Does Brittle Armor Increase HEAT Effectiveness?

[rexford]

Made the mistake of playing Panthers and Churchill VIII's in the same scenario, where 95mm HEAT wiped the Panthers off the board.

The 95mm HEAT penetration of 125mm vertical is enough to penetrate 80mm/55 degrees with 85% quality (which equals 119mm vertical).

Brittle armor does not always correlate with reduced HEAT resistance. T34 high hardness 45mm plates lose 24% of resistance against 75mm APCBC compared to medium hardness armor, but gain about 10% more resistance than medium hardness armor against HEAT due to the greater difficulty in burning through harder plate.

Panther glacis is medium hardness armor and brittle behavior would come from inclusions, laminations and bad byproducts from the hardening process.

So the question is whether the bad things in some Panther glacis armor that reduce resistance to AP, APCBC and APBC would also hurt when HEAT hits the plate.

I recently came across a British tanker discussion where one fellow said 95mm HEAT was not very good against tanks. With a 1650 fps muzzle velocity 95mm HEAT hits might be hard to obtain on the first or second shots, which might account for the low effectiveness against armor.

Since the brittle areas within the Panther glacis seem to have had about the same hardness as the good areas, it is possible that HEAT resistance may not be compromised by brittle medium hardness armor unless there are laminations (internal areas that are like several plates in contact instead of a single plate).

Do several plates in contact resist HEAT with the same effectiveness as a single plate with similar thickness?

[ July 14, 2003, 05:00 PM: Message edited by: rexford ]

[Shosties]

Good questions. My guess is that interfaces within the armor help to diffuse the jet, given that Chobham is definately some sort of composite.

Though I would never have guessed that plate hardness would have mattered much at given that the jet produces many gigapascals of pressure at the advancing tip.

[ July 14, 2003, 08:00 PM: Message edited by: Shosties4th ]

[rexford]

Originally posted by Shosties4th:

Good questions. My guess is that interfaces within the armor help to diffuse the jet, given that Chobham is definately some sort of composite.

Though I would never have guessed that plate hardness would have mattered much at given that the jet produces many gigapascals of pressure at the advancing tip.

What if the plates in contact are in perfect contact at all points?

Brinell Hardness is measured by pushing a ball into the plate surface and measuring the dimensions of the indentation. The harder the plate the less of a dent, and the higher the attraction between molecules.

I guess hardness indicates molecular bond strength in some way, and the greater the bond strength the more heat is needed to break the bonds and melt the metal. So for a given temperature harder metals are more difficult targets (the pressure at the tip of the HEAT jet is due to high temperature?).

Hardness doesn't relate to more resistance against APCBC because brittleness enters the picture along with stress waves.

[Shosties]

Originally posted by rexford:

Brinell Hardness is measured by pushing a ball into the plate surface and measuring the dimensions of the indentation. The harder the plate the less of a dent, and the higher the attraction between molecules.

Not strictly true. In metals, indentation hardness correlates with compressive yield strength in a rough fashion. Metals (if they are ductile enough) yield at stresses far below those needed to break the diffuse atom-to-atom metallic bonds on a large scale (it doesn't usually make much sense to talk of "molecules" within metallic crystals). They propogate mobile crystalline defects called dislocations instead; these incorporate only a small zone of disrupted bonds. Think of moving a large rug a small distance by pushing a ruck through it rather than dragging the whole rug. Much easier to do isn't it?

At the strain rates taking place from HEAT jet penetration, things get ultra funky (i.e. dislocations being propogated faster than the speed of sound in that material, etc.). I have no idea how Brinell hardness would correlate there, though supposedly stronger will remain stronger and thus put up more resistance and sap the energy possessed by the jet.

Originally posted by rexford:

I guess hardness indicates molecular bond strength in some way, and the greater the bond strength the more heat is needed to break the bonds and melt the metal. So for a given temperature harder metals are more difficult targets (the pressure at the tip of the HEAT jet is due to high temperature?).

Nope... kinetic energy. It's moving at some ungodly number of times the speed of sound (15?). The HEAT jet (which has been shown to actually still be in the solid state by X-ray flash diffraction) is simply pushing the armor out of it's way. The rapid deformation in this penetration zone is going to cause tremendous local heating though (dislocation motion disipates some energy to the crystal in the form of heat, especially when they are forced to move fast).

[ July 15, 2003, 11:53 PM: Message edited by: Shosties4th ]

[rexford]

Thank you for going beyond my mere speculation and adding some factual stuff.

So, does brittle armor resist 95mm HEAT like good quality plate?

[Shosties]

Originally posted by rexford:

Thank you for going beyond my mere speculation and adding some factual stuff.

So, does brittle armor resist 95mm HEAT like good quality plate?

I don't know.

It would make for an interesting experiment to do out in the middle of nowhere, though.