The time has come for the theoretically final article in this series. He was BDD, was ERAWA in 2 installments, was CERAWA, and was now to discuss possibly the least known armor from the full set. I have been reasoning about dividing this article into 2 parts, but many issues are so linked that I request to discuss this full subject here. The main character of this article will be the CAWA ceramic armor family, which, like the erstwhile heroes, was created in the 1990s at the Military Institute of Weapons Technology.
CAWA-1 The first kind of ceramic armour developed is CAWA-1. It was created from a single layer of ceramic tiles with a foundation in the form of armored steel, or aramid fabric, acting as a spall lineer. The task of this armor was to defend vehicles lightly armoured against anti-tank firearm ammunition. However, in order to find what is best for armor for light armored vehicles, it was decided to compare the following ceramic materials as armor: - aluminium oxide (Al2O3; besides known as corundum and alumina; density 3.73 g/cm^3), - silicon carbide (SiC; carborund; 3.2 g/cm^3), - boron carbide (B4C; borocarbide; 2.39 g/cm^3), - Titanium silicon carbide (Ti3SiC2; 4.46 g/cm^3),
The requirements set before CAWA-1 were: - protection of the object from firearm ammunition up to and including 14.5 mm (depending on thickness) during shelling at a minimum distance of 100-200 meters - protection of the vehicle against ignition agents - anticipation of mounting additional armor layer on ceramics, including reactive armor ERAWA - anticipation of applying a microwave absorber with paint - advanced adhesion of the base armor tiles in order to avoid abrasions - ease of production, assembly and operation - maintaining its strength parameters in a minimum of 97% of cases with: 1) air humidity up to 98% 2) air temperature from -60 to +70° C 3) the impact of reduced atmospheric pressure, single mechanical strokes, magnetic field, electrical field, electromagnetic radiation, static electricity and lightning discharges, 4) underwater at a depth of up to 5 metres for a minimum hour 5. for an operating period of at least 15 years with water protection and corrosion The tests carried out on the ceramic types afraid respective stages, in which for the most reliable results were shot at each example from 3 to 10 times. The first test was the protective capabilities against a 7.62 mm B-32 armoured rocket utilizing a 10 mm thick armored steel plate as a substrate for ceramics. The results showed that the best protection was provided by plates made of 8 mm Al2O3 and 7 mm Ti3SiC2 thickness - for comparison besides tested SiC tiles accomplish the assumed possibilities at 12 - 20 mm thickness. Given their density, the mass to surface ratio was: - 29.84 kg/m^2 for Al2O3, - 31.36 kg/m^2 for Ti3SiC2 - 38,4 - 64 kg/m^2 for SiC Theoretically speaking, the best consequence was shown for alumina, but for this test the value for titanium-silicon carbide proved to be small worse (the armor thickness is 12.5% lower with a higher weight of 5.1%). Another test was very similar, but the only difference was to defend the armor from anti-tank ammunition. 12.7 mm. There the comparative possibilities supplemented by the Borocarbide mentioned at the very beginning. The results proved to be the best for Al2O3 again - the ceramic plate made of this oxide provided protection against these missiles already at 10 - 12 mm thick. For comparison for SiC and Ti3SiC2 it was 20 mm and for B4C - 24 mm. With 14.5 mm ammunition, the tests were limited only to plates made of Al2O3, and the results showed that full protection against these missiles provides armor of at least 18 mm thickness. The gabarite origin was 1.7, while the mass origin was 3.44. Also on the occasion of the ammunition of this caliber, the impact of substrate thickness (steel base armor) on the protective capabilities of ceramics was checked. And it has been shown that the substrate importantly affects protective capabilities - for a plate with a thickness of 13,5 mm, 8 mm of ceramics is adequate to avoid full penetration, and for a plate of 8 mm it already needs 15 mm of Al2O3. In addition, taking into account the usage of 15 mm thick plates, for RHA plates of thickness: - I'm sorry. 8 mm - only to avoid armor perforation, - 10.5 mm - the depth of the crater after the bullet is 5 mm - 13,5 mm - crater depth is 1 mm However, for an angle of 60 degrees it is possible to avoid perforation with plates of 4 mm thickness (h = 10,5 and 13,5 mm) or 6 mm (h = 8 mm), and for plates of 8 mm thickness, for an RHA plate of: - 8 mm - 7 mm depth of the crater - 10,5 mm - 2 mm - 13,5 mm - 1,5 mm It follows that the minimum thickness of steel armour, at which ceramics begin to execute their task well, should be 10 mm. In conclusion, CAWA-1 has been shown to the mass and thickness efficiency ratios were 2.6 and 1.25 for Al2O3 and 1.95 and 1.12 for Ti3SiC2 respectively. This means that the ceramic armor (made of alumina in this case) is 2.6 times lighter and 1.25 times thinner than the armor made of armoured steel at an equivalent level of protection. In the case of 12,7 mm ammunition protection, the coefficients for alumina were as advanced as 4 and 2 respectively. CAWA-2 Another aspect of the ceramics acting as armour was the protection of primary tanks against anti-tank ammunition, both kinetic and explosive. At the time (as now) our armored troops were based on the T-72 tank, which utilized glass textolite and silicon oxide cartridge as peculiar cartridges. Glass fibre is simply a laminate composite, which is obtained by pressing at advanced temperature glass fibre layers soaked with resin (probably phenolic). In the 1960s, this material as an component of the armor was a complete novum, but due to mediocre characteristics of glass fibre and the advancement of material engineering in the usage of non-ferrous materials in the armor, this material rapidly became inefficient. And for this reason, the investigation facility became a multi-layer ceramic armor, known as CAWA-2. The literature available at the time recommended utilizing two-layer ceramic models in thick armor, consisting of either 2 layers of SiC, or a layer of alumina and a layer of zirconium oxide behind it, which were depreciated by a layer of polymer or aramid fabric, whose task was to capture fragments formed by crushing ceramic tiles. Another option was to usage multilayer systems, where the first layer was aluminium oxide, and the next layer included another ceramics. However, on the basis of the work on CAWA-2, it can be concluded that it was decided to take a small different path. It cannot be ruled out that it utilized a multiplicity slide from 2 layers of different ceramic materials, with the first layer having to be advanced hardness ceramics and the second - soft ceramics (i.e. low hardness). But why did armor should be so made? It was assumed that the task of the first layer, made of hard ceramics, was to destruct a bullet penetrating the armor, and the second layer (soft ceramics) was to halt the deformed bullet. For this reason, a combination of the advantages of alumina and silicon carbide or zirconium oxide was considered to be a kind of "opus magnum". In the course of the studies, another equally good soft ceramic material was found to be titanium-silicon carbide (Ti3SiC2), but it is not produced so far in quantities allowing its usage for a intent another than laboratory tests. But will individual come up with a new, much more effective composition of layered ceramic armor? We'll see.
The essence of ceramic armour - layered and gradient
Returning to the subject, another crucial aspect is the value of wave impedance of utilized materials, due to the fact that the greater the differences between materials, the penetration tends to lose kinetic energy while passing between layers of armor, which can be observed by observing "fungals" in the penetration crater. It is so crucial to alternate the usage of different materials in the layered armor. In addition, during the research, it was shown that layered ceramic armor is much little heated and is better cooled than monolithic armor - steel or ceramic. This plays a very crucial function in protecting the armor from multiple hits, where the advanced temperature of the working armor has a affirmative impact on the penetration of the anti-tank rocket (i.e. detrimental to the defender). However, by the way, it is not a secret that ceramics is simply a good thermal insulator, which WITU utilized in the reactive armor of ERAWA. As a result, Polish armor in contrast to Soviet, Russian and Ukrainian solutions is much little delicate to the operation of tandem precursors of accumulation heads, as well as to any shrapnel-storming missiles. The CAWA-2 was designed specifically to service as a peculiar contribution to the armor of essential primary tanks - in this case it was associated with the plan of the PT-97 tank planned by the Mechanical Swans, to be the final modernization of the hard Tanks, as well as to implement in the Polish MBT III generation task named Goryl and Gepard (not to be confused with the later 35-toner). For this purpose, the additional request was placed before the CAWA-2 another than those corresponding to the CAWA-1 requirements. tank protection against kinetic anti-tank missiles up to 550-600 mm RHA (cal. 105 - 125 mm ammunition) and before HEAT ammunition with a breakthrough of up to 1000 mm RHA. On the another hand, it was specified that erstwhile assembling the CAWA-2 as a basic MBT armor, the first steel layer should have a hardness of min. 500 HB and the bulkheads in which the ceramic armor would be placed should have a hardness of approx. 300 HB.
Concept of layered ceramic armour by Adam Wiśniewski, 1992 Ceramic tiles in respective layers were to be included in welded (a) or cast (b) cassettes to stiffen the armor. It is very likely that this was constructed (at least initially) CAWA-2
As a consequence of further work, the ceramic part is to be composed of respective layers of tiles with a thickness of 20 mm. Why would they be so thin? This is where the way in which ceramic armor works plays a major role. As shortly as the bullet makes contact with armored ceramics, the tiles begin to crack. But cracking is not contrary to immediate appearances - the time between the beginning of the penetration process and the beginning of the cracking process is counted in microseconds. As shown experimentally, as the ceramics begin to crack, its protective properties begin to drop drastically with time. Therefore, the aim of technology is to make specified tiles that do not start to break before they are completely penetrated by a projectile or completely penetrated may happen in a tiny period of time from the beginning of the ceramic tile crushing. In order to find out erstwhile the plate will crack, you request to know the 3 main components responsible: - size of ceramic plate (less dimension or width of tiles is most important) - the value of sound velocity in ceramic tile material - the velocity at which the bullet hits the ceramic plate The problem is to optimize the size of ceramic tiles. besides tiny a plate will start to break besides rapidly as a bullet hits. The besides large plate will cover besides much surface while its protective capabilities will be weakened immediately after the first hit. And both have a negative effect on the capabilities of ceramic armor. As shown during the tests in 2005, it is if a plate of dimensions 50 x 50 mm shows average thickness efficiency at the level 1,565, so much a plate with dimensions 100 x 100 mm of the same thickness (i.e. 10 mm) ensures efficiency at the level 1,679, which means an increase by 7.3%. The second measured parameter was the depth of the bulge of the steel plate, which is the basis for ceramic cubes - in tiles 50 x 50 mean 4,08 mmand for platelets 100 x 100 was it 0,59 mm. At the same time with tiles 50 x 50 In 6 out of 22 Tested ankles were perforated with armor, which meant that the required tasks - for comparison in the case of tiles 100 x 100 It just happened. one specified case (on 21 the test ankles), precisely in a plate made of material worst parameters. In addition, it is crucial to arrange individual layers of ceramic tiles "on the tab". In the case of linear arrangement in the armor, places would appear weakened in the spaces between ceramic plates, and in specified places the protective capabilities of the armor could fall even by 30%.
But CAWA-2 does not request to be utilized exclusively as a peculiar cartridge in the basic armor of MBT, but it could besides be utilized (similar to CAWA-1) as a easy disassembled additional armor. And 3 different ideas were patented for the construction of additional armor cassettes, specified as CAWA-2 The first thought is patent PL 181177 B1 of September 10, 1996, which was notified by WITU.
Within its framework, the armor was to be 1 cassette, closely adjacent to the armor, which consisted of 5 layers. The first and last layer of armor was the steel case of the cassette, inside which were 2 layers of ceramics, and the space between the housing and the first layer of ceramics was filled with material, a mixture of fine ceramic elements, advanced strength concrete and glue. This material was utilized in the armor to fill the gaps, and thus to stiffen the armor structure, preventing the ability to decision ceramic layers, while improving the opposition of cartridges to bullet hits. On the another hand, the issue of combining cassettes from the armor of the main combat car was not full resolved in order to stick the surface of the outer cassettes and armor to each another - the authors proposed 4 solutions on this issue: - the first was to combine cassettes utilizing the tenicas, acting as guides. - the second was the usage of a perforated plate, located between the cassette and the base armor and connecting the cassettes with the plate utilizing screws - the 3rd was a tape clamp utilizing anglers - the 4th was the usage of brackets attached to cartridges and basic armor The second thought is the patent PL 183721 B1 of September 26, 1997, which was notified by the AGH University. In this case, the thought of creating cassettes was decided to be akin to that already discussed in the series of reactive armor ERAWA.
Compared to the erstwhile option, the large advantage is to facilitate the production process of cassettes by replicating the ERAWA armor structure. In order for the CAWA-2 cassette to be dimensionally and structurally as close as possible to its explosive equivalent, the housing would gotta have the same size and plan (dimensions 150 x 150 x 46 mm; made of steel panels with a thickness of 5 mm and a hardness of 500 HB) and should be fitted to the base armor with identical coils 30 - 50 mm from the surface. At the same time, in order to reduce the cost of production besides of ceramic elements, it would be desirable to usage ceramic layers of a thickness akin to those utilized in CAWA-1 and CAWA-2 as a contribution of peculiar basic armour. For this reason, the thickness of a single layer of ceramic tiles recommended by the designers was between 8 and 20 mm. However, it can be seen that the CAWA-2 cassette is much larger than ERAWA-2 - its likely dimensions according to the graphics are 250 x 250 x 33 mm, while the ceramic layer is 20 mm thick in total. However, since this is just a visual drawing that is expected to describe only the construction of a cassette, it would not be a problem to make cassettes measuring both 150 x 150 x 46 mm and larger with dimensions ~300 x ~300 x 46 mm so that there are no problems with their usage in place of the ERAWA armor. An additional advantage of CAWA-2 in cassette form is the anticipation to combine them with layers (authors provided for the anticipation to usage up to 3 layers of cassettes) and to mount reactive armor on them. As a result, CAWA-2 could drastically increase the protective capabilities of an armored car, with limitations lying solely on the side of the armored vehicle. Nor can it be excluded that already at that time it was proposed to usage much larger armour modules, as is presently utilized in modern combat vehicles The 3rd thought comes from patent PL 178940 B1 and it is actually closely related to CERAWA-1 reactive-composite armor.
A cassette of this type, unlike others, can be considered modular as it was designed to be capable of fitting ERAWA, CERAWA and CAWA cubes. In addition, as you can see, it was mounted differently to the base armor than the classical cubes, so that the additional armor could be tilted, and at the same time increased its effective thickness, even on a vertical armor plate. Moving on, the conventional component of armor work was its endurance tests on the subject APFSDS ammunition protection. The request included protection against 125 mm projectile with a penetration of 550 mm RHA, and most likely the Israeli M711 (produced later in a tiny batch in Poland and besides known as Pronit and Ryś). These tests were carried out on the CAWA-2 armor between 1994 and 1997. 3 1000 x 700 x 230 mm armour models were prepared for them, where the top steel layer was bolted to the remainder of the 10 M20 model. The composition of these models is officially unknown, but on the basis of residual data it can be concluded that a composition consisting of 60 mm RHA, six layers of ceramics of 20 mm thickness, each, alternately utilizing aluminium oxide and silicon carbide, the last layer being a 50 mm RHA plate. Additionally, these models were planted on a witness-plate made of RHA measuring 1000 x 1000 x 100 mm. The full was tilted at an angle of 60°. The results are as follows:
Why is there specified a difference in measurements between models 1 and models 2 and 3? Well, model No. 1 was constructed differently from the another 2 models by utilizing dorsal joints to combine armored plates alternatively than groin joints, as was the case in models No. 2 and 3. However, the results of the CAWA-2 armor tests do not reflect 100% of the possibilities he could give for T-72. This is most likely due to a different composition of armor compared to what would have gone to MBT, as well as the fact that for the reliability of tests the models were tilted at an angle of 60° alternatively than 68° as in russian tanks. In addition, the tested CAWA-2 armour models were not suitable for immediate usage in tank armor. In order for this to be possible, it was essential to adjust the armor to the size, the ability to defend against multiple hits and the safety of the crew inside the vehicle. But on the another hand, on the basis of the tests, the theoretical protective capabilities of CAWA-2 in the additional armor version (cage variety). Taking into account the mass and gabarite ratios mentioned above and assuming that my armor composition is true, it means that the two-layer ceramic armour cartridge itself can supply protection of about 105 mm RHA at an angle of 60°. And given the impact of the armor leaning on the bullet's penetration, this can be equivalent to 65 mm RHA at right angles or 130 mm RHA at 68°, which is simply a decent value. PT-91M Pendecar In 1998 (later) the proposal to usage the CAWA-2 armor was revealed as part of the later modernization of PT-91 hard Tanks. Initially, the replacement of the armor was intended to concern the hull only, where as much as 5 layers of ceramic armor were proposed to be utilized alternatively of 2 layers of textolite. Due to the fact that the problem of replacing cartridges in the cast tower (which is not technically possible) was not proposed, the CAWA-2 armor was most likely not utilized in Polish PT-91 Tough, although there is no 100% certainty. On the another hand, unofficial sources indicate that almost surely this armor was utilized in the production of fresh hard copies for the Malaysian army, besides known as PT-91M Pendecar. Tough with the same armor was besides offered at least for Peru and Colombia nearly 10 years ago. It was not officially revealed what the hull's front armor and Pendecar's tower were made of, but based on the available information on both CAWA-2 and T-72M1, it is possible to fishy that 100% ceramic armor was placed in the Malaja's hull, but is not so certain about its tower, where most sources keep sand cartridges. On the basis of the information available, it can be estimated that the effective thickness of the T-72 front fuselage with CAWA-2 cartridges may be between 600 and 700 mm RHA against APFSDS ammunition, with the most likely (although I think a small overstated) value being 670 mm RHA. However, these are only my guesses based on the data that were the origin for this article, so I would not regulation out that they will be false after all. On the another hand, 1 must regret that in 1989 we did not buy from the Soviets a licence for T-72S (export variant T-72B), which they offered us. The modernization possible of Object 172M-E8 is much greater than what the Object 172M-E5 proposes, due to the fact that the armor cartridges of a peculiar tower are flooded with steel during the tower casting process, while in T-72S these cartridges are welded to the already cast tower. The effect is that if you want to exchange armor cartridges in T-72M1, then you request to replace the full tower, while in T-72S you just request to remove the welds connecting the cartridges with the remainder of the tower. Summary It can be noted that all of the material engineering active in the improvement of non-ferrous armour is working on solutions that would not be limited to the armoring of primary tanks, but besides the effects of this work may besides be utilized to defend lighter military vehicles, solid reinforcements, as well as the protection of individual soldiers. The ceramics I discussed here are perfect for all the mentioned solutions and can sometimes take over most of the work for protecting a given object from iron alloys. And that's what CAWA shows. Its improvement has been targeted 3 ways - the protection of light and average armored vehicles as additional armour, the protection of non-armoured vehicles with akin construction and the protection of heavy armoured vehicles as both the main component and the additional component of the armor. This enabled ceramic tiles to service as both PT-91M armour and armored infantry vehicles (BWP-1, KTO Rosomak, KTO Ryś and others) or unarmoured (propellers). However, the problem is that investigation into the improvement of materials under defence applications should proceed and make any effects. Meanwhile, investigation and improvement funds are frequently insufficient, which means that investigation or may become abandoned due to under-financing of the task (example is the Polish ASOP project), and the effects of the existing work can be lost or the investigation can be slow enough, that abroad competition starts to "run" from us with technological improvement of the product. And in the end, it's either a mockery of a home product or a complete oblivion. At present, however, it is essential to support another Polish composite armor, which contains, among another things, ceramic elements and which will form the main component of the combat armor of the Borsuk infantry vehicles. But it will be mentioned in another article. Bibliography Adam Wiśniewski, Pancers: construction, plan and research. Warsaw 2001 Adam Wiśniewski, Ceramic materials in protective layers, Green 1998 - Wojciech Łukasik, Protection properties of large corundum ceramics: doctoral dissertation, Kraków 2005 - Michał Łopaciński, Jerzy Lis, Gradient ceramic layer materials for anti-balistic applications, Poland Ceramics 2002: materials of the second global conference Spala 20-22 May 2002, pp. 342-349, Kraków 2002 Adam Wiśniewski, Single layer and multilayer ceramic panel, Polish Ceramic Bulletin No 3, pp. 255-261, Kraków 1992
