Researchers See Aluminum As Alternative to Steel Armor
In response to these concerns, Navy researchers have been testing new armoring materials that could provide equal protection at a much lower weight. One of the more promising materials has the potential to be just as strong as steel, but as light as aluminum, said scientists at the Office of Naval Research. This tri-modal aluminum, as it is called, is a combination of various ceramic and metallic materials that provide a greater level of ballistic protection at a lower weight. It is being developed in the form of an appliqué armor kit — known as a “B” kit — for ground vehicles. The kit consists of panels that are attached to the vehicles’ exteriors for increased protection.
To combat insurgents’ roadside bombs, the military has invested in special mine-resistant ambush-protected (MRAP) vehicles and armor kits. But the rush to defeat explosions with bulked-up combat vehicles has created a paradox for the services. The metal plates add weight, which troops have complained is hampering their ability to maneuver around the battlefield and creating safety hazards, among other issues.
“Try opening the door of an MRAP or uparmored humvee right now, especially if it rolls over,” said Lt. Gen. George Flynn, commander of Marine Corps Combat Development Command, who returned recently from a deployment to Iraq. Because of the protective metal, the doors are extremely heavy — a perilous situation if troops have to evacuate the cabin during an emergency. “The answer is not hydraulics. What if they’re not working? We still need to get out of the vehicle,” he told an Office of Naval Research conference in Arlington, Va.
The weight of the MRAPs also have caused problems for Marines in Afghanistan, said Marine Corps Commandant Gen. James Conway.
“The Afghan roads are sloped in some cases, unlike roads here in the United States or elsewhere. There’s a lot of mountain trails and switchbacks and those types of things and the vehicle is still too heavy,” Conway told reporters at the Pentagon. “We’ve taken that back to the manufacturers. They’re working on it.”
The weight issue has become such a priority that all Marine Corps vehicle program managers currently are looking at weight reduction options, including lightweight armor.
That poses a significant challenge for vehicle designers, who must grapple with balancing the needs of protecting vehicle occupants from ballistic threats, roadside bombs and rocket-propelled grenades with the need for speed.
“It is a challenge to design a ground platform that maximizes survivability yet is light and agile enough to fight in the expeditionary warfare environment,” said Jeff Bradel, manager of Marine Corps Maneuver Science and Technology at ONR’s Code 30, Expeditionary Warfare and Combating Terrorism Department. His office is investigating technologies to counter ballistic threats, improvised explosive devices, mines and rocket-propelled grenades.
The tri-modal aluminum armor kits can be applied to a range of vehicles, Bradel said. “We’re pretty excited about that particular armor solution,” he told National Defense. “We hope to achieve a significant weight savings over currently fielded solutions.”
ONR is funding efforts to mature the material composition and develop full-scale panels for testing in about three years. During that test and evaluation period, scientists will conduct various ballistic and traditional strength and toughness tests for metallic materials.
“We’ve proven it as a material, in a small billet size,” said Greg Doerrer, technical direction authority lead for ONR Code 30. “What you need to do is produce that same material in large 175-to 250-pound billets that can then be rolled or turned into plate. That’s a lot of processing challenges.”
The ability to produce nano-scale materials, such as the tri-modal aluminum, exists today.
However, the ability to retain the desired material properties in larger plate sizes needs additional development, said Bradel. Both the Army Research Laboratory and the Office of Naval Research are jointly investigating options for manufacturing the material.
If researchers figure out a way to make the material in the sizes and quantities needed, the technology will be a boon for the services, Doerrer said.
For now, steel armor has become the norm to defeat the threats in the current wars. But older vehicles, such as the humvee, were not originally built to accommodate so much extra weight.
“You can’t just slap 5,000 pounds of steel on the side of a vehicle and expect it to drive around,” said Doerrer. “It’s not designed to handle that kind of weight.”
Future vehicles are expected to become even heavier because of additional communications and computer equipment that will become a standard part of the vehicle payload.
“That gear takes a lot of punishment when the ride is rough,” he said.
To address the problem, ONR is investigating advanced suspensions that can compensate for that large weight variation and increase the life span of combat vehicles.
“We’re looking at suspensions that can absorb more energy at the wheel end and translate less to the vehicle chassis and crew,” said Bradel. “This will allow the driver to maintain control while traversing rough terrain at higher speeds.”
The department is currently investing in two programs to improve the suspensions on the light armored vehicle, or LAV, as well as the humvee.
In the case of the humvee, the Nevada Automotive Test Center is finishing up durability testing on a fully active suspension system designed by the University of Texas and manufactured by L3 Communications. This electronically-controlled active suspension controls the motion of the wheels to smooth out the ride.
“It’s the Cadillac of suspensions,” said Doerrer.
Studies have shown that installing advanced suspensions on light tactical vehicles can significantly reduce overall life cycle costs by absorbing damaging shock and vibrations that would normally be transferred throughout the vehicle system, said Bradel. That means an extended longevity of life for many of the on board vehicle parts. For example, the need to replace brake shoes is lessened when the suspension absorbs more energy because the driver doesn’t have to accelerate and brake as much in rough terrain.
Unlike the four-wheeled humvee, the light armored vehicle has eight wheels with different suspensions on the rear and forward wheels.
ONR has contracted four vendors to do the preliminary conceptual design of an advanced suspension system for the LAV. ONR’s plan is to down-select to a single vendor who will build a full-up system that will be demonstrated in two years.