t is often argued in some threads that such and such a tank as the equivalent of 1000mm of steel armor or 800mm. Or that a certain tank gun can
penetrate how many mm of armor at a certain range. The fact is that it doesn’t work this way. Modern tank armor cannot be described as being
equivalent to a certain thickness of rolled homogeneous steel, period. There is no equivalency to speak of.
Primarily there are two kinds of threats a tank’s armor has to defeat – Kinetic Energy and Chemical Energy.
In terms of kinetic energy threats, the only kind of projectile that even has a chance at penetrating a heavy tank’s frontal arc is a long rod
projectile. You cannot describe the ability to protect against them as a thickness of steel. Depleted Uranium or Tungsten-Carbide rods will pierce
ordinary steel like butter and any kind of sane thickness is quite irrelevant. If you shoot the LR penetrators into a 5m block of steel they’ll
simply embed themselves in it. This is not how tank armor typically stop the APFSDS-T or DU rounds. There is no armor that is say 300mm thick, but
equal 1200 mm of steel and hence cause a penetrator that will go through 1000mm of steel to be stopped after 250mm of this “miracle armor” and
stick out like a dart on a dart board. It doesn’t work like that. The key to stopping long rod penetrators is fracturing it on impact. If you are
successful, you will have an inch or two worth of a dent and there will be practically no penetration. If you fail, the rod will most likely go right
through your armor no matter how thick or thin it physically is. Generally speaking, the system employed to achieve this is a very high tensile metal
face plate that is relatively thin. And their effectiveness depends highly on the penetrator itself. The US uses Depleted Uranium for this. Most
others use tungsten carbide or simply face hardened steel. Tungsten carbide is actually harder than DU, but DU is sufficiently hard and is less prone
to shattering than TC. In the end, 80% of the tank’s ability to stop sabot KE rounds comes down to 10 to 20mm worth of armor.
When it comes to Chemical Energy warheads, there are primarily two types – HEAT and HESH. HEAT is the more common of the two today, and despite the
name the way it works has nothing to do with heat. So, you can forget about any claims that ceramic armor is superior against HEAT rounds because they
do not conduct heat. This is utter rubbish. HEAT – High Explosive Anti-Tank – rounds work by focusing explosive energy down a very narrow jet.
They do so using a geometrically precise reverse cone hollow charge of high explosive which when detonated uses about 2/3 of its explosive energy to
force the remain 1/3 or so into a concentrated jet. This jet penetrates armor by pressure, not by temperature. Stopping HEAT rounds really comes down
to either dissipating this jet or giving it sufficient room to dissipate on its own. The simplest way is to have an armor skirt a good half a meter
away from the tank’s armor. This is used in WWII on many German tanks when HEAT rounds started to become commonplace. The other way is to use a
reactive armor. Both explosive and ceramic composite armor (such as Chobham) are in essence reactive armor. They work by reacting to the HEAT jet and
disrupting it. ERA works by itself exploding. The resulting explosive force and the metal plate thrown out by it disrupts the focus of the HEAT jet
rendering it a lot less effective that it otherwise will be. Chobham type armor typically crushes under the jet. This pulverizes the ceramic layers
and turns the ceramic into a high modulus cloud of pulverized ceramic. This dense ceramic dust, under tremendous pressure, is almost like a fluid. As
it gushes out in the face of the HEAT jet and neutralizes its energy. HESH – High Explosive Squash Head -- warheads work by flattening itself
against the armored surface like a lump of clay. When detonated, the explosive force causes transfer through the metal – like a billard ball
striking another, stopping and causing the other ball to get in motion. This force causes the inside surface of the armor to buckle and detach. The
armor itself hence becomes the killing mechanism, showering the occupants inside the tank with shrapnel. Again spacing works against HESH. However,
ERA and composite armor in their basic form do not. As long as you have continuous armor between the outer and inner surface, HESH will most likely
kill you. Again, trying to measure resistance to chemical warhead as a “thickness of steel” worthless.
To sum it up, basically, to stop kinetic energy weapons, it really comes down to a few centimeters of very hard plating. To stop Chemical Energy
weapons, it is all about spacing and reactive armor (not just ERA, but passive ones like Ceramic composites as well).
The common armor concepts used in modern tanks is as follows:-
(1) Steel armor. This is cheap and easy to make. It can be a casting or made from welded plates. Heat treating can be used to harden the faces of
steel armor to improve performance against kinetic energy weapons at the expense of resilience against chemical warheads. Classic tanks like the M48
and T55 uses this.
(2) Aluminum armor. This is very light. Every pound of aluminum armor is also more effective against chemical warheads as an equivalent pound of steel
since aluminum is bulkier but less dense and stronger than steel by weight. The M113 uses aluminum armor – too little of it really to be of much
value. The protection of the M113 was bad to the point where assault rifle rounds with steel cores will penetrate it at close range.
(3) Perforated steel armor. This involved steel armor that is in effect drilled full of holes perpendicular to the face of the armor. The holes are no
bigger than half the expected diameter of the expected penetrator. This allows the armor to be 40-50% the weight of a solid block of steel, but 70% as
effective against kinetic threats. It also makes the armor bulkier and full of empty space, which enhances survivability against HEAT and HESH type
warheads. Usually the perforated blocks will form the core of the armor, with harden steel strike faces and/or unperforated panels capping off both
ends. Advanced versions of perforated armor use hard cylinder liners for the holes to increase kinetic protection and/or ceramic fillers within for
protection against HEAT rounds. Despite popular believe, the original Leopard II does not use Chobham type ceramic laminate armor, rather it uses
perforated armor. Because the orientation of the holes are very important to effective protection, perforated armor does not lend itself to curved
surfaces very well.
(4) Ceramic Laminates (Chobham type). This is usually a laminate of multiple layers of metal and ceramic plates. The ceramic used is usually a guarded
secret, but it is speculated that Alumina (Aluminium Oxide or Sapphire), Boron Carbide (the hardest simple ceramic), and similar materials are
probably used. Sometimes synthetic fibers are used to enhance the effectiveness of the metal backing plates and metal mesh is integrated into the
ceramic plates to localize shattering when struck. Sometimes the term Ceramic Matrix Composite is coined to discribed laminated armor employing these
advanced techniques. Because the ceramics are both very hard and crushes into a HEAT jet disrupting retro-fluid action, it is very effective against
HEAT warheads. Because it is numerously layered, it is more effective against modern HEAT warheads which frequently has tandem charges to defeat ERA.
When it is hit by a tandem charge, the precursor charge will not expend the entire reactive package just the top layer or two. Ceramic laminates also
resist kinetic energy penetrators better than steel armor of a comparable weight though not as drastically better as they resist shaped charges from
chemical warheads. Pound for pound, this is currently the most effective single armor concept though it is frequently used in conjunction with other
armor concepts. Because ceramics cannot be bent into curved surfaces, tank designs using ceramic laminates also tend to be squarish.
(5) High tensile alloy faced armor. This is an arrangement common amongst state of the art tanks. Basically, it is a thin sheet of tungsten alloy or
in the case of late model M1 tanks Depleted Uranium acting as the strike face of whatever the armor type is underneath. The mission of this is to
fracture long rod penetrators and render them practically useless. Tungsten-carbide is actually harder than DU, but DU is also very hard and is less
prone to shattering making it a superior material for penetrators and strike faces. The problem is DU dust is toxic and is very unhealthy if breathed
(6) ERA – Explosive Reactive Armor. This is a cheap and relative light way of protecting against HEAT projectiles. Basically it is high explosive
sandwiched between steel plates which explodes when it is hit by a HEAT warhead. It is practically useless against kinetic rounds and there is no
repeated strike capability making it very venerable to tandem charge warheads. But it is light, modular and easy to apply over existing vehicles. You
will see this on Soviet tanks and Chinese tanks a lot. Generally it is a quick fix for tanks which does not use advanced ceramic laminate type
“passive” reactive armor.
(7) Spaced armor. This is one of the oldest tricks in the book and really the only one that does not involve heavy materials and the only thing that
is truly effective against HESH rounds. This can be simple slats or skirts mounted some distance off the sides of the hull or turret. It is also a
feature inside the advanced construct of some tanks. An empty space is just about as good as steel in countering shaped charges and empty space is
weightless. Modern internal spacings also tend to have angled baffles to channel the jet off the centerline to further increase effectiveness against
chemical energy attacks.
(8) Advanced Combinations. Most of the best tanks in the world use a combination of two or more of the above.
Oh, BTW, because they offer more protection for the same weight compared to steel but takes up more space, perforated armor and ceramic laminate armor
is sometimes called "Bulky Armor".
The current armor package for the M1A2 for example uses Depleted Uranium strike faces, an advanced Chobham type ceramic laminate, baffled spacing and
Kevlar type supplementary backing for critical spaces. The exact thickness and construct of the laminated armor blocks are of course highly
classified. I believe the core armor for the up armored Leopard 2s remain the same as the original Leopard 2’s perforated type. However, the big
chunks of additional armor probably has high tensile strike faces and are probably mostly hollow – if they were not largely hollow, the Leopard 2A6
would be a lot more than 70 tons. Only the Chinese military officials will know the exact composition of the armor on the Type 98 and 99 tanks.
However, if I have to take a guess I say they are using perforated armor with hardened strike faces and ERA. This will be consistent with the need for
squared profiles and the modest weight of the packge.
I did not write this.
i cut and paste this from sinodefence.com. posted by member jatt2ooo