Ar500 steel plate can stop rifle bullets. In my brain I’m thinking like “well if kevlar is stronger than steel, then slab of kevlar of the same size of an ar500 plate should stop rifle bullets too”. Clearly it doesn’t and I don’t understand why
In: Engineering
it’s not just about strength. PSI is a factor.
basically the way kevlar works is it deforms around the bullet to catch it while dissipating a lot of the kinetic energy but also stopping the bullet from putting a hole in your body (that’s why even if you take a shot with kevlar on you should still probably see a doctor). if it was just a steel plate then (in addition to it being heavy) with 0 deformation the kinetic energy of the bullet (assuming it didn’t penetrate the plate) would be entirely dispersed into your body.
pistol bullets have a lower muzzle velocity but also tend to A not be jacketed, B are more likely to be hollow-point (hollow point being illegal in warfare but actually preferable in a lot of pistol situations) and in general have a lower PSI on impact than a rifle round typically
so kevlar saves you because it’s tough but ironically kind of soft but the issue with a rifle round is that because it’s very fast and very had and very pointy is it’ll cut the kevlar like a knife. so what the metal plate does is basically turn the rifle round into something less pointy and less directed so it won’t penetrate the kevlar.
mythbusters did a thing that uses similar principals but on a different scale where they were testing (from burn notice) whether or not you can use a phone book to make a car bulletproof. so first they just shot a car door and the bullet went through no problem. then they shot a phone book and the bullet made it all the way through. but then they put the metal of the door in front of the phone book the metal broke up the bullet enough that the bullet then couldn’t make it all the way through the phone book
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