Non-Newtonian Fluid Stop a Bullet? I just saw a YouTube video about Non-Newtonian fluids where people could actually walk on the surface of the fluid but if they stood still, they'd sink. Cool stuff.
Now, I'm wondering: Could a pool of Non-Newtonian fluid stop a bullet? Why or why not?
If so, if you put this stuff inside of a vest, it would make an effective bullet-proof vest, wouldn't it?
 A: Yes, here is an example where they made a bullet proof vest by soaking Kevlar fabric in a non-newtonian fluid:
http://www.youtube.com/watch?v=LlEo5MbcaX0
The video is from 2006, I don't know if this has been developed further.
A: Actually non-neutonian fluids are a bit heavy and massive with regard to their bullet stopping efficiency. They could work with other approaches. 
This does not mean their tension surface is infinite. They are penetrable and a bullet applies huge surface tension
A: BAE Systems have already done this. Annoyingly there seems to be some problem on the BAE web server at the moment, but there's a description here with links to the BAE site. Alternatively Google for something like "liquid armour site:baesystems.com".
Dilatant fluids are very good at absorbing energy as forcibly shearing them requires evaporating the water between the particles, and this absorbs a lot of energy. There is more info about dilatant fluids in the answers to Why do non-Newtonian fluids go hard when having a sudden force exerted on them?
A: Glass is a non Newtonian fluid.
Over time a window will begin to sag a process that can take millions of years for silicon dioxide but as it’s often mixed with sodium or boron the process is accelerated, as even though glass is rigid and inflexible it is still in a non Newtonian state.
A Prince Rupert’s drop is glass and as such in a non Newtonian state and can stop a bullet.
So yes a non Newtonian fluid can stop a bullet.
I’m not sure that any state of matter can’t be described as a non Newtonian fluid. It may take millions or billions of years to manifest its fluid nature but any collection of molecules or atoms excluding atomic decay, chemical or thermal reaction would shift over time when subject to gravity.
Time is an arbitrary factor in measuring the fluid state of matter. The more fluid the state the faster it gives way to sustained force from a foreign mass, fluidity is subject to molecular & atomic bonds relative to gravitational force over time. Time being an arbitrary measure of decay measured by the rotation of the earth, time of orbit, distance between the stellar centre + Earth (1AU) and relative luminal velocity to those measurements.
