Approved for public release; distribution is unlimited / This thesis investigates the types of competition that exist during the different acquisition phase of a weapon system procurement, and discusses the possible effects that competition has on the acquisition cost of these systems. Also, economic, technical and management variables are presented and discussed that may have a significant impact when considering whether to introduce production competition into a program. Five second sourcing methodologies are presented and discussed along with their relative advantages and disadvantages, and a model is presented which allows for a comparison to be performed between the five second sourcing methods. The proposed acquisition strategy for the Advanced Assault Amphibian Vehicle (AAAV) is presented and analyzed as it concerns design and production competition. An analysis of the AAAV program variables is performed, with accompanying economic analysis, which indicates that a Contractor Teaming strategy would be appropriate for introducing production competition should the decision be made to second source. / http://archive.org/details/evaluationofcomp00corc / Captain, United States Marine Corps

Advanced impact protection systems can experience serious damage due to contact with projectiles such as fragments or entire fan blades. To prevent catastrophic damage of such systems will require sophisticated materials and complex designs. The development of advanced ballistic protection systems will place increased emphasis on the use of composite materials and on numerical simulations to assess these new systems due to the cost and limitations of testing facilities and the increased capability of computing power. Example applications include the design of body armor for the protection of personnel, the design of fragment containment systems for aircraft engines, and the design of orbital debris shielding for the protection of manned spacecraft. The current research has developed a new mesomechanical particle-element material model for woven material impact response, a velocity dependent friction model to simulate yarn interactions, and a strain rate dependent model for Kevlar. In recent research, a new class of shear-thickening fluid (STF) composites has been developed for use in impact protection systems. Advancements in the current work include a Bingham shear stress model for STF effects and a new mixture equation of state for the STF Kevlar that captures the thermodynamic properties of the constituents. The numerical methods and material model developed in this research have been validated through the simulation of three dimensional impact experiments on different Kevlar target geometries. This dissertation also provides new data for fragment simulating projectile impacts on Kevlar with different boundary conditions and new data for aluminum cylinder and steel disk projectile impacts on neat and STF Kevlar with different boundary conditions. / text

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Speyer, Robert; Committee Member: Judson, Elizabeth; Committee Member: Sanders, Thomas. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Abhandlung zur Erlangung der Doktorwürde--Zürich. / Vita. Bibliography: p. 99-105.

Thesis (doctoral)--Universität Basel, 1968. / Vita. Bibliography: p. 265-272.

Inaug.-Diss.--Heidelberg. / Lebenslauf. "Die gesamte arbeit wird als [38.] Band der Anglistischen forschungen ... unter dem tifel 'Die englischen angriffswaffen zur zeit der einführung der feuerwaffen (1300-1350)' veröffentlicht." "Literatur": p. [ix]-xvi.

In the past, personal body armor was constructed of simple plates of high- strength alloys. However, with the advancement of modern combat and weaponry, particularly armor-piercing ammunition, personal body armor has evolved into more complex and effective metal, ceramic, and composite structures. This paper lays the groundwork for experimental and modeling methods used to understand the effectiveness of new armor designs. Focusing on the first layer of modern body armor, the ”High Impedance” layer. Experiments measuring the change in velocity of bullets passing through aluminum and titanium plates were conducted. These experiments were then replicated through FEA simulation.

Boron carbide (B₄C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B₄C make it a nearly ideal material for personnel and vehicular armor. B₄C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B₄C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B₄C powders. The boron carbide powder examined in this study was a submicron (0.6 μm median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form ofphenolic resin, and titanium additives in the form of 32 nm and 0.9 μm TiO₂ powders were selected. Parametric studies of sintering behavior were performed via high-temperature dilatometry in order to measure the in-situ sample contraction and thereby measure the influence of the additives and their amounts on the overall densification rate. Additionally, broad composition and sintering/post-HIPing studies followed by characterization and mechanical testing elucidated the effects of these additives on sample densification, microstructure development, and mechanical properties such as Vickers hardness and microindentation fracture toughness. Based upon this research, a process has been developed for the sintering of boron carbide that yielded end products with high relative densities (i.e., 100%, or theoretical density), microstructures with a fine (∼2-3 μm) grain size, and high Vickers microindentation hardness values. In addition to possessing these improved physical properties, the costs of producing this material were substantially lower (by a factor of 5 or more) than recently patented work on the pressureless sintering and post-HIPing of phase-pure boron carbide powder. This recently patented work developed out of our laboratory utilized an optimized powder distribution and yielded samples with high relative densities and high hardness values. The current work employed the use of titanium and carbon additives in specific ratios to activate the sintering of boron carbide powder possessing an approximately mono-modal particle size distribution. Upon heating to high temperatures, these additives produced fine-scale TiO ₂ and graphite inclusions that served to hinder grain growth and substantially improve overall sintered and post-HIPed densities when added in sufficient concentrations. The fine boron carbide grain size manifested as a result of these second phase inclusions caused a substantial increase in hardness; the highest hardness specimen yielded a hardness value (2884.5 kg/mm²) approaching that of phase-pure and theoretically-dense boron carbide (2939 kg/mm²). Additionally, the same high-hardness composition exhibited a noticeably higher fracture toughness (3.04 MPa•m¹/²) compared to phase-pure boron carbide (2.42 MPa• m¹/²), representing a 25.6% improvement. A potential consequence of this study would be the development of a superior armor material that is sufficiently affordable, allowing it to be incorporated into the general soldier’s armor chassis.

Based on the underlying structure of fabric materials, a three-scale model is constructed to describe the mechanical behavior of fabric materials. The current model assumes that fabric materials take on an overall behavior of anisotropic membranes, so membrane scale is taken as the macroscopic or continuum scale of the model. Following the membrane scale, yarn scale is introduced, in which yarns and their weaving structure are accounted for explicitly and the yarns are modeled as extensible elasticae. A unit cell consisting of two overlapping yarns is used to formulate the weaving patterns of yarns, which governs the constitutive nonlinear behavior of fabric materials. The third scale, named fibril scale, zooms to the fibrils inside a yarn and incorporates its material properties. Via a coupling process between these three scales, the overall behavior and performance of the complex fabric products become predictable by knowing the material properties of a single fibril and the weaving structure of the fabrics. In addition, potential damage during deformation is also captured in the current model through tracking the deformation of yarns in fibril scale. Based on the multi-scale model, both static and dynamic simulations were implemented. Comparison between the static simulations and experiment demonstrates the model abilities as desired. Through the dynamic simulations, parameter research was conducted and indicates the ballistic performance and mechanical behavior of the fabric materials are determined by a combination of various factors and conditions rather than the material properties alone. Factors such as boundary conditions, material orientation and projectile shapes etc. affect the damage patterns and energy absorption of the fabric. / Mechanical Engieering

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