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‘Smart’ armor learns more with every bullet

Smart armor being developed by scientists and engineers can not only predict its own failure, but also identify the size of bullets shot at it and even generate electrical power upon impact.
Image: Armor test results
Intelligent armor generates a small voltage when bent, such as when it is hit by a bullet.TARDEC
/ Source: Discovery Channel

Smart armor being developed by scientists and engineers at U.S. Army Tank Automotive Research, Development and Engineering Center in Michigan can not only predict its own failure, but also identify the size of bullets shot at it and even generate electrical power upon impact.

"As a kid, everyone played those video games that showed you how much armor you had left as a percentage bar," said John Wray, a TARDEC contractor. "That's exactly what we're working on here and more."

Intelligent armor is based on piezoelectrics, or materials that generate a small voltage when bent. The reverse is also true: Apply a small voltage, and a piezoelectric material will bend.

The sensors TARDEC scientists are installing on armor plates use both features. The armor itself isn't new, but the sensors are.

Each plate of armor, whether its wrapped around a soldier's body or a vehicle's chassis, has two piezeoelectric sensors attached to it.

An electric current flows into one sensor and turns it into mechanical energy in the form of a tiny vibration that ripples through the armor plate. The other piezoelectric device takes that mechanical vibration and turns it back into electrical energy.

Anywhere from five to 15 volts of electricity is pumped into, and out of, an intact plate of armor. If the armor has been damaged by bullets, shrapnel or anything else, some of the current released into the armor won't be picked up on the other end.

By measuring just how much energy is lost, the TARDEC scientists can determine how damaged the armor is.

The research into intelligent armor began several years ago, says Thomas Meitzler, a research scientist at TARDEC developing the intelligent armor. The Army approached TARDEC about finding a way to measure armor's integrity in the field.

"Right now, there are really only two ways to evaluate the health of a vehicle's armor," said Meitzler. "One is to get out and manually inspect the armor. The other is to bring it to a vehicle depot for an ultrasound." Neither option is ideal when soldiers are in the middle of a battle.

A third, real-time option was needed. Piezoelectric sensors were the answer.

The piezoelectric sensors don't just monitor armor's integrity. They also could help to make it stronger.

Each bullet striking the armor would create an electricity generating shock wave. It wouldn't be much electricity, says Meitzler, certainly not enough to power the vehicle, but it would be enough to run a small sensor if enough bullets hit the armor plating.

Each bullet would create a slightly different amount of electricity as well. Complex mathematical algorithms, also being developed at TARDEC, would analyze the amount of electricity generated by a bullet's impact and discover what kind of round was used.

A .22 caliber bullet, for example, will generate less electricity compared with a .45 caliber bullet.

The combination of knowing your opponent's weaponry and having real-time information about the integrity of the armor could save the soldiers' lives. "If you know that one side of the armor is weakening, you could turn the vehicle to protect that side," said Meitzler.

Other scientists are enthusiastic about the research.

John Ohab, the Department of Defense's new technology strategist, thought of Star Trek when he heard of the new armor sensors. "There was always damage to a certain part of the ship and a graphic that displayed what part was injured," he said.

Armored vehicles and soldiers could be just the start, says Ohab, adding that he doesn't see any reason why the sensors couldn't eventually be deployed on ships or aircraft.

Vladimir Genis, a professor of applied engineering technology who also develops piezoelectric devices at Drexel University, was also impressed with the research.

"This is an absolutely excellent idea," said Genis. "There is so much energy that simply disappears. If we can even capture a portion of that energy, we could power a multitude of electrical devices."