Ceramic composite protection for turbine disc bursts

Ceramic composite turbine disc protection panels for the A300B were developed using armor technology. Analytical predictions for modifying the ballistic projectile armor system were verified by a test program conducted to qualify the rotor containment system. With only a slight change in the areal density of the armor system a more than two-fold increase in kinetic energy protection level was achieved. Thickness of the fiberglass reinforced plastic backing material was increased to achieve an optimum ratio of ceramic thickness to backing thickness for the different ballistic defeat condition

Micro-Switches with Sputtered Au, AuPd, Au-on-AuPt, and AuPtCu Alloy Electric Contacts

This work is the first to report on a new analytic model for predicting micro-contact resistance and the design, fabrication, and testing of microelectromechanical systems (MEMS) metal contact switches with sputtered bi-metallic (i.e. gold (Au)-on-Au-platinum (Pt), (Au-on-Au-(6%)Pt)), binary alloy (i.e. Au-palladium (Pd), (Au-(2%)Pd)), and tertiary alloy (i.e. Au-Pt-copper (Cu), (Au-(5%)Pt-(0.5%)Cu)) electric contacts. The micro-switches with bi-metallic and binary alloy contacts resulted in contact resistance between 1-2 /spl Omega/ and, when compared to micro-switches with sputtered Au electric contacts, exhibited a 3.3 and 2.6 times increase in switching lifetime, respectively. The tertiary alloy exhibited a 6.5 times increase in switch lifetime with contact resistance ranging from 0.2-1.8 /spl Omega/

Development of impact resistant boron/aluminum composites for turbojet engine fan blades

Composite fabrication was performed by vacuum press diffusion bonding by both the foil-filament array and preconsolidated monotape methods. The effect of matrix material, fiber diameter, matrix enhancement, fiber volume reinforcement, test temperature, angle-plying, notch, impact orientation, processing variables and fabrication methods on tensile strength and Charpy impact resistance are evaluated. Root attachment concepts, were evaluated by room and elevated temperature tensile testing, as well as by pendulum-Izod and ballistic impact testing. Composite resistance to foreign object damage was also evaluated by ballistic impacting of panels using projectiles of gelatin, RTV rubber and steel at various velocities, and impingement angles. A significant improvement in the pendulum impact resistance of B-Al composites was achieved

Ballistic Limit Estimation Approaches for Ballistic Resistance Assessment

The armour technologist conducts ballistic impact testing either for evaluating armour materials and systems or for studying material’s defeating mechanism. Most standards make use of the ballistic limit velocity for ballistic assessment. This is the bullet impact velocity that leads to the protection perforation in 50 per cent of the cases. Various models have been emerged to estimate this key metric. The present article summarises the popular models developed for ballistic limit estimation. An attempt is made to point out models’ strength and weakness. First, the experimental set-up used for that goal is displayed. Next, a concise overview of ballistic limit estimation methods is presented. Lastly, a discussion is dedicated to model’s comparison and analysis. This literature survey reveals that the main drawback of already existing methods is that they are purely statistical. Moreover, existing methods are based on the normality assumption of perforation velocities which tends from -infinity to infinity. The main conclusion of this survey is that the presented methods offer a comparable accuracy in estimating the ballistic limit velocity. However, a given variability is remarked when extreme values estimation is of interest, impact velocities leading to low and high perforation probability. Finally, existing models’ performances decay with the reduction of the experimental sample size which represent a constraining requirement in ballistic resistance assessment

Structural Health Monitoring of M1114 High Mobility Multipurpose Wheeled Vehicle Armor System

The M1114 High Mobility Multipurpose Wheeled Vehicle (HMMWV) has been the workhorse vehicle of the U.S. Armed Forces in Afghanistan and Iraq. Donald Rumsfeld, Secretary of Defense, was faced with massive public criticism in 2004 for not equipping our military personnel in Afghanistan and Iraq with M1114s that had the proper ballistic armor. In May 2004, a $618M Senate Bill was passed to increase the production level of HMMWVs and improve their ballistic protection capabilities while minimizing additional weight. While the military is taking advantage of using composite armor on the HMMWV, it does not have a rigorous method to detect, locate, and quantify damage on a two-layer composite armor system. Structural Health Monitoring (SHM) is the process of implementing a damage detection and characterization strategy for engineering structures. Damage is defined as changes to the material and geometric properties of a structural system, including changes to boundary conditions and system connectivity, which adversely affect the system\u27s performance. An active SHM system was developed to detect, locate, and quantify damage on a two-layer composite armor (HJ1 composite with ceramic frontal plates) that encounters impact from a 0.30 caliber armor piercing projectile. An adaptive version of a one-at-a-time experiment was used during this research. Base line testing was performed to provide information on the structural properties and wave propagation characteristics of the material. Ballistic testing was completed to replicate David Fecko\u27s experiment of maximum V50 velocity of 947 meters per second and a ceramic-to-composite ratio of 60/40

An Inference about Interference: A Surprising Application of Existing International Law to Inhibit Anti-Satellite Weapons

This article presents a thesis that most readers will find surprising, in an effort to develop a novel, simultaneous solution to three urgent, complex problems related to outer space. The three problems are: a) the technical fact that debris in outer space (the accumulated orbital junk produced by decades of space activities) has grown to present a serious hazard to safe and effective exploration and exploitation of space; b) the strategic fact that many countries (notably the United States, China and Russia, but others, too) continue to demonstrate a misguided interest in pursuing anti-satellite weapons, which can jeopardize the security of space; and c) the political fact that attempts to provide additional legal regulation of outer space (via new bilateral or multilateral international agreements) have failed, with little prospect for prompt conclusion of meaningful new accords. The proposed solution is to adapt existing international law in an unforeseen way. Specifically, numerous current and historical arms control treaties provide for verification of parties’ compliance via “national technical means” (NTM) of verification, which prominently include satellite-based sensory and communications systems. These treaties routinely provide protection for those essential space assets by requiring parties to undertake “not to interfere” with NTM. The argument developed here is that additional tests in space of debris-creating anti-satellite weapons would already be illegal, even without the conclusion of any dedicated new treaty against further weaponization of space, because in the current crowded conditions of space, a new cloud of orbital debris would, sooner or later, impermissibly interfere with NTM satellites. If sustained, this thesis can provide a new rationale for opposition to the development, testing, and use of anti-satellite weapons. It a legal reinforcement for the political instincts to avoid activities that further undercut the optimal usability of outer space, and it demonstrates how creative re-interpretation of existing legal provisions can promote the advancement of the rule of international law, even in circumstances where the articulation of new treaties is blocked

Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing – An experimental study and analytical approach

AbstractHigh strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard (JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets

Enhanced Combat Helmet (ECH) Case Study

Mortlock, R. F. (2017, July). Enhanced combat helmet (ECH) case study, teacher’s edition, (NPS-AM-17-212); available upon request. This Enhanced Combat Helmet (ECH) case study encourages critical analysis of a U.S. Defense Department project at two key decision points: project start and production. The case centers on the development, testing, and procurement (also referred to as acquisition) of the ECH for U.S. Army Soldiers and U.S. Marines. Two things make this case study particularly interesting. First is that key project stakeholders are passionate about helmets because they save lives in combat and all Soldiers and Marines consider themselves subject matter experts on helmets, resulting in wide applicability. Second is the fact that the key decisions involved with the ECH effort involved ambiguous data within a complex acquisition environmentﾗrequiring decision making under uncertainty. The ECH case study reinforces critical thinking in uncertain environments, documents lessons learned for sound project management for future application, and provides wide private sector exposure to the complexities of public sector acquisition and helmet manufacture in particular.Naval Postgraduate School Acquisition Research ProgramNaval Postgraduate School Acquisition Research ProgramApproved for public release; distribution is unlimited

Optimization of Airfield Parking and Fuel Asset Dispersal to Maximize Survivability and Mission Capability Level

While the US focus for the majority of the past two decades has been on combatting insurgency and promoting stability in Southwest Asia, strategic focus is beginning to shift toward concerns of conflict with a near-peer state. Such conflict brings with it the risk of ballistic missile attack on air bases. With 26 conflicts worldwide in the past 100 years including attacks on air bases, new doctrine and modeling capacity are needed to enable the Department of Defense to continue use of vulnerable bases during conflict involving ballistic missiles. Several models have been developed to date for Air Force strategic planning use, but these models have limited use on a tactical level or for civil engineer use. This thesis presents the development of a novel model capable of identifying base layout characteristics for aprons and fuel depots to maximize dispersal and minimize impact on sortie generation times during normal operations. This model is implemented using multi-objective genetic algorithms to identify solutions that provide optimal tradeoffs between competing objectives and is assessed using an application example. These capabilities are expected to assist military engineers in the layout of parking plans and fuel depots that ensure maximum resilience while providing minimal impact to the user while enabling continued sortie generation in a contested region