The increasing demand for polymer matrix composites (PMCs) from the airframe industry raises the issues of productivity, cost and reproducibility of manufactured PMC components. Performance reproducibility is closely related to the manufacturing technique. Resin transfer moulding (RTM) offers the advantage of flexible manufacturing of net-shape PMC components with superior repeatability starting from ready-to-impregnate dry reinforcements. An RTM apparatus was developed for manufacturing PMC plates and demonstrator components representative of actual, PMC components and PMC moulds made and used in the airframe industry. The RTM process developed in this work involved making net-shape dry carbon fibre preforms and impregnating them an epoxy resin, targeting mould applications. Thermal repeatability of different net-shape PMC components manufactured using the RTM apparatus developed in-house was investigated. Effects of bonding an outer copper plate onto the PMC material, targeting mould applications known as integrally heated copper tooling (IHCT), were explored. Heat conduction through the PMC components was studied using simulation models validated by experimental data obtained primarily by thermography. Manufactured PMC components showed good repeatability, particularly in terms of thermal behaviour. The IHCT technique was found to be well suited for mould applications. Expected advantages of thermography were materialised. Finally, the simulation models developed were in good agreement with experimental data.

The increasing demand for polymer matrix composites (PMCs) from the airframe industry raises the issues of productivity, cost and reproducibility of manufactured PMC components. Performance reproducibility is closely related to the manufacturing technique. Resin transfer moulding (RTM) offers the advantage of flexible manufacturing of net-shape PMC components with superior repeatability starting from ready-to-impregnate dry reinforcements. An RTM apparatus was developed for manufacturing PMC plates and demonstrator components representative of actual, PMC components and PMC moulds made and used in the airframe industry. The RTM process developed in this work involved making net-shape dry carbon fibre preforms and impregnating them an epoxy resin, targeting mould applications. Thermal repeatability of different net-shape PMC components manufactured using the RTM apparatus developed in-house was investigated. Effects of bonding an outer copper plate onto the PMC material, targeting mould applications known as integrally heated copper tooling (IHCT), were explored. Heat conduction through the PMC components was studied using simulation models validated by experimental data obtained primarily by thermography. Manufactured PMC components showed good repeatability, particularly in terms of thermal behaviour. The IHCT technique was found to be well suited for mould applications. Expected advantages of thermography were materialised. Finally, the simulation models developed were in good agreement with experimental data.

According to the United States Department of Defense (DOD), as of 2013 there were over 12,000 DOD contractors supporting the U.S. mission in Iraq (DASD, 2013). This thesis explores the laws and legal systems that operate to keep contractors, and the companies that employ them, resistant to legal oversight. I ground my analysis in the 2007 Nisour Square massacre, exploring how every attempt to prosecute those responsible was doomed due to Blackwater’s legal position of being American-headquartered, hired by the State Department, privately owned, and operating in Iraq. I conclude that the legal indeterminacy of the US deployed security contractor normalizes violence towards Iraqi civilians while simultaneously downloading the risk and responsibility associated with the US war efforts onto the shoulders of individual contractors. Moreover, I suggest that this legal indeterminacy is of particular interest to geographers as it arises, in part, out of overlapping legal systems, jurisdictions, and authorities.

According to the United States Department of Defense (DOD), as of 2013 there were over 12,000 DOD contractors supporting the U.S. mission in Iraq (DASD, 2013). This thesis explores the laws and legal systems that operate to keep contractors, and the companies that employ them, resistant to legal oversight. I ground my analysis in the 2007 Nisour Square massacre, exploring how every attempt to prosecute those responsible was doomed due to Blackwater’s legal position of being American-headquartered, hired by the State Department, privately owned, and operating in Iraq. I conclude that the legal indeterminacy of the US deployed security contractor normalizes violence towards Iraqi civilians while simultaneously downloading the risk and responsibility associated with the US war efforts onto the shoulders of individual contractors. Moreover, I suggest that this legal indeterminacy is of particular interest to geographers as it arises, in part, out of overlapping legal systems, jurisdictions, and authorities.

abstract: The formation of dendrites in materials is usually seen as a failure-inducing defect in devices. Naturally, most research views dendrites as a problem needing a solution while focusing on process control techniques and post-mortem analysis of various stress patterns with the ultimate goal of total suppression of the structures. However, programmable metallization cell (PMC) technology embraces dendrite formation in chalcogenide glasses by utilizing the nascent conductive filaments as its core operative element. Furthermore, exciting More-than-Moore capabilities in the realms of device watermarking and hardware encryption schema are made possible by the random nature of dendritic branch growth. While dendritic structures have been observed and are well-documented in solid state materials, there is still no satisfactory theoretical model that can provide insight and a better understanding of how dendrites form. Ultimately, what is desired is the capability to predict the final structure of the conductive filament in a PMC device so that exciting new applications can be developed with PMC technology. This thesis details the results of an effort to create a first-principles MATLAB simulation model that uses configurable physical parameters to generate images of dendritic structures. Generated images are compared against real-world samples. While growth has a significant random component, there are several reliable characteristics that form under similar parameter sets that can be monitored such as the relative length of major dendrite arms, common branching angles, and overall growth directionality. The first simulation model that was constructed takes a Newtonian perspective of the problem and is implemented using the Euler numerical method. This model has several shortcomings stemming majorly from the simplistic treatment of the problem, but is highly performant. The model is then revised to use the Verlet numerical method, which increases the simulation accuracy, but still does not fully resolve the issues with the theoretical background. The final simulation model returns to the Euler method, but is a stochastic model based on Mott-Gurney’s ion hopping theory applied to solids. The results from this model are seen to match real samples the closest of all simulations. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

abstract: Nonvolatile memory (NVM) technologies have been an integral part of electronic systems for the past 30 years. The ideal non-volatile memory have minimal physical size, energy usage, and cost while having maximal speed, capacity, retention time, and radiation hardness. A promising candidate for next-generation memory is ion-conducting bridging RAM which is referred to as programmable metallization cell (PMC), conductive bridge RAM (CBRAM), or electrochemical metallization memory (ECM), which is likely to surpass flash memory in all the ideal memory characteristics. A comprehensive physics-based model is needed to completely understand PMC operation and assist in design optimization. To advance the PMC modeling effort, this thesis presents a precise physical model parameterizing materials associated with both ion-rich and ion-poor layers of the PMC's solid electrolyte, so that captures the static electrical behavior of the PMC in both its low-resistance on-state (LRS) and high resistance off-state (HRS). The experimental data is measured from a chalcogenide glass PMC designed and manufactured at ASU. The static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film is characterized and modeled using three dimensional simulation code written in Silvaco Atlas finite element analysis software. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities. The sensitivity of our modeled PMC to the variation of its prominent achieved material parameters is examined on the HRS and LRS impedance behavior. The obtained accurate set of material parameters for both Ag-rich and Ag-poor ChG systems and process variation verification on electrical characteristics enables greater fidelity in PMC device simulation, which significantly enhances our ability to understand the underlying physics of ChG-based resistive switching memory. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2014

The increasing demand for polymer matrix composites (PMCs) from the airframe industry raises the issues of productivity, cost and reproducibility of manufactured PMC components. Performance reproducibility is closely related to the manufacturing technique. Resin transfer moulding (RTM) offers the advantage of flexible manufacturing of net-shape PMC components with superior repeatability starting from ready-to-impregnate dry reinforcements. An RTM apparatus was developed for manufacturing PMC plates and demonstrator components representative of actual, PMC components and PMC moulds made and used in the airframe industry. The RTM process developed in this work involved making net-shape dry carbon fibre preforms and impregnating them an epoxy resin, targeting mould applications. Thermal repeatability of different net-shape PMC components manufactured using the RTM apparatus developed in-house was investigated. Effects of bonding an outer copper plate onto the PMC material, targeting mould applications known as integrally heated copper tooling (IHCT), were explored. Heat conduction through the PMC components was studied using simulation models validated by experimental data obtained primarily by thermography. Manufactured PMC components showed good repeatability, particularly in terms of thermal behaviour. The IHCT technique was found to be well suited for mould applications. Expected advantages of thermography were materialised. Finally, the simulation models developed were in good agreement with experimental data.

Producing composite parts using low-cost processes such as resin transfer moulding (RTM) has received much interest in the aerospace industry. RTM manufactured components require near net shape preforms which closely fit mould cavities. To reduce labour costs associated with composite production, automated preforming processes must be utilized. However, obtaining reproducible high quality preforms is required for manufacturing consistent high quality parts. Stitched multilayer 3D non crimp fabric preforms are well suited for automation and an investigation into quality and performance of components manufactured from these preforms is required. This thesis provides an initial evaluation of quality and mechanical properties of components made from stitched multilayer 3D non crimp fabric preforms using RTM. Similar sized flat plates of varying fibre volume fractions were manufactured to evaluate flexural modulus and strength, short beam shear strength and drop weight impact resistance of the material. Also, integral reinforced panels (IRPs) featuring a reinforcing section joined to a flat plate of varying laminating sequences were manufactured to evaluate debonding strength between sections. Optical microscopy was performed on component samples to determine quality based on void content and was found to be within acceptable limits for production composites. Flexural moduli were found to be comparable with theoretical expected values, however flexural strength was limited by the presence of transverse stitches. Short beam shear strength results showed high consistency between specimens, however were lower than comparable values found in literature. Impact specimens showed consistency among specimens, with greater damage resistance than comparable values found in literature. Determining debonding strength proved difficult as different failure modes were observed between IRPs, however, initial baseline values were acquired.

This study delves into the conflict landscape in the form of a case study of the Central African Republic, with a specific focus on the involvement of the private military company Wagner Group, framed within Mary Kaldor's theory of New Wars. The theory emphasises that since the 1990s wars have been carried out in the name of identity politics, are between the state and non-state actors, that violence is directed at civilians and that the global economy is a driving condition. These characteristics are generally true for the conflict in CAR. The Wagner Group's role remains largely unexplored within academic circles, necessitating a closer examination of its impact on conflict dynamics to better understand the broader implications for regional stability and global power dynamics. Since CAR became independent in 1960, CAR has been imprinted by armed conflict and widespread violence against civilians. In 2018 the government ceded parts of its monopoly on violence to the Wagner group through an agreement where the group protects the state in exchange for access to natural resources. The Wagner group's presence also contributes to increased regional conflict dynamics and can lead to increased violence and criminal activity.

In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response Group (MRG) at Virginia Tech had the primary responsibility to develop the models for long-term behavior, especially remaining strength and life. The MRG is also responsible for the characterization of the material system with a focus on the effects of time, temperature, and environmental exposure. The present work is part of this effort. The motivation to use a composite material in a non-bonded flexible riser for use in the offshore oil industry is put forth. The requirements for such a material are detailed. Strength analysis and modeling methods are presented with experimental data. The effect of matrix crystallinity on composite mechanical properties is shown. A new method for investigating matrix behavior at elevated temperatures developed. A remaining strength life prediction methodology is recalled and applied to the case of combined fatigue and rupture loading. / Master of Science