Literatura académica sobre el tema "Multiscale mechanical characterization"
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Artículos de revistas sobre el tema "Multiscale mechanical characterization"
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Liparoti, S., A. Sorrentino, V. Speranza y G. Titomanlio. "Multiscale mechanical characterization of iPP injection molded samples". European Polymer Journal 90 (mayo de 2017): 79–91. http://dx.doi.org/10.1016/j.eurpolymj.2017.03.010.
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Juliano, Thomas F., Aaron M. Forster, Peter L. Drzal, Tusit Weerasooriya, Paul Moy y Mark R. VanLandingham. "Multiscale mechanical characterization of biomimetic physically associating gels". Journal of Materials Research 21, n.º 8 (1 de agosto de 2006): 2084–92. http://dx.doi.org/10.1557/jmr.2006.0254.
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The mechanical response of living tissue is important to understanding the injury-risk associated with impact events. Often, ballistic gelatin or synthetic materials are developed to serve as tissue surrogates in mechanical testing. Unfortunately, current materials are not optimal and present several experimental challenges. Bulk measurement techniques, such as compression and shear testing geometries, do not fully represent the stress states and rate of loading experienced in an actual impact event. Indentation testing induces deviatoric stress states as well as strain rates not typically available to bulk measurement equipment. In this work, a ballistic gelatin and two styrene-isoprene triblock copolymer gels are tested and compared using both macroscale and microscale measurements. A methodology is presented to conduct instrumented indentation experiments on materials with a modulus far below 1 MPa. The synthetic triblock copolymer gels were much easier to test than the ballistic gelatin. Compared to ballistic gelatin, both copolymer gels were found to have a greater degree of thermal stability. All of the materials exhibit strain-rate dependence, although the magnitude of dependence was a function of the loading rate and testing method.
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Park, Byung, David Hwang, Dong Kwon, Tae Yoon y Youn-Woo Lee. "Fabrication and Characterization of Multiscale PLA Structures Using Integrated Rapid Prototyping and Gas Foaming Technologies". Nanomaterials 8, n.º 8 (27 de julio de 2018): 575. http://dx.doi.org/10.3390/nano8080575.
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Multiscale structured polymers have been considered as a promising category of functional materials with unique properties. We combined rapid prototyping and gas foaming technologies to fabricate multiscale functional materials of superior mechanical and thermal insulation properties. Through scanning electron microscope based morphological characterization, formation of multiscale porous structure with nanoscale cellular pores was confirmed. Improvement in mechanical strength is attributed to rearrangement of crystals within CO2 saturated grid sample. It is also shown that a post-foaming temperature higher than the glass transition temperature deteriorates mechanical strength, providing process guidelines. Thermal decomposition of filament material sets the upper limit of temperature for 3D printed features, characterized by simultaneous differential scanning calorimetry and thermogravimetric analysis. Porosity of the fabricated 3D structured polylactic acid (PLA) foam is controllable by suitable tuning of foaming conditions. The fabricated multiscale 3D structures have potential for thermal insulation applications with lightweight and reasonable mechanical strength.
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Abdelaziz, Amal, Eyad Masad, Amy Epps Martin y Edith Arámbula Mercado. "Multiscale Characterization of Rejuvenated RAP Binders". Journal of Testing and Evaluation 51, n.º 4 (16 de febrero de 2023): 20220229. http://dx.doi.org/10.1520/jte20220229.
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Reggente, M., M. Natali, D. Passeri, M. Lucci, I. Davoli, G. Pourroy, P. Masson et al. "Multiscale mechanical characterization of hybrid Ti/PMMA layered materials". Colloids and Surfaces A: Physicochemical and Engineering Aspects 532 (noviembre de 2017): 244–51. http://dx.doi.org/10.1016/j.colsurfa.2017.05.011.
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Pierrat, Baptiste, Nahime Al Abiad, Anicet Le Ruyet y Stéphane Avril. "Multiscale mechanical characterization of knitted abdominal wall repair meshes". Computer Methods in Biomechanics and Biomedical Engineering 23, sup1 (19 de octubre de 2020): S221—S222. http://dx.doi.org/10.1080/10255842.2020.1815310.
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Serino, Gianpaolo, Fabio Distefano, Elisabetta M. Zanetti, Giulia Pascoletti y Gabriella Epasto. "Multiscale Mechanical Characterization of Polyether-2-ketone (PEKK) for Biomedical Application". Bioengineering 11, n.º 3 (29 de febrero de 2024): 244. http://dx.doi.org/10.3390/bioengineering11030244.
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Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.
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Bigerelle, M., M. Dalla-Costa y D. Najjar. "Multiscale similarity characterization of abraded surfaces". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 221, n.º 10 (1 de octubre de 2007): 1473–82. http://dx.doi.org/10.1243/09544054jem770.
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Many surface properties are related to their topography. The characteristics of an engineering surface can be recorded as a roughness profile characterized by calculation of roughness parameters. The supposed relevant parameters are used to characterize the surface and to tailor similar surfaces with the same characteristics. The aim of this paper is to propose an alternative method based on information theory to avoid roughness parameters calculation in quantifying the similarity of two roughness profiles. The relevance of this method is emphasized using experimental profiles.
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Liao, Ning Bo, Miao Zhang y Rui Jiang. "Recent Development in Multiscale Simulation of Mechanical Properties at Material Interface". Advanced Materials Research 146-147 (octubre de 2010): 491–94. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.491.
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For nanoscale devices and structures, interface phenomena often dominate their overall thermal behavior. The feature scale of material interfaces usually originate from nanometer length and present a hierarchical nature. Considering to the limitations of the continuum mechanics on the characterization of nano-scale, the multiscale model featuring the interface could be very important in materials design. The purpose of this review is to discuss the applications of multiscale modeling and simulation techniques to study the mechanical properties at materials interface. It is concluded that a multi-scale scheme is needed for this study due to the hierarchical characteristics of interface.
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Lejček, Pavel, Jaroslav Čapek, Michaela Roudnická, Orsolya Molnárová, Jan Maňák, Jan Duchoň, Drahomír Dvorský et al. "Selective laser melting of iron: Multiscale characterization of mechanical properties". Materials Science and Engineering: A 800 (enero de 2021): 140316. http://dx.doi.org/10.1016/j.msea.2020.140316.
Texto completoTesis sobre el tema "Multiscale mechanical characterization"
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GODENZONI, CARLOTTA. "Multiscale Rheological and Mechanical characterization of Cold Mixtures". Doctoral thesis, Università Politecnica delle Marche, 2017. http://hdl.handle.net/11566/245296.
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Oggigiorno, la crescente consapevolezza sociale e politica per le questioni ambientali si sta orientando verso lo sviluppo di tecnologie a basso consumo ed emissioni. In questo contesto, tecnologie come le miscele bituminose a freddo possono rappresentare una valida alternativa ai tradizionali conglomerati bituminosi a caldo, per le pavimentazioni stradali. Inoltre, quando vengono utilizzati materiali provenienti dal riciclaggio di pavimentazioni stradali ammalorate, il consumo di aggregati vergini può essere considerevolmente ridotto.
In passato, l'uso di miscele bituminose a freddo ha riscosso limitato successo a causa dei problemi legati al tempo necessario per il completo sviluppo di resistenza e la suscettibilità all’acqua nei primi mesi di vita.
Il presente dottorato di ricerca è volto a valutare scientificamente i vantaggi/svantaggi dell’adozione di miscele bituminose a freddo.
Oltre alle tradizionali indagini di laboratorio, è stata adottata una metodologia originale basata sulla caratterizzazione multiscala del materiale, sia dal punto di vista fisico che reologico. Infatti, la miscela bituminosa a freddo può considerarsi un materiale evolutivo poiché il suo stato fisico evolve nel tempo a causa della continua perdita di umidità. In questo contesto, la caratterizzazione delle miscele bituminose a freddo deve essere sviluppata su scale temporali differenti durante la vita in servizio del materiale, e a diversi livelli di indagine (scala dimensionale).
I risultati raccolti hanno mostrato una correlazione ottimale tra i diversi livelli di indagine; a dimostrazione del fatto che il metodo di ricerca adottato può ritenersi scientificamente valido e inoltre, nessun elemento scoraggia l'uso delle miscele bituminose a freddo come strati di supporto per la sovrastruttura stradale. Ad ogni modo, i materiali impiegati devono essere adeguatamente progettati in termini di assortimento granulometrico, contenuto d’acqua e leganti (tipologia e dosaggio).Nowadays, the growing social and political awareness about environmental issues is moving towards the development of low-energy and low-emission technologies. In this context, technologies as cold mixtures may represent a valid alternative to traditional hot mix asphalt for road pavements. Moreover, when materials obtained from the recycling of old pavements are adopted, the consumption of virgin aggregate can be significantly reduced. In the past, the use of cold mixture for structural layers has attracted relatively little attention largely because of problems related to the time required for full strength to be achieved after paving and its susceptibility to early life damage by rainfall. The PhD research aimed at scientifically evaluating advantages and disadvantages of cold mixtures. Besides the traditional laboratory investigations, an original research methodology based on the multiscale characterization of the material, from both physical and rheological point of view. In fact, cold mixture can be considered as an evolutive material because its physical state evolves over time according to moisture loss. In this context, the characterization of cold mixture should be developed at different time during its in-service life (time-scale) and at different level of investigation (size-scale). Optimum correlation was found between results collected from different levels of investigation (size and time-scales); hence demonstrating the scientific validity of the adopted research approach. Based on the overall findings, no elements discourage the use of cold mixtures as support layers for pavement structure. Therefore, materials should be properly designed in terms of aggregate blend, water content and binding agents (type and dosage).
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Miri, Ramsheh Amir Kamal. "Mechanical characterization of vocal folds using a multiscale study". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119585.
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The vocal folds are two membranous lips of soft tissue located within the human larynx. During phonation, they undergo self-sustained oscillations. Common voice disorders are believed to result from excessive mechanical stresses within the vocal folds' mucosal layer. The overarching goal of the present study was to better understand the relationship between mechanical loading and vocal fold tissue response. The bulk mechanical properties of the vocal folds were initially investigated using uniaxial traction testing and shear rheometry. These methods were used to quantify the material parameters of porcine vocal folds. A linear transversely-isotropic model was used to relate stresses and strains. The assumption of incompressibility was used to reduce the number of independent parameters.The effects of water loss induced by an osmotic pressure potential on vocal fold tissue's viscoelastic properties were investigated. Uniaxial traction testing was used to impose slow-rate, cyclical extensions of porcine vocal folds while a hypertonic solution was used to absorb interstitial fluid from the tissue. The elastic modulus and the loss factor were then determined for normal and dehydrated tissues. A non-linear eight-chain hyperelastic model was used to relate the stress and the stretch of the bi-phasic tissue. Significant changes in mass were observed as a result of the traction tests. The mechanics of the vocal folds were investigated under linear poroelasticity, where interstitial fluids are assumed to be freely moving within the extracellular matrix proteins. The one-dimensional consolidation problem was used to model the contact between tissue and a spherical indenter. Atomic force microscopy based indentation data, obtained from creep and dynamic oscillation testing, were used to calibrate the model. Nanoscale viscoelastic characteristics of porcine lamina propria were characterized from the force response to frequency-dependent displacement oscillations, with an amplitude of 30-50 nm. Nonlinear laser scanning microscopy was used to visualize the morphology of extracellular matrix proteins within human and animal vocal folds. A custom-built multimodal nonlinear laser scanning microscope was used to scan fibrous proteins in human and porcine vocal folds. Collagen and elastin were imaged using second-harmonic generation and two-photon fluorescence, respectively. An experimental protocol was introduced to characterize the geometrical properties of the collagen fibrils. Nonlinear laser scanning microscopy was then used to investigate the remodeling of scarred rat vocal folds. The volume fraction of collagen was found to be 12% greater in scarred vocal fold tissue 12 month after injury. Atomic force microscopy images suggest a rope-shaped structure of collagen fibrils in the vocal folds. A hyperelastic theory was developed for collagen-reinforced soft tissues. The relevant formulation was derived for finite element simulations. The model captured the role of helical hierarchies of the collagen fibrils in the nonlinear response of vocal folds under load.Les cordes vocales sont des membranes de tissus mous situées à l'intérieur du larynx. Pendant la phonation, elles sont soumises à des oscillations auto-entretenues. Certains troubles de la voix répandus sont connus pour résulter de contraintes mécaniques excessives au sein de la muqueuse des cordes vocales. Les propriétés viscoélastiques des cordes vocales pathologiques diffèrent de celles dont les tissus sont sains. L'objectif global de cette étude est de mieux comprendre la relation entre le chargement mécanique et la réponse des tissus des cordes vocales. Les propriétés mécaniques de compression des cordes vocales ont tout d'abord été étudiées à l'aide d'essai de traction et d'un rhéomètre à cisaillement. Ces méthodes ont servi à quantifier les paramètres mécaniques de cordes vocales porcines. Un modèle linéaire, isotrope transverse a été utilisé pour la relation entre les contraintes et les déformations. La condition d'incompressibilité a permis de réduire le nombre de paramètres indépendants. Les effets de déshydratation, induite par le potentiel de pression osmotique, sur les propriétés des tissus des cordes vocales ont été étudiés. Des essais de traction uniaxiaux ont servi pour imposer des extensions cycliques à faible vitesse sur des cordes vocales porcines pendant qu'une solution hypertonique absorbait le fluide interstitiel des tissus. Le module élastique et le facteur de perte ont été calculés pour des tissus normaux et déshydratés. Un modèle d'hyperélasticité non linéaire à huit chaînes a servi pour décrire la relation entre les contraintes et les déformations du tissu biphasique. Des variations de masse significatives ont été observées à la suite des essais de traction. La mécanique des cordes vocales a été étudiée à l'aide de conditions de poroélasticité linéaire. Les fluides interstitiels sont supposés libres de mouvement au sein des matrices extra-cellulaires des protéines. Le problème de consolidation à une dimension a servi à la modélisation du contact entre les tissus mous et une indentation sphérique. Les données d'entrée du modèle étaient obtenues par la microscopie à force atomique basée sur des données d'indentation utilisant des signaux de rampe ou d'oscillations dynamiques. Des caractéristiques viscoélastiques furent mises en valeur à partir de la réponse des cordes vocales aux oscillations, dont le déplacement était contrôlé en fréquence, avec une amplitude de 30 à 50 nm. La microscopie optique non linéaire a permis la visualisation de la morphologie des matrices extra-cellulaires des protéines au sein de cordes vocales humaines et porcines. Un microscope non linéaire multimodale a été conçu pour scanner les protéines fibreuses de cordes vocales humaines et porcines. Le collagène et l'élastine ont été imagés respectivement à l'aide de la génération de second harmonique et de la fluorescence sous excitation à deux photons. L'introduction d'un protocole expérimental a servi à caractériser les propriétés géométriques des fibres de collagène. Cette méthode d'imagerie a ensuite été utilisée pour étudier le remodelage de cordes vocales de rats cicatrisées. Ceci a permis de montrer que la fraction volumique de collagène était 12% plus importante dans les tissus de cordes vocales cicatrisées 12 mois après la blessure.Les images du microscope à force atomique suggèrent que des fibres de collagène avec une structure de corde sont présentes dans les cordes vocales. Une théorie hyperélastique a été développée pour des tissus mous supportés par le collagène, ainsi que la formulation adaptée pour les calculs éléments finis. Le modèle capture le rôle de la structure hélicoïdale des fibres de collagène d'après la réponse non linéaire des cordes vocales soumises à un chargement.
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El, Azhari Idriss. "Multiscale mechanical and microstrutural characterization of titanium and zirconium carbonitride hard coatings". Doctoral thesis, TDX (Tesis Doctorals en Xarxa), 2020. http://hdl.handle.net/10803/669821.
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The present dissertation is an in-depth investigation from the macro to atomic scale of industrial wear-resistant CVD hard coatings deposited on cemented carbides for cutting tool applications. Micro-compression tests at the micro-scale and contact damage induced by means of millimetric spherical indentation were deployed to study deformation mechanisms of two systems consisting of a defined cemented carbide substrate coated with two different films: Ti(C,N) and Zr(C,N). The latter system exhibited a superior tool life in comparison to the conventional Ti(C,N) one. Several characterization techniques were used: confocal microscopy, scanning electron microscopy, focused ion beam, electron back scattered diffraction, X-ray synchrotron and atom probe tomography.
It was found that remnant structural integrity related to the absence of an extensive cracking network for Zr(C,N) - in the as deposited state - is one of the main reasons that could explain better performance in interrupted cutting. Adapted coefficient of thermal expansion toward the substrate, plastic deformation and better cohesive strength at the grain boundaries (which renders more toughness) are factors that contribute not only to this preserved structural integrity but also to the extended tool life during in-service interrupted cutting.En esta tesis doctoral se presenta una investigación extensa y detallada, desde la escala macroscópica hasta la atómica, de recubrimientos industriales - duros y resistentes al desgaste - depositados por CVD sobre carburos cementados para su aplicación como herramientas de corte. El estudio se realizó en dos sistemas recubiertos empleando diferentes capas cerámicas - Ti(C,N) y Zr(C,N) - pero sin variar el carburo cementado empleado como sustrato. Los mecanismos de deformación de ambos sistemas se evaluaron mediante ensayos de micro-compresión de pilares, así como de indentación esférica (con bolas de radios milimétricos), estos últimos buscando inducir daño de forma controlada a nivel superficial y subsuperficial. El sistema recubierto con la capa de Zr(C,N) exhibió una vida útil superior al más convencional - Ti(C,N). El estudio incluyó la implementación de varias técnicas de caracterización: microscopía confocal, microscopía electrónica de barrido, haz de iones focalizados, difracción de electrones retrodispersados, sincrotrón de rayos X, y tomografía con sonda atómica. Se encontró que la elevada integridad estructural remanente relacionada con la ausencia de fisuración interconectada en el caso de Zr(C,N) – justo después de ser depositado – es alguna de las principales razones para explicar el mayor rendimiento de este sistema recubierto en operaciones de mecanizado que involucran corte interrumpido. La adecuación del coeficiente de expansión térmica, relativo al que exhibe el sustrato, la capacidad de absorber deformación plástica, y la relevante resistencia cohesiva en los bordes de granos (lo que proporciona una mayor tenacidad) son factores que contribuyen no sólo a preservar la integridad estructural, sinó también a prolongar la vida útil de la herramienta durante condiciones de servicio que conlleven corte interrumpido.
Die vorliegende Dissertation ist eine eingehende Untersuchung vom makrobis zu der atomaren Skala von industrieller verschleißfester CVD-Hartschichten auf Hartmetallschneidwerkzeugen abgeschieden. Mikrodruckversuche und Kontaktschädigung ausgelöst durch millimetergenaue Kugel Eindruck wurden eingesetzt, um Verformungsmechanismen von zwei Systemen, bestehend aus einem definierten Hartmetallsubstrat, das mit zwei verschiedenen Schichten beschichtet ist: Ti(C,N) und Zr(C,N). Letzteres System zeigt eine höhere Standzeit als das herkömmliche Ti(C,N). Es wurden eine Vielzahl von Charakterisierungstechniken eingesetzt: Konfokale Mikroskopie, Rasterelektronenmikroskopie, fokussierter Ionenstrahl, Elektronenrückstreubeugung, Synchrotron und Atomsonden- Tomographie. Es wurde festgestellt, dass die erhaltene strukturelle Integrität in Bezug auf das Fehlen eines ausgedehnten Rissnetzwerks für Zr(C,N) - im abgeschiedenen Zustand - einer der Hauptgründe ist, der die bessere Leistung beim unterbrochenen Schnitt Verfahren erklären könnte. Angepasste Wärmeausdehnungskoeffizienten entgegen das Substrat, plastische Verformung und bessere Korngrenzen-Kohäsion (was zu mehr Zähigkeit führt) sind Faktoren, die nicht nur zu dieser erhaltenen strukturellen Integrität beitragen, sondern auch zu einer verlängerten Standzeit beim Fräsen im Einsatz.
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El, Azhari Idriss [Verfasser]. "Multiscale mechanical and microstructural characterization of titanium and zirconium carbonitride hard coatings / Idriss El Azhari". Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://d-nb.info/1216503494/34.
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Tehrani, Mehran. "Next Generation Multifunctional Composites for Impact, Vibration and Electromagnetic Radiation Hazard Mitigation". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49547.
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For many decades, fiber reinforced polymers (FRPs) have been extensively utilized in load-bearing structures. Their formability and superior in-plane mechanical properties have made them a viable replacement for conventional structural materials. A major drawback to FRPs is their weak interlaminar properties (e.g., interlaminar fracture toughness). The need for lightweight multifunctional structures has become vital for many applications and hence alleviating the out-of-plane mechanical (i.e., quasi-static, vibration, and impact) and electrical properties of FRPs while retaining minimal weight is the subject of many ongoing studies. The primary objective of this dissertation is to investigate the fundamental processes for developing hybrid, multifunctional composites based on surface grown carbon nanotubes (CNTs) on carbon fibers\' yarns. This study embraces the development of a novel low temperature synthesis technique to grow CNTs on virtually any substrate. The developed method graphitic structures by design (GSD) offers the opportunity to place CNTs in advantageous areas of the composite (e.g., at the ply interface) where conventional fiber architectures are inadequate. The relatively low temperature of the GSD (i.e. 550 C) suppresses the undesired damage to the substrate fibers. GSD carries the advantage of growing uniform and almost aligned CNTs at pre-designated locations and thus eliminates the agglomeration and dispersion problems associated with incorporating CNTs in polymeric composites. The temperature regime utilized in GSD is less than those utilized by other synthesis techniques such as catalytic chemical vapor deposition (CCVD) where growing CNTs requires temperature not less than 700 C.It is of great importance to comprehend the reasons for and against using the methods involving mixing of the CNTs directly with the polymer matrix, to either fabricate nanocomposites or three-phase FRPs. Hence, chapter 2 is devoted to the characterization of CNTs-epoxy nanocomposites at different thermo-mechanical environments via the nanoindentation technique. Improvements in hardness and stiffness of the CNTs-reinforced epoxy are reported. Long duration (45 mins) nanocreep tests were conducted to study the viscoelastic behavior of the CNT-nanocomposites. Finally, the energy absorption of these nanocomposites is measured via novel nanoimpact testing module.
Chapter 3 elucidates a study on the fabrication and characterization of a three phase CNT-epoxy system reinforced with woven carbon fibers. Tensile test, high velocity impact (~100 ms-1), and dynamic mechanical analysis (DMA) were employed to examine the response of the hybrid composite and compare it with the reference CFRP with no CNTs. Quasi-static shear punch tests (QSSPTs) were also performed to determine the toughening and damage mechanisms of both the CNTs-modified and the reference CFRP composites during transverse impact loading.
The synthesis of CNTs at 550 C via GSD is the focus of chapter 4. The GSD technique was adjusted to grow Palladium-catalyzed carbon filaments over carbon fibers. However, these filaments were revealed to be amorphous (turbostratic) carbon. Plasma sputtering was utilized to sputter nickel nano-films on the surface of the substrate carbon fibers. These films were later fragmented into nano-sized nickel islands from which CNTs were grown utilizing the GSD technique. The structure and morphology of the CNTs are evaluated and compared to CNTs grown via catalytic chemical vapor deposition (CCVD) over the same carbon fibers.
Chapter 5 embodies the mechanical characterization of composites based on carbon fibers with various surface treatments including, but not limited to, surface grown CNTs. Fibers with and without sizing were subjected to different treatments such as heat treatment similar to those encountered during the GSD process, growing CNTs on fabrics via GSD and CCVD techniques, sputtering of the fibers with a thin thermal shield film of SiO2 prior to CNT growth, selective growth of CNTs following checkerboard patterns, etc.
The effects of the various surface treatments (at the ply interfaces) on the on-axis and off-axis tensile properties of the corresponding composites are discussed in this chapter. In addition, the DMA and impact resistance of the hybrid CNT-CFRP composites are measured and compared to the values obtained for the reference CFRP samples. While the GSD grown CNTs accounted for only 0.05 wt% of the composites, the results of this chapter contrasts the advantages of the GSD technique over other methods that incorporate CNTs into a CFRP (i.e. direct growth via CCVD and mixing of CNTs with the matrix).
Understanding the behavior of the thin CFRPs under impact loadings and the ability to model their response under ballistic impact is essential for designing CFRP structures. A precise simulation of impact phenomenon should account for progressive damage and strain rate dependent behavior of the CFRPs. In chapter 6, a novel procedure to calibrate the state-of-the-art MAT162 material model of the LS-DYNA finite element simulation package is proposed. Quasi-static tensile, compression, through thickness tension, and in-plane Isopescu shear tests along with quasi-static shear punch tests (QSSPTs) employing flat cylindrical and spherical punches were performed on the composite samples to find 28 input parameters of MAT162. Finally, the capability of this material model to simulate a transverse ballistic impact of a spherical impactor with the thin 5-layers CFRP is demonstrated.
It is hypothesized that the high electrical conductivities of CNTs will span the multifunctionality of the hybrid composites by facilitating electromagnetic interference (EMI) shielding. Chapter 6 is devoted to characterizing the electrical properties of hybrid CNT-fiberglass FRPs modified via GSD method. Using a slightly modified version of the GSD, denser and longer CNTs were grown on fiberglass fabrics. The EMI shielding performance of the composites based on these fabrics was shown to be superior to that for reference composites based on fiberglass and epoxy. To better apprehend the effect of the surface grown CNTs on the electrical properties of the resulting composites, the electrical resistivities of the hybrid and the reference composites were measured along different directions and some interesting results are highlighted herein.
The work outlined in this dissertation will enable significant advancement in protection methods against different hazards including impact, vibrations and EMI events.
Ph. D.
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Valiveti, Dakshina M. "INTEGRATED MULTISCALE CHARACTERIZATION AND MODELING OF DUCTILE FRACTURE IN HETEROGENEOUS ALUMINUM ALLOYS". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253035787.
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Rubin, Matthew Aaron. "Multiscale characterization of the ultrastructure of trabecular bone in osteoporotic and normal humans and in two inbred strains of mice". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/18949.
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Gotti, Carlo. "Development and mechanical characterization of a biostable Nylon6.6 electrospun nanofibrous multiscale device for tendon and ligament replacement and simulation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15708/.
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This thesis aims to investigate electrospun structures by means their production process and morpho-mechanical characterization. Considering the results obtained, the electrospun devices developed, will be useful for tendon and ligament tissue applications.
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Residori, Sara. "FABRICATION AND CHARACTERIZATION OF 3D PRINTED METALLIC OR NON-METALLIC GRAPHENE COMPOSITES". Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/355324.
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Nature develops several materials with remarkable functional properties composed of comparatively simple base substances. Biological materials are often composites, which optime the conformation to their function. On the other hand, synthetic materials are designed a priori, structuring them according to the performance to
be achieved. 3D printing manufacturing is the most direct method for specific component production and earmarks the sample with material and geometry designed ad-hoc for a defined purpose, starting from a biomimetic approach to functional structures. The technique has the advantage of being quick, accurate, and with a limited waste of materials. The sample printing occurs through the deposition of material layer by layer. Furthermore, the material is often a composite, which matches the characteristics of components with different geometry and properties, achieving better mechanical and physical performances. This thesis analyses the mechanics of natural and
custom-made composites: the spider body and the manufacturing of metallic and non-metallic graphene composites. The spider body is investigated in different sections of the exoskeleton and specifically the fangs. The study involves the mechanical characterization of the single components by the nanoindentation technique, with a special focus on the hardness and Young's modulus. The experimental results were mapped, purposing to present an accurate comparison of the mechanical properties of the spider body. The different stiffness of components is due to the tuning of the same basic material (the cuticle, i.e. mainly composed of chitin) for achieving different mechanical functions, which have improved the animal adaptation to specific evolutive requirements. The synthetic composites, suitable for 3D printing fabrication, are metallic and non-metallic matrices combined with carbon-based fillers. Non-metallic graphene composites are multiscale compounds. Specifically, the material is a blend of acrylonitrile-butadiene-styrene (ABS) matrix and different percentages of micro-carbon fibers (MCF). In the second step, nanoscale filler of carbon nanotubes (CNT) or graphene nanoplatelets (GNP) are added to the base mixture. The production process of composite materials followed a specific protocol for the optimal procedure and the machine parameters, as also foreseen in the literature. This method allowed the control over the percentages of the different materials to be adopted and ensured a homogeneous distribution of fillers in the plastic matrix. Multiscale compounds provide the basic materials for the extrusion of fused filaments, suitable for 3D printing of the samples. The composites were tested in the
configuration of compression moulded sheets, as reference tests, and also in the corresponding 3D printed specimens. The addition of the micro-filler inside the ABS matrix caused a notable increment in stiffness and a slight increase in strength, with a significant reduction in deformation at the break. Concurrently, the addition of nanofillers
was very effective in improving electrical conductivity compared to pure ABS and micro-composites, even at the lowest filler content. Composites with GNP as a nano-filler had a good impact on the stiffness of the materials, while the electrical conductivity of the
composites is favoured by the presence of CNTs. Moreover, the extrusion of the filament and the print of fused filament fabrication led to the creation of voids within the structure, causing a significant loss of mechanical properties and a slight improvement in the electrical conductivity of the multiscale moulded composites. The final aim of this work is the identification of 3D-printed multiscale composites capable of the best matching of mechanical and electrical properties among the different compounds proposed. Since structures with metallic matrix and high mechanical performances are suitable for aerospace and automotive industry applications, metallic graphene composites are studied in the additive manufacturing sector. A comprehensive study of the mechanical and electrical properties of an innovative copper-graphene oxide composite (Cu-GO) was developed in collaboration with Fondazione E. Amaldi, in Rome. An extensive survey campaign on the working conditions was developed, leading to the definition of an optimal protocol of printing parameters for obtaining the samples with the highest density. The composite powders were prepared following two different routes to disperse the nanofiller into Cu matrix and, afterward, were processed by selective laser melting (SLM) technique. Analyses of the morphology, macroscopic and microscopic structure, and degree of oxidation of the printed samples were performed. Samples prepared followed the mechanical mixing procedure showed a better response to the 3D printing process in all tests. The mechanical characterization has instead provided a clear increase in the resistance of the material prepared with the ultrasonicated bath method, despite the greater porosity of specimens. The interesting comparison obtained between samples from different routes highlights the influence of powder preparation and working conditions on the printing results. We hope that the research could be useful to investigate in detail the potential applications suitable for composites in different technological fields and stimulate further comparative analysis.
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Reda, Ali. "A multiscale mechanical study of flax stems and fibres for the development of an in-the-field tool capable of predicting optimum retting". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN055.
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L'agriculture 4.0 se développe actuellement rapidement en termes de recherche, de développement et d'applications commerciales. L'objectif de l'agriculture 4.0 est d'utiliser la technologie pour améliorer tous les domaines de l'agriculture. L'agriculture 4.0 est tellement vaste que si l'on veut y contribuer, il faut choisir un domaine spécifique. Le domaine choisi pour l'étude de ce doctorat est la production de fibres de lin. Les fibres de lin sont des fibres naturellement solides qui peuvent être extraites des tiges de lin. Les tiges de lin ont évolué pour avoir des fibres robustes d'un diamètre de l'ordre du micromètre qui courent le long de l'extérieur de la tige et sont maintenues en place dans le tissu externe de la tige. Une fois extraites et isolées, les fibres de lin ont de nombreuses applications, allant des textiles aux matériaux composites. Afin de faciliter l'extraction mécanique des fibres de lin de leurs tiges mères, les tiges subissent un processus connu sous le nom de « rouissage ». Le rouissage entraîne la décomposition du tissu externe (appelé lamelle moyenne) entre les fibres. Une forme courante de rouissage est connue sous le nom de « rouissage de rosée ». Dans le rouissage de la rosée, des processus naturels tels que les bactéries et les champignons produisent des enzymes qui décomposent la lamelle centrale et séparent progressivement les grappes de fibres et les fibres des grappes. La durée du rouissage dépend fortement des conditions météorologiques. Un rouissage insuffisant entraîne une extraction difficile des fibres dans l'usine, tandis qu'un rouissage excessif peut compromettre la qualité des fibres. On sait depuis longtemps qu'il existe un point de rouissage optimal - même les anciens le savaient. Certains agriculteurs artisans qualifiés sont capables de juger ce point par une combinaison de manipulation manuelle des tiges, d'observation des dommages causés aux tissus externes par cette manœuvre, et aussi d'observation de la couleur et de l'odeur des tiges au cours de ce test très habile, mais artisanal. Il est clair que l'artisan effectue des tests de laboratoire rudimentaires littéralement « sur le terrain ». Il semblerait donc logique d'essayer de quantifier ces tests et de voir si un outil fiable peut être mis au point pour aider l'artisan. Et c'est exactement ce que d'autres ont tenté de faire. L'introduction de la thèse donne des exemples de tentatives de fabrication d'outils de rouissage optimal dans les années 1980 et suivantes. Inspirés par ces premiers travaux, les travaux de cette thèse tentent une caractérisation mécanique multi-échelle complète des tiges et des fibres de lin pendant un cycle de rouissage (été 2022) et, de manière quelque peu ambitieuse, réalisée en temps réel - à notre connaissance pour la première fois. La caractérisation mécanique comprend des essais mécaniques macroscopiques (flexion, écrasement et torsion de la tige), ainsi que des essais mécaniques microscopiques inédits sur des fibres de lin individuelles à l'aide de nouvelles méthodes inspirées des MEMS. En outre, les propriétés mécaniques nanoscopiques de la paroi cellulaire primaire des fibres de lin en cours de rouissage ont été caractérisées à l'aide de l'AFM par nanoindentation. Au fur et à mesure que le travail expérimental, l'analyse via la modélisation analytique et l'interprétation descendent en échelle, de la macro au nano en passant par le micro, nous en apprenons un peu plus sur la manière dont le rouissage affecte les tiges, leurs propriétés et leurs fibres. En plus de l'apprentissage, un résultat très positif du doctorat est que l'on est capable de suggérer un mécanisme de dommage induit mécaniquement dans les tiges, qui pourrait être la base d'un outil. On peut cependant noter que la nature multiparamétrique incontrôlable du sujet, par exemple le temps, signifie que plusieurs études seraient nécessaires pour confirmer sans aucun doute les observations d'un seul cycle de rouissageAgriculture 4.0, also known under several aliases such as ‘digital agriculture', ‘smart farming', and ‘e-farming' is currently developing rapidly in terms of research, development, and commercial applications. As with Agriculture 1.0, 2.0, and 3.0, the objective of Agriculture 4.0 is the use of technology to improve all areas of agriculture. In Agriculture 4.0 it is the application of microelectronics and microtechnologies. Unlike before, these technologies bring things such as the internet-of-things, big data, telecommunications, novel sensing, rapid feedback, data analysis, connectivity, artificial intelligence etc. In principle, all these areas should result in a massive modernization of farming in terms of organisation, yield, efficiency, and quality of produce. However, Agriculture 4.0 is so vast that if one is to contribute to it, even in a minor way, one has to choose a specific area to contribute. The area chosen for the study in this PhD was flax fibre production. Flax fibres are naturally strong fibres which can be extracted from flax stems. The flax stems have evolved to have robust micrometre-diameter fibres running the length of the outside of the stem, and held in place in the external tissue of the stem. Once extracted and isolated, flax fibres have numerous applications ranging from textiles to composite materials. In order to facilitate the mechanical extraction of flax fibres from their parent stems, the stems undergo a process known as ‘retting'. Retting leads to the breakdown of the external tissue between the fibres. A common form of retting is known as ‘dew retting'. In dew retting, natural processes such as bacteria and fungi result in enzymes which break down the middle lamella and gradually separate fibre bunches and fibres from bunches. The length of dew retting depends heavily on the weather. Too little retting results in difficult fibre extraction in the factory, too much retting can result in a compromise in fibre quality. It has long been known that there is an optimum retting point-even the ancients knew this. Certain skilled artisan farmers are able to judge this point via a combination of manual manipulation of the stems, observation of damage caused to the external tissue via this manoeuvre, and also observing the colour and the smell of the stems during this very skilled, but artisanal, testing. It is clear that the artisan is performing rudimentary laboratory tests quite literally ‘in-the-field'. It would seem logical therefore to try to quantify such tests and see if a reliable tool can be made to help the artisan. And indeed, this is exactly what others have attempted. The introduction of the PhD gives examples of attempts to make optimal-retting tools in the 1980s and after. Inspired by this early work, the work of this PhD attempts a full multiscale mechanical characterization of flax stems and fibres during a retting cycle (summer 2022) and, somewhat ambitiously, performed in real time-to our knowledge for the first time. The mechanical characterization involved macroscopic mechanical tests (bending, crushing, and twisting), as well as novel microscopic mechanical testing of single flax fibres using novel methods inspired by MEMS. In addition, the nanoscopic mechanical properties of the primary cell wall of retting flax fibres was characterised using nanoindentation AFM. As the experimental work, analysis via analytical modelling, and interpretation descends in scale from macro, through micro, to nano, we learn a little more of how the retting affects the stems, their properties, and their fibres. In addition to simply learning, a very positive outcome of the PhD is that one is able to suggest a mechanically-induced damage mechanism in stems which could be the basis for a tool. One can note however, that the uncontrollable multiparameter nature of the subject, e.g. the weather, means that several studies would be needed to confirm beyond doubt observations from a single retting cycle
Libros sobre el tema "Multiscale mechanical characterization"
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Ahzi, S. IUTAM Symposium on Multiscale Modeling and Characterization of Elastic-Inelastic Behavior of Engineering Materials: Proceedings of the IUTAM Symposium held in Marrakech, Morocco, 20-25 October 2002. Dordrecht: Springer Netherlands, 2004.
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(Editor), S. Ahzi, M. Cherkaoui (Editor), M. A. Khaleel (Editor), H. M. Zbib (Editor), M. A. Zikry (Editor) y B. LaMatina (Editor), eds. IUTAM Symposium on Multiscale Modeling and Characterization of Elastic-Inelastic Behavior of Engineering Materials (Solid Mechanics and Its Applications). Springer, 2004.
Buscar texto completoCapítulos de libros sobre el tema "Multiscale mechanical characterization"
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Tomar, Vikas, Tao Qu, Devendra K. Dubey, Devendra Verma y Yang Zhang. "Nanomechanics Experiments: A Microscopic Study of Mechanical Property Scale Dependence and Microstructure of Crustacean Thin Films as Biomimetic Materials". En Multiscale Characterization of Biological Systems, 21–36. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-3453-9_3.
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Oñate, Eugenio, Facundo J. Bellomo, Virginia Monteiro, Sergio Oller y Liz G. Nallim. "Characterization of Mechanical Properties of Biological Tissue: Application to the FEM Analysis of the Urinary Bladder". En Multiscale Simulations and Mechanics of Biological Materials, 283–300. Oxford, UK: John Wiley & Sons Ltd, 2013. http://dx.doi.org/10.1002/9781118402955.ch15.
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Puydt, Quentin, Sylvain Flouriot, Sylvain Ringeval, Guillaume Parry, Frédéric De Geuser y Alexis Deschamps. "Multiscale Characterization and Mechanical Modelling of an Al-Zn-Mg Electron Beam Weld". En ICAA13: 13th International Conference on Aluminum Alloys, 801–6. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118495292.ch118.
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Puydt, Quentin, Sylvain Flouriot, Sylvain Ringeval, Guillaume Parry, Frédéric De Geuser y Alexis Deschamps. "Multiscale characterization and mechanical modeling of an Al-Zn-Mg electron beam weld". En ICAA13 Pittsburgh, 801–6. Cham: Springer International Publishing, 2012. http://dx.doi.org/10.1007/978-3-319-48761-8_118.
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Daniel, Isaac M. y Jeong-Min Cho. "Multiscale Hybrid Nano/Microcomposites–Processing, Characterization, and Analysis". En Solid Mechanics and Its Applications, 161–72. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3467-0_12.
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Tomita, Y. y Y. Higa. "Multiscale Characterization of Deformation Behavior of Particulate-Reinforced Metal-Matrix Composite". En IUTAM Symposium on Computational Mechanics of Solid Materials at Large Strains, 259–68. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-0297-3_23.
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Fulcher, J. T., H. E. Karaca, G. P. Tandon, D. C. Foster y Y. C. Lu. "Multiscale Characterization of Water-, Oil- and UV-Conditioned Shape-Memory Polymer under Compression". En Mechanics of Time-Dependent Materials and Processes in Conventional and Multifunctional Materials, Volume 3, 97–103. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0213-8_14.
Texto completoActas de conferencias sobre el tema "Multiscale mechanical characterization"
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Zhang, Dongxiao, Junliang Zhao, Tianhao Wu, Haoyu Tang, Qihan Xuan y Zheng Jiang. "Multiscale Approach to Mechanical Characterization of Shale". En Sixth Biot Conference on Poromechanics. Reston, VA: American Society of Civil Engineers, 2017. http://dx.doi.org/10.1061/9780784480779.183.
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Hsiao, Kuang-Ting, James Ryals, Peter H. Wu y Ming C. Liu. "Mechanical Property Characterization of Multiscale Carbon Fibers and Carbon Nanofibers Reinforced Polymer Matrix Composite". En ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12937.
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Multiscale polymeric composite laminate reinforced by carbon micro-fibers (CFs) and carbon nanofibers (CNFs) is fabricated via an in-house developed prepreg and vacuum bag/compression molding process. The multiscale fiber system is expected to form a multiscale fiber reinforcement network inside the composite. As a result, the mechanical properties of the prepreg-processed multiscale composite laminate are expected to be different from the traditional carbon fiber reinforced composite laminate. This CNFs modified multiscale composite laminate is tested for its mechanical strength with respect to various important properties for composite aerostructures. The effects of the CNFs in the matrix sensitive properties and in the carbon micro-fiber dominated properties of the multiscale composite are revealed.
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Shah, Sachin B., Colleen Witzenburg, Mohammad F. Hadi, Hallie P. Wagner, Janna Goodrich y Victor H. Barocas. "Dissection of Porcine Ascending Aortic Media: Mechanical Characterization and Multiscale Model". En ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14610.
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Ascending thoracic aortic aneurysm (aTAA) is a pathological condition with a high risk of dissection and rupture. Clinically, management of aTAA balances the risk of rupture with that of surgery-related complications. The risk of aneurysm rupture is known to correlate with aneurysm diameter. 1,2 Aneurysms greater than 6 cm in diameter have a significantly higher risk of rupture. 1 Current guidelines for intervention suggest surgical intervention for aTAA diameters greater than 5.5cm for patients without connective tissue disorders. 1
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Zhai, Yingnan, Jose A. Colmenarez, Valentina O. Mendoza, Pengfei Dong, Kenia Nunes, Donny Suh y Linxia Gu. "Multiscale Mechanical Characterization of Cornea With AFM, SEM, and Uniaxial Tensile Test". En ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-113394.
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Abstract Cornea stiffness is associated with the progression of keratitis, aging, and glaucoma diseases. Knowing the microstructure and mechanical properties of the cornea is important for cornea tissue engineering. In this study, the microstructure and mechanical properties of the cornea from African green monkey eye were determined through multiscale methods with atomic force microscopy (AFM), scanning electron microscopy (SEM), and uniaxial tensile test. The cornea samples were dissected from the eyeball of African green monkeys. Cornea microstructures were inspected by SEM and optical microscopy for corneal stroma collagen lamellae. The aligned collagen lamellae have a width of approximately 3–6 μm. The stiffness map of cornea stroma with scanning regions of 10 × 10 μm2 and 5 × 5 μm2 was detected by AFM indentation test. The average Young’s modulus determined by AFM was 238.2 ± 32.7 kPa, which is on the same scale as the toe modulus (402.1 ± 176.7 kPa) of the stress-strain curve (linear region of 0%–5% strain) obtained from uniaxial tensile test. The heterogeneity of corneal stroma stiffness was presented in the stiffness map with line-shaped and band-shaped regions showing higher Young’s Modulus (around 250 kPa). The width of the band-shaped region is around 3.7 μm referring to collagen lamellae, while the adjacent arbitrarily shaped region with lower Young’s modulus (< 70 kPa) on the stiffness map refers to keratocytes. Corresponding histograms show two-phase characteristics with one peak at a lower Young’s modulus range of 0.027–0.574 kPa, and another peak at a higher Young’s modulus in the range of 250.0–263.3 kPa. Monkey cornea shows heterogeneous and nonlinear mechanical properties over the scale of the tests.
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Park, Sang-Hyun, Ji-Hun Kang, Yeon-Gil Jung, Ungyu Paik, Glaucio H. Paulino, Marek-Jerzy Pindera, Robert H. Dodds, Fernando A. Rochinha, Eshan Dave y Linfeng Chen. "Fabrication and Mechanical Characterization of Al[sub 2]O[sub 3]∕ZrO[sub 2] Layered Composites with Graded Microstructure". En MULTISCALE AND FUNCTIONALLY GRADED MATERIALS 2006. AIP, 2008. http://dx.doi.org/10.1063/1.2896789.
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Aktas, Levent, Sudha Dharmavaram y M. Cengiz Altan. "Multiscale Characterization of Nanocomposites Fabricated by Copulverization of Epoxy Resin and Nanoclay". En ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80380.
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Effect of nanoclay on the thermo-mechanical properties of BT250E-1 epoxy resin is investigated. Nanocomposite parts containing 0, 2 and 10wt. % of Cloisite® 30B nanoclay are fabricated by copulverization of nanoclay with epoxy resin at −25°C. Desired amounts of solid epoxy resin and nanoclay are placed into a grinder and copulverized for 20 seconds. The resulting fine powder is then cured using an APA2000 rheometer by using the time-temperature profile provided by the resin supplier. Five disk-shaped parts for each nanoclay content are fabricated. Two rectangular samples are cut out from each disk and used for characterization of mechanical properties and microstructure. Glass transition temperature is observed to deteriorate by 5% and 10% with the addition of 2 and 10wt. % nanoclay, respectively. Three-point bending test results indicate up to 28% improvement in flexural stiffness whereas flexural strength is observed to degrade by 57% over the range of nanoclay loading. Scanning electron microscopy indicates extensive nanoclay agglomeration. In order to characterize the nanoclay cluster morphology, several scanning electron micrographs are captured at 500x magnification. Nanoclay clusters and their size distribution are then identified by digital image processing. It is found that the average cluster size is 2-fold higher at nanocomposites containing 10wt.% nanoclay compared to 2wt.%. Transmission electron microscopy indicates several nanovoids trapped in the intra-cluster regions. The existence of these voids is also verified by density measurements of the cured samples of the epoxy with and without nanoclay. The reduction observed in the flexural strength is believed to be due to these nanovoids and nanoclay agglomeration.
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Rubin, Matthew A. y Iwona Jasiuk. "Multiscale Characterization of the Ultrastructure of Normal and Osteoporotic Human Trabecular Bone". En ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32591.
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In this paper we characterized hierarchical structure of healthy and osteoporotic human trabecular bone from microscale down to nanoscale. To characterize the hierarchical structure, trabecular bone was investigated at the microstructural level (i.e. trabecula, trabecular packets), sub-microstructural level (lamellar structure) and the nanostructural level (crystal-collagen collagen composite). There was an emphasis on evaluating the sub-microstructure and nanostructure of trabecular bone since detailed descriptions of the lamellar structure and of the crystal-collagen relationship in osteoporotic bone are relatively unknown. The ultrastructure of healthy and osteoporotic human trabecular bone was characterized experimentally by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The experiments also involved studying trabecular bone from C57BL/6J and C3H/HeJ mice. These mice have nearly the same size and weight, but have very different bone density. Thus, they were good candidates for a comparative study of healthy and osteoporotic human trabecular bone. TEM and SEM were used to characterize the hierarchical microstructure of trabecular bone in the inbred mice. The understanding of the hierarchical nature of healthy and osteoporotic bone microstructure is needed for a deeper understanding of the state of bone health and its mechanical properties.
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Chokhandre, Snehal, Craig Bennetts, Jason Halloran, Robb Colbrunn, Tara Bonner, Morgan H. Jones y Ahmet Erdemir. "Comprehensive Identification of Tibiofemoral Joint Anatomy and Mechanical Response: Pathway to Multiscale Characterization". En ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80200.
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The human knee joint is a complex multi-body structure, whose substructures greatly affect its mechanical response. An understanding of the multiscale mechanics of the joint is essential for the prevention and treatment of knee joint injuries and pathologies. Due to the limitations associated with in vivo experimentation, mechanical characterization of the knee joint has commonly relied on in vitro experimentation [1,2]. Predictive and descriptive studies of the mechanical function of the knee and its substructures have commonly employed computational modeling, in particular finite element (FE) analysis, which can be driven by experimental data. With the recent focus on the use of FE models of the knee joint for scientific and clinical purposes [3–5], data for model development, verification, and validation became increasingly important, especially when relying on FE analysis for decision making. An adequate representation of a joint not only depends on the specimen-specific anatomy but may also need to be informed by specimen-specific tissue properties for model development, and specimen-specific joint/tissue response to confirm model response.
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Xuan, Yue y Wei Tong. "Mechanical Characterization of Biological Tissue: Finite Element Modeling". En ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13320.
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Indentation, in addition to the traditional tensile testing, has been widely used for evaluating mechanical properties of hard materials such as metals and bone as well as soft materials like polymer and soft tissues. However, it is difficult to measure the contact area and surface deformation in conventional indentation tests of soft tissue which will bring large errors to the evaluation of the material properties. Also the assumption of isotropic property limited the usage of indentation test in characterizing the nonlinear, anisotropic properties of soft tissue thin film. In this project, 2D and 3D finite element analyses has been carried out to predict hyperelastic material response under indentation and punch tests. A novel indentation test system was developed, which made the direct measurement of local deformation and contact area possible. The apparatus consists of a transparent indenter, a digital microscope, and a computer based control and data acquisition system. The proposed testing system and associated finite element analysis are used to characterize the mechanical properties of multiscale (bulk and thin film) biological tissues.
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Johnston, Joel y Aditi Chattopadhyay. "Stochastic Multiscale Modeling and Damage Progression for Composite Materials". En ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66566.
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Modeling and characterization of complex composite structures is challenging due to uncertainties inherent in these materials. Uncertainty is present at each length scale in composites and must be quantified in order to accurately model the mechanical response and damage progression of this material. The ability to pass information between length scales permits multiscale models to transport uncertainties from one scale to the next. Limitations in the physics and errors in numerical methods pose additional challenges for composite models. By replacing deterministic inputs with random inputs, stochastic methods can be implemented within these multiscale models making them more robust. This work focuses on understanding the sensitivity of multiscale models and damage progression variations to stochastic input parameters as well as quantifying these uncertainties within a modeling framework. A multiscale, sectional model is used due to its efficiency and capacity to incorporate stochastic methods with little difficulty. The sectional micromechanics in this model are similar to that of the Generalized Method of Cells with the difference being the discretization techniques of the unit cell and the continuity conditions. A Latin Hypercube sampling technique is used due to its reported computational savings over other methods such as a fully random Monte Carlo simulation. Specifically in the sectional model, the Latin Hypercube sampling method provides an approximate 35 % reduction in computations compared to the fully random Monte Carlo method. The Latin Hypercube sampling is a stratified technique which discretizes the distribution function and randomizes the input parameters within those discretized fields. Within this multiscale modeling framework, a progressive failure theory is implemented using these stochastic methods and a modified Hashin failure theory. With a combined stochastic method and progressive failure theory, this multiscale model is capable of modeling the uncertainty and material property variations for composite materials.