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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Modern High Density Digital Recorders (HDDR) are ideal devices for the storage of large amounts of digital and/or wideband analog data. Ruggedized versions of these recorders are currently available and are supporting many military and commercial flight test applications. However, in certain cases, the storage format becomes very critical, e.g., when a large number of data types are involved, or when channel-to-channel correlation is critical, or when the original data source must be accurately recreated during post mission analysis. A properly designed storage format will not only preserve data quality, but will yield the maximum storage capacity and record time for any given recorder family or data type. This paper describes a multiplex/demultiplex technique that formats multiple high speed data sources into a single, common format for recording. The method is compatible with many popular commercial recorder standards such as DCRsi, VLDS, and DLT. Types of input data typically include PCM, wideband analog data, video, aircraft data buses, avionics, voice, time code, and many others. The described method preserves tight data correlation with minimal data overhead. The described technique supports full reconstruction of the original input signals during data playback. Output data correlation across channels is preserved for all types of data inputs. Simultaneous real-time data recording and reconstruction are also supported.

A novel approach has been introduced in making flexible armor composites. Armor composites are usually made by reinforcing Kevlar fabric into the mixture of a polymer and nanoscale particles. The current procedure deviates from the traditional shear thickening fluid (STF) route and instead uses silane (amino-propyl-trimethoxy silane) as the base polymer. In addition, a cross-linking fixative such as Glutaraldehyde (Gluta) is added to the polymer to create bridges between distant pairs of amine groups present in Kevlar and silated nanoparticles. Water, silane, nanoparticles and Gluta are mixed using a homogenizer and an ultra-sonochemical technique. Subsequently, the admixture is impregnated with Kevlar - bypassing the heating and evaporating processes involved with STF. The resulting composites have shown remarkable improvement in spike resistance; at least one order higher than that of STF/Kevlar composites. The source of improvement has been traced to the formation of secondary amine C-N stretch due to the presence of Gluta. / by Vincent Lambert. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

O carbeto de boro é um material sintético com ligações químicas essencialmente covalentes, tem um alto ponto de fusão só é sinterizável em elevada temperatura. Possui excepcional dureza, baixa densidade, resistência a abrasão, elevada velocidade sônica e boas propriedades mecânicas, características ideais para as aplicações balísticas. Tem como principal característica a alta seção de choque para nêutrons térmicos para aplicações nucleares. O presente trabalho teve por objetivo avaliar as propriedades mecânicas do carbeto de boro, pela introdução de diferentes teores de diboreto de titânio, pela reação in situ com pós de carbeto de titânio, e adição do carbono durante a sinterização, em forno resistivo sem pressão e prensagem isostática a quente dos componentes cerâmicos. Em menores temperaturas valores obtidos da densidade teórica para o carbeto de boro puro, foram alcançados com o emprego do aditivo. Os resultados obtidos na sinterização mostram a eficiência da introdução do carbeto de titânio para o aumento da densificação do material. Com percentuais de 20% de carbeto de titânio, obteve-se os máximos valores para microdureza (HV) de 35 GPa e tenacidade a fratura (KlC) de 3,16 MPa.m1/2. Comprovadamente a dificuldade de sinterização em elevadas temperaturas, para maior densificação, de componentes cerâmicos de carbeto de boro pode ser minimizada com a introdução de percentuais de carbeto de titânio. / Boron Carbide is a synthetic material with essentially covalent chemical bonds with high fusion point. The main characteristics are: it is sintered at high temperature, high hardness, low density, abrasion resistant, high sonic velocity, good mechanical properties and high neutron absorption cross section (10BxC, x>4). Those features are ideal for ballistics applications. The aim of this study was to evaluate the changes in mechanical properties of Boron Carbide with different concentration of Titanium Diboride by reaction in situ with TiC powders. The addition of carbon during sintering without pressure and hot isostatic pressing of ceramic components was studied. At low temperatures, the nearly values for the theoretical density for pure Boron Carbide were obtained only with the use of additives. In sintering, the use of TiC increased Boron Carbide density. At concentrations up to 20% of TiC, the maximum values for hardness (HV) and fracture toughness (KlC) were obtained. With the introduction of different levels of additive, the difficulty of sintering at high temperatures was minimized and the density of ceramic components was maximized.

Modern ballistic armor can protect soldiers against gunfire and shrapnel. The added weight and movement restriction of armor on the extremities may negatively impact soldier performance. Loading the limbs with weight has been found to increase metabolic cost in locomotion and alter gait kinematics. It was hypothesized that increases in metabolic cost and alterations in gait kinematics would result from the use of extremity armor. Fifteen healthy U.S. Army men walked (1.34 m/s) and ran (2.46 m/s) on a level treadmill with three different levels of extremity armor configuration: a no armor condition (4.3 lbs) that consisted of minimal clothing, combat boots, and a helmet; a partial extremity armor configuration (27.2 lbs) that consisted of an armor vest and extremity armor on the upper arms and thighs plus the minimal clothing; and a full extremity armor configuration (29.2 lbs) that consisted of forearm and shank armor in addition to the partial extremity armor configuration. In walking and running on the treadmill, metabolic cost normalized to body mass increased significantly when extremity armor was worn, as compared to the no armor condition. No difference was found in metabolic cost scaled to total mass (body mass + mass of armor), indicating no effect of mass placement. When walking on the treadmill, double support time was the only temporal variable found to increase with use of extremity armor; no differences between partial and full armor configurations were found. Range of motion (ROM) of the ankle decreased in walking with extremity armor, while hip and knee ROMs increased with the use of extremity armor. In running, only hip ROM and trunk lean increased significantly with the use of extremity armor, while no difference was found between the two extremity armor configurations. In conclusion, use of extremity armor on soldiers walking and running on a level treadmill resulted in a metabolic cost increase as the mass of the armor increased and did affect gait kinematics. The distal placement of the armor on the extremities at the low mass tested did not significantly affect metabolic cost or gait kinematics.

This thesis aims to develop a design-oriented simulation approach for cloth analysis. Our approach is built on the framework of NURBS-based isogeometric analysis, which utilizes NURBS as the basis functions of analysis. NURBS is a class of parametric geometry to represent curves and surfaces in computer-aided design (CAD) programs. Recently, NURBS geometry has been used directly in analysis. The overall goal of this thesis is to develop a computation infrastructure that enables cloth analysis directly on NURBS geometry. The advantage of NURBS in the context of cloth modeling lies in the geometric smoothness. Using NURBS, it's easy to construct surfaces with C1 or higher order of continuity. Compared to C0 finite element geometry, the NURBS geometry is more effective in capturing wrinkles and folders of cloth, which are characteristics of cloth motion. The NURBS geometry enables the use of rotation-free Kirchhoff-Love shell. The rotation-free shell model not only saves freedoms, but also makes the contact/impact treatment much easier. The major contribution of this work is the development of a NURBS cloth modeling approach. The mechanical model of cloth and its implementation with NURBS geometry will be presented in detail. Proper constitutive laws are employed for fabric materials. Since NURBS geometry from CAD typically contains multiple patches and trimmed patches, a certain treatment is proposed so that geometry can be used directly in analysis. Another contribution of this work relates to a contact/impact algorithm. Contact problems in cloth simulation have been a bottleneck of continuum-based approach. Since the general contact method doesn't work well for cloth simulation, a special contact treatment is developed. The present contact model distinguishes three types of contact interactions. The first is the persistent contact force. This force in essence is the traditional penalty force, but is applied when a contact pair is within a separation tolerance instead of being penetrated. This essentially smears the abrupt contact reaction into a relatively smooth force defined only a small thickness. The second is trajectory impact, which deals with the reaction when impact occurs in a time step. The treatment ensures that a point stays on a same side of the surface it impacts on. The third is self-intersection. Intersection resorting force is introduced when the initial configuration has self-intersections, or when the trajectory impact force fails to eliminate all the collisions. We proposed a new method, the method of area minimization, to handle intersections. The contact models have been integrated into an operator-split integration algorithm. A notable feature of this integration is that the contact/impact response is singled out from the momentum equation. This work also proposes a continuum-based strain limiting scheme. Because the in-plane stiffness of cloth is much higher than the bending stiffness, numerical difficulty is encountered in either implicit or explicit time integration. The strain limiting is a numerical technique that formulates the in-plane response as a constraint problem to allow the use of lower in-plane stiffness. A number of examples are presented to show the performance of the proposed approach. In the wrinkling study, the simulated wrinkle pattern looks similar with the experimental results. In the contact study, it is found that the current method can accurately recover a constant contact pressure field (press patch test), can handle contacts of multi-layer folds and produce realistic draping effect. The intersection resolution method is illustrated to be robust to various kinds of intersections. The fast projection method can enlarge time steps while limiting the in-plane strain. The current method is also applied to the analysis of a soft armor. Beginning from CAD models the armor was put on the human body by a try-on simulation. In multi-layer models, the intersection resolution method is used to resolve the intersections between layers. Subsequently, cloth dynamics are simulated for different human motions. Mechanical indexes such as the extra torque caused by the armors, pressure force on the body, and stress in the armor are predicted. Parametric studies are performed to investigate the change in mechanical metrics under altered design parameters.

Traditional lightweight armor ceramics such as boron carbide (B4C) and silicon carbide (SiC) are used alone or together in varying amounts to create monolithic protective plates. These materials exhibit relatively small differences in hardness, flexure strength, and fracture toughness. Many of the routes taken during the synthesis of the powder and sintering of the plates using traditional ceramic processing techniques have long processing times, tend to leave asperities within the microstructure, and have unwanted secondary phases that lower the performance of these materials. In lieu of the incremental changes in the above properties, it is thought that adding diamond particulates to the ceramic matrix will dramatically improve the mechanical properties and overall performance. With the reduced cost of synthetic diamond and the commercial development of more rapid spark plasma sintering (SPS), this work develops a novel reactive SPS process to fabricate near fully dense SiC-TiC-diamond composites at various processing temperatures with minimal graphitization and full adhesion to the ceramic matrix. It was found that samples with up to ~97% theoretical density can be fabricated with no quantifiable graphite content within the characterization ability using advanced X-ray diffraction and microscopy techniques.

Thesis (doctoral)--Ethnikon kai Kapodistriakon Panepistēmion Athēnōn, Philosophikē Scholē. / Summary in English. Includes bibliographical references (p. xx-xxviii) and index.

The high strength, light weight, and flexibility of fabric protection systems makes them the preferred solution for a number of ballistic applications. Examples include body armor, fan blade containment for jet engines, and orbital debris shielding. In general, these protection systems employ plain woven fabric, most suitable for flat or gently curved geometries. Highly curved surfaces, such as personnel extremities, may be more effectively protected using fabrics of different weaves. This dissertation presents the first numerical model developed to simulate ballistic impacts into plain, harness satin, twill, and basket weave fabrics. It extends previous work on hybrid particle-finite element methods developed for fabric modeling. The extended formulation closely replicates the tensile load response and contact-impact dynamics of highly flexible yarns, by generalizing the kinematic model and density interpolation used in previous work. The formulation has been validated in three dimensional simulations of impact experiments conducted to investigate the effects of weave type on fabric ballistic performance. / text

The objective of this study is to develop a finite element model of the human thorax with a protective body armor system so that the model can adequately determine the thorax's biodynamical response from a projectile impact. The finite element model of the human thorax consists of the thoracic skeleton, heart, lungs, major arteries, major veins, trachea, and bronchi. The finite element model of the human thorax is validated by comparing the model's results to experimental data obtained from cadavers wearing a protective body armor system undergoing a projectile impact. When the model is deemed valid, a parametric study is performed to determine the components of the model that have the greatest effect on its biodynamical response to a projectile impact.