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1
Russell, Benjamin Peter. "The micromechanics of composite lattice materials." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252176.
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Tang, Tian. "Variational Asymptotic Micromechanics Modeling of Composite Materials." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/72.
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The issue of accurately determining the effective properties of composite materials has received the attention of numerous researchers in the last few decades and continues to be in the forefront of material research. Micromechanics models have been proven to be very useful tools for design and analysis of composite materials. In the present work, a versatile micromechanics modeling framework, namely, the Variational Asymptotic Method for Unit Cell Homogenization (VAMUCH), has been invented and various micromechancis models have been constructed in light of this novel framework. Considering the periodicity as a small parameter, we can formulate the variational statements of the unit cell through an asymptotic expansion of the energy functional. It is shown that the governing differential equations and periodic boundary conditions of mathematical homogenization theories (MHT) can be reproduced from this variational statement. Finally, we employed the finite element method to solve the numerical solution of the constrained minimization problem. If the local fields within the unit cell are of interest, the proposed models can also accurately recover those fields based on the global behavior. In comparison to other existing models, the advantages of VAMUCH are: (1) it invokes only two essential assumptions within the concept of micromechanics for heterogeneous material with identifiable unit cells; (2) it has an inherent variational nature and its numerical implementation is shown to be straightforward; (3) it calculates the different material properties in different directions simultaneously, which is more efficient than those approaches requiring multiple runs under different loading conditions; and (4) it calculates the effective properties and the local fields directly with the same accuracy as the fluctuation functions. No postprocessing calculations such as stress averaging and strain averaging are needed.
The present theory is implemented in the computer program VAMUCH, a versatile engineering code for the homogenization of heterogeneous materials. This new micromechanics modeling approach has been successfully applied to predict the effective properties of composite materials including elastic properties, coefficients of thermal expansion, and specific heat and the effective properties of piezoelectric and electro-magneto-elastic composites. This approach has also been extended to the prediction of the nonlinear response of multiphase composites. Numerous examples have been utilized to clearly demonstrate its application and accuracy as a general-purpose micromechanical analysis tool.
3
Li, Hong. "Experimental micromechanics of composite buckling strength." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11719.
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Case, Scott Wayne. "Micromechanics of strength-related phenomena in composite materials." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09122009-040447/.
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Carman, Greg P. "Micromechanics of finite length fibers in composite materials." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39869.
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Sacks, Serena. "Effects of thermal aging on the mechanical behavior of K3B matrix material and its relationship to composite behavior." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18865.
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Abdelal, Gasser F. "A three-phase constitutive model for macrobrittle fatigue damage of composites." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1485.
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Thesis (Ph. D.)--West Virginia University, 2000.<br>Title from document title page. Document formatted into pages; contains xiii, 183 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 180-183).
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Shabrov, Maxim N. "Micromechanical modeling of void nucleation in two phase materials /." View online version; access limited to Brown University users, 2005. http://wwwlib.umi.com/dissertations/fullcit/3174672.
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Fu, Yuhong. "Rapid solution of large-scale three-dimensional micromechanics problems /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Caliskan, Ari Garo. "Micromechanics-based approach to predict strength and stiffness of composite materials." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09052009-041025/.
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Fraser, Andrew. "Mesoscale behavior of an aluminum-manganese dioxide-epoxy mixture under shock loading: from milli to nano-sized aluminum particles." [Milwaukee, Wis.] : e-Publications@Marquette, 2009. http://epublications.marquette.edu/theses_open/7.
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Struble, John D. "Micro-scale planar and two-dimensional modeling of two phase composites with imperfect bonding between matrix and inclusion." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17345.
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Averill, Ronald C. "Nonlinear analysis of laminated composite shells using a micromechanics-based progressive damage model." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134259/.
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Kilic, Mustafa Hakan. "Three-dimensional micromechanical models for the nonlinear analysis of pultruded composite structures." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20735.
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Varadarajan, Bhadri Narayanan. "MICROMECHANICS OF DEBOND GROWTH AND INTERFACIAL WEAR UNDER FATIGUE LOADING IN A TRANSPARENT CERAMIC COMPOSITE." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin975352464.
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Muliana, Anastasia Hanifah. "Integrated Micromechanical-Structural Framework for the Nonlinear Viscoelastic Behavior of Laminated and Pultruded Composite Materials and Structures." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5142.
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This study introduces a new three-dimensional (3D) multi-scale constitutive framework for the nonlinear viscoelastic analysis of laminated and pultruded composites. Two previously developed nonlinear micromechanical models for unidirectional and in-plane random composite layers are modified to include time-dependent and nonlinear behavior. A new recursive-iterative numerical integration method is introduced for the Schapery nonlinear viscoelastic model and is used to model the isotropic matrix subcells in the two micromodels. In addition, a sublaminate model is used to provide for a through-thickness 3D nonlinear equivalent continuum of a layered medium. The fiber medium is considered as transversely isotropic and linear elastic. Incremental micromechanical formulations of the above three micromodels are geared towards the time integration scheme in the matrix phase. New iterative numerical algorithms with predictor-corrector type steps are derived and implemented for each micromodel to satisfy both the constitutive and homogenization equations. Experimental creep tests are performed for off-axis pultruded specimens in order to calibrate and examine the predictions of the constitutive framework for the multi-axial nonlinear viscoelastic response. Experimental creep data, available in the literature, is also used to validate the micromodel formulation for laminated composite materials. Nonlinear viscoelastic effects at the matrix level, such as aging, temperature, and moisture effects can be easily incorporated in the constitutive framework. The multi-scale constitutive framework is implemented in a displacement-based finite element (FE) code for the analysis of laminated and pultruded structures. Several examples are presented to demonstrate the coupled multi-scale material and structural analysis.
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Guerrero, Garcia José Manuel. "Micromechanical modelling of hybrid unidirectional composite materials under fibre tensile loading." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/669043.
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In this thesis, a micromechanical model for predicting the tensile failure process in hybrid and non-hybrid unidirectional composite materials under fibre tensile loading is developed. Derived from this, the influence that different parameters have on the failure development in hybrid composites is investigated. The results prove that the model captures qualitatively well the failure development of composite materials. Moreover, adding matrix yielding and dynamic effects into the model allows to improve the modelling predictions compared with experimental results. It is also proved that the size of the material has a significant influence on the hybrid properties, and the dispersion of the fibres in the hybrid material has a large importance on the failure and damage development. Therefore, this thesis gives a step forward towards the inclusion of hybrid composites into commercial design and the generation of more optimised materials<br>En aquesta tesi, es desenvolupa un model micromecànic per predir el procés de ruptura a tracció de materials compostos unidireccionals híbrids i no híbrids sotmesos a càrregues longitudinals. Derivat d’això, la influència que diferents paràmetres tenen, en el procés de ruptura de materials híbrids, és investigada. Els resultats demostren que el model captura qualitativament el procés de trencament en materials compostos. A més, afegir plasticitat a la matriu i efectes dinàmics en el model permet millorar les prediccions del model comparat amb resultats experimentals. També es demostra que la mida del material té una influència significativa en les propietats híbrides, i que la dispersió de les fibres en el material híbrid té una gran importància en el trencament i el desenvolupament de dany. Per tant, aquesta tesi dóna un pas endavant cap a la inclusió de compostos híbrids en el disseny comercial i la generació de materials més optimitzats
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Rahman, Muhammad Ziaur. "Mechanical Performance of Natural / Natural Fiber Reinforced Hybrid Composite Materials Using Finite Element Method Based Micromechanics and Experiments." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6482.
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A micromechanical analysis of the representative volume element (RVE) of a unidirectional flax/jute fiber reinforced epoxy composite is performed using finite element analysis (FEA). To do so, first effective mechanical properties of flax fiber and jute fiber are evaluated numerically and then used in evaluating the effective properties of ax/jute/epoxy hybrid composite. Mechanics of Structure Genome (MSG), a new homogenization tool developed in Purdue University, is used to calculate the homogenized effective properties. Numerical results are compared with analytical solution based on rule of mixture, Halpin-Tsai as well as Tsai-Hahn equations. The effect of the volume fraction of the two different fibers is studied. Mechanical performance of hybrid composite is compared with the mechanical performance of single fiber composites. Synergistic effect due to hybridization is studied using analytical method given in literature, finite element method based MSG and Classical Lamination Theory (CLT). It is found that, when Poisson ratio is taken into consideration, elastic modulus shows synergy due to hybridization. Finally, impact properties of ax/jute/epoxy hybrid composite material are studied using Charpy impact testing.
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Elouaer, Abdelmonem. "Contribution à la compréhension et à la modélisation du comportement mécanique de matériaux composites à renfort en fibres végétales." Thesis, Reims, 2011. http://www.theses.fr/2011REIMS003/document.
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L’industrie des matériaux composites ne cesse d’évoluer et de croître en mettant en place de nouveaux matériaux et de nouvelles technologies. En substitution des matériaux d’origine fossile que les matériaux d’origine naturelles (et surtout végétales) commencent à voir le jour. C’est dans ce contexte que notre travail de recherche est proposé. Il s’intéresse à la caractérisation du comportement mécanique d’un composite à matrice Polypropylène, renforcé avec des fibres de Chanvre et du bois de Chanvre (Chènevotte). Les différents moyens et techniques de caractérisation, utilisés par la présente étude, ont montré que ces nouveaux matériaux sont dotés de propriétés, en particulier mécaniques, de haut niveau, qui viennent rivaliser avec celles des autres composites classiques à base de fibres de verre et de carbone.Les essais expérimentaux en statique et de fatigue, ont révélé beaucoup de détails en comparaison avec d’autres matériaux composites. Ces informations ont permis de créer une sorte de base de données qui pourra servir de référence pour d’autres composites de la même famille à base de fibres végétales. Ainsi, des mécanismes d’endommagement ont été mis en évidence grâce aux essais mécaniques (traction monotone, charge-décharge, …) associés à des observations microscopiques (Microscope Electronique à Balayage), et à des outils de détection du dommage basés sur l’émission acoustique. Par le biais de cette technique, nous avons pu apprécier la qualité et l’importance de l’interface fibre/matrice qui est un paramètre fondamental pour la présente étude et pour la détermination de la loi de comportement du composite.La modélisation micromécanique a été intégrée dans ce travail de thèse, grâce au modèle de Mori-Tanaka. Le comportement des matériaux à l’endommagement n’a pas été pris en considération ; seule l’élasticité a été étudiée. A l’aide de ce modèle, nous avons pu remonter aux propriétés intrinsèques des constituants (le module d’élasticité longitudinale des renforts: Chanvre et Chènevotte)<br>The composites industry continues to evolve and grow by developing new materials and new technologies. Replacing fossil materials by materials with natural origin (especially vegetable) seems to be one of the most promising. In this context our research is proposed. It is interested to characterize the mechanical behavior of a polypropylene matrix composite reinforced with fibers of Hemp and Wood of Hemp (Chenevotte). The various means and characterization techniques used in this study showed that these new materials have interesting mechanical properties, coming rival those of other conventional composites based on carbon and glass fibers.The experimental static and fatigue tests have revealed many details in comparison with other composite materials. The information help creates a database that can serve as reference for other composites of the same family and vegetable fibers. Mechanisms of damage have been highlighted through mechanical tests (tensile monotonous charge-discharge …) associated with microscopic observations (Scanning Electron Microscope), and tools for damage detection based on emission acoustics. Thanks to this technique, we could improve the quality of the interface fiber / matrix which is a basic parameter for this study and for determining the behavior of composite.Micromechanical modeling has been integrated in this thesis, through the Mori-Tanaka model. The behavior of materials during damage has not been taken into account: only the elasticity has been studied. Using this model, we were able to trace the intrinsic properties of the constituents (the longitudinal modulus of elasticity of the reinforcements: Hemp and Chenevotte)
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Neagu, Razvan Cristian. "Hygroelastic behaviour of wood-fibre based materials on the composite, fibre and ultrastructural level." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4098.
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Wood fibres can be used as reinforcement in plastics for load carrying purposes. Some advantages compared with conventional man-made fibres are that wood fibres come from a renewable resource, have high specific stiffness and strength, are generally less hazardous to health, biodegradable, and can be manufactured at low cost and high volumes. A clear disadvantage with cellulose-based materials for structural use is their dimensional instability in humid environments. The hygroelastic properties are of high importance in materials development of improved wood-fibre composites. This work deals with the stiffness and hygroexpansion of wood fibres for composite materials. The long-term aim is to design engineered wood fibre composites based on better basic knowledge of wood fibres. Mechanistic models have been used to link the fibrous microstructure with macroscopic composite engineering properties. The properties have been characterized experimentally for various wood-fibre composites and their fibre-mat preforms, by means of curvature measurements at various levels of relative humidity, as well as tensile and compressive tests. From these test results and microstructural characterization, the longitudinal Young’s modulus and transverse coefficient of hygroexpansion of wood fibres were identified by inverse modelling. Some effects of various pulp processes and fibre modifications on the elastic properties of the fibre were observed, illustrating how the mixed experimental-modelling approaches can be used in more efficient materials screening and selection. An improved micromechanical analysis for wood-fibre composites has been presented. The model is more appropriate to combine with laminate analogy, to link fibre properties on the microscale to the macroscopic composite properties and vice versa. It also offers the possibility to include the effects of ultrastructure since it can account for an arbitrary number of phases. An approach to model ultrastructure-fibre property relations has been demonstrated. It includes analytical modelling of multilayered cylindrical fibres as well as finite element modelling of fibres with irregular geometry characterized with microscopy. Both approaches are useful and could be combined with experiments to reveal insights that can pave way for a firmer link between the wood fibre ultrastructure and wood fibre properties.<br>QC 20100914
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Cavalcante, Márcio André Araújo. "Modelagem do comportamento termo-mecânico transiente de estruturas de materiais compósitos pela teoria de volumes finitos." Universidade Federal de Alagoas, 2006. http://repositorio.ufal.br/handle/riufal/378.
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The advance of the materials science has motivated the advent of composite materials
with different characteristics that assure high performance thermo-mechanical, such as the
advanced fiber reinforced composites and those that present a gradual variation in its
microstructure. Nowadays, many computational models and analytical methods are being
employed for evaluation of the behavior of such materials. An alternative technique, applied to
the steady-state thermo-mechanical analysis, which considers the coupling between
microstructure and macrostructure behaviors, is that originally denominated of Higher-Order
Theory. In this work is used the same theoretical base of the Higher-Order Theory, with a
simplification in the discretization and assembly of the system of equations. In this way, this
theory presents some similarities in relation to the finite-volume technique used in fluid
dynamics problems, reason for which is enough reasonable to adopt the denomination finitevolume
theory for this method. Besides, as a contribution of this study, it is presented a
parametric formulation that allows a larger flexibility in the mesh generation and a reduction of
the problem in relation to the number of variables, particularly appropriate for analysis of
structures with curved contour. The formulation was also extended for the accomplishment of
transient thermo-mechanical analysis. In the present study, a three-dimensional formulation of
the method is also used for the determination of the effective properties of fiber reinforced
composites and particulate materials, where comparisons were accomplished with
micromechanics simplified models and with those based on the mean field theory (selfconsistent,
Mori-Tanaka and differential scheme). Besides, there is a series of numerical
applications in bi-dimensional thermo-elastic and elastic problems, where are accomplished
verifications using analytical solutions and comparisons with the finite element method.<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>O avanço da ciência de materiais tem proporcionado o advento de materiais compósitos
com características peculiares que asseguram elevado desempenho termo-mecânico, tais como os
compósitos avançados reforçados por fibras e aqueles dotados de microestrutura com variação
gradual. Atualmente, muitos modelos computacionais, assim como métodos analíticos, vêm
sendo empregados para avaliação do comportamento de tais materiais. Uma técnica alternativa,
voltada à análise termo-mecânica em regime estacionário, na qual o comportamento do material
é analisado considerando-se o acoplamento entre microestrutura e macroestrutura, é aquela
originalmente denominada de Higher-Order Theory. Neste trabalho, utiliza-se a mesma base
teórica da Higher-Order Theory, com uma simplificação em termos de discretização e montagem
do sistema de equações. Neste sentido, esta teoria apresenta algumas semelhanças em relação à
técnica de volumes finitos usada em problemas de dinâmica dos fluidos, razão pela qual é
bastante razoável adotar a denominação teoria de volumes finitos para o método. Além disso,
como uma contribuição deste estudo, apresenta-se uma formulação paramétrica que permite uma
maior flexibilidade na geração da malha e uma diminuição do problema em relação ao número
de incógnitas, particularmente apropriada para análise de estruturas com contorno curvo. A
formulação também foi ampliada para possibilitar a execução de análises termo-mecânicas
transientes. No presente estudo, também é utilizada uma formulação tridimensional do método
para a determinação das propriedades efetivas de materiais compósitos reforçados por fibras e
particulados, onde foram realizadas comparações com modelos simplificados da micromecânica
e com aqueles baseados na teoria de campos médios (Auto-consistente, Mori-Tanaka e Esquema
Diferencial). Além disso, há uma série de aplicações numéricas em problemas termo-elásticos e
elásticos bidimensionais, onde são realizadas verificações a partir de soluções analíticas e
comparações com o método dos elementos finitos.
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Koutsawa-Tchalla, Adjovi Abueno Kanika C.-M. "Contribution à la modélisation multi-échelle des matériaux composites." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0119.
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Nous proposons dans cette thèse diverses approches, pour l'amélioration de la modélisation et la simulation multi-échelle du comportement des matériaux composites. La modélisation précise et fiable de la réponse mécanique des matériaux composite demeure un défi majeur. L'objectif de ce travail est de développer des méthodologies simplifiées et basées sur des techniques d'homogénéisation existantes (numériques et analytiques) pour une prédiction efficiente du comportement non-linéaire de ces matériaux. Dans un premier temps un choix à été porté sur les techniques d'homogénéisation par champs moyens pour étudier le comportement élastoplastique et les phénomènes d'endommagement ductile dans les composites. Bien que restrictives, ces techniques demeurent les meilleures en termes de coût de calcul et d'efficacité. Deux méthodes ont été investiguées à cet effet: le Schéma Incrémental Micromécanique (SIM) en modélisation mono-site et le modèle Mori-Tanaka en modélisation multi-site (MTMS). Dans le cas d'étude du comportement élastoplastique, nous avons d'une part montré et validé par la méthode des éléments finis que la technique d'homogénéisation SIM donne un résultat plus précis de la modélisation des composites à fraction volumique élevée que celle de Mori-Tanaka, fréquemment utilisée dans la littérature. D'autre part nous avons étendu le modèle de Mori-Tanaka (M-T) généralement formulé en mono-site à la formulation en multi-site pour l'étude du comportement élastoplastique des composites à microstructure ordonnée. Cette approche montre que la formulation en multi-site produit des résultats concordants avec les solutions éléments finis et expérimentales. Dans la suite de nos travaux, le modèle d'endommagement ductile de Lemaître-Chaboche a été intégré à la modélisation du comportement élastoplastique dans les composites dans une modélisation multi-échelle basée sur le SIM. Cette dernière étude révèle la capacité du modèle SIM à capter les effets d'endommagement dans le matériau. Cependant, la question relative à la perte d'ellipticité n'a pas été abordée. Pour finir nous développons un outil d'homogénéisation numérique basé sur la méthode d'éléments finis multi-échelles (EF2) en 2D et 3D que nous introduisons dans le logiciel conventionnel ABAQUS via sa subroutine UMAT. Cette méthode (EF2) offre de nombreux avantages tels que la prise en compte de la non-linéarité du comportement et de l'évolution de la microstructure soumise à des conditions de chargement complexes. Les cas linéaires et non-linéaires ont été étudiés. L'avantage de cette démarche originale est la possibilité d'utilisation de toutes les ressources fournies par ce logiciel (un panel d'outils d'analyse ainsi qu'une librairie composée de divers comportements mécaniques, thermomécaniques ou électriques etc.) pour l'étude de problèmes multi-physiques. Ce travail a été validé dans le cas linéaire sur un exemple simple de poutre en flexion et comparé à la méthode multi-échelle ANM (Nezamabadi et al. (2009)). Un travail approfondi sera nécessaire ultérieurement avec des applications sur des problèmes non-linaires mettant en évidence la valeur de l'outil ainsi développé<br>We propose in this thesis several approaches for improving the multiscale modeling and simulation of composites’ behavior. Accurate and reliable modeling of the mechanical response of composite materials remains a major challenge. The objective of this work is to develop simplified methodologies based on existing homogenization techniques (numerical and analytical) for efficient prediction of nonlinear behavior of these materials. First choice has been focused on the Mean-field homogenization methods to study the elasto-plastic behavior and ductile damage phenomena in composites. Although restrictive, these techniques remain the best in terms of computational cost and efficiency. Two methods were investigated for this purpose: the Incremental Scheme Micromechanics (IMS) in One-site modeling and the Mori-Tanaka model in multi-site modeling (MTMS). In the framework of elastoplasticity, we have shown and validated by finite element method that the IMS homogenization results are more accurate, when dealing with high volume fraction composites, than the Mori-Tanaka model, frequently used in the literature. Furthermore, we have extended the Mori-Tanaka's model (MT) generally formulated in One-site to the multi-site formulation for the study of elasto-plastic behavior of composites with ordered microstructure. This approach shows that the multi-site formulation produces consistent results with respect to finite element and experimental solutions. In the continuation of our research, the Lemaître-Chaboche ductile damage model has been included to the study of elasto-plastic behavior in composite through the IMS homogenization. This latest investigation demonstrates the capability of the IMS model to capture damage effects in the material. However, the issue on the loss of ellipticity was not addressed. Finally we develop a numerical homogenization tool based on computational homogenization. This novel numerical tool works with 2D and 3D structure and is fully integrated in the conventional finite element code ABAQUS through its subroutine UMAT. The (FE2) method offers the advantage of being extremely accurate and allows the handling of more complex physics and geometrical nonlinearities. Linear and non-linear cases were studied. In addition, its combination with ABAQUS allows the use of major resources provided by this software (a panel of toolbox for various mechanical, thermomechanical and electrical analysis) for the study of multi-physics problems. This work was validated in the linear case on a two-scale analysis in bending and compared to the multi-scale method ANM (Nezamabadi et al. (2009)). Extensive work will be needed later with applications on non-linear problems to highlight the value of the developed tool
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Gu, Shui-Tao. "Contributions à la modélisation des interfaces imparfaites et à l'homogénéisation des matériaux hétérogènes." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00470541.
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En mécanique des matériaux et des structures, l'interface entre deux composants matériels ou deux éléments structuraux est traditionnellement et le plus souvent supposé parfaite. Au sens mécanique, une interface parfaite est une surface à travers laquelle le vecteur de déplacement et le vecteur de contrainte sont tous les deux continus. L'hypothèse des interfaces parfaites est inappropriée dans de nombreuses situations en mécanique. En effet, l'interface entre deux corps ou deux parties d'un corps est un endroit propice aux réactions physico-chimiques complexes et favorable à l'endommagement mécanique. L'intérêt pour les interfaces imparfaites devient depuis quelques années grandissant avec le développement des matériaux et structures nanométriques dans lesquels les interfaces et surfaces jouent un rôle prépondérant. A partir de la configuration de base où une interphase de faible épaisseur sépare deux phases, ce travail établit trois modèles d'interface imparfaite généraux qui permettent de remplacer l'interphase par une interface imparfaite dans les cas de la conduction thermique, de l'élasticité linéaire et de la piézoélectricité sans perturber les champs en questions à une erreur fixée près. La dérivation de ces modèles est basée sur le développement de Taylor et sur une approche originale de géométrie différentielle indépendante de tout système de coordonnées. Les trois modèles généraux permettent non seulement de mieux appréhender certains modèles phénoménologiques d'interface imparfaite mais aussi de décrire les effets d'interface que les modèles existants ne sont pas en mesure de prendre en compte. Les modèles d'interface imparfaite établis sont appliqués dans la détermination des propriétés effectives thermiques, élastiques et piézoélectriques d'un matériau composite constitué d'une matrice renforcée par des particules ou fibres enrobées d'une interphase. La méthode utilisée pour rendre compte des effets des interfaces imparfaites sur les propriétés effectives repose sur une condition d'équivalence énergétique qui ramène un matériau hétérogène avec interfaces imparfaites à un matériau hétérogène avec interfaces parfaites
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Le, Huy Toan. "Homogénéisation des interfaces ondulées dans les composites." Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00647889.
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Les surfaces et interfaces rugueuses sont rencontrées dans de nombreuses situations en mécanique et physique des solides. En particulier, une surface ou interface considérée comme lisse à une échelle donnée se révèle souvent rugueuse à autre échelle plus petite. Ce travail étudie les interfaces planes et courbées dont la rugosité peut être raisonnablement décrite comme des ondulations périodiques. Il a pour objectif de modéliser ces interfaces dans des composites et de déterminer leurs effets sur les propriétés effectives élastiques et conductrices des composites concernés. L'approche élaborée pour atteindre cet objectif consiste d'abord à utiliser l'analyse asymptotique pour modéliser une zone d'interface rugueuse comme une interphase hétérogène uniquement suivant son épaisseur et ensuite à faire appel à des schémas micromécaniques pour quantifier les influences de cette interphase sur les propriétés effectives. Ce travail considère trois types de composites dans lesquels de s interfaces périodiquement ondulées sont présentes : composites stratifiés, fibreux et à inclusions. Les résultats obtenus pour ces composites contribuent au développement de la micromécanique et apportent des solutions à des problèmes d'intérêt pratique rencontrés en physique et mécanique des matériaux hétérogènes
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Mihai, Iulia. "Micromechanical constitutive models for cementitious composite materials." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/24624/.
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A micromechanical constitutive model for concrete is proposed in which microcrack initiation, in the interfacial transition zone between aggregate particles and cement matrix, is governed by an exterior-point Eshelby solution. The model assumes a two-phase elastic composite, derived from an Eshelby solution and the Mori-Tanaka homogenization method, to which circular microcracks are added. A multi-component rough crack contact model is employed to simulate normal and shear behaviour of rough microcrack surfaces. It is shown, based on numerical predictions of uniaxial, biaxial and triaxial behaviour that the model captures key characteristics of concrete behaviour. An important aspect of the approach taken in this work is the adherence to a mechanistic modelling philosophy. In this regard the model is distinctly more rigorously mechanistic than its more phenomenological predecessors. Following this philosophy, a new more comprehensive crack-plane model is described which could be applied to crack-planes in the above model. In this model the crack surface is idealised as a series of conical teeth and corresponding recesses of variable height and slope. Based on this geometrical characterization, an effective contact function is derived to relate the contact stresses on the sides of the teeth to the net crack-plane stresses. Plastic embedment and frictional sliding are simulated using a local plasticity model in which the plastic surfaces are expressed in terms of the contact surface function. Numerical simulations of several direct shear tests indicate a good performance of the model. The incorporation of this crack-plane model in the overall constitutive model is the next step in the development of the latter. Computational aspects such as contact related numerical instability and accuracy of spherical integration rules employed in the constitutive model are also discussed. A smoothed contact state function is proposed to remove spurious contact chatter behaviour at a constitutive level. Finally, an initial assessment of the performance of the micromechanical model when implemented in a finite element program is presented. This evaluation clearly demonstrates the capability of the proposed model to simulate the behaviour of plain and reinforced concrete structural elements as well as demonstrating the potential of the micromechanical approach to achieve a robust and comprehensive model for concrete.
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Wongsto, Anchana. "Micromechanical finite element analysis of composite materials." Thesis, University of Manchester, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488307.
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Hafeez, Farrukh. "Micromechanical analysis of cracked laminates of composite materials." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511927.
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Josefsson, Gabriella. "Elasticity of Cellulose Nanofibril Materials." Doctoral thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-240250.
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The demand for renewable load-carrying materials is increasing with increasing environmental awareness. Alternative sources for materials manufacturing and design have to be investigated in order to replace the non-biodegradable materials. The work presented in this thesis investigates structure-property relations of such renewable materials based on cellulose nanofibrils. Cellulose is the most abundant polymer on earth and exists in both ordered and disordered phases, where the ordered crystalline cellulose shows excellent mechanical properties. The celluloses nanofibril is composed of partly crystalline cellulose where the stiff crystal regions, or crystallites, are orientated in the axial direction of the fibrils. The cellulose nanofibrils have a high aspect ratio, i.e. length to diameter ratio, with a diameter of less than 100 nm and a length of some micrometres. In the presented work, different properties of the cellulose nanofibril were studied, e.g. elastic properties, structure, and its potential as a reinforcement constituent. The properties and behaviour of the fibrils were studied with respect to different length scales, from the internal structure of the cellulose nanofibril, based on molecular dynamic simulations, to the macroscopic properties of cellulose nanofibril based materials. Films and composite materials with in-plane randomly oriented fibrils were produced. Properties of the cellulose nanofibril based materials, such as stiffness, thickness variation, and fibril orientation distribution, were investigated, from which the effective elastic properties of the fibrils were determined. The studies showed that a typical softwood based cellulose nanofibril has an axial stiffness of around 65 GPa. The properties of the cellulose nanofibril based materials are highly affected by the dispersion and orientation of the fibrils. To use the full potential of the stiff fibrils, well dispersed and oriented fibrils are essential. The orientation distribution of fibrils in hydrogels subjected to a strain was therefore investigated. The study showed that the cellulose nanofibrils have high ability to align, where the alignment increased with increased applied strain.
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YI, WEITAO. "MICROMECHANICS BASED COMPOSITE MATERIAL MODELS FOR CRASHWORTHINESS FINITE ELEMENT SIUMLATION." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990541929.
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Wang, Yaou. "Failure mechanism and reliability prediction for bonded layered structure due to cracks initiating at the interface." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1236645979.
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Marklund, Erik. "Micromechanism based material models for natural fiber composites /." Luleå : Luleå University of Technology, 2005. http://epubl.luth.se/1402-1757/2005/84.
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Case, Scott Wayne. "Mechanics of Fiber-Controlled Behavior in Polymeric Composite Materials." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30568.
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Modern durability and damage tolerance predictions for composite material systems rely on accurate estimates of the local stress and material states for each of the constituents, as well as the manner in which the constituents interact. In this work, an number of approaches to estimating the stress states and interactions are developed. First, an elasticity solution is presented for the problem of a penny-shaped crack in an N-phase composite material system opened by a prescribed normal pressure. The stress state around such a crack is then used to estimate the stress concentrations due to adjacent fiber fractures in a composite materials. The resulting stress concentrations are then used to estimate the tensile strength of the composite. The predicted results are compared with experimental values.
In addition, a cumulative damage model for fatigue is presented. Modifications to the model are made to include the effects of variable amplitude loading. These modifications are based upon the use of remaining strength as a damage metric and the definition of an equivalent generalized time. The model is initially validated using results from the literature. Also, experimental data from APC-2 laminates and IM7/K3B laminates are used in the model. The use of such data for notched laminates requires the use of an effective hole size, which is calculated based upon strain distribution measurements. Measured remaining strengths after fatigue loading are compared with the predicted values for specimens fatigued at room temperature and 350°F (177°C).<br>Ph. D.
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Cheng, Chun-Chung. "3-D finite element method for micromechanical analysis in fibrous composite material." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA302950.
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Sreeranganathan, Arun. "Realistic micromechanical modeling and simulation of two-phase heterogeneous materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24607.
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Thesis (Ph.D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Gokhale, Arun; Committee Member: Gall, Kenneth; Committee Member: Garmestani, Hamid; Committee Member: Kurtis, Kimberly; Committee Member: Thadhani, Naresh
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Gardner, Jeffrey P. (Jeffrey Philip). "MIcromechanical modeling of composite materials in finite element analysis using an embedded cell approch." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/43275.
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Singh, Harpreet. "Computer simulations of realistic microstructures implications for simulation-based materials design/." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22564.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Dr. Arun Gokhale; Committee Member: Dr. Hamid Garmestani; Committee Member: Dr. Karl Jacob; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Steve Johnson.
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Haberman, Michael Richard. "Design of High Loss Viscoelastic Composites through Micromechanical Modeling and Decision Based Materials Design." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14599.
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This thesis focuses on the micromechanical modeling of particulate viscoelastic composite materials in the quasi-static frequency domain to approximate macroscopic damping behavior and has two main objectives. The first objective is the development of a robust frequency dependent multiscale model. For this purpose, the self-consistent (SC) mean-field micromechanical model introduced by Cherkaoui et al [J. Eng. Mater. Technol. 116, 274-278 (1994)] is extended to include frequency dependence via the viscoelastic correspondence principal. The quasi-static model is then generalized using dilute strain concentration tensor formulation and validated by comparison with complex bounds from literature, acoustic and static experimental data, and established models. The second objective is SC model implementation as a tool for the design of high loss materials. This objective is met by integrating the SC model into a Compromise Decision Support Protocol (CDSP) to explore the microstructural design space of an automobile windshield. The integrated SC-CDSP design space exploration results definitively indicate that one microstructural variable dominates structure level acoustic isolation and rigidity: negative stiffness. The work concludes with a detailed description of the fundamental mechanisms leading to negative stiffness behavior and proposes two negative stiffness inclusion designs.
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Pavan, Roberto Carlos. "Aplicação da Teoria de Dano na análise do comportamento de materiais compósitos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15301.
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A Mecânica do Dano Contínuo (MDC) teve importante desenvolvimento desde os trabalhos iniciais de Kachanov e Rabotnov sendo uma ferramenta prática para considerar processos de danificação em materiais e estruturas em nível de contínuo macroscópico. Neste trabalho, apresenta-se uma aplicação da teoria do dano anisotrópico baseada em teorias desenvolvidas a partir dos trabalhos de Murakami. Nas formulações apresentadas, o tensor de dano de quarta ordem M (que relaciona tensões aplicadas e tensões efetivas) é determinado com base no tensor Ω (densidade de área tridimensional devida ao dano) que, por sua vez, pode ser determinado com base em dados experimentais. São propostas três formulações teóricas que são transformadas em formulações incrementais e incorporadas em um programa computacional de elementos finitos (para placas e cascas laminadas em material compósito) que considera efeitos geométricos não-lineares. A primeira e segunda formulação são casos particulares da terceira formulação que é um modelo termodinâmico tridimensional. As forças termodinâmicas associadas à evolução do tensor de dano são deduzidas a partir da expressão da dissipação intrínseca. Um critério fenomenológico para o dano é proposto. Em consistência com a positividade da dissipação intrínseca é adotada uma regra de normalidade para a evolução da força termodinâmica. Também é proposta, baseada em dados experimentais, uma lei para o encruamento associada ao processo de dano. Os modelos são validados comparando resultados numéricos a soluções analíticas ou a resultados experimentais. A formulação viscoelástica é definida do dano elástico e por componentes viscoelásticas representadas no formato de variáveis de estado e, posteriormente, validadas através de resultados experimentais.<br>The Continuum Damage Mechanics (CDM) had important development since the initial works of Kachanov and Rabotnov and constitutes now a practical tool to account for macroscopic damage in materials and structures. In this work, an application of an anisotropic damage theory based in Murakami theory is presented. In the formulations presented here, the fourth order damage tensor M (that relates Cauchy stress and effective stress) is determined on the basis of the tensor Ω (damaged three-dimensional area density) that, can be determined through experimental data. The three theoretical formulations presented here are transformed into incremental formulations and implemented in a finite element program (for plates and shell structures in composite material) taking account of geometrically non-linear effects. The first and second formulations are particular cases of the third formularization that is a tridimensional model for continuous damage formulated. The thermodynamic force associated with the evolution of the damage tensor is deduced from the expression of the intrinsic dissipation. A phenomenological criterion for damage yielding is proposed. In consistence with the positivity of the intrinsic dissipation, a normality rule is adopted for the evolution of the thermodynamic force. In addition, a hardening law associated with the damage process is identified from available experiment results. The models are validated by comparison with closed-form solutions or with experiment results. The viscoelastic formulation is defined through damage elastic and viscous components and set in a state variables format and then validated by comparison with experimental creep tests.
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Blivi, Adoté Sitou. "Effet de taille dans les polymères nano-renforcés : caractérisation multi-échelles et modélisation." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2431/document.
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Le travail présenté dans ce document vise à mettre en évidence et à comprendre l'effet de la taille nanométrique des renforts sur les propriétés des nanocomposites avec une approche expérimentale. Des nanocomposites de PMMA et particules de silice (15nm, 25nm, 60nm, 150nm et 500nm) de fractions volumiques 2 0/0, 40/0 et 6 0/0 ont été fabriqués. Des analyses multi-échelles (MET et DRX-WAXS) ont montré que les paramètres caractéristiques de la microstructure des nanocomposites varient avec la taille des nanoparticules. En effet, la diminution de la taille des nanoparticules à fraction volumique constante a entrainé une diminution de la distance intermoléculaire. Cette diminution a induit une densification de la matrice et une réduction de la mobilité des chaînes de la matrice. Des essais mécaniques (traction, DMA) ont montré que les modules de Young (E) et de conservation (E') des nanocomposites augmentent avec la diminution de la taille des nanoparticules à fraction volumique constante. Et que l'augmentation de E' est conservée avec l'augmentation de la température. Une augmentation des températures de transition vitreuse (Tg) et de dégradation (Td) a également été observée avec les essais DSC, DMA et ATG. Le modèle de la borne inférieure d'Hashin-Shtrikman étendue aux nanocomposites à renforts sphériques proposé par Brisard a été utilisé. La modélisation des modules élastiques des nanocomposites a montré que pour reproduire les données expérimentales, il faut que d'une part que les modules surfaciques caractérisant l'interface soient dépendants de la taille des nanoparticules. Et d'autre part, tenir compte de l'état de dispersion des nanoparticules<br>The work presented in this paper aims to highlight and to understand the size effect of nano-reinforcements on nanocomposite properties With an experimental approach. Nanocomposites of PMMA and silica particles With different sizes (15nm, 25nm, 60nm, 150nm and 500nm) and volume fractions (20/0, 4 0/0 and 60/0) were manufactured. Multiscale analysis (MET and DRX-WAXS) have shown that the characteristic parameters of the microstructure of nanocomposites vary With the size of the nanoparticles. Indeed, the decrease in the size of nanoparticles at a given volume fraction implies a decrease of the intermolecular distance. This decrease has induced a densification of the matrix and a decrease of the matrix chain mobility. Mechanical tests (tensile, DMA) have shown that the young (E) and the conservation (E') moduli of the nanocomposites increase With the decrease in the size of the nanoparticles With a constant volume fraction. And the increase of E l is kept when temperature growing. An increase in glass transition (Tg) and degradation temperature (Td) was also observed With the DSC, DMA and ATG tests. Experimental elastic properties of the nanocomposites were used to assess the relevance of size effect micromechanical models, particularly the Hashin-Shtrikman bounds With interface effects proposed by Brisard. The modeling has shown that to reproduce the experimental elastic moduli of nanocomposites, the elastic coefficients of the interface must be dependents on particle sizes. And the state of dispersion of particles must be taken into account
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Milliren, Eric Carlton. "Nanocomposites a study of theoretical micromechanical behavior using finite element analysis /." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/milliren/MillirenE0509.pdf.
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Current research in nanotechnology has produced an increasing number of possibilities for advanced materials. Among those materials with potential advanced mechanical properties are fiber-reinforced composite laminates that utilize nanoscale fiber diameters. Through a combination of studying classic micromechanical models and modern computer-aided finite element analysis (FEA), the advantages for utilizing these nanofibers in advanced structural applications, such as space mirror backings, was investigated. The approach for modeling these composite structures was that of a Representative Volume Element (RVE). Using the program ABAQUS/CAE, a RVE was created with the goals of accurately comparing to the shear lag theory, effectively incorporating "interphase" zones that bond the constituents, and demonstrating effects of down-scaling fiber diameter. In this thesis, the progression of the ABAQUS model is thoroughly covered as it developed into a verified model correlating with the shear lag theory. The model produced was capable of utilizing interphase if desired, and was capable of off-axis loading scenarios. A MathCAD program was written in order to employ the published theoretical techniques, which were then compared to the FEA results for verification. The FEA model was found to work well in conjunction with the theory explored using MathCAD, after which the nanofiber FEA model showed some clear advantages over a conventional-sized model, specifically an increase in strength of the composite RVE. Finally, it was determined that the interfacial bonding strength plays a large role in the structure of the interphase zone, and thus the overall strength of the composite.
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Lee, Haeng-Ki. "Three-dimensional micromechanical damage models for effective elastic and elastoplastic behavior of composite materials with inhomogeneities or microcracks." Restricted to subscribing institutions, 1998. http://proquest.umi.com/pqdweb?did=1562125051&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Paul, Ewart D. "Micro-mechanical predictive modelling as an aid to CAD based analysis of composite sporting equipment." The University of Waikato, 2008. http://hdl.handle.net/10289/2509.
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The sport and leisure industry in New Zealand (NZ) has the potential to become a major user of composite materials. Given the size of NZ industry, design and manufacturing strategies based on virtual engineering should be developed to suit NZ requirements. Virtual methods use computer aided engineering capabilities to find faults, explore alternatives and optimise product performance before detailed design or prototyping. When doing computer aided simulation the required mechanical properties of individual reinforcement and matrix components are well documented. However, the mechanical properties of composite materials are not as simple to obtain. Micro-mechanical modelling could therefore be used to aid the design and development of composite equipment, where mechanical properties are unknown. In this study, solids modelling was used to produce an analog model of a composite, and it was found that it lead to reductions in file size and simulation time. Representing a composite with an analog model implies that the behavioural characteristics are modelled, but not the physical characteristics of the individual components. Three micro-mechanical models were developed to predict the flexural modulus of composite materials, based on perfect, partial and no adhesion. It was found that the partial adhesion model was both practical and consistently accurate. The partial adhesion model accounted for adhesion between components by considering an 'effective shear value' at the interface. Validation of the models was done by flexural testing injection moulded samples of glass, wood and carbon fibre reinforced polyethylene. It was shown that the adhesion coefficient range was 0.1 for carbon fibre, 0.5 for glass fibre and 0.9 for the wood fibre composites. It was concluded that the adhesion coefficient is crucial and it is recommended that further work is done to validate effective shear values by empirical means. The predicted flexural modulus values were used to enable finite element simulation of modelled analog beams as well as commercial kayak paddles. It was determined that accurate simulation is possible for composite equipment using the partial adhesion model.
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Sidhom, Maged. "Approches multi-échelles des composites granulaires avec effets d'interface : applications aux nanocomposites et composites cimentaires." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1175/document.
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Ce travail s'inscrit dans le contexte des recherches menées pour la modélisation des composites aléatoires, permettant de déterminer leurs propriétés mécaniques effectives (élasticité et résistance). Parmi les modèles micromécaniques, numériques ou analytiques, développés dans ce but, on retrouve certains qui prennent en compte les effets d'interfaces se produisant aux frontières des inclusions des composites. Ces interfaces ont, selon plusieurs auteurs, une grande influence sur les propriétés élastiques et de rupture. Les modèles les considérant à ce jour sont néanmoins limités aux cas d'inclusions sphériques ou cylindriques. Dans cette thèse, nous proposons plusieurs approches et modèles micromécaniques (ou multi-échelles) qui permettent de déterminer les propriétés élastiques et poroélastiques ainsi que les modes de ruptures de matériaux composites granulaires présentant divers effets d'interfaces. Les morphologies inclusionnaires étudiées ne se limitent pas à la forme sphérique mais s'étendent également aux inclusions ellipsoïdales ce qui nous a amené à examiner une rupture inter-granulaire anisotrope. Les modèles de rupture développés dans ce travail ont été appliqués aux gels de C-S-H (hydrates de la pâte de ciment) ce qui a permis d'améliorer les modèles de rupture consacrés aux pâtes durcies. Les prédictions de ces modèles ont pu être confrontées à des données expérimentales de résistance à la compression simple des pâtes<br>Modelling composite media in view of determining its effective mechanical behaviour has been the topic of a large number of research papers. Some analytical and numerical models that can be found in the scientific literature on this topic take into account the interface effects that can arise at inclusions' boundaries. These interfaces have a major influence on the mechanical properties of composites according to some researchers. However, the models considering them are limited to spherical and cylindrical inclusions. In this work, several multi-scale approaches and models are developed to consider interface effects in the determination of the effective elastic and poroelastic properties and the failure mechanisms of granular composites. These models are performed on both spherical and ellipsoidal shapes of inclusions. The latter has led us to investigate an anisotropic inter-granular failure in granular media. The failure models developed in this work are applied to the microstructure of C-S-H gels (a cement paste hydrate) in order to improve the existing models on cement paste failure. The predictions of these improved models are compared to experimental data on the compressive strength of cement pastes
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Willard, Bethany. "Micromechanical evaluation of interfacial shear strength of carbon/epoxy composites using the microbond method." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/16868.
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Master of Science<br>Department of Mechanical and Nuclear Engineering<br>Kevin Lease<br>Carbon fiber reinforced composites (CFRP’s) are a mainstay in many industries, including the aerospace industry. When composite components are damaged on an aircraft, they are typically repaired with a composite patch that is placed over the damaged material and cured into the existing composite material. This curing process involves knowledge of the curing time necessary to sufficiently cure the patch. The inexact nature of curing composites on aircraft causes a significant waste of time and material when patches are unnecessarily redone. Knowing how differences in cure cycle affect the strength of the final material could reduce this waste. That is the focus of this research.
In this research, the interfacial shear strength (IFSS) of carbon fiber/epoxy composites was investigated to determine how changes in cure cycle affect the overall material strength. IFSS is a measure of the strength of the bond between the two materials. To measure this, the microbond method was used. In this method, a drop of epoxy is applied to a single carbon fiber. The specimen is cured and the droplet is sheared from the fiber. The force required to debond the droplet is recorded and the data is analyzed.
The IFSS of AS4/Epon828, T650/Epon828, and T650/Cycom 5320-1 composites were evaluated. For the former two material systems, a cure cycle with two steps was chosen based on research from others and then was systematically varied. The final cure time was changed to determine how that parameter affected the IFSS. It was found that as the final cure time increased, so did the IFSS and level of cure achieved by the composite to a point. Once the composite reached its fully cured state, increasing the final cure time did not noticeably increase the IFSS.
For the latter material system (T650/Cycom 5320-1), the two cure cycles recommended by the manufacturer were tested. These had different initial cure steps and identical final cure steps. Although both cure cycles caused high IFSS, the cycle with the higher initial temperature, but shorter initial cure time achieved a higher level of cure than that with a longer time, but shorter temperature.
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AMINJIKARAI, SRINIVASA BABU. "A STRAIN RATE DEPENDENT 3D MICROMECHANICAL MODEL FOR FINITE ELEMENT SIMULATIONS OF PLAIN WEAVE COMPOSITE STRUCTURES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1070549522.
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Gibbons, Michael P. "Continuum-Scale Modeling of Shear Banding in Bulk Metallic Glass-Matrix Composites." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471882991.
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Goidescu, Cristina. "Caractérisation et modélisation de l'endommagement par microfissuration des composites stratifiés - Apports des mesures de champs et de l'homogénéisation." Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/7121/1/goidescu.pdf.
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Ce travail porte sur l'endommagement des matériaux composites stratifiés utilisés notamment pour la réalisation de pièces structurales minces. La dégradation de ces matériaux induite par la création et le développement de surfaces de décohésion internes est abordée sous deux angles. Une campagne expérimentale a tout d'abord été menée sur des stratifiés en carbone-époxy réalisés par infusion de résine liquide et sollicités en traction uniaxiale. Cette étude propose une analyse originale à l'aide de trois techniques optiques permettant une caractérisation de l'endommagement par mesures de champs : cinématiques (par stéréo-corrélation d'images), thermiques (par thermographie infrarouge) et densimétriques (par tomographie à rayons X). Le second volet du travail concerne la modélisation de la microfissuration dans le contexte d'une anisotropie initiale. A cette fin, une homogénéisation bidimensionnelle de milieux orthotropes fissurés permet la prise en compte de défauts d'orientation arbitraire et des effets unilatéraux (ouverture-fermeture des microfissures) au sein d'une formulation énergétique en déformation. Sur cette base, un modèle de comportement est proposé dans le cadre de la thermodynamique des processus irréversibles avec variables internes. Des simulations numériques permettent de démontrer les capacités prédictives de la formulation, en particulier la représentation du comportement non linéaire de ces matériaux, l'interaction entre les anisotropies initiale et induite et la restitution des propriétés élastiques lors de la fermeture de défauts.
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Goyal, Deepak. "Analysis of linear elasticity and non-linearity due to plasticity and material damage in woven and biaxial braided composites." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2405.
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Mao, Yuxiong. "Computer simulations of realistic three-dimensional microstructures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33954.
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A novel and efficient methodology is developed for computer simulations of realistic two-dimensional (2D) and three-dimensional (3D) microstructures. The simulations incorporate realistic 2D and 3D complex morphologies/shapes, spatial patterns, anisotropy, volume fractions, and size distributions of the microstructural features statistically similar to those in the corresponding real microstructures. The methodology permits simulations of sufficiently large 2D as well as 3D microstructural windows that incorporate short-range (on the order of particle/feature size) as well as long-range (hundred times the particle/feature size) microstructural heterogeneities and spatial patterns at high resolution. The utility of the technique has been successfully demonstrated through its application to the 2D microstructures of the constituent particles in wrought Al-alloys, the 3D microstructure of discontinuously reinforced Al-alloy (DRA) composites containing SiC particles that have complex 3D shapes/morphologies and spatial clustering, and 3D microstructure of boron modified Ti-6Al-4V composites containing fine TiB whiskers and coarse primary TiB particles. The simulation parameters are correlated with the materials processing parameters (such as composition, particle size ratio, extrusion ratio, extrusion temperature, etc.), which enables the simulations of rational virtual 3D microstructures for the parametric studies on microstructure-properties relationships. The simulated microstructures have been implemented in the 3D finite-elements (FE)-based framework for simulations of micro-mechanical response and stress-strain curves. Finally, a new unbiased and assumption free dual-scale virtual cycloids probe for estimating surface area of 3D objects constructed by 2D serial section images is also presented.
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Alia, Adem. "Comportement à la rupture d'un composite à fibres végétales." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI016.
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L’objectif de cette thèse est la caractérisation du comportement mécanique et de l’endommagement d’un composite tissé jute/polyester. Les fibres végétales constituent en effet une alternative écologique intéressante à l’utilisation des fibres synthétiques, en particulier les fibres de verre qui sont les plus utilisées pour les pièces composites de grande diffusion. Le composite est développé au sein du laboratoire LMNM à l’IOMP, Sétif, Algérie. Deux orientations ([0]8 et [+45/-45]2S) sont considérées. La caractérisation mécanique est effectuée en traction et compression monotones ainsi qu’en fatigue cyclique. Les caractérisations mécaniques et microstructurales sont réalisées au sein du laboratoire MATEIS. L’étude de l’endommagement des composites est réalisée en combinant cinq techniques : l’évolution des paramètres mécaniques via des essais cyclés et de fatigue, la microscopie, l’émission acoustique (EA), la corrélation d’images et la micro-tomographie RX. L’étude de l’évolution des paramètres mécaniques accompagnée de l’analyse globale de l’EA fournit des premiers indicateurs quant au développement de l’endommagement lors des essais. Les analyses microstructurales permettent d’identifier finement les différents mécanismes d’endommagement qui surviennent lors des sollicitations mécaniques (décohésions fibre/matrice, fissurations matricielles et rupture de fibres). Pour la segmentation des signaux d’émission acoustique en traction et en compression monotones, une classification non-supervisée est utilisée en mettant l’accent sur le choix des descripteurs et sur la labellisation des classes obtenues. Des essais de traction instrumentés par corrélation d’images ainsi que des essais de traction in-situ sous tomographe permettent d’identifier la chronologie d’apparition de l’endommagement. Ces résultats permettent également de labelliser les classes obtenues. Les signaux labellisés servent ensuite à créer une bibliothèques pour identifier la chronologie d’évolution des modes d’endommagement en fatigue cyclique réalisée par classification supervisée. Enfin, toutes ces analyses ont permis d’établir des scénarios d’endommagement pour les différents modes d’endommagement et pour les deux orientations. Il est ainsi possible de reconsidérer l’élaboration pour optimiser les propriétés mécaniques<br>The objective of this thesis is the characterization of the mechanical behavior and the damage of a woven jute / polyester composite. natural fibers are indeed an interesting ecological alternative to synthetic fibers, in particular glass fibers which are the most used for composite manufacturing. The studied composite is developed in the LMNM laboratory at IOMP, Sétif, Algeria. Two fibre orientations ([0] 8 and [+ 45 / -45] 2S) are considered. The mechanical characterization is carried out in monotonic tensile and compression as well as in cyclic fatigue. Mechanical and microstructural characterizations are carried out in the MATEIS laboratory. The study of the damage is carried out by combining five techniques: the evolution of mechanical parameters via cyclic and fatigue tests, microscopy, acoustic emission (EA), image correlation and micro- RX tomography. The study of the evolution of the mechanical parameters combined with the global analysis of the AE provides first indicators concerning the development of the damage during the tests. Microstructural analyzes allow to finely identify the damage mechanisms that occur during mechanical tests (fiber / matrix decohesions, matrix cracks and fiber breakage). For the segmentation of acoustic emission signals in monotonic tests, an unsupervised classification is used, emphasizing the choice of descriptors and the labeling of the classes obtained. Tensile tests instrumented by image correlation as well as in situ tensile tests under tomography allow to identify the chronology of appearance of the damage. These results are also used to label the obtained classes . The labeled signals are then used to create a library to identify the chronology of evolution of the modes of damage in cyclic fatigue achieved by supervised classification. Finally, all these analyzes made it possible to establish damage scenarios for the different damage modes and for the two orientations. It is thus possible to reconsider the development to optimize the mechanical properties