Armor Technology

[Tyler Durden]

Frag it. Paragraph by paragraph, as time allows me.

 

 

 

[Edited by Tyler Durden (30 Apr 2002).]

[Paul Lakowski]

Originally posted by Tyler Durden:

Frag it. Paragraph by paragraph, as time allows me.

 

[Edited by Tyler Durden (30 Apr 2002).]

 

Yeah I know its weird, you can't copy and past anything on that site....too bad!

 

Thanks for this Tyler,when every you are able to get around to it!

[Tyler Durden]

Wadda yah think?

[Bob_Mackenzie]

Originally posted by Tyler Durden:

Wadda yah think?

 

 

I think you are doing a great job - waiting with baited breath for the WW2 part...

 

Cheers

 

Bob

[Paul Lakowski]

Hey Tyler , Professor Igor Minn says you did a good job translating the page. Thanks!

[Paul Lakowski]

In a paper recently published in the Int.J.Impact Engng [Vol-26 pp 735-744] A group of Russian researchers [svirsky etal from Russian Federal Nuclear Center] studied the effects of spaced armor on 120mm 100mm & 46mm shaped charges....the results are quite surprising!

 

They analyse post penetration xrays radio graqphs of thin spaced plates and found the same large post penetration jet disruption zone that I reported about before [ the 14mm thick steel aluminum sandwhich causing a 28-30cm disruption zone in the jet]. They report this segment of the jet has very poor penetration.

 

Any way they tested 120mm shaped charge against a spaced armor target with 200mm steel in three plates @ 7 CD standoff and measured the residual penetration at 77-80% of the reference penetration. Which wasn't given, but it should have be 840mm, thus Pexp should be 65-67cm.So the array offer 19-17cm or 0.85 to 0.95 LOS thickness. Not very good idea!

 

The next test was a 100mm shaped charge fired at a 38mm spaced steel aluminum array @ 5.8 total diameters standoff, infront of RHA semifinite target . This resulted again in 80% reduction of penetration into the reference material. Again assuming 7 CD reference penetration, the spaced plates accounted for 132mm of RHA [ 132/35 ] , so the array was ~ 3.8 times as effective as its LOS/Te values suggest.Not bad at all and consistant with previous findinds [~ 3 x LOS for spaced a single steel plate].

 

Next target was a 100mm shaped charge fired at a 62mm two plate spaced steel array @ 6.8 total diameters standoff . This resulted about 70% reduction of penetration into the reference material. Again assuming 7 CD reference penetration, the spaced plates accounted for 204mm of RHA [ 204/62 ] , so the array was ~ 3.2 times as effective as its LOS/Te values suggest.

 

Finally they tested 46mm shaped charge @ 2.2 CD standoff into RHA and got a penetration of 157±7mm ( 3 shots) [ 70° copper cone 1mm thick liner , with a 6.6 km/s tip V and 350mm break up distance].Next the placed a 1mm plate 0.5d from the reference RHAe and this reduced the penetration to an astonishing 124±5mm penetration[ 3 shots]....again about a 20% reduction in penetration.

 

It seems that the average resistance offered by a spaced armor array -reguardless of its thickness - is about 22% average reduction in modern shaped charge penetration [20-30% range].Infact it seems to suggest that the thicker the spaced plate the less effective it is at defeating shaped charges.

 

This effect is confirmed by Hornemann & Holzwarth [ Int.J.Impact Engng- Vol 20 pp 375-386]. The reference penetration against a straight RHA target was 215mm while penetration into spaced target with 72mm thick spaced plate was 200mm and a similar target with 20mm spaced plate resulted in a penetration of 195mm ...in other words the 72mm spaced plate accounted for 87mm resistance [1.2 x LOS] , while the 20mm plate resulted in 40mm resistance [ 2 x LOS].

 

So all those thin boxes and side skirts placed on the sides and rear of AFVs do offer a considerable increase in resistance. Check out Chieftain tank, by Mk 13 the side profile is >80% covered in boxes and side skirts and Still brew... Thus even the side turret [ 15cm RHA ] should be able to boost the resistance against basic RPG-7 , by 6cm to ~ 21cm....assuming those boxes are empty.The above test figures are for modern jets where increase in the standoff alone should not reduce penetration atall. But early RPG -7 was 'none precision jet' so with the standoff this should increase resistance by ~2 diameter or + 15cm , bringing the average side turret resistance to ~ 36cm.

 

Against a 'precision charge' [RPG-7V],the resistance should be down ~22cm due to lack of any significant standoff reduction at this level. However if the storage boxes are full of material with an average density of plastic that should bring the total side turret resistance to ~ 35cm . Only difference is that it should be equally effective against both 'precision and none precision' jets .

 

 

 

[Edited by Paul Lakowski (05 May 2002).]

[Tyler Durden]

Originally posted by Paul Lakowski:

Hey Tyler , Professor Igor Minn says you did a good job translating the page. Thanks!

 

Thanks, that’s great to hear…and seriously- 14 and 18 hour shifts have been keeping me occupied, and the computers I have access to have no off site connection, so please excuse the delay.

[Paul Lakowski]

New paper in the Int.J.Impact Engng from Russia [Vol-26, pp 675-681]

They test subscale penetration of sand from steel and WHA penetrators of increasing aspect ratio [L/d] and striking velocity.....here are some results.

 

Steel @ 1700m/s

L/d 1:1 resistance 4% of RHA

L/d 2:1 resistance 9% of RHA

L/d 12:1 resistance 12% of RHA

 

Steel 12:1 L/d @

1000m/s 5% resistance of RHA

1300m/s 8% resistance of RHA

1600m/s 11% resistance of RHA

1800m/s 13% resistance of RHA

 

WHA @ 1300m/s

L/d 4:5 resistance 6% of RHA

L/d 7:5 resistance 8% of RHA

 

WHA @ 1600m/s

L/d 4:5 resistance 7% of RHA

L/d 7:5 resistance 10% of RHA

 

WHA @ 1800m/s

L/d 4:5 resistance 8% of RHA

L/d 7:5 resistance 12% of RHA

 

Interesting as v increases, effective resistance increases and as L/d increases so too does resistance.The melt temperature starts to factor in and WHA does better hear than Steel. The semi infinite sand [ 1.8g/cc]target, deformed the 12:1 steel penetrator so it would have had reduced penetration if it hit a main armor wall.However scientist insist that the penetration channel through the sand didn't deviate at all [ no deflection]...suggesting not much in the way of Yaw. Usually increasing yaw leads to increasing deflection.Mind you no measure is made of pre impact yaw conditions.

 

These where with small scale penetrators [8-10 grams], tests on concrete with low compressive strenght and soft lime stone struck by full scale steel 10:1 penetrators [ 3-4kg] @ ordnance velocity [ 1000-1800m/s] yield Te values in the 0.1-0.12 region and showing little deviation due to scaling, however the rods, while eroded are not bent as in the case of sand.

[Paul Lakowski]

ISB-2001 [19th international Symposium on ballistics] has several papers on the expected performance of active defence systems like Arena and methods to counter them, so a review is in order.

 

VM-04 "Analysis of Active Protection system: When Athena meets Arena" Wey , Fleck & Chanteret.

Reportedly Arena was first introduced in 1992 and it incorperates

A MM wave radar for incoming missile detection

32 x'focused grenade' for hitting inbound missile

A control unit.

An accompanging diagram shows radar scanns 50m radius around tank from mast mounted MMwave radar and intercept occurs a few meters from the tank.

 

Simulation of this shows a 150mm grenade is needed to get sufficent 'spray of fragments' powerfull enough to destroy a missile.. In theory a single fragement hit should generate 70% kill while two hits should accumulate a 90% hit chance.

 

Further simulation reveals that % of hits as follows

 

narrow azimuth and wide azimuth simulations where tried with a grenade detonated with to cover a 10° azimuth angle with no repeats while the second grenade covered 20° allowing two grenades to cover each sector with drop in intercept probablity.

 

The results are below...

 

chance of a hit on a missile approaching

Hull Turret from the azimuth in question.

 

Single 10° 85%[4.8m 4 fragments] 90%[2.6m 10 fragments]

overlaping 20° 50%[5.5m 1 fragment] 90%[2.1m 6 fragments]

 

 

Clearly some precise detonation is needed since a change of detonation angle reduces the number of fragments dramatically [ ~ 3-4 fragments] and lower hit chance... 1 fragmemt = 50% over hull compared to 4 fragments resulting in 85% hit.

 

These are the results of lab simulations [controlled] and battlefield conditions should bring these figures down dramatically.For example its reported that this system doubles the effectiveness of the tank...which can be interpeted as 50% hit chance against incoming missiles.This is probably a good ball park figure to work with when estiamting the effectiveness of these active defence systems.

 

In WM-01 "Active Protection against KE-rounds and shaped charges at short distance" M- Held, reports that Droz only covers 40°either side of the gun while Arena covers 340°

 

VM-14 "Defeating Active Defence Systems by Double firing of missiles." M-Held, reports that Drost fragment covers only ± 0.5m meter area while Arena is ± 2m either side of the grenade direction.

 

Held also notes that the sensor will have dead time thats 1-3 seconds that can't get a detection so firing two missiles from the same launcher should be an effective way to ensure second missile reaches target.[Alternatively two launch systems within 10m of each other can diplicate this if some precise system can 'similtaneously fire' the missiles].Held estiamtes that if the system is automated it can place the second missile 20m behind the first giving enough seperation to clear the debri field before impacting the target, stationary or on the move.

 

Held suspects that BMP with 'Khrizantema' missile system may well already have this capability.

[Paul Lakowski]

A recent paper in the Int.J.Impact Engng [Vol26,pp831-841] Webber et al ,examined the KE resistance of layered ceramics [AiN] with thin interlayers [PMMA] mounted on RHA. In these test the resistance of AiN compared to RHAe [~400BHN]was tested ....these targets had plate diameters to the subscale penetrator diameters of 9:1 to 14:1, which is very close to what I believe the approxiamte ceramic dimensions are in modern tanks armor.

 

In the tests the reference RHAe penetration was 90mm while the block of AiN resistance was 0.98 Te [thickness effectiveness]. That means 10cm of AiN could be expected to offer the equivellent of 98mm RHA. When the same thickness of ceramic was divided into thinner plates [change t/d from 7:1 to 0.6:1]. The resistance went from 0.98 Te to 0.9 showing that large reduction in t/d reduces resistance only by 9%. When the same target had thin plexiglas sheets added inbetween each of the 12 thin ceramic plates, the resistance was reduced to 0.86 T/d.

 

This is a reduction of 12%, but with the dilution of the target with lower density interlayers [ 3.26g/cc for AiN & 1.2g/cc for PMMA], the effective resistance over all didn't change much.Because thicker over all array could be constructed with the same armor mass.

 

If 10cm of steel mass was devoted to the insert effectives, a straight AiN insert would amount to 24cm thick, with a overall KE resistance of ~23.6cm RHAe. If the same armor mass was devoted to a AiN /Plexiglas multi layered target [2.98 g/cc average density], then the array thickness increases to 26cm .The effectiveness over all is reduced to 22.6cm RHAe...this is a reduction in resistance to ~96%.

 

So why is this practice reported to be done? Firstly the paper reports that constructing ceramics in blocks thick enough for heavy tank targets is very expensice. If the same thickness was composed of thinner plates this would reduce cost considerably. Since armor is secondary to firepower/FCS cost , this is not a small consideration.

 

In addition these targets where struck at normal impact angles, at angle the resistance may improve. In a paper from the institute @ Chobham [Hohler etal int.J.Impact Engng Vol-26 , pp 333-344] , layered ceramic targets @ 0° & 60° showed that atleast for subscale models, the @ 60° layered ceramic [Alumina AD-97] steel target resistance was higher than the same LOS target thickness @ 0° impact angle. In otherwards something in the layering at angle helps to defeat long rod penetrators.

 

However there may be another reason why multilayers with interlayers is practiced ,because it improves shaped charge resistance.

 

In a paper by Hornemann & Holzwarth [int.J.Impact Engng Vol 20,pp375-386], various layered ceramic steel targets where fired on by 5cm subscale shaped charge warheads .In these tests at normal impact angle the reference penetration into RHA was 216mm while the optimum ceramic [AD-92]/steel resistance was 116mm suggesting an overall Te of 1.8 RHAe. Another target was the same construction with a rubber layer inbetween each ceramic tile [ ratio 1 rubber to 6 ceramic , similar to the AiN tests mentioned above].In this target the resistance worked out to 1.73 Te [125mm].The cross sectional density of the two different arrays was 3.5g/cc and 3.2g/cc, thus if we had 10cm of steel mass for an insert the straight AD-92 target could offer 22cm ceramic thickness for an effectiveness of ~40cm RHAe. The Ceramic Rubber target should have a thickness of 24cm and an effectiveness of ~42cm RHAe.Thats about a 5% improvement in resistance.

[Tyler Durden]

Tired. Had hoped to get Prof Minin’s article on the problems with spin stabilised projectiles finished tonight but don't know if I'll get the chance. Later

 

TD

 

Oh yeah, the "Grid against the projectile article" translation is finished.

 

 

 

 

[Edited by Tyler Durden (24 Jun 2002).]

[Tyler Durden]

...

[Paul Lakowski]

Originally posted by Tyler Durden:

Tired. Had hoped to get Prof Minin’s article on the problems with spin stabilised projectiles finished tonight but don't know if I'll get the chance. Later

 

TD

 

Oh yeah, the "Grid against the projectile article" translation is finished.

 

 

[Edited by Tyler Durden (24 Jun 2002).]

 

 

I'd like to see the translation of that...can you Email it to me at

 

stl@telus.net

 

Thanks for now!

[Tyler Durden]

yup, when I get it done. Later. Now MUST SLEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP........................

[Paul Lakowski]

OK heres a tentative simplistic analysis of how MEXAS armor may get the absurdly high shaped charge resistance values.....

 

MEXAS density is ~1.7g/cc and reactive elements are reported in the construction with a strenght of 2.5 GPa, not many materials are that strong but Boron Carbide could fit the bill.

B4C has a mass of 2.55g/cc and ME vs shaped charges of ~ 4.0...leading to a space effectiveness of ~ 1.3.

 

Now a mixture of CaCO/GAP and B4C should have a density of 1.7-1.8 g/cc [2.55g/cc+1.0g/cc ÷2]. Some thing with the density of CaCO/Gap should have an effectiveness of ~ 0.7 [space effectiveness] so a average of B4C & CaCO/GAP should be ~ 1.0 spaced effectiveness...

 

The ME should be 7.83/1.7= 4.6.

 

But the CaCO/GAP is reactive and generates a considerable improvement in effectivenes because this reactive forces the steel plates apart...using the VM-11 paper as a guide the ME of steel foam is ~ 3.3 while the value for steel CaCO/GAP is ~ 10.0...meaning this reactivity tripled the effectiveness of the sandwich...

 

If this same reactivity is applied to the above B4C & CaCO/GAP sandwich we end up with ~ 14:1 Me.

 

Now in this paper there were reactive elements that were tested with thin explosive layers to enhance the bulging effect on the outer steel plates...these ranged from 4-6 times the base values and if these super reactive forces are applied to the MEXAS model thats 4.6 x 4-6 or ME of 18:1 -28:1.

 

The paper showed that MEXAS @ 15° offers as much protection as ERA @ 60-70°. If you take Blazer this is two 2-3mm steel plates and a couple of mm of explosives [density ~ 1.8g/cc?]...any way thats ~ 6mm steel mass @ 60-70° or 12-18mm steel...the ME of these ERAs are reported to be ~ 20:1 meaning this resistance is ~ 240-350mm. Thus MEXAS with a steel mass of ~ 7mm is as effective as >250mm RHAe or a ME of 36:1!!!!

 

Heres the crunch...studies of bulging plates show that plate speed is the key. Well if the above chemical reactive forces can 'bulge' a plate sufficently to tripple quadruple its effectiveness , image how effective they would be on a small ceramic [b4C ]nugget? Rosenberg and Dekel wrote several papers on the parameters of this bulging prossess...it was clear that if you increases the interlayer or reduced the thickness of the outer steel plate [mass], the plate bulging velocity shot up [going from 200-800m/s in some cases].

 

Could be that instead of tripple its 6-8 times the ME against shaped charges? That would be an ME of ~ 32-37 .

 

KE resistance would suck...incomparison but it could still be overall very effective against small diameter projectiles....

 

anyway just a theory at this point

 

[Edited by Paul Lakowski (28 Jan 2003).]

[Przezdzieblo]

I just found this veeery old thread. It might be interesting which ideas said here are still fresh today.

 

But, this kind of archeology I made not without reason.

See this please -->

http://img149.imageshack.us/my.php?image=armorfy2.png

I was said that this is old (pre-Chobham?) American project of armour (probably anti-HEAT). Any other informations? Comments? Ideas? How could it work, just spaced armour?