Bibliografias temáticas / Variable and anisotropic composites

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Literatura científica selecionada sobre o tema "Variable and anisotropic composites"

Autor: Grafiati

Publicado: 14 de setembro de 2024

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Artigos de revistas sobre o assunto "Variable and anisotropic composites"

Robinson, D. N., e W. K. Binienda. "A Representation of Anisotropic Creep Damage in Fiber Reinforced Composites". Journal of Applied Mechanics 72, n.º 4 (28 de outubro de 2004): 484–92. http://dx.doi.org/10.1115/1.1875512.

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A creep damage model is presented that allows for anisotropic distributions of damage in composite materials. An earlier model by the writers allowed for anisotropic damage growth rate but, based on a scalar state variable, failed to account for anisotropic distributions of damage. A vectorial state variable is introduced that allows a representation of anisotropic damage distribution. As in earlier work, a fundamental assumption is that the principally damaging stress components are tensile traction and longitudinal shear at the fiber/matrix interface. Application of the creep damage model is made to calculations involving homogenously stressed composite elements under transverse tensile and longitudinal shear stress and to cross plied thin-walled tubes under tension/torsion. Although the emphasis is phenomenological, with focus on a mathematical structure for representing anisotropic distributions of damage, a meaningful creep damage model must rest on fundamental material science and microstructural examination. Verification experiments involving tension/torsion testing of thin-walled composite tubes together with detailed microstructural examination are discussed and outlined.

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Chang, Yan Jun, Ke Shi Zhang, Gui Qiong Jiao e Jian Yun Chen. "Application and Analysis of Plane Woven C/SiC Composites Based on Continuum Damage Mechanics". Advanced Materials Research 490-495 (março de 2012): 3916–19. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3916.

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The aim of this article was to propose a macroscopic damage model, which describes the nonlinear behavior observed on woven C/SiC ceramic matrix composites. The model was built within a thermodynamic framework with internal variables. The anisotropic damage evolution processes of the material were described by nonlinear damage isotropic and kinematic hardening functions in this model. The anisotropic damage and damage coupling were considered with a damage yield function including anisotropic coefficients. Using the principle of energy equivalence, the damage variables were defined by the unloading modulus and initial modulus. The damage variable and the irrecoverable strain induced by micro-crack propagation were deduced by thermodynamics. The constants of constitutive model were identified and the damage evolution processes under tensile and shear loading. Uniaxial tension and shear tests had been used to valid the constitutive model to C/SiC composites.

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Lu, C. H. "Bending of Anisotropic Sandwich Beams with Variable Thickness". Journal of Thermoplastic Composite Materials 7, n.º 4 (outubro de 1994): 364–74. http://dx.doi.org/10.1177/089270579400700406.

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Mir, Hicham, Mario Fafard, Benoı^t Bissonnette e Marie-Laure Dano. "Damage Modeling in Random Short Glass Fiber Reinforced Composites Including Permanent Strain and Unilateral Effect". Journal of Applied Mechanics 72, n.º 2 (1 de março de 2005): 249–58. http://dx.doi.org/10.1115/1.1839593.

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This paper presents the development of a theoretical damage mechanics model applicable to random short glass fiber reinforced composites. This model is based on a macroscopic approach using internal variables together with a thermodynamic potential expressed in the stress space. Induced anisotropic damage, nonsymmetric tensile/compressive behavior (unilateral effect) and residual effects (permanent strain) are taken into account. The anisotropic damage is represented with second-order tensorial internal variables D. The unilateral effect due to microcrack closure in compression is introduced by generalizing the hypothesis of the complementary elastic energy equivalence. In the case of the permanent strain, a new term related to frozen energy, which is a function of the damage variable, the stress tensor, and some materials constants to be identified, is added to the basic thermodynamic potential. Using laboratory test results, parameter identification has been performed to illustrate the applicability of the proposed model.

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Bittrich, Lars, Axel Spickenheuer, José Humberto S. Almeida, Sascha Müller, Lothar Kroll e Gert Heinrich. "Optimizing Variable-Axial Fiber-Reinforced Composite Laminates: The Direct Fiber Path Optimization Concept". Mathematical Problems in Engineering 2019 (19 de fevereiro de 2019): 1–11. http://dx.doi.org/10.1155/2019/8260563.

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The concept of aligning reinforcing fibers in arbitrary directions offers a new perception of exploiting the anisotropic characteristic of the carbon fiber-reinforced polymer (CFRP) composites. Complementary to the design concept of multiaxial composites, a laminate reinforced with curvilinear fibers is called variable-axial (also known as variable stiffness and variable angle tow). The Tailored Fiber Placement (TFP) technology is well capable of manufacturing textile preforming with a variable-axial fiber design by using adapted embroidery machines. This work introduces a novel concept for simulation and optimization of curvilinear fiber-reinforced composites, where the novelty relies on the local optimization of both fiber angle and intrinsic thickness build-up concomitantly. This framework is called Direct Fiber Path Optimization (DFPO). Besides the description of DFPO, its capabilities are exemplified by optimizing a CFRP open-hole tensile specimen. Key results show a clear improvement compared to the current often used approach of applying principal stress trajectories for a variable-axial reinforcement pattern.

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Kawai, Masamichi, H. Kamioka, Jian Qi Zhang e Tetsuya Matsuda. "Off-Axis Creep Recovery of Unidirectional Carbon/Epoxy Composites at High Temperature". Key Engineering Materials 334-335 (março de 2007): 65–68. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.65.

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Off-axis creep recovery behavior after complete unloading during creep at a constant stress is examined for a unidirectional T800H/3631 carbon/epoxy composite laminate at high temperature. Creep and creep recovery tests are performed on plain coupon specimens with four kinds of fiber orientations: 10, 30, 45 and 90°. It is observed that the creep strain appeared at a high stress does not completely recover after full removal of the creep stress, indicating that an irrecoverable creep strain has developed under the prior constant stress loading. Variable stress creep simulations are attempted using the modified kinematic hardening model for homogenized anisotropic inelastic composites in which an accelerated change in kinematic hardening over a certain range of viscoplastic strain is considered. Comparison with experimental results demonstrates that the proposed model can adequately describe the off-axis creep and creep recovery behaviors of the unidirectional composite system under constant and variable stress conditions.

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Almeida, José Humberto S., Lars Bittrich, Tsuyoshi Nomura e Axel Spickenheuer. "Cross-section optimization of topologically-optimized variable-axial anisotropic composite structures". Composite Structures 225 (outubro de 2019): 111150. http://dx.doi.org/10.1016/j.compstruct.2019.111150.

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Shafei, Erfan, Shirko Faroughi e Timon Rabczuk. "Multi-patch NURBS formulation for anisotropic variable angle tow composite plates". Composite Structures 241 (junho de 2020): 111964. http://dx.doi.org/10.1016/j.compstruct.2020.111964.

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Kakade, Ramakant S., Dr Ajay Chavan e Prof Mayuri S. Mhaske. "Analysis of Epoxy Fiber Composite Clamp with Variable Slotted Holes for Electric Overhead Crane Mounting". International Journal of Innovative Research in Advanced Engineering 10, n.º 10 (10 de dezembro de 2023): 722–26. http://dx.doi.org/10.26562/ijirae.2023.v1010.02.

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Composite materials offer an excellent solution for structural applications requiring a high strength-to-weight ratio and stiffness-to-weight ratio. This is particularly beneficial in weight-sensitive structures like aircraft and spacecraft, where the cost-effectiveness of composite materials becomes evident. The exploration of composite materials encompasses various aspects, such as manufacturing processes, anisotropy, the elasticity strength of anisotropic materials, and micromechanics. This study focuses on the investigation of a novel glass epoxy composite material as a substitute for expensive, heavy, and corroding metals in applications involving tensile loadings. The objective is to experimentally analyze and employ finite element methods to understand the mechanical behavior of composite components, specifically those featuring slotted holes. Furthermore, the study aims to validate these findings using the finite element analysis (FEA) method.

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Kurkin, Evgenii, Oscar Ulises Espinosa Barcenas, Evgenii Kishov e Oleg Lukyanov. "Topology Optimization and Efficiency Evaluation of Short-Fiber-Reinforced Composite Structures Considering Anisotropy". Computation 12, n.º 2 (12 de fevereiro de 2024): 35. http://dx.doi.org/10.3390/computation12020035.

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The current study aims to develop a methodology for obtaining topology-optimal structures made of short fiber-reinforced polymers. Each iteration of topology optimization involves two consecutive steps: the first is a simulation of the injection molding process for obtaining the fiber orientation tensor, and the second is a structural analysis with anisotropic material properties. Accounting for the molding process during the internal iterations of topology optimization makes it possible to enhance the weight efficiency of structures—a crucial aspect, especially in aerospace. Anisotropy is considered through the fiber orientation tensor, which is modeled by solving the plastic molding equations for non-Newtonian fluids and then introduced as a variable in the stiffness matrix during the structural analysis. Structural analysis using a linear anisotropic material model was employed within the topology optimization. For verification, a non-linear elasto-plastic material model was used based on an exponential-and-linear hardening law. The evaluation of weight efficiency in structures composed of short-reinforced composite materials using a dimensionless criterion is addressed. Experimental verification was performed to confirm the validity of the developed methodology. The evidence illustrates that considering anisotropy leads to stiffer structures, and structural elements should be oriented in the direction of maximal stiffness. The load-carrying factor is expressed in terms of failure criteria. The presented multidisciplinary methodology can be used to improve the quality of the design of structures made of short fiber-reinforced composites (SFRC), where high stiffness, high strength, and minimum mass are the primary required structural characteristics.

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Mais fontes

Teses / dissertações sobre o assunto "Variable and anisotropic composites"

Chevalier, Romain. "Modélisation multi-échelles du comportement hygro-mécanique et étude de la stabilité dimensionnelle de structures composites lamellées collées aboutées en Pinus pinaster (Ait.)". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0057.

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Cette thèse porte sur le développement de modèles multi-échelles du comportement hygro-mécanique pour l'étude de la stabilité dimensionnelle de lamellés collés aboutés (LCAs) en Pinus pinaster (Ait.). Les structures en bois sont soumises à des variations dimensionnelles dues aux modifications des ambiances climatiques. Dans le cadre des structures LCAs, la stabilité dimensionnelle peut être atteinte via une conception systématique en fonction des propriétés des lamelles constituantes. Dans ce but, un modèle multi-échelles reposant sur une étude bibliographique exhaustive des propriétés du Pinus pinaster (Ait.) a été développé. Ce modèle permet d'obtenir spatialement, grâce à l'utilisation d'une méthode d'homogénéisation numérique et d'un métamodèle basé sur les hypersurfaces Non-Uniform Rational Basis-Spline (NURBS), les propriétés hétérogènes, variables et anisotropes de lamelles de Pinus pinaster (Ait.). De plus, des configurations de LCAs, reposant sur la théorie des stratifiés, ont été proposées et soumises expérimentalement à des variations d'ambiance climatiques. Les déplacements induits sont mesurés grâce à une méthode de corrélation d'images numériques. In fine, une comparaison des déplacements est réalisée qui permet de recommander des configurations de LCAs améliorant la stabilité dimensionnelle des LCAs du groupe Gascogne Bois
This thesis focuses on the development of a multi-scale model of the hygro-mechanical behaviour and the study of the shape stability of glued laminated timber (GLT) made of Pinus pinaster (Ait.). Wooden structures are subject to dimensional variations due to changes in climatic conditions. In the case of GLT structures, shape stability can be achieved through systematic design based on the properties of the constituent lamellae. To this end, a multi-scale model based on an exhaustive bibliographic study of the properties of Pinus pinaster (Ait.) has been developed. Using a numerical homogenisation method and a metamodel based on Non-Uniform Rational Basis-Spline (NURBS) hypersurfaces, this model provides a spatial representation of the heterogeneous, variable, and anisotropic properties of Pinus pinaster (Ait.) lamellae. In addition, configurations of GLTs, based on laminate theory, have been proposed and experimentally subjected to variations in climatic conditions. The induced displacements are measured using a digital image correlation method. Finally, a comparison of the displacements is carried out, enabling the recommendation of GLT configurations that improve the shape stability of the GLTs produced by the Gascogne Bois company

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McKernan, Scott John. "Anisotropic tensile probabilistic failure criterion for composites". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237601.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 1990.
Thesis Advisor(s): Wu, Edward M. "June 1990." Description based on title screen as viewed on October 16, 2009. Author(s) subject terms: Composite materials, probabilistic failure criterion, combined stress. Includes bibliographical references (p. 151). Also available in print.

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Bradford, Ian David Richard. "Finite deformations of highly anisotropic materials". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334952.

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Mohamed, Abdel-Mohsen Onsy. "Performance of an anisotropic clay under variable stresses". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75342.

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In the true triaxial test procedure used for testing laboratory-prepared kaolinite clay samples, undrained (with constant mean stress) strength tests were conducted to study the yield and failure of the clays. The principle concern focussed around the influence of orientation of particle bedding plane on the development of yield and failure characteristics of the clay. As the true triaxial cell permits variations of the three principal stresses, it was possible to study the soil response in any chosen quadrant of the principal space.
As a consequence to what is mentioned above, two types of consolidated undrained true triaxial tests were conducted in this study. In the first type, specimens were trimmed from the block sample with 90, 60, 30 and 0 degree orientation angles of particle's bedding planes; these angles were measured with respect to the direction of the major principal stress axis. For each degree of inclination, specimens were tested with three confining pressures 207, 276 and 345 kPa, and for each value of confining pressure, the loading path was varied from compression to tension.
The degree of dissociation between the stress and strain increment vectors was seen to depend on both initial and stress induced anisotropy.
Most important of all, a constitutive relationship for anisotropic kaolinite clay was derived on the basis of the observed experimental behaviour of soil samples under loading.
Additionally, anisotropy is characterized by a double transformation technique. The first transformation accounts for the directional dependency whilst the second transformation concerns itself with anisotropy of the base vectors. The relative joint invariant principle is used to calculate the degree of dissociation during the loading process. The variation of the dissociation angle during the loading process can be considered as a measure of the evolution of the resultant anisotropy. The model has shown to provide viable predictions of the stress-strain relationships obtained from true triaxial tests on an anisotropic kaolinite clay for: (a) different inclinations of particle's bedding planes, (b) different stress paths in one sector, (c) different stress paths in other sectors, and (d) the failure surfaces for different inclinations of particle's bedding planes in the octahedral plane. (Abstract shortened with permission of author.)

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Senan, Anish Sen. "Determination of the Viscoelastic Properties of General Anisotropic Materials". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/SenanAS2003.pdf.

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Bourn, Steven. "Anisotropic behaviour of magneto-electric coupling in multiferroic composites". Thesis, University of Central Lancashire, 2018. http://clok.uclan.ac.uk/23578/.

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The anisotropy of the direct magnetoelectric effect in textured nickel ferrite/lead zirconate titanate strain mediated bilayer composites has been studied. The magnetic layers of these samples have been crystallographically textured in planes of the form {100}, {110} and {111}. In this study, it is shown that the optimum bias field and the maximum magnetoelectric coupling signal can be controlled by changing the alignment of the applied magnetic field with respect to the magnetocrystalline anisotropy directions. It is also shown that the product of the optimum bias field and the maximum magnetoelectric coupling signal are proportional to the theoretical saturation magnetostriction. The samples have been magnetically characterised using a recommissioned and developed biaxial vibrating sample magnetometer, capable of detecting the component of a sample’s magnetic moment in 2 perpendicular directions and thus determining the net magnetic moment vector of the sample. Coupled with sample rotation this allows insight into the magnetic anisotropy of the sample, which has been compared with a micromagnetic model. A specialist magnetoelectric coupling rig has also been developed to allow application of DC and AC magnetic fields to a sample simultaneously. As part of the magnetic anisotropy study, a modified torque magnetometry method has been developed to enhance the identification of the anisotropy directions in magnetically soft samples, as well as a method by which torque magnetometry can be approximated using the in-field direction component of magnetisation as measured using a standard vibrating sample magnetometer.

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Costa, Luan Mayk Torres. "Modélisation micromécanique à variables internes du comportement viscoélastique anisotrope des matériaux hétérogènes : applications aux composites à matrice organique". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0116.

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L'objectif principal de la thèse consiste à développer une approche micromécanique pour prédire le comportement viscoélastique macroscopique des matériaux hétérogènes à partir des propriétés locales des constituants et de leur microstructure. Les propriétés viscoélastiques effectives sont obtenues par l'utilisation des méthodes d'homogénéisation à champ moyen appropriées. L'approche micromécanique proposée est basée sur une loi constitutive fonctionnelle ayant la forme d'une intégrale de Volterra. Dans un premier temps, nous obtenons une formulation micromécanique à variables internes développée avec le module de relaxation. Dans un autre temps, nous développons une deuxième approche micromécanique cette fois-ci écrite avec le module de fluage, consistant à la formulation duale à la première. À l'aide des techniques des fonctions de Green, nous établissons, dans les deux cas, une équation intégrale décrivant le problème viscoélastique hétérogène. Cette équation principale fait apparaître un terme intégral de volume difficile à évaluer directement, ce qui nous amène à construire une deuxième équation intégrale complémentaire venant s'ajouter à la première. Cette formulation générale définie par ces deux équations intégrales est appliquée au problème classique de l'inclusion viscoélastique d'Eshelby. La solution exacte du problème est obtenue dans le cas d'une morphologie ellipsoïdale arbitraire de l'inclusion ayant un comportement viscoélastique anisotrope et plongée dans une matrice viscoélastique isotrope. Nous utilisons une méthode à variables internes qui considère que l'histoire du matériau est contenue dans son état interne. La résolution de l'approche directement dans l'espace-temps nous conduit à une solution exacte avec un gain appréciable de temps de calcul, en comparant avec les résultats obtenus par les approches héréditaires, traitées dans l'espace de Laplace-Carson. Les deux formulations proposées permettent d'évaluer l'effet du comportement anisotrope et de la morphologie ellipsoïdale des inclusions, tout en permettant également d'étudier l'influence du vieillissement sur le comportement mécanique du composite. Les deux modèles obtenus présentent des résultats cohérents avec ceux disponibles dans la littérature, en permettant un gain de calcul intéressant par rapport aux méthodes existantes
The primary aim of this thesis is to devise a novel micromechanical approach for predicting the macroscopic viscoelastic response of heterogeneous materials. The behavior is achieved through micromechanical modeling that is based on local properties and microstructure. The effective viscoelastic properties are obtained by the use of appropriate mean-field homogenization methods. The mechanical approach is based on a Volterra integral-form functional constitutive law. Firstly, a new internal variable micromechanical formulation is obtained by utilizing the relaxation modulus. Secondly, a second micromechanical approach is developed, which employs the creep modulus and consists to the dual formulation. Using Green's function techniques, we derive integral equations that describe the heterogeneous viscoelastic problem for both cases. The main equation contains a challenging volume integral term, which necessitates the development of a second complementary integral equation. These two integral equations form the general formulation that we apply to the classical Eshelby viscoelastic inclusion problem. We employ an internal variable method that considers the material's history to be contained in its internal state. The approach is solved directly in the time domain, resulting in an exact solution with reduced computation time compared to hereditary approaches processed in the Laplace-Carson space. Our model enables us to evaluate the impact of anisotropic inclusions and to examine the influence of aging behavior on the composite viscoelastic properties. Both approaches proposed in this thesis deliver results that are consistent with those reported in the literature and offer a significant computational advantage over existing methods

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Yalcin, Omer Fatih. "A Dynamic Theory For Laminated Composites Consisting Of Anisotropic Layers". Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607116/index.pdf.

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In this thesis, first a higher order dynamic theory for anisotropic thermoelastic plates is developed. Then, based on this plate theory, two dynamic models, discrete and continuum models (DM and CM), are proposed for layered composites consisting of anisotropic thermoelastic layers. Of the two models, CM is more important, which is established in the study of periodic layered composites using smoothing operations. CM has the properties: it contains inherently the interface and Floquet conditions and facilitates the analysis of the composite, in particular, when the number of laminae in the composite is large
it contains all kinds of deformation modes of the layered composite
its validity range for frequencies and wave numbers may be enlarged by increasing, respectively, the orders of the theory and interface conditions. CM is assessed by comparing its prediction with the exact for the spectra of harmonic waves propagating in various directions of a two-phase periodic layered composite, as well as, for transient dynamic response of a composite slab induced by waves propagating perpendicular to layering. A good comparison is observed in the results and it is found that the model predicts very well the periodic structure of spectra with passing and stopping bands for harmonic waves propagating perpendicular to layering. In view of the results, the physical significance of Floquet wave number is also discussed in the study.

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Searle, Timothy John. "The manufacture of marine propellers in moulded anisotropic polymer composites". Thesis, University of Plymouth, 1998. http://hdl.handle.net/10026.1/2766.

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This thesis examines the feasibility of manufacturing small marine propellers from continuous fibre reinforced polymer composite materials. An appraisal of some current applications of composite materials in the marine industry is given, together with the moves shown towards the use of composites in the area of propeller design. It has been shown that manufacturing propellers in composite materials is theoretically more cost effective than traditional materials. The manufacturing route investigated is Resin Transfer Moulding, where some detailed investigations have highlighted some of the critical processing parameters necessary for successful production of laminates suitable for propellers and other high performance marine structures. A thorough testing programme of 4 novel designs of composite propeller is reported. Trials at sea on university run vessels has enabled many hours use to be logged, which has shown the fitness for purpose of propellers made from glass reinforced, epoxy composite. Experimental tank testing has helped to shape the remainder of the research by identifying the possibility of using hydroelastic tailoring to improve the efficiency of the propeller when a variety of operating conditions are required from the propulsion system. Further experience is required with respect to the the tooling construction and the life assessment of the propeller. To facilitate appropriate modelling of the propeller, spreadsheet based load prediction models have been used. Finite element analysis (FEA) was used to model the elastic characteristics of one particular design of novel composite propeller. This indicated that traditional geometries may be too stiff to allow significant performance advantages from the anisotropy of the material. However the potential does exist for modified propeller geometries made from composite to give some performance benefit. For specific applications, small marine propellers made from continuous glass fibre reinforced epoxy composite are likely to yield cost savings over traditional propeller materials.

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Belijar, Guillaume. "Anisotropic composite elaboration and modeling : toward materials adapted to systems". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30353/document.

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L'objectif de ces travaux de thèse a été de démontrer la possibilité, en se basant sur une approche prédictive, de contrôler avec précision la fonctionnalisation d'un matériau composite, d'isotrope à anisotrope, sous l'application d'un champ électrique. Ces derniers matériaux présentent en effet un fort potentiel pour des applications futures telles que des condensateurs intégrés ou bien encore des composites conducteurs thermiques. Une première approche théorique des différentes forces et mécanismes entrant en jeux lors de l'élaboration de composites anisotropes par chaînage a permis d'identifier les paramètres impactant le procédé d'élaboration. A la suite de cette étude théorique, un modèle de formation de chaînes de particules sous champ électrique a été développé afin de prédire la dynamique de chaînage. Le modèle choisi (méthode moment dipolaire effectif) a permis la simulation de plus de 4500 particules. Les paramètres ayant au préalable été identifiés ont ensuite été mesurés. Pour la permittivité des particules, une méthode de mesure diélectrophorétique a été développée, ce qui est une première dans le cas de particules céramiques. L'élaboration des composites anisotropes a été couplé avec un suivi novateur, en temps réel, d'un marqueur (permittivité) de la formation de chaînes, permettant d'obtenir la dynamique de structuration des particules. Afin de valider l'aspect prédictif du modèle numérique, une comparaison a été effectuée entre la dynamique mesurée et simulée. Les résultats obtenus ont démontré une très bonne fiabilité des prédictions du modèle, même si des progrès sont encore réalisables aux faibles taux de chargement. Dans un dernier temps, une preuve de concept a été démontrée, de la réalisation de composites anisotropes dont les particules sont alignées perpendiculairement au champ électrique
This study was aimed to demonstrate the possibility, based on a predictive approach, to tailor the structure of a composite from isotropic to anisotropic when applying an electric field. This composites have great potential for future applications such as embed capacitors or thermally conductive composites. A theoretical approach of the forces and mechanisms acting in the elaboration of anisotropic composites by chaining allowed identifying the key parameters. Based on this approach a model of particle chaining under electric field was established to predict the structuration dynamics. This model (effective dipole moment) allowed simulating more than 4500 particles. The parameters previously identified were then measured, and for the particle permittivity, a dielectrophoretic measurement method was developed, which was a first for ceramic particles. The elaboration of anisotropic composites was coupled to a novel on-line monitoring of a chaining marker (permittivity), allowing to obtain the structuration dynamics. To validate the predictive aspect of the model, experimental and numerical dynamics were compared showing the robustness and accuracy of the model, even if improvement is still possible at low filler content. In the last part, a proof of concept was demonstrated of the elaboration of anisotropic composites with fillers oriented normally to the direction of the electric field

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Mais fontes

Livros sobre o assunto "Variable and anisotropic composites"

Freger, G. E., V. N. Kestelman e D. G. Freger. Spirally Anisotropic Composites. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9.

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Freger, G. E. Spirally Anisotropic Composites. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004.

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Robinson, David N. A hydrostatic stress-dependent anisotropic model of viscoplasticity. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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Q, Tao, Verrilli M. J e United States. National Aeronautics and Space Administration., eds. A hydrostatic stress-dependent anisotropic model of viscoplasticity. [Washington, DC]: National Aeronautics and Space Administration, 1994.

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Nayfeh, Adnan H. Wave propagation in layered anisotropic media: With applications to composites. Amsterdam: Elsevier, 1995.

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F, Knight Norman, Ambur Damodar R e United States. National Aeronautics and Space Administration., eds. Buckling analysis of anisotropic curved panels and shells with variable curvature. [Washington, D.C: National Aeronautics and Space Administration, 1998.

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M, Arnold S., Al-Zoubi Nasser R e NASA Glenn Research Center, eds. A study of time-dependent and anisotropic effects on the deformation response of two flywheel designs. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2003.

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Saleeb, Atef F. A study of time-dependent and anisotropic effects on the deformation response of two flywheel designs. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2003.

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Capítulos de livros sobre o assunto "Variable and anisotropic composites"

Hwu, Chyanbin. "Complex Variable Formalism". In Anisotropic Elasticity with Matlab, 21–63. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66676-7_2.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Hybridization and Spatial Reinforcement of Composite Materials". In Spirally Anisotropic Composites, 1–26. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_1.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "General Conclusions and Recommendations". In Spirally Anisotropic Composites, 287–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_10.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Major Principles of Developing Material Structures with Hybrid Spirally Reinforced Filler". In Spirally Anisotropic Composites, 27–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_2.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Stress-Strain State in Composites Based on Hybrid Spirally Reinforced Fillers Under Transverse Loading". In Spirally Anisotropic Composites, 61–113. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_3.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Stress-Strain State of the Composite Based on Spirally Reinforced Filler Under Loading in the Direction of Reinforcement". In Spirally Anisotropic Composites, 115–39. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_4.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Description of Production Technology and Physico-Mechanical Properties of Composites Based on Spirally Reinforced Fillers". In Spirally Anisotropic Composites, 141–94. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_5.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Design of Composite Spirally Reinforced Rods". In Spirally Anisotropic Composites, 195–217. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_6.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "The Effect of Structural and Geometrical Parameters on Rod Properties". In Spirally Anisotropic Composites, 219–42. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_7.

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Freger, G. E., V. N. Kestelman e D. G. Freger. "Optimal Design of Hybrid Spirally Reinforced Rods". In Spirally Anisotropic Composites, 243–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-09975-9_8.

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Trabalhos de conferências sobre o assunto "Variable and anisotropic composites"

Shen, Zikui, Yanpeng Hao, Meng Zhou, Zhidong Jia, Jun Wang, Dongyuan Du, Fengzhen Zhang e Wei Liang. "Electric Field-assisted Preparation of Anisotropic BNNw/SiR Composites for Thermal Management". In 2024 IEEE 5th International Conference on Dielectrics (ICD), 1–4. IEEE, 2024. http://dx.doi.org/10.1109/icd59037.2024.10613286.

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Zhou, Yuqing, Tsuyoshi Nomura, Enpei Zhao, Wei Zhang e Kazuhiro Saitou. "Large-Scale Three-Dimensional Anisotropic Topology Optimization of Variable-Axial Composite Structures". In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22509.

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Abstract Variable-axial fiber-reinforced composites allow for local customization of fiber orientation and thicknesses. Despite their significant potential for performance improvement over the conventional multiaxial composites and metals, they pose challenges in design optimization due to the vastly increased design freedom in material orientations. This paper presents an anisotropic topology optimization (TO) method for designing large-scale, 3D variable-axial composite structures. The computational challenge for large-scale 3D TO with extremely low volume fraction is addressed by a tensor-based representation of 3D orientation that would avoid the 2π periodicity of angular representation such as Eular angles, and an adaptive meshing scheme, which, in conjunction with PDE regularization of the density variables, refines the mesh where structural members appear and coarsens where there is void. The proposed method is applied to designing a heavy-duty drone frame subject to complex multi-loading conditions. Finally, the manufacturability gaps between the optimized design and the fabrication-ready design for Tailored Fiber Placement (TFP) is discussed, which motivates future work toward fully-automated design synthesis.

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He, Ge, Yucheng Liu, D. J. Bammann e M. F. Horstemeyer. "An Elastothermoviscoplasticity Anisotropic Damage Model for Short Fiber Reinforced Polymer Composites". In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86286.

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By using the internal state variable (ISV) theory (Horstemeyer and Bammann, 2010), we developed a finite deformation anisotropic and temperature dependent constitutive model to predict elastoviscoplasticity and progressive damage behavior of short fiber reinforced polymer (SFRP) composites. In this model, the SFRP is considered as a simple anisotropic equivalent medium (lamina), and the rate dependent plastic behavior of the SFRP is captured with the help of three physically-based ISVs. A second-order damage tensor is introduced to describe the anisotropic damage state of the SFRP and the tensorial damage evolution equations are used based on the damage mechanism of micro voids/cracks nucleation, growth and coalescence. The constitutive model developed herein arises employing standard postulates of continuum mechanics with the kinematics, thermodynamics, and kinetics being internally consistent. The developed model is then calibrated to a 35 wt% glass fiber reinforced polyamide 66 (PA66GF-35) for future numerical analyses.

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Garcia, Jordan, Sayer Smith, Brian Sibley e Y. Charles Lu. "Effect of Fiber Content on Anisotropic Behavior of 3D Printed Fiber Composites". In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0071.

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<div class="section abstract"><div class="htmlview paragraph">Discontinuous or short-fiber composites are traditionally less expensive and are normally less difficult to manufacture than continuous fiber composites, while still retaining some of the benefits of reinforcing fibers. Similarly to continuous fibers, the volume ratio influences the mechanical properties of the composite. In addition the ratio of the length and diameter of the reinforcing fibers also plays a significant role. This ratio (also known as the aspect ratio) adds another variable to the anisotropic properties of lamina plies where now not only the content of fibers but also the dimensions of the fibers themselves play a role. Short fiber reinforced composites are already used in additive manufacturing techniques; however, the amount of carbon fiber and the length of the discontinuous strands in the filaments are normally not stated or vary greatly. An investigation in conducted on how the dimensional properties of the carbon fiber, (volume fraction and aspect ratio), affect the mechanical properties of 3D printed parts. Rectangular bending samples were fabricated using a Pulse XE 3D-printer using filament rolls of varying carbon-fiber content and carbon-fiber length. The results showed that the orientation of the reinforcing fibers can play a significant role in the mechanical responses of the final product. The amount of fiber by content also influence how much of a brittle/ductile response the samples exhibited. Additionally the aspect ratio of the carbon-fiber strands appears to influence how susceptible the final products are to artifacts of the 3D-printing process. Finally it is shown how using a combination of the Halpin-Tsai model with Classical-Laminate-Composite-Theory can predict how the samples will respond based on the carbon-fiber content, aspect ratio, and print/fiber orientation. This can theoretically be used to tailor a 3D-printed products anisotropic mechanical properties based on the loading conditions expected by manipulating the reinforcing fibers.</div></div>

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RAHMAN, MINHAZUR, VAMSEE VADLAMUDI e RASSEL RAIHAN. "MECHANICAL AND DIELECTRIC MODELING OF ADHESIVE BONDED FIBER REINFORCED COMPOSITE SINGLE LAP JOINTS". In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36462.

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Fiber Reinforced Polymer (FRP) composites have long since been dominating the structural materials industry due to its superior specific strength and its ability to be designed for desirable mechanical and electrical properties. Using this formidable class of materials as structural components lead to the need of joining and bonding them. Adhesive bonding of composite materials are preferred over conventional mechanical fasteners, rivets, welding etc. as these tend to weaken the structure by introducing additional sources of stress concentrations. However, the complexity from the anisotropy of FRPs and the added convolution of anisotropic (composite adherend) and isotropic (adhesive) interfaces poses significant challenge to properly evaluate and model the adhesive bonded joints of composites. Significant experimental investigations have revealed correlations of material state degradation with the dielectric state variable defined as Dielectric Relaxation Strength (DRS). Due to the lack of appropriately defined physics in commercial simulation software packages, modeling such behaviors were challenging. In this paper a phenomenological modeling approach is taken to simulate the evolution of dielectric properties with the degradation of materials state. Broadband Dielectric Spectroscopy (BbDS) tests were carried out while applying tension on the specimen. The experiment allowed for an in-situ measurement of dielectric property evolution with material state degradation. The experimental data obtained were used to formulate equations relating material’s mechanical properties with dielectric variables such as real and imaginary permittivity. These equations were inserted into the material model as constitutive equations and the evolution of dielectric properties with material degradation were simulated using an 1D Finite Element Analysis (FEA) model.

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Gérard, A., e P. K. Raju. "Optimization of Composites Through Ultrasonic Characterization". In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0212.

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Abstract Composites offer the structural designer a wide choice of properties, geometries and characteristics. Various fibers, matrix materials,’ reinforcement geometries and processing histories may be combined to provide a composite with properties that range from isotropic, low strength and low stiffness materials to highly anisotropic, high strength, and high stiffness materials. These options offer additional variables to the designer that can be used to optimize the configuration of the material and structure simultaneously. This process is presented schematically in Fig. 1. Figure 1. shows a typical design cycle for a composite component.

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Chow, C. L., Fan Yang e H. Eliot Fang. "Crack Initiation in Notched Unidirectional Graphite/Epoxy Composites". In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0668.

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Abstract The paper describes an investigation examining damage responses and failure characteristics of unidirectional graphite/epoxy composites containing a central circular hole subjected to off-axis uniaxial tension. A recently developed damage mechanics model is extended to determine the progressive damage process around the hole and the effect of such damage on the in-plane behaviors and final failure of the notched composites. The generalized stress and strain constitutive equations and the relationship between the damage variable and material properties are briefly outlined first. The anisotropic mechanical behavior of the composites is investigated by using a nonlinear finite element procedure incorporated with the damage-coupled constitutive equations. As the failure of fiber reinforced composite materials may basically be either fiber dominated or matrix dominated, separate damage criteria are proposed to capture fiber failure and matrix or fiber/matrix interaction failure in unidirectional composites. The damage model is validated by comparing the numerical prediction and experimental data obtained from a Moiré interferometry technique. Preliminary results indicate that the proposed damage model provides an effective alternative method to study progressive failure behavior in unidirectional composites.

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Gori, Fabio, Sandra Corasaniti e Jean-François Ciparisse. "Theoretical Prediction of the Anisotropic Effective Thermal Conductivity of Composite Materials". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-86114.

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The composite is made of a matrix and a fiber-reinforced material to form a non-homogeneous anisotropic material. Thermal behaviour of composite materials is very important in many applications as heat shields and heat guides. The present paper investigates theoretically a composite material made of a silica matrix and a fiber reinforcement made of steel. The steady state effective thermal conductivity in the main directions are calculated theoretically for two extreme thermal assumptions, i.e. parallel isothermal lines and parallel heat flux lines. The effective thermal conductivity of the composite is evaluated for a variable thickness of the reinforcement, i.e. for a variable volume fraction. The anisotropy degree, defined as the ratio between the thermal conductivities along the two main directions, increases with the ratio between the thermal conductivities of the reinforcement material and the matrix. The composite material, made of two homogeneous and isotropic materials, is thermally anisotropic and can be used to drive heat towards colder regions. This phenomenon is very useful when a device, such as a spacecraft, must be thermally protected.

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Sakai, J., e Y. H. Park. "Optimum Design of Composite Pressure Vessel Based on 3-Dimensional Failure Criteria". In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93816.

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Abstract Anisotropic composite cylinders and pressure vessels have been widely employed in automotive, aerospace, chemical and other engineering areas due to high strength/stiffness-to-weight ratio, exceptional corrosion resistance, and superb thermal performance. Pipes, fuel tanks, chemical containers, rocket motor cases and aircraft and ship elements are a few examples of structural application of fiber reinforced composites (FRCs) for pressure vessels/pipes. Since the performance of composite materials replies on the tensile and compressive strengths of the fiber directions, the optimum design of composite laminates with varying fiber orientations is desired to minimize the damage of the structure. In this study, a complete mathematical 3D elasticity solution was developed, which can accurately compute stresses of a thick multilayered anisotropic fiber reinforced pressure vessel under force and pressure loadings. A rotational variable is introduced in the formalism to treat torsional loading in addition to force and pressure loadings. Then, the three-dimensional Tsai-Wu criterion is used based on the analytical solution to predict the failure. Finally, a global optimization algorithm is used to find the optimum fiber orientation and their best combination through the thickness direction.

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Nomura, Tsuyoshi, Yoshihiro Iwano, Atsushi Kawamoto, Katsuharu Yoshikawa e Axel Spickenheuer. "Variable Axial Composite Lightweight Automotive Parts Using Anisotropic Topology Optimization and Tailored Fiber Placement". In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2022. http://dx.doi.org/10.4271/2022-01-0344.

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Relatórios de organizações sobre o assunto "Variable and anisotropic composites"

Biswas, Kaushik, Som S. Shrestha, Diana E. Hun e Jerald Atchley. Experimental and numerical evaluations of the energy savings potential of thermally anisotropic composites. Office of Scientific and Technical Information (OSTI), maio de 2019. http://dx.doi.org/10.2172/1515652.

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Malchi, Jonathan Y., e Timothy J. Foley. Development of nano-thermite composites with variable electrostatic discharge ignition thresholds. Office of Scientific and Technical Information (OSTI), novembro de 2007. http://dx.doi.org/10.2172/1454970.

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Wetzel, Kyle K., Thomas M. Hermann e James Locke. Fabrication, testing, and analysis of anisotropic carbon/glass hybrid composites: volume 1: technical report. Office of Scientific and Technical Information (OSTI), novembro de 2005. http://dx.doi.org/10.2172/896281.

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Jury, William A., e David Russo. Characterization of Field-Scale Solute Transport in Spatially Variable Unsaturated Field Soils. United States Department of Agriculture, janeiro de 1994. http://dx.doi.org/10.32747/1994.7568772.bard.

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This report describes activity conducted in several lines of research associated with field-scale water and solute processes. A major effort was put forth developing a stochastic continuum analysis for an important class of problems involving flow of reactive and non reactive chemicals under steady unsaturated flow. The field-scale velocity covariance tensor has been derived from local soil properties and their variability, producing a large-scale description of the medium that embodies all of the local variability in a statistical sense. Special cases of anisotropic medium properties not aligned along the flow direction of spatially variable solute sorption were analysed in detail, revealing a dependence of solute spreading on subtle features of the variability of the medium, such as cross-correlations between sorption and conductivity. A novel method was developed and tested for measuring hydraulic conductivity at the scale of observation through the interpretation of a solute transport outflow curve as a stochastic-convective process. This undertaking provided a host of new K(q) relationships for existing solute experiments and also laid the foundation for future work developing a self-consistent description of flow and transport under these conditions. Numerical codes were developed for calculating K(q) functions for a variety of solute pulse outflow shapes, including lognormal, Fickian, Mobile-Immobile water, and bimodal. Testing of this new approach against conventional methodology was mixed, and agreed most closely when the assumptions of the new method were met. We conclude that this procedure offers a valuable alternative to conventional methods of measuring K(q), particularly when the application of the method is at a scale (e.g. and agricultural field) that is large compared to the common scale at which conventional K(q) devices operate. The same problem was approached from a numerical perspective, by studying the feasibility of inverting a solute outflow signal to yield the hydraulic parameters of the medium that housed the experiment. We found that the inverse problem was solvable under certain conditions, depending on the amount of noise in the signal and the degree of heterogeneity in the medium. A realistic three dimensional model of transient water and solute movement in a heterogeneous medium that contains plant roots was developed and tested. The approach taken was to generate a single realization of this complex flow event, and examine the results to see whether features were present that might be overlooked in less sophisticated model efforts. One such feature revealed is transverse dispersion, which is a critically important component in the development of macrodispersion in the longitudinal direction. The lateral mixing that was observed greatly exceeded that predicted from simpler approaches, suggesting that at least part of the important physics of the mixing process is embedded in the complexity of three dimensional flow. Another important finding was the observation that variability can produce a pseudo-kinetic behavior for solute adsorption, even when the local models used are equilibrium.

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Ziegler, Nancy, Nicholas Webb, Adrian Chappell e Sandra LeGrand. Scale invariance of albedo-based wind friction velocity. Engineer Research and Development Center (U.S.), maio de 2021. http://dx.doi.org/10.21079/11681/40499.

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Obtaining reliable estimates of aerodynamic roughness is necessary to interpret and accurately predict aeolian sediment transport dynamics. However, inherent uncertainties in field measurements and models of surface aerodynamic properties continue to undermine aeolian research, monitoring, and dust modeling. A new relation between aerodynamic shelter and land surface shadow has been established at the wind tunnel scale, enabling the potential for estimates of wind erosion and dust emission to be obtained across scales from albedo data. Here, we compare estimates of wind friction velocity (u*) derived from traditional methods (wind speed profiles) with those derived from the albedo model at two separate scales using bare soil patch (via net radiometers) and landscape (via MODIS 500 m) datasets. Results show that profile-derived estimates of u* are highly variable in anisotropic surface roughness due to changes in wind direction and fetch. Wind speed profiles poorly estimate soil surface (bed) wind friction velocities necessary for aeolian sediment transport research and modeling. Albedo-based estimates of u* at both scales have small variability because the estimate is integrated over a defined, fixed area and resolves the partition of wind momentum be-tween roughness elements and the soil surface. We demonstrate that the wind tunnel-based calibration of albedo for predicting wind friction velocities at the soil surface (us*) is applicable across scales. The albedo-based approach enables consistent and reliable drag partition correction across scales for model and field estimates of us* necessary for wind erosion and dust emission modeling.

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Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density. US Geological Survey, 2001. http://dx.doi.org/10.3133/wri004105.

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