you know of any ERAs that use high density (ie greater than 9 g/cc) alloys as the flyer plate material?