April 2016
By Stew Magnuson
A soldier completes the final part of welding on an up-armored truck. The Army Tank Automotive Research Development and Engineering Center continues to invest millions to improve the vehicle armor that protects troops from small arms and explosives. And universities are pitching in by inventing new life-saving materials. Gen. Robert “Bo” Dyess, deputy director of the Army Capabilities Integration Center at the Army Training and Doctrine Command, recently identified “advanced protection” as one of the Army’s top eight acquisition priorities. One of the service’s ultimate goals is to produce better protection, but at an affordable price, said Chip Filar, deputy associate director of ground systems survivability and ballistic protection at TARDEC. “Much research has been done by the Army — along with industry and academia — on advanced materials and their application to advanced armor designs, however, armors using advanced materials have typically been too costly to meet system goals,” he said in an email. It’s unrealistic to find a material less expensive than regular steel, he said. Some ceramic composites can run anywhere from three times to 40 times the price of steel. “The cost of these systems is important, and … we want to work to make them as affordable as possible, however, realistically they will never be as cheap as steel and aluminum armor simply due to the raw material costs,” he said. “We are working with the ceramic industry and with composite material developers to reduce both the cost of the constituent materials through improved processing efficiency, as well as to reduce the armor system manufacturing cost through automation,” he added. TARDEC is aiming for fiscal year 2019 for an “optimized system demonstration of new protective systems,” he said. The command recently awarded Alcoa Defense a $50 million, five-year research-and-development contract for various projects including a monolithic hull to bolster troop protection, and improved welding processes. The latter is important because the seams in armored vehicles are the most vulnerable areas, Filar said. When it comes to ceramics, plates that need to be joined create real challenges. The more complex the interface between two plates, the harder it is to confine the explosion’s effects, Filar said. It requires complicated shapes, which adds to the weight and negates some of the benefits ceramics provide. It also adds to the expense, he said. Eric Roegner, president of Alcoa Defense, said there are similar complexities when it comes to welding the alloys that comprise vehicle armor. The first task order under the company’s contract with TARDEC will tackle this problem. “The weakest parts of any armor solution are the welds. They are less strong. They are more brittle. And if you’re going to get hit by an [improvised explosive device], for example, the two issues you’ve got to manage is dynamic deflection — you deflect most at the weld. And the second is rupture – you rupture the weld,” he said. A weld wire made of a particular alloy is used to help join two plates. It starts off solid, is turned to liquid, then becomes solid again. “That can change the mix of the alloyed elements in that little zone,” he told National Defense. It’s similar to a snowball and an icicle, which are both frozen water, but have different crystal structures. Their creation depends on the rate of cooling. As for welds, how much heat is applied and how quickly it is cooled can make the weld stronger, or more brittle, depending on what is done, he said. “All of that will change the microstructure of the material at the weld,” Roegner said. If there is any change to the alloy, that will completely change the whole equation. We are “developing the weld wire and processes to make that weld as strong as possible, and there is a huge amount of R&D that has to go into that,” he added. The contract also calls on Alcoa to build on the work it did on a previous program to create a monolithic hull. The company at its Cleveland plant has a 50,000-ton forge, the largest in the world, which is capable of making complex, large, one-piece components for aircraft, ships and vehicles. Its first customer was the Airbus A380 commercial airliner. Then the joint strike fighter used the forge to drastically reduce the weight and complexity of the aircraft’s bulkhead. The previous bulkhead began with a large piece of metal, which had to be machined, flanged and bolted together. It had 100 separate parts. Now, there is only one piece, the weight was reduced by 400 pounds and there is no longer a need to have a supply chain for those other 99 pieces, he said. “That is the same concept that we want to take for the [vehicle] hull,” he said. In a partnership with BAE Systems and the Army Research Laboratory, Alcoa created the largest monolithic component with the forge to date, when it made a hull — the underside of a truck — that roughly matched the size of a Bradley Fighting Vehicle. A Bradley or a Paladin M109A6 cannon artillery system has about nine large plates underneath that need to be welded, which takes time and money. If there is only a need for four inches of thickness at the bottom and two inches at the top, the excess metal needs to be machined off. Other parts have to be bolted on, he noted. “Think about the complexity of making an understructure. Now, imagine making it in one piece, where you’ve got exactly the right amount of metal, exactly where you want it. You’ve got all the bracketing from engine mounts to axle collars already baked into the shape and you’ve gotten rid of the welds,” he said. The savings don’t necessarily come from raw material costs, but the reduced amount of manufacturing time and the simplification of the logistics tail, he said. “It provides a radical improvement in performance, while reducing the installed costs,” he added. While he could not share the test specifications, Roegner said the hull was blasted twice “with something more than any vehicle is going to see in the field.” The hull showed no discernible damage. The next step will be to take layers off the hull and continue to run blast tests to see at what point it will finally rupture. Then the program will identify specific vehicles the hull could be placed under, he said. The exact same technology can be used for side panels, top panels or any structure where plates are welded, he said. It can’t, however, make an entire vehicle shell. “The Holy Grail of armor is: get rid of the welds,” he said. Meanwhile, basic and applied research on stronger materials continues at universities. A team at the University of California at Los Angeles made a splash in December when the journal Nature announced a new metal comprising magnesium, ultra-hard ceramic silicon and carbide nanoparticles. Magnesium has several desirable properties, said Xiaochun Li, Raytheon endowed chair in manufacturing at UCLA’s Henry Samueli School of Engineering and Applied Sciences. It is light, yet strong, found in abundance on Earth and has high plasticity, which means it can better absorb the impact of bullets and blasts, he said in an interview. It took about 10 years to figure out how to make the three elements disperse in a uniform manner without clumping. Without that, the metal would lose its plasticity and become too brittle, Li said. The research was conducted without the benefit of military funding, but since the article was published, he has received eight inquiries from military agencies and defense contractors. One company will help scale up production of the material in order to make body armor plates. “First we will work on smaller body armor applications, but then there are no l
imitations on us to push forward for even larger structures like vehicle armor,” Li said. Afsaneh Rabiei, professor of mechanical and aerospace engineering at North Carolina State University, has developed a porous steel that offers high protection against bullets and blasts, but is much more lightweight. “The material is basically like a bubble wrap, or Styrofoam, but in a metallic version,” she said. Normally, an air bubble in steel would make the metal weaker. But when dispersed in a uniform manner, it becomes stronger. It’s no different than the thin layer of Styrofoam in cartons that manages to protect eggs, or the skull, also made of a porous material, which protects the most vital human organ. “It provides a cushioning ability that can absorb impacts,” she said. “She could not reveal specifics, but the material in tests was able to completely stop “heavy” caliber armor piercing bullets using about one inch thickness.” She is now working on optimization of the armor for protection against both blast and ballistic. She continues to collect more test data against larger threats, and hopes that Army vehicle programs take notice. More recently, she has received funding from the Defense Department’s joint aircraft survivability program. TARDEC’s Filar said there are other ongoing projects to make vehicle armor more effective. Additive manufacturing, better known as 3D printing, is being looked at, but it is still in the basic research phase. “Additive manufacturing has the potential to reduce the cost of armor systems that require complex geometries or require substantial machining/processing,” he said. But the materials used in this method simply aren’t strong enough. Both the Departments of Defense and Energy are sponsoring the basic research looking into stronger 3D printing materials, he said. There is also work on armor that can adapt and react to its environment. “The concept is to use as much information as possible about the surrounding environment — threat likelihood, temperature, humidity, terrain, etc. — to optimize the armor response in a way that increases its performance in a given engagement,” he said. He declined to give further details as much of that work is classified.
Photo Credits: Army, Dr. Afsaneh Rabiei Clarification: Update clarifies the results of the porous steel heavy caliber tests.