The objective of this investigation is to predict the residual strength of notched composite Iaminates with various layups, subjected to low frequency fatigue loading with constant amplitude at room temperature, by using a material modeling approach, fracture and fatigue mechanics and the finite element method (FEM). For simplicity, after thousands of cycles, the geometry of a circular hole of the deformed laminate was categorized as (1) uniformly expanded hole into elliptic shape, (2) crack propagation around the hole transversely. Both types were studied for 12 cases of layups with various proportions of 0, 45, -45 and 90 degree plies. The effect of geometry change during fatigue on residual strength was attributed to the elliptical hole, longitudinal splitting, matrix cracking (reduction moduli of plies), crack propagation and local delamination. Due to the thin through-the-thickness notched laminate, two-dimensional FEM was used and interlaminar stresses were not considered. Reduction of stress concentration is a reason for the increase of the residual strength of the notched laminate. The stress concentration factor decreases while the elliptic hole becomes more slender; that was examined by the FEM. The residual strength and stiffness were determined by the material modeling with moduli reduction and damaged zone, and the numerical result was obtained by FEM. Laminate theory, point stress criterion, polynomial failure criterion, ply discount method, and fatigue and fracture mechanics (Paris' Power Law) were also included in this research. Geometry change and moduli reduction are two major effects that are considered to predict the notched strength. The WN point stress fracture model is adopted for simplicity, instead of the average stress criterion. K_tg that corresponds to the unnotched strength in the normalized stress base curve is used to obtain the characteristic length (d_o). We find that K_tg decreases when the elliptic hole becomes more slender and more moduli are reduced (more plies crack). At the time d_o that is determined from K_tg in the base curve is not necessarily a fixed material constant. The correlation between the fatigue life and the residual strength as predicted by the model and those determined numerically is found within acceptable errors in comparison with the experimental data. / Ph. D.

Prestressing a steel girder reduces the required structural steel weight, limits tension stresses in the section, increases the ultimate strength, and increases the fatigue resistance. The technique of prestressing with tendons can be used for strengthening of existing bridges as well as for construction of new bridges. This thesis presents an analytical study of the behavior of simply-supported and continuous prestressed composite girders and describes the benefits of prestressing steel in composite construction. Analytical models are developed and used as a basis for a computer program that calculates the stresses and displacements in the cables and the girder at discrete number of nodes along the length of the girder. The effects of design variables such as prestress force, tendon profile, eccentricity and tendon length are studied. The results indicate that prestressing is an effective means of increasing the load carrying capacity of simple-span as well as continuous composite girders.

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Vascularized composite allotransplantation (VCA) has emerged over the last two decades as a promising therapeutic option for persons who have suffered the loss of limbs or who have suffered major facial disfigurement. Despite the clear advantages of facial and upper extremity VCA in terms of function and cosmesis, VCA has elicited a great deal of ethical concern. Much of that concern is centered around whether or not persons should be exposed to the toxic side effects and possible shortening of life associated with immunosuppression as part of treatment for conditions which are not life-threatening. Ethical concern has also been raised about the vulnerability, dignity and autonomy of VCA candidates and about the justice of allocating the necessary resources to research a treatment that seems unlikely to become widely available in the foreseeable future. <br>While this dissertation will demonstrate familiarity with the technical aspects of VCA, and with the ethical issues just mentioned, its focus will be on the implications of this new therapeutic option for the manner in which consent is understood. In particular, it will argue that the nature and duration of the treatment involved in upper extremity and face transplants makes necessary some modification to the theory and practice of consent. The concept of covenant will be put forward as a resource for this modification. Covenants, as agreements which establish and maintain on-going personal relationships of mutual obligation, are both durable and flexible. Covenants, by engaging persons affectively, promote commitment and encourage the formation of strong therapeutic alliances. Such alliances are especially fitting in light of the lengthy and demanding course of VCA, from screening through surgery and years of physiotherapy, maintenance of immunosuppression and self-monitoring for signs of rejection. <br>Covenant consent is needed for VCA because it more adequately describes what is being asked of recipients and what is necessary for the treatment to succeed. It is also needed because it appropriately honors the recipients by understanding them as active partners rather than as passive patients, and as people assuming major burdens and risks while contributing meaningfully to the development of the field. The employment of covenant consent significantly strengthens the ethical justification for vascularized composite allotransplantation of faces and upper extremities by acknowledging what is actually required of patients and by creating a structure through which they are supported in carrying out their commitment through the long, arduous period of rehabilitation and beyond. / McAnulty College and Graduate School of Liberal Arts; / Health Care Ethics / PhD; / Dissertation;

The emerging need for smart and wearable electronic systems are driving new electronics technology paradigms in miniaturization, functionality and cost.The operating voltages and power levels for devices in these systems are becoming increasingly varied with increased diversity of devices to serve these heterogeneous functions. Power convertor technologies are incorporated into various parts of these systems to step-up or step-down battery voltages and currents to address these diverse needs. Hence, multiple power converters, each requiring several passive components, are used to create stable power-supplies. This is placing significant challenges in ultra-miniaturized and ultra-efficient power management technologies. A typical power convertor consists of magnetic components such as inductors perform the basic energy storage and delivery functions from the source to the load. These power components are still at microscale in lithography and milliscale in component size. They occupy a large volume fraction of the power circuitry. Power convertors therefore, are a major bottleneck to system miniaturization. There is, thus, a need for ultra-miniaturized and high-performance power inductors for scaling down such power convertors. The critical parameters governing the size and performance of power inductors are its inductance density and power handling capability. These parameters are limited by the magnetic properties of the present inductor core materials. A new approach to inductor cores that achieves the best magnetic properties and yet allows integration of power inductors into ultra-thin substrates to meet the emerging needs for performance and size is therefore required. The objective of this research is to model, design and synthesize a novel multilayered ferromagnetic-polymer composite structure for inductor cores with high permeability and saturation magnetization.The multilayered composite structure consists of thin magnetic layers interspersed with ultra-thin polymers. A fabrication approach to integrate the composite structure in inductor devices is also demonstrated.

<p>Pitch and heave are limiting motions when driving at high speed on water. The installation ofa T-foil is an effective solution that reduces these motions. Commercial T-foils are available,but today none of them are non-magnetic. This thesis studies the possibility to design anon-magnetic T-foil that can carry the considerable loads that such a constructionexperiences. The T-foil is designed for vessels such as the Visby Class corvette.</p><p>Vortex lattice theory is used to calculate the pressure distribution acting on the construction atdifferent load cases. Required laminate thickness is determined by iteration using a linearfinite element model of the fin.</p><p>The conclusion is that it is possible to manufacture a non-magnetic T-foil of the required size.A critical area in the construction is the T-joint between the vertical strut and the horizontalfoil. Future investigations should include laboratory tests of the T-joint as well as moredetailed hydrodynamic analysis for more accurate input parameters of the T-foil.</p>

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