Microbullets Test Material Strength for Military & Aerospace

It's easy to see what happens when a bullet hits an object, but researchers at Rice University and MIT (and its Institute for Soldier Nanotechnologies) wanted to know what happens at the nanoscale - with microbullets. The researchers were inspired by their observations in macroscopic ballistic tests in which a complex multiblock copolymer polyurethane material was able to not only stop a 9-mm bullet, but also seal the entryway behind it. The research team created nanoscale target materials, microscale ammo, and even the method for firing them. The team's main goal is to find ways to make materials more impervious to deformation or failure for stronger and lighter body armor, jet engine turbine blades for aircraft, and for cladding to protect spacecraft and satellites from micrometeorites and space junk.

Transcript

00:00:01 [Music] well this particular piece of polymer is a polyurethane and it's interesting because it's got three 9mm slugs that have been shot into the backside and have been arrested inside that polyurethane and there's no macroscopic damage the material hasn't failed it hasn't cracked even you can still see

00:00:23 through it so this be a great ballistic windshield material and what we wanted to do is find out why this particular poly Ane works the way it does experimentally it works and theoretically no one understood why this particular kind of material which actually has nanoscale features of glassy and rubbery domains uh would be so good at dissipating energy what we

00:00:45 did was to work with model material a polystyrene polymethyl Cy oxane polymer which has glassy and rubbery components just like the polyurethane does but we can uh control its micro structure at the Nano scale and form parallel layers that are only 20 NM a piece thick and these things form a parallel stack and it's a sort of an ideal starting morphology and then instead of shooting

00:01:12 a 9mm slug into it we decided to uh miniaturize the bullet if you like so we're shooting a silic sphere that's only 3 microns in diameter human hair is about 50 microns in diameter so this is like more than a tenth smaller than the diameter of a human hairir so we have sort of a micro bullet that we're shooting into into a nanoscale structure and then after the impact of the bullet

00:01:34 we can go in and cross-section the structure see how far and how deep uh the bullet gut and in fact see what happened to these nice parallel layers of glassy and rubbery domains they they sort of tell the story of the uh evolution of the penetration of the projectile and help us understand on at the nanoscale What mechanisms are taking place in the material in order for this

00:01:55 thing to be such a great uh high- performing lightweight uh ballistic prote material in the microscopic image you are looking at the actual uh projectile projectile is tiny tiny tiny so each side is about 3.7 Micron diameter silica bead so on the microscope you can aim the projectile and then after aiming we can shut the laser pulse by the laser pulse the

00:02:22 projectile can move toward the sample the goals of the research is to be able to develop met better materials lightweight materials for protection and of course body armor for soldiers would be one um turns out that the turbine blades on engines also have very highspeed impacts from say hail or sand that gets into a a jet turbine engine uh and satellites uh up orbiting the Earth

00:02:47 uh there are micr meteorites up there very small projectiles going very fast and occasionally these impact the satellite and poke holes in it so being able to develop lightweight materials that have Superior resistance to these sort of uh I would say extreme uh Dynamic conditions where the velocities are uh kilometers per second lightweight is is

00:03:08 really a big deal if this was a piece of Steel uh it wouldn't perform as as well as the polyurethane and it would be seven times heavier