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1
Hart, Shandon D. (Shandon Dee) 1978. "Multilayer composite photonic bandgap fibers." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32264.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (leaves 120-126).
Materials and fabrication techniques are developed that lead to the successful fabrication of multilayer composite photonic bandgap fibers. The pertinent background in electromagnetic theory of multilayer dielectric mirrors and optical fibers is surveyed. Materials properties constraints are outlined, with emphasis on those constraints related to processing strategy and ultimate target length scale. Interfacial energy is measured in a chalcogenide glass / organic polymer composite system selected for fiber fabrication. A classical capillary instability model is employed to predict the feasibility of fiber fabrication based on material properties; from this model, quantitative materials selection criteria related to ultimate length scale are derived. Good agreement is found between the calculated materials selection criteria and controlled fiber experiments. The fiber fabrication techniques are described and analyzed; chalcogenide film deposition is characterized using Raman and electron microprobe spectroscopy, and heat transfer during fiber drawing is modeled using a commercial finite-element software package. The developed materials and fabrication processes are used to perform two case studies in novel photonic bandgap fiber fabrication; the first case study deals with externally reflecting omnidirectional 'mirror-fibers', while the second deals with hollow- core light transmitting fibers. The reflecting mirror-fibers consist of a tough polymer core surrounded by multiple coaxial submicron-thick layers of a high-refractive-index glass and a low-index polymer; these layers reflect external light from all incident angles and polarizations in the mid-IR range.
(cont.) Large directional photonic gaps and high reflection efficiencies that are comparable to the best metallic reflectors were measured. In the second case study, the light-transmitting fibers consist of a hollow air core surrounded by multiple alternating layers of the same materials, resulting in large infrared photonic bandgaps. Optical energy is strongly confined in the hollow fiber core, enabling light guidance in the fundamental and up to fourth-order gaps. These gaps are placed at selectable wavelengths within a large selection range, from 0.75 to 10.6 m. Tens of meters of hollow photonic bandgap fibers designed for 10.6 pgm radiation transmission are fabricated. We demonstrate transmission of carbon dioxide (CO2) laser light with high power-density through more than 4 meters of hollow fiber and measure the losses to be less than 1.0 dB/m at 10.6 microns. Thus, fiber waveguide losses are suppressed by orders of magnitude compared to the intrinsic fiber material losses.
by Shandon D. Hart.
Ph.D.
2
Saillant, Jean-Francois. "Study of multilayer piezoelectric composite structures." Thesis, University of the West of Scotland, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.742766.
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Davis, Jill Benea. "Three-dimensional multilayer woven fabrics as composite preforms." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12437.
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Allen, Aaron Andrew. "Stability results for damped multilayer composite beams and plates." [Ames, Iowa : Iowa State University], 2009.
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Georgallides, Christoforos. "Design production assessment of multilayer fabrics for composite materials reinforcement." Thesis, University of Manchester, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603311.
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The aim of this project was to design, produce and assess multilayer fabrics with crosslinks or stitches between the individual layers so that the interlaminar shear properties of the composite panels reinforced with these fabrics would be improved. In fact, 12 fabric variants based on a 2-layer a-end satin fabric (with a more number 3Up) were produced on a 4x1 SAURER 100W Shuttleloom, which was modified in order to weave these fabrics. 3-D cellulorr fabrics with novel triangular cores were also woven on this shuttleloom. All of the 2-layer a-end satin fabric variants (including one non-stitched (weave No.9); five weft stitched (weave No.s 32,33,19,34,25); three warp stitched (weave No.s 36,37,29) ; and four weft and warp stitched fabrics (weaves Nos. 35,38,39,40) were assessed for their mechanical performance, particularly in Tensile and Interlaminar shear deformations. A geometrical model, "MAMCA" ("Major and Minor Circular Arc") model, was proposed in order to describe the yarn paths (warp and weft) in all the above fabric variants. using this model ("MAMCA"), the average breaking load of warp and the maximum initial angle between the warp yarn and the fabric axis (ximax.warp)' the theoretical breaking load along the warp direction was estimated for all 13 fabric variants tested. The theoretical values of the breaking load of the above fabric variants in the warp direction, were compared to the Experimental values obtained from Tensile strip strength Tests. There was a reasonable degree of agreement between these two sets of breaking load values. Thus, this method could be used to predict the breaking load of such fabrics in the appropriate loading direction.
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Fielder, Robert Stanley. "Computer Aided Design and Fabrication of Magnetic Composite Multilayer Inductors." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/36115.
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Computer modeling using finite element analysis (FEA) was performed to examine the effects of constructing multilayered thick film inductors using an artificially modulated magnetic composite structure. It was found that selectively introducing regions of low permeability material increased both the inductance and the current carrying capacity compared to thick film inductors made with single material magnetic cores. Permeabilities of the composite cores ranged from 1 to 220. The frequency for the models ranged from 0 to 5.0 MHz. Experimental devices were constructed using thick film screen printing techniques and characterized to validate the models and to determine the effectiveness of the design modifications. Quantitative comparisons were made between inductors of single permeability cores with inductors produced with magnetic composite cores. It was found that significant (> 130%) increases could be gained in saturation current with only a 12% decrease in inductance. It was found that the key parameters affecting performance were 1) the placement of low permeability regions, 2) the extent of non-uniform flux distribution within the structure, and 3) the volume fraction of low permeability material.Master of Science
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Wilkins, Ian. "Multilayer composite AZO / AGZO thin films for transparent conductive electrodes." Thesis, Wilkins, Ian (2016) Multilayer composite AZO / AGZO thin films for transparent conductive electrodes. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/40056/.
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Transparent electronics are an essential ingredient in many new technologies which are emerging in the 21st century - high efficiency solar cells [1, 2], interactive and transparent displays, energy efficient windows, and photonics for communications and computing [3]. The development of transparent conductors which are abundant, cheap and environmentally friendly, is critical for materials science in developing such applications. Specifically, an important research goal is to find substitutes for indium tin oxide (ITO) - the dominant transparent conductive oxide (TCO) material. ITO is a high performing and robust transparent conductor, but it is made from indium which is scarce, expensive and toxic. Zinc oxides doped with small amounts of aluminium (AZO), are promising candidates for such a substitute but generally don’t perform as well as ITO [3]. Gallium co-doping with aluminium improves AZO performance significantly, but raises similar concerns to ITO, in terms of the scarcity and high cost of gallium.
This project aims to enhance the conductivity of AZO thin films, by adding a thin middle layer, co-doped with Ga (AGZO). The project employed the solution based sol-gel technique for synthesising AZO and AGZO nanoparticles, and then deposited composite multi-layered thin films on glass substrates using a spin coating process. The optical properties, crystal structure and morphology of the films were characterised using UV-vis and FTIR spectroscopy, X-ray diffraction and Field Emission Scanning Electron Microscopy. Composite multilayer films were produced with thickness around 320nm, exhibiting transmittance above 90% across the visible range and resistivity approximately 10 Ωcm.
Results indicate significant improvement in AZO films, resulting from the addition of the co-doped AGZO mid-layer. The enhancement in performance recorded, was 4 similar to that found in uniformly doped AGZO films, except that the composite films contained only 20% of the gallium compared with the AGZO films. Due to the high cost of gallium, this presents the potential for significant reduction in the materials cost for TCO thin films.
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Karash, E. T. "Multilayer theory for delamination stresses in semicircular laminated composite curved bars." Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/25834.
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Composites laminates are widely used in both civil and military aircraft structures and gases cylinders leading to weight saving. However, study of the behaviour of such materials has shown that they are more damage sensitive than metallic material especially to delamination due to edge effect or low velocity impact [1]. In order to improve the performance of composite structures, advances must be made in the prediction of delamination growth and the evaluation of residual strength. The aim of this paper is to extend a delamination model valid for the plate in small displacement [2] or large displacement [3] to the case of curved structures as shells. Two kinds of approach are commonly used to study delamination growth, (i) the damage mechanics approach in which the interface enclosing the delamination is modelled by a damageable material Delamination is obtained when the damage variable reaches its maximum value [4 - 6] and (ii) the fracture mechanics approach which the present work is part.
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Jordan, Alex Michael. "FIBER-COMPOSITE IN SITU FABRICATION: MULTILAYER COEXTRUSION AS AN ENABLING TECHNOLOGY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1467832877.
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Tasdemirci, Alper. "Experimental and modeling studies of stress wave propagation in multilayer composite materials." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 11.67 Mb., 261 p, 2006. http://wwwlib.umi.com/dissertations/fullcit/3200525.
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Tung, Peter So Wah. "Design and development of three-dimensional multilayer woven preforms for composites." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/8686.
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Wu, Dongzhu. "SUBSTRATE DESIGN AND MEMBRANE STABILITY OF MULTILAYER COMPOSITE MEMBRANE FOR CO2 SEPARATION." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1510429230811329.
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Oguibe, Chukwuma Nnamdi. "A finite element study of the elastic-plastic indentation and the response of composite structural components to impact and impulse loading." Thesis, Leeds Beckett University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320299.
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Daines, Gregory Welch. "Evaluation of multilayer silicon carbide composite cladding under loss of coolant accident conditions." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103651.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 160-164).
Silicon carbide (SiC) has been proposed as an alternative to zirconium alloys used in current light water reactor (LWR) fuel cladding because it exhibits superior corrosion characteristics, high-temperature strength, and a 1000°C higher melting temperature, all of which are important during a loss of coolant accident (LOCA). To improve the performance of SiC cladding, a multilayered architecture consisting of layers of monolithic SiC (mSiC) and SiC/SiC ceramic matrix composite (CMC) has been proposed. In this work, the mechanical performance of both the tubing and the endplug joint of two-layer SiC cladding is investigated under conditions associated with the LOCA. Specifically, SiC cladding mechanical performance is investigated after exposure to 1,400°C steam and after quenching from 1,200°C into either 100°C or 90°C atmospheric-pressure water. The samples consist of two-layer SiC, with an inner SiC/SiC CMC layer and an outer monolith SiC layer. The relationship between mechanical performance and sample architecture is investigated through ceramography and internal void characterization. The two-layered SiC cladding design offered an as-received failure hoop stress of about 600 MPa, with little strength reduction due to thermal shock, and the tube failure hoop stress remained above 200 MPa after 48 hour high-temperature steam oxidation. The cladding showed pseudo-ductile behavior and failed in a non-frangible manner. The designs investigated for joint strength offered as-received burst strength above 30 MPa, although the impact of thermal shock and oxidation showed possible dependence on architecture. Overall, the cladding showed promising accident-tolerant performance. Because the implementation of SiC is complicated by the need for an open gap and low plenum pressure, thorium-based mixed oxides (MOX) are a promising fuel for SiC cladding because they have higher thermal conductivity and lower fission gas release (FGR). Previous efforts at MIT have modified the FRAPCON code to include thorium MOX fuel. In this work, the fission gas release and thermal conductivity models of FRAPCON-3.4-MIT are validated against published data. The results of this validation indicate a need to update the FGR model, which was accomplished in this work.
by Gregory Welch Daines
S.M.
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Audette, Scott. "Mechanical Properties of Aerospace Composite Parts Made from Stitched Multilayer 3D Carbon Fibre Preforms." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31691.
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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.
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Bell, Bryan Frederick. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131058/unrestricted/bell%5Fbryan%5Ff%5F200405%5Fms.pdf.
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Churilov, G. N., A. L. Kolonenko, A. I. Dudnik, T. A. Leonova, I. V. Osipova, N. G. Vnukova, and G. A. Glushenko. "Set-up for Nanosized Powder Synthesis and Set-up for Deposition of Composite and Multilayer Films." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35609.
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Set-up for nanosized powder synthesis and set-up for deposition of composite and multilayer films were described.
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Bell, Bryan Frederick Jr. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7962.
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Francart, Charles. "Experimental and numerical study of the mechanical behavior of metal/polymer multilayer composite for ballistic protection." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAD033/document.
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L’étude présentée porte sur le développement d’un modèle numérique destiné à évaluer les performances balistiques d’une structure multicouche polymère/métal frittée par procédé SPS. Les matériaux sont un alliage d’aluminium 7020 et un polyimide thermoplastique amorphe qui sont ensuite assemblés avec une résine epoxy. Le comportement mécanique de ces trois matériaux a été étudié sur de larges gammes de vitesses de déformations (de 0.0001 /s à 50.000 /s) et de températures (de -70°C à 500°C) correspondant aux conditions extrêmes rencontrées lors d’impacts à hautes vitesses. Afin d’améliorer la précision des résultats, des approches analytiques ont été développées autant pour la modélisation du métal que pour celle les polymères. Après la calibration des modèles, ces derniers ont été implémenté dans ABAQUS®/Explicit (éléments finis) via des subroutines VUMAT en code FORTRAN. Des essais d’impacts de billes à hautes vitesses ont été réalisés sur des cibles monocouches pour valider les modèles numériques. De nombreuses configurations de composites multicouches ont ensuite été étudiées numériquement et leurs performances balistiques ont été comparéesThe present study deals with the development of a numerical model to evaluate the ballistic performance of a polymer/metal multilayer structure sintered by SPS. The materials are an aluminum alloy 7020 and an amorphous thermoplastic polyimide which are then assembled using an epoxy resin. The mechanical behavior of these three materials has been studied over wide ranges of strain rates (from 0.0001 / s to 50,000 / s) and temperatures (from -70 °C to 500 °C) corresponding to the extreme conditions encountered during impacts at high velocities. In order to improve the accuracy of the results, analytical approaches have been developed both for the modeling of the metal and for the polymers. After the calibration of the models, these models were implemented in ABAQUS® / Explicit (finite elements) via VUMAT subroutines in FORTRAN code. Ball impact tests at high velocities were performed on monolayer targets to validate numerical models. Numerous configurations of multilayer composites were then studied numerically and their ballistic performances have been compared
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Lee, Sangjin. "Structure-Property Relationships in Composite Layers Polymeric Film/Foam Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1473444646138984.
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Liu, Yang, and Rui Wang. "Finite element analysis of the effects of theCu:CNx nano-composite multilayer coating onto the improvement of cutting tool life." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300140.
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To verify the effects of applying the shim with nanostructured composite damping coating onto the improvement of cutting tool life, the thesis studies two related aspects, the experiment and finite element software simulation. The experiment part mainly discusses the methods of designing the experiment process and verifying the damping vibration effectiveness of the coated shim. It gives a brief introduction to the experiment, including the procedures and the results. During the experiment, the traditional shim and the shim with nanostructured composite damping coating-CuCNx were turned respectively under the condition that the turning process remains the same, and the results were tested and checked by two methods. Firstly, the PSD of acceleration data in cutting tangential direction was recorded in real time by LMS software. Secondly, the flank wear of the tool was observed with optical microscope every 10 minutes. The results showed that the coated shim can effectively reduce the tool vibration and prolong the tool life, which is convincing evidence of the damping effect of nano composite coating. In the simulation part, ABAQUS software was used for the 3D Finite Element Analysis simulation. Instead of applying the common orthogonal cutting simulation model, the research used the real partsize and real machining parameters from the experiment for simulation. In addition, this part also introduces the methods of establishing the finite element model and setting the parameters in the software. The possible error messages and the reasons for the simulation failure would also be listed. Given that the simulation calculation continues to be optimized and completed, the thesis compares the stress levels on the insert with different shim conditions. The stimulation results showed that the stress was decreased with the application of the coating shim on the model of the cutting tool, proving that the composite coating of the shim can effectively expand the tool life. This thesis discusses the feasibility and reliability of using Finite Element Analysis simulation to analyze the cutting process, as well as verifying the effect of the coated shim.
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Sibanda, Wilbert. "Comparative study of neural networks and design of experiments to the classification of HIV status / Wilbert Sibanda." Thesis, North West University, 2013. http://hdl.handle.net/10394/13179.
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This research addresses the novel application of design of experiment, artificial neural net-works and logistic regression to study the effect of demographic characteristics on the risk of acquiring HIV infection among the antenatal clinic attendees in South Africa. The annual antenatal HIV survey is the only major national indicator for HIV prevalence in South Africa. This is a vital technique to understand the changes in the HIV epidemic over time. The annual antenatal clinic data contains the following demographic characteristics for each pregnant woman; age (herein called mother's age), partner's age (herein father's age), population group (race), level of education, gravidity (number of pregnancies), parity (number of children born), HIV and syphilis status. This project applied a screening design of experiment technique to rank the effects of individual demographic characteristics on the risk of acquiring an HIV infection. There are a various screening design techniques such as fractional or full factorial and Plackett-Burman designs. In this work, a two-level fractional factorial design was selected for the purposes of screening. In addition to screening designs, this project employed response surface methodologies (RSM) to estimate interaction and quadratic effects of demographic characteristics using a central composite face-centered and a Box-Behnken design. Furthermore, this research presents the novel application of multi-layer perceptron’s (MLP) neural networks to model the demographic characteristics of antenatal clinic attendees. A review report was produced to study the application of neural networks to modelling HIV/AIDS around the world. The latter report is important to enhance our understanding of the extent to which neural networks have been applied to study the HIV/AIDS pandemic. Finally, a binary logistic regression technique was employed to benchmark the results obtained by the design of experiments and neural networks methodologies. The two-level fractional factorial design demonstrated that HIV prevalence was highly sensitive to changes in the mother's age (15-55 years) and level of her education (Grades 0-13). The central composite face centered and Box-Behnken designs employed to study the individual and interaction effects of demographic characteristics on the spread of HIV in South Africa, demonstrated that HIV status of an antenatal clinic attendee was highly sensitive to changes in pregnant mother's age and her educational level. In addition, the interaction of the mother's age with other demographic characteristics was also found to be an important determinant of the risk of acquiring an HIV infection. Furthermore, the central composite face centered and Box-Behnken designs illustrated that, individual-ally the pregnant mother's parity and her partner's age had no marked effect on her HIV status. However, the pregnant woman’s parity and her male partner’s age did show marked effects on her HIV status in “two way interactions with other demographic characteristics”. The multilayer perceptron (MLP) sensitivity test also showed that the age of the pregnant woman had the greatest effect on the risk of acquiring an HIV infection, while her gravidity and syphilis status had the lowest effects. The outcome of the MLP modelling produced the same results obtained by the screening and response surface methodologies. The binary logistic regression technique was compared with a Box-Behnken design to further elucidate the differential effects of demographic characteristics on the risk of acquiring HIV amongst pregnant women. The two methodologies indicated that the age of the pregnant woman and her level of education had the most profound effects on her risk of acquiring an HIV infection. To facilitate the comparison of the performance of the classifiers used in this study, a receiver operating characteristics (ROC) curve was applied. Theoretically, an ROC analysis provides tools to select optimal models and to discard suboptimal ones independent from the cost context or the classification distribution. SAS Enterprise MinerTM was employed to develop the required receiver-of-characteristics (ROC) curves. To validate the results obtained by the above classification methodologies, a credit scoring add-on in SAS Enterprise MinerTM was used to build binary target scorecards comprised of HIV positive and negative datasets for probability determination. The process involved grouping variables using weights-of-evidence (WOE), prior to performing a logistic regression to produce predicted probabilities. The process of creating bins for the scorecard enables the study of the inherent relationship between demographic characteristics and an in-dividual’s HIV status. This technique increases the understanding of the risk ranking ability of the scorecard method, while offering an added advantage of being predictive.
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Huang, Jin. "Simulation du drapage des renforts de composites multicouches liés par piquage." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI098.
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De nos jours, les matériaux composites permettent de diminuer la masse des pièces et sont largement utilisés dans le domaine de l'aérospatial, de l'aéronautique et de l'automobile. De plus, les composites multicouches à renfort textiles permettent de la conception des structures épaisses telles que les aubes de la soufflante des réacteurs d'avion. Cependant, de nombreux défauts peuvent apparaître pendant le processus de mise en forme des renforts multicouches, comme des plissements. Des recherches sur la formation de plis, ainsi que sur la technique de piquage pour améliorer la propriété mécanique des renforts multicouches dans l'épaisseur sont présentées dans ce travail. La première partie de ce présent rapport consiste à étudier la formation de plis des renforts multicouches soumis à la flexion hors plan. Dans un premier temps, l'influence des différentes orientations des couches sur la formation de plis est explorée. La relation entre le chargement appliqué sur le tissu et la création de plissements est ainsi montrée. Le second chapitre consiste à comparer l'influence de deux types de tissage pour ce qui concerne la drapabilité du composite. La troisième partie propose deux modèles numériques adaptés pour simuler le drapage des renforts composites liés par piquage. Ces approches impliquent l'utilisation d'un élément fini de coque de type stress resultant pour représenter chaque couche de renfort et des éléments de barre pour représenter le fil de piquage. Ces modèles nécessitent un algorithme de contact propre pour gérer l'interaction entre le renfort et le fil de piquage. Enfin, la dernière partie consiste à valider les modèles par une comparaison entre les simulations et les essais expérimentauxNowadays, composite materials make it possible to reduce the mass of parts and are widely used in the aerospace, aeronautics and automotive industries. In addition, the multilayered reinforcement of composites allows the design of thick structures such as the fan blades of aircraft engines. However, many defects can occur during the forming process of multilayered reinforcements, such as the wrinkling problem. Research on the formation of wrinkles, as well as on the tufting technology to improve the mechanical property of multilayered reinforcements in the direction of thickness are presented in this work. The first part of this report is a study of the formation of the wrinkles of multilayered reinforcements subjected to out-of-plane bending. Firstly, the influence of the different orientations of the layers on the formation of wrinkles is explored. The relationship between the load applied to the fabric and the creation of wrinkles is thus shown. The second chapter compares two types of weaving pattern on the drapability of the composite. The third part consists of developing two numerical models adapted to simulate the forming of tuft-bonded composite reinforcements. These approaches involve the use of a stress resultant shell element to represent each layer of reinforcement and bar elements to represent the tufting yarn. These models require a specific contact algorithm to manage the interaction between the reinforcement and the tufting yarn. Finally, the last part consists of validating the models by comparing simulations and experiments
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森, 敏彦, Toshihiko MORI, 俊一 福田, Syun'ichi FUKUDA, 嘉彦 竹村, and Yoshihiko TAKEMURA. "Ti/TiN スパッタリング薄膜の多層化につれての機械的特性の向上." 日本機械学会, 2000. http://hdl.handle.net/2237/9035.
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Attar, Latifa. "Evaluation par ondes guidées de niveaux d'adhésion dissymétriques dans des collages structuraux métal-matériau composite. : Modélisation et approches des cas de Kissing Bonds." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH06/document.
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Cette thèse s'intéresse à l'évaluation de la qualité de l'adhésion dans des assemblages structuraux métal/adhésif/composite carbone-époxy, assemblages utilisés dans l'industrie automobile et aéronautique. La qualité du collage est évaluée par méthodes non destructives grâce à des ondes guidées ultrasonores de type Lamb et SH. Un nouveau modèle numérique par éléments finis a été développé au cours de ce travail : il s'agit d'un modèle rhéologique aux interphases qui permet de tracer les courbes de dispersion des modes guidés dans les échantillons étudiés. Il permet aussi de prédire l'évolution de l'amplitude de ces modes et la répartition de l'énergie dans la structure suivant le niveau d'adhésion ou la présence d'un défaut de type kissing bond. Des échantillons à niveau d'adhésion connus et maîtrisés sont réalisés avec l'aide de physico-chimistes, où l'époxy est partiellement ou totalement réticulé, et où l'interface substrat/adhésif a subi différents traitements chimiques. En particulier sont étudiés des échantillons dont la dégradation du collage dans la structure n'est pas symétrique. Les résultats expérimentaux sont confrontés à ceux issus du modèle numérique. Ces résultats montrent qu'il est possible de caractériser deux niveaux d'adhésion proches et aussi de déterminer sur quelle interface (métal/adhésif ou composite/adhésif) le collage a été dégradé. L'utilisation d'un banc de mesure à transducteurs électromagnétiques acoustiques (EMAT) a permis l'étude de l'amplitude des modes SH. Des variations importantes de l'amplitude de certains modes ont été constatées lors du passage de l'onde d'une zone de bonne adhésion à une zone où le collage est dégradéThis thesis focuses on the evaluation of the quality of adhesion in metal/adhesive/carbon-epox: structural assemblies used in the automotive and aerospace industry. The quality of the bonding i assessed by non-destructive methods using ultrasonic guided waves of the Lamb and SH types. A nev finite element numerical model was developed during this work: it is an interphase rheological mode that allows the dispersion curves of the guided modes to be plotted in the samples studied. It als( makes it possible to predict the evolution of the amplitude of these modes and the distribution o energy in the structure according to the level of adhesion or the presence of a kissing bond type defect. Samples with known and controlled adhesion levels are made with the help of physico chemists, 'where the epoxy is partially or totally crosslinked, and where the substrate/adhesivl interface has undergone different chemical treatments. In particular, samples are studied whos degradation of the bonding in the structure is not symmetrical. The experimental results are compare( with those from the numerical model. These results show that it is possible to characterize two clos levels of adhesion and also to determine on which interface (metal/adhesive or composite/adhesive the bonding has been degraded. The use of a measurement bench with electromagnetic acousti( transducers (EMAT) allowed thè study of the amplitude of the SH modes. Significant variations in th( amplitude of some modes have been observed when the wave passes from an area of good adhesioi to an area where the bonding is degraded
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Capron, Adélie. "Towards the predictive FE analysis of a metal/composite booster casing’s thermomechanical integrity." Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/314767/5/contratAC.pdf.
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In response to serious environmental and economic concerns, the design and production of aircrafts have been changing profoundly over the past decades with the nose-to-tail switch from metallic materials to lightweight composite materials such as carbon fibre reinforced plastic (CFRP). In this context, the present doctoral research work aimed to contribute to the development of a CFRP booster casing, a real innovation in the field initiated and conducted by Safran Aero Boosters. More specifically, this thesis addresses the matter of joining metal/CFRP hybrid structures, which are prone to possibly detrimental residual stresses.The issue is treated with an approach combining experimental characterisation and finite element (FE) simulations. The multi-layered system’s state of damage was systematically examined on hundreds of micrographs, and the outcome of this study is presented under the form of a statistical analysis. Further, the defects’ 3D morphology is investigated by incremental polishing. A number of thermal and mechanical properties are measured by diverse physical tests on part of the constituent materials, i.e. the aerospace grade RTM6 epoxy resin, the structural Redux 322 epoxy film adhesive, and AISI 316L stainless steel. They are used as input data in a FE model of the multilayer that is developed and progressively refined to obtain detailed residual stress fields after thermal loading. These results are compared to experimental data acquired by X-ray diffraction stress analysis and with the curvature-based Stoney formula. Cohesive elements are placed at specific locations within the FE model to allow simulating progressive damage. Peel tests, mode I, mode II and mixed mode I/II fracture tests are thus performed in view of measuring the joint toughness. The results of these tests are discussed and the presence of residual stress in the fracture specimens is highlighted. Key information for the calibration of the cohesive law is finally identified via inverse FE analysis of the mode I test, this being a significant step in the process of building a damage predictive FE model of the multi-layered system.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Graiff, Lorenzo. "Dispositivi protesici in Odontoiatria Digitale: dall'impronta digitale intraorale alla produzione con tecnologie Cad-Cam. Caratterizzazione in vitro della precisione di accoppiamento e delle proprietà meccaniche." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424453.
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The objective of this work is to study some various aspects of the modern digital workflow to produce Fixed Dental Prostheses (FDP): from the optical impression, directly in the mouth, to the finalization of the prosthetic device specific for the patient. The motivation of this study is related to the growing need around the dental world to optimize and modernize the workflows that are still essentially artisanal.
Taking advantage of modern digital technologies, that are rapidly spreading in the dental field, it is possible to obtain products with the highest quality standards, with lower production costs. Moreover it is important to spread the knowledge and skills to the dentists and to the dental technicians for an optimal use of these knowledges.
In particular, we have have taken into consideration the following issues of distinct particular clinical importance:
- optical intraoral scanning technology: specific operative and technical performance of these digital devices were investigated with particular reference to edentulous patients who need a full-arch implants rehabilitation,
- innovative ceramic materials, used to produce metalfree multilayer bridges on natural teeth using Cad-Cam technology. It was also investigated an innovative resin composite material, which is also workable with Cad-Cam technology and used for the production of single crowns on implants.
The revision of the scientific literature, suggested goals and metrological aspects of the experimental program of this research.
The investigations, have evaluated precision and accuracy aspects of the optical impression of implants position, the geometric coupling precision of the multilayer metal free bridge components, mechanical resistance of different types of materials, and adhesion between a recent Cad-Cam resin composite referred as, Resin Nano-Ceramic (RNC) and zirconia. Moreover the introduction of instruments and methods established in the technical-scientific field, has been provided suitable to characterize the manufacturing processes used, the materials used and the devices manufactured.
More in detail, the activities involved:
1. the study, in terms of metrological performance, of the acquisition process performed by the True Definition Scanner using a clinical sample reproducing a fully edentulous arch rehabilitated with 6 implants,
2. the verification of the geometric precision of the coupling component, sub and superstructure, of multilayer metalfree bridges made with different ceramic materials (zirconia-lithium disilicate), produced by Cad-Cam technology, and assembled by two different operators; the assembly / union of the bridge components, is instead carried out manually by the dental technicians totally handmade;
3. the analysis of the mechanical behavior, static, of the multilayer metalfree bridges, cited in paragraph 2, compared with another type of multilayer prosthesis (from the same Cad projects) but made with zirconia and glass ceramic (RLT),
4. the analysis by mechanical test, both static and under fatigue, of an innovative composite material resin supplied in blocks for Cad-Cam processing: Lava Ultimate. This new composite material presents, mechanical properties (Young's modulus), more similar to the natural tooth, compared to other aesthetic materials.
For this reason, it was used to produce single crowns on implants comparing two different modes of use: cementing a composite crown produced with Cad-Cam technology directly on a titanium standard abutment supplied by industry, or producing a Cad-Cam zirconia customized abutment and cementing the composite crown to this;
5.verification of bonding capacity between zirconia and Lava Ultimate, using two different resin cements by means of shear bond test.
Based on the results of the test campaigns conducted in this study it can be stated that:
1 technologies of digital intraoral optical impression are able to fulfill the clinical requirements of precision even in the case of full arch implants rehabilitations,
2. multilayer metalfree bridges, made with Cad-Cam technology according to the precision requirements of digital workflow, are affected by the intervention of the dental technician during the final assembly of the bridge components, resulting in reduced quality of precision established in the Cad phase,
3 multilayer metalfreee bridges show fracture toughness values greater than or equal to the minimum values reported in the scientific literature,
4. the implants crowns made with the innovative composite material subjected to strength tests and fatigue resistance, when cemented on an customized zirconia abutment, have superior mechanical characteristics than the cheapest solution, which provides the composite crown cementation directly to a standardized titanium abutment,
5. the use of adhesive cements for luting Lava Ultimate on zirconia, allowed to highlight the opposite results regards the strenght of adhesion, measured by means of the shear bond test.L’obiettivo di questo lavoro è studiare alcuni aspetti della moderna filiera produttiva digitale di manufatti protesici in campo dentale: dalla realizzazione dell’impronta ottica, direttamente nel cavo orale, alla finalizzazione del dispositivo protesico individualizzato per il paziente. La motivazione di questo studio risiede nell’esigenza sempre più sentita da parte di tutto il mondo dentale di ottimizzare e modernizzare i flussi di lavoro che sono ancora essenzialmente artigianali. Sfruttando le moderne tecnologie digitali, che si stanno rapidamente diffondendo in campo dentale, è possibile ottenere prodotti finiti di più alto standard qualitativo a fronte di costi di realizzazione più contenuti a condizione di diffondere ai clinici ed agli odontotecnici le conoscenze e le competenze necessarie all’utilizzo ottimale. In particolare sono stati presi in considerazione i seguenti temi di particolare rilevanza clinica: - la tecnologia di scansione ottica intraorale: sono state indagate le specificità operative e le prestazioni tecniche in particolare riferimento all’impiego per edentulie totali riabilitate mediante impianti, - i materiali ceramici innovativi, lavorabili mediante tecnologia Cad-Cam ed impiegati per realizzare protesi a ponte su denti naturali di tipo multilayer metalfree. E’ stato inoltre indagato un innovativo materiale in resina composita, anch’esso utilizzabile con tecnologia Cad-Cam ed impiegato per la realizzazione di corone singole su impianti. La revisione della letteratura tecnico scientifica, ha suggerito gli obbiettivi e gli aspetti metrologici del programma di ricerca sperimentale da condurre. Le indagini hanno riguardato aspetti di precisione ed accuratezza della lettura ottica della posizione degli impianti, di precisione geometrica di accoppiamento di protesi multilayer metal free, di resistenza meccanica di diversi tipologie di materiali e di adesione tra un recente composito a matrice resinosa, denominato Resin Nano-Ceramic (RNC) e zirconia; hanno previsto l’introduzione di strumenti e metodi consolidati in campo tecnico-scientifico, adatti a caratterizzare i processi di fabbricazione utilizzati, i materiali impiegati e i dispositivi realizzati. Più in dettaglio, l’attività ha riguardato: 1. lo studio, in termini di prestazioni metrologiche, del processo di acquisizione effettuato mediante il sistema di scansione True Definition Scanner su un campione clinico riproducente un'arcata completamente edentula riabilitata con 6 impianti; 2. la verifica della precisione geometrica di accoppiamento delle componenti, sotto e sovrastruttura, di protesi metalfree multilayer realizzate con materiali ceramici diversi (zirconia-disilicato di litio) prodotte mediante tecnologia Cad-Cam, e assemblate da due operatori diversi; l’assemblaggio/unione delle componenti, dei singoli ponti, viene invece realizzato manualmente dall’odontotecnico con tecnica totalmente artigianale; 3. l’analisi del comportamento meccanico, statico, delle protesi metalfree multilayer, citate al punto 2, confrontate con un altro tipo di protesi multilayer (provenienti dagli stessi progetti Cad) ma costituite da zirconia e ceramica feldspatica (RLT), 4. l’analisi mediante prova meccanica, statica e a fatica, della resistenza di un innovativo materiale in resina composita fornito in blocchetti per lavorazione Cad-Cam: Lava Ultimate. Questo nuovo materiale composito presenta, rispetto ad altri materiali estetici quanto a proprietà meccaniche dichiarate, (modulo di Young), un comportamento più simili al dente naturale. In quest’ottica, è stato utilizzato per realizzare corone singole su impianti, confrontando due modalità diverse di impiego: cementando una corona realizzata con questo composito e prodotta con tecnologia Cad-Cam direttamente su un pilastro standard in titanio fornito dall’industria, o realizzando con lavorazione Cad-Cam una sottostruttura in zirconia individualizzata e cementando su quest’ultima la corona in composito; 5. la verifica delle capacità adesive tra zirconia e Lava Ultimate, utilizzando due diversi cementi resinosi mediante test di taglio. Sulla base dei risultati delle campagne sperimentali condotte in questo studio è possibile affermare che: 1 le tecnologie di impronta ottica digitale intraorale sono in grado di rispondere ai requisiti clinici di precisione anche nel caso di arcate complete riabilitate su impianti, 2. le protesi multilayer metalfree, realizzate con tecnologia Cad-Cam secondo i requisiti di precisione propri dal workflow digitale, risentono dell’intervento di assemblaggio finale che esegue l’odontotecnico, con conseguente riduzione delle qualità di precisione stabilite in fase progettuale, 3. i ponti multilayer metalfreee presentano valori di resistenza alla frattura superiori o uguali ai valori minimi riportatati dalla letteratura scientifica 4. le corone su impianti realizzate con l’innovativo materiale composito, sottoposto a prove di resistenza statica e a fatica, quando cementate su un moncone individualizzato in zirconia, hanno caratteristiche meccaniche superiori alla soluzione più economica, che prevede la cementazione della corona direttamente ad un pilastro standardizzato in titanio. 5. l’utilizzo di cementi adesivi per cementare Lava Ultimate su zirconia, ha permesso di evidenziare comportamenti opposti per quanto riguarda le forze di adesione misurate con il test di taglio.
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Skinner, Anna Penn. "Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71683.
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Ionic polymer-metal composites (IPMCs) are widely studied for their potential as electromechanical sensors and actuators. Bending of the IMPC depends on internal ion motion under an electric potential, and the addition of an ionic liquid and ionic self-assembled multilayer (ISAM) conductive network composite (CNC) strongly enhances bending and improves lifetime.
Ion conducting polyelectrolytes poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and Nafion® were incorporated into an ISAM CNC film with poly(allylamine hydrochloride) (PAH) and anionic gold nanoparticles actuators to further improve bending. CNC films were optimized for bending through pH adjustments in PAH and adding NaCl to the PAMPS and Nafion® solutions. PAMPS-containing actuators showed larger and faster bending than those containing Nafion® in the CNC.
The IPMC actuator was also evaluated for its potential as a humidity sensor based on its relative humidity (RH) dependent steady-state current. The detection range is at least 10-80%RH, with 5%RH increment differentiation and likely better resolution. Effects of CNC presence and thickness were studied, in conjunction with ionic liquid at a range of RH values. A thin CNC (pH 4 PAH) produced the greatest current differentiation between RH values. The current's response speed to a large RH decrease was approximately 4 times faster than that of a fast commercial digital hygrometer. Additionally, the presence of a CNC and ionic liquid improved the current response time. These results indicate that an IPMC based humidity sensor using a CNC and ionic liquid is very promising and merits further study.Master of Science
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Marchetti, Fabien. "Modelling and characterisation of anisotropic multilayered plates on a wide frequency range." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI130.
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Le présent travail de thèse traite de la modélisation vibratoire et de la caractérisation dynamique de matériaux multicouches anisotropes. Dans le premier chapitre, une classification de quelques modèles analytiques de multicouche et techniques de caractérisation expérimentales de structures planes est établie sous la forme d'une synthèse bibliographique. Elle regroupe les récents résultats publiés autour du sujet. Le second chapitre propose une extension d'un modèle équivalent de multicouche au cas des structures anisotropes. Ce modèle décrit les premières courbes de dispersion de la structure et tient compte des phénomènes de cisaillement pouvant agir sur le mode de flexion en hautes fréquences. Le principal avantage du modèle réside dans sa simplicité et sa rapidité grâce à son nombre de variables cinématiques indépendant du nombre de couches. Les caractéristiques du multicouche sont définies par les 5 rigidités de flexion d'une plaque équivalente mince qui est comparée à ce dernier. L'extension de modèle est validée à l'aide d'une étude expérimentale réalisée sur des plaques composites en fibres de carbone. Un intérêt tout particulier est porté sur la modélisation de l'amortissement structurel. Une définition énergétique du facteur de perte, décrite par une formulation spatiale et temporelle de l'atténuation, est comparée à une définition équivalente. Une nouvelle définition de la formulation spatiale est proposée dans le cas de structures très amorties et est comparée aux résultats de la littérature. Dans le troisième chapitre, la technique de caractérisation RIC est étendue au cas des structures anisotropes. Cette méthode inverse s'appuie sur l'analyse du champ de déplacement de la structure et possède, grâce à son aspect local, des atouts non négligeables pour des applications industrielles. La méthodologie est tout d'abord présentée pour l'identification de sources (objectif initial de la méthode) et est ensuite adaptée à la caractérisation. Plusieurs applications numériques et expérimentales sont présentées afin de valider cette extension. Enfin, le quatrième chapitre porte sur la caractérisation expérimentale d'un sandwich en nids d'abeille sur une large bande fréquentielle (1 à 300 kHz). Le comportement dynamique complexe de cette structure épaisse est décrit au travers des résultats prometteurs fournis par les simulations de notre modèle et les estimations de RIC. Ces résultats sont également comparés à ceux d'un modèle de référence et d'autres méthodes de caractérisationThis PhD thesis concerns the modelling and the dynamic characterisation of anisotropic multilayered structures. In the first chapter, a classification of some analytical models and experimental methods of characterisation is presented in the form of a bibliographical synthesis where the main published results are gathered. The second chapter introduces an extension of an equivalent model of multilayered structures to the case of anisotropic materials. This model describes the first dispersion curves of the structure and considers the shear phenomena that can affect the bending mode in high frequencies. The main advantage of the model lies in its simplicity and rapidity thanks to a number of kinematic variables independent of the number of layers. The characteristics of the multilayer are defined by the 5 flexural rigidities of a thin equivalent plate which is compared to the multilayer. The results of the model are validated by means of an experimental study on carbon fiber composite plates. A particular interest is dedicated to the modelling of structural damping. An energetic loss factor, based on a temporal and spatial definition of the attenuation, is compared to an equivalent one. A new definition of the spatial attenuation is suggested for high damped structures and is compared to literature. In the third chapter, the methodology of the characterisation technique CFAT is adapted for anisotropic plates. This inverse method is based on the displacement field analysis of the structure and has, by means of its local aspect, relevant advantages for industrial applications. This adaptation is, as a first step, introduced for the identification of sources (initial objective of the method) and applied, in a second step, for the characterisation. Several numerical and experimental applications are presented to validate the results of the method. Finally, the fourth chapter deals with the experimental characterisation of a honey comb sandwich on a high frequency range (1 to 300 kHz). The complex dynamic behaviour of this thick structure is described through the promissing results given by the simulations of our model and the estimations of RIC. These results are also compared to the ones of a reference model and other characterisation methods
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Crisafulli, Daniela. "Advanced modelling of multilayered composites and functionally graded structures by means of Unified Formulation." Thesis, Paris 10, 2013. http://www.theses.fr/2013PA100055/document.
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La plupart des problèmes d'ingénierie des deux derniers siècles ont été résolus grâce à des modèles structuraux pour poutres, plaques et coques. Les théories classiques, tels que Euler-Bernoulli, Navier et de Saint-Venant pour les poutres, et Kirchhoff-Love et Mindlin-Reissner pour plaques et coques, ont permis de réduire le problème générique 3-D, dans le problème unidimensionnel pour les poutres et deux dimensionnelle pour les coques et les plaques. Théories raffinés d'ordre supérieur ont été proposées au cours du temps, comme les modèles classiques ne consentez pas à d'obtenir une complète domaine des contraintes et des déformations. La Carrera Unified Formulation (UF) a été proposé au cours de la dernière décennie, et permet de développer un grand nombre de théories structurelles avec un nombre variable d'inconnues principales au moyen d'une notation compacte et se référant à des nuclei fondamentales. Cette formulation unifiée permet de dériver carrément des modèles structurels d'ordre supérieur, pour les poutres, plaques et coques. Dans ce cadre, cette thèse vise à étendre la formulation pour l'analyse des structures fonctionnellement gradués (FGM), en introduisant aussi le problème thermo-mécanique, dans le cas des poutres fonctionnellement gradués. Suite à la formulation unifiée, les variables génériques déplacements sont écrits en termes de fonctions de base, qui multiplie les inconnues. Dans la deuxième partie de la thèse, de nouvelles fonctions de bases pour la modélisation des coques, qui représentent une approximation trigonométrique des variables déplacements, sont pris en compteMost of the engineering problems of the last two centuries have been solved thanks to structural models for both beams, and for plates and shells. Classical theories, such as Euler-Bernoulli, Navier and De Saint-Venant for beams, and Kirchhoff-Love and Mindlin- Reissner for plates and shells, permitted to reduce the generic 3-D problem, in onedimensional one for beams and two-dimensional for shells and plates. Refined higher order theories have been proposed in the course of time, as the classical models do not consent to obtain a complete stress/strain field. Carrera Unified Formulation (UF) has been proposed during the last decade, and allows to develop a large number of structural theories with a variable number of main unknowns by means of a compact notation and referring to few fundamental nuclei. This Unified Formulation allows to derive straightforwardly higher-order structural models, for beams, plates and shells. In this framework, this thesis aims to extend the formulation for the analysis of Functionally Graded structures, introducing also the thermo-mechanical problem, in the case of functionally graded beams. Following the Unified Formulation, the generic displacements variables are written in terms of a base functions, which multiplies the unknowns. In the second part of the thesis, new bases functions for shells modelling, accounting for trigonometric approximation of the displacements variables, are considered
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Wang, Lugen. "Ultrasonic Characterization of Multilayered Composites." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392038608.
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Zhou, Yijun. "Polymer-Ceramic Composites for Conformal Multilayer Antenna and RF Systems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1245240041.
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Waterton, Taylor Lindsey. "Design and manufacture of 3D nodal structures for advanced textile composites." Thesis, University of Manchester, 2007. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:151244.
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Traditional weaving technologies have been utilised over the past twenty-to-thirty years in producing woven textile components that meet engineering requirements through the interlacement of high performance yarns such as carbon, glass and Kevlar. The end performance properties and lightweight characteristics of these fabrics have been adapted within the development of both flat multilevel and shaped configurations for the composites industry. The purpose of the present research required the employment of conventional weaving technologies with limited modifications for the production of 3D woven textile preforms in a variety of truss like configurations; therefore, generating a generic procedure for all yarn combinations and strut and node dimensions for production on dissimilar jacquard looms. The ultimate driving force behind the research was to produce a truss like configuration for the aerospace industry incorporating the design criterion of solid and hollow woven counterparts. This would enable the end truss configuration to have two functions; the first being a lightweight structure by the elimination of bonding applications, through the utilisation of a fully integrated fabrication process; secondly to incorporate hollow struts for a novel storage solution.
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Мисловська, М. С. "Розрахунок статичних і динамічних характеристик модифікованої конструкції пристрою автоматичного врівноважуючого пристрою." Master's thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/71740.
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Об’єкт дослідження – процес навантаження і деформування багатошарових композитних торових оболонок.
Мета роботи – полягає в розробці методики розрахунку термопружного напруженого стану композитних торових оболонок високого тиску.
Методи дослідження – для розв’язання термопружної незв'язаної задачі застосовуються метод сплайн-колокацій, метод Фур’є, метод рядів Тейлора, метод ортогональної прогонки. На основі даних методів cтворений алгоритм і мовою програмування VISUALFORTRAN складена програма розрахунку напружено-деформованого стану багатошарових торових оболонок від дії статичного та температурного навантаження. Для розв’язання деяких із розглянутих задач також використовувався метод скінченних елементів, який реалізовано в програмному комплексі ANSYS.
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Ulke-Winter, Lars. "Naturanaloge Optimierungsverfahren zur Auslegung von Faserverbundstrukturen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-220529.
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Die vollständige Ausnutzung des Leichtbaupotentials bei der Dimensionierung von mehrschichtigen endlosfaserverstärkten Strukturbauteilen erfordert die Bereitstellung von geeigneten Optimierungswerkzeugen, da bei der Auslegung eine große Anzahl von Entwurfsvariablen zu berücksichtigen sind. In dieser Arbeit werden Optimierungsalgorithmen und -strategien zur Lösung wissenschaftlicher Fragestellungen für industrielle Anwendungen bei der Konstruktion von entsprechenden Faserkunststoffverbunden entwickelt und bewertet. Um das breite Anwendungsspektrum aufzuzeigen, werden drei unterschiedliche repräsentative Problemstellungen bearbeitet. Dabei wird für Mehrschichtverbunde die Festigkeitsoptimierung hinsichtlich eines bruchtypbezogenen Versagenskriteriums vorgenommen, ein Dämpfungsmodell zur Materialcharakterisierung entworfen sowie eine bivalente Optimierungsstrategie zur Auslegung von gewickelten Hochdruckbehältern erstellt. Die Grundlage der entwickelten Methoden bilden dabei jeweils stochastische naturanaloge Optimierungsheuristiken, da die betrachteten Aufgabenstellungen nicht konvex sind und derartige Verfahren flexibel eingesetzt werden könnenThe full utilization of the light weight potential in the dimensioning of multilayer fiber reinforced composites requires suitable optimization tools, since a large number of design variables has to be taken into account. In this work, optimization algorithms and strategies for the solution of scientific questions for industrial applications are developed and evaluated in the design of corresponding fiber-plastic composites. In order to show the wide range of applications, three different representative topics have been chosen. It will carry out a strength optimization for multilayer composites with regard to a type-related failure criterion, devolop a damping model for material characterization and established a bivalent optimization strategy for the design of wound high-pressure vessels. The developed methods are based on stochastic natural-analog optimization heuristics, since the considered tasks are not convex and such methods can be used in a very flexible manner
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Kasichainula, Sridhar. "Multilayered ceramic/metal composites by extrusion freeform fabrication." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/280308.
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Metal layers within a laminar ceramic can improve damage tolerance of ceramics by arresting large cracks either by ductile bridging or by crack deflection at the ceramic/metal interface, which will allow engineers to design reliable ceramics for structural applications. At low volume fractions of the metal ductile bridging is not very effective, mainly owing to decreased distance between the crack tip and next ceramic layer. Significant increase in the energy absorption during fracture can come from delamination, but depends on the interfacial fracture resistance. A two-fold increase in energy absorption is realized in the case of glass-ceramic/silver laminates prepared by extrusion freeform fabrication. Interfacial fracture energy for glass-ceramic/silver is found to be 100 J/m² in comparison to 15 J/m² for glass-ceramic/SiC, which should explain the sporadic crack deflection in notched four-point bend. For a short beam flexural test shear failure is more favorable in four-point than in three-point bending. In four-point tests, the shear stresses between the outer and inner loading pins can precipitate shear delamination prior to tensile cracking of the layers. Damage modes under low velocity impact tests are similar to four-point bend showing delamination as primary energy dissipation mechanism.
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Bordeaux, Frédéric. "Mélange atomique exothermique et amorphisation en phase solide dans des composites de multicouches fines métal-métal préparés par co-laminage." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0108.
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Etude des reactions exothermiques de melange atomique et d'amorphisation par reaction en phase solide dans des composites de multicouches fines metal-metal fabriques par co-laminage de rubans de materiaux purs ou d'alliages amorphes ou cristallises. La simulation numerique des reactions exothermiques est comparee aux resultats experimentaux et les utilisations possibles de ces composites en tant que fusibles de coupe circuit et alliages de brasure sont detaillees
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Overman, Nicole Rebecca. "Yielding and fracture in nanolayered metallic composites." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/n_overman_061709.pdf.
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Thesis (M.S. in materials science and engineering)--Washington State University, August 2009.Title from PDF title page (viewed on Aug. 10, 2009). "School of Mechanical and Materials Engineering." Includes bibliographical references.
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Mishra, Dibyajat. "Modeling, design, fabrication and demonstration of multilayered ferromagnetic polymer-dielectric composites for ultra-thin high-denisty power inductors." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54333.
Full textAbstract:
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.
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Wang, Yuxin. "Processing, Structure and Properties in Layered Films and Clay Aerogel Composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1332268511.
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Barton, Craig Wesley. "Anisotropy tuning in Co/Pd multilayers : for application in exchange-springs." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/anisotropy-tuning-in-copd-multilayers-for-application-in-exchangesprings(ef80ecc0-ad00-470f-8bd1-7bd39ade415e).html.
Full textAbstract:
Exchange–spring systems have been proposed as one method of addressing the media trilemma, where a balance must be maintained between thermal stability, writeability and signal to noise ratio. High anisotropy films coupled to low anisotropy films, in bit patterned media (BPM), via the exchange interaction allow the reversal mechanism to be tailored such that thermal stability is maintained whilst the switching field remains realisable in terms of available write elements. Understanding how the exchange interaction is mediated by through exchange break layers (EBL) is key in successfully creating an optimal exchange spring structure based on Co/Pd thin films for applications such as BPM.The work presented in this thesis shows that the perpendicular magnetic anisotropy (PMA) ofCo/Pd magnetic multilayers can be tuned by varying the Ar ion energy during deposition, usingremote plasma sputtering. This provides a novel method of tailoring the PMA without affecting the film composition and reduces the need for post fabrication processing. It is demonstrated that the reduction in PMA is due to chemical intermixing at the multilayer interface as the Ar ion energy is increased. This provides a method of creating two phase or graded exchange–spring materials for data storage or spin torque applications. In–situ anisotropy tuning was used to create hard and soft magnetic phases using Co/Pd multilayers to explore the effect of an exchange break layer (EBL) on exchange coupling. The relative coupling was investigated using Pd and Ta as the exchange break layer in two–phase anisotropy systems. The exchange–spring effect was found to extend 4 nm in the case of a Pd, whereas in the case of a Ta EBL only a 0.5 nm layer exhibited the same effect. These results highlight the importance of the choice of material for the EBL on the effective performance of the exchange–spring.
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Wang, Ruifeng. "Three-Dimensional Finite Element Modeling of Multilayered Multiferroic Composites." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1311365854.
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Sun, Mingze. "STRUCTURE, PROPERTIES AND APPLICATIONS OF LAYERED MATERIALS:MULTILAYERED FILMS AND AEROGEL COMPOSITES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1512489068284179.
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Wang, Lugen. "Elastic wave propagation in multilayered anisotropic media with applications to composite /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486401895209331.
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Akasheh, Firas. "Size effects and deformation mechanisms in nanoscale metallic multilayered composites." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Spring2007/F_Akasheh_050107.pdf.
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Kleicke, Roland, Adil Mountasir, Chokri Cherif, Gerald Hoffmann, and Christian Franz. "Thermoplastic fiber-reinforced composites based on noncrimped and multilayered weaves." Sage, 2014. https://tud.qucosa.de/id/qucosa%3A35637.
Full textAbstract:
Manufacturing of thermoplastic composite based on textile preforms made from hybrid yarns is well suited for the production of fiber-reinforced plastic (FRP) in medium- and large-scale production runs. Especially, the consolidation of thermoplastic FRP is currently complicated by the high viscosity of molten material. Woven multilayered and z-reinforced NCF-preforms are very interesting for FRP supposed to withstand threedimensional loading and impact stress. These preforms with z-directional reinforcement improve the FRP delamination behavior and out-of-plane characteristics. The wellknown composite parameters are essential to ensure the use of these materials in a wide range of applications.
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Salamone, Sam. "Densification of and constitutive laws for ceramic matrix composites and multilayered systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10585.
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Trotter, Heather Ann. "Preparation and evaluation of polymer composite multilayers on SiO₂ for use in medical systems." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010535.
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Yang, Wei. "Interaction of acoustic waves and anisotropic multilayered composite plates immersed in water." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186960.
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In this dissertation a theoretical analysis of elastic wave propagation in multilayered anisotropic composite plates is presented. Reflection and transmission coefficients as a function of the plane wave incident angle and ultrasonic wave frequency are computed for single layered and multilayered plates. From the minima of the reflection spectra one can obtain the Lamb wave modes. Computation of the displacement and stress components inside the plate show that different Lamb wave modes excite different levels of energy at various depths of the plate. These modes can be effectively used to detect and image defects in different layers of a plate. Theoretical predictions have been qualitatively verified experimentally by imaging internal defects inside different layers of a multilayered composite plate by different Lamb wave modes. Numerical precision problems associated with such analyses have been completed avoided for an unidirectional composite plate by solving the problem by symbolic programming instead of conventional numerical matrix manipulation technique.
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Wang, Xiaohua. "Stress and reliability analysis of multilayered composite cylinder under thermal and mechanical loads." Diss., Virginia Polytechnic Institute and State University, 1992. http://hdl.handle.net/10919/49934.
Full textAbstract:
The coupling resulting from the mutual influence of material thermal and mechanical parameters is examined in the thermal stress analysis of a long, hollow, multilayered, isotropic composite cylinder subjected to sudden axisymmetric external and internal temperature. The method of complex frequency response functions together with the Fourier transform technique is utilized.
Because coupling parameters for some composite materials, such as carbon-carbon, are very small, the effect of coupling is neglected in the orthotropic thermal stress analysis. The stress distributions in long, hollow, multilayered orthotropic cylinders subjected to sudden axisymmetric temperature loading combined with dynamic pressure as well as asymmetric temperature loading are also obtained. The method of Fourier series together with Laplace transform is utilized in solving the heat conduction equation and thermal stress analysis. The inertial term is considered and the perturbation technique is applied to cylinders subjected to dynamic pressure loading.
For brittle materials, like carbon-carbon composite, the strength variability is represented by two or three parameter Weibull distributions. The “weakest link" principle which takes into consideration both the applied stresses and the effected volume of material is used in the reliability analyses for both the isotropic and orthotropic carbon-carbon composite cylinders.
The complex frequency response analysis is performed on a long hollow multilayed orthotropic cylinder under asymmetrical thermal load. Both deterministic and random thermal stress and reliability analyses can be based on the results of this frequency response analysis.
The stress and displacement distributions and reliability of rocket motors under static or dynamic line loads are analyzed by an elasticity approach. Rocket motors are modeled as long hollow multilayered cylinders with an air core, a thick isotropic propellant inner layer and a thin orthotropic kevlar-epoxy case. The case is treated as a single orthotropic layer or a ten layered orthotropic structure. Five material properties and the load are treated as random variables with normal distributions when the reliability of the rocket motor is analyzed by the first-order, second-moment method (FOSM).Ph. D.
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