Re: Kevlar spark gap armor - NOT!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Chris Roberts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>


Kevlar armor is great at stopping bullets and such, but according to what I 
know (thank you discovery channel) a knife or handheld weapon will go 
through it much more easily. A projectile exerts a quick force on the armor 
that will snap a lot of the fibers but it will stop after it loses it's 
momentum. Anything hand-held will exert a force that snaps through a lot of 
the fibers but there is a continuing force as the arm that's holding the 
weapon follows through. This will push through the rest of the fibers. So 
unless you can fire something at the kevlar somehow, you can't really test 
it's strength that accurately.

  Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: "Terry Fritz"



Hi All,

My 4 x 5 foot sheet of Kevlar arrived today. A very odd material
indeed. It is sort of rough but not too bad. Almost like a thick course
wool blanket. I don't find it irritating to the skin, but some folks
might. It is about 1/10 inch thick woven interlocked weave stuff. The
fibers are long and well attached so it is not "dusty" at all. Machining
and such would cause possibly bad dust, but just the fabric is pretty tame.

http://hot-streamer-dot-com/temp/P2060019.jpg

I found a pair of common tin snips cuts it like butter. A bit more
disturbing, I found my big razor sharp grizzly bear hunting knife also cuts
it like butter :-|

http://hot-streamer-dot-com/temp/P2060020.jpg

However, a Phillips screw driver and other blunt things are easily stopped
dead by the ! fabric. It is odd how much it resists the screwdriver, but the
knife cuts right through it. A common 2 inch nail also has no problem
punching through it.

I can easily see how many layers (like 1 inch) of the stuff could stop a
bullet. I am not so sure it would be great against knives (but far better
than nothing...).

To the matter at hand. I worry that small heavy tungsten bits may go
through a single layer. Certainly anything big, like a chunk of a rotor,
could easily be stopped buy the fabric. But small sharp fragments, or say
a tungsten rod tip hitting it at high speed, could go through it rather
easily. It is thick, so I don't know how easily one could impregnate the
fabric with epoxy. Probably need very thin epoxy and a vacuum process to
do it right. But in general, I can not recommend this stuff for spark gap
armor. there are probably different types of Kevlar and all that, but this
garden variety type soft ! fabric is not much use to us.

Cheers,

Terry



-Chris

"The trouble is not that the world is full of fools, it's just that 
lightning isn't distributed right." -Mark Twain

"Only two things are infinite, the universe and human stupidity, and I'm 
not sure about the former." -Albert Einstein