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My version of a tank uses reinforced depleted uranium as armor plating, however it was recently attacked by a large dragon which managed to crunch, and chew off a piece of it in one big bite.

What kind of material could allow the dragon tooth to penetrate into the tank's armor, and is it possible to duplicate the tooth using modern science? Think of Chobham armor.

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    $\begingroup$ Why depleted uranium in an armor, exactly? $\endgroup$ – Mołot Dec 17 '16 at 13:37
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    $\begingroup$ @Mołot Because it's heavy (helps against kinetic energy projectiles). But it's used in composites only as far as I know, with Uranium being the heavy part and something else supplying hardness. Are you using pure Uranium? Because other than being heavy, I don't think it has much advantage and can probably be pierced fairly easily. $\endgroup$ – Nobody Dec 17 '16 at 14:03
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    $\begingroup$ Depleted uranium is not what makes armor strong, as it has poor mechanical characteristics. Steel and ceramics give the armor its hardness and strength. Depleted Uranium is used in because of its high density gives it better ability to resist kinetic energy penetrators i.e. sabot rounds. Unless your dragon is firing its teeth into the tank at several times the speed of sound, the primary stresses it is putting on the tanks are the shear and crushing forces of its jaws. In that case, uranium is about as useful as butter compared to the high strength steels that encase it. $\endgroup$ – kingledion Dec 17 '16 at 14:37
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    $\begingroup$ I take it "unobtanium" or simply "dragon tooth enamel" is not an acceptable answer? $\endgroup$ – SRM - Reinstate Monica Dec 17 '16 at 15:43
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    $\begingroup$ Are we assuming that the tank doesn't have any possibly-very-dangerous-to-a-dragon explosive reactive armor? $\endgroup$ – Timpanus Dec 18 '16 at 13:34
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Before we get into teeth, note that your dragon will need some really, really strong muscles (and jaw bones) in order to take a bite out of a tank. Perhaps a "how could dragons have strong jaw muscles" question is in order.

According to the comments, depleted uranium is helpful against projectiles, but it won't do much against the compression from dragon teeth. It is usually used with steel or another alloy, however, so now the question becomes what can pierce steel effectively.

Let's use the hardness of steel and a handy unit converter, because for a quick chomp and pierce, tensile strength alone will not matter. While some of these materials may shatter if you put too much pressure on them, they are adequate for puncturing and tearing if you make them sharp enough.


Tungsten Carbide

Hardness

Some of the strongest heat-treated steel will measure at about 444 on the Vickers hardness scale, while tungsten carbide measures in at around 2242! Alternatively, using the Mohs hardness scale, steel is at around a 7, while tungsten carbide measures 9.

Organic use

It is difficult for a dragon to have tungsten teeth for several reasons:

  • Acquiring tungsten in abundance requires a really weird diet
  • Processing the elements to create an alloy requires extreme conditions (if they breathe fire, I guess this is plausible)
  • Tungsten may be toxic

A possible workaround could include dipping teeth of another material into molten metal, although I doubt molten tungsten carbide exists in nature.


Carbon Steel

Hardness

It's hard to find quantitative data to compare the hardness of carbon steel to regular steel, but note that as the carbon content increases, strength increases - so these teeth will likely be stronger than the tank material.

Organic use

It is difficult for a dragon to have carbon steel teeth because:

  • Acquiring steel in abundance requires a really weird diet
  • Processing the elements to create an alloy requires extreme conditions (if they breathe fire, this may be plausible)

A possible workaround could include dipping teeth of another material into molten metal, although I doubt molten carbon steel is easy to find in nature.


Chromium

Hardness

Chromium has a Vickers hardness of 1060 MPa, compared to steel's reasonable maximum of 444. It would definitely get the job done.

Organic use

Many yeasts have a high chromium content. While some forms of the element may be toxic, it's reasonable to think that dragons could consume animals that rely on this yeast - or they could cultivate the yeasts themselves.


Titanium

Hardness

Titanium has a Vickers number of 830–3420 - higher than that of most steel - so you should be all set.

Organic use

Organic titanium compounds are found in some natural reactions. These could occur in the prey of your dragons, or their prey's prey; with some more work and possibly some handwaving you could construct titanium teeth.


Diamond

Hardness

Diamonds are considered to be one of the strongest natural substances - with a 10 on the Mohs hardness scale, compared to a 6-7 for most steel. These are the most ideal teeth you could have.

Organic use

No organic processes can create, or have created, diamonds. However, since dragons tend to hoard gemstones (and some consume them) it's reasonable to think that a dragon's body could arrange diamond particles and bind them with an alloy to make semi-diamond teeth.


Ruby

Hardness

At a measure of 9 on the Mohs scale, rubies are significantly harder than steel.

Organic use

Similarly to diamonds, no organic processes can create, or have ever created, rubies. However, since dragons tend to hoard gemstones (and some consume them) it's reasonable to think that a dragon's body could arrange ruby particles and bind them with an alloy to make semi-ruby teeth.


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  • $\begingroup$ This was getting long but see also silicon carbide and boron. $\endgroup$ – Zxyrra Dec 17 '16 at 16:42
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    $\begingroup$ I'm very new to material properties, but isn't toughness also extremely important? For example, diamonds are extremely hard, but very brittle, so they can break more easily in certain circumstances. $\endgroup$ – Thom Blair III Dec 17 '16 at 22:51
  • $\begingroup$ Also, though, there is a new form of man-made diamond called Lonsdaleite that might be of use, since it is much harder than normal diamond. But I don't know about it's other properties. $\endgroup$ – Thom Blair III Dec 17 '16 at 22:52
  • $\begingroup$ @ThomBlairIII It is, although I reasoned when writing this that if the teeth are sharp they will puncture instead of shattering $\endgroup$ – Zxyrra Dec 17 '16 at 23:29
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    $\begingroup$ @Zxyrra true. Another thing to consider that may whittle down your options is that a dragon attacking a modern tank would really need teeth tough enough to handle reactive armor, especially the explosive reactive variety $\endgroup$ – Timpanus Dec 18 '16 at 15:53
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The dragon's jaws need to be strong enough to crush the tank, and its teeth need to be strong enough to resist not shattering at the tremendous pressure which this will require. Furthermore, the bone structure itself needs to be strong enough to hold the teeth in place, as well as not break under that same pressure. The tissue in its mouth must also resist severe damage from the metal shards, and sharp edges which will be pressing into it.

Last but not least, the dragon must be powerful enough to lift a main battle tank off of the ground, in its jaws, so that it can move it in an optimal position for crushing.

Since we have long left behind the rolling plains of realism, and entered the rocky valley of "this must now be solved with magic", I do believe that your dragon should be made of unobtainium.

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Foolish Wyrmlings!

You can't eat a human tank raw. You have to cook it for a few seconds with your fire breath.
Then it gets soft and chewy, making it much easier to get at the juicy parts inside.

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What about biologically formed carbon nanotubes?

This webpage had this to say regarding their physical properties:

On a molecular level, CNTs are 100 times stronger than steel at one-sixth the weight and have a very large aspect ratio making them very useful as a mechanical property enhancing filler material. Carbon Nanotubes conduct heat and electricity similar to copper but without oxidative concerns provided that they are well dispersed.

Since the base element for the chemistry occurring in all known life is carbon, that part is at least somewhat plausible perhaps - however, I'm not au fait on whether it's anywhere within the realm of plausible for a biological mechanism to deposit carbon atoms into a matrix to produce nanotubes, but it could be perhaps, depending on how deep you want to explain the processes and so forth. The properties around heat might even lend themselves to explanations/applications concerning the fire breathing and so forth and/or reinforcement against it.

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