How strong would chitin armor really be?

[Darmalus]

It shows up from time to time in fantasy and sci-fi, chitin armor. Usually from giant bugs.

So, how tough would chitin armor really be? How would it perform compared to more normal armor? Assume you can make/shape/form it in any arbitrary shape and thickness.

[biostem]

Well, it really depends upon its thickness, and whether it's made form the same material as normal exoskeletons. Many settings have such creatures possessing natural metallic/crystalline or other exotically-composed exoskeletons.

In general, though, they'd be quite effective against slashing or glancing blows - heck, you can drag a knife against your fingernail, which is pretty thin, with only a painless light scratch to the surface, while a slash of similar pressure would cut your skin right open. Against firearms or larger purpose-built weapons, it wouldn't help nearly as much.

[Lord Revan]

it might also depend on how the armor is made if was made like normally depicted aka essentially plate armor where the metal is replaced with chitin would probably very weak against maces and axes (and possibly some forms of a swords as well). but if you made use of the fact that chitin as material is more flexible then steel/iron you could weave it so that the armor would flex when it with a mace or other high impact weapon and break so easily (that's assuming it's not exotic or magical chitin).

[Sea Skimmer]

Would depend on the actual structure; chitin formed into a clamshell isn't exactly the same as a typical insect endoskeleton. Generally though it's not going to be able to be stronger then human bones or teeth are, and thus while it could have useful shock absorbing properties it will not be very effective at all against any kind of direct attack with metal edged or piercing weapons. The softer less shattering forms it can take also tend to have poor environmental resistance. Aka your suit of armor would degrade in the sun; though it would be highly resistant to water which beats leather and cotton based armors.

Also much of the strength of biomaterials like this come from very detailed trial and error evolved nanostructures, endoskeletons for example normally have multiple plys of material running in different directions for improved strength, and just about all of them are actually composite materials (as in major fractions are different materials, not say 99% chitin and 1% other). So the actual value of such armor would be highly dependent on the exact piece bio material used, and where it was placed on the user, directionality will matter. If you just began sewing together chunks at will you'd get a far inferior result to a carefully articulated armor suit.

Suffice to say this would take a serious amount of research and full scale testing to develop, which is not impossible with say 12th century level technology, but rather unlikely to be worth the trouble. Metal works awesome for armor precisely because its such a homogeneous unidirectional material. You can forge hardness into it, but out of the mold it doesn't matter which way you use the material which is very handy for creating reliable results.

[Lord Revan]

I suppose it might develop in a place that has very poor supply of high quality metal ores but strong supply of chitin.

[Broomstick]

Rather than attempting to find/use/make really big pieces of chitin, what about using smaller pieces for lamellar or scale armor?

[Elheru Aran]

Rather than attempting to find/use/make really big pieces of chitin, what about using smaller pieces for lamellar or scale armor?

In that case it depends on a.) how well made it is and b.) how strong your binding materials are. Lamellar, I think, would be better as you have more overlap to your plates and it's a tighter assembly-- but from what I understand it's also very confining.

A brigandine or coat-of-plates are also options.

[Adam Reynolds]

Suffice to say this would take a serious amount of research and full scale testing to develop, which is not impossible with say 12th century level technology, but rather unlikely to be worth the trouble. Metal works awesome for armor precisely because its such a homogeneous unidirectional material. You can forge hardness into it, but out of the mold it doesn't matter which way you use the material which is very handy for creating reliable results.

This is also largely true with metal in comparison to high tech potential replacements. They can beat steel in unidirectional stress in a laboratory but are more likely to fail when the stress comes from several directions at once(as inevitably happens with massive structural components when used in reality).

[Alyrium Denryle]

Oh hey, my dissertation broached this a bit...

To use a grasshopper as an example, the harder parts of the cuticle are about as resistant to elastic deformation as human bone, with plastic deformation resistance being about as high as that of brass. But that is just a grasshopper, and the exoskeleton is pretty damned thin. Other species have much more formidable defenses, but very few people actually test the material properties of insect exoskeletons.

[Darmalus]

So, of I understand this right, chitinous armor that could come from something reasonably earth-like biologically (no unobtanium shells) would be ideally lighter than metal, but roughly as hard. Correct me if I'm wrong, the stuff would be more brittle than it's metal counterpart. So once penetrated you'd start getting cracks and a drastic loss in strength.

Thanks for the heads-up that insect exoskeletons aren't mostly chitin, Sea Skimmer. I hear the word "chitin" used to describe it so often I just assumed that's what it was mostly made of.

Alyrium, is the reason for lack of testing lack of interest, funding, or are insect exoskeletons just really difficult to test?

[Alyrium Denryle]

Alyrium, is the reason for lack of testing lack of interest, funding, or are insect exoskeletons just really difficult to test?

Lack of interest, I suspect. The tests are relatively easy to perform if you make friends with someone in the engineering department who has the proper equipment. My dissertation only went there at all because I suspected that the larvae of some dragonflies had angled armor on their abdomens and prevented penetration by the palpal lobes of Anax junius, but that was after data collection was over so it was basically me spitballing upon my observation results. I could test it easily enough. Need more nymphs and a load cell, then to find a friend in the engineering department wherever I end up...

[LadyTevar]

In that case it depends on a.) how well made it is and b.) how strong your binding materials are. Lamellar, I think, would be better as you have more overlap to your plates and it's a tighter assembly-- but from what I understand it's also very confining.

A brigandine or coat-of-plates are also options.

Actually, lamellar armor is far less confining than plate or brigandine. Due to the overlaping plates, it molds to your torso better, while still providing coverage, as you can see in this LINK.

Seen also in leather HERE

It also is able to fit the curves of a LADY (amusingly, this pic is from Spacebattles forum.) I believe this is plastic armor, which would be most like chitin.

[Zeropoint]

but very few people actually test the material properties of insect exoskeletons.

That seems to be the truth--I looked for scholarly papers and engineering data, and couldn't find any. This is an oversight that must be corrected!

[Zixinus]

What existing animal has chitin/exoskeleton most likely to be useful as armor? My first thoughts are crabs. Is there any record of people using crab shells or something like it for armor?

[Broomstick]

A quick google gave me the info that in India they've apparently used pangolin scales for the purpose - not an insect or arthropod, but it does follow the general idea of using an animal's natural armor for the purpose.

One of the problems of using insect shells is their size - they're very small. The shells of horseshoe crabs might be a possibility, but I'm not aware of them ever being used in such a manner any more than any other crab shell. I'm not aware of any terrestrial insects or arthropods that have shells large enough to be useful for such a project.

[Alyrium Denryle]

What existing animal has chitin/exoskeleton most likely to be useful as armor? My first thoughts are crabs. Is there any record of people using crab shells or something like it for armor?

Too brittle in sections that are too small.

[General Zod]

What existing animal has chitin/exoskeleton most likely to be useful as armor? My first thoughts are crabs. Is there any record of people using crab shells or something like it for armor?

Armadillos can deflect bullets up to .38 caliber.

[Broomstick]

OK, that's now makes armadillos and pangolins. Anything else to add to the list?

[Zeropoint]

The bulletproof armadillo incident is a little suspect . . . many believe the shooter missed and the bullet bounced off a rock.

I seem to recall that turtle shells have been used as armor. I mean, used by humans as armor. Turtles have been using them as armor for a while now.

[General Zod]

The armadillo may not have survived but I think it could be effective if you layered it's plating.

[Sea Skimmer]

Anything could be effective with enough layers and thickness. Also deflection is a thing. At steep grazing angles even long rod sabots make of DU or tungsten can ricochet off normal structural concrete. Concrete is stronger then animal scales, but its a bunch of crap compared to hardened tungsten alloys. Such radical deflection is plausible for animals scales at extreme angles too such as vs a .38cal bullet. The idea that an armadillo caused a 180 degree ricochet though is pretty much nonsense. The guy hit a rock, or more likely shot himself and lied out his teeth. People do that all the fucking time.

Against melee and arrow weapons were dealing with a combination of shearing and piercing effects largely governed by momentum and not kinetic energy. That's good from the standpoint of bioinspired armor, because biological structures tend to be low on hardness which severely limits their ability to deal with high velocity-high energy attacks. And even when they are hard it tends to be at the expense of tensile strength, in part because living biological material must be porous for circulation flow.

The problem with chitin in an insect or clam context is it's actually trying to be a pretty hard structure, with is just a path to failure here. One wants to exploit its ductility and strain strength, which is where bone comes into play. And no surprise, a lot of bone armor has been used in history. Doesn't sound as sexy as 'chitin' but its much more specifically what you'd actually want given the limitations of biomaterials.

Once were talking heavy steel weapons though its just not going to work well, the overmatch is too high leading to catastrophic failure. That's why Gambeson style armor made from natural materials was heavily layered, just like modern soft unnatural fiber armors are and used to back stronger metal armor, or alone. The layering effect helps spread the impact and mitigate the effect of strain waves causing shattering of the material providing the maximum possible time for the material to absorb energy. The lower the velocity a hit the better this sort of effect works. This is why in real life even the immense strength of kevlar doesn't turn into just using thicker kelvar for body armor to stop rifles. The rifle bullets are simply too fast for this approach to be effective. Instead hard plates of metal or ceramic (good enough cement or glass would also actually work, if you really wanted) are used to slow down and breakup the hit. Then the kevlar stops the remaining energy spread over a wider area.

I suppose a large number of layers of densely packed insect shells might actually be fairly good armor, but this presents an very obvious manufacturing problem for medieval technology. Or even modern technology given the size of typical insects.

Some animals actually have layered scales, I can think of at least one fish and I recall reading of others, as a way of covering the gaps in scales, but I'm not aware of any which use more then 2 layers. In principle some much stronger forms of biological armor might be chemically possible, but it'd be hard for them to evolve because they'd almost certainly have a high metabolic cost, and probably restrict the ability of the creature using them too. Evolution I suspect favors protection that completely prevents serious damage a lot more then protection that merely reduces damage, because an injured animal will probably just die from a followup attack. Its a different situation then a battlefield. That's one of those special traits of humans that helped us become so powerful, we heal well, and we can treat wounds well even with no modern technology. No other animal does more then lick a wound. Big limitation to less then total protection.

[LaCroix]

For example, this is a boar tusk helmet... The must-have thing in 17th to 10th century Mycene. Even Odysseus had one...

[Sea Skimmer]

That image does a good job of showing the problems behind this. The holes are needed to lace the stuff together with leather cords, holes which cannot simply be made smaller in smaller pieces of material if the cord strength and durability cannot also be improved. The enemy weapon threat doesn't change. Nor easily drilled in material with excessive hardness relative to its other strength. And for all that trouble you either end up with gaps, requiring a strong backing, or else you accept overlap and thus high weight for the actual protection as well as a generally greater draw on labor and materials to make the design. With bone none of this is that great a deal, bone is already porous so it responds well to the stress caused by holes, and this also makes it light for its thickness, generally improving damage tolerance in general. Thinner harder materials will like holes less, true of anything you can make armor out of.

Some material like ceramic armors are basically non compliant with anything but solid shapes, while hardened steel armors can sometimes still be drilled but past a certain point (about 400 BHN IIRC) the work hardening this causes will not break the plate outright, but it will compromise the ballistic protection. The hardest steel armors around cannot be joined in ANY way. They have to be hot worked from the first actual casting into the desired shape, and then clamped onto the final product as applique.

Generally the thicker any given piece of armor is, the less hardness you want, but that's not very relevant to personal armors which are always going to be very thin in material terms. Indeed the problem is often increasing rigidity past that of the unitary material, which is a reason why medevil plate armor was meant to have a lot of padding under it. Even if the steel could resist penetration it could not resist deformation, being dented in with resulting serious wounds. Today we can make steels that could resist any reasonable human inflicted blow without deformation, but still not easily. The momentum problem at work. Human blows are hard pressed to be more then a few hundred joules of energy but a warhammer is a rather heavy thing.

[Darmalus]

If we aren't restricted to real-world forms (either bio-tech or giant bugs with just the right shaped bits to be harvested) how would the materials hold up? For example, if the above helmet was made of a single piece of tusk instead of many bits sown together.

[Sea Skimmer]

Better, but not by much?

I can't claim to have a lot of mathematically specific data on bone armor the way I do for proper armor materials, but it appears from the quick internet that it is around a 25-30 BHN rating in an adult human. That actually places it up towards pure copper (even ancient copper armors were alloys, but often unintentionally or unknowlingly) but only about one quarter as hard as the worst steel (120) while armor grade steels range from 200-350 for large plates (like battleship armor or tank armor) to 400-600 for thin plates meant to stop only small arms or absolute protection from blunt force on human scales. This suggests to me that bone armor is probably very credible against copper weapons, but not iron or steel. Which fits with other information I am aware of concerning ancient practices.

Hardness is not the end all of armor, but when you have gross overmatch situations it becomes very important. Because if you aren't hard enough to seriously slow a hit before it begins to deform, or ideally cause a major portion of the impact energy to recoil, you have to absorb that energy through eating damage. And once you start absorbing energy like this your on the path to complete failure.

Now given the same material a larger piece should have higher resistant per unit of weight, all else being equal. This is for various reasons, some of which I doubt I could usefully explain and some of which vary material to material. But a fundamental one is that the strain wave takes longer to reach the edge of the material, and then reflect back. If your strain wave is too high the material will begin to breakup under the first pass, instead of undergoing plastic deformation. (in a sci fi context FYI this strain wave behavior could be actively controlled by nanoscale actuators, for TRUE powered armor, this really works in computer simulations of ceramic armor). Also propagating through more material before reflecting back simply absorbs more energy. These effects loose importance as impact velocity increases though until hydronamic effects take hold and life changes. That isn't a big deal below about 800m/s though. Also this as another useful FYI, this is why why you don't see carbon fiber based armor against bullets or fragmentation. It's really strong in tension, but it has almost no ability to strain before failure. So carbon fiber armor would just massively shatter under high velocity hits. Carbon nanotubes and graphene aren't like this, but armor work with both is very preliminary.

So a single piece of bone armor would take a bigger hit both in absolute terms, and in proportion to its own mass, up to a certain limit. That limit is when the armor fractures. Aka cracks. The problem is as I've mentioned, that basically any realistic weapon of metal or frankly stone, is going to exceed that limit. its way harder then the bone armor, and its probably got enough energy that the crack won't be minor, it will be straight through. That's my gut feeling based on what I've seen random shit do to peoples actual bones. And what I think your could have on your head. Neck strength is kind of a problem, and bulk matters for other reasons.

An arrowhead might not cause major fracturing, the effect might remain local, but a heavy sword blow or warhammer hit certainly will. On the plus side we have no weak spots provided the shape of the original material is truly optimal, so we are much less likely to fail from a less then clear hit. On probabilistic scale averaged over many soldiers that's very useful. But it may mean nothing to any given person. Also given careful craftsmanship bone will not work harden from having the interior cleaned up to hit the human head. So we can craft the armor without creating new problems. Again that's pretty useful on a probalistic basis.

Still its just on a path of failure and being one solid piece only helps around the edges of the threat, not at the core of the problem.

The solid hits are when we have a big problem with a single piece bone helmet, because if it cracks the crack won't stop. Its going to want to split in half, if not then soon after. Probably though you will be dead as it splits completely and weapon edge contacts skull. In reality this is true of nearly any material, once cracking begins it simply doesn't stop. Oh it might slow down, it might take a while, but it won't stop. We've come up with concrete that can self heal chemically on a microscopic level, but its hardly meant for protection either. We've also come up with self healing composite armor, but that stuff literally has nanoscale glue packets mixed into it, and the healing is basically 'glue ceramic back onto fiberglass backing' rather then fundamentally eliminating the cracks. It doesn't help with the first hit, only improves performance against later ones.

So in this respect the one piece bone helmet is hurting us probabilistically, because anyone who does survive a damaging hit has a highly compromised helmet and will be much more vulnerabvle to future hits. And no means will exist to repair this helmet.

So for solutions to fracture...

A living biological system obviously can heal cracks, in fact it can potentially heal them back to original strength (generally not though) but that's not going to work for a dead bone helmet. Some kind of parasite living bone helmet gene spliced by force mages seems like the ideal 500 AD solution to that problem.

Fracturing can also be delayed by placing an armor under compression, pre tensioned concrete beams work on a similar principle, and a lot of vehicle based ceramic armor exploits this, but I'm not sure how you'd accomplish this more then 1-2 centuries ago (or with any valid point, since METAL) . Also the lower density of the armor, the less effective compression will be and bone is pretty light.

One way to mitigate the cracking problem is to use armor that doesn't really crack at a fundamental level. That's where woven fiber armor comes into play, and has for centuries. Specific fibers might crack and thus break in half, but they have no mechanism to directly propagate this to other fibers. Each fiber must be tensioned to the point of failure individually. That means even if the armor is fully perforated it isn't cracked. It just has a damaged zone that won't spread. Modern composite armors exploit the hell out of this, but I don't see a way to adapt it to reinforce our one piece bone armor, because bonding hard armor to fiber armor requires some very effective adhesives. When done right though it far exceeds the resistance of either material.

The problem is this only matters if you have multiple layers of material. gambeson armor and modern vests have 20-30 layers because any serious impact will just cut right through the first dozen or so, and only after it has been slowed with the later layers be able to exploit this behavior. A double layer of soft bone armor might be feasible in this respect, but I think thickness won't allow more then two layers. Maybe you could make such bone/exoskeleton armor out of an adult and a young version of the same giant insect shoved inside each other?

So overall I'd reckon a single piece bone helmet should immense low speed blunt trauma resistance, but its resistance to hardened impacts while improved, will still be a 'one hit only' kind of deal. And that isn't very desirable in a melee situation, all the more so in ancient times when you have no actual supply lines. Even if the warrior had money they might have nobody to buy a replacement off of. I just can't see how a reasonable piece of bone will avoid being cracked open by a direct blow by edged steel. And on top of that precisely because bone is soft and spongy it will have trouble causing deflections to avoid direct solid hits. It will actually help the impact bite and transmit high energy levels compared to metal armor vs metal weapons.

So the two layer bone is one possible approach. Another perhaps more realistic is bone on top of a wooden backing, which could provide both rigidity to damaged bone so it isn't useless after one hit, and a certain measure of additional protection against perforation of the bone. I can see that working pretty well, but it'd still be way inferior to a metal helmet lined with thick layers of fabric padding or even no liner at all. I'm playing around in my head right now with putting the wood on the outside, as a means of spreading the blow across the bone, but I think this will fail unless you had a very precise fit and very hard wood. That is not impossible in a fantasy context. I need to think more on it.

Interestingly a lot of modern effort is going into making synthetic bone, but specifically as shock protection to avoid brain injuries and blunt trauma, not to stop penetration.