By Heather R. Smith, AMRDEC Public AffairsAugust 15, 2013
REDSTONE ARSENAL, Ala. (Aug. 15, 2013) -- The Army is using some of the latest advancements in the areas of composite structures and 3D printing to better equip today's Soldiers.
In particular, engineers at the U.S. Army Aviation and Missile Research, Development and Engineering Center Weapons Development and Integration Directorate incorporate composite technology and additive manufacturing, sometimes called 3D printing, into a solution for Soldiers using the Javelin missile and the Javelin Command Launch Unit.
In anticipation of the future need to integrate Javelin into the network of sensor-shooter systems, WDI proposed a far target locator to provide accurate target data that could be passed from the Javelin gunner to other systems on the network.
But this solution resulted in another problem: added weight.
"If we're trying to reduce their burden, we don't want to give them a system that's heavy, and traditionally these accurate inertial navigation systems are ten pounds by themselves," said Virginia Franco, a mechanical engineer who worked on the Far Target Locator design.
It was imperative that the Far Target Locator be lightweight. A vendor was found to make lighter weight components for the inertial navigation system, but housing it in aluminum, which is the material traditionally used, was still going to result in too much weight.
So the solution was to bring in the expertise of the AMRDEC Composite Structures Lab team and AMRDEC engineer Keith Roberts, to design and fabricate housing for the FTL using advanced composite materials.
The collaboration on the Javelin FTL is part of the Close Combat Missile Modernization technology program managed by Devin Chamness from WDI and is the outgrowth of complimentary component-based development efforts researchers were performing under the Applied Smaller Lighter Cheaper Munition Components program that ended in fiscal 2012.
"We're trying to replace metallic structures with lighter-weight, carbon fiber reinforced polymer composites," Roberts said, "but by doing that you're often taking out other functionality, so a big part of what we're doing is trying to increase the functionality of composite structures by incorporating things like thermal management, electrical conductivity, and ruggedizing the structure."
The FTL housing is made out of carbon fiber epoxy, which is the same material used to make light-weight sporting equipment like tennis rackets and fishing poles.
In addition to being lightweight, Roberts said other benefits for composite materials in missile applications are tailored stiffness, strength and vibration damping, and customized shapes.
There are many different ways to build composite structures.
The FTL housing will be made using a process called Resin Transfer Molding. The first few prototypes are built by hand lay-up, using a foam tool that is machined to the needed shape, and a carbon fiber prepreg, or "pre-impregnated," fabric impregnated with epoxy resin and cured at elevated temperature.
But hand lay-up is more time consuming and more labor intensive; the Resin Transfer Molding process is better for production. "In resin transfer molding, you basically take a dry fabric that's got a tackifier on it and lay up the structure in a clam-shell mold," Roberts said. "Then you've got a carbon fabric pre-form, and you basically pump resin into the mold to infiltrate the pre-form."
A pre-form is a structure that is the same shape as the final product, over which resin is poured to create the composite.
To build the mold, the lab is using additive manufacturing, which has been commonly called 3D printing.
"We wanted to use additive manufacturing because it's really good for making tools where you've got a low part count," Keith said. "With traditional resin transfer molding, you want matched metal tooling; for making composite structures. Metal tooling is the best way to go for a high volume production. But we're going to make tens to hundreds, which is not a lot really, so we thought let's use additive manufacturing. It also allows us to make internal cavities since additive manufacturing builds it up layer by layer. We can also modify the part design rather easily because the tooling is lower cost."
Stereolithography is one of the most mature additive manufacturing methods and will be used to "print" the mold at Edgewood Chemical and Biological Center. AMRDEC and ECBC are both part of the U.S. Army Research, Development and Engineering Command.
Additive manufacturing is so important to the future of composites that Roberts, along with fellow AMRDEC Composite Structures Lab engineer Lance Hall, have proposed a Science and Technology program to bring additive manufacturing capabilities to the AMRDEC.
"We need the young engineers to start thinking in these terms and designing with additive manufacturing because it's the future and it adds a new capability," he said. "It gives you a lot of other options that you wouldn't ordinarily have with traditional machining, so the sooner we get into the mix the more we can have people thinking in that mindset."
AMRDEC is part of the U.S. Army Research, Development and Engineering Command, which has the mission to develop technology and engineering solutions for America's Soldiers.
RDECOM is a major subordinate command of the U.S. Army Materiel Command. AMC is the Army's premier provider of materiel readiness -- technology, acquisition support, materiel development, logistics power projection, and sustainment -- to the total force, across the spectrum of joint military operations. If a Soldier shoots it, drives it, flies it, wears it, eats it or communicates with it, AMC provides it.