Polyurea used as Armour for a Vehicle

polyurea materials tend to have low decomposition temperatures and are not well suited to be armour because the spinning bullet impacts and moves it and there is a lot of heat at the impact point. They usually use Kevlar types of materials with a tighte weave in many layers.

http://www.dupont.com/kevlar/otherapplications.html

Thanks for your reply but why the USMC use the polyurea to increase the armour of their Humve, see: http://www.naulin.ca/

Waiting for your reply,

the object of my research is research to increase the armour of mobil wall wich are made for building for dangerous zone

Looks like it is used in conjunction with filler materials to absorb force and prevent spallation etc as part of a compound protection

http://www.google.ca/search?hl=en&q=%22dragonshield+ht%22&btnG=Google+Search&meta=

Thanks for the ref. , it seems you know what you are talking about, so do you think that direction of development of a new product is worth it, is there potential...what is your feeling.

Pierre Desjardins

I know a little bit.

If you want to stop bullets you can either stop them with brute force, as tanks do, or with a flowing restraining force, as bullet proof vests do.

Using brute force means solid armor = high weight, and some of the helicopter crew wear very heavy jackets that are effective, but far too heavy for ground troops to wear. Most of the so called flak jackets use a combination of ballistic cloth with thinner ceramic panels, armadillo style in overlapping pockets. This works fairly well, but none of this helps against head shots that hit flesh directly.

Currently there are two technologies that are going to the front of the pack and in 3-4 years seem to be the winning strategy.

The first one is the use of a layer of defromable material that separates and wraps the bullet. This makes a far larger object so that ballistic cloth works better at slowing it. In addition, the addition of the rest mass to the bullet mass means that the composite projectile is now going more slowly.

http://www.newscientisttech.com/channel/tech/dn9845-invention-ultimate-body-armour.html

The other tech is the so-called transparent aluminium, aluminium oxy-nitride

(not true aluminium metal, but a clear ceramic composite). It achieves it's clarity bu being made of small clear particles that are smaller than 1/4 wave of light and yet they have tiny interstitial gaps which prevent crack propagation and the underlying meterial(alumins or aluminium oxy nitride) is very very strong. Diamond would be even better and they are working on that as well.

http://www.af.mil/news/story.asp?id=123012131

Of course, nothing can save you if the kinetic energy is large enough that even a distributed shock can kill you. So a high velocity 1" round is fatal even if not penetrating

As an old soldier, i see that we are more protected than before, but i will look at what you sent me, and give you a feedback soon, thanks again for the info.

Pierre Desjardins

I suspect you are thinking of a polyurethane - polyurea combination. The polyurea, by itself, would likely not be a decent armor material. Polyurea has a very high cohesive energy density, but does not combine flexibility with hardness. We had the original patent on the "bullet proof" glazing for the Pope-mobile, bank "windows", etc. There is a gentleman who is a client of my consulting firm who has a number of patents on armor, which is light weight and has passed all test firing up to high velocity .50 cal rounds. I suspect until he gets the contracts completed, he would not be willing to discuss the composition in any detail. I am bound by client-customer legalities not to divulge any further info. Think of what polymeric material is very hard, but would elongate under a high-energy impact. What polyols would make a polyurethane-polyurea polymer that is extremely hard, rings like metal when dropped on concrete or steel, and can't be shattered or cracked with sledgehammer blows. One can make very good armor that is optically clear or opaque, for different applications. The limitations against using such a polymeric material by itself as a steel replacement are the thermal limitations, as well as cost constraints.

Well, since patents take a number of years to acquire and must reveal the method it seems that patent numbers can be dropped in here for people to look up, how about those?

As for light weight armor that stops high velocity 50 caliber rounds, I fear it will not protect the person behind the armor who just had his body subjected to an enormous impact. a 50 caliber slug at 900 M/second = death by impact if not by penetration.

A typical 50 caliber round that weighs 500 grains at 900 M/sec, ~=2700 fps

Energy of about 8000 foot-pounds for a 500 grain bullet at 2700 fps. Assuming full momentum transfer the 200 pound man would go flying at 40 fps and if the acceleration to that speed did not kill him, the next thing he hit at over 30 miles per hour would. Impacts like that are not survivable. In Kosovo the snipers would kill anyone they hit and knock down choppers with those rounds which they used from well inside apartments with no windows or lights, and they would wait, shoot one round and move immediately to avoid bullet tracking radar, which had real time counter round capability, but which needed an authorization to fire the counter round into the residential area. The counter round would be artillery fire, not too precise, and there would be occupied apartments all around the sniper's den. By the time people went there, the sniper was long gone.

As for making a hard polymer, you can add fillers to do that, but I am not sure to what degree the fillers attributes would lend their attributes to the composite, but I think it would work and a little length in the filler, like carbon nano tubes would be an obvious way to make a strong composite, too obvious to patent anyway.