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Valença, Silvio Leonardo. "Estudo de envelhecimento e propriedades mecânicas de compósito epóxi reforçado com tecido plano de kevlar e híbrido vidro/kevlar". Universidade Federal de Sergipe, 2014. https://ri.ufs.br/handle/riufs/3463.
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The epoxy resin has a widespread use in the manufacture of polymer composites to obtain various elements of structural engineering. The overall objective of this research is to evaluate the effect of reinforcing fabric architecture fiber-based Kevlar 49 and glass S on the mechanical performance of composites with epoxy matrix. It was observed that the mechanical performance of the epoxy resin and the composite, after natural aging and in seawater at a temperature of 70 ° C. Three architectures are designed for the production of tissue related to the structural reinforcement of the composite element: only aramid (Kevlar 49), and hybrid Kevlar 49 and glass S; varying the type of yarn and intertwining of the composition (fiber content in percentage) in each frame. The composite plates were made by hand casting process with epoxy matrix reinforced with woven fabrics of Kevlar fiber and Kevlar hybrid/glass, according to an innovative architecture. The mechanical properties of the composites were determined by tensile, bending and impact carried out in parallel and perpendicular to the warp direction. We used scanning electron microscopy to observe the reinforcement and matrix fractures after the mechanical tests. The composites with hybrid structure of Kevlar/glass on reinforcing fabric showed the best results with respect to the specific strength and impact energy.A resina epóxi possui uma ampla utilização na fabricação de compósitos poliméricos, para obtenção de diversos elementos da engenharia estrutural. O objetivo geral desta Tese é avaliar o efeito da configuração do tecido de reforço à base de fibras de Kevlar 49 e vidro S no desempenho mecânico de compósitos com matriz epoxídica. Observou-se o desempenho mecânico da resina epóxi e do compósito, após envelhecimento natural ao ar livre e na água do mar sob temperatura de 70 ºC. Foram concebidas três configurações para produção do tecido referentes ao elemento de reforço estrutural do compósito: apenas em aramida (Kevlar 49), e híbrido de Kevlar 49 e fibra de vidro S; variando-se o tipo de entrelaçamento dos fios e composição (teor de fibra em percentual) em cada estrutura. Foram fabricadas placas do compósito pelo processo de moldagem manual com matriz epoxídica, reforçadas por tecidos planos em fibra de Kevlar, e híbrido Kevlar/vidro, de acordo com uma configuração inovadora. As propriedades mecânicas dos compósitos foram determinadas por ensaios de tração, flexão e impacto, realizados nas direções paralela e perpendicular ao urdume. Utilizou-se a microscopia eletrônica de varredura para observar as fraturas do reforço e matriz após os ensaios mecânicos. Os compósitos com estrutura híbrida de Kevlar/vidro no tecido de reforço apresentaram os melhores resultados com relação à resistência mecânica específica, bem como energia de impacto.
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Tomlinson, John Brian. "Studies of activiated carbon fibres". Thesis, Brunel University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315527.
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Brooks, Thomas Michael Brinten. "Condition assessment of Kevlar composite materials using Raman spectroscopy". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5052.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 9, 2009) Includes bibliographical references.
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Brown, Kenneth Alexander. "A Study of Aerodynamics in Kevlar-Wall Test Sections". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49383.
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This study is undertaken to characterize the aerodynamic behavior of Kevlar-wall test sections and specifically those containing two-dimensional, lifting models. The performance of the Kevlar-wall test section can be evaluated against the standard of the hard-wall test section, which in the case of the Stability Wind Tunnel (SWT) at Virginia Tech can be alternately installed or replaced by the Kevlar-wall test section. As a first step towards the evaluation of the Kevlar-wall test section aerodynamics, a validation of the hard-wall test section at the SWT is performed, in part by comparing data from NACA 0012 airfoil sections tested at the SWT with those tested at several other reliable facilities. The hard-wall test section showing good merit, back-to-back tests with three different airfoils are carried out in the SWT's hard-wall and Kevlar-wall test sections. Kevlar-wall data is corrected for wall interference with a panel method simulation that simulates the unique boundary conditions of Kevlar-wall test sections including the Kevlar porosity, wall deflection, and presence of the anechoic chambers on either side of the walls. Novel measurements of the boundary conditions are made during the Kevlar-wall tests to validate the panel method simulation. Finally, sensitivity studies on the input parameters of the panel method simulation are conducted. The work included in this study encompasses a wide range of issues related to Kevlar-wall as well as hard-wall tunnels and brings to light many details of the performance of such test sections.Master of Science
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Pate, Patricia Lynne. "The Preparation of and Upper Atmospheric Effects on Kevlar Films". W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539625590.
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Watson, Simon A. "The modelling of impact damage in Kevlar-reinforced epoxy composite structures". Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395462.
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Nath, Rajat Bushan. "Finite element analysis of interfacial failure mechanisms in fibre-reinforced composites". Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/finite-element-analysis-of-interfacial-failure-mechanisms-in-fibrereinforced-composites(88b177ba-f351-4263-ac35-500680a21613).html.
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Chambers, John Joseph. "Parallel-lay aramid ropes for use as tendons in prestressed concrete". Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/8327.
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Mathur, Virat. "Effects of nanoscale inclusions on impact resistance of Kevlar-epoxy laminate composites". Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/10637.
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Kevlar, an aramid fiber, is one of the most widely used materials for various industrial applications, such as aerospace, automotive, sports, wind energy, biomedical, optics, as well as defense due to its extraordinary mechanical and thermal (fire retardancy) properties and lightweight. In the present study, graphene nanoflakes and nanoclays dispersed in epoxy resins at different weight percentages (0 to 10 wt.%) were incorporated with dry Kevlar fibers through wet-layup process, and then cured under vacuum and high temperature to make Kevlar/epoxy hybrid composites. The prepared composite panels of 16-ply were impact tested using a low-velocity impactor, and C-Scanned before and after the impact tests. During the impact tests, the impact force vs. displacement, impact force vs. time and impact energy values of the composite panels were analyzed and compared. The c-scans of the damaged composite panels were analyzed for damage area and depth. The damaged test panels were exposed to UV light and moisture for 8 days, with an interval of 4 days. The water contact angles around the damaged area were measured for each damaged composite panel. The test results, impact analysis and damage analysis showed that the nanoscale inclusions in the Kevlar/epoxy composites had a major impact in dissipating the kinetic energy into heat, other forms of energy, and elastic and plastic deformation, and thus saving the composite panels from the major damages. This comparative research study illustrated that the variation in nanomaterials in the epoxy of a composite makes a significant difference in the impact response of the laminate. This result may be useful for the further improvement of the Kevlar-based products in various industries.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Cairns, Douglas Scott. "Impact and post-impact response of graphite/epoxy and Kevlar/epoxy structures". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14652.
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Vita. Title as it appeared in M.I.T. Graduate List, September 1987: Impact and post-impact response of laminated structures.Bibliography: v.2, leaves 341-347.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987.
by Douglas Scott Cairns.
Ph.D.
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Rocha, Davi Costa dos Santos. "Modificação de tecidos de Kevlar com partículas de SiC para aplicação balística". Instituto Tecnológico de Aeronáutica, 2013. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2844.
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O Kevlar, um tecido de fibras de poli (p-aramida), é um material amplamente utilizado em produtos que requerem uma elevada capacidade de absorção de energia de impacto, como as aplicações de proteção balística. Em tais aplicações faz-se necessário um material de elevada resistência mecânica, propriedade em que o Kevlar se destaca entre outros materiais não poliméricos, devido ao fato de tal resistência estar associada a um baixo peso. Entre os mecanismos de absorção de energia deste material, estão: o atrito entre filamentos, o atrito entre as fibras do tecido e a mobilidade das fibras. Surge, então, a possibilidade de alterar a superfície das fibras, de forma a melhorar o desempenho do Kevlar no momento do impacto. Para alterar a superfície das fibras do tecido, foi utilizado neste trabalho o processo de impregnação por via úmida. Para tanto foi utilizada uma dispersão de carbeto de silício (SiC) em etanol, sendo o pó de SiC previamente cominuído e caracterizado por difratometria de raios-X, espectroscopia de infravermelho por transformada de Fourier (FTIR), análise de distribuição de tamanhos e análise de impurezas pela técnica de absorção atômica. Foram utilizados três métodos de impregnação: imersão do Kevlar por 15 min na dispersão, imersão do Kevlar por 30 min na dispersão e imersão do Kevlar por 30 min na dispersão com mudança de lados. Neste último método, a face que estava em contato com o fundo do recipiente foi virada após 15 min, de forma que cada face do tecido permanecesse 15 min voltada para cima. Após a impregnação por diferentes métodos, as amostras de Kevlar foram caracterizadas quanto ao teor e distribuição das partículas de SiC no tecido, quanto à interação química entre SiC e Kevlar, quanto às características tribológicas superficiais e também quanto à resistência ao pull-out. Nos ensaios tribológicos foi notável a diferença entre os coeficientes de atrito ao se comparar a amostra como recebida com as demais. Aquela apresentou o menor coeficiente de atrito metal-tecido. Ao se comparar os coeficientes de atrito das amostras impregnadas e da amostra tratada com etanol foi possível notar que estes coeficientes apresentam valores próximos. No método de impregnação com alternância de lados, foi obtido um aumento maior que 150 % na força máxima registrada durante a extração do filamento, sendo este o método que apresentou o maior valor de força máxima. A impregnação do Kevlar com partículas de SiC se mostrou, portanto, eficiente na alteração da resistência do tecido ao pull-out, o que pode resultar em uma melhor capacidade de absorção de energia de impacto balístico deste tecido.
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Joguet, Pascale. "Comportement mécanique de matériaux composites : Étude sur tubes bobibes sous sollicitations uniaxiales et biaxiales". Besançon, 1989. http://www.theses.fr/1989BESA2031.
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Le comportement de tubes bobines en materiaux composites, de type kevlar/epoxy et carbone/epoxy, sont etudies dans des cas de sollicitations simples ou couplees (traction, torsion, pression interne), en couplant un modele mecanique d'endommagement anisotrope a une theorie elastique de plaques stratifiees. On cherche a prevoir le comportement de structures d'empilement complexe a partir des caracteristiques mecaniques du composite unidirectionnel et de l'identification des lois d'endommagement sur un bobinage a 90#o. Les previsions des seuils d'apparitions de la non-linearite du comportement et de la rupture du composite global, sont envisagees a partir de l'application couche par couche de trois criteres quadratiques (hashin, hill et tsai), sous sollicitations uniaxiales ou biaxiales. On compare les resultats de cette modelisation avec le comportement experimental sous chargements monotones radiaux, pour deux types de stratifications dans le cas des tubes kevlar/epoxy. Les ecarts observes sont analyses en considerant les hypotheses de la modelisation (plis croises en aller-retour) et les resultats d'observations microstructurales. On met en evidence une correlation entre les comportements et les dommages detectes par les controles non destructifs. Un autre modele pour les materiaux viscoelastiques endommageables considere le materiau composite comme homogene. L'utilisation de ce modele permet de determiner la part d'endommagement et de viscoelasticite dans le comportement d'un tube kevlar/epoxy, a partir des boucles d'hysteresis et des deformations residuelles obtenues par chargements repetes progressifs. Cette etude fait partie d'un axe de recherche visant a etablir une modelisation complete du comportement des materiaux composites
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Erwin, Stephanie K. "The Veil of Kevlar: an Analysis of the Female Engagement Teams in Afghanistan". Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6792.
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Recent developments in the population engagement strategies associated with Operation Enduring Freedom and the International Security Assistance Force in Afghanistan have led to the emergence of the Female Engagement Teams. These Teams seek to provide insight and intelligence while engendering American and ISAF efforts in the region, by utilizing female service members to actively engage and interact with the population. This thesis endeavors to answer the question of how the Female Engagement Teams evolved around combat exclusion and given the nature of the conflict in Afghanistan can they serve to facilitate the missions of counterinsurgency and population engagement This paper will serve as the beginning of the academic analysis of this concept and policy for potential use in future determinations by civilian and military leadership. Understanding of both the tribal networks wielded by women and their capacities to influence their world while still recognizing the given constraints and realities of gender seclusion are a necessity to truly exploit the human and cultural terrain in Afghanistan. The FETs despite the restrictions of combat exclusion seem the preeminent means by which to tap into this fountain of possibility.
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Fernando, Gerard Franklyn. "The fatigue behaviour of unidirectional mono-fibre and hybrid kevlar/xas/914 composites". Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760597.
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Wollbrett-Blitz, Judith. "Comportement mécanique longitudinal et transverse, micro-mécanismes de déformation et effet de la température sur la fibre Kevlar® 29". Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0062/document.
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Concevoir des moyens de mobilité plus sûrs et plus légers est un défi majeur des constructeurs automobiles. Dans ce contexte, l'intégration des matériaux dans le pneumatique a elle aussi été soumise à de nouvelles exigences : concilier performances et économie d'énergie. Les renforts traditionnels à forte densité comme les tréfilés d'acier sont peu à peu et en partie remplacés par des matériaux polymères hautes-performances plus légers tel que le para-aramide. Le Kevlar® est le nom industriel du composé polyamide aromatique : poly(paraphénylène téréphtalamide), intégré à l'architecture du pneumatique sous forme d'un fil torsadé. La structure rigide et fortement orientée de l'aramide confère à ce polymère de hautes performances mécaniques, telles qu'un module élevé dans la direction longitudinale, de l'ordre de 85GPa, et une grande résistance mécanique de plus de 2.8GPa. Les hautes performances de cette fibre de 15 micromètres de diamètre sont dues à son organisation multi-échelles isotrope transverse avec des liaisons covalentes dans la direction longitudinale et des liaisons de plus faibles énergies dans la direction radiale. L'objectif de cette étude est de comprendre, à l'échelle de la fibre unitaire, les corrélations entre l'architecture microstructurale et la réponse mécanique dans les directions longitudinale et transverse. Une approche expérimentale multi-échelle a été adoptée (Extensometrie Raman, DRX, MEB, caractérisation mécanique sur fibre unitaire), couplée à l'outil numérique afin d'apporter des nouveaux éclairages sur les micro-mécanismes de dissipation. Ce travail a mené à une identification expérimentale du comportement mécanique anisotrope ainsi qu'à établir une limite de plasticité transverse. De plus, grâce à l'approche numérique, une architecture cœur/peau a été mise en avant en modélisant le comportement par une loi viscoélasto-viscoplastique anisotrope. Enfin, des éléments sur le couplage thermo-mécanique sont apportés en vue de mieux comprendre le cycle de vie de la fibre au sein du pneumatiqueDesigning safer and lighter vehicles is a major challenge for manufacturers. Nowadays, a vehicle needs to be eco-friendly and conciliate efficiency and energy-saving. Considering these requirements, tire materials are subject to change: high performance polymers are a good replacement, in terms of weight and dissipation, for traditional reinforcements such as drawn steel. For instance, aramid strands (1000 fibres) are used because the single fibre exhibits good mechanical properties such as its high modulus (85 GPa) conferred by its anisotropy or its high temperature resistance. The mechanical performance of a Kevlar® fibre is due to its different scale organisation : the primary (molecular chains held by covalent bonds), the secondary (pleated sheets held by interactions) and the tertiary structure (sheets stacked together). Because of the cooling thermodynamics during the fabrication process, the 15 microns diameter fibre seems to have a skin/core structure with punctual more or less critical defects. To go further in the understanding of the complex structure, the contribution of the skin/core structure in the mechanical performance in the longitudinal and the transverse directions is investigated through a multi-disciplinary approach made of a numerical and an experimental study. During its use, an aramid single fibre undergoes cyclic multiaxial loading and harmful thermal treatments, at the origin of structural and mechanical properties modifications but also dissipative behaviour evolution, still misunderstood. To deal with these change in depth, an experimental and numerical multi-scale characterisation is used. Mechanical and thermal treatments are realised and their impact on the microstructure, on the deformation micromechanisms and on the mechanical properties including the dissipative behaviour are investigated. Limiting use values in terms of temperature, longitudinal and transverse stresses are highlighted in this work in order to understand modifications enhanced by the fibre life cycle
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O'Neil, Joseph M. "Factors contributing to the degradation of poly(p-phenylene benzobisoxazole) (PBO) fibers under elevated temperature and humidity conditions". Thesis, Texas A&M University, 2006. http://hdl.handle.net/1969.1/4439.
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The moisture absorption behavior of Zylon fibers was characterized in various high temperature and high humidity conditions in a controlled environment. The results of these thermal cycling tests show that PBO fibers not only absorb, but also retain moisture (approximately 0.5-3%) when exposed to elevated temperature and humidity cycles. Also, the impurities of Zylon fibers were characterized through the use of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and solid state Nuclear Magnetic Resonance (NMR). These tests demonstrated that, in addition to other impurities, PBO fibers may contain up to 0.55 weight percent phosphorus, and that this phosphorus is present in the form of phosphoric acid. It was also shown through accelerated hydrolytic degradation tests that production procedures used to neutralize the acid present in the fibers have a beneficial effect on the hydrolytic performance of the fiber. The data collected in this study was then compared and contrasted to known Kevlar studies, identifying similarities, differences, and potential trends. The results of these tests seem to indicate that there is accelerated acid catalyzed hydrolysis occurring in the fiber which is causing these fibers to degrade at an increased rate. This condition is further accelerated by heat and humidity induced permanent fiber swelling.
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Jayarajah, James Nirmal. "Coalescence and filtration of emulsions using fibres". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343600.
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Belenet, Hubert de. "Les prothèses de remplacement des ligaments croisés du genou : les différents matériaux utilisés : contribution à l'étude de la biocompatibilité des fibres de polyéthylène HD et de kevlar : étude expérimentale". Bordeaux 2, 1988. http://www.theses.fr/1988BOR25389.
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Guimaraes, Giuseppe Barbosa. "Parallel-lay aramid ropes for use in structural engineering". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/8631.
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Bernardi, Stefania Tesi. "Avaliação do comportamento de materiais compósitos de matrizes cimentícias reforçadas com fibra de aramida kevlar". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2003. http://hdl.handle.net/10183/3596.
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Esse trabalho aborda a questão de materiais compósitos reforçados com fibras (fiber reinforced concrete) com enfoque em matrizes cimentícias reforçadas com fibra de aramida Kevlar. O objetivo é caracterizar o potencial da fibra de aramida Kevlar como elemento de reforço a ser adicionado ao concreto. O trabalho busca caracterizar o desempenho dos compósitos formados, identificando as alterações decorrentes da incorporação em função do comportamento mecânico e da resistência ao impacto. Os objetivos são verificar a potencialidade de utilização dessa fibra em termos de trabalhabilidade e resistência mecânica; definir como deve ser a forma de incorporação, verificar a aderência da fibra à matriz através de microscopia eletrônica de varredura por elétrons secundários e determinar a resistência ao impacto, comparando matrizes sem adição de fibra com corpos-de-prova moldados com vários tipos e teores de fibra (aço, sisal, vidro, polipropileno e aramida). Como vantagens da incorporação das fibras de aramida Kevlar, constata-se um incremento na resistência à compressão dos compósitos aos 28 dias em relação aos espécimes sem adição de fibra. Observam-se, também, reduções na massa específica e na trabalhabilidade dos espécimes com adição de fibra de aramida Kevlar em comparação aos sem adição. Em relação à resistência ao impacto, conclui-se que os compósitos com adição de fibra de aço e fibra de aramida são os que apresentaram melhor comportamento dinâmico em relação a energia de ruptura acumulada e à energia para aparecimento da primeira fissura, respectivamente.
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Lefebvre, Marie. "Résistance à l’impact balistique de matériaux composites à renforts Interlocks tissés : application au blindage de véhicules". Valenciennes, 2011. https://ged.uphf.fr/nuxeo/site/esupversions/25e254d5-2d8c-4d76-9959-cb97a45dcce8.
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Cette étude s’inscrit dans le cadre d’une recherche exploratoire innovante (REI), financée par la DGA et vise à étudier le comportement à l’impact de matériaux composites à renfort Interlock. L’objectif final de ce travail est d’intégrer dans des blindages de véhicules terrestres, un matériau composite à renfort tissé Interlock de fibres hautes performances qui sera placé à l’arrière d’un matériau métallique utilisé pour fragmenter le projectile, ici un FSP, au moment de l’impact. Le matériau composite aura un rôle d’absorbeur d’énergie durant l’impact et permettra d’arrêter les fragments métalliques suite à la pénétration du blindage métallique par le projectile. La réalisation de ce matériau passe par l’élaboration des structures tissées Interlocks sur une machine à tisser manuelle puis à la mise en œuvre des tissus par techniques d’infusion. Les matériaux sont ensuite testés en condition d’impact réel. Un critère de comparaison a été établi en prenant en compte la vitesse limite de perforation (Vlp) du matériau et les masses surfaciques de chaque structure testée afin de ramener les performances balistiques à iso masse. Pour cette étude nous avons choisi de fabriquer trois architectures Interlocks ayant des paramètres de tissage identiques. Nous avons choisi d’utiliser deux types de fibres, du Kevlar® et du Vectran® pour chaque structures. La modification du procédé de tissage et de l’infusion des matériaux a permis de faire ressortir deux structures Interlocks en Vectran® présentant un critère d’impact équivalent aux structures actuellement utilisées dans le domaine du blindage de véhiculeThis study is a part of an innovative exploratory research with the financial support of the DGA. The aim is to study the impact behaviour of Interlock composite materials. The final objective is to integrate a composite material based on Interlock weaving structure into vehicle armor system that will be placed as backing of a metal panel used to fragment the FSP projectile during the impact. The composite materials should absorb the impact energy during impact and stop the metal fragments after penetration of the metal panel by the projectile. The fabrication of these materials leads to create woven Interlock structures on a weaving loom and the implementation of the fabrics by infusion process. The materials are then impacted. A criterion of comparison was used, taking into account the speed limit perforation of the material and the area density of each impacted structures in order to compare the ballistic performance at the same weight. For this study we have made the choice to produce three Interlocks weaving structures with the same weaving parameters. We also choose to use two types of fibres, Kevlar® and Vectran® for each structure. The change of the weaving process and the infusion of materials allowed us to bring out two Interlocks structures composed of Vectran® fibres with the impact criterion equivalent to the structures currently used in the field of vehicle armor
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Felipe, Renata Carla Tavares Santos. "Envelhecimento ambiental acelerado em PRF a base de tecidos h?bridos kevlar/vidro: propriedades e instabilidade estrutural". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15592.
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Previous issue date: 2012-09-14There are a number of damaging mechanisms that various materials can suffer in service. However, when working with polymer composite materials, this is something that requires analysis, especially when exposed to adverse environmental conditions. Thus, the objective of the present thesis is the study of the direct influence of environmental aging and the form of hybridization of the reinforcement woven on the structural stability, surfacedegradation and fracture process of polymer composites laminates. For this, the development of two polymer composite laminates was necessary, where one of them was reinforced with a bi-directional woven with hybrid strandsofkevlar-49/glass-Efibers, and the other also with a bi-directionalwoven, however with weft and warpformed of alternating strandsof Kevlar-49 fibers and glass-E fiber The reinforcementwoven are industrially manufactured. Both laminates use a polyester resin as a matrixand are made up of four layers each. All laminates were industrially prepared by the hand lay-up method of manufacturing. To do this, test specimens were manufactured of the respective laminates and submitted to environmental aging accelerated through the aging chamber. They were exposed to alternating cycles of UV radiation and moisture (heated steam) for a standard defined period. At the end of the exposure period the specimens were subjected to mechanical tests of uniaxial tensile and bending in three points and to the characterizationsof the fracture and surface deterioration. In addition, they were submitted to a structural degradation assessment by the measurement of mass variation technique (MMVT) and the measurement of thickness variation technique (MTVT), this last technique being developed in this thesis. At the end of the analysis it was observed that the form of hybridization of the reinforcement woven and the aging process directly influence with losses or gain in mechanical properties, with losses in the structural degradation and in the formation and propagation of damage mechanism of the developedcomposite laminates
S?o v?rios os mecanismos de danos que os diversos materiais podem sofrer em servi?o. No entanto, ao se trabalhar com os materiais comp?sitos polim?ricos isso ? algo que necessita de an?lises principalmente quando expostos a condi??es ambientais adversas. Logo, a respectiva tese objetiva o estudo da influ?ncia direta do envelhecimento ambiental e da forma de hibridiza??o dos tecidos de refor?o no comportamento mec?nico, degrada??o estrutural (dimensional e de massa) de laminados comp?sitos polim?ricos. Para tanto se fez necess?rio o desenvolvimento de dois laminados comp?sitos polim?ricos, onde um deles ? refor?ado com um tecido bidirecional com mecha h?brida de fibras de kevlar-49/vidro-E e o outro com um tecido tamb?m bidirecional, por?m com trama e urdume formadas com mechas alternadas de fibras kevlar-49 e fibras de vidro-E. Os tecidos de refor?o s?o de fabrica??o industrial. Ambos os laminados utilizam como matriz a resina de poli?ster, sendo constitu?dos de quatro camadas cada. Todos os laminados foram confeccionados industrialmente pelo m?todo de fabrica??o handlay-up. Desta forma, foram fabricados corpos de provas (CP s) dos respectivos laminados e submetidos ao envelhecimento ambiental acelerado atrav?s da c?mara de envelhecimento. Os mesmos foram expostos aos ciclos alternados de radia??o UV e umidade (vapor aquecido) por um per?odo definido em norma. Ao t?rmino do per?odo de exposi??o os CP s foram submetidos aos ensaios mec?nicos de tra??o uniaxial e flex?o em tr?s pontos e ?s caracteriza??es da fratura e da deteriora??o superficial. Al?m disso, foram submetidos ? avalia??o da degrada??o estrutural mediante a t?cnica de media??o de varia??o de massa (TMVM) e a t?cnica de medi??o de varia??o de espessura (TMVE), sendo essa ?ltima desenvolvida nesta tese. Ao t?rmino das an?lises foi observado que a forma de hibridiza??o dos tecidos de refor?o e o processo de envelhecimento influenciam diretamente, seja com perdas ou ganho naspropriedades mec?nicas, com perdas na degrada??o estrutural e na forma??o e propaga??o do mecanismo de dano dos laminados comp?sitos desenvolvidos
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Mazáč, Petr. "Koncepční návrh ultra lehké konstrukce lunárního habitatu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230821.
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This master’s thesis deals with ultra lightweight structural design concept of a lunar habitat. The beginning of the thesis is focused on basic properties of the Moon and different concept designs of lunar habitats and bases. Afterwards the main concept is introduced with defined loads followed by application of loads on the construction and design of main parts of the construction, especially design of an inflatable beam. Thesis is ended by manufacturing technology of an inflatable beam and design concept of main structural nodes.
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Liu, Zhihui. "Properties of 3D Printed Continuous Fiber-Reinforced CNTs and Graphene Filled Nylon 6 Nanocomposites". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045511745974.
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Aguilar, Juan Pablo. "Experimental methodology to assess the effect of coatings on fiber properties using nanoindentation". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45781.
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Current body armor technologies need further improvements in their design to help reduce combat injuries of military and law enforcement personnel. Kevlar-based body armor systems have good ballistic resistance up to a certain ballistic threat level due to limitations such as decreased mobility and increased weight [1,2]. Kevlar fibers have been modified in this work using a nano-scale boron carbide coating and a marked increase in the puncture resistance has been experimentally observed. It is hypothesized that this improvement is due to the enhancement of the mechanical properties of the individual Kevlar fibers due to the nano-scale coatings. This study presents a comprehensive experimental investigation of individual Kevlar fibers based on nanoindentation to quantify the cause of the enhanced puncture resistance. The experimental setup was validated using copper wires with a diameter size in the same order of magnitude as Kevlar fibers. Results from nanoindentation did not show significant changes in the modulus or hardness of the Kevlar fibers. Scanning Electron Microscopy revealed that the coated fibers had a marked change in their surface morphology. The main finding of this work is that the boron carbide coating did not affect the properties of the individual fibers due to poor adhesion and non-uniformity. This implies that the observed enhancement in puncture resistance originates from the interaction between fibers due to the increase in roughness. The results are important in identifying further ways to enhance Kevlar puncture resistance by modifying the surface properties of fibers.
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Cavini, Andrea. "Studio e progettazione di una piastra in materiale composito per calzature da competizione". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Il presente elaborato consiste in uno studio teorico della possibile applicazione di materiali compositi, rinforzati a fibre, per la realizzazione di una piastra per scarpe da competizione utilizzate nelle discipline di velocità dell’atletica leggera.
Mediante un’analisi approfondita degli aspetti fondamentali della corsa di velocità, ci si è concentrati sulla determinazione di un modello biomeccanico del piede, al fine di valutare l’entità e le caratteristiche delle GRF (forze di reazione con il terreno) generate durante il gesto atletico. Sulla base delle informazioni così ricavate è stato definito un modello meccanico approssimativo della piastra; questo ha permesso di individuare le caratteristiche e l’entità delle sollecitazioni applicate sulla piastra stessa durante le successive fasi di una gara dei 100 metri piani.
Infine, sono state determinate le proprietà del laminato da utilizzare per la realizzazione di un primo prototipo della particolare suola di queste calzature.
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Wijanto, Ludovikus Sugeng. "Seismic Assessment of Unreinforced Masonry Walls". Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2007. http://hdl.handle.net/10092/1680.
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This thesis focuses on the seismic performance of unreinforced masonry wall perforated with
a door opening representing typical URM walls of many aged masonry buildings in
Indonesia. To obtain a test result that will be able to represent the local conditions, the
experiments have been conducted in the Research Institute for Human Settlements (RIHS)
laboratory in Bandung-Indonesia.
Two 75 % unreinforced masonry (URM) walls with a 1½-wythe of solid clay-brick were
constructed in Dutch bond configuration and tested until failure under quasi-static-reversed
cyclic loading. Both units were loaded vertically by constant loads representing gravity loads
on the URM wall’s tributary area. Both models were constructed using local materials and
local labours. Two features were taken into account. First, it accommodated the influence of
flanged wall and second, the URM wall was built on the stone foundation. The first URM
wall represent the plain existing URM building in Indonesia and second strengthened by
Kevlar fibre.
It was observed from the test results that the URM wall Unit-1 did not behave as a brittle
structure. It could dissipate energy without loss of strength and had a post-elastic behaviour in
terms of “overall displacement ductility” value of around 8 to 10. As predicted, the masonry
material was variable and non homogeneous which caused the hysteresis loop to be non
symmetrical between push and pull lateral load directions. It can be summarized that Kevlar
fibre strengthening technique is promising and with great ease of installation. Although
Kevlar material is more expensive when compared to other fabrics as long as it was applied at
the essential locations and in limited volumes, it can significantly increase the in-plane URM
wall capacity. With appropriate arrangements of Kevlar fibre, a practicing engineer will be
able to obtain a desired rocking mechanism in the masonry structure. Another advantage for
the architectural point of view, very thin Kevlar fibres do not reduce the architectural space.
Studies have also been undertaken to analyze the in-plane response of plain URM wall before
and after retrofiting using the current seismic standard and the Finite Element Method (FEM).
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Vachon, Pierre-Luc. "Étude comparative sur la propagation de l’endommagement après impact des composites carbone/époxy renforcés par piquage au fil Kevlar et TI-NI". Mémoire, École de technologie supérieure, 2012. http://espace.etsmtl.ca/1114/1/VACHON_Pierre%2DLuc.pdf.
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Les matériaux composites stratifiés présentent des propriétés mécaniques enviables dans le plan des couches de fibres, mais ils ont également une faiblesse naturelle dans la direction de l’épaisseur. Cette faiblesse peut donner lieu à l’apparition de zones délaminées invisibles à l’oeil nu, particulièrement lors d’un impact à faible vitesse. Par conséquent, beaucoup de travaux de recherche ont été dédiés à l’étude de méthodes de renfort interlaminaire pour les stratifiés, dont notamment l’insertion de coutures transversales. Ce projet de recherche propose donc d’utiliser la technique de couture avec un fil métallique en alliage TiNi présentant un comportement superélastique. La combinaison de ces deux éléments devrait permettre l’amélioration de la résistance à la propagation du délaminage lors d’un chargement en flexion.
En premier lieu, un modèle numérique a été développé pour servir d’outil d’analyse des structures composites. Le modèle 3-D a été construit dans l’environnement ANSYS à partir d’éléments solides à 20 noeuds et d’éléments shell à 8 noeuds. La technique d’endommagement progressif a été implémentée, permettant ainsi de prédire la propagation du délaminage dans une plaque stratifiée soumise à différents chargements. Le modèle a d’abord été validé en traction quasi-statique avant d’être utilisé pour simuler des essais de flexion trois-points.
Par la suite, des plaques de composite carbone/époxy ont été fabriquées, chaque plaque comprenant des échantillons renforcés de couture et d’autres non renforcés. Deux types de renforts ont été utilisés : des fils TiNi superélastiques et des fils de Kevlar, à titre de référence. Les plaques renforcées ont été découpées pour permettre l’observation des coutures internes au microscope optique.
Des essais standardisés d’impact à faible vitesse et de compression résiduelle après impact ont été menés (ASTM D7136 et D7137) sur les échantillons renforcés et non renforcés. Les renforts de Kevlar se sont montrés les plus performants pour réduire la zone endommagée après impact, ainsi que pour améliorer la résistance résiduelle en compression. Les renforts de TiNi ont tout de même présenté une amélioration encourageante pour ce qui est de la performance lors de l’impact, alors que la différence lors de l’essai de compression s’est avérée très faible par rapport aux échantillons non renforcés.
En troisième lieu, la performance en flexion trois-points des échantillons a été quantifiée expérimentalement en calculant l’énergie nécessaire pour créer un volume unitaire de matériau endommagé (Gv, J/mm3). Ce paramètre s’apparente au taux de restitution de l’énergie de déformation (Strain Energy Release Rate) communément rencontré dans les travaux sur le délaminage. Les résultats ont montré que bien que les renforts de Kevlar permettaient d’améliorer la ténacité à l’endommagement lors de l’impact, cette performance n’était pas entièrement reportée sur la ténacité à l’endommagement durant l’essai de flexion. Ainsi, en relativisant l’énergie de déformation dégagée lors de la propagation du délaminage par rapport au volume de délaminage engendré, on constate que les renforts de TiNi augmentent la valeur de cette résistance à l’endommagement.
Finalement, l’étude numérique du comportement des renforts a permis d’identifier des différences qui étaient imperceptibles sur les courbes Force-Déplacement. Les deux types de renforts semblent favoriser la propagation interlaminaire du délaminage lors de la flexion, bien que ce comportement soit moins prononcé dans le cas du TiNi. Cependant, les fils de Kevlar semblent plus efficaces pour freiner la propagation latérale du délaminage entre les
lignes de couture.
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Azev?do, Camilla de Medeiros Dantas. "Estudo da resist?ncia residual de comp?sitos polim?ricos de fibra de vidro-e e kevlar 49 ap?s sofrerem impacto de baixa velocidade". PROGRAMA DE P?S-GRADUA??O EM ENGENHARIA MEC?NICA, 2017. https://repositorio.ufrn.br/jspui/handle/123456789/24937.
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As propriedades mec?nicas dos materiais comp?sitos, das mais diversas aplica??es industriais, podem ser reduzidas significativamente pela ocorr?ncia de impactos de baixas velocidades. Esses impactos podem provocar danos internos no material comprometendo sua integridade. Assim, o presente estudo tem como objetivo fazer uma an?lise experimental da resist?ncia residual ? flex?o em tr?s pontos e compress?o ap?s o impacto (CAI), de dois tipos de laminados comp?sitos de matriz polim?rica ortoft?lica, sendo um deles refor?ado a com 7 camadas de tecido bidirecional de Vidro E (CV) e o outro refor?ado com 7 camadas de tecido bidirecional de Kevlar 49 (CK), sujeitos a impactos de baixa velocidade. Esse estudo ? de grande import?ncia pelo fato de tentar conduzir ao aparecimento prematuro de instabilidade estrutural e a consequente restri??o do seu uso. A energia utilizada nesse trabalho para os dois tipos de laminados foi de aproximadamente 96J. Al?m disso, para o material comp?sito refor?ado com fibra de kevlar, foram feitos sucessivos impactos com a mesma energia verificando sua influ?ncia nas propriedades do laminado. Sendo aplicadas 5 vezes, e 10 vezes a energia m?xima de 96J. Como resultado verificou-se que no laminado CV, tanto as propriedades de compress?o como de flex?o em tr?s pontos, a resist?ncia se manteve praticamente inalterada enquanto que o m?dulo teve uma diminui??o depois do impacto. J? no laminado CK houve um decr?scimo tanto nas propriedades de compress?o como flex?o em tr?s pontos ap?s o impacto. Essa perda da integridade desses materiais pode ser justificada pela ocorr?ncia de delamina??o nas interfaces dos comp?sitos.
The mechanical properties of the composite materials, used in the most diverse industrial applications, can be significantly reduced by the occurrence of low speed impacts. These impacts can cause internal damage to the material and compromise its integrity. Thus, the present study aims to perform an experimental analysis of the residual resistance to three-point flexural test and compression after impact (CAI), in two types of composite laminates of orthophthalic polymeric matrix, being one of them reinforced with 7 layers of E-Glass bidirectional tissue (CV) and the other reinforced with 7 layers of Kevlar 49 bidirectional tissue (CK), subject to low speed impacts. This study is of great importance because it tries to lead to the premature appearance of structural instability and the consequent restriction of its use. The energy used in this work for the two types of laminates was approximately 96J. In addition, for the Kevlar fiber reinforced composite material, were made successive impacts with the same energy being checked its influence on the properties of the laminate, where it was tested with a repetition of 5 times and 10 times the maximum energy of 96J.As result, it was found that in the CV laminate, both in the compression properties and three-point flexural properties, the resistance remained practically unchanged while the modulus had a decrease after impact. In the CK laminate, there was a decrease both in compression properties and three-point flexural properties after impact. This integrity loss of these materials can be justified by the occurrence of delamination at the interfaces of the composites.
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LILLIEROTH, AMANDA y LINNEA BRYNGELSSON. "Produktutveckling av handske för bilsport". Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17991.
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: I denna rapport har det gjorts en undersökning om vilket som är det mest lämpliga materialet/ materialen för en handske till formel 1 bilförare. Genom kvalitativa intervjuer och informationsundersökning har en kravspecifikation sammanställts med de viktigaste kraven, som förare och regelverket ställer. Reglerna är angivna i standarder till handskar för formel 1 bilförare. ! En rad olika tester har gjorts och genom det har frågeformuleringarna besvarats. De material som testades var Nomex®, Kevlar®, Trevira CS® och Nomex® III. För att sammanställa alla resultat av testerna har det värderats i två typer av matriser. Den första matrisen som gjordes var en Concept Screening Matrix, där de alternativa materialen fick värden utifrån hur väl de klarade de tre standarder som fanns. På de material som klarade denna matris gjordes sedan en mer detaljerad undersökning, där fanns även förarnas önskemål med som krav på materialen. Dessa tester sammanställdes med olika värden i en Concept Scoring Matrix, resultatet av denna tabell sammanfattar vilket/vilka material som blev svaret på frågeformuleringarna. Det material som efter testerna visade sig vara det mest lämpliga materialet för handskar till formel 1 bilförare var Nomex® och strax efter kom Nomex® III.Program: Textil produktutveckling och entreprenörskap
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Arrieta, Carlos. "Étude de l'effet du vieillissement sur les propriétés d'un tissu en mélange Kevlar®-PBI utilisé dans le revêtement extérieur des habits de protection contre le feu". Mémoire, École de technologie supérieure, 2011. http://espace.etsmtl.ca/884/1/ARRIETA_Carlos.pdf.
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Ce projet porte sur l’étude de l’effet de trois facteurs environnementaux, la température,
l’humidité et le rayonnement lumineux, sur les propriétés d’un tissu en mélange Kevlar®-PBI
couramment utilisé dans la fabrication des habits de protection contre le feu. Des traitements
de vieillissement accéléré ont entraîné une perte significative de performance mécanique,
mise en évidence par une diminution de la force de rupture d’un minimum de 50% au bout
d’un mois d’exposition continue. Des tests de diffraction des rayons X (XRD) menés sur des
échantillons du tissu vieillis thermiquement ont reflété une augmentation de la cristallinité du
tissu. La disparition de lignes spectrales en spectroscopie Raman indiquait plutôt une perte de
cristallinité suite au vieillissement thermique. Afin d’expliquer ces résultats en apparence
contradictoires, une hypothèse a été avancée. Cette hypothèse soutient que deux phénomènes
simultanés ont lieu suite à l’exposition aux températures élevées : d’une part les cristaux
augmentent dans la direction parallèle aux fibres, ce qui est mis en évidence par les tests de
diffraction; et d’une autre l’écart entre les lamelles cristallines se creuse, un événement qui
entraîne une diminution de la cristallinité et qui est relevé par les analyses Raman. Les
résultats des mesures de spectroscopie diélectrique réalisées sur des échantillons vieillis
thermiquement ont confirmé le changement de la morphologie du Kevlar® suite au
vieillissement thermique. Aucun indice d’une possible modification de la structure chimique
du Kevlar® n’a été repéré. Des analyses thermiques différentielles ont révélé, par contre, une
diminution de la température de transition vitreuse de l’autre composant du mélange, à savoir
le PBI, un fait qui suggère que ce matériau a subi une diminution de sa masse molaire. Des
analyses ATR menées sur des échantillons soumis à des traitements de vieillissement par
humidité ont permis d’identifier l’hydrolyse de la liaison amide du Kevlar® catalysée par un
acide comme étant le mécanisme de dégradation responsable de la perte de performance
mécanique suite au vieillissement par humidité. La progression de la réaction d’hydrolyse a
été modélisée mathématiquement au moyen de l’évolution de la concentration de
groupements acide carboxylique. Dans le cas des traitements de vieillissement
photochimique accéléré, le mécanisme de dégradation a été déterminé à l’aide des analyses
ATR. Ce mécanisme correspond à une photo-oxydation amorcée par la thermolyse de la
liaison amide du Kevlar®. L’accumulation de produits Photo-Fries, un sous-produit de la
photo-oxydation, pendant le vieillissement photochimique est soupçonnée d’entraîner un
ralentissement de la réaction de photo-oxydation, mis en évidence par la superposition des
courbes de force de rupture. Des modèles basés sur la loi d’Arrhenius ont été proposés pour
modéliser le vieillissement thermique et hydrolytique, tandis qu’un modèle tenant compte
autant du niveau de flux énergétique que de la température a été formulé pour décrire le
vieillissement par rayonnement lumineux. Un modèle inspiré de la théorie linéaire
d’accumulation d’endommagement de Palmgren-Miner a été proposé pour exprimer
l’endommagement global entrainé par l’ensemble des trois facteurs de vieillissement.
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Allen, Devin Nelson. "Damage Tolerance of Unidirectional Basalt/Epoxy Composites In Co-Cured Aramid Sleeves". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3158.
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Unidirectional basalt fiber rods consolidated with an aramid sleeve were measured for compression strength after impact at various energy levels and compared to undamaged control specimens. These structural elements represent local members of open three-dimensional composite lattice structures (e.g., based on isogrid or IsoTruss® technologies) that are continuously fabricated using advanced three-dimensional braiding techniques. The unidirectional core specimens, nominally 8 mm (5/16") and 11 mm (7/16") in diameter, were manufactured using bi-directional braided sleeves or unidirectional spiral sleeves with full or partial (approximately half) coverage of the core fibers. The 51 mm (2") specimens were shorter than the critical buckling length, ensuring the formation of kink bands, typical of strength-controlled compression failure of unidirectional composites. The test results indicate an approximate decrease in the average undamaged compression strength of approximately 1/3 and 2/3 when impacted with 5 J (3.7 ft-lbs) and 10 J (7.4 ft-lbs) for the 8 mm (5/16") diameter specimens and 10 J (7.4 ft-lbs.) and 20 J (14.8 ft-lbs.) for the 11 mm (7/16") diameter specimens, respectively. The aramid sleeves improved the damage tolerance of the composite members, with the amount of coverage having the greatest effect; full coverage exhibiting up to 45% greater strength than partial coverage. Braided sleeves improved compression strength after impact by up to 23% over spiral sleeves, but generally had little effect on damage tolerance. Larger diameter specimens tend to be more resistant to damage than those specimens of a smaller diameter. The compressive material properties for undamaged basalt composites are also presented with the average compressive strength being 800 MPa (116 ksi).
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Cunha, Ricardo Alex Dantas da. "Influ?ncia da absor??o de umidade no comportamento mec?nico nos comp?sitos polim?ricos h?bridos Kevlar/vidro quando imerso em ?gua do mar e petr?leo". Universidade Federal do Rio Grande do Norte, 2015. http://repositorio.ufrn.br/handle/123456789/20605.
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Os materiais comp?sitos de matriz polim?rica v?m sendo utilizados em larga escala nas ?reas industriais tais como aeroespacial, automobil?stica, petrol?fera, por apresentarem um bom desempenho mec?nico, vida ?til elevada e uma rela??o custo/benef?cio. A determina??o das propriedades mec?nicas se faz indispens?vel para a caracteriza??o dos comp?sitos. Desta forma, neste trabalho ser?o obtidas tr?s placas de laminados com matriz polim?rica teraft?lica, refor?ados por um tecido bidirecional de vidro-E e kevlar, ambos confeccionados industrialmente, onde as placas ser?o fabricadas pelo processo de lamina??o manual (Hand lay up). Todos os laminados ter?o cinco camadas de refor?o,como primeiro laminado h?brido sendo composto pelo tecido bidirecional de fibra de vidro-E, intercalado por camadas de fibra kevlar, o segundo ? formado pelo tecido bidirecional de fibra kevlar nas extremidades do laminado (duas camadas), e no centro o tecido de fibra de vidro (tr?s camadas), a terceira placa foi composta apenas pelo tecido bidirecional de fibra de vidro-E. Em seguida, foram confeccionados corpos de prova (CP) mediante norma, para determina??o das propriedades mec?nicas de tra??o e flex?o em tr?s pontos. Ap?s a fabrica??o dos corpos de prova, estes foram imersos em petr?leo e em ?gua do mar. Feito isso, realizou-se um comparativo das propriedades mec?nicas para a condi??o de ensaio no estado seco. Houve um aumento consider?vel nas propriedades estudadas devido o efeito da hibridiza??o nos laminados.
The polymer matrix composite materials are being used on a large scale in the most different industrial fields such as aerospace, automotive, oil, among others, since the industrial perspectives is currently working with materials which have a good mechanical performance at high service life and cost / benefit. Thus, the determination of the mechanical properties is indispensable for the characterization of waste resulting in greater expansion of this type of material. Thus, this work will be obtained three plates laminated with tereft?lica polymeric matrix reinforced by a bidirectional woven E-glass and kevlar both industrially made, where the plates are manufactured by manual lamination process (hand lay-up), all laminates have five enhancement layers, the first hybrid laminate will consist of bidirectional woven E-glass fiber, kevlar fiber interspersed with layers, is formed by the second bidirectional woven kevlar fiber at the ends of the laminate (two layers), and in the center the glass fiber fabric (three layers), the third plate is composed of only the bidirectional woven E-glass fiber. Then were prepared specimens (CP) by standard, to determine the mechanical properties of tensile and bending in three points. After fabrication of the specimens, they were immersed in oil and seawater. After that, there was a comparison of the mechanical properties for the test condition in the dry state. Showing that there was a considerable increase in the properties studied because the effect of hybridization in laminates.
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Almonte, Thania Grisel Rodriguez. "Avaliação da resistência à fratura de prótese parcial fixa provisória confeccionada sobre componentes do tipo UCLA em titânio - efeito de diversos reforços". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/25/25135/tde-11042015-110150/.
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As restaurações provisórias no tratamento reabilitador oral são de suma importância. Por isso é preocupante que os materiais utilizados para a execução das mesmas sejam críticos com relação à sua resistência e longevidade, principalmente, quando estas são executadas em tratamentos prolongados e/ou em espaços desdentados extensos. O objetivo deste trabalho foi avaliar em 4 grupos reforçados, compostos por 9 espécimes cada um, a resistência e o modo de fratura, de uma resina acrílica poli(metilmetacrilato) auto-polimerizável (Dencor® - Clássico®, São Paulo, SP, Brasil) utilizada para restaurações provisórias quando reforçada com fibras de vidro (Fibrante® e Interlig® - Angelus®, Londrina, PR, Brasil), fibras de aramida (Kevlar® - Du Pont®, USA) y fio ortodôntico ∅ 0, 7mm. E um grupo controle sem nenhum tipo de reforço, com a mesma quantidade de corpos de prova. A análise dos resultados (ANOVA, p < 0,05), para o teste de resistência, mostrou haver diferença estatística entre os grupos. O teste de Tukey encontrou que os grupos reforçados, aqueles que alcançaram maior média de resistência à fratura foram os que utilizaram a fibra de vidro trançada pré-impregnada com resina composta foto-polimerizável, Interlig® (1083 N); a fibra de vidro unidirecional préimpregnada com dimetacrilato de glicol, Fibrante® (1022 N) e a fibra de poli(aramida) unidirecional sem pré-impregnação, Kevlar® 29, aumentando em 26%, 22% e 17%, respectivamente, esta resistência em relação ao grupo controle (800 N), não havendo diferença estatística significante entre eles. O grupo reforçado com fio de aço com ∅ 0,7 mm (871 N) apareceu em seguida com uma resistência somente 8% maior e semelhante àquela apresentada pelo grupo controle sem reforço. A análise das fraturas concorreu com a elaboração de um novo sistema de classificação dividindo-as em quatro tipos: Ausente, Parcial, Total Não Separada e Total Separada. As fraturas dos espécimes reforçados foram consideradas mais favoráveis ocorrendo, predominantemente, os tipos Ausente e Parcial.Provisional restorations are of ultimate importance in the oral rehabilitation treatment. Thus, clinicians have to bear in mind that materials used for their fabrication are critical due to its longevity and strength, when these are done for longterm therapy and/or large edentulous spaces. The aim of this work was to evaluate the flexural resistance and fracture mode of an auto-cure polymethylmetacrilate resin (Dencor® - Classico® , Sao Paulo, SP, Brasil) used for provisional restorations and reinforced with four materials. Samples were divided in four groups of nine each, as the following: glass fiber (Fibrante® and Interlig® Angelus®, Londrina, PR, Brasil), aramide fibers (Kevlar® Du Pont®, USA), and orthodontic wire ∅ 0,7mm. one group whitout reinforcement served as control. Data was submitted to statistical analysis with one-way ANOVA (p<.05) test. Results showed statistically significant difference among the groups. Tukeys test showed that glass-fiber Interlig® exhibited the greatest value of flexural strength (1083 N); followed by unidirectional glycol dimetacrylate glass-fiber Fibrante® (1022 N) and aramid fiber Kevlar® (966 N). These values represent 26%, 22% and 17% in relation to the control group (800 N), being non statistically significant difference observed among them. The group with ∅ 0,7mm orthodontic wire (871 N) had a resistance only 8% higher and similar of that of control group without reinforcement. Fracture analysis was conducted by the following scale: absence, partial, complete without separation, and complete with separation. Fracture modes observed on reinforced samples were considered more favorable, with types absent and partial seeing more frequently.
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Basaran, Mustafa Bulent. "Computational Analysis Of Advanced Composite Armor Systems". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608858/index.pdf.
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Achieving light weight armor design has become an important engineering challenge in the last three decades. As weapons becoming highly sophisticated, so does the ammunition, potential targets have to be well protected against such
threats. In order to provide mobility, light and effective armor protection materials should be used.
In this thesis, numerical simulation of the silicon carbide armor backed by KevlarTM composite and orthogonally impacted by 7.62mm armor piercing (AP) projectile at an initial velocity of 850 m/s is analyzed by using AUTODYN hydrocode. As a first step, ceramic material behavior under impact conditions is
validated numerically by comparing the numerical simulation result with the test result which is obtained from the literature. Then, different numerical simulations
are performed by changing the backing material thickness, i.e. 2, 4, 6 and 8mm, while the thickness of the ceramic is held constant, i.e. 8mm. At the end of the simulations, optimum ceramic/composite thickness ratio is sought.
The results of the simulations showed that for the backing thickness values of 4, 6 and 8mm, the projectile could not perforate the armor system. On the contrary,
the projectile could penetrate and perforate the armor system for the backing thickness value of 2mm and it has still some residual velocity. From these results, it is inferred that the optimum ceramic/composite thickness ratio is equal to about
2 for the silicon carbide and kevlar configuration.
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Marriner-Edwards, Cassian. "The development of fibre-reinforced ceramic matrix composites of oxide ceramic electrolyte". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:3af11d08-c0d8-429b-8eab-d2befc83ea74.
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Flammable solvents contained in liquid electrolytes pose a serious safety risk when used in lithium batteries. Oxide ceramic electrolytes are a safer alternative, but suffer from inadequate mechanical properties and ionic conductivity. Thin electrolyte layers resolve the issue of conductance, but accentuate the detrimental mechanical properties of oxide ceramics. The presented work has investigated oxide ceramic electrolyte reinforcement in composite electrolytes for all-solid-state batteries. Fabricating oxide ceramic electrolytes with engineered microstructure enabled development of a reinforced composite. This approach is based on the formation of 3D- porous ceramics via stereolithography printing of polymer templates from designed cubic, gyroid, diamond and bijel architectures. The microstructural parameters of templates were analysed and modified using computational techniques. Infiltration of the prepared 3D-porous electrolyte with polymeric-fibre reinforcement created the reinforced composite electrolyte. The prepared ceramic composite showed excellent reproduction of the template microstructure, good retention of ionic conductivity and enhanced mechanical properties. The final composite was composed of NASICON-type Li1.6Al0.6Ge1.4(PO4)3 oxide ceramic electrolyte and epoxy and aramid fibre reinforcement. The gyroid architecture was computationally determined as having the optimal stress transfer efficiency between two phases. The printed gyroid polymer template gave excellent pore microstructure reproduction in ceramic that had 3D-interconnected porosity, high relative density and the most uniform thickness distribution. The ceramic matrix porosity allowed for complete infiltration of reinforcement by aramid and epoxy forming the fibre-reinforced ceramic matrix composite. The interpenetrating composite microstructure with ceramic and epoxy gave a flexural strength increase of 45.65 MPa compared to the ceramic. Unfortunately, the infiltration procedure of aramid-epoxy reinforcement did not realise the full tensile strength potential of aramid fibres.
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Brown, Kenneth Alexander. "Understanding and Exploiting Wind Tunnels with Porous Flexible Walls for Aerodynamic Measurement". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73363.
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The aerodynamic behavior of wind tunnels with porous, flexible walls formed from tensioned Kevlar has been characterized and new measurement techniques in such wind tunnels explored. The objective is to bring the aerodynamic capabilities of so-called Kevlar-wall test sections in-line with those of traditional solid-wall test sections. The primary facility used for this purpose is the 1.85-m by 1.85-m Stability Wind Tunnel at Virginia Tech, and supporting data is provided by the 2-m by 2-m Low Speed Wind Tunnel at the Japanese Aerospace Exploration Agency, both of which employ Kevlar-wall test sections that can be replaced by solid-wall test sections. The behavior of Kevlar fabric, both aerodynamically and mechanically, is first investigated to provide a foundation for calculations involving wall interference correction and determination of the boundary conditions at the Kevlar wall. Building upon previous advancements in wall interference corrections for Kevlar-wall test sections, panel method codes are then employed to simulate the wind tunnel flow in the presence of porous, flexible Kevlar walls. An existing two-dimensional panel method is refined by examining the dependency of correction performance on key test section modeling assumptions, and a novel three-dimensional method is presented. Validation of the interference corrections, and thus validation of the Kevlar-wall aerodynamic performance, is accomplished by comparing aerodynamic coefficients between back-to-back tests of models carried out in the solid- and Kevlar-wall test sections. Analysis of the test results identified the existence of three new mechanisms by which Kevlar walls cause wall-interference. Additionally, novel measurements of the boundary conditions are made during the Kevlar-wall tests to characterize the flow at the boundary. Specifically, digital image correlation is used to measure the global deformation of the Kevlar walls under wind loading. Such data, when used in conjunction with knowledge of the pre-tension in the Kevlar wall and the material properties of the Kevlar, yields the pressure loading experienced by the wall. The pressure loading problem constitutes an inverse problem, and significant effort is made towards overcoming the ill-posedness of the problem to yield accurate wall pressure distributions, as well as lift measurements from the walls. Taken as a whole, this document offers a comprehensive view of the aerodynamic performance of Kevlar-wall test sections.Ph. D.
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Urbášek, Jan. "Vývoj a aplikace výpočtového modelu balisticky odolného vrstveného laminátu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-418198.
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This master thesis is aimed at computational modeling of ballistic resistant layered laminate. The introductory sections of the thesis are aimed at understanding the individual topics that are closely related to the interaction of the projectile and target and computational modeling of this process. The main goal of this thesis was to create a computational model that is able to reflect the behavior of aramid fabric during the interaction with the projectile. During the development of the computational model were used more methods of modeling and also more material models were used. For the purposes of the development of the computational model were used the available data of the companies SVS FEM s.r.o. and VVÚ s.p. The outcome of the diploma thesis is a computational model of aramid fabric which is designed for ballistic protection simulations. This model is validated on the basis of available experiments. The validated computational model is then applied to the simulation of ballistic protection.
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Sika, Charles Andrew. "Damage Tolerance of Unidirectional Carbon and Fiberglass Composites with Aramid Sleeves". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3431.
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Unidirectional carbon fiber and fiberglass epoxy composite elements consolidated with aramid sleeves were radially impacted at 5 J (3.7 ft-lbs) and 10 J (7.4 ft-lbs), tested under compression, and compared to undamaged control specimens. These structural elements represent local members of open three-dimensional composite lattice structures (e.g., based on isogrid or IsoTruss® technologies). Advanced three-dimensional braiding techniques were used to continuously fabricate these specimens. The unidirectional core specimens, 8 mm (5/16 in) in diameter, were manufactured with various sleeve patterns. Bi-directional braided sleeves and unidirectional spiral sleeves ranged from a nominal full to half coverage. These specimens were tested for compression strength after impact. This research used an unsupported length of 50.8 mm (2.0 in) specimens to ensure a strength-controlled compression failure. Compression strength of undamaged unidirectional carbon fiber and fiberglass epoxy composites is virtually unaffected by sleeve type and sleeve coverage. Fiberglass/epoxy configurations exhibited approximately 1/2 and 2/3 reduction in compression strength relative to undamaged configurations after impact with 5 J (3.7 ft-lbs) and 10 J (7.4 ft-lbs), respectively. Increasing aramid sleeve coverage and/or increasing the interweaving of an aramid sleeve (i.e., braid vs. spiral) increases the damage tolerance of fiberglass/epoxy composite elements. Damaged carbon/epoxy composites exhibited an approximate decrease in strength of 70% and 75% after 5 J and 10 J of impact, respectively, relative to undamaged configurations. The results verify that an aramid sleeve, regardless of type (braid or spiral), facilitates consolidation of the carbon fiber and fiberglass epoxy core. Not surprisingly, full coverage configurations exhibit greater compression strength after impact than half coverage configurations.
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Embley, Michael D. "Damage Tolerance of Buckling-Critical Unidirectional Carbon, Glass,and Basalt Fiber Composites in Co-Cured Aramid Sleeves". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3185.
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Compression strength after impact tests were conducted on unidirectional composite rods with sleeves. These elements represent local members of open three-dimensional composite lattice structures (e.g., based on isogrid or IsoTruss® technologies). The unidirectional cores composed of carbon, glass, or basalt fiber/epoxy composites were co-cured in aramid sleeves. Sleeve patterns included both bi-directional (unsymmetric) braids and unidirectional spiral wraps with sleeve coverage ranging from nominally half to full. The diameters were nominally 8 and 11 mm (5/16 and 7/16 in). The larger diameter had nominally twice the cross-sectional area, to quantify the effects of scaling. The specimens were long enough to encourage local buckling failure as expected in members of typical composite lattice structures. The unsupported lengths varied from 127 mm (5.0 in) to 160 mm (6.3 in). Specimens were radially impacted at mid-length with energy levels ranging from 0 to 20 J (0 to 14.8 ft-lbs) and tested in longitudinal compression to quantify the effects of local impact damage on the buckling strength. In undamaged specimens, sleeve type and sleeve coverage have no effect on the ultimate compression strength of carbon, glass, or basalt composites (7% or less standard deviation for each material). When impacted, the influence of sleeve type and sleeve coverage varies with the type of fiber in the unidirectional core. Sleeve type and coverage did not affect the compression strength after impact for fiberglass composites. On the other hand, both carbon and basalt composites exhibited improved performance with braided (vs. spiral) sleeves (up to 34% stronger) and full (vs. half) coverage (up to 38% stronger). The compression strength of carbon configurations decreases with increasing impact energy regardless of sleeve type or coverage. The higher flexibility of glass and basalt composites, however, allowed some configurations to maintain the same compression strength after impact as their undamaged counterparts, at lower impact energy levels. Doubling cross-sectional area of basalt composites significantly improves the stiffness and compression strength after impact, more than doubling the impact energy required to achieve the same compression strength.
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Nilakantan, Gaurav. "Design and Development of an Energy Absorbing Seat and Ballistic Fabric Material Model to Reduce Crew Injury Caused by Acceleration From Mine/IED Blast". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1155041442.
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Johnson, Andrew. "Establishing design characteristics for the development of stab resistant Laser Sintered body armour". Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16743.
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Stab resistant body armour had been used throughout history, with examples ranging from animal hide construction to the moulded Polycarbonate units typically used by United Kingdom (UK) Police Officers. Such protective articles have historically, and continue to present a number of issues which have shown to impair the operational performance of its wearer including but not exclusive to poor thermal regulation, large masses, and reduced manoeuvrability. A number of developments have been made in an attempt to minimise the effects of such issues. One potential solution yet to be fully explored is the utilisation of Additive Manufacturing (AM) technologies. In recent years the use of such manufacturing technologies, particularly Laser Sintering, has successfully demonstrated their suitability for a range of high performance applications ranging from Formula 1® to aerospace. Due to the fundamental additive nature of AM build processes, the utilisation of such technologies have facilitated the realisation of design concepts that are typically too expensive, difficult or impossible to create using traditional manufacturing processes. In order for AM technologies to be used for the generation of stab resistant body armour a number of historical issues and performance characteristics fundamental to ensure stab resistance is achieved must be satisfied. This body of research firstly evaluated the stab resistive performance of two of the most common materials suitable for Laser Sintering as highlighted by an initial review of AM technologies. Once an appropriate material had been highlighted it was used as the basis for further experimental testing. Such tests focussed on minimising the material thickness required to maintain an appropriate level of stab resistance within United Kingdom Home Office Scientific Development Branch (HOSDB) KR1-E1 requirement of 24 Joules of stab impact energy. Test results demonstrated that specimens manufactured from Duraform EX® required a minimum single layer thickness of 11.00 mm, and a dual layer total thickness of 9.00 mm to provide an appropriate level of stab protection within the HOSDB KR1-E1 standard. Coupled with the results generated from an investigation identifying the overlapping/imbricated assembly angle required to maintain an appropriate level of coverage across a scale structure, the stab resistant characteristics initially identified were used for the development of an imbricated scale-like assembly. Additional design features were also investigated to further minimise the total thickness of the final element design and corresponding assembled imbricated structure such features included angling strike surfaces and integrating a dual layered structure within individual elements. When the finalised imbricated assemblies were stab tested, they successfully demonstrated levels of stab resistance to the UK HOSDB KR1-E1 impact energy of 24 Joules.
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Pham, Quoc Hoan. "Analyse des réponses balistiques des fibres d'un matériau tissé à l'échelle microscopique basée sur l'homogénéisation numérique". Thesis, Lille, 2021. http://www.theses.fr/2021LILUI008.
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Cette thèse est consacrée à l’étude du comportement balistique d’un matériau tissé en utilisant une approche microscopique basée sur la technique d'homogénéisation numérique. En effet, lors d’un chargement balistique, le projectile agit localement sur la zone affectée du tissu engendrant ainsi une compression transversale des fibres. Ce phénomène a été modélisé, à l’échelle des fibres, en prenant en compte les effets des interactions fibre-fibre et l’évolution de la fraction volumique d’un fil au cours du chargement. Cette modélisation a conduit à établir une loi de comportement mécanique non-linéaire décrivant l’évolution des contraintes et des déformations apparentes dans un fil soumis à une compression transversale. La technique d’homogénéisation numérique, basée sur un volume élémentaire représentatif (VER) périodique, a été utilisée en vue d’une modélisation prenant en compte le vide entre les fibres. Cette démarche a conduit à établir une loi puissance entre la déformation apparente et la fraction volumique pour un fil sollicité en compression transversale. Ces données ont été introduites pour évaluer le comportement microscopique des fibres soumis à un impact balistique en se basant sur une approche multi-échelle. Cette analyse a conduit à une meilleure compréhension des phénomènes physiques se produisant lors d’un impact balistique d’un fil à l’échelle des fibres. Ensuite, cette modélisation a été appliquée au cas d’un tissu soumis à un impact balistique à une échelle mésoscopique (échelle d’un fil) combinée à une échelle microscopique (échelle d’une fibre) dans la zone affectée par l’impact. Cette modélisation a été validée par confrontation avec des données expérimentales, en termes de l’évolution la vitesse du projectile. L’évolution de l’énergie, de la force d'impact, des interactions fibres-fibres et de la rupture locale des fibres ont été aussi analyséesThis thesis is dedicated to the study of the ballistic behaviour of woven material using a microscopic approach based on the numerical homogenization technique. Indeed, during a ballistic loading, the projectile acts locally on the impact zone of the fabric, thus generating a transverse compression of the fibres. This phenomenon has been modelled, at the fibre scale, taking into account the effects of fibre-fibre interactions and the evolution of the volume fraction of yarn during loading. From this modelling, a non-linear mechanical behaviour law describing the evolution of apparent stress and strain in a yarn subjected to transverse compression was obtained. Then, based on a periodic Representative Volume Element (RVE), a numerical homogenization technique taking into account the void between fibres was used for modelling. A power law between the apparent deformation and the volume fraction for a yarn subjected to transverse compression was deduced based on this approach. These data were implemented into a model in order to analyse the microscopic behaviour of fibres subjected to ballistic impact based on a multi-scale approach. The analysis has provided a better prediction of the physical phenomena occurring during the ballistic impact of one single yarn at the fibre scale. Then, this model was applied to the case of one fabric subjected to ballistic impact at a mesoscopic scale (yarn scale) combined with a microscopic scale (fibre scale) in the impact zone. This model was validated by comparison with experimental data, in terms of the evolution of projectile velocity. The evolution of energy, impact force, fibre-fibre interactions and local fibre failure are also analysed
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Klova, Egidijus. "Cilindrinių kevalų statistinis modeliavimas ir analizė". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050603_140122-29706.
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The made-up software let to construct the cylindrical shell with composition in laminate by chosen test (reinforcement’s corner, number of shells), also it offer to simulate a reliability of construction and to optimise it by chosen in statistic parameters. Shell’s parameters can be evaluated like episodic variables, which are modulated with Monte - Carlo method. There is given opportunity to evaluate construction’s reliability: of the supposition that distribution of strain at shell is known, construction can be optimised when we are minimizing mass. If we want to show construction’s distribution of limitary state in dotted chart, we have to model strain’s value in every Monte – Carlo step. It is computed factors, which have influence for shell’s strain in construction’s stability. In such succession of operations is controlled the reliability of model’s evaluation. There are analysed parameters, which have the biggest influence for strain at shell. Studied the minimal shell’s mass fluctuation in dependence with dispersion and also parameter’s, of construction strain, overtop probability.
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Mazáč, Jan. "Využití kevlarových vláken v asfaltových směsích". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240054.
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Diploma thesis deals with topic of using aramid (Kevlar) fibres in road engineering in asphalt mixtures. Theoretical part of thesis is describing characteristics of aramid fibres and their technical usage. Thesis deals with research and application of aramid fibres abroad and also in Czech Republic. Practical part deals with influence of aramid fibres, namely FORTA FI fibres in mixture with modified binder for wearing course. An integral part of this thesis is a description of all methods that were used during the processing of the practical part. In the end of the thesis there are outcomes of tests and theoretical research.
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Gibson, Jason. "Nano-Particles in Multi-Scale Composites and Ballistic Applications". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5745.
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Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through two mechanisms. The first being the elongation of the fiber reinforcement contained in the resin matrix, and the second is the propagation of the crack in between the discreet fabric plies. This research aims to fundamentally study the energy absorption characteristics of various nano-particles as reinforcements in thermoset resin for high velocity impact applications. Multiple morphologies will be evaluated through use of platelet, tubular and spherical shaped nano-particles. Evaluations of the effect on stress transfer through the matrix due to the combination of nano sized and micro scale particles of milled fiber is conducted. Three different nano-particles are utilized, specifically, multi-walled carbon nanotubes, graphene, and core shell rubber particles. The difference in surface area, aspect ratio and molecular structure between the tube, platelet and spherical nano-particles causes energy absorption through different failure mechanisms. This changes the impact performance of composite panels enhanced with the nano-particle fillers. Composite panels made through the use of dispersing the various nano-particles in a non-contact planetary mixer, are evaluated through various dynamic and static testing, including unnotched cantilever beam impact, mixed mode fracture toughness, split-Hopkinson bar, and ballistic V50 testing. The unnotched cantilever beam testing showed that the addition of milled fiber degraded the impact resistance of the samples. Addition of graphene nano platelets unilaterally degraded impact resistance through the unnotched cantilever beam testing. 1.5% loading of MWCNT showed the greatest increase in impact resistance, with a 43% increase over baseline. Determining the critical load for mixed mode interlaminar shear testing can be difficult for composite panels that bend without breaking. An iterative technique of optimizing the coefficient of determination, R2, in linear regression is developed for objectively determining the point of non-linearity for critical load. This allows for a mathematical method of determination; thereby eliminating any subjective decision of choosing where the data becomes non-linear. The core shell rubber nano particles showed the greatest strain energy release rate with an exponential improvement over the baseline results. Synergistic effects between nano and micro sized particles in the resin matrix during transfer of the stress wave were created and evaluated. Loadings of 1% milled carbon fiber enhanced the V50 ballistic performance of both carbon nanotube and core shell rubber particles in the resin matrix. However, the addition of milled carbon fiber degrades the impact resistance of all nano-particle enhanced resin matrices. Therefore, benefits gained from the addition of micro-sized particles in combination with nano-sized particles, are only seen in high energy impact scenarios with micro second durations. Loadings of 1% core shell rubber particles and 1% milled carbon fiber have an improvement of 8% in V50 ballistic performance over the baseline epoxy sample for 44 mag single wad cutter gas check projectiles. Loadings of 1% multi-walled carbon nanotubes with 1% milled carbon fiber have an improvement of 7.3% in V50 ballistic performance over the baseline epoxy sample. The failure mechanism of the various nano-particle enhanced resin matrices during the ballistic event is discussed through the use of scanning electron microscope images and Raman spectroscopy of the panels after failure. The Raman spectroscopy data shows a Raman shift for the fibers that had an enhancement in the V50 performance through the use of nano-particles. The Raman band for Kevlar centered at 1,649 cm-1 stemming from the stretching of the C==O bond of the fiber shows to be more sensitive to the residual axial strain, while the Raman band centered at 1,611 cm-1 stemming from the C-C phenyl ring is minimally affected for the CSR enhanced panels due to the failure mechanism of the CSR particles during crack propagation.Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
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Peleckytė, Urtė. "Homeopatiškai paruošti preparatai iš Juglans nigra L. kevalo: biologiškai aktyvių junginių analizė ir antioksidacinio aktyvumo tyrimas". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140701_144628-19868.
Texto completoResumen
Homeopatiniais vadinami preparatai, kurie yra pagaminti iš homeopatinių žaliavų, naudojant homeopatinės gamybos procedūras. Biologiniam homeopatinių preparatų aktyvumui tirti mokslininkai naudoja tuos pačius tyrimų metodus, kaip ir kitų rūšių cheminiams preparatams [32]. Šiam tyrimui pasirinkta homeopatinė juodojo riešuto (Juglans nigra L.) kevalo tinktūra ir jos D1 bei C1 praskiedimai – tai nedidelio laipsnio skiediniai, kuriuose veikliąsias medžiagas dar galima įdentifikuoti ir koncentracijas bei biologinį aktyvumą vertinti turimais tyrimo metodais.
Mokslinės literatūros šaltiniuose skelbiama, jog juodojo riešuto kevale yra devynios pagrindinės cheminės medžiagos [29]. Nustatyta, jog riešuto viena iš pagrindinių veikliųjų medžagų yra juglonas, kuris turi citotoksinių savybių prieš melonomos, kepenų, plaučių, širdies, kraujo ląsteles [25,28,38,39]. Kadangi mokslinių tyrimų su preparatais, pagamintais iš juodojo riešuto, atlikta nedaug, todėl buvo pasirinkta ištirti polifenolinių junginių, juglono kiekį pagamintuose tirpaluose bei nustatyti jų antioksidacines savybes.
Darbo tikslas:
Homeopatiškai paruošti iš juodojo riešuto kevalo pradinę tinktūrą ir jos D1 bei C1 praskiedimus, ištirti polifenolinių junginių, juglono kiekį ir įvertinti antioksidantinį aktyvumą.
Metodai:
Pagaminta pradinė homeopatinė tinktūra (urtinktūra) ir jos skiediniai pagal Homeopatijos farmakopėjos reikalavimus (HAB 2000, 3a taisyklė).
Spektrofotometriškai nustatytas polifenolinių junginių... [toliau žr. visą tekstą]Preparations referred to as homoeopathic are those made of homoeopathic raw materials using homoeopathic manufacturing procedures. In order to measure biological activity of homoeopathic preparations scientists use the same investigation methods as with other kinds of chemical products [30]. For this study homoeopathic tincture of black walnut (Juglans nigra L.) shell and its D1and C1 dilutions have been selected as these produce low-grade solutions in which active substances still can be identified and concentrations as well as bioactivity can be assessed by available methods of testing. The scientific literature sources state that the black walnut shell contains nine basic chemical substances [29]. It is found that one of the basic active ingredients is juglone which possesses cytotoxic properties effective against melanoma, the liver, lung, heart and blood cells. [25,28,38,39]. As the studies of black walnut preparations are not so common, we have chosen to investigate the juglone amount and polyphenolic compounds in solutions and to measure their antioxidant properties. The aim of the research: To produce homoeopathically original tincture of the black walnut shell and its D1 and C1 dilutions, to explore polyphenolic compounds, the level of juglone and evaluate their antioxidant activity. The methodology: Original homoeopathic tincture (urtincture) and its solutions were produced following the specification of Homoeopathy Pharmacopoeia (HAB 2000, rule 3a)... [to full text]
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Chevalier, Caroline. "Caractérisation du comportement mécanique longitudinale d'un fil de para-aramide en sollicitation dynamique". Thesis, Valenciennes, 2016. http://www.theses.fr/2016VALE0030/document.
Texto completoResumen
Ce travail a pour objectif d’étudier le comportement mécanique d’un fil de para-aramide en sollicitation longitudinale et dynamique. Pour ce faire, nous avons conçu un nouveau dispositif expérimental permettant de réaliser ces essais à l’aide d’un canon à gaz : le Dispositif de Traction par Impact sur Fil (DTIF). Ce dispositif a subi de nombreuses modifications dans le but d’obtenir des conditions d’essais optimales. Celui-ci est associé à un dispositif de mesure par laser permettant d’obtenir le profil de vitesse du projectile ainsi que les courbes caractéristiques de Force-Déformation du fil testé. La validité de la mesure est confirmée par comparaison aux résultats obtenus avec un vélocimètre à effet Doppler, dispositif permettant de mesurer directement et de façon précise le profil de vitesse du projectile. Plusieurs campagnes d’essais sont réalisées, à la fois dans le but d’identifier les caractéristiques dynamiques d’un fil seul, et dans le but de caractériser l’influence de l’arrangement structural d’un tissu sur le comportement dynamique d’un fil. Cette étude révèle l’intervention de trois principaux paramètres structuraux, qui sont la surface de contact inter-fils totale, le nombre de points de liage et les pressions inter-fils transverses et latérales au sein du tissu, influant sur quatre principaux critères de rupture du fil, qui sont les défauts de structure et les phénomènes d’hystérésis au sein du filament, les concentrations de contraintes ainsi que les forces de frottement au niveau des interactions entre le fil testé et le reste de la structure tisséeThis work aims at studying the mechanical behavior of a para-aramid yarn in dynamic and longitudinal load. To that end, we designed a new experimental device to achieve these tests with the use of a gas gun: the Tensile Impact Test for Yarn (TITY). This device met numerous modifications in the aim to reach optimal test conditions. It is associated with a measurement device using laser and allowing obtaining the velocity profile of the projectile and the Strength-Strain characteristic curves of the tested yarn. The validity of the measure is confirmed by comparing our results with those obtained with a laser Doppler vélocimètre, device allowing measuring directly and precisely the velocity profile of the projectile. Many test campaigns are performed. Both in the aim to identify the dynamic parameters of a single and virgin yarn, and in the aim to characterize the impact of the fabric structural arrangement on the dynamic behavior of a yarn. This study reveals the intervention of three main structural parameters, which are the total inter-yarns contact surface, the number of binding points and the transvers and lateral inter-yarns pressures, having an impact on four main yarn break criteria, which are the structural defects and hysteresis phenomena inside the filament, stress concentrations and frictional forces concerning the interactions between the tested yarn and the rest of the fabric
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Gencalp, Kevser [Verfasser], Dirk [Akademischer Betreuer] Görlich, Jörg [Akademischer Betreuer] Großhans, Peter [Akademischer Betreuer] Rehling, Holger [Akademischer Betreuer] Stark y Detlef [Akademischer Betreuer] Doenecke. "Nuclear export of actin: A biochemical and structural perspective / Kevser Gencalp. Gutachter: Dirk Görlich ; Jörg Großhans ; Peter Rehling ; Holger Stark ; Detlef Doenecke. Betreuer: Dirk Görlich". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1075642396/34.
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Mantaş-Öktem, Kevser [Verfasser], Wolfgang A. [Akademischer Betreuer] Herrmann y Kai-Olaf [Akademischer Betreuer] Hinrichsen. "Reaktivitätsuntersuchungen mit Cycloheptatrienyliden-Palladium-Komplexen gegenüber N-Donorliganden und Anwendungen in der homogenen Katalyse / Kevser Mantaş-Öktem. Gutachter: Wolfgang A. Herrmann ; Kai-Olaf Hinrichsen. Betreuer: Wolfgang A. Herrmann". München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1072758172/34.
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