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Keten, Sinan. "Size-dependent mechanical properties of beta-structures in protein materials." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60792.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 199-217).
Protein materials such as spider silk can be exceptionally strong, and they can stretch tremendously before failure. Notably, silks are made entirely of proteins, which owe their structure and stability to weak molecular interactions, in particular, hydrogen bonds (H-bonds). Beta-structures, a class of protein folds that employ dense arrays of H-bonds, are universal in strong protein materials such as silks, amyloids, muscle fibers and virulence factors. The biological recipe for creating strong, tough materials from weak bonds, however, has so far remained a secret. In this dissertation, size, geometry and deformation rate dependent properties of beta-structures are investigated, in order to provide a link between the nanostructure and mechanics of protein materials at multiple length scales. Large-scale molecular dynamics (MD) simulations show that beta-structures reinforce protein materials such as silk by forming H-bonded crystalline regions that cross-link polypeptide chains. A key finding is that superior strength and toughness can only be achieved if the size of the beta-sheet crystals is reduced to a few nanometers. Upon confinement into orderly nanocrystals, H-bond arrays achieve a strong character through cooperation under uniform shear deformation. Moreover, the size-dependent emergence of a molecular stick-slip failure mechanism enhances toughness of the material. Based on replica-exchange MD simulations, the first representative atomistic model for spider silk is proposed. The computational, bottom-up approach predicts a multi-phase material with beta-sheet nanocrystals dispersed within semi-amorphous domains, where the large-deformation and failure of silk is governed by the beta-structures. These findings explain a wide range of observations from single molecule experiments on proteins, as well as characterization studies on silks. Results illustrate how nano-scale confinement of weak bond clusters may lead to strong, tough polymer materials that self-assemble from common, simple building blocks.
by Sinan Keten.
Ph.D.
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Kappiyoor, Ravi. "Mechanical Properties of Elastomeric Proteins." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54563.
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When we stretch and contract a rubber band a hundred times, we expect the rubber band to fail. Yet our heart stretches and contracts the same amount every two minutes, and does not fail. Why is that? What causes the significantly higher elasticity of certain molecules and the rigidity of others? Equally importantly, can we use this information to design materials for precise mechanical tasks? It is the aim of this dissertation to illuminate key aspects of the answer to these questions, while detailing the work that remains to be done.
In this dissertation, particular emphasis is placed on the nanoscale properties of elastomeric proteins. By better understanding the fundamental characteristics of these proteins at the nanoscale, we can better design synthetic rubbers to provide the same desired mechanical properties.Ph. D.
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Guan, Juan. "Investigations on natural silks using dynamic mechanical thermal analysis (DMTA)." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:c16d816c-84e3-4186-8d6d-45071b9a7067.
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This thesis examines the dynamic mechanical properties of natural silk fibres, mainly from silkworm species Bombyx mori (B. mori) and spider species Nephila edulis, using dynamic mechanical thermal analysis, DMTA. The aim is not only to provide novel data on mechanical properties of silk, but also to relate these properties to the structure and morphology of silk. A systematic approach is adopted to evaluate the effect of the three principal factors of stress, temperature and hydration on the properties and structure of silk. The methods developed in this work are then used to examine commercially important aspects of the ‘quality’ of silk. I show that the dynamic storage modulus of silks increases with loading stress in the deformation through yield to failure, whereas the conventional engineering tensile modulus decreases significantly post-yield. Analyses of the effects of temperature and thermal history show a number of important effects: (1) the loss peak at -60 °C is found to be associated the protein-water glass transition; (2) the increase in the dynamic storage modulus of native silks between temperature +25 and 100 °C is due simply to water loss; (3) a number of discrete loss peaks from +150 to +220°C are observed and attributed to the glass transition of different states of disordered structure with different intermolecular hydrogen bonding. Excess environmental humidity results in a lower effective glass transition temperature (Tg) for disordered silk fractions. Also, humidity-dynamic mechanical analysis on Nephila edulis spider dragline silks has shown that the glass transition induces a partial supercontraction, called Tg contraction. This new finding leads to the conclusion of two independent mechanisms for supercontraction in spider dragline silks. Study of three commercial B. mori cocoon silk grades and a variety of processed silks or artificial silks shows that lower grade and poorly processed silks display lower Tg values, and often have a greater loss tangent at Tg due to increased disorder. This suggests that processing contributes significantly to the differences in the structural order among natural or unnatural silks. More importantly, dynamic mechanical thermal analysis is proposed to be a potential tool for quality evaluation and control in silk production and processing. In summary, I demonstrate that DMTA is a valuable analytical tool for understanding the structure and properties of silk, and use a systematic approach to understand quantitatively the important mechanical properties of silk in terms of a generic structural framework in silk proteins.
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Silva, Nuno Hélder da Cruz Simões. "Production of protein nanofibers and their application in the development of innovative materials." Doctoral thesis, Universidade de Aveiro, 2018. http://hdl.handle.net/10773/23348.
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Doutoramento em Engenharia QuímicaAs nanofibras proteicas, também conhecidas como fibrilas amilóide, estão a ganhar muito interesse devido às suas propriedades únicas, nomeadamente elevada resistência mecânica e propriedades funcionais. Estas nanofibras caracterizam-se por depósitos proteicos que resultam de um processo onde a molécula proteica adquire uma conformação estrutural em folhas-β. Dadas as suas propriedades, estas nanofibras têm sido estudadas como elementos estruturais e funcionais no desenvolvimento de materiais inovadores para aplicação em diferentes áreas como, por exemplo, em biosensores, membranas bioactivas e estruturas tridimensionais (scaffolds) para engenharia de tecidos. No entanto, uma das principais limitações na exploração de nanofibras proteicas está relacionada com o tempo necessário para a sua produção, uma vez que a fibrilação é um processo moroso que pode levar horas, dias ou até mesmo semanas. A utilização de solventes alternativos como agentes promotores de fibrilação, nomeadamente líquidos iónicos (ILs), foi recentemente demonstrada como uma via para reduzir o tempo de fibrilação. Estes resultados serviram de inspiração para estudarmos o processo de fibrilação de uma proteína modelo, a lisozima, em soluções aquosas de líquidos iónicos baseados nos catiões imidazólio ou colina com diferentes aniões derivados de ácidos orgânicos. A presença de qualquer um dos ILs testados no meio de fibrilação demonstrou ser muito eficiente obtendo-se taxas de conversão superiores a 80% de fibrilas. Seguindo uma abordagem semelhante, estudou-se também um solvente eutéctico profundo (DES) baseado em cloreto de colina e ácido acético (1:1) como possível promotor da fibrilação da lisozima, diminuindo-se o tempo de fibrilação de 8-15 h para apenas 2-3 h. Foi também demonstrado que a temperatura tem um papel fundamental na aceleração da fibrilação e tanto a temperatura como o pH influenciam significativamente as dimensões das nanofibras, nomeadamente em termos de comprimento e largura. Com o objectivo de ajustar a razão de aspecto das nanofibras (razão comprimento/largura), foram ainda estudados vários DES baseados em cloreto de colina e com ácidos mono-, di- e tri-carboxílicos, tendo-se observado que o ácido carboxílico do DES desempenha um papel fundamental no comprimento das nanofibras produzidas, sendo as razões de aspecto sempre superiores às obtidas por fibrilação apenas com cloreto de colina. O potencial das nanofibras proteicas como elementos de reforço em materiais compósitos foi avaliado pela preparação de filmes nanocompósitos à base de pululano com nanofibras de lisozima em diferentes proporções. Foram obtidos filmes transparentes com maior resistência mecânica à tracção, particularmente para as nanofibras com razões de aspecto mais elevadas. Além disso, a incorporação de nanofibras de lisozima nos filmes de pululano conferiu propriedades bioativas aos filmes, nomeadamente capacidade antioxidante e atividade antibacteriana contra a Staphylococcus aureus. O aumento do conteúdo de nanofibras nos filmes promoveu um aumento das propriedades antioxidante e antibacteriano dos filmes, sugerindo-se como possível aplicação a utilização destes nanocompósitos como filmes comestíveis e ecológicos para embalagens alimentares bioactivas. As nanofibras de lisozima foram também misturadas com fibras de nanocelulose com o objectivo de produzir um filme sustentável para a remoção de mercúrio (II) de águas naturais. Os filmes foram obtidos por filtração sob vácuo e mostraram-se homogéneos e translúcidos. A incorporação das nanofibras de lisozima nos filmes de nanocelulose promoveu um reforço mecânico significativo. Em termos da capacidade de remoção de mercúrio (II) a partir de água natural, a presença das nanofibras de lisozima proporcionou um aumento muito expressivo com eficiências de 82% (pH 7) < 89% (pH 9) < 93% (pH 11), utilizando concentrações de mercúrio (II) de acordo com o limite estabelecido nos regulamentos da União Europeia (50 μg L-1). Em suma, foi demonstrado nesta tese que o uso de líquidos iónicos e de solventes eutécticos profundos assume um papel fundamental na formação de nanofibras de lisozima morfologicamente alongadas e finas, que podem ser exploradas no desenvolvimento de bionanocompósitos para diversas aplicações desde embalagens bioactivas a sistemas de purificação de água.
Protein nanofibers, also known as amyloid fibrils, are gaining much attention due to their peculiar morphology, mechanical strength and functionalities. These nanofibers are characterized as fibrillar assemblies of monomeric proteins or peptides that underwent unfolding-refolding transition into stable β-sheet structures and are emerging as building nanoblocks for the development of innovative functional materials for application in distinct fields, for instance, in biosensors, bioactive membranes and tissue engineering scaffolds. However, one of the main limitations pointed out for the exploitation of protein nanofibers is their high production time since fibrillation is a time-consuming process that can take hours, days, and even weeks. The use of alternative solvents, such as ionic liquids (ILs), as fibrillation agents has been recently reported with considerable reduction in the fibrillation time. This fact encouraged us to study the fibrillation of a model protein, hen egg white lysozyme (HEWL), in the presence of several ILs based on imidazolium and cholinium cations combined with different anions derived from organic acids. All ILs used were shown to fibrillate HEWL within a few hours with conversion ratios over than 80% and typically worm-like nanofibers were obtained. In another study, a deep eutectic solvent (DES) based on cholinium chloride and acetic acid (1:1) was studied as a possible promoter of HEWL fibrillation, and a considerably reduction of the fibrillation time from 8-15 h to just 2-3 h was also observed. Temperature has a key role in the acceleration of the fibrillation and both temperature and pH significantly influence the nanofibers dimensions, in terms of length and width. In what concerns the nanofibers aspect-ratio, several DES combining cholinium chloride and mono-, di- and tri-carboxylic acids were studied. It was observed that carboxylic acid plays an important role on the length of the nanofibers produced with aspect-ratios always higher than those obtained by fibrillation with cholinium chloride alone. The potential of the obtained protein nanofibers as reinforcing elements was evaluated by preparing pullulan-based nanocomposite films containing lysozyme nanofibers with different aspect-ratios, resulting in highly homogenous and transparent films with improved mechanical performance, particularly for the nanofibers with higher aspect-ratios. Furthermore, the incorporation of lysozyme nanofibers in the pullulan films imparted them also with bioactive functionalities, namely antioxidant capacity and antibacterial activity against Staphylococcus aureus. The results showed that the antioxidant and antibacterial effectiveness increased with the content of nanofibers, supporting the use these films as, for example, eco-friendly edible films for active packaging. Lysozyme nanofibers were also blended with nanocellulose fibers to produce a sustainable sorbent film to be used in the removal of mercury (II) from natural waters. Homogenous and translucent films were obtained by vacuum filtration and the incorporation of these nanofibers in a nanocellulose film promoted a considerable mechanical reinforcement. In terms of the capacity to remove mercury (II) from natural water, the presence of lysozyme nanofibers demonstrated to increase expressively the mercury (II) removal with efficiencies of 82% (pH 7) < 89% (pH 9) < 93% (pH 11), using realistic concentrations of mercury (II) under the limit established in the European Union regulations (50 μg L-1). In sum, it was demonstrated in this thesis that the use of ionic liquids and deep eutectic solvents can accelerate the formation of long and thin lysozyme nanofibers that can be explored as nanosized reinforcing elements for the development of bionanocomposites with applications ranging from food packaging to water purification systems and nanotechnology
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Clemments, Alden Michael. "A Study Of The Physicochemical Properties Of Dense And Mesoporous Silica Nanoparticles That Impact Protein Adsorption From Biological Fluids." ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/639.
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At the intersection of materials chemistry and biology, biomaterials have been successfully employed in an array of medical applications. From diagnostic tools to targeted drug delivery, the modular physical and chemical properties of these materials provide numerous applications. For example, porous nanoparticles have been widely integrated as vehicles to carry chemotherapeutics to localized tumor sites. By encapsulating these cytotoxic compounds within a porous framework, the commonly associated adverse side effects of conventional chemotherapeutics, such as Doxorubicin, have been greatly reduced. One such material, mesoporous silica, has received widespread attention due to its excellent biocompatibility, high surface area to mass ratio, tunable pore diameters and volumes, and robust surface chemistry. However, recent studies have demonstrated that exposing silica nanoparticles, and other synthetic materials, to biological milieu envelops the particles in layers of proteins and biomolecules. The resulting protein coat, known as the "protein corona", has been shown to have profound effects on bioavailability, cellular targeting, and cytotoxicity. Thus, in order to develop safe and effective particle-based therapies, it is of utmost importance to establish a more thorough understanding of this process.
To examine how changes in surface chemistry influence protein adsorption, monodisperse, spherical mesoporous silica nanoparticles, ca. 50 nm, were modified with a variety of surface functionalizations, -NH2, -COOH, and -PEG. Exposing these materials to biological fluid revealed drastically different protein fingerprints, suggesting a strong correlation between the surface chemistry and the identity and composition of the protein corona. Quantification of the protein corona, i.e. mg protein/mg particles, was then achieved by performing thermogravimetric analysis. These values, in concert with spectral counts obtained by shotgun proteomics, illustrates a method for quantifying individual proteins present in the corona.
Spherical, silica particles of varying diameters, 70-900 nm, were then synthesized to investigate how particle diameter may affect the biomolecular identity of the protein corona. Applying the previously described methods, it was found that mesoporous particles exhibit a higher affinity for low-molecular weight proteins compared to dense silica particles of similar diameters.
Finally, stochastic optical reconstruction microscopy (STORM) was used to map protein adsorption/diffusion throughout as-prepared (pore diameter ~ 30 Å) .and large pore (pore diameter > 60 Å) mesoporous silica particles. By collecting three-dimensional data on the protein-adsorbed materials, a sphere-fitting algorithm could be applied to determine the center and radius of the host particle. This calculation demonstrated that the depth by which specific proteins diffused into the porous framework was a function of both the protein's molecular weight as well as the pore diameter.
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Kopuletá, Ema. "Struktura a vlastnosti nanokompozitních sítí kolagen/HAP." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-233390.
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Polymerní biomateriály jsou jedním ze současných populárních témat vzhledem k možnosti potenciální aplikace v tkáňovém inženýrství a řízeného dávkování léčiv v organismech. Kolagen je jako jeden z nejčastěji se vyskytujících proteinů zvláště zajímavý díky svým rozmanitým vlastnostem bez imunoreakce organismu příjemce. Tato práce je zaměřena na samouspořádávací procesy, kinetiku, obecné zákonitosti řídící proces samouspořádání a mechanické vlastnosti kolagenních roztoků. Dále je zkoumán efekt hydroxyapatitových nanočástic na samouspořádávání kolagenu a mechanické vlastnosti výsledných nanokompozitních hydrogelů. Jsou objasněny možné mechanismy interakcí mezi kolagenem I a hydroxyapatitem spolu s popisem vývoje struktury a vlastností na různých úrovních struktury. Byly měřeny a molekulárně interpretovány závislosti viskoelastických veličin na smykové rychlosti spolu s viskoelastickým chováním. Dále byla studována struktura kolagenních scaffoldů a určen vliv HAP a síťování. Závěrem byly diskutovány výsledky v souvislosti s jejich aplikovatelností v tkáňovém inženýrství chrupavek tvrdých tkání a v regenerativní medicíně.
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Chopra, Prateek. "Effective mechanical properties of lattice materials." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39436.
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Lattice materials possess a spatially repeating porous microstructure or unit cell. Their usefulness lies in their multi-functionality in terms of providing high specific stiffness, thermal conductivity, energy absorption and vibration control by attenuating forcing frequencies falling within the band gap region. Analytical expressions
have been proposed in the past to predict cell geometry dependent effective material properties by considering a lattice as a network of beams in the high porosity limit. Applying these analytical techniques to complex cell geometries is cumbersome. This precludes the use of analytical methods in conducting a comparative study involving complex lattice topologies. A numerical method based on the method of long wavelengths and Bloch theory is developed here and applied to a chosen set of lattice geometries in order to compare effective material properties of infinite lattices. The proposed method requires implementation of Floquet-bloch transformation in conjunction with a Finite Element (FE) scheme. Elastic boundary layers emerge from surfaces and interfaces in a finite lattice, or an infinite lattice with defects such as cracks. Boundary layers can degrade effective
material properties. A semi-analytical formulation is developed and applied to a chosen set of topologies and the topologies with deep boundary layers are identified. The methods developed in this dissertation facilitate rapid design calculation and selection of appropriate core topologies in multifunctional design of sandwich
structures employing a lattice core.
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Lawson, Nathaniel C. "Mechanical properties of dental impression materials." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2008r/lawson.pdf.
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Ajwani, Anita. "Mechanical properties of bio-absorbable materials." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020133/.
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Calvo, de la Rosa Jaume. "Mechanical and functional properties in magnetic materials." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667865.
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This doctoral Thesis has been focused on the preparation of magnetic materials by different methods, the characterization of their structural characteristics, and the understanding of their mechanical and magnetic properties. Furthermore, a big effort has been paid to investigate the frequency-dependent functional properties of different materials, which are increasingly demanded in novel technological applications. Moreover, this work presents this characterization in a wide range of frequencies, from the kHz to the THz.
In the first chapter, the reader will find an introduction to the topic and the state of the art of those materials that have been synthesized and developed in this Thesis. Then, the general goals of our research are described.
Chapter II provides all the needed fundamental theory to accomplish with the previously stated goals. The concepts exposed here will be used later in the following chapters where the results will be shown and discussed. Moreover, this chapter does not only pretend to give the essential notions used in the following chapter, but we also aim to provide a useful guide to anyone who starts working on this field.
All the materials, devices, software, and experimental conditions used in this Thesis are described in Chapter III. Here, we describe these aspects in detail in order to allow an agile discussion in the following chapters.
The first experimental chapter is Chapter IV, where the synthesis of copper ferrite nanoparticles by mean of sol-gel and co-precipitation is described. The sol-gel process is optimized through of design of experiments (DoE) approach. The results of the mechanical and magnetic characterization of solid pellets fabricated with the previously synthesized nanoparticles are also shown in this chapter. Finally, by using statistical methods a direct experimental correlation between the mechanical and magnetic properties is found in this material.
Another material, a carbon nanotube–based nanocomposite, is studied in Chapter V. This novel material is first structurally characterized in order to understand its magnetic properties. A big effort is paid on the study of the magnetic relaxation of this material, which has not been previously reported as far as we know.
The investigation of soft magnetic materials (SMM) and composites (SMC) can be found in Chapter VI. The actual SMCs are first structurally and magnetically characterized. Their magnetic properties in the kHz and MHz frequency range are also investigated, showing the better performance of the SMC at high frequencies. In the second part of the chapter, the development on new SMC’s formulations is described. The developed materials are potentially useful for applications in the kHz and MHz frequency range.
The frequency is raised in Chapter VII. Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the optical and dielectric properties of two different semiconductor oxides from 180 GHz to 3 THz. The signal processing and the interpretation of the effect that different characteristics of the sample may have on the observed properties are discussed. In this chapter, magnetic materials are not investigated because the Fresnel
model – which is the base of this technique - assumes a non-magnetic response of the material.
The work described in Chapter VIII is completely different from the previous ones. In this case, we investigate the manipulation of the magnetic moments by using surface acoustic waves (SAWs). The experiments done in this chapter lead to interesting observation about the potentiality of the use of SAWs to accelerate the magnetic moment reversal in magnetic nanoparticles.Esta Tesis Doctoral se centra en el estudio de materiales magnéticos en su conjunto, tanto desde la síntesis hasta sus propiedades mecánicas y funcionales finales. Además, ha habido un especial interés en el estudio de las propiedades funcionales en un amplio rango frecuencial. De este modo, en el primer capítulo, el lector puede encontrar una introducción al campo de investigación, así como también el estado del arte de aquellos materiales que se han sintetizado y desarrollado en esta Tesis. Por otro lado, en el Capítulo II se aportan todos los conceptos teóricos necesarios para el siguiente desarrollo de la Tesis. Además, los materiales, dispositivos, software y condiciones experimentales utilizados durante el desarrollo de esta investigación están descritos en el Capítulo III. El Capítulo IV es la primera parte experimental de la Tesis, y en la que se describe la síntesis de nanopartículas de ferrita de cobre vía sol-gel y coprecipitación. Además, se estudian las propiedades magnéticas y mecánicas en bulk, y se analiza su correlación empírica. El Capítulo V está dedicado al estudio de un nuevo material: un nanocompuesto magnético basado en nanotubos de carbono. Inicialmente se caracteriza química y estructuralmente para después centrarse en las propiedades magnéticas. Se realiza, además, un detallado estudio de su relajación magnética. Por otro lado, en el Capítulo VI, se investigan materiales magnéticos blandos. Inicialmente se analizan los materiales actualmente utilizados, mientras que en una segunda parte se desarrollan nuevas formulaciones con interesantes propiedades tecnológicas. En el Capítulo VII se presenta el estudio de las propiedades ópticas y dieléctricas en el rango de los THz. Se describe detalladamente el método, análisis de señal, y efecto de las características físicas de la muestra sobre la medida. Finalmente, también se propone un método para cuantificar el efecto de la porosidad de las muestras. Por último, el Capítulo VIII se investiga la manipulación del momento magnético mediante estímulos mecánicos como las ondas acústicas superficiales (SAW, en inglés). Se observa una clara variación experimental con la aplicación de las SAWs, y se relaciona matemáticamente esta variación con la frecuencia y potencia de las SAWs.
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Wang, Ning. "Microstructures and mechanical properties of nanocrystalline materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ28077.pdf.
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Whitty, Justin Paul Michael. "The Thermo-Mechanical Properties of Auxetic Materials." Thesis, University of Bolton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494271.
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Fan, Zhongyun. "Microstructure and mechanical properties of multiphase materials." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/776187/.
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A systematic method for quantitative characterisation of the topological properties of two-phase materials has been developed, which offers an effective way for the characterisation of twophase materials. In particular, a topological transformation has been proposed, which allows a two-phase microstructure with any grain size, grain shape and phase distribution to be transformed into a three-microstructural-element body (3-E body). It has been shown that the transformed 3·E body is mechanically equivalent along the aligned direction with the original microstructure. The Hall·Petch relation developed originally for single-phase metals and alloys has been successfully extended to two~ductile-phase alloys. It has been shown that the extended Hall- Petch relation can separate the individual contribution to the overall efficiency of different kinds of boundaries as obstacles to dislocation motion. A new approach to deformation behaviour of two-ductile-phase alloys has been developed based on Eshelby's continuum transformation theory and the microstructural characterisation developed in this thesis. In contrast to the existing theories of plastic deformation, this approach can consider the effect of microstructural parameters, such as volume fraction, grain size, grain shape and phase distribution. In particular, the interactions between particles of the same phase have also been taken into account by the topological transformation. Consequently, the newly developed theory can be applied in principle to a composite with any volume fraction. This approach has been applied to various two-ductile-phase alloys to predict the true stress·true strain curves, the internal stresses and the in situ stress and plastic strain distribution in each microstructural element. It is found that the theoretical predictions are in very good agreement with the experimental results drawn from the literature. A new approach has also been developed for the prediction of the Young's moduli of particulate two-phase composites. Applications of this approach to AVSiCp and Co/WCp composite systems and polymeric matrix composites have shown that the present approach is superior to both the Hashin and Shtrikman's bounds and the mean field theory in terms of the good agreement between the theoretical predictions and the experimental results from the literature. Furthermore, this approach can be extended to predict the Young's moduli of multiphase composites by iteration. This iteration approach has been tested on some Ti-6Al- 4V-TiB composites. An experimental investigation has being carried out to study the in situ Ti-6AI-4V-TiB (hereafter, Ti/TiB is used for convenience) metal matrix composites produced through a rapid solidification route. Production of in situ Ti/fiB metal matrix composites through rapid solidification route can completely exclude problems such as wetting and chemical reaction encountered by alternative production routes. The relevant microstructural phenomena in in situ Ti/TiB metal matrix composites, such as the growth habit of TiB phase and the w-phase transformation, have also been investigated. The TiB phase in the consolidated composites exhibits two distinguished morphologies: needle-shaped TiB and nearly equiaxed TiB. The needle-shaped TiB phase formed mainly from the solidification process always grows along the [010] direction of the B27 unit cell, leaving the cross-section of the needles consistently enclosed either by (100) and {101 1 type planes or by (100) and {102l type planes. It is also found that the cross-sections of the nearlyequiaxed TiB particles formed from the B supersaturated Ti solid solution are also bounded by the same planes as above, although the growth rate along the [010] direction has been considerably reduced. Experiments have also been perfonned to investigate the effect of pre-hipping heat treatments on the microstructure of RS products. It is found that pre-hipping heat treatments at a temperature below 800°C can lead to the precipitation of fine equiaxed TiB particles from the B super-saturated Ti solid solution, which are uniformly distributed throughout the a+B matrix. The majority of those TiB precipitates do not grow up by Ostwald ripening process after long time exposure at higher temperature. Microstructural examination has confirmed the existence of a B to w transformation in RS Ti- 6AI-4V alloys with and without B addition after consolidation. In addition, the B to w transformation has also been observed in RS Ti-Mn-B alloys after consolidation. Systematic electron diffraction work on the B-phase offers a strong experimental evidence for the B to W transformation mechanism proposed by Williams et al.
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Brakus, Josko. "Mechanical properties of natural materials : an overview." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11553.
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Rajkumar, Ananth. "Mechanical properties of microsphere based composite materials." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7276.
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Mestrado em Ciência de MateriaisIn this experimental study two different types of composite materials were prepared and their mechanical behavior was investigated. The first group consists of porous material made from sintering a mixture of micron size glass and metal spheres. Though the porous compacts made from glass microspheres have been already investigated, the main aim of the present work is to study the effect of varying the proportion of the metal spheres on the mechanical strength of the final sintered porous material. The results presented herein show that mixing metal microspheres always results in diminishing of the fracture strength of the final material and the decrease is first proportional to the volume ratio but after a certain percentage the material becomes very week; a provisional explanation is suggested. The fracture path and surface in disc type specimen broken under a flexural stress were also studied by optical microscopy. The second composite material studied consists of hollow metal spheres embedded in a polymer matrix; the general aim is to prepare lightweight armour for energy absorption under impact. Composites were made by mixing the millimeter size hollow aluminum spheres in a two-part epoxy and subsequent thermal curing of the mixture. The tests on the cured samples showed that they generally had many voids and the strength was low. An improved procedure was devised that led to considerable reduction of voids and consequently an improvement in the strength.
No trabalho aqui apresentado foram estudados dois tipos de materiais compósitos. O primeiro grupo de materiais consiste em materiais porosos obtidos a partir de sinterização de uma mistura de microesferas metálicas com microesferas de vidro. As propriedades dos materiais porosos preparados com apenas microsferas de vidro já foram estudadas; o estudo aqui descrito tem como objectivo investigar a influencia de misturar microesferas metálicas nas propriedades mecânicas do produto final. Os resultados indicam que as microesferas metálicas diminuem a resistência do material e essa diminuição é dependente da concentração de esferas metálicas; após certa concentração a diminuição é acentuada. Propõe-se uma explicação provisória. Também foi estudada a morfologia de fractura utilizando a técnica de microscopia óptica. O segundo grupo de materiais foi preparado a partir de esferas ocas metálicas e uma resina. O objectivo final é preparar um material leve mas resistente a impactos. Foram preparados materiais compósitos utilizando a técnica convencional que resultou em amostras com lacunas. A nova técnica aqui apresentada diminui consideravelmente este problema e os compósitos preparados com esta técnica tem quase dobro de resistência mecânica.
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Perera, M. Mario. "Dynamic Soft Materials with Controllable Mechanical Properties." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1595847753887897.
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Butsch, Susan Laurel. "Mechanical and physical properties of particulate reinforced composites." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020333/.
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Root, Samuel E. "Mechanical Properties of Semiconducting Polymers." Thesis, University of California, San Diego, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10745535.
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Mechanical softness and deformability underpin most of the advantages offered by semiconducting polymers. A detailed understanding of the mechanical properties of these materials is crucial for the design and manufacturing of robust, thin-film devices such as solar cells, displays, and sensors. The mechanical behavior of polymers is a complex function of many interrelated factors that span multiple scales, ranging from molecular structure, to microstructural morphology, and device geometry. This thesis builds a comprehensive understanding of the thermomechanical properties of polymeric semiconductors through the development and experimental-validation of computational methods for mechanical simulation. A predictive computational methodology is designed and encapsulated into open-sourced software for automating molecular dynamics simulations on modern supercomputing hardware. These simulations are used to explore the role of molecular structure/weight and processing conditions on solid-state morphology and thermomechanical behavior. Experimental characterization is employed to test these predictions—including the development of simple, new techniques for rigorously characterizing thermal transitions and fracture mechanics of thin films.
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Werniewicz, Katarzyna. "Fe-based composite materials with advanced mechanical properties." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-38543.
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In this study a series of novel Fe-based materials derived from a bulk metallic glass-forming composition was investigated to improve the ductility of this high-strength glassy alloy. The interplay between the factors chemistry, structure and resulting mechanical properties was analyzed in detail. It has been recognized that subtle modifications of the chemical composition (carbon addition) lead to appreciable changes in the phase formation, which occurs upon solidification (from a single-phase structure to composite materials). As a consequence, significant differences in the mechanical response of the particular samples have been observed.
The materials developed here were fabricated by centrifugal casting. To explore the structure features of the as-cast cylinders, manifold experimental techniques (X-ray diffraction, optical, as well as electron microscopy) were employed. The occurrence of the numerous reflections on the X-ray diffraction patterns has confirmed the crystalline nature of the studied Fe-based alloy systems. The subsequent extensive research on their deformation behavior (Vickers hardness and room temperature compression tests) has revealed that, although the glass-forming ability of the investigated compositions is not high enough to obtain a glassy phase as a product of casting, excellent mechanical characteristics (high strength - comparable to that of the reference bulk metallic glass (BMG) - associated with good ductility) were achieved for the “composite-like” alloys. In contrast, the single phase cylinders, subjected to compressive loading, manifested an amazing capacity for plastic deformation – no failure occurred.
The fracture motives developed during deformation of the “composite-structured” samples were studied by scanning electron microscopy. The main emphasis has been put on understanding the mechanisms of crack propagation. Owing to the structural complexity of the deformed samples, it was crucial to elucidate the properties of the individual compounds. Based on the obtained results it was concluded that the coexistence of a soft f.c.c. γ-Fe phase in combination with a hard complex matrix is responsible for the outstanding mechanical response of the tested composites. While the soft particles of an austenite contribute to the ductility (they hinder the crack propagation and hence, cause unequivocal strain-hardening), the hard constituents of the matrix phase yield the strength.
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Kock, Jeffrey Wayne. "Physical and Mechanical Properties of Chicken Feather Materials." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10555.
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Materials derived from chicken feathers could be used advantageously in composite building material applications. Such applications could potentially consume the five billion pounds of feathers produced annually as a by-product of the U.S. poultry industry. To aid the development of successful applications for chicken feather materials (CFM), the physical and mechanical properties of processed CFM have been characterized in this research. Results describing the moisture content, aspect ratio, apparent specific gravity, chemical durability, Youngs modulus, and tensile strength for processed CFM and specifically their fiber and quill components are presented herein. Processed chicken feather fiber and quill samples were found to have similar moisture contents in the range of 16 - 20%. The aspect ratio (i.e., length/diameter) of samples were found to be in the range of 30 - 50, and the fiber material was found to have a larger aspect ratio than the quill material. A comparison with values in the literature suggests that different processing regimes produce CFM with higher aspect ratios. Samples were found to have apparent specific gravities in the range of 0.7 - 1.2, with the fiber material having a higher apparent specific gravity than the quill material. A comparison with values in the literature suggests that apparent specific gravity results vary with fiber length and approach the value for keratin as fiber length decreases and internal voids become increasingly accessible. Chemical durability results showed that CFM rapidly degrade in highly alkaline (pH=12.4) environments and are, thus, likely incompatible with cement-based materials without special treatment. The Youngs modulus of processed chicken feather materials was found to be in the range of 3 - greater than 50 GPa and, thus, comparable to the Youngs moduli of other natural fibers. The tensile strength of oven-dried samples was found to be in the range of 10 - greater than 70 MPa. In agreement with results in the literature, the fiber material was found to have a greater tensile strength than the quill material. Finally, a simplified approach for comparing the effective Youngs moduli and effective tensile strengths of various processed CFM samples was introduced.
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Thibaud, Denoyelle. "Mechanical properties of materials made of nano-cellulose." Thesis, KTH, Hållfasthetslära (Inst.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-29581.
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Recent experimental findings have demonstrated great mechanical properties of nanopaper compared to ordinary paper. In this work, we have studied the formation of the elastic modulus of paper. Our goal was to investigate the contribution of fibers, fiber bonds and network structure. A 2D finite element network model was developed to study the elastic properties of nanopaper. The model can handle very dense networks of large sizes. Networks were composed of bonded, curved and randomly oriented fibers. The fiber interaction was modeled with a bonding contact. The numerical analysis was compared with theoretical models available in the literature and experimental measurements. Analysis showed that the fiber stiffness, density and the aspect ratio are the most influential parameters of those investigated with dense isotropic networks. The bond activation and fiber curl affect the modulus only in relatively sparse networks.Aktuella experimentella mätresultat visar att "nanopapper" (papper som är gjort av nanocellulosa) kan ha överlägsna mekaniska egenskaper jämfört med ett vanligt papper. I detta arbete har vi studerat hur de elastiska egenskaperna hos nanopapper påverkas av fibrer, fiberinteraktioner och pappersstruktur. En 2D finit-element modell har utvecklats för att studera de elastiska egenskaperna hos nanopapper. Modellen kan analysera mycket stora pappersark med hög densitet. Papperet representerades med krökta slumpmässigt ordnade fibrer bundna till varandra. Interaktionen mellan fibrerna modellerades kontakten mellan fibrerna modellerades med en penalty-metod. Resultaten från numeriska beräkningar jämfördes med olika teoretiska modeller och experimentella mätningar. Analysen visade att fiberstyvhet, densitet och fiberstorleksförhållandet är de enda av de undersökta parametrarna som påverkade de elastiska egenskaperna hos isotropt nanopapper med hög densitet. Så kallad "bindningsaktivering" och fibrernas krökning påverkade E-modulen bara hos ett relativt glest papper.
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Xu, Wei-Hua. "Mechanical properties of materials at micro/nano scales /." View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20XU.
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Kikuta, Michael Thomas. "Mechanical Properties of Candidate Materials for Morphing Wings." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/36152.
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The research presented in this thesis investigates the mechanical properties of candidate materials that could be used as a skin for a morphing wing. A morphing wing is defined as a wing that changes shape. Although engineers have been designing different morphing wing configurations, there has been limited research investigating materials that could be used as a skin for a morphing wing. Specifically, after investigating the different morphing wing abilities engineers at Virginia Tech are designing, criteria were determined for candidate materials. A suitable skin material for a morphing wing will have to be elastic, flexible, have high recovery, resistant to different weather conditions, resistant to abrasions and chemicals, and have a hardness number high enough to handle the aerodynamic loads of the aircraft while in flight. Using some of the preceding criteria, different materials were selected that are readily available in the commercial market. The materials tested were a type of thermoplastic polyurethanes, copolyester elastomer, shape memory polymer, or woven materials that are made out of elastane yarns.
The first study determined the required forces to strain the material in a uniaxial direction. A test stand was designed with a gripping device to hold the material. By grounding one side of the material, the other side of the material was pulled using a winch. Using a force transducer and a string potentiometer the required forces and the amount the material was strained was recorded, respectively. Utilizing the same test stand, the amount the material recovered was also acquired. Also, by measuring how much the material necked the elongation ratio was calculated. The final test determined if the forces "relaxed" after being strained to a stationary position. It was found that each material performed differently, but some materials were definitely better suited for morphing wing material. The materials that were made out of thermoplastic polyurethanes, copolyester elastomer, and shape memory polymer required less force and were able to strain more, when compared to the woven materials.
The second study determined if the material could be strained in a biaxial direction. The reason for this was for a better understand how the material would perform if the material was strained to an extreme condition. A test stand was designed using the same principles and components as the uniaxial test stand. The only difference was additional sensors were required to measure the force and strain along the other axis. Although a recovery analysis was warranted for the biaxial experiments, most of the materials test failed while being strained a small amount. Also, the material strained a lot less before ripping, when compared to the straining capabilities when only being strained in the uniaxial direction. After conducting the experiments, the results were similar to the uniaxial experimental results. In terms of required forces to strain the material, the thermoplastic polyurethanes and the copolyester elastomer required less force, when compared to the woven materials. The only advantage of the woven materials was they did not break.
The final study determined how much the material deflected while being subjected to a pressure load before breaking. The test stand used an air compressor to supply a pressure load to the material, while a laser vibrometer measured how much the material deflected. A regulator was used to control the amount of pressure that was applied to the material. As the pressure load was increased, the material deflected more. The test stand also determined the maximum sustained pressure load the material could handle before breaking. After conducting all the experiments and analyzing the data, it was found woven materials are not suitable as a skin material. The reason air is allowed to pass through the woven material. Therefore, woven materials could not sustain the aerodynamic loads of an aircraft while in flight. The rest of the materials performed differently. Specifically if the material strained well and required less force while conducting the uniaxial and biaxial experiments, those materials could not sustain a high pressure load. Yet, the materials that did not strain well and required more force were able to handle a larger sustained pressure load.Master of Science
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Kau, Chia-Chiun James. "Mechanical properties and deformation mechanisms of polyurethane materials." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055883413.
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Drexler, Jason. "Materials Engineering for Enhanced Tissue Scaffold Mechanical Properties." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275492023.
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Forsik, Stéphane Alexis Jacques. "Mechanical properties of materials for fusion power plants." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/221725.
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Fusion power is the production of electricity from a hot plasma of deuterium and tritium, reacting to produce particles and 14 MeV neutrons, which are collected by a cooling system. Their kinetic energy is transformed into heat and electricity via steam turbines. The constant ux of neutrons on the rst wall of the reactor produces atomic displacement damage through collisions with nuclei, and gas bubbles as a result of transmutation reactions. This leads eventually to hardening and embrittlement. Designing a material able to withstand such intensity of damage is one of the main aims of research in the field of controlled fusion. In the past decades, many experiments have been carried out to understand the formation of radiation-induced damage and quantify the changes in mechanical properties of irradiated steels, but the lack of facilities prevents us from testing candidate materials in a fusion-like environment. Modelling techniques are utilised here to extract information and principles which can help estimate changes in steels due to damage. The elongation and yield strength of various low-activation ferritic/martensitic steels were modelled by neural networks and Gaussian processes. These models were used to make predictions which were compared to experimental values. Combined with other techniques and thermodynamic tools, it was possible to understand the evolution of the mechanical properties of irradiated steel, with a particular focus on the role of chromium and the roles of irradiation temperature and irradiation dose. They were also used to extrapolate data related to fission and attempt to make predictions in fusion conditions. A set of general recommendations concerning the database used to train the neural networks were made and the usage of such a modelling technique in materials science is discussed. An attempt to optimise the performance of neural networks by suppressing some random aspects of the training is presented. Models of the elongation, yield strength and ductile-to-brittle transition temperature trained following this procedure were created and compared to classical models.
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Li, Haoqi. "STRUCTURE, PROPERTIES, AND POTENTIAL APPLICATIONS OF POLYDOPAMINE MATERIALS." Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/571324.
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Mechanical EngineeringPh.D.
Polydopamine (PDA) as a novel polymer material has attracted much attention in recent years owing to its unique universal adhesive behavior and easy fabrication through self-assembly. Its monomer form (dopamine, DA) is composed of catechol and amine, which both contribute to the adhesive properties. Since 2007, PDA has been investigated extensively by materials research communities. Application wise, most recent researches focused on utilizing PDA as a surface chemistry modifier and secondary platform. Moreover, by heat treating layer assembled PDA film in an inert or reductive environment, PDA will carbonize and transform into a conductive form, cPDA. It has been found that cPDA has a comparable property to reduced graphene oxide (rGO). The hypothesis is that cPDA also process a layered structure with interlayer distances similar to rGO. Furthermore, with amine groups presents in dopamine, cPDA is believed to be N-doped rGO after carbonization. However, even with a decade of research on this topic, the structure of PDA has not yet been fully understood. In our work, the structural evolution of PDA and cPDA with different heat treatment temperature is investigated by Raman spectroscopy and neutron diffraction, finding the nanocrystal carbon growth respective to temperature. Carbon crystallization also explained the electrical conductivity increase from our measurement. Furthermore, with catechol groups in DA, PDA is capable of forming coordination bonds with metal ions. These bonds will pin the metal ions within PDA and form a metal-PDA complex (M-PDA). In the second part of our work, the effect of doping to structure and properties was investigated by TEM and AFM. We found the thickness of the doped film is thinner than undoped film, which indicates the crosslinking mechanism of PDA is affected by the metal ion dopant. In addition, the pinned metal in M-PDA matrix tends to be reduced into its metal phase after annealing in a protective environment. These finding has also explained the properties change in the thin film and lead us to further investigation on the mechanism of the metal reduction. In TEM, metal nanoparticles are found reduced from M-PDA complex and remain attached under irradiation of electrons. The abundance of electrons in TEM directly supplies the reduction of metal cations and forms metal nanoparticles. With different metal cation, the behavior and final products are vastly different in size and shape. Heating M-PDA powder or film is also a valid way to synthesis self-supported metal nanoparticles which has potential applications in catalysis. The performance of the synthesized catalysts was tested for hydrogen generation in acid solution. This research works forms the third and fourth part of my study. The last part of this study includes the mechanical properties of pristine PDA and Cu-PDA with and without annealing. Finding that increased annealing temperature and metal ion coordination increases Young’s modulus.
Temple University--Theses
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McMahon, P. H. "The mechanical properties of cement stabilized minestone." Thesis, University of Sunderland, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378952.
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Cui, Jianyi. "Catalytic properties, densification and mechanical properties of nanocrystalline yttria-zirconia-based materials." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41679.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references.
Alumina, titania, ceria and manganese oxide were either coated onto or doped in cubic 7 mol% Y203-ZrO2 (7YZ) nanocrystals to form nanocomposites for methane combustion. These novel catalysts were very active and thermally stable. In particular, 25 wt% Mn203-coated 7YZ and 25 wt% Mn203-doped 7YZ showed remarkably low light-off temperatures of 3750C and 3580C, respectively. These catalysts were highly attractive as they were competitive with the much more expensive supported noble metal catalysts. Their catalytic activity could be attributed to the availability of active surface oxygen species, which facilitated the methane activation at low temperatures. Nanocrystalline 3 mol% and 8 mol% Y203-ZrO2 (3YZ and 8YZ) were successfully densified with an ultrafine grain size of < 90 nm by pressureless sintering at 11000C and 11500C, respectively. The low-temperature sinterability could be attributed to the well-defined nanocrystalline particles obtained via hydrothermal synthesis, and the effective elimination of secondary porosity through the dry compact processing. Submicron-sized 3 mol% Y203-ZrO2 ceramics with a grain size of - 150 nm was also obtained with commercial TOSOHC powders. Grain growth during densification of TOSOH© powders was successfully suppressed by presintering to 93% density under an argon atmosphere, followed by hot isostatic pressing at a temperature lower than the presintering temperature. The grain sizes of dense 3YZ and 8YZ ceramics were controlled between 100 nm and 5 glm. This allowed for the systematic study of 3YZ and 8YZ in indentation hardness, Young's modulus and fracture toughness as a function of grain size through micro-indentation and instrumented nano-indentation.
(cont.) The Hall-Petch effect was found to be extended to the nanocrystalline regime for 3YZ. 8YZ showed the Hall-Petch effect only in the micrometer and submicrometer regime. Maximum Hv values of 19 and 20 GPa were achieved for 3YZ and 8YZ, respectively. A continuous decrease in Young's modulus with decreasing grain size was observed in both 3YZ and 8YZ. This could be partially explained by the percolation theory. Transgranular fracture was observed in 3YZ as the grain size approached - 100 nm. This was in contrast with the dominant intergranular fracture mode observed in ceramics with fine grain sizes. Transgranular fracture was found in 8YZ over an even broader range of grain sizes (150 nm to 5.0 glm). A significant reduction in fracture toughness from 7.9 MPam-1/2 to 3.1 MPa-m1/2 was observed as the grain size was reduced from 1.1 im to 100 nm in 3YZ. Fracture toughness was much lower for 8YZ than for 3YZ, and showed little dependence on grain size. The stability of tetragonal phase at small grain sizes could account for the considerable reduction in the fracture toughness in 3YZ, and the transgranular fracture mode as grain size approached 100 nm.
by Jianyi Cui.
Ph.D.
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Eskandari, Hani. "On the identification of mechanical properties of viscoelastic materials." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/6051.
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Commonly used medical imaging techniques can render many properties of the anatomy or function, but are still limited in their ability to remotely measure tissue mechanical properties such as elasticity and viscosity. A remote and objective palpation function would help physicians in locating possible tumors or malignancies. The branch of medical imaging that characterizes tissues mechanical properties in a non-invasive manner has enjoyed increasing interest in the past two decades. The basic principle is to apply an excitation, such as tissue compression, to a region of interest and measure the resulting tissue deformation. Tissue mechanical properties can then be inferred from the observed deformation at multiple locations in the region, and the properties can be displayed as an image. If the excitation is dynamic, the deformation is considered as a motion field that varies in time and location over the region of interest. Ultrasound is particularly well suited for measuring motion fields due to its ability to image in real-time, low cost, low risk and ease-of-accessibility. The focus of this thesis is the estimation of the viscoelastic parameters such as Young's modulus, viscosity and relaxation-time. For this purpose, a motion estimation method is proposed to measure axial tissue displacements from the peak of the ultrasound radio frequency signals. The displacements can be further processed to identify the mechanical properties. Two methods were developed: the first one is based on a one dimensional Voigt's model of soft tissue and the second one is based on a finite element model. In the first method, a single frequency or wide-band excitation is applied to the tissue and the local relaxation-time is recovered from the phase difference between the strains or displacements. In this method, the elasticity can also be reconstructed from the magnitudes of the spectra. In the second approach, a novel dynamic finite element model is proposed for the incompressible soft materials. An inverse problem of viscoelasticity is solved iteratively to reconstruct the viscosity and elasticity based on a two or three dimensional model. The theoretical aspect of compressional elastography and longitudinal wave propagation is investigated. It is shown to be feasible to apply dynamic or transient compressional excitation to recover the dynamic properties of soft tissue.
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Ramzan, Muhammad. "Structural, Electronic and Mechanical Properties of Advanced Functional Materials." Doctoral thesis, Uppsala universitet, Materialteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205243.
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The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage. Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials. Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies. MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method. Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature. In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.
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Popelar, Carl Frank. "Characterization of mechanical properties for polyethylene gas pipe materials." Connect to this title online, 1989. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1094830993.
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Poisl, William Howard III. "Mechanical and viscoelastic properties of materials by instrumented indentation." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187224.
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The mechanical properties of small volumes of material have received increasing attention in the past decade due to the extensive use of films and coatings in microelectronic devices and as protection against wear and corrosion. The mechanical properties of thin films of a given material are often substantially different from those of the identical bulk material. Instrumented, or ultra-low load, indentation instruments are capable of measuring the elastic, plastic and time-dependent properties of small volumes of materials. A two stage area model has been developed to predict the variation in measured hardness with depth of penetration for soft films on hard substrates. The model is able to predict the variation for depths of penetration less than and greater than the film thickness. The model incorporates constraints on the film hardness based on the uniaxial compression of a flat cylindrical disk. Friction, or adhesion, at the film/substrate interface causes the film hardness to increase as the depth of penetration increases. However, the film hardness is not allowed to increase beyond the substrate hardness. The model is compared to experimental hardness versus depth data for three different film/substrate systems with different levels of adhesion. Time-dependent properties of materials are obtainable from instrumented indentation tests by measuring the force and displacement as a function of time. Indentation creep experiments on a linear viscoelastic material, amorphous selenium, were used to establish the relationship between indentation strain rate and the strain rate measured in conventional creep tests. Equations for determining viscosity from indentation tests were also obtained. Finally, it was shown that stress relaxation functions for viscoelastic materials may be obtainable from indentation creep experiments.
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Leppard, Claire Louise. "Mathematical modelling of some mechanical properties of construction materials." Thesis, Coventry University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313143.
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Harris, Trudy Katherine. "The mechanical properties of ultrahard materials at elevated temperatures." Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363188.
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Ngan, Alfonso Hing Wan. "Dislocation Mechanisms and Effects on Mechanical Properties of Materials." Thesis, University of Birmingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522018.
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Lamm, Adrienne Valerie. "Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565.
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Khasawneh, Qais Azzam. "On the Analysis of Mechanical Properties of Nanofiber Materials." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1226939318.
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Sher, Arnold. "Holographic determination of mechanical properties and behaviour of materials." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/21833.
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Bibliography: pages 116-122.This study, which was primarily experimental, was aimed at investigating the feasibility and development of experimental procedures using holographic interferometry to determine different material properties such as: i) Modulus of Elasticity (E) ii) Poisson's ratio (v) (which included a study into the Modulus of Rigidity. (G)) iii) creep behaviour at room temperature. The Elastic Modulus (E) was determined from the relationship E=v²p, where v is the velocity of a longitudinal wave propagating in a long rod and p is the density of the rod. The technique of double-exposure holographic interferometry was used to record longitudinal waves propagating in long brass and steel rods. The waves were initiated by striking the end of the rod with a pendulum. From the pulsed laser interferograms obtained, the distance travelled by the wave in a known time could be measured and thereby the velocity (v) could be calculated. Experimental results indicate that it is feasible fo use holographic interferometry when dynamically determining the Elastic Modulus. The values produced for brass and steel compared favourably with the ones obtained from the ultrasonic velocity technique.
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Subedi, Samikshya. "Evaluation of Microstructural and Mechanical Properties of Multilayered Materials." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/802.
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Microstructure controls many physical properties of a material such as strength, ductility, 1density, conductivity, which, in turn, determine the application of these materials. This thesis work focuses on studying microstructural features (such as grain size, shape, defects, orientation gradients) and mechanical properties (such as hardness and yield strength) of multilayered materials that have undergone different loading and/or operating conditions. Two materials that are studied in detail are 18 nm Cu-Nb nanolaminates and 3D printed Inconel 718. Copper-Niobium (Cu-Nb) nanolaminate is a highly stable, high strength, nuclear irradiation resistant composite, which is destabilized with application of high pressure torsion (HPT). This work focuses on understanding the deformation and failure behavior of Cu-Nb using a novel orientation mapping technique in transmission electron microscopy in (TEM) called Automated Crystal Orientation Mapping (ACOM) and Digistar (ASTARTM) or Precession Electron Diffraction (PED). A new theory is postulated to explain strengthening mechanisms at the nanoscale using a data analytics approach. In-situ TEM compression and tensile testing is performed to image dislocation movement with the application of strain. This experiment was performed by Dr. Lakshmi Narayan Ramasubramanian at Xi’an Jiaotong University in China. Another major aspect of this research focuses on the design, fabrication, and microstructural characterization of 3D printed Inconel 718 heat exchangers. Various heat exchanger designs, machine resolution, printing techniques such as build orientation, power, and velocity of the laser beam are explored. Microstructural and mechanical properties of printed parts (before and after heat treatment) are then analyzed to check consistency in grain size, shape, porosity, hardness in relation to build height, scan parameters, and design. Various tools have been utilized such as scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), x-ray computed microtomography (at Advanced Photon Source at Argonne National Lab), hardness and micro-pillar compression testing for this study.
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Chapagain, Indra Prasad. "Mechanical properties of self-consolidating concrete with pozzolanic materials." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/2111.
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Self-consolidating concrete has been described as the most revolutionary development in concrete technology in several decades with the ability to flow freely through closely spaced reinforcements, expel entrapped air and self compact without vibration. Since it was first developed in Japan in the early 1980's, major development in the chemical admixture technology has made SCC more viable.
An experimental study was conducted to identify the mechanical properties of SCC by optimizing the use of pozzolanic materials and local aggregates with some proposed statistical models. The research was focused to investigate compressive strength, splitting tensile strength, modulus of elasticity and drying shrinkage behavior of concrete. The results were established experimentally and compared with the available SCC research data based on extensive literature study.
Besides the improved mechanical performance, results indicate that the use of pozzolanic materials and local aggregate in SCC is recommended in terms of its cost benefit value.
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Hartschuh, Ryan D. "Optical Spectroscopy of Nanostructured Materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1195016254.
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Bidasaria, Sanjay K. "Electronic and mechanical properties of." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28101.
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Thesis (M. S.)--Physics, Georgia Institute of Technology, 2009.Committee Chair: Marchenkov, Alexei; Committee Member: Callen, William Russell; Committee Member: First, Phillip; Committee Member: Kindermann, Marcus; Committee Member: Riedo, Elisa.
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Li, Edward. "Characterization of mechanical and fatigue properties for a hybrid titanium composite laminate." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19897.
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Gerhardt, Michael R. "Microstructure and mechanical properties of bamboo in compression." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76122.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 34).
Bamboo has received much interest recently as a construction material due to its strength, rapid growth, and abundance in developing nations such as China, India, and Brazil. The main obstacle to the widespread use of bamboo as a structural material is the lack of adequate information on the mechanical properties of bamboo. In this work, the microstructure and mechanical properties of Phyllostachis dulcis bamboo are studied to help produce a model for the mechanical properties of bamboo. Specifically, a linear relationship is established between the density of bamboo samples, which is known to vary radially, and their strength in compression. Nanoindentation of vascular bundles in various positions in bamboo samples revealed that the Young's modulus and hardness of the bundles vary in the radial direction but not around the circumference. The compressive strength of bamboo samples was found to vary from 40 to 95 MPa, while nanoindentation results show the Young's modulus of vascular bundles ranges from 15 to 18 GPa and the hardness ranges from 380 to 530 MPa.
by Michael R. Gerhardt.
S.B.
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Park, Jin Young. "Pultruded composite materials under shear loading." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/32865.
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Braithwaite, Christopher Henry. "High strain rate properties of geological materials." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/267815.
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The dynamic response of various geological materials has been investigated through a series of plate impact experiments. The materials involved were supplied from various mines by De Beers and Rio Tinto and were generically termed: sandstone, scilified siltstone, kimberlite, quartz/feldspathic gneiss, biotite schist, amphibolite, amphibolitic gneiss, basalt and iron ore. Investigations into compressional, shear and tensional behaviour were carried out. This project was part of a larger international study to develop models for the explosive loading of rock in a mining environment. This model is known as the Hybrid Stress Blasting Model, or HSBM. For this model to be accurate and relevant to the mining process it is essential to have dynamic data on the various rock types concerned. This was the purpose of the current project. As the material data are destined for use in a computer modelling programme it was essential to attempt to develop prediction methodologies to avoid the need for expensive dynamic characterisation of any new materials encountered in the mining environment. Much of the static data provided with the materials from De Beers proved of little use in predicting behaviour, although crucially it was not possible to determine sufficient dynamic tensile strengths in this investigation to make comparisons with the De Beers data. More success was found in predicting the slope of the Hugoniot with the elastic impedance of the material (for the non-porous linear Hugoniot materials). A fairly strong trend was found, which was backed up with data from the literature. Additionally some effort at further analysis using mineral data was undertaken. Attempts at predicting the HEL were also partially successful. While no specific quantitative prediction method was found, it was noted that the HEL did seem to scale with grain size, in that the large grained materials had a lower value of the HEL (below 2 GPa) compared with the finer grained materials (around 4 GPa and above).
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Minnich, Austin (Austin Jerome). "Modeling the thermoelectric properties of bulk and nanocomposite thermoelectric materials." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44852.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 95-99).
Thermoelectric materials are materials which are capable of converting heat directly into electricity. They have long been used in specialized fields where high reliability is needed, such as space power generation. Recently, certain nanostructured materials have been fabricated with high thermoelectric properties than those of commercial bulk materials, leading to a renewed interest in thermoelectrics. One of these types of nanostructured materials is nanocomposites, which are materials with either nanosized grains or particles on the nanometer scale embedded in a host material. Nanocomposites present many challenges in modeling due to their random nature and unknown grain boundary scattering mechanisms. In this thesis we introduce new models for phonon and electron transport in nanocomposites. For phonon modeling we develop an analytical formula for the phonon thermal conductivity using the effective medium approximation, while for electron modeling and more detailed phonon modeling we use the Boltzmann equation to calculate the thermoelectric properties. To model nanocomposites we incorporate a grain boundary scattering relaxation time. The models allow us to better understand the transport processes in nanocomposites and help identify strategies for material selection and fabrication.
by Austin Minnich.
S.M.
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Khor, Han Chuan. "Mechanical and structural properties of interlocking assemblies." University of Western Australia. School of Civil and Resource Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0026.
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A novel way to ensure stability of mortarless structures topological interlocking is examined. In this type of interlocking the overall shape and arrangement of the building blocks are chosen in such a way that the movement of each block is prevented by its neighbours. (The methodological roots of topological interlocking can be found in two ancient structures: the arch and the dry stone wall.) The topological interlocking proper is achieved by two types of blocks: simple convex forms such as the Platonic solids (tetrahedron, cube, octahedron, dodecahedron and icosahedron) that allow plate-like assemblies and specially engineered shapes of the block surfaces that also allow assembling corners. An important example of the latter so-called Osteomorphic block is the main object of this research with some insight being provided by numerical modelling of plates assembled from tetrahedra and cubes in the interlocking position. The main structural feature of the interlocking assemblies is the need of the peripheral constraint (for the Osteomorphic blocks this requirement can be relaxed to uni-directional constraint) to keep their integrity. We studied the least visible constraint structure internal pre-stressed cables which run through pre-fabricated holes in Osteomorphic blocks. It is shown that the pre-stressed steel cables can provide the necessary constraint force without creating appreciable residual stresses in the cables, however the points of connection of the cables are the weakest points and need special treatment. The main mechanical feature of the interlocking structures is the absence of block bonding. As a result, the blocks have a certain freedom of translational and rotational movement (within the kinematic constraints of the assembly) and their contacts have reduced shear stresses which hampers fracture propagation from one block to another. These features pre-determine the specific ways the interlocking assemblies behave under mechanical and dynamic impacts. These were studied in this project and the following results are reported. As the blocks in the interlocking structure are not connected, the main issue is the bearing capacity. The study of the least favourable, central point loading in the direction normal to the structure shows elevated large-scale fracture toughness (resistance to fracture propagation). However when the central force imposes considerable bending the generated tensile membrane stresses assist fracturing of the loaded block. Prevention of bending considerably enhances the strength therefore the most efficient application of the interlocking structures would be in protective coatings and covers. Furthermore, proper selection of the material properties and the interface friction can increase the system overall strength and bearing capacity. The results of the computer simulations suggest that both Youngs modulus and the friction coefficient are the key parameters whose increase improves the bearing capacity of topologically interlocking assemblies.
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Pötzsch, Sina. "Influence of PLA on the mechanical properties of paper materials." Thesis, KTH, Hållfasthetslära (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176012.
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The aim of the project is to produce a new type of paper with PLA that later will be converted into corrugated board. The PLA paper shall have enhanced moisture resistance and shall show less creep compared with conventional paper under a humid ambient climate. Therefore, dynamic sheets with different amounts of PLA (0 %, 5% and 10 %) are manufactured. The sheets are made from unbleached softwood kraft pulp with two different grinding ratios and pulp from recovered paper. As well as examining the effect of PLA in paper, the influences of different grinding ratios and pulps are investigated. After testing of dynamic sheets, larger paper quantities of recovered paper with 0 %, 5% and 10 % PLA are produced on a pilot paper machine (FEX). Afterwards those papers are pressed and heated to melt the PLA fibres in order to activate them. The results show that PLA strongly enhanced tensile strength (up to 80 %), stiffness, ductility and compression strength in dynamic sheets of unbeaten kraft and recovered paper. In beaten kraft dynamic sheets the strength improved slightly, whereas stiffness and compression strength decreased with addition of PLA. For unbeaten kraft paper mechano-sorptive creep was reduced. For paper produced on FEX PLA increased tensile strength. Tensile stiffness and compression strength increased in cross machine direction (CD). Mechano-sorptive creep was reduced under cyclic humidity conditions in CD.