Talk:Chobham armour

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[edit] Perforated Armour

Can someone provide some information on what "perforated armour" is? I did a quick search and found nothing particularly enlightening. Currently the link just redirects to the vehicle armour page, which has no mention of it. Bobbis 16:48, 21 Apr 2005 (UTC)

Well, in fact it has :o). But to state the obvious: perforated armour is just that: armour with perforations. To understand the principle applied in its simplest form, imagine a block of steel with perpendicular holes drilled into it, that are smaller in diameter than the penetrator hitting it. If the penetrator hits the area between the holes it has to penetrate the whole of the thickness of the plate - that plate of course being a lot thicker for the same weight now that it has perforations in it. If it hits the edge of the perforation the penetrator will tip, deform or (hopefully) snap. That's one penetrator that won't penetrate. If it snags into the perforation the abrasion will be terrible. And abrasion provides 60% of the protective qualities of any armour even during a normal impact.
Instead of drilling holes into a steel plate you can create a similar structure with perpendicular uranium or tungsten rods, bundled together. Cold tungsten is rather brittle so you'd have to encase it in e.g. titanium tubes.
This is only the principle at its most simple. The protective qualities can be significantly improved by applying materials of different hardness and toughness and by using an advanced topology optimised for the expected penetrator. A remarkable advantage of perforated armour compared to Chobham armour is its vastly superior "multiple hit capability" (i.e. sustainability). When modern perforated armour is hit there's at first a build-up of protection: the addition to the protective mass by the deformed penetrators is at first more important than the loss of structural cohesion! If you keep hitting a Leopard 2A4's frontal armour with a T-80 you'll run out of sabot rounds long before the Leo 2 is knocked out. That's very satisfying from the point of view of the Leopard 2 crew. However if an original M1 was hit by a T-64, after the second hit on the same module its crew was (un)protected by a heap of expensive rubble, only good to make toothpaste from (it's the same stuff).
Perforated armour can also be used to protect LAV's against bullets, but then the thin armour plates have to be really optimised for the bullet calibre.

--MWAK 15:51, 24 Apr 2005 (UTC)

This sounds very much like "spaced armor" from the 1960s, actually.
Indeed such systems were then in development and the principles were implemented in the Leopard 1A3 and A4, the A1A1 in the Mittel and Schwer configuration, as well as the French AMX-32 and 40. These types were therefore much better protected than is often assumed (well, their turrets...). Much what has been described as "spaced" is not of a simple laminate type as would be suggested. --MWAK 09:56, 4 December 2005 (UTC)

http://www.ciar.org/ttk/mbt/papers/ijie01/ijie_25_423.pdf is an interesting paper that looks at the effect of projectiles striking the edge of armour plates. MWAK do you have any references discussing the build-up effect or the composition of Chobham? It might be nice to add a perforated Armour article, or at least add something to Vehicle armour Megapixie 03:56, 13 July 2005 (UTC)

There are no unclassified papers on the build-up phemomenon (which is a freak effect anyway); so it's better not to put it in the article :o). The International Journal of Impact Engineering is an excellent source in general. Also the American Ceramics Society (it sounds so innocent doesn't it? But it isn't all about pottery ;o) can give a lot of information. See e.g. http://www.ceramics.org/meetings/cocoabeach2004/armor.asp. Relevant to the article is especially this abstract:
The drive to develop armor systems for combat vehicles requires improvements in the bonding of ceramic armor to metallic substructures. Current methods that utilize epoxy adhesives provide limited strength and ballistic performance. Reactive multilayer joining offers the novel ability to form strong metallic joints between ceramic tiles and metallic plates at room temperature. Reactive NanoTechnologies’ novel joining technology is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano-engineered materials, in which self-propagating exothermic reactions can be initiated at room temperature with a spark, laser or hot filament. By inserting a multilayer foil between two solder or braze layers and two components, heat generated by the reaction in the foil melts the solder and consequently bonds the components. The joining process can be completed in air, argon or vacuum in approximately one second. The use of reactive foils as a local heat source for soldering or brazing eliminates the need for furnaces, speeds up the joining process, and dramatically reduces the total heat that is needed. Most importantly the limited heating of the components virtually eliminates the mismatch in thermal contraction that normally occurs on cooling from soldering or brazing temperatures. Thus large thermal stresses are avoided and large area samples can be bonded. This presentation will begin with a description of the multilayer foils and their use as local heat sources in soldering and brazing. We will then demonstrate their utility in the bonding of two ceramic armor systems, Al2O3/Al and SiC/Ti 6-4. For each of these systems we will first show numerical predictions and IR measurements of heat [t]ransfer. Then we will present shear strength measurements for the joints. The strengths achieved range from 30 to 80 MPa, and are limited by failure in the braze or solder. Finally examples of large scale reactive joints for each of these material combinations will be shown.
It's a public secret that in the late seventies the British used boron carbide and the Americans alumina. Stone age technology by today's standards of course :o). The last ten years, in a desperate effort to lower costs enough to equip even LAV's with an effective protection against RPG's, the USA has tried to mobilise the world's research sources. This could only be done by being less strict about security. Especially through the SBIR-program much has been revealed, among which the fact that silicon carbide is used in vehicle armour. http://www.dtic.mil/matris/sbir/ should be most interesting! Particularly http://www.dtic.mil/dticasd/sbir/sbir012/sba39.html
Should you doubt the claims in the article about recent protection levels: see http://www.fprado.com/armorsite/US-Field-Manuals/abrams-oif.pdf on page 7.

--MWAK 09:11, 13 July 2005 (UTC)

All good stuff.

I've seen some estimates of the M1's protection levels on a couple of forums

But a Chinese webpage isn't exactly the most reliable of sources.

The pages on armour are very fragmented (no pun intended). I thought it might be good to re-structure some of it - i.e. a page on each armour type and a main page with summaries linking off to the other pages. The problem is that it's hard to get a concrete references. I'm currently getting side tracked working on Soviet and early western ATGM's - see AT-3 Sagger,Entac ....

Do you think it would be worthwhile re-organising the pages? It's probably going to take me a couple of weeks at least to finish up the ATGM's - but after that I wouldn't mind helping out.

Megapixie 12:44, 14 July 2005 (UTC)

Allow me to comment. :o)
  1. The first diagram has the principle right: the original M1 armour consisted of three main sections: an outer thinner steel plate; a thicker steel back plate — and in between the alumina (Al2O3). However it pretends to give exact numbers. It fails because it is based on a complete misunderstanding of CMC's. It shows no matrix, no vibration absorber, no oxygen absorber and no expansion space. In fact it reminds me of nothing so much as Wilkins original work of over forty years ago, as if all you needed was some massive Magical Crystal. Such a configuration would literally self-destruct. It also fails to understand the fundamentally modular nature of the system.
  2. The first column of armour equivalence estimates is correct. No wonder: it's the official one. The numbers for the M1A1 and M1A2 are ridiculous underestimations though, unless those of the M1A1 are interpreted as indicating the equivalence of a double silicon carbide matrix, without uranium module. Then you would have a lot of empty space left; a single matrix has a thickness, according to the original SBIR discussion (later partially deleted in the archives :o), of four centimetres. The numbers in the Team Abrams presentation are inches, not feet: a RPG with a nominal penetration of 360 mm steel caused only a hole of about 30 mm deep! Such is the superior quality of the American "eumorphed" silicon carbide composites, so much better than the industrial-grade junk Soviet engineers had to work with. There should be space enough to protect the tank with an equivalence of over a metre against KE and almost double that against HEAT and still remain within a weight limit ensuring 80% reliability (if you have a good maintenance team). Newer composites are in development improving toughness through the use of nanotubes; these should make it possible for the CMC's to really contribute to KE-protection. At present no actually bought KE-rounds can penetrate the M1's frontal armour in its heavy configuration.
  3. However, as said, the system is modular; it's up to the theatre commander to decide what the general threat level is, whether strategic mobility demands outweigh the need for protection. I've been told base commanders often remove the CMC's completely to reduce costs by putting them in protected storage, at the same time reducing general maintenance and fuel use. This would then be the origin of the story that the tank "rings hollow" if hit with a hammer. Certainly it seems to be the cause of the heavy suspension damage during the Iraq invasion; drivers made jumps that would have caused no trouble for the unloaded vehicles they were used to, but now destroyed the suspension elements.
  4. Speaking about ATGW's (nice work you've done!), it should be noted that the penetration of a hollow charge does in fact not scale linearly with its diameter: heavy missiles are a lot more dangerous than is often presumed. So that's the bad news. :o)
And now about the article structure. As it is now, it isn't too bad. Vehicle armour can be used as a sort of general introduction — and we need one, I feel: remember that for most people, especially those of the female persuasion, all this is completely new and utterly confusing. It would indeed be very nice to have a special "Perforated armour" article; but, as you said, it's hard to get good references and it might be harder still to defend the validity of the article if challenged. As it is a subject people have strong opinions about (to say the least :o) perhaps it should be mentioned only in the context of Chobham. For "normal" steel armour we could use RHA and sloped armour. I often get the impression less attention should be given to all kinds of modern developments and more to the basics of ballistical protection, which the average tank enthusiast doesn't seem to understand at all :o).

--MWAK 15:14, 14 July 2005 (UTC)

On closer inspection I believe the Chinese table is an incorrect copy of a more original one with four columns, the second then giving data for the M1 Improved. This seems to be indicated by the wrong number for the weight increase. Many other data would make more sense if seen as estimates comparing the M1 Imp to the M1A1, rather than the M1A1 to the M1A2. It's also notable it's assumed the replacement ceramic is titaniumdiboride, apparently inspired by reports about the LAV-programme in the mid-eighties. It's certain titaniumdiboride modules were made, but their very high cost makes it doubtful the entire M1-fleet was refitted with them.--MWAK 18:11, 14 July 2005 (UTC)

Absolutely no scientific reasoning behind this article. Oh, and non of the M1 variants use Chobham as this is a British invention which has never been made available to them.

Is there not even a tiny bit of scientific reasoning present? ;>) Regarding your second claim: it all depends on what you call "Chobham". Since the early seventies there has been close cooperation between the British and the Americans in this field.--MWAK 09:35, 26 April 2007 (UTC)

[edit] An error?

" The effectiveness of Chobham armour was demonstrated in the first Gulf War, where no Coalition tank was destroyed by the obsolete Iraqi armor. "

I know this does not make sense, and I can think of no appropiate word to replace the second 'armour'. Perhaps someone would like to fix?

It sounds a bit silly :o). "Tanks" might well do.--MWAK 08:09, 7 February 2006 (UTC)

Or "ordnance". Gdr 22:22, 7 February 2006 (UTC)


"armor" is sometimes used as a shortened form of "mobile armor" (which is to say, tanks or other armored fighting vehicles). Here it is clear that the author meant Iraqi tanks. TTK 05:55, 8 March 2006 (UTC)
I forgot to thank you, once I discovered your contribution here, for the enormous amount of work you have done in the past to make available information about this subject to the larger public!--MWAK 20:42, 11 May 2006 (UTC)

[edit] Effect of sloped armor

The article seems to operate on the assumption that the only advantage to sloped armor is the chance of deflection. That's not the primary advantage. The advantage is simply that the steeper the angle of the hit, the more metal a penetrator has to through in order to breach the armor. As a rule of thumb, every 30 degrees off the perpendicular effectively doubles the amount of armor that has to be penetrated. And so while having flat-sided armor may be an advantage against HEAT rounds, it's a significant disadvantage against kinetic penetrators.

Well — aside from your rule of thumb, which is simply incorrect — you make the common mistake to forget that although angling implies that a longer stretch of armour has to be penetrated, this offers no weight advantage, simply because the angled armour plate has to be proportionally longer. See sloped armour.--MWAK 05:46, 24 September 2006 (UTC)

[edit] Chapter: "Effectiveness"..

Everything writen under here is false. 1st, armored vehicles and MBT's were lost in both 91 and 03 and to ATGM's, ROCKETs and Grenades and KE-weapons, including M1's and Challengers. Also this story about the punctured sideskirt M1 is bogus too, it was no tandem warhead, just your common PG-7VL or VM, and this with 330 -> 550 RHA penetration is far cry from the PG-7VR of which none of have ever been encountered in Iraq, infact only know use of this round has been from Checnya and even from there theres been just few photos of this in use.

Well, it's not the best section of the article ;o). The main point however is this: no existing RPG can easily penetrate the Chobham armour proper, i.e. the ceramic tiles. The silicon carbide composite used has a mass efficiency of over 25. A typical double layer configuration would have the equivalence of about 1000 RHA against hollow charges. A RPG-7, whether it has a tandem warhead or not (no, it will not "pre-shatter" the tile), will probably not penetrate even a single layer. But only a part of the vehicle is protected by Chobham.--MWAK 12:23, 11 November 2006 (UTC)
  • Only 1 Challenger2 has been destroyed......It was a "blue on blue" incident. —Preceding unsigned comment added by 86.129.37.181 (talk) 16:18, 8 October 2007 (UTC)

[edit] Pics/Diagrams?

Any pics or diagrams? I'm interested in seeing what this armor looks like/how it works. Maybe an animated GIF of a round penetrating and being deflected/disrupted by the armor? Shrumster 17:02, 30 January 2007 (UTC)

The pictures available are classified and/or copyrighted. The assemblage looks like what it is: a metal framework holding ceramic tiles. When there is a metal face plate, the entire assemblage looks like a metal plate. The heavy armour modules look like removable metal boxes, because they are contained in these. Should you open them, the topology then visible isn't easily described and strongly varies among types. Most published diagrams in the popular literature are rather simplistic and deceptive. Some are downright nonsensical. Especially the terms "layer" and "rod" have confused many artists, apparently not having got a clue how they should be interpreted :o). Anyone is invited to go to http://63.99.108.76/forums/index.php?s=5994548d9d786158a232a99ba6583369&showforum=8 and make a nice drawing of the typical penetration effects, basing himself on the pictures shown in the various pdfs made available through this site. --MWAK 08:35, 31 January 2007 (UTC)

[edit] Plastic Armour

Does anyone know if there is a relation to the second world war era Plastic armour, Chobham style armour can't have arrived out of no where and the earlier Plastic armour is similar in concept in being fine but tough granules kept in shape by a matrix. KTo288 13:59, 10 August 2007 (UTC)

It would indeed not be incorrect to say that Chobham is directlty derived from development lines started in the forties.--MWAK 17:27, 10 August 2007 (UTC)
Does that double negative mean yes?KTo288 09:58, 11 August 2007 (UTC)
Yes :o).--MWAK 18:24, 11 August 2007 (UTC)
ThanksKTo288 21:02, 11 August 2007 (UTC)

[edit] Rampant speculation

This article is full of opinion and random hypotheses which aren't sourced. Wikipedia is not a place to speculate on things. Chris Cunningham 17:39, 25 August 2007 (UTC)

Ah, you are communicating. Good ;o). Now to business: the accusation of original research is a very serious one and should not be lightly made. Are you very sure you have the expertise to correctly identify any "opinion and random hypotheses"? Obviously the article needs inline references — putting them in is simply a very time-consuming process, the main reason they aren't there — but most of the content is very basic. Could it be that you have concluded, after reading popular accounts that the composition of Chobham Armour is "classified", that the entire principle of ceramic armour is some great undisclosed mystery? This is far from true, I assure you. I will start adding references — obviously I've been waiting for this — but there will remain a narrative gap between the very technical papers and the implicit knowledge they assume any reader to possess already.--MWAK 18:36, 25 August 2007 (UTC)
Well, yes. The lack on inline citations is exacerbated by the use of phrase like "it is probable that". It's also quite chatty; that "bit of a mystery" thing should be removed, because how a hairdryer works is a "bit of a mystery" as well. Chris Cunningham 08:57, 26 August 2007 (UTC)
In that case we will increase the level of formality — and of course the process of adding citations is far from complete :o). I'm not sure what you mean with "chatty" exactly. As far as I can see there are no sentences without informative content present and the account is quite bone-dry as it is; but perhaps you're an engineer or physicist and correctly perceive that a more quantitative approach would be able to perfectly describe in a single formula what a thousand words fail to express. Should you want to add a quantitative analysis, this would of course be most welcome; nevertheless it should be remembered that most readers would be unable to understand it and need a purely qualitative treatment also.--MWAK 13:34, 26 August 2007 (UTC)
Well, put it this way: what does the phrase "the exact nature of the protection offered is sometimes presented as a bit of a mystery" add to the article? It's obviously not from a source ("The BBC reports that Iranian weapons researchers have declared the level of protect offered by Chobham armour to be 'a bit of a mystery'"), and it is also obviously not going to be much of a mystery after one reads the rest of the paragraph (which somewhat demystifies it), so it would seem that the clause is both irrelevant and unwanted. Removing it increases the sourced:unsourced ratio in the article.
The second problem (which is really the key one) is that things are constantly phrased as "could be" rather than "is". How something could be composed isn't what we should be discussing. Take this: "To minimise the effects of this the tiles could be made as small as possible, but then the ratio between the area covered by tiles and that covered by the matrix would become more unfavourable, also because the matrix elements cannot be reduced accordingly as they have a minimal practical thickness of about an inch. An equilibrium is usually found at a diameter of about ten centimetres." Why the build-up? Just say that the tiles are produced at 10cm because this is the best compromise. This speculative, arrive-at-a-conclusion phrasing is okay for key points in the article, but it's used all over the place. It's possible that the whole "protective qualities" section could be merged into the construction one after this is corrected because of all the duplication it causes through being separate. Chris Cunningham 14:04, 26 August 2007 (UTC)
There are several issues at stake here. Firstly we are not capable of giving a detailed sourced description of the properties of the actual Ceramic Composite Systems used in the respective MBTs of the world's armies, simply because most of the relevant sources have not been made public as yet. What we can do however is to give a sourced presentation of the present state of the art of ceramic armour in general, while abstaining from the claim that this state of the art is really applied in any actual western tank. Therefore we can only describe such systems as "typical" — given the known state of the art of present ceramic armour technology as reflected by the technical literature — and possibly applied.
Secondly, you are mistaken to call "arrive-at-a-conclusion phrasing" speculative. Speculation is the suggestion of facts; what the text does is to give the known design principles and then logically infere from them the conclusions (of course within a certain assumed factual context). This is far from redundant as neither the principles nor their deductions will be obvious to the average reader. If the text merely stated that tiles are 10 cm wide, the reader wil not be given the insight why this must be so. Why not a continuous ceramic layer covering an entire turret side? This was in fact the original intention for the MBT-70. And when the reader is told why — to prevent extensive damage by a single hit — he still would need to be told why in that case tiles shouldn't be made as small as possible. Might be obvious to you and me — but not to most. Of course we could condense the phrasing: "The typical tile size of 10 cm is a compromise between limitation of impact damage and optimising the tile-matrix framework ratio given a minimal one inch framework bar width". This is shorter and we both immediately understand what is meant. However, this is because we already are acquainted with the subject. To the reader it would probably be a bit of a mystery ;o).--MWAK 16:58, 26 August 2007 (UTC)
While I appreciate that this is a fascinating subject, this sort of thing is why WP:SYN was developed. Composite armour has its own article, and as this is an article for a specific type of composite armour it should refrain from using sources which don't actually refer to said armour to advance an argument. On the tile size thing, I'm coming round to your suggestion that it just needs to be made more concise. Chris Cunningham 08:00, 27 August 2007 (UTC)
Well, though the lead section as yet imperfectly reflects this, "Chobham armour" has of course become a generic term for "ceramic vehicle armour" in general. Should we limit ourselves to its strictest meaning, not even the M1 or Challenger 2 can be said to be fitted with Chobham armour in the narrow sense. Composite armour is a much wider concept so merging the two articles seems undesirable. Should we create a new article "Ceramic vehicle armour" we would be forced to begin this with "Ceramic vehicle armour, commonly known as Chobham armour..." — but if "Chobham armour" is the common name, it should in principle be the article title.
As the concept is general, I tried to give a general treatment of ceramic armour technology. I fail to understand what special argument I could be advancing by this. Obviously this would be different if Chobham armour were such a complete mystery that it would not even be certain that it was ceramic armour — for then the emphasis on this armour type would be biased. However, again the lead section is as yet incorrect: we have good official, public and published information on the basic properties of Chobham armour in the narrow sense.--MWAK 18:29, 27 August 2007 (UTC)
The intro edits are good. I'm going to de-tag this and see what else I can do to help out. Thanks for working so diligently on this. Chris Cunningham 08:44, 28 August 2007 (UTC)

[edit] Further work

No thanks. I'll continue being diligent by first of all adding the references you indicated as the most necessary :o). Your restructuring of the article is very reasonable; only I feel that it would be more "logical" to first give the general physical principles involved — in an expanded section — and only then present the structural properties. I'll also try and create a short "Development" section, as an introduction to the subject.--MWAK 10:56, 29 August 2007 (UTC)

"No thanks"?
I'm not sure that we can get away with explaining the protection factor first, again due to the angle of not trying to teach content. We should first describe, then explain things, rather than presenting the problem first. But no reason not to experiment!
The article's looking pretty nice now. Once it's got more inline citations, it can probably get graded as a good article. Chris Cunningham 12:01, 29 August 2007 (UTC)
Sorry, I didn't mean "No, thanks" but "No thanks are necessary". My germanic background got the better of me...I indeed have taught this subject in the past, so that could explain my educational approach of the matter :o).--MWAK 19:09, 29 August 2007 (UTC)

[edit] Reference formatting

Okay, we've got a lot of contextual referencing now. We should move to eliminating redundancy by having a References section containing the full description of the books being referenced (in proper cite tags) and a Footnotes section which contains the page numbers. I'll start doing this. Chris Cunningham 07:56, 4 September 2007 (UTC)

Very good idea! Thank you for your efforts; I myself tend to be a bit lazy and simply copy the whole for each footnote...--MWAK 07:13, 6 September 2007 (UTC)

[edit] Leopard 1 "glacis armour"

Such modules are also used by tanks not equipped with Chobham armour; an early less sophisticated steel version of such armour can be seen attached to the glacis of the German Leopard 1.

I'm removing this, until someone can find a reference. As far as I know, the only thing which can be seen attached to the Leopard's glacis is the metal racks for storing the track grousers, seen empty and loaded in the photos here.

I sure hope the article isn't full of other such tidbits. —Michael Z. 2007-10-03 22:58 Z


Yes, but the reason the track grousers have the shape they do and are attached at this particular place is that they can function as a primitive perforated armour system :o).--MWAK 07:42, 4 October 2007 (UTC)

[edit] Why an M1 Picture?

Since this is British armour I don't think that the only picture should be of an American tank! Why don't we put a picture of a Challenger 2 up there? —Preceding unsigned comment added by TechnoRat (talk • contribs) 17:26, 24 January 2008 (UTC)

Make that a Challenger 1, I would say :o). But again: it has become a generic name.--MWAK (talk) 08:08, 26 January 2008 (UTC)
Done. --Padijow (talk) 22:21, 13 May 2008 (UTC)