The film “Terminator 2: Judgment Day” depicted a villain whose gaping battle wounds could seal themselves shut just seconds after being inflicted. Now, in a case of science imitating science fiction, self-healing armor may be what is in store for military vehicles.
Pradeep Rohatgi, director of the center for composites at the University of Wisconsin-Milwaukee, has been developing techniques that could soon be used to make self-healing armor for military vehicles.
This is accomplished by mixing microscopic “balloons” into the metals that are used to make armor while those metals are still in liquid form. The microscopic balloons are filled with materials that melt at low temperatures. As a result, cracks in vehicle armor could close up in a matter of minutes or even seconds, Rohatgi said. The balloons would break after a hit from a rocket, RPG or other battlefield projectile, causing the material inside to melt and seep out into the crack. Once it solidified it would close up any cracks caused by the strike.
Once a projectile fractures the balloons, the material inside can melt with enough heat. The heat generated by the hit could theoretically be enough to do the job.
Billions of micro balloons would either be distributed throughout the armor or placed in sections that are more vulnerable to damage, Rohatgi said.
The amount of heat produced depends on the speed of impact, as well as the material of both the armor and the projectile, Rohatgi said.
The possibility of installing these billions of balloons into armor raises questions of cost. But it would not be unaffordable, Rohatgi said.
For one thing, putting micro balloons into the armor means less aluminum or magnesium would be used. This would make the metal lighter, which would ultimately save money, Rohatgi said.
“So on one hand the cost of the micro balloons will [initially] increase the cost, but then the reduced amount of aluminum and magnesium will reduce the cost,” Rohatgi said.
Replacing damaged armor is expensive, he added. And micro balloons can be made from something known as fly ash, which is a cheap waste byproduct of coal.
At this point, Rohatgi’s group is making centimeter-sized samples from aluminum and magnesium, both of which are armor materials. It is also looking into ways to make self-healing ceramic armor.
The next step will be to make and test large samples. “I believe we are looking at a time horizon of three to five years [until] it can be deployed.” But this depends on whether industry is ready to partner with Rohatgi’s group and how quickly companies are willing to make prototypes, he said.
Requests for funds from the National Science Foundation have been turned down, although Rohatgi’s group is still in talks with the NSF, he said.
Tom Wagner, a senior engineer at the U.S. Army Tank Automotive Research, Development and Engineering Center and manager of Rohatgi’s project, said that the Army is interested in the work and believes it holds promise. In 2008, Congress approved $1.3 million for lightweight materials, including self-healing metals, Wagner said .
“The end product would be very useful to the Army, if they succeed,” Wagner said.