Graphene May Top Kevlar As a Bullet-Stopping Material

The Royal Society of Chemistry reports that U.S. researchers Edwin Thomas and Jae-Hwang Lee have been testing the strength of graphene mesh in one role it's probably destined to appear in down the road: as ballistic shielding material. From the article: We cannot use conventional techniques such as a gun barrel or gunpowder [on this scale],’ explains Lee. ‘Instead we used a laser to accelerate a microscale silica bullet [at the multilayer graphene target].’ The bullet was propelled into stacked graphene sheets at supersonic speeds of up to 2000mph by the gases produced by laser pulses rapidly evaporating a gold film. The team calculated the energy difference of the bullet before and after to determine the energy absorbed. Neil Bourne, director of the National Centre for Matter under Extreme Conditions in the UK, who was not involved in the research, described the technique as ‘very exciting’. ‘They have taken a standard laboratory ballistics configuration and demonstrated its utility on microscopic scales,’ he says. Graphene was able to absorb up to 0.92MJ/kg of ballistic energy in the test, with cracks forming around the impact zone. By comparison, steel targets only absorbed up to 0.08MJ/kg at the same speed.

Comments

Re:for all this talk... where is it?

[Anonymous Coward]

I think the problem lies in you get media coverage on the basic research and the release of a product but no media coverage on the years of development and implementation research in order to get from A to B. It's not sexy enough for media coverage.

sane units - FYI

[Orgasmatron]

No one but a reporter talks about bullets in miles per hour. 2000 MPH is about 3000 feet per second.

A typical handgun bullet (9mm, 45 ACP, etc) is going to be around 1000 to 1500 fps. Shoulder arms (223, 308, 30-06, etc) tend towards the 2500-3000 fps range.

The MJ/kg figures refer to Specific kinetic energy. To convert it to foot-pounds, you need to multiply it by the mass of the projectile to find the energy in joules, then multiply by 0.73756 (or do the dimensional analysis the hard way).

Re:sane units - FYI

[pushing-robot]

A Joule is equal to one newton-meter (or metre if you're so inclined). Force times distance.

Foot-pounds are the same: Force times distance (well, distance times force). The confusion comes from pound in this case referring to "pound-force" or lbf, a unit equal to one pound times g.

J/kg is a different measure, the specific kinetic energy of an object; the amount of energy per unit mass. The imperial equivalent would be ft*lbf / lb (foot * pound-force / pound)

Metric: J/kg = N*m/kg = (kg * m/s^2 * m)/kg = m/s^2 * m = m^2/s^2

Imperial: lbf*ft/lb = lb*g*ft/lb = g*ft = ~32.174 * ft/s^2 * ft = ~32.174*ft^2/s^2

As you can see, the choice of g rather than 1 ft/s^2 was unfortunate, but otherwise the systems are equivalent.

Re:insane units - FYI

[Anonymous Coward]

For sane units, 2000 mph ~= 900 m/s.

p.s. I'm an American, and I only use mph for driving speeds.

Re:I wonder

[denzacar]

Kevlar tactical vests, being essentially a ballistic, polymer weave, have a shelf life of only about 3-5 years or so before they lose their power to slow and stop bullets.

No they don't.

They are GIVEN a shelf life of 3-5 years based on lab tests interpreted in such a way that the continuous chain of procurement of such vests by the police and the military is maintained AND so the producers of said vests could cover their asses in court in case it's needed.
"See, your honor, evidence shows that the officer Smith exposed his vest to higher temperature and UV light than what is written on the label. Ergo, it is his fault that high velocity round our client's vest wasn't ever designed for, not to say that it isn't the greatest vest out there, wasn't stopped by the said vest which is still a perfectly safe vest if you buy it brand new every 3-5 years."

Back in reality, you'd need to either soak it in strong acid or expose it to direct UV for hundreds of hours for the fibers to lose a significant part of their tensile strength i.e. bullet stopping abilities.
450 hours of direct UV will degrade 4500 denier kevlar to ~65% and 1500 denier kevlar to ~35%.
900 hours will knock it further to ~48% and ~23%, respectfully.

Even then, that only means that the TOP LAYER is degraded. Kevlar is not transparent. It degrades because it absorbs UV light.
And that's IF it was worn on top of other clothes, without any kind of a liner or protective or decorative impregnation.
I.e. If police were running around in banana-yellow ponchos for protection from bullets.

It's in the specs and real-life tests by people who are re-selling USED police kevlar vests confirm it.

It's plastic. The stuff that will take millions of years to degrade out of the ecosystem.