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Dissertations / Theses on the topic 'Laminated materials Mechanical properties'
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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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Johnson, David Page. "The effect of specimen size on the mechanical response of laminated composite coupons loaded in tension and flexure." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164926/.
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Zhang, Mei. "The effects of contamination on the mechanical properties of carbon fibre reinforced epoxy composite materials." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299084.
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Rhymer, Donald William. "Fatigue damage mechanisms of advanced hybrid titanium composite laminates." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18980.
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Appiah, Kwadwo Ampofo. "Microstructural and microanalytical characterization of laminated (C-SiC) matrix composites fabricated by forced-flow thermal-gradient chemical vapor infiltration (FCVI)." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14910.
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Cobb, Ted Quincy Jr. "Optimization of hybrid titanium composite laminates." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19965.
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Minnaar, Karel. "Experimental and numerical analyses of damage in laminate composites under low velocity impact loading." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15812.
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Subramanian, Suresh. "Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-01252008-165523/.
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Kuriakose, Sunil. "Analysis of damage in composite laminates under bending." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12054.
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Kousourakis, Asimenia, and asimeniak@hotmail com. "Mechanical Properties and Damage Tolerance of Aerospace Composite Materials Containing CVM Sensors." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090506.095922.
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The PhD thesis evaluates the mechanical properties and damage tolerance of aerospace carbon/epoxy laminates containing long, narrow interlaminar galleries. The term 'galleries' refers to thin and long holes in a laminate used for the installation of small measuring devices, such as structural health monitoring (SHM) sensors. The galleries considered in this study are similar to those used in a novel SHM system known as 'Comparative Vacuum Monitoring (CVM)'. CVM was developed by the Australian company - Structural Monitoring Systems (SMS) - for damage detection in aircraft structures. CVM is a SHM system that utilises pressure differentials between a parallel series of galleries at atmospheric or low pressure to detect damage initiation and propagation. Thus far, CVM has been used for the monitoring of surface cracks in metallic structures using surface mounted sensors. Recent research has also demonstrated that it may be possible to monitor damage along the bond- line of both metallic and composite joints using CVM. The ability of CVM sensors to detect delamination damage inside composite structures is less well understood. It is envisaged that CVM can be used for the through-life health monitoring of composite aircraft structures prone to delamination damage. However, a major concern with applying CVM to composite laminates is the open-hole design of the galleries that may initiate damage growth under external loading. Material property data, structural tests, and models for predicting the properties of laminates containing galleries is needed before CVM technology can be certified for use in aircraft composite structures. The primary objectives of this PhD thesis are the development of an optimum process method for introducing multiple interlaminar CVM galleries in composite laminates; the development of a validated model for calculating changes to the mechanical properties of laminates containing CVM galleries; and the determination of optimum CVM gallery shape, size and orientation combinations for minimising the effect of the galleries on the mechanical properties of laminates. The effects of the shape, size and orientation of CVM galleries on the mechanical properties of carbon/epoxy laminates are evaluated by an extensive experimental research program, and the results are presented in the thesis. The properties investigated include the in-plane tensile and compressive properties, tensile and compressive fatigue life, through-thickness tensile strength, interlaminar shear strength, mode I and mode II interlaminar fracture toughness, and impact damage resistance. The results from tensile tests on lap-joints and T-joints containing CVM galleries are also presented.
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Hammond, Matthew Wesley. "Evaluation of the Crack Initiation and Crack Growth Characteristics in Hybrid Titanium Composite Laminates via In Situ Radiography." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7650.
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Hybrid Titanium Composite Laminates (HTCL) have vast potential for future commercial aircraft development. In order for this potential to be properly utilized the HTCLs material properties must first be well understood and obtained through experimentation. Crack initiation and crack growth characteristics of HTCLs are dependent on the heat treatment of the embedded constituent titanium foil. While high strength titanium foils may delay crack initiation, there may be an adverse effect of unsuitable crack growth rates in the HTCLs. Literature has indicated that when properly designed, cracks in HTCLs can arrest due to fiber bridging mechanisms and other crack closure mechanisms. Traditional surface inspection techniques employed on facesheet laminate evaluations will not be able to properly monitor the internal crack growth and damage progression for the internal plies.
The main objective of the this joint Georgia Tech/Boeing research project was to determine and compare crack initiation and crack growth characteristics of different heat-treated -Ti 15-3 titanium foil embedded in HTCLs. Georgia Tech utilized a unique capability of x-raying the internal foils of the HTCL specimen in a servo-hydraulic test frame while under load. The titanium foil in this study represented four different heat treatments that result in four increasing levels of strength and decreasing levels of elongation. Specifically, open-hole HTCL coupons were tested at four stress load levels under constant amplitude fatigue cycles to determine a-N curves for the HTCL layups evaluated. The layup evaluated was [45/0/-45/0/Ti/0/-45/0/45]. Crack growth rates were determined once the initiated crack was detected via radiographic exposure. Radiographic delamination analysis and thermoelastic stress analysis techniques were employed to determine additional damage mechanisms in the laminate. Analytical and finite element methods were utilized to determine ply stresses. Additionally, titanium foil properties were determined via dog-bone coupons for each of the four heat treatment conditions.
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Treasurer, Paul James. "Characterization and Analysis of Damage Progression in Non-Traditional Composite Laminates With Circular Holes." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13989.
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Carbon Fiber / Epoxy Laminates are increasingly being used in the primary structure of aircraft. To make effective use these materials, it is necessary to consider the ability of a laminate to resist damage, as well as material strength and stiffness. A possible means for improving damage tolerance is the use of non-traditional composite laminates, in which the longitudinal 0 plies are replaced with 5 or 10 plies. The main objectives of this collaborative Georgia Tech / Boeing research was the characterization of these non-traditional laminates, and the determination of appropriate lamina-level analytical techniques that are capable of predicting the changes caused by the use of slightly off-axis longitudinal plies. A quasi-isotropic [45/90/-45/theta/45/90/-45/-theta]s and hard [45/theta/-45/theta/90/45]s lay-up, where theta =0,5 or 10, were tested in open hole tension, filled hole tension, open hole compression, single shear bearing, and unnotched tension. These coupon level tests illustrated the effects of lay-up, notch constraint, and load type on traditional and non-traditional laminates. Die penetrant enhanced in-situ radiography was performed to determine the extent of damage suppression. The use of non-traditional laminates was found to reduce longitudinal ply cracking and delamination, with significant effect on the stress distribution around the notch. The use of non-traditional laminates also resulted in a 15%-20% improvement in bearing strength of the traditional laminates. Several predictive techniques were implemented to evaluate their ability to predict the effect of slight changes in ply orientations. A progressive damage model was written to compare Tsai-Wu, Hashin, and Maximum Stress unnotched strength criterion. Additionally, several semi-empirical failure theories for notched strength prediction were compared with linear and bi-linear cohesive zone models to determine applicability to non-traditional laminates.
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Nilsson, Peter. "Measuring material properties of thin films with DIC and tearing test of laminate." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-14939.
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Thin polymer materials are today widely used in industry and production. An ordinary food package can have around six different layers of materials laminated together to obtain the desired protection. To obtain an efficient usage of these materials simulations are often required. But the simulations require precise and good material models and properties. To obtain these properties through standard tests are difficult as normal strain gauges or extensometers can’t be used. Much research has been done on this kind of material. But still, the knowledge of the behaviour in certain cases is limited. One such area is the tearing of a laminated material. The first objective of the work is to test a new measurement method, Digital Image Correlation (DIC), for thin polymer films and test if the method is applicable. DIC is a non-contact measurement technique that measure the deformation of a stochastic pattern. The strain is then calculated from this deformation. These strains can then be used to obtain material properties and behaviour. The second objective is to test the tearing behaviour of a laminate. The material used is a laminate between a PET (100 μm) and LDPE (25 μm) film. When testing the single layers they were carefully delaminated with a plexiglass staff. As the material can be anisotropic the materials were tested in five directions: Machine Direction (MD); 22,5˚; 45˚; 67,5˚ and Cross Direction (CD). The work and tests were performed at BTH Campus Gräsvik. An experimental setup for DIC with the usage of chalk spray and backlight was tested. Five tests were performed with and without DIC pattern. It was calculated that the DIC specimens were within standard deviation of the reference tests. GOM Correlate was used to evaluate the strains and visualise the distribution. The strains obtained were also used to calculate the true stress of the specimens and estimate the Poisson’s ratio. Through testing it was concluded that the tearing of the laminate led to delamination in one of the legs. The delamination always appears in the leg where the LDPE film will experience tensile forces. The crack also angels towards 45˚. By testing single layers it was found that the PET film angles when teared, likely caused by the anisotropy of the material. An experimental setup for the use of DIC for thin polymer has been developed. This method can be used for future measurements and improvement of material models. The behaviour of laminated tearing was observed and some conclusions could be drawn about its behaviour. However, a lot more work is required on this subject.
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Wen, Zhongmeng. "Contribution à l'étude des contraintes résiduelles sur le comportement mécanique des composites stratifiés ±θ." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0019/document.
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Cette thèse comprend deux parties : Détermination des contraintes résiduelles dans les composites stratifiés ±θ induites par le cycle thermique de fabrication et Etude de leurs influences sur le com-portement mécanique de ces stratifiés. Limitée par la théorie actuelle, la détermination expérimentale des contraintes résiduelles dans les stratifiés ±θ a été très difficile. Dans notre étude, la méthode du trou incrémental a été employée afin de relaxer les contraintes résiduelles et les déformations provoquées ont été mesurées par les jauges de déformation. Une nouvelle approche proposée dans cette thèse permet d’associer les déformations autour du trou et les contraintes résiduelles au sein du stratifié ±θ. Les coefficients de calibration ont été déterminés par la simulation numérique. Grâce à l’approche développée, nous avons constaté une relation linéaire entre les contraintes résiduelles et l’angle θ du stratifié [02/θ2]s. En adaptant un modèle thermoélastique du matériau, les résultats expérimentaux ont pu être modélisés numériquement. Ensuite, nous avons étudié l’influence de l’épaisseur du stratifié, du cycle de cuisson et du vieillissement hydrothermique sur la distribution des contraintes résiduelles. A l’aide de la technique d’émission acoustique, les influences des contraintes résiduelles sur l’endommagement et le comportement mécanique des stratifiés ont été étudiées grâce aux essais de traction. Enfin, l’importance des contraintes résiduelles sur la rupture transversale du stratifié a été mise en évidence en comparant avec les résultats théoriquesThis thesis work consists of two main parts: Deter-mination of residual stresses in composites laminates ±θ, introduced by the thermal cycle during the manufacturing process of laminates and Study of their influences on the mechanical behavior of these laminates. Limited by the current theory, the exper-imental determination of residual stresses in the laminates ±θ was very difficult. In this work, the incremental hole drilling method was performed for the residual stresses relaxation and then the gener-ated strains around the hole were measured with strain gages. The new approach proposed in this thesis allows associating the strains around the hole and the residual stresses in the laminates ±θ. The calibration coefficients were determined by the numerical simulation. With this approach, we found a linear relationship between the residual stresses and the fiber orientation angle θ for the composite laminates [02/θ2]s. By adapting a thermoelastic ma-terial model, the results obtained by our new ap-proach were modelized by the numerical study. Then we studied the influence of laminate thickness, curing cycle and hydrothermal ageing on the distri-bution of residual stresses. With the help of acoustic emission technique, the influences of the residual stresses on the damage and the mechanical behavior of composite laminates were studied through tensile tests. Finally, the importance of the residual stresses on the transverse failure of composite laminates was demonstrated comparing with the theoretical results
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Yttergren, Rose-Marie. "Mechanical properties of laminated ceramic composites /." Stockholm : Tekniska högsk, 1999. http://www.lib.kth.se/abs99/ytte0910.pdf.
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Wang, Yi. "Mechanical performance of transparent laminated materials for aircraft." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/59698.
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To fully understand mechanical and structural performance of laminated glass, seven laminated cases were designed to assess the influence of glass types, polymer interlayer thickness, polymer interlayer types and multi-layered interlayer. An innovative apparatus combining 3D-Digital-Image-Correlation and ring on ring tests have been tested successfully, major strain and out of plane displacement at the supporting side were monitored. Novel sabot design helped the rubber projectile to eject without deformation in gas gun tests. The third innovative design was the gas gun system which allowed a stereo system of two high speed cameras for 3D-Digital-Image-Correlation and one camera monitoring impact performance, strain gauge system, and detecting velocity to be synchronised at the same time. Regarding major research findings, for monolithic glasses, an approximate 0.8% major failure strain was identified regardless of its thickness which was used as a failure criterion for laminated glass. For laminated glasses, an increase of thermoplastic-polyurethane thickness will allow laminate to absorb more energy at quasi static and low velocity ranges, but lower the supporting face strain at high velocity. Chemically strengthened glass used as frontal glass layer has better performance in terms of energy consumption in quasi static and low velocity ranges comparing to thermally strengthened glass. Different types of interlayer have different functionalities. Sentry-glass-plus is more rigid comparing thermoplastic-polyurethane and polyvinyl-butyral which can transfer more shear between layers and lower the strain at the back. However, it has poor adhesion on glass proven by large peeling off of the glass fragments after gas gun experiments. Comparing with polyvinyl-butyral, thermoplastic-polyurethane has good adhesive properties with Sentry-glass-plus and glass. A multi-layered interlayer system using structural Sentry-glass-plus and adhesive thermoplastic-polyurethane as interlayers can significantly reduce the strain during impact and prevent glass fragments from flying off at high velocity which is favourable in real scenarios (e.g. bird-strike).
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Singh, Jasveer. "Multi-objective selection and optimization of shaped materials and laminated composites." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104819.
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Most of the current optimization techniques for the design of light-weight structures are unable to generate structural alternatives at the concept stage of design. This research tackles the challenge of developing methods for the early stage of design involving structures made up of conventional materials and composite laminates. For conventional materials, the recently introduced shape transformer approach is used. This work extends the method to deal with the case of torsional stiffness design, and generalizes it to single and multi-criteria selection of lightweight shafts subjected to a combination of bending, shear, and torsional load. The prominent feature of the work is the useful integration of shape and material to model and visualize multi-objective selection problems. The scheme is centered on concept selection in structural design, and hinges on measures that govern the shape properties of a cross-section regardless of its size. These measures, referred to as shape transformers, can classify shapes in a way similar to material classification. The procedure is demonstrated by considering torsional stiffness as a constraint. Performance charts are developed for both single and multi-criteria cases to let the reader visualize in a glance the whole range of cross-sectional shapes for each material. Each design chart is explained with a brief example. The above mentioned approach is also extended to incorporate orthotropic composite laminates. Design charts are obtained for the selection of five generic design variables: shape, size, material, layup, and number of plies. These charts also aid in comparing the performances of two commonly used laminates in bending and torsion - angle plies and cross plies. For a generic composite laminate, due to the number of variables involved, these kinds of design charts are very difficult. However, other tactics like using an analytical model for function evaluation can be used at conceptual stage of design. This is demonstrated with the example of a helicopter wing spar made up of composite laminates. The objective is to select the optimum shape and layup which perform best with respect to three conflicting criteria: mass, torsional-bending coupling, and location of mass center and aerodynamic center. The formulation is based on Kollar's methodology. The three-dimensional Pareto front obtained is mapped on to two dimensions for better visualization using contour representation.La plupart des méthodes d'optimisation qui existe actuellement pour la fabrication des structures légères sont incapables de générer des structures alternatives au début de la conception. Cette étude cherche à démontrer les difficultés qui existent au début de la conception et propose des solutions en se servant des matériaux conventionnels et des composites laminés.Pour des matériaux conventionnels, la nouvelle méthode de « shape transformers » a été utilisée. Dans cette étude, la méthode traditionnelle a été modifiée et inclus un modèle de rigidité pour la torsion et ainsi généralise cette méthode afin qu'on puisse l'utiliser pour la sélection (simple ou multiples) des arbres légères soumis a une combinaison des forces de flexion, de cisaillement et de torsion. L'aspect important de ce projet démontre l'intégration de la forme ainsi que le matériel sur le modèle afin qu'on puisse visualiser la sélection des problèmes a objectif multiples. Le projet se centralise sur un concept qui facilite la sélection des structures de fabrication, et dépend sur des mesures qui contrôlent les propriétés de la forme de la section quelle que soit la dimension. Cette mesure plus connu comme la méthode de « shape transformers » peut servir a classer la forme comparable au classement des matériaux. Cette méthode est démontrée en incluant la rigidité pour la torsion comme une restriction. Des tableaux qui comprennent la performance pour le cas simple ou multiples sont présentés afin qu'on puisse visualiser un rayon de section pour chaque matériel. Chaque tableau est expliqué par un bref exemple.La méthode susmentionnée à aussi été prolongé pour inclure des composites laminés orthotropes. Des tableaux de conception à été conçu afin de pouvoir sélectionner parmi les cinq paramètres : la forme, la dimension, le matériel, le « layup » et le nombre de nappes. Ces tableaux peut aussi servir à comparer la performance de deux laminés commun en flexion ou en torsion notamment le « angle-plies » et le « cross-plies ». Pour des composites laminés génériques, il est difficile de concevoir ce genre de tableau à cause des nombres de paramètres qui existent. Mais il existe d'autres méthodes analytiques qu'on peut utiliser au début de la conception. Ceci est démontré par l'exemple d'un longeron d'aile pour un hélicoptère fait avec des composites laminés. Le but est de pouvoir sélectionner la forme et le « layup » optimale avec la performance maximale à l'égard de trois critères contradictoires notamment : la masse, l'accouplement des forces de flexion et de torsion, l'emplacement de la masse et l'emplacement du centre aérodynamique. La formulation est basée sur la méthode de Kollar. Le front Pareto en trois dimensions est ainsi projeté sur deux dimensions pour une visualisation plus facile en se servant d'une représentation contour.
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Derstine, Mark S. "Combined mechanical loading of composite tubes." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43841.
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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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Daniewicz, David Joseph 1965. "Edge delamination in advanced laminated composites, theory and verification." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277294.
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A damage evolution theory capable of predicting the effects of edge delamination phenomena on composite laminate response is developed. The theory is a mechanics-based formulation which quantifies the damage development of a laminate under general loading, and incorporates it directly to the constitutive behavior of the laminate. The theoretical development introduces a laminate-specific constant φ; the methodology of φ selection is presented for [±15/±50]s, [±45/0/90]s, and [0₂/90₂]s T300 graphite/epoxy laminates. Edge effects are demonstrated by comparing the damage state of the above laminates with and without edge delamination damage. The capability of the theory in predicting the volume scaling effect is shown through consideration of the failure strengths of the [±25/90n]s laminate series.
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Sung, Taehyun. "Variable frequency microwave curing of polymer dielectrics on metallized organic substrates." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180423/unrestricted/sung%5ftaehyun%5f200312%5fms.pdf.
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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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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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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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Johnson, Wayne Michael. "Structural acoustic optimization of a composite cylindrical shell." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131213/unrestricted/johnson%5Fwayne%5Fm%5F200405%5Fphd.pdf.
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Subba, Rao Vinay Sagar. "Evaluation of mechanical properties of laminated composites using Multi-Continuum Theory in ABAQUS." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3748.
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A thorough knowledge of the mechanical properties of composites is very important for proper design and optimization of structures in composite applications. Experimental determination of these properties like strength and modulus is prohibitively expensive, as there are unlimited combinations of matrix type, fiber type and stacking sequences possible. In this thesis, “Progressive Damage Modeling” is used to simulate the notched and un-notched tension and compression tests to obtain the strength and stiffness properties of composites. A quasi-isotropic layup (25/50/25) of Toray T700GC-12K-31E/#2510 unidirectional tape was used for the purposes of simulation. Previously obtained experimental data is used to validate the model. The commercially available software ABAQUS, is used for the simulations. A commercially available plug-in for ABAQUS, Helius:MCT, which utilizes the concepts of Multi-Continuum Theory (MCT), was employed to determine its suitability to accurately predict the loads and stiffnesses. Also, the suitability of Helius:MCT for certification, by analysis, of various laminates under various types of loading, was evaluated. It is shown that progressive damage modeling, of the notched and un-notched tension and compressive tests, using Helius:MCT, results in accurate prediction of failure loads and stiffnesses of laminates.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Swain, Robert Edward. "The effect of interlayers on the mechanical response of composite laminates subjected to in-plane loading conditions." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53187.
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"lnterlayering" - the incorporation of low-modulus film adhesive between the plies of composite Iaminates - has proved to be a successful technique for reducing debilitating out-of-pIane stresses. This work seeks to determine the effect interlayering has on a composite Iaminate's in-plane performance.
Two Iaminate systems, an unnotched, 16-ply, quasi-isotropic, AS4/C985 and a centernotched, 32-ply, quasi-isotropic, AS4/C1808, were furnished in an interlayered and baseline (non-interlayered) configuration. The interlayers, 0.0005 in. each in thickness, appeared between each ply in every Iaminate tested. Both configurations of these two material systems were subjected to a regimen of in-plane loading tests. These tests included monotonic tension and compression, fully-reversed (R=-1), tension-compression fatigue cycling, and long-term tensile loading. A new test method, called the Incremental Strain Test (IST), was developed in an attempt to isolate and distinguish the long-term, tensile response of the interlayered and baseline Iaminates. This technique and its utility are described herein.
The interlayered Iaminates exhibited superior performance during monotonic and IST loading. Distinctly higher ultimate loads and strains were achieved by the interlayered laminates. The notched fatigue performance of the interlayered Iaminates was sub-standard in comparison to the baseline results at the load level tested. The residual tensile strength of the fatigued interlayered Iaminates fell sharply at an early fraction of the laminates’ total life. The presence of the interlayers did not degrade the laminates’ IST performance.
Several non-destructive techniques were used to monitor the damage mechanisms. These results, when combined with the experimental findings, helped explicate the disparity found between the interlayered and baseline Iaminate response.Master of Science
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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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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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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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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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Graux, Alexis. "Evolutions microstructurales au cours du laminage à chaud d’aciers bas carbone microalliés." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI120.
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Il existe actuellement une dynamique de développement d’aciers à très haute résistance, destinés à l’industrie automobile, et présentant des propriétés de formabilité améliorées. Ces travaux font partie d'un projet de recherche qui vise à produire des aciers à phase complexe (CP) par laminage à chaud, en recherchant une combinaison améliorée de résistance et d’aptitude à l’étirement des bordures. Ainsi, ces travaux ont porté sur la description et la compréhension des évolutions de la microstructure au cours des différentes étapes du laminage à chaud d’aciers microalliés à faible teneur en carbone. Dans un premier temps, l’évolution de l’état de précipitation et de la taille des grains austénitiques au cours du réchauffage des brames ont été étudiés. Un modèle de précipitation a été développé et couplé à un modèle de croissance de grain simple basé sur l'épinglage Zener pour décrire les évolutions de la microstructure qui se produisent pendant le réchauffage. Ensuite, les évolutions microstructurales prenant places après la déformation à chaud lors du laminage ont été analysées. Les cinétiques de recristallisation de l'austénite et de la précipitation induite par déformation ont été étudiées par des essais de relaxation de contraintes couplées à observations directes de la microstructure. Des modèles ont également été développés pour décrire ces évolutions microstructurales. Un dernier chapitre a été consacré à l'établissement des relations entre les paramètres de laminage à chaud, les microstructures et les propriétés mécaniques obtenues. Les transformations de phase au cours de refroidissements continus ont été établis, en prenant en compte l’effet de la déformation de l’austénite. Ensuite, six procédés différents de laminage à chaud différents ont été appliqués et les microstructures et propriétés mécaniques résultantes ont été caractérisées de manière détaillée. Ce travail de thèse a permis de mieux comprendre les évolutions de la microstructure se produisant lors du laminage à chaud, ainsi que les microstructures et les propriétés mécaniques qui en résultent. Les travaux de modélisation présentés pourraient s’étendre à l’étude d’autres alliages. Plusieurs stratégies visant à améliorer la combinaison de résistance et d’aptitude à l’étirement des bordures ont été proposéesThere are nowadays major driving forces for the development of Advanced High Strength steels presenting enhanced formability properties for automotive applications. This PhD-work is part of a research project that aims at producing complex phase (CP) steels by hot rolling, seeking for an enhanced combination of strength and stretch flangeability. Thus, this PhD-work focused on the description and the understanding of the microstructural evolutions during the various steps of the hot rolling process of low carbon microalloyed steels. First, the evolution of the precipitation state and austenite grain sizes during the reheating stage of hot rolling were studied. A precipitation model was developed and coupled to a simple grain growth model based on Zener pinning to describe microstructural evolutions that occurs during reheating. Then, the microstructural evolutions occurring after the hot rolling deformation passes were analyzed. The kinetics of austenite recrystallization and strain-induced precipitation were determined by stress relaxation and direct microstructural observations. Models were also developed for describing these microstructural evolutions. A final chapter focused on establishing the relationships between the hot rolling parameters, the microstructures, and the mechanical properties obtained. The phase transformation during continuous cooling was established, including the effect of austenite deformation. Then, six different hot rolling processes were applied, and the resulting microstructures and mechanical properties were extensively characterized. This PhD-work provided a better understanding of the microstructural evolutions taking place during hot rolling and of the resulting microstructures and mechanical properties. The modeling work presented could extended to the study of other alloys. Several strategies for improving the combination of strength and stretch flangeability were proposed
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Adhikari, Kamal. "Effects of functionalized single walled carbon nanotubes on the processing and mechanical properties of laminated composites." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99617.
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Carbon Nanotubes are thought to have tremendous potential as reinforcements for the next generation of composite materials. In the past decade, the enhancing effects of the nanotubes on the mechanical, electrical as well as multi-functional properties of polymer composites have been reported. However, the same nanotubes/polymer composites investigated by different research groups, in many cases, do not show a good agreement with one another. The root cause of this variability is believed to lie in the processing methodology employed to prepare the composites. Before one can propose an ideal and systematic processing condition, it is imperative to have a fundamental understanding of the effect of these nanotubes on the processing of the nanotube-based composites. In this study, the effect of 0.2wt.% functionalized single walled carbon nanotubes on the various thermo mechanical and thermo chemical properties of aerospace grade epoxy was investigated. Namely, the thermal degradation, rheological behavior, cure kinetics as well as the thermal expansion behavior of the epoxy were addressed. In addition, the effect of the application small quantity of nanotube/epoxy composite film on the interlaminar shear strength (ILSS) of a conventional laminated carbon fibre/epoxy prepregs was also investigated. The characterization results show that the presence of the nanotubes has a very significant effect on some of the inherent physical and chemical properties of the epoxy. The presence of these nanotubes leads to a delay in the degradation temperature of the epoxy. The viscosity sees a seven-fold increase at room temperature and the resin also gels at a lower temperature in the presence of the nanotubes. At the same time, the total heat of reaction is also lowered on addition of the nanotubes. The mechanical test, however, shows that the addition of the nanotube/epoxy film does not affect the ILSS of the laminated carbon fibre/epoxy composite. This ILSS value is also found to be dependant on the controlled alignment of the nanotubes and the method of application of the film at the interfaces of the laminates. Finally, it was observed that the nanotubes, when used in such low contents, also had no effect on the thermo mechanical properties of the epoxy.Les nanotubes de carbone sont considérés comme ayant un potentielénorme pour assurer le rôle de renforts dans la prochaine génération de matériauxcomposites. Dans les décennies précédentes, les effets des nanotubes surl'amélioration des propriétés mécaniques, électriques et multi-fonctionnelles despolymères ont été révélés. Par contre, dans la plupart des cas, les études réaliséespar différents groupes de recherche et portant sur les mêmes composites faits depolymère renforcé de nanotubes ne présentent pas toutes des résultatscomparables. La cause majeure de cette variabilité est la méthodologie utiliséelors du procédé de fabrication de ces composites. Avant que quiconque ne suggèreune méthodologie idéale et systématique, il est impératif de comprendre les basesfondamentales de l'effet des nanotubes sur le procédé de fabrication. Dans cetterecherche, les effets des nanotubes de carbone à paroi simple sur les propriétésthermo mécaniques et thermo chimiques d'une résine époxy de gradeaéronautique ont été investigués. Les caractéristiques étudiées comprennent ladégradation thermique, le comportement rhéologique, la cinétique depolymérisation, ainsi que l'expansion thermique. L'effet de l'application d'unfilm de nanotube/époxy sur la résistance interlaminaire au cisaillement aégalement été étudié avec un préimprégné conventionel de fibre de carbone etd'époxy. Les résultats de caractérisation montrent que les nanotubes ont un effetsignificatif sur certaines propriétés physiques et chimiques inhérentes à l'époxy.La présence des nanotubes crée un délai dans la température de dégradation del'époxy. La viscosité de la résine est 7 fois plus élevée à la température de la pièceet sa température de gélification est inférieure. De plus, la chaleur totale deréaction est diminuée. Par contre, les tests mécaniques montrent que l'applicationd'un film de nanotube/époxy ne cause pas de changement dans la résistanceinterlaminaire au cisaillement d'un préimprégné de fibre de carbone et d'époxy.Par ailleurs, cette valeur de résistance est dépendante de l'alignement desnanotubes et de la méthode d'application du film sur les interfaces du laminé.Finalement, il a été observé que les nanotubes n'ont aucun effet sur les propriétésthermo mécaniques.
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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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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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Johansson, Anton. "Influence of the adhesive on the mechanical properties in laminated multi-layer paperboard : Evaluation of two common dispersion adhesives, their failure modes, internal strength and influence on bending and tensile properties." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-33662.
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The objectives of the thesis were to investigate the adhesives influence on the mechanical properties in laminated multi-layer paperboard. The study also strived to find a method to investigate the interface strength of the adhesive layer. This was investigated by constructing handsheets of laminated paperboard by gluing a bulky, CTMP center ply, Chromofoil, of two different grammages, 290 g/m2 and 360 g/m2, together with two outer plies of ordinary copy paper, Multi- Copy 80 g/m2. The sheets were glued with two types of dispersion adhesives, a starch based adhesive and a polyvinyl acetate based adhesive. Twelve types of test specimens were constructed and tested in a series of mechanical tests, which involved a tensile test, a two-point bending test and a Scott Bond test. The method called “digital image correlation” was used trying to investigate the interface strength of the adhesive layer. The study also involved an evaluation of the possibility to predict the bending stiffness of laminated multi-layer paperboard by using calculations according to classic laminate theory. The results show that it is fully possible to use these calculated values as a prediction, with low risk of overestimating the bending stiffness of the paperboard and without involving the adhesive layer in the calculation. The method provided high absolute values in bending and tensile properties, which increased with increasing amount of glue applied. This came at the cost of grammage, which lead to low index values. The overall conclusion is that the effect from the adhesives is somewhat negative, since the mechanical properties would have been improved if the adhesive had been replaced with more fiber. The major source of errors during the experiments was the roughness of the manufacturing method. This lead to an uncertainty about whether the right amount of adhesive had been applied to the test specimens. Due to this the validity of the results could be questioned. Digital image correlation proved to be a rather sensitive method that requires a high accuracy setup and execution for it to be applicable in this type of study. The failure mode of the glue seam correlated well to the amount of glue applied. A lower amount of adhesive applied increases the likeliness of failure of the glue seam.