A promising area of soft body armor involves armor built around non-Newtonian, shear thickening fluids. Newtonian fluids, such as air, have a strain rate that is proportional to the velocity gradient, as viewed perpendicular to the plane of shear, blah, blah, blah.
The faster that you try to displace a shear thickening fluid, the more viscous it becomes. A person wearing a shear thickening fluid, soft body armor would walk and bend at a rate much slower than the bending that would result from a bullet impact. To the wearer, the shear thickening fluid, soft body armor would feel like a normal soft body armor vest. But, when a bullet impacted the shear thickening fluid armor, it would feel very rigid to the bullet.
The classic example of a shear thickening fluid is the childrens' toy, Silly Putty. Conversely, ketchup is a shear thinning fluid. Once ketchup starts to move, it moves more readily...usually onto your shirt.
You can play with this at home by either going to Wally World and buying some Silly Putty, or you can mix a little corn starch and water in a bowl. If you go the Silly Putty route, mash it in your fingers a few times, fun huh? Now, roll it into a ball, place it on a firm surface, and smack it with a hammer. See the difference? Pour a handful of corn starch and a teaspoon of water together in the bowl and stir. Notice that the mix is harder to stir when you try to stir it faster. Tee-dah! Congratulations, you have just made a shear thickening, non-Newtonian fluid.
The faster that you try to displace a shear thickening fluid, the more viscous it becomes. A person wearing a shear thickening fluid, soft body armor would walk and bend at a rate much slower than the bending that would result from a bullet impact. To the wearer, the shear thickening fluid, soft body armor would feel like a normal soft body armor vest. But, when a bullet impacted the shear thickening fluid armor, it would feel very rigid to the bullet.
The classic example of a shear thickening fluid is the childrens' toy, Silly Putty. Conversely, ketchup is a shear thinning fluid. Once ketchup starts to move, it moves more readily...usually onto your shirt.
You can play with this at home by either going to Wally World and buying some Silly Putty, or you can mix a little corn starch and water in a bowl. If you go the Silly Putty route, mash it in your fingers a few times, fun huh? Now, roll it into a ball, place it on a firm surface, and smack it with a hammer. See the difference? Pour a handful of corn starch and a teaspoon of water together in the bowl and stir. Notice that the mix is harder to stir when you try to stir it faster. Tee-dah! Congratulations, you have just made a shear thickening, non-Newtonian fluid.
