News Article | April 3, 2017
The U.S. Army is developing a “third arm” device that can be attached to a soldier’s protective vest to hold a weapon. The purpose of the device is to redirect all of the weight of a weapon to the soldier’s body and lessen the weight on the soldier’s arms, freeing up his or her hands for other tasks. The prototype of the third arm weighs less than four pounds thanks to the use of carbon fiber composites. “We’re looking at a new way for the Soldier to interface with the weapon,” said Zac Wingard, a mechanical engineer for the Army Research Laboratory’s Weapons and Materials Research Directorate. “It is not a product; it is simply a way to study how far we can push the ballistic performance of future weapons without increasing Soldier burden.” As the Army Research Laboratory explained, some soldiers are weighed down by combat gear heavier than 110 pounds. Those heavy loads may worsen as high energy weapons are developed for future warfare. “You wind up pushing that Soldier’s combat load up beyond 120 pounds and they’re already overburdened,” Wingard said during the Association of the United States Army’s Global Force Symposium. “We have Soldiers in their late teens and early 20s and they’re getting broken sometimes in training before they see a day in combat.” To test the device, researchers are conducting a test with a few Soldiers using the M4 carbine on a firing range at Aberdeen Proving Ground in Maryland. As part of the test, the soldiers wear special sensors on their arms and upper body to measure muscle activity to determine if there’s a change in fatigue when shooting with the device. Researchers also score soldiers’ shots to see if there’s an improvement in marksmanship. The third arm could also allow soldiers to use future weapons with more recoil. Additionally, researchers plan to examine the device’s potential applications for various fighting techniques, like shoot-on-the-move, close-quarters combat, or even shooting around corners with augmented reality displays.
News Article | January 2, 2017
Ballistic composites are meeting demands for protective gear, equipment and shelter. Composites manufacturers are continually looking for ways to enhance the performance of materials, making them thinner, lighter and stronger. But producers of ballistic composites have a much greater incentive for improvement than most: the material changes they make can literally save lives. The most common types of composite ballistic materials used today are para-aramids (aromatic polyamides) such as Kevlar® and Twaron® and the newer high-molecular weight polyethylene (HMWPE) or ultra-high-molecular weight polyethylene (UHMWPE) such as Dyneema® and Spectra®. Military and police forces, the main customers for ballistic composites, have used one or both types for helmets, body armor, vests and shields and for armor components on tanks, helicopters, planes and other vehicles. Ballistic composites provide significant performance enhancement and weight reduction over metal ballistic materials in such applications. “When you replace metal with a non-metallic system like a standard polymer matrix composite material you’re significantly lessening the likelihood of degradation due to corrosion in extreme environments,” says Steve Taulbee, general engineer in the Office of the Director for the Weapons and Materials Research Directorate at the U.S. Army Research Laboratory at Aberdeen, Proving Ground, Md. The U.S. Army started investigating the potential of composite materials for ballistic applications (specifically Kevlar vests) at the end of the Vietnam War. In 1989, the Army fielded its first composite helmet in combat in Panama, made from a Kevlar fiber hardened by a thermoset resin matrix. The most recent iteration is the enhanced combat helmet (ECH), made with UHMWPE. “It improved ballistic protection by 35 percent over any and all of the previous generations of the Kevlar helmet,” says Taulbee. The Army is currently researching the use of UHMWPEs to reduce the weight of next-generation military aircraft, pursuing 3-D weaving with several industry partners, including Albany Engineered Composites and T.E.A.M. Inc. With military aircraft, there is a lot of pressure to reduce the weight of the armor without compromising protection, says Nick Baird, director of sales and marketing at Permali Gloucester Ltd. The company uses aramids, glass fibers and UHMWPEs to create ballistic protection for helicopters like the CH-47 Chinook and the AW101 Merlin. The materials have to resist vibration and crash loads and meet flammability specifications as well. Permali is investing heavily in the development of molded composite structures to provide mine and blast protection for vehicles. “We have shown that the right composite solution outperforms steel by resisting higher blast loads, by having lower dynamic deflection and by exhibiting ‘graceful degradation,’’’ says Baird. “Composites show very progressive behavior as you increase the blast loading, whereas steel fabrications tend to fail suddenly and catastrophically as you exceed their threshold.” In one case, Permali replaced a steel roof on a vehicle with a stronger, stiffer composite roof, providing a rigid and stable platform for a roof-mounted remote weapon station.
Hornbuckle B.C.,Weapons and Materials Research Directorate |
Rojhirunsakool T.,University of North Texas |
Rajagopalan M.,Arizona State University |
Alam T.,University of North Texas |
And 6 more authors.
JOM | Year: 2015
The immiscible Cu-Ta system has garnered recent interest due to observations of high strength and thermal stability attributed to the formation of Ta-enriched particles. This work investigated a metastable Cu-1 at.% Ta solid solution produced via mechanical alloying followed by subsequent consolidation into a bulk specimen using equal channel angular extrusion at 973 K (700°C). Microstructural characterization revealed a decreased number density of Ta clusters, but with an equivalent particle size compared to a previously studied Cu-10 at.% Ta alloy. Molecular dynamic stimulations were performed to understand the thermal evolution of the Ta clusters. The cluster size distributions generated from the simulations were in good agreement with the experimental microstructure. © 2015, The Minerals, Metals & Materials Society (outside the U.S.).
Cooper G.R.,U.S. Army |
Cooper G.R.,Weapons and Materials Research Directorate |
Costello M.,Georgia Institute of Technology
Journal of Spacecraft and Rockets | Year: 2011
Payloads that behave like a liquid are carried onboard some projectile configurations, and it iswell established that the internal motion of a liquid payload can induce destabilizing moments on the projectile. This paper creates a method to include the effect of a liquid payload in the fight dynamic equations of motion, enabling trajectory simulations of projectiles with liquid payloads. To include this effect, liquid payload moments are added to the applied loads on the projectile. These loads are computed by solving the linearized Navier-Stokes equations for a projectile undergoing coningmotion.To highlight themethodology, trajectory simulation results are provided for an example projectile with different liquid payloads configurations possessing stable behavior while one exhibits catastrophic fight instability. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Rogers J.,Georgia Institute of Technology |
Costello M.,Georgia Institute of Technology |
Hepner D.,U.S. Army |
Hepner D.,Weapons and Materials Research Directorate
Journal of Guidance, Control, and Dynamics | Year: 2011
The use of inexpensive, commercially available thermopiles sensors for roll orientation estimation of spinning bodies is explored. The sensors convert observed thermal gradients into an electrical signal well suited for onboard data acquisition and real-time signal processing. An environmental model emulating sensor stimulus for a sixdegree-of-freedom body is generated given standard atmospheric and typical ground conditions. When sensor characteristics are included, the fully developed model can be used to generate accurate sensor output as a function of Euler angles and altitude. Outputs from the model are then shown to compare favorably with experimental flight data, capturing the predominant and nearly sinusoidal signal variation as the projectile rolls. An extended Kalman filter algorithm is offered, which enables real-time roll angle and roll rate estimation using solely thermopiles as feedback. Example results demonstrate that the algorithm yields reasonably accurate roll information. Finally, a trade study demonstrates that roll error is further mitigated as the number of thermopile sensors is increased. This research shows that thermopiles could be useful in a diverse multisensor constellation as a convenient absolute inertial roll reference.
Silton S.I.,U.S. Army |
Silton S.I.,Weapons and Materials Research Directorate
33rd AIAA Applied Aerodynamics Conference | Year: 2015
The present study was undertaken to better understand the impact of the canard trailing vortex flow interactions on the aerodynamics of short length-to-diameter, fin-stabilized munitions when canards are deflected for pitch or yaw control. Advanced computational aerodynamic techniques were applied. Results indicated that the projectile trim angle remained at 6° for the pitch control canard deflections investigated. The trim angles were due to both positive canard pitching moments as well as increases in pitching moment for both the tail fins and body components due to interaction effects. For yaw control canard deflections, results show that significant yaw control can only be obtained at angles of attack prior to canard stall due to the individual local canard angles of attack. The effect of the canard trailing vortex interactions on the tail fin aerodynamics was greatest at small angles of attack. Canard-body interactions were most affected by the local flow; canard trailing vortices were not a contributor. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.
Silton S.I.,U.S. Army |
Silton S.I.,Weapons and Materials Research Directorate
29th AIAA Applied Aerodynamics Conference 2011 | Year: 2011
A computational study has been undertaken to predict the static aerodynamic coefficients and dynamic derivatives of the standard 0.50-cal army projectile using multiple simulations that are collectively called the virtual wind tunnel technique. Computational solutions have been completed and validated against experimental range data for a wide range of Mach numbers to include subsonic, transonic, and supersonic flight regimes. It was found that steady-state methodologies can be used to obtain the static aerodynamic coefficients and most of the dynamic derivatives with good agreement. However, the accurate prediction of the Magnus moment coefficient in the transonic and subsonic flight regimes remains problematic. Further investigation of grid resolution, including refined wake region, boundary layer growth rate and circumferential resolution, for the steady-state simulations, time-accurate, moving mesh RANS simulations, and LNS simulations have been completed without significant improvement seen in the prediction of the Magnus moment coefficient. The discrepancy in Magnus moment coefficient prediction is large enough that it appears to affect the predicted flight dynamics of the projectile.
McAllister Q.P.,University of Delaware |
Gillespie Jr. J.W.,University of Delaware |
Vanlandingham M.R.,Weapons and Materials Research Directorate
Journal of Materials Research | Year: 2012
An instrumented indentation method is established to accurately measure the local elastic-plastic material properties of a single fiber by accounting for the additional sources of compliance associated with fiber indentation. The Oliver-Pharr instrumented indentation data analysis method is compared for indentation of a standard, planar fused silica sample and in the radial direction of homogeneous, isotropic E-glass fibers of two different diameters. Compliance contributions from substrate deflection and other nonindentation-related fiber deflections are quantified and shown to be negligible. The added compliance observed is attributed to the lack of constraint due to the finite geometry of a curved fiber surface. This compliance contribution is accounted for by using a proposed area correction to capture the geometry of the curved fiber-probe contact combined with a structural compliance correction. Implementation of these corrections to experimental indentation curves results in accurate measurements of the fiber elastic modulus and hardness. © 2011 Materials Research Society.
Weingarten N.S.,Weapons and Materials Research Directorate |
Rice B.M.,Weapons and Materials Research Directorate
Journal of Physics Condensed Matter | Year: 2011
Molecular dynamics (MD) simulations using a recently developed first-principles-based embedded-atom-method (EAM) potential are used to simulate the exothermic alloying reactions of a Ni/Al bilayer initially equilibrated at 1200K. Simulations are performed in the isobaric-isoenthalpic (NPH) ensemble, which provides insight into the influence of pressure on atomic mixing and the subsequent alloying reaction. For pressures lower than 8GPa, the mechanism of mixing is the same: as mixing and reaction occur at the interface, the heat generated first melts the Al layer, and subsequent mixing leads to further heat generation after which the Ni layer melts, leading to additional mixing until the alloying reactions are completed. However, for simulations at pressures higher than 8GPa, the reaction does not occur within the time interval of the simulation. The results will be compared with our previous simulations of a Ni/Al bilayer using a different interatomic potential, which predicts substantially different pressure-dependent melting behavior of the pure components. This comparative study suggests that pressure-dependent melting behavior of components of reactive materials can be used to influence reaction rates and mechanisms. © 2011 IOP Publishing Ltd.