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Bhutta, Salman Ahmed. "Analytical modeling of hybrid composite beams." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020112/.
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Cobb, Ted Quincy Jr. "Optimization of hybrid titanium composite laminates." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19965.
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Raimondi, Luca <1980>. "Theoretical and experimental study of novel hybrid composite and metal-composites interfaces." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10366/1/Tesi%20dottorato%20Luca%20Raimondi_rev1.pdf.
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The growing demand for lightweight solutions in every field of engineering is driving the industry to seek new technological solutions to exploit the full potential of different materials. The combination of dissimilar materials with distinct property ranges embodies a transparent allocation of component functions while allowing an optimal mix of their characteristics. From both technological and design perspectives, the interaction between dissimilar materials can lead to severe defects that compromise a multi-material hybrid component's performance and its structural integrity. This thesis aims to develop methodologies for designing, manufacturing, and monitoring of hybrid metal-composite joints and hybrid composite components. In Chapter 1, a methodology for designing and manufacturing hybrid aluminum/composite co-cured tubes is assessed. In Chapter 2, a full-field methodology for fiber misalignment detection and stiffness prediction for hybrid, long fiber reinforced composite systems is shown and demonstrated. Chapter 3 reports the development of a novel technology for joining short fiber systems and metals in a one-step co-curing process using lattice structures. Chapter 4 is dedicated to a novel analytical framework for the design optimization of two lattice architectures.La crescente domanda di soluzioni alleggerite in ogni campo dell'ingegneria, sta spingendo l'industria a cercare nuove soluzioni tecnologiche per sfruttare il pieno potenziale dei diversi materiali. La combinazione di materiali diversi con gamme di proprietà specifiche racchiude in sé una trasparente ripartizione delle funzioni fra componenti, consentendo al contempo un connubio ottimale delle loro caratteristiche. Sia dal punto di vista della progettazione che del processo, l'interazione tra materiali differenti può portare a gravi difetti che compromettono le prestazioni di un componente, anche nell’integrità strutturale. Questa tesi mira a sviluppare metodologie per la produzione, la progettazione ed il controllo di componenti ibridi metallo-composito e compositi ibridi. Nel Capitolo 1, viene esposta una metodologia per la progettazione e la produzione di tubi ibridi in alluminio/composito co-curati. Nel Capitolo 2, viene mostrata e dimostrata una metodologia full-field per il rilevamento del disallineamento delle fibre e la previsione della rigidezza per sistemi fibrorinforzati a fibra lunga. Il capitolo 3 riporta lo sviluppo di una nuova tecnologia per l'unione compositi a fibra corta e metallo in processo di co-curing, utilizzando lattice structures. Il capitolo 4 è dedicato a un nuovo quadro analitico per l'ottimizzazione del design di due tipologie di lattice structure.
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Forconi, Mattia. "Experimental analysis of a hybrid composite material." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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The main aim of this thesis is to investigate the mechanical properties of a hybrid composite material under static loadings. The material is a composite laminate made by layers of carbon bars and a rubber layer. The thesis can be split into three main parts. In the first part a background about carbon bar composite is given and, subsequently, the research and main results on hybrid composites is introduced. The objective of this section is to provide a base on which built the main results of this work. In the second part it is explained how the test activities have been performed and the main results obtained. In particular, the effect of the introduction
of a rubber layer has been highlighted in each type of tests. In the last part, a finite element dynamical analysis is presented. A very simple transient analysis has been performed in order to foresee the dynamic behaviour of the hybrid. In conclusion, it has been demonstrated a relevant hybrid effect in the compressive and flexural properties. Those effects can be roughly reassumed in anincreasing specific stiffness for the compressive properties and in a large improvement of flexibility in the bending test. The numerical simulation shows that an increased damping effect is present, corresponding to an increase of rubber layer thickness.
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Parkes, Philip. "Metal-composite joining using hybrid penetrative reinforcement." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.667739.
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Leaity, M. A. "Mechanical properties of hybrid-matrix composite laminates." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/843941/.
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A laboratory scale drum winder has been designed and built for the production of pre-preg. Cross-ply hybrid matrix laminates were made from the pre-preg with glass fibres/epoxy resin in the longitudinal plies and glass fibres/epoxy resin-urethane elastomer in the transverse ply. The addition of urethane to the matrix in the transverse plies alone increased the applied strains necessary for the initiation and development of transverse cracking during the extension of cross-ply laminates. This resulted in a smaller reduction in laminate stiffness (due to damage) at a prescribed level of strain. Damage resistance was similar to that in cross-ply laminates with urethane additions to the matrix in both the transverse and longitudinal plies (a uniform matrix laminate). It was found that urethane additions lead to improved damage resistance in cross-ply laminates because they lower the transverse ply modulus and increase the matrix toughness in the transverse ply. During the extension of cross-ply laminates, stable (constrained) transverse cracking was observed in thin transverse plies and unstable (brittle) transverse cracking in thick transverse plies. The effects of urethane additions on the development of constrained transverse cracking and brittle transverse cracking were modelled with a shear lag stress analysis combined with an energy balance and a statistical expression for the transverse ply strength respectively. The ultimate properties of hybrid matrix laminates, having improved damage resistance, were expected to be better than uniform matrix laminates with a similar urethane content in the matrix. However, the tensile strength of circular centre-notched (0,90)s hybrid matrix laminates was lower than uniform matrix counterparts and the compressive strength of (02,902)2s hybrid matrix laminates was similar to uniform matrix counterparts.
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Senne, Jolyn Louise. "Fatigue Life of Hybrid FRP Composite Beams." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33982.
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As fiber reinforced polymer (FRP) structures find application in highway bridge structures, methodologies for describing their long-term performance under service loading will be a necessity for designers. The designer of FRP bridge structures is faced with out-of-plane damage and delamination at ply interfaces. The damage most often occurs between hybrid plys and dominates the life time response of a thick section FRP structure. The focus of this work is on the performance of the 20.3 cm (8 in) pultruded, hybrid double web I-beam structural shape. Experimental four-point bend fatigue results indicate that overall stiffness reduction of the structure is controlled by the degradation of the tensile flange. The loss of stiffness in the tensile flange results in the redistribution of the stresses and strains, until the initiation of failure by delamination in the compression flange. These observations become the basis of the assumptions used to develop an analytical life prediction model. In the model, the tensile flange stiffness is reduced based on coupon test data, and is used to determine the overall strength reduction of the beam in accordance the residual strength life prediction methodology. Delamination initiation is based on the out-of-plane stress sz at the free edge. The stresses are calculated using two different approximations, the Primitive Delamination Model and the Minimization of Complementary Energy. The model successfully describes the onset of delamination prior to fiber failure and suggests that out-of-plane failure controls the life of the structure.Master of Science
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Kim, Dae-Wook. "Machining and drilling of hybrid composite materials /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/7041.
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Phongphinittana, Ekkarin. "Assemblages composites-polymères après traitement par plasma atmosphérique du composite : caractérisation mécaniques et modélisation." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0070.
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A la suite des propositions de la commission européenne, visant à concrétiser les objectifs de réduction des émissions de dioxyde de carbone (CO2) des voitures. Pour atteindre cet objectif, les constructeurs automobiles doivent réduire le poids de la voiture. Ainsi l'équipementier FAURECIA, fabricant de sièges de voiture désire remplacer les structures métalliques par des structures hybrides plastique-métal (PMH). Et en plus, il désire également utiliser un matériau composite en remplacement du métal pour diminuer le poids et utiliser la technique du plasma atmosphérique pour améliore le force d'adhérence à l'interface de pièce structure hybride.C'est dans ce contexte que nous avons étudié des effets de plasma traitement sur l'adhérence dans la structure hybride pour proposer la meilleure condition de traitement. L'objectif de ce travail était de caractériser l'effet de plasma traitement par détermination des paramètres dans le processus de traitement telle que la vitesse de balayage, la distance entre le substrat et la torche plasma et le nombre de passages de la torche, puis de prédire l'initiation du délaminage sous chargement quasi-statiques dans l'éprouvette de simple recouvrement par l'utilisation le critère de la rupture. Un autre objectif était d'étudier les modèle micromécanique pour évaluer la fiabilité de leur. Et ils seront appliqués pour prévoir les comportements mécaniques de matériau thermoplastique renforcé par fibre de verre court. Afin d'atteindre les objectifs présenté, les plusieurs essais telles que l'essai de traction, l'essai simple recouvrement et l'essai de l'ARCAN-Mines sont été réalisé. En parallèle, les techniques de l'émission acoustique (EA), du rayonnement infrarouge (RI) et de la microscopie optique ont été utilisées pour suivre les mécanismes de la rupture de l'éprouvette étudiée. En enfin, la méthode des éléments finis a été utilisé pour simuler les essais et pour permettre de vérifier la fiabilité du critère de ruptureFollowing the proposals of the European Commission, to achieve the goals of emission reduction of carbon dioxide (CO2) from cars. To achieve this objective, automakers must reduce the weight of the car. Thus the supplier Faurecia, manufacturer of car seats desires to replace metal structures by structure plastic-metal hybrid (PMH). And they desire also to use a composite material to replace metal in order to reduce weight. Moreover in order to improve the adhesion strength at the interface piece hybrid structure,Atmospheric plasma technique was used.In this context, we studied the effects of plasma treatment on term of adhesion in the hybrid structure in order to provide the best condition of treatment. The objective of this study was to characterize the effect of plasma treatment by determination at the parameters in the process such as the scanning speed, the distance between the substrate and the plasma torch and the number of passes of the torch, then to predict the initiation of delamination under quasi-static loading test in specimen of single lap shear by using the criterion of rupture. The other objective was to study the micromechanical model to assess the reliability of them. And they will be applied to predict the mechanical behavior of Short Glass Fiber reinforced thermoplastic. In order to achieve the objectives presented, the several tests such as tensile test, single lap shear test and ARCAN-Mines test have been executed. In parallel, techniques acoustic emission (AE), infrared radiation (IR) and optical microscopy were used in order to follow the failure mechanisms of the specimen studied. Finally, the finite element method was used to simulate the tests and allow to verify the reliability of the failure criterion
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Ming, Jin Martin. "High velocity impact studies on hybrid composite structures." Thesis, University of Portsmouth, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500334.
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Composite structural elements are now used in a variety of components for automotive, aerospace, marine, and architectural structures. The impact resistance of the materials is an important area of research. Fibre reinforced polymer (FRP) structures typically respond poorly to transverse impact events. In addition, uncertainties about the mechanics of damage make it difficult to ascertain the effect of an impact event on the performance of a FRP structure. Compounding these considerations is the fact that, in some cases, the damage will not be visible which could lead to components with considerable damage being allowed to continue in service: a hidden menace. In these series of studies, tests were conducted with an instrumented drop weight impact, an air gun system was developed and a numerical transient analysis conducted on composite plate to understand the loading distribution as a result of impact.
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Liu, Xiao Bin. "Finite element analysis of hybrid thermoplastic composite structures." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493330.
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A wide range of thermoplastic composites (TPC) are now being used in automotive applications including vehicle front-end structures, load floors, seat backs, door cassettes and instrument panels. Long fibre thermoplastics (LFT), glass mat thermoplastics (GMT) and fully structural materials such as woven commingled fabric TPCs, e.g. Twintex®, provide a range of properties and mouldability appropriate to specific applications.
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Slemp, Wesley Campbell Hop. "Integrated Sinc Method for Composite and Hybrid Structures." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77111.
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Composite materials and hybrid materials such as fiber-metal laminates, and functionally graded materials are increasingly common in application in aerospace structures. However, adhesive bonding of dissimilar materials makes these materials susceptible to delamination. The use of integrated Sinc methods for predicting interlaminar failure in laminated composites and hybrid material systems was examined. Because the Sinc methods first approximate the highest-order derivative in the governing equation, the in-plane derivatives of in-plane strain needed to obtain interlaminar stresses by integration of the equilibrium equations of 3D elasticity are known without post-processing. Interlaminar stresses obtained with the Sinc method based on Interpolation of Highest derivative were compared for the first-order and third-order shear deformable theories, the refined zigzag beam theory and the higher-order shear and normal deformable beam theory. The results indicate that the interlaminar stresses by the zigzag theory compare well with those obtained by a 3D finite element analysis, while the traditional equivalent single layer theories perform well for some laminates.
The philosophy of the Sinc method based on Interpolation of Highest Derivative was extended to create a novel weak form based approach called the Integrated Local Petrov-Galerkin Sinc Method. The Integrated Local Petrov-Galerkin Sinc Method is easily utilized for boundary-value problem on non-rectangular domains as demonstrated for analysis of elastic and elastic-plastic plane-stress panels with elliptical notches. The numerical results showed excellent accuracy compared to similar results obtained with the finite element method.
The Integrated Local Petrov-Galerkin Sinc Method was used to analyze interlaminar debonding of composite and fiber-metal laminated beams. A double-cantilever beam and a fixed-ratio mixed mode beam were analyzed using the Integrated Local Petrov-Galerkin Sinc Method and the results were shown to correlate well with those by the finite element method. An adaptive Sinc point distribution technique was implemented for the delamination analysis which significantly improved the methods accuracy for the present problem. Delamination of a GLARE, plane-strain specimen was also analyzed using the Integrated Local Petrov-Galerkin Sinc Method. The results correlate well with 2D, plane-strain analysis by the finite element method, including interlaminar stresses obtained by through-the-thickness integration of the equilibrium equations of 3D elasticity.Ph. D.
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Al-Majali, Yahya T. "Novel Hybrid Composite Discharge Electrode for Electrostatic Precipitator." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1492188040079733.
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Sun, Mingkun Sun. "MULTISCALE HYBRID ELEMENT MODELING OF TRIAXIAL BRAIDED COMPOSITE." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533550804106857.
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Rhymer, Donald William. "Fatigue damage mechanisms of advanced hybrid titanium composite laminates." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18980.
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Gautam, Mayank. "Hybrid composite wires for tensile armour in flexible risers." Thesis, University of Manchester, 2001. https://www.research.manchester.ac.uk/portal/en/theses/hybrid-composite-wires-for-tensile-armour-in-flexible-risers(c5adfc24-9a23-40ab-a038-dba352df6fc4).html.
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Flexible risers that carry hydrocarbon fuels from the subsea facilities to the floatation units above the sea surface are composed of multiple metallic and polymeric layers (in their wall). Among these layers, the tensile armour layer consists of several helically wound metallic wires; these tensile armour layers carry the weight of the riser, provide tensile stiffness & strength and maintain the structural integrity of the riser structure during harsh underwater currents. However, as the oil & gas fields in shallow waters are receding, the oil & gas industry is being forced to move towards deeper offshore waters, where the metallic tensile armour wires pose limitations (fatigue, corrosion, weight, etc.). In this thesis an alternative to metallic tensile armour wires will be presented in form of a flexible hybrid composite formed by stacking seven pultruded composite (carbon and vinyl-ester) circular rods in form of hexagonal pack, held together by an over-braid (Dyneema fibres) sleeve. The manufacturing process for hybrid composite tensile armour wires will be studied and their mechanical properties will be presented. A multi-scale finite element model developed for hybrid composite wires will be presented in this thesis to help further understand the mechanical properties of hybrid composite wires.
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Paine, Jeffrey S. "Multi-functional SMA hybrid composite materials and their applications." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38219.
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Shape memory alloy (SMA) materials such as nitinol have unique properties associated with the shape recovery effect and the material’s phase changes that have been used in a variety of actuator and sensing applications. By embedding SMA elements into host composite materials, control or modification of the SMA hybrid composite’s structural properties can be accomplished inservice, thereby increasing the hybrid composite’s structural functionality. Previous studies addressed increasing composite materials’ functionality by enabling in-service control of their dynamic response. Utilizing the SMA’s substantial recovery stress and capacity to dissipate strain energy to increase the hybrid composite’s static functionality is addressed herein. Specific applications for SMA hybrid composites include improving composite material’s impact damage resistance and composite cylinder stress and deflection control.
In stress and deflection control of cylindrical structures, SMA actuators are placed within the composite cylinder to form an active compound cylinder. The active SMA elements can significantly reduce the internal pressure-induced radial dilation and creep so that under severe loading, piston to cylinder tolerances may be maintained. Similar to a conventional metallic compound cylinder, the active compound cylinder also reduces peak cylinder hoop stresses. Hybridizing composites with nitinol improves their impact resistance because of nitinol’s tremendous capacity to absorb impact strain energy through the stress-induced martensitic phase transformation. The amount of impact damage is reduced and the material’s resistance to impact perforation at various velocities is improved. The experimental response of nitinol hybrid composites and the associated mechanics are presented. The unique toughness and resistance to permanent deformation that is a result of the stress-induced martensitic phase transformation enables the nitinol to absorb on the order of 4 times the strain energy of high alloy steel and 16 times that of many graphite/epoxy composites.
In most static applications where SMA elements are used for reinforcement, maintaining the integrity of the interface between the SMA elements and the host polymeric matrix composite material is critical to operation. The relationship between preparation of SMA elements for hybrid composite fabrication and interfacial bond strength is presented to address this issue. The mechanics of interfacial shear failure between SMA element and composite is also presented.Ph. D.
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Van, Nosdall Stephen Paul. "Experiments on a Hybrid Composite Beam for Bridge Applications." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23106.
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This thesis details a study of the structural behavior of Hybrid-Composite Beams (HCB) consisting of a fiber reinforced polymer (FRP) shell with a concrete arch tied with steel prestressing strands. The HCB offers advantages in life cycle costs through reduced transportation weight and increased corrosion resistance. By better understanding the system behavior, the proportion of load in each component can be determined, and each component can be designed for the appropriate forces. A long term outcome of this research will be a general structural analysis framework that can be used by DOTs to design HCBs as rapidly constructible bridge components. This study focuses on identifying the load paths and load sharing between the arch and FRP shell. Testing was performed by applying point loads on simple span beams (before placing the bridge deck) and a three beam skewed composite bridge system. Curvature from strain data is used to find internal bending forces, and the proportion of load within the arch is found. Additionally, a stress integration method is used to confirm the internal force contributions. The tied arch carries about 80% of the total load for the non-composite case without a bridge deck. When composite with a bridge deck, the arch has a minimal contribution to the HCB stiffness and strength as it is below the neutral axis. For this composite case the FRP shell and prestressing strands resist about 85% of the applied load while the bridge deck carries the remaining 15% to the end diaphragms and bearings.
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Prasad, Hanasoge Saraswathi Deepthi. "Bearing strength and failure behavior of hybrid composite laminates." Thesis, Linköpings universitet, Konstruktionsmaterial, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170914.
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Composite layups have been continuously used over many years in various applications. It is necessary to optimize its composition by studying various parameters influencing the mechanical properties and studying the failure behavior. In this master thesis, the objective was to test five different plies manufactured using thick and thin plies and various combinations of thick and thin laminates called hybrid laminates. Bearing tests are performed for five layups with each layer has its thickness varying from 40μm to 130μm, and a combination called hybrid laminate, and the results from the tests are investigated. The resulting system has a good performance with onset damage above 700 MPa and an ultimate failure above 1130 MPa, using fibers' full potential. Also, the different failure modes like fiber kinking, matrix crack, delamination, and their effect on the layup's strength are investigated using fractography. This paper also investigates the influences of the thickness of the laminate on the strength of hybrid composites jointed using different mechanisms, and its failure modes are checked. Results from this experiment are used to validate in the form of FEM model, which is a part of an internal project at RISE SICOMP AB. This thesis is suitable for an engineering student in mechanical engineering, material science interested in composite materials and fractography.
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Paine, Jeffrey Steven Nelson. "Multi-functional SMA hybrid composite materials and their applications /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-162936/.
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Reiniati, Isabela. "Chemical, physical, and viscoelastic properties of hotpressed hybrid poplar." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/i_reiniati_061209.pdf.
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Thesis (M.S. in chemical engineering)--Washington State University, August 2009.Title from PDF title page (viewed on July 15, 2009). "School of Chemical Engineering and Bioengineering." Includes bibliographical references.
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Horton, Brandon Alexander. "Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/93961.
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In recent years, the prevalence and application of composite materials has exploded. Due to the demands of commercial transportation, the aviation industry has taken a leading role in the integration of composite structures. Among the leading concepts to develop lighter, more fuel-efficient commercial transport is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The highly integrated structure of PRSEUS allows pressurized, non-circular fuselage designs to be implemented, enabling the feasibility of Hybrid Wing Body (HWB) aircraft. In addition to its unique fabrication process, the through-thickness stitching utilized by PRSEUS overcomes the low post-damage strength present in typical composites. Although many proof-of-concept tests have been performed that demonstrate the potential for PRSEUS, efficient computational tools must be developed before the concept can be commercially certified and implemented.
In an attempt to address this need, a comprehensive modeling approach is developed that investigates PRSEUS at multiple scales. The majority of available experiments for comparison have been conducted at the coupon level. Therefore, a computational methodology is progressively developed based on physically realistic concepts without the use of tuning parameters. A thorough verification study is performed to identify the most effective approach to model PRSEUS, including the effect of element type, boundary conditions, bonding properties, and model fidelity. Using the results of this baseline study, a high fidelity stringer model is created at the component scale and validated against the existing experiments. Finally, the validated model is extended to larger scales to compare PRSEUS to the current state-of-the-art.
Throughout the current work, the developed methodology is demonstrated to make accurate predictions that are well beyond the capability of existing predictive models. While using commercially available predictive tools, the methodology developed herein can accurately predict local behavior up to and beyond failure for stitched structures such as PRSEUS for the first time. Additionally, by extending the methodology to a large scale fuselage section drop scenario, the dynamic behavior of PRSEUS was investigated for the first time. With the predictive capabilities and unique insight provided, the work herein may serve to benefit future iteration of PRSEUS as well as certification by analysis efforts for future airframe development.PHD
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van, Dijken Jan W. V. "Conventional, microfilled and hybrid composite resins : laboratory and clinical evaluations." Doctoral thesis, Umeå universitet, Kardiologi, 1987. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100590.
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Three types of composite resins, classified as conventional, microfilled and hybrid resins were compared with respect to surface characteristics, effect on the gingival margin, marginal adaptation and clinical durability in anterior cavities. The surface characteristics were studied in in vitro systems by means of scanning electron microscopy. Fillings prepared in vivo were evaluated regarding surface characteristics, marginal conditions, color stability and the effect on the development of gingivitis and caries. Microfilled resins were superior to the conventional and hybrid composites with regard to the possibility of obtaining and retaining a smooth surface. The number of porosities varied greatly between the composites investigated and could not be related to the type or curing method used in their manufacture. Marginal defects in the form of chip fractures and fractures in the resin parallel to the resin/enamel border were seen more frequently in the microfilled composite fillings than in the conventional and hybrid resins. The severity of the defects increased with time. There was a great variation in clinical behaviour within each resin group. The difference in surface characteristics between the three composites did not result in clinically measurable differences in amount of plaque on and degree of gingivitis around the composite fillings neither during a period of normal home care nor during an experimental gingivitis period. Recurrent caries was the major single reason for replacement. Patients with a greater number of caries risk factors clearly showed a higher caries increment, especially around composite fillings. The shortcomings of the three composite resin types indicate that no material as yet meets the demands of an all purpose material.Diss. (sammanfattning) Umeå : Umeå universitet, 1987, härtill 7 uppsatser.
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Sarh, Bastian. "A novel hybrid joining methodology for composite to steel joints /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3205377.
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Tsang, Terry Kin Chung. "Behaviour of concrete beams reinforced with hybrid FRP composite rebars /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20TSANGT.
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Ku, Jieun. "A Hybrid Optimization Scheme for Helicopters with Composite Rotor Blades." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16268.
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Rotorcraft optimization is a challenging problem due to its conflicting requirements among many disciplines and highly coupled design variables affecting the overall design. Also, the design
process for a composite rotor blade is often ambiguous because of its design space. Furthermore, analytical tools do not produce
acceptable results compared with flight test when it comes to aerodynamics and aeroelasticity unless realistic models are used, which leads to excessive computer time per iteration.
To comply these requirements, computationally efficient yet realistic tools for rotorcraft analysis, such as VABS and DYMORE were used as analysis tools. These tools decompose a three-dimensional problem into a two-dimensional cross-sectional and a one-dimensional beam analysis. Also, to eliminate the human interaction between iterations, a previously VABS-ANSYS macro was
modified and automated. The automated tool shortened the computer time needed to generate the VABS input file for each analysis from
hours to seconds. MATLAB was used as the wrapper tool to integrate VABS, DYMORE and the VABS-ANSYS macro into the methodology. This methodology uses Genetic Algorithm and gradient-based methods as
optimization schemes. The baseline model is the rotor system of generic Georgia Tech Helicopter (GTH), which is a three-bladed, soft-in-plane, bearingless rotor system. The resulting methodology is a two-level optimization, global and local. Previous studies showed that when stiffnesses are used as design variables in
optimization, these values act as if they are independent and produce design requirements that cannot be achieved by local-level optimization. To force design variables at the global level to stay within the feasible design space of the local level, a surrogate model was adapted into the methodology. For the surrogate model,
different ``design of experiments" (DOE) methods were tested to find the most computationally efficient DOE method. The response surface
method (RSM) and Kriging were tested for the optimization problem.
The results show that using the surrogate model speeds up the optimization process and the Kriging model shows superior performance over RSM models. As a result, the global-level optimizer
produces requirements that the local optimizer can achieve.
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Anders, William S. "Structural acoustic analysis of shape memory alloy hybrid composite panels." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11012008-063243/.
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Photiou, Nikolaos K. "Rehabilitation of steel members utilising hybrid FRP composite material systems." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/634/.
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CAVACO, MARCO ANTONIO MARTINS. "AN HYBRID METHOD FOR PHOTOELASTIC ANALYSIS OF ORTHOTROPIC COMPOSITE MATERIALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1990. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20636@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta uma nova técnica para análise de tensões em modelos fotoelásticos planos. Essa técnica baseia-se na determinação de coeficientes para funções de tensão aproximadas, através da coleta dos dados extraídos de ordens de franjas isocromáticas e de condições de contorno de modelos fotoelásticos planos. O modelo tem como vantagens a determinação de fatores de concentração de tensões com boa precisão, além de permitir a separação de tensões em pequenas ou grandes regiões de modelos fotoelásticos planos, sem requerer a leitura de franjas isoclínicas. Uma outra grande vantagem está na possibilidade imediata de acoplamento desse método com um analisador de imagens para determinação automática de Kt. Foram encontrados excelentes resultados em problemas onde haviam concentradores de tensão e no estudo de regiões próximas a cargas concentradas. A determinação dos coeficientes das funções foi feita através de um programa escrito em BASIC, que utiliza o método de Newton-Raphson em conjunto com o ajuste dos dados por mínimos quadrados. Vários exemplos foram estudados com o objetivo de avaliar sua performance. Entre eles estão: carga concentrada sobre uma superfície semi-infinita; placa infinita e finita com futo circular sujeita à tração; disco circular submetidos à cargas diametrais compressivas; viga reta carregada à tração constante e a momento constante; e barra com duplo entalhe em U submetida a momento constante.
This work presents a new technique for improving stress analysis in photoelastic plane models. This technique is based on the determination of coefficients of approximated stress functions through the collection of isochromatic fringe data, and by the applications of boundary conditions to photoelastic plane models. The technique has as advantages the accurate determination of stress concentration factors and the stress without the need for collecting isoclinic fringe data. Another great advantage, is the immediate use of this method coupled with an image analyzer device for automatic extraction of Kt. Excellent results were found in problems where stress concentration or concentrated loading were present. The coefficients of the stress functions were determined by a BASIC program, using a Newton-Raphson technique coupled to a least square algorithm. Many example were tested to evaluate its performance. Among them are: concentrated force at a point of a straight boundary; infinite and finite plate with circular holes subjected to uniaxial tensile loads; circular disk under compressive diametral forces; bar subjected to pure tensile and pure bending loads; and a double U-notched bar under pure bending.
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CASTRO, LUIZ OTAVIO GUERREIRO DE. "AN HYBRID METHOD FOR PHOTOELASTIC ANALYSIS OF ORTHOTROPIC COMPOSITE MATERIALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1992. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24947@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
Este trabalho tem como finalidade a apresentação de um método novo e eficiente para a análise e separação de tensões em materiais compostos (conjugados). O método híbrido consiste no acoplamento da lei ótica para materiais ortotrópicos com as equações de compatibilidade e equilíbrio para corpos anisotrópicos. As soluções destas equações são representadas por funções analíticas de variáveis complexas. O método propõe que se aproximem as funções analíticas por funções polinomiais. Estas funções aproximadas são determinadas através do acoplamento das equações de equilíbrio e compatibilidade com dados experimentais, obtidos da resposta fotoelástica, e com métodos numéricos (Newton-Raphson e mínimos quadrados), possibilitando a determinação dos coeficientes integrantes das funções polinomiais. O método apresenta como principal vantagem a capacidade de separar as tensões, com precisão, em pequenas ou mesmo em grandes regiões de modelos fotoelásticos planos, sem requerer a leitura de franjas isoclínicas. São apresentados excelentes resultados obtidos com a aplicação do método desenvolvido em alguns casos específicos, envolvendo um material composto por uma matriz de resina reforçada por fibras de vidro com arranjo unidirecional. Três casos são objetos de estudo: A) Barra retangular submetida à tração, com a direção do reforço paralela a direção da carga aplicada. B) Barra retangular submetida à tração. com direção do reforço fazendo um ângulo qualquer com a direção da carga aplicada. C) Plano semi-infinito submetido à carga concentrada atuando perpendicularmente à direção do reforço.
The objective of this paper is to present a new and efficient method to analyse and separate stresses in composite materials. The hybrid method associates the stress-optic law for orthotropic materials with the compatibility and equlibrium equations for anisotropic bodies. The solutions of these equatios are represented by analytical functions of complex variables. The method proposes that these analytical functions be approximate by polynomial functions. These aapproximate functions are determined by the association of the compatibility equilibrium equatios with experimental data (obtained from the photoelastic response) and numerical methods (Newton-Raphson and least squares method). The method presents as a major advantage the capacity to separate stresses precisely in small or even in large regions of photoelastic plane models, without needign to collect isoclinic fringe data. The thesis presents excellent results obtained by the application of the developed method in some specific cases, where a fiber glass reinforced epoxy resin is used as a model material, will be shown. Three cases are studied: A) Rectangular bar in tension with the fiber reinforcement axis parallel to the applied load direction B) Rectangular bar in tension with the fiber reinforcement axis making a known angle with the applied load direction C) Semi-infinite plane subjected to a concentrated edge load which is perpendicular to the fiber reinforcement axis.
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Jia, Hongyu. "Impact Damage Resistance of Shape Memory Alloy Hybrid Composite Structures." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30572.
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The strain energy absorption of shape memory alloy (SMA) bars and beams under tension and bending loading was studied. A theoretical model is presented that can give quantitative relations between the martensite fraction, the applied load, and the strain energy absorbed in the shape memory alloy (SMA). It was found analytically that the super-elastic SMA demonstrates a high strain energy absorption capability. The closed- form solution of the strain energy absorption capability of SMA bars is a simple and useful tool in the design of energy absorption applications of super-elastic SMA. The nonlinear equations for SMA hybrid composite plates, which can be used for low velocity impact or quasi-static contact loading, are derived. The governing equations include the transverse shear deformation to the first-order, large deformation of the plates, and SMA/epoxy lamina. The equations are derived in the general form with general boundary conditions and general stack of angle ply. The equations can be simplified to special forms in the specific applications.
A theoretical study of the impact force and the strain energy absorption of an SMA/graphite/epoxy composite beam under a low-velocity impact has been performed. The contact deformation, the global bending deformation, the transverse shear deformation, and the martensitic phase transformation of the super-elastic SMA fibers are studied. The energy absorbed by the SMA hybrid composite is calculated for each task of the absorption mechanisms: contact deformation, global bending deformation, and The analysis methods and models developed in this dissertation are the first reported research in modeling SMA composite under low velocity impact and quasi-static loading. The models and methods developed here can be used for further study and design of SMA composites for low velocity impact or quasi-static loading in failure process.Ph. D.
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Dijken, Jan W. V. van. "Conventional, microfilled and hybrid composite resins laboratory and clinical evaluations /." Umeå : [s.n.], 1987. http://books.google.com/books?id=NnBqAAAAMAAJ.
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Zhang, Rui. "Transition-metal-based composite and hybrid nanomaterials for catalytic applications." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19224.
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In der Entwicklung von Technologien für die nachhaltige Erzeugung, Speicherung und Umwandlung von Energie werden Hochleistungskatalysatoren benötigt. Im Rahmen dieser Arbeit werden verschiedene Übergangsmetall-basierte Katalysatoren, namentlich TiO2/Kohlenstoff-Komposite, anorganisch-organische Hybridsysteme auf Basis von NiFe Phosphonaten sowie Ni Phosphide, synthetisiert, charakterisiert und hinsichtlich ihrer photo- und elektrokatalytischen Eigenschaften untersucht.
Es wird gezeigt, dass die Grenzflächeneigenschaften der TiO2/C-Komposite signifikant durch die Gestaltung des Heizvorgangs während der Synthese beeinflusst werden. Insbesondere der Einsatz von Mikrowellenstrahlung vermag die Synthese von Kohlenstoff-basierten Materialien positiv zu beeinflussen. Schnelles Erwärmen führt zu stärkeren Wechselwirkungen zwischen Nanopartikeln und Kohlenstoff, einheitlicheren Beschichtungen und kleineren Partikeln mit schmaleren Partikelgrößenverteilungen, wodurch die photokatalytische Aktivität verbessert wird.
Schichtartige, hybride NiFe-Phenylphosphonat-Materialien werden ausgehend in Benzylalkohol dargestellt und ihre Aktivität in der OER im basischen Milieu untersucht. Die Hybridpartikel werden in-situ in NiFe-Hydroxid Nanoschichten umgewandelt. Röntgenspektroskopische Untersuchungen deuten auf eine induzierte, teilweise verzerrte Koordinationsumgebung der Metallzentren im Katalysator hin. Die Kombination der synergistischen Effekte zwischen Ni und Fe mit den strukturellen Eigenschaften des Hybridmaterials ermöglicht einen effizienten Katalysator.
Weiterhin werden Nickel-Phosphide durch die thermische Behandlung der Phenyl- oder Methylphosphonate des Nickels, welche Schichtstrukturen aufweisen, in H2(5%)/Ar-Atmosphäre synthetisiert. Ni12P5, Ni12P5-Ni2P und Ni2P Nanopartikel, die mit einer dünnen Schicht aus Kohlenstoffmaterial beschichtet sind, werden erhalten. Ni12P5-Ni2P und Ni2P Nanopartikel katalysieren die Wasserstoffentwicklungsreaktion (HER) im Sauren effektiv.High-performance catalysts play a key role in the development of technologies for sustainable production, storage, and conversion of energy. In this thesis, transition-metal-based catalysts, including TiO2/carbon composites, hybrid organic-inorganic NiFe phosphonates, and Ni phosphides are synthesized, characterized, and investigated in photocatalytic or electrocatalytic reactions. TiO2 is frequently combined with carbon materials, such as reduced graphene oxide (rGO), to produce composites with improved properties. TiO2 is more efficiently stabilized at the surface of rGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance. Layered hybrid NiFe-phenylphosphonate compounds are synthesized in benzyl alcohol, and their oxygen evolution reaction (OER) performance in alkaline medium is investigated. The hybrid particles transformed in situ into NiFe hydroxide nanosheets. X-ray absorption spectroscopy measurements suggest the metal sites in the active catalyst inherited partly the distorted coordination. The combination of the synergistic effect between Ni and Fe with the structural properties of the hybrid results in an efficient catalyst that generates a current density of 10 mA cm-2 at an overpotential of 240 mV. Moreover, nickel phosphides are synthesized through thermal treatment under H2(5%)/Ar of layered nickel phenyl- or methylphosphonates that act as single-source precursors. Ni12P5, Ni12P5-Ni2P and Ni2P nanoparticles coated with a thin shell of carbonaceous material are produced. Ni12P5-Ni2P and Ni2P NPs efficiently catalyze the hydrogen evolution reaction (HER) in acidic medium. Co2P and CoP NPs are also synthesized following this method.
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Kapidzic, Zlatan. "Strength analysis and modeling of hybrid composite-aluminum aircraft structures." Licentiate thesis, Linköpings universitet, Hållfasthetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91894.
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The current trend in aircraft design is to increase the proportion of fiber composites in the structures. Since many primary parts also are constructed using metals, the number of hybrid metal-composite structures is increasing. Such structures have traditionally often been avoided as an option because of the lack of methodology to handle the mismatch between the material properties. Composite and metal properties differ with respect to: thermal expansion, failure mechanisms, plasticity, sensitivity to load type, fatigue accumulation and scatter, impact resistance and residual strength, anisotropy, environmental sensitivity, density etc. Based on these differences, the materials are subject to different design and certification requirements. The issues that arise in certification of hybrid structures are: thermally induced loads, multiplicity of failure modes, damage tolerance, buckling and permanent deformations, material property scatter, significant load states etc. From the design point of view, it is a challenge to construct a weight optimal hybrid structure with the right material in the right place. With a growing number of hybrid structures, these problems need to be addressed. The purpose of the current research is to assess the strength, durability and thermo-mechanical behavior of a hybrid composite-aluminum wing structure by testing and analysis. The work performed in this thesis focuses on the analysis part of the research and is divided into two parts. In the first part, the theoretical framework and the background are outlined.Significant material properties, aircraft certification aspects and the modeling framework are discussed.In the second part, two papers are appended. In the first paper, the interaction of composite and aluminum, and their requirements profiles,is examined in conceptual studies of the wing structure. The influence of the hybrid structure constitution and requirement profiles on the mass, strength, fatigue durability, stability and thermo-mechanical behavior is considered. Based on the conceptual studies, a hybrid concept to be used in the subsequent structural testing is chosen. The second paper focuses on the virtual testing of the wing structure. In particular, the local behavior of hybrid fastener joints is modeled in detail usingthe finite element method, and the result is then incorporated into a global model using line elements. Damage accumulation and failure behavior of the composite material are given special attention. Computations of progressive fastener failure in the experimental setup are performed. The analysis results indicate the critical features of the hybrid wing structure from static, fatigue, damage tolerance and thermo-mechanical points of view.
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Case, Amelia Ann. "Permeability of Hybrid Composites Subjected to Extreme Thermal Cycling and Low-Velocity Impacts." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4956.
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The next generation of space launch vehicles would like to utilize composite materials for both fuel tanks and fuel feedlines in an effort to reduce the overall vehicle weight, which in turn, increases the weight of payload that can be sent into orbit. These polymer matrix composites are subjected to extreme thermal cycles and are vulnerable to impacts, both of which can cause the composite to leak thru micro-cracks in the matrix material, jeopardizing the performance and safety of the vehicle. A reusable launch vehicle's composite fuel tanks are cycled from -253℃(cryogenic fuel temperature) to 127℃(reentry), which can cause matrix micro-cracking due to the thermal mismatch between the fibers and the matrix. These fuel tanks and feedlines are also vulnerable to low velocity impacts, such as those due to dropped tools and inadvertent bumping during installation and maintenance, which can also cause matrix micro-cracking.
The main objective of this research was to develop hybrid polymer matrix composites that are able to withstand applications of extreme temperature fluctuations and moderate impacts while retaining structural integrity (i.e. low permeability and adequate load carrying capacity). Specifically, this research investigated the effects of the addition of a 'barrieer'layer, embedded during manufacture, on a PMCs permeability after thermal cycling and low velocity impact events. The baseline composite material was an eight ply IM7/977-2 epoxy system. Barrier layer candidates include a nano-clay reinforced epoxy, aluminized Mylar, aluminum foil, and two т-Ti 15-3 films. Thermal cycling was performed on the hybrid composites to simulate the extreme temperatures experienced by the cryotanks and to determine if the interleaved composites exhibited reduced permeability after thermal cycling. Drop-weight impact tests were performed to determine the effect of interleaving on the critical impact energy of the graphite/epoxy composites. The results of this research suggest that the addition of an embedded barrier layer can increase a graphite/epoxy composite's resistance to thermal stresses and low-velocity impacts. This research indicates that hybrid composites are extremely promising materials for applications of extreme temperatures and stresses.
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Guerfala, Wassim. "Élaboration de bio-composite hybride à matrice thermoplastique : formulation optimale et modélisation du comportement statique en vue d'une application pour pièces de structure dans l'automobile." Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0022.
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L’impact environnemental devient un sujet de plus en plus important dans l’industrie automobile, ce qui pousse les constructeurs à réduire les émissions de CO2 à travers des motorisations propres et à travers l’allègement des structures. Les matériaux composites, associant légèreté et résistance mécanique, présentent une bonne alternative aux aciers standards avec une réduction de masse considérable. L’objectif principal de notre étude est l’application des matériaux bio-composites dans la structure automobile.Pour répondre aux différentes exigences mécaniques, thermiques et économiques, le premier objectif de ce travail est de développer un matériau composite hybride à base de deux fibres naturelles ayant des caractéristiquescomplémentaires permettant d’optimiser les performances du composite, tout en garantissant une homogénéité de son comportement mécanique. Le second objectif concerne l’élaboration d’un outil numérique qui permettrait un pré-dimensionnement rapide de structures qui prend en compte les particularités de ce type de matériau composite hybride. En effet, les exigences et les demandes au sein de l’industrie automobile évoluent rapidement et d’une manière continue, il est nécessaire de pouvoir produire une réponse rapide et à moindre frais (les campagnes expérimentales sont souvent longues et coûteuses pour des matériaux sensibles et encore plus quand ces derniers sont influencés par les conditions environnementales)The environmental impact is becoming increasingly important in the automotive industry, pushing OEMs to reduce CO2 emissions through clean engines and structural weight reduction. Composite materials, combining lightness and mechanical strength, offer a good alternative to standard steels with a considerable weight reduction. This study mainly aims to apply bio-composite materials in the automotive structure.To meet the various mechanical, thermal and economic requirements, the first objective of this study is to develop ahybrid composite material based on two natural fibers with complementary characteristics to optimize its performance while guaranteeing the homogeneity of its mechanical behavior. The second objective is the development of a numeric tool that would allow rapid pre-design of structural parts reinforced with this hybrid composite material. Indeed, the obligations of the automotive industry are quickly and continuously changing; it is necessary to provide quick and cost-effective responses (compared to the long and expensive experimental campaigns especially when there is sensitivity to the environmental conditions to consider)
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Adusei, Paa Kwasi. "Carbon Nanotube-Based Composite Fibers for Supercapacitor Application." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1561996824580323.
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Mahmoud, Bassam. "Modélisation d'impacts sur des stratifiés composites unidirectionnels et hybrides." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30212.
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Les structures aéronautiques sont aujourd’hui largement réalisées à partir de matériaux composites, permettant ainsi d’en diminuer la masse. L’impact sur structure composite est une des sources de dommage la plus courante et la plus pénalisante. L’objectif de cette thèse est de développer un modèle prédictif d’impact sur stratifiés unidirectionnels de faible épaisseur afin, dans un premier temps, de mieux comprendre les mécanismes d’endommagement mis en jeu et, dans un deuxième temps, de pouvoir proposer des pistes d’amélioration de la tenue de ces structures. La première étape de ces travaux a consisté à développer un modèle éléments finis explicite de stratifiés composite unidirectionnel, en s’appuyant sur les travaux d’impact sur pale d’hélicoptère réalisés par F. Pascal. Ainsi, un nouvel élément capable de représenter le comportement à l’impact des plis unidirectionnels a été formulé. Le comportement des paquets de fibres est représenté par des éléments barres stabilisés grâce à des éléments 2D spécifiques. La dégradation de ces éléments est pilotée par des lois d’endommagement déduites d’observations expérimentales. La stratégie de modélisation proposée a été identifiée sur la base d’essais expérimentaux pour deux matériaux : T700/M21 et HTA7/913. Les résultats donnés par le modèle ont ensuite été validés par une comparaison avec des essais d’impact à basse vitesse. Enfin, dans le but d’optimiser la tenue des stratifiés, des impacts à basse et moyenne vitesse sur des stratifiés hybrides unidirectionnels/tissus composites ont été étudiés expérimentalement et numériquement grâce à la stratégie de modélisation proposéeToday, composite materials are largely used in the manufacturing of aeronautical structures, in order to lighten their weight. Impact on composite structures is one of the most detrimental loading. The present study aims to develop a predictive modelling of impacts on thin unidirectional laminates in order to, firstly, better understand the damage mechanisms involved, and, secondly, be able to provide guidance for a strength improvement of these structures. First, an explicit finite element modelling of unidirectional laminates is developed based on the work of F Pascal dealing with impact modeling on helicopter blades. Thus, a new element that can represent the impact response of unidirectional plies is formulated. The behavior of the bundle of fibers is modeled with rod elements stabilized with specific 2D elements. The degradation is managed using damage based on experimental observations. The parameters of the proposed modelling strategy are identified on the basis of experimental tests carried out on T700/M21 and HTA7/913 composites. The results provided by the modeling are then validated by a comparison with experimental low velocity impact results. Finally, in order to improve the laminate strength, low velocity and medium velocity impacts on hybrid unidirectional/woven composite laminates are studied experimentally and with the developed modelling strategy
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Fox, Matthew J. "Numerical modeling of air blast effects on hybrid structures." Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2630.
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Thesis (M.S.)--West Virginia University, 2002.Title from document title page. Document formatted into pages; contains x, 114 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 42-45).
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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 materialsEn 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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Amerini, Francesco. "Advanced hybrid joint design configurations for improved performance of composite structures." Thesis, University of Bath, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604566.
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The continuous research of lightening mechanical and aeronautical structures is leading to the adoption of innovative materials and structure designs. and this development has to be necessarily followed by research in optimising structural health monitoring techniques. The set up of a reliable and quick monitoring technique. together with the enhancement of the mechanical performances of structures, is the tUl1ung point to the usage of even lighter and longer-lifed structures. Being impossible to build up a monolithic structure, it is common sense to understand that the most critical part of a structure is the joint between two or more different parts. For this reason, research is being focused on both the improvement of existing joint configuration, and the development of automatic systems which are able to monitor the health state of these joints when the structure is in service. The main reason urging to improve the current composite fastening joint and to develop innovative in situ monitoring techniques is linked to the continuous pursuit of cost reduction. In fact, a stronger and longer lifed fastening configuration, together with a reliable. quick and real-time non-destructive monitoring system applied on in service structures, would allow a considerable cut in maintenance time, with a consequent drop of costs. The objectives of this PhD work are manifold. On one side it focuses on the development of an innovative structural coupling configuration which is able to improve the mechanical properties of the joint; on the other hand, it aims to define reliable indexes able to assess the state of health of a joint structure. More precisely. the entire part concerning the monitoring side of the problem, it focuses on the definition of different possible method capable of determining the loosening state of a bolted connection. These methods are all based on the vibration and ultrasonic based techniques. The first step consists in the development of indexes able to predict the healthy state of a joint by studying some properties related to acoustic signals passing through the part's connection. After theoretically defining the parameters involved, experimental campaigns aimed to validate the models have been carried-out. Once the indexes were found, and confirmed to work on a small simplified structure, the most reliable and accurate IS chosen to be applied for the monitoring procedure on larger and more complicated structures. Both theoretical and experimental approaches were adopted to justify the reliability of the used method. Ultimately it was proved that with the adoption of few sensors and natural frequencies based vibration, with the developed method, it is possible to assess the location of a loosening bolt also on a multibolted structure. Additional research has to be done on real larger scale structures, hut promising results based on solid theoretical principles have been achieved. With regards to the necessity of enhancing existing fastening coupling configuration, all the efforts concentrate on the adoption and optimization of hybrid joints. Hybridization joint process takes advantages of positive aspects of both composite materials and fastening joints. Most important, the rising use of composite parts contributes to the reduction of structures' weight, with all the advantages involved, such as for instance, fuel consumption reduction with a consequent decrease of running costs. For this reason the second part of the thesis will discuss possible solution able to get out the best from coupling together composite materials and fastening configuration. More precisely all the attentions will focus on how to reduce problems generated by fastening composite parts, such as low bearing and shear strength, notch sensitivity and high dependency of joint strength from the lay-up configuration. The proposed solution will be as strong as the hybrid solutions developed so far, but also lighter at the same time
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Li, Ming-Sang. "Higher order laminated composite plate analysis by hybrid finite element method." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/40145.
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Ahsan, Shainur. "Evaluation of Hybrid-Composite Beam for Use in Tide Mill Bridge." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/35061.
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A test program for the Hybrid-Composite Beam (HCB) was conducted prior to its use for the replacement of a skewed, simply-supported bridge (Tide Mill Bridge). The HCB is an innovative combination of conventional materials and ideas in a structural beam. The beam consists of a concrete arch tied with prestressing strand that is placed within a Fiber-Reinforced Polymer (FRP) box. Behavior in individual HCBâ s and a three HCB-system was examined to determine the appropriateness of the current design methodology developed by John Hillman and the simplifying assumptions made within it. Such assumptions include strain compatibility and linear-elastic behavior. Three HCBâ s were tested at the structures laboratory at Virginia Tech. During individual beam tests, the predicted behavior of the FRP box and prestressing strand agreed with experimental results. The tests revealed the arch was susceptible to local bending and behaved far differently from predicted. Overall, the beams were shown to behave linearly. A final test was performed to apply the design live load to the system. Slight non-linear behavior was observed in the beams. Distribution factors for the system were also investigated and compared to AASHTO and Hillmanâ s model. AASHTO factors were conservative for exterior girders but unconservative for interior girders. Hillmanâ s factors were often conservative but were in agreement for the shear in the exterior girder. The current design procedure appeared to predict FRP and strand behavior well, but the behavior of the arch appeared to differ greatly from the other components of the HCB.Master of Science
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Salem, Adel I. "Weight and Cost Multi-Objective Optimization of Hybrid Composite Sandwich Structures." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1478637482819839.
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Abeysinghe, Mudiyanselage Chanaka Madushan Abeysinghe. "Static and dynamic performance of lightweight hybrid composite floor plate system." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/60323/1/Chanaka_Abeysinghe_Mudiyanselage_Thesis.pdf.
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In the modern built environment, building construction and demolition consume a large amount of energy and emits greenhouse gasses due to widely used conventional construction materials such as reinforced and composite concrete. These materials consume high amount of natural resources and possess high embodied energy. More energy is required to recycle or reuse such materials at the cessation of use. Therefore, it is very important to use recyclable or reusable new materials in building construction in order to conserve natural resources and reduce the energy and emissions associated with conventional materials. Advancements in materials technology have resulted in the introduction of new composite and hybrid materials in infrastructure construction as alternatives to the conventional materials. This research project has developed a lightweight and prefabricatable Hybrid Composite Floor Plate System (HCFPS) as an alternative to conventional floor system, with desirable properties, easy to construct, economical, demountable, recyclable and reusable. Component materials of HCFPS include a central Polyurethane (PU) core, outer layers of Glass-fiber Reinforced Cement (GRC) and steel laminates at tensile regions. This research work explored the structural adequacy and performance characteristics of hybridised GRC, PU and steel laminate for the development of HCFPS.
Performance characteristics of HCFPS were investigated using Finite Element (FE) method simulations supported by experimental testing. Parametric studies were conducted to develop the HCFPS to satisfy static performance using sectional configurations, spans, loading and material properties as the parameters. Dynamic response of HCFPS floors was investigated by conducting parametric studies using material properties, walking frequency and damping as the parameters. Research findings show that HCFPS can be used in office and residential buildings to provide acceptable static and dynamic performance. Design guidelines were developed for this new floor system. HCFPS is easy to construct and economical compared to conventional floor systems as it is lightweight and prefabricatable floor system. This floor system can also be demounted and reused or recycled at the cessation of use due to its component materials.
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Mwita, Wambura Mwiryenyi. "Development and testing an intelligent hybrid polymeric composite beam with healing ability embedded with Ni-Ti shape memory alloy." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1251.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.Hybrid polymeric composites (HPC) are widely used for the design of aerospace, automobile and civil engineering structures. One of the major challenges posed by these materials and structures is their brittle nature. When subjected to impact and dynamic loads, the polymeric composite structures undergo micro cracking. The cracks coalesce, propagate and can lead to catastrophic failure of the material and structures. In this thesis, an intelligent hybrid polymeric composite (IHPC) beam with healing ability was developed and tested. The IHPC beam developed consisted of a 3% prestrained 1mm diameter Ni-Ti shape memory alloy (SMA) wire actuator embedded in the polymeric host matrix. The function of the embedded Ni-Ti shape memory alloy was to enhance intelligence and healing ability to the IHPC beam. Upon electric current resistance heating, the Ni-Ti SMA actuator responds by contracting as a result of detwinned martensite → austenite phase transformation. Contraction of the SMA in the IHPC beam was utilized to stiffen and enhance healing by retarding crack growth and recovery of the strain induced in the loaded IHPC beam. This can result to increase of the flexural stiffness EI (defined as the product of the Young’s Modulus E of the material and the moment of inertia I of the geometry of the beam) and mode I fracture stress intensity factor KIC of the IHPC beam. One (1) mm diameter Ni-Ti SMA wire was used in the experimental work in this thesis. The wire was cut into 35 pieces, 200 mm long each. Ni-Ti SMA wires were heated in the furnace to a temperature of 250ºC for ten (10) hours then were left to cool in the ambient air. The heat treatment was aimed to release any residual stress and to stabilize the austenite start (AS) and austenite finish (Af) transformation temperatures of the Ni-Ti SMA. After heat treatment, the Ni-Ti SMA wires were prestrained by 3% (based on a gauge length of 150mm) on a tensile testing machine. Prestraining of the Ni-Ti SMA wires was aimed to induce detwinned martensite volume fraction in them hence increasing the transformation strain and recovery force of the Ni-Ti SMA actuator. Intelligent hybrid polymeric composite (IHPC) beams and polymeric virgin (PV) beams, all of dimensions 150mmx25mmx10mm were manufactured by casting 60D polyurethane thermosetting epoxy resin in a silicon mould. transformation strain and recovery force of the Ni-Ti SMA actuator.
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Sudarisman. "Flexural behaviour of hybrid fibre-reinforced polymer (FRP) matrix composites." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2110.
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The flexural behaviour of three different hybrid fibre-reinforced polymer (FRP) matrix composites, i.e. S2-glass/E-glass/epoxy, TR50S carbon/IM7 carbon/epoxy, and E-glass/TR50S carbon/epoxy hybrid FRP composites, has been investigated. The main objectives of this study were to: (i) improve the flexural properties of the parent composite materials, i.e. E-glass/epoxy and TR50S carbon fibre/epoxy composites, through substitution of stronger fibres, i.e. S2-glass and IM7 carbon fibres, for the fibres of the parent composite materials, and (ii) determine the optimum stacking configurations that produced the maximum increase in flexural properties of the resulting hybrid composites. In addition to these, two secondary objectives related to the preliminary investigation of determining the optimum stacking configurations have also been established. The two secondary objectives were to: (i) determine the optimum values of the processing parameters of the composites under investigation, and (ii) determine the compressive strength and compressive modulus of the parent materials.The investigation was carried out experimentally, thus data presented and analysed were obtained from laboratory work. Optimum values of five processing parameters, i.e. (i) the concentration of matrix precursor within the solvent solution utilised to wet the fibres, (ii) the compressive pressure applied during hotpress curing, (iii) the vacuum pressure of the atmosphere inside the curing chamber, (iv) the dwell time during hot-press curing, and (v) the holding temperature during hot-press curing, have been established. The criteria for determining the optimum values of these parameters were optimum fibre content, minimum void content, and optimum flexural properties. Compressive strength and compressive modulus of the parent composite materials have also been determined.Specimens were cut from flat composite plates using a diamond-tipped circular blade saw. The longitudinal edges of the specimens were carefully polished to remove any possible edge damage due to cutting. The composite plates were produced from preforms comprised of a number of glass fibre/epoxy prepregs, carbon fibre/epoxy prepregs or a combination of these. All the fabrication procedures were carried out using manual techniques. Whilst the compressive tests were conducted in accordance with the ASTM D3410-03 standard, flexural tests were carried out according to Procedure A of the ASTM D790-07 standard. Span-to depth ratios, S/d, of 16, 32, and 64 were selected for flexural testing in order to determine the minimum value of S/d required to ensure flexural failure rather than shear failure. Fibre and void contents were evaluated from optical micrograph images of the slices perpendicular to the fibre direction of the samples.It was concluded that the optimum values of the five processing parameters under investigations were: (i) epoxy concentration, C[subscript]e ~ 50 wt%, (ii) compressive pressure, p[subscript]c ~ 1.00 MPa, (iii) vacuum pressure, p[subscript]v ~ 0.035 MPa, (iv) dwell time, t ~ 30 minutes, and (v) holding temperature, T ~ 120 °C. Compressive tests revealed that the order of compressive strength for the parent composite materials were arranged as follows: S2-glass fibre/epoxy (476 MPa), E-glass fibre/epoxy (430 MPa), IM7 carbon fibre/epoxy (426 MPa), and TR50S carbon fibre/epoxy (384 MPa). The compressive modulus of these parent composite materials were found to be ordered as follows: IM7 carbon fibre/epoxy (67.9 GPa), TR50S carbon fibre/epoxy (61.8 GPa), S2-glass fibre/epoxy (45.1 GPa), and E-glass fibre/epoxy (32.9 GPa). After considering these compressive properties, three different hybrid combinations, as mentioned earlier, were manufactured and evaluated with the prepreg layers of the fibre composites possessing higher compressive strength being placed at the compressively loaded side of the flexural specimens.Shorter beam specimens (S/d = 16) of the three hybrid systems exhibited increased flexural strength as the amount of stronger fibre content was increased, but no hybrid effect was noted. The increase appeared to follow the rule of mixtures and this was attributed to their failure mode being shear failure. For beams tested at S/d = 32 and S/d = 64, the three hybrid systems demonstrated three different trends. The S2-glass fibre/E-glass fibre/epoxy hybrid system, where the S2-glass fibre (substituted at the compressive loading face) was slightly stronger and stiffer compared to the E-glass fibre at the tensile side, demonstrated increases in flexural strength together with the presence of a hybrid effect following partial substitution of the S2-glass fibre for E-glass fibres at the compressive side. The IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, where the IM7 carbon fibre (substituted at the compressive side) was slightly stronger but significantly stiffer in compression compared to the TR50S fibre at the tensile side, exhibited a slight increase in flexural strength that appeared to obey the rule of mixtures.This result was attributed to the strength increase in the compressive side introduced by the substituted fibres not being sufficient to suppress the increase of internal compressive stress due to the increase in compressive modulus of the substituted fibres. The E-glass fibre/TR50S carbon fibre/epoxy hybrid system, where the E-glass fibre (substituted at the compressive side) was found to be slightly stronger but significantly less stiff in compression compared to the TR50S fibre at the tensile side, demonstrated a significant increase in flexural modulus and also exhibited a significant hybrid effect. The decrease in internal compressive stresses generated at the compressive side due to the decreased compressive modulus of the substituted fibre, when combined with the increase in compressive strength of the substituted fibre, was thought to led to the significant increase of flexural strength for this hybrid system.General trends observed in flexural modulus for the three hybrid systems were reasonably similar with any change in flexural modulus appearing to obey the rule of mixtures. Whilst an increase in flexural modulus was noted for higher contents of stronger fibre in the case of the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, a decrease in flexural modulus with increased quantities of stronger fibre was exhibited by the E-glass fibre/TR50S carbon fibre/epoxy hybrid system. The increase or decrease in flexural modulus was attributed to the relative stiffness in compression of the substituted fibre when compared to that of the respective parent composite materials.Unlike the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system that did not exhibit any significant trend with regards the effect of the substitution of stronger fibre at the compressive side, the E-glass fibre/TR50S carbon fibre hybrid system demonstrated a significant increase in the energy stored to maximum stress with increasing content of the stronger fibre. This increase was mainly attributed to the increased strain–to-maximum stress of the hybrid system with respect to that of the parent composite material.In addition, for the three hybrid systems under investigation, the most significant change in flexural properties was noticed following substitution of the first layer at the compressive face. The relative position with respect to the neutral plane of the substituted layer was thought to be the reason for this phenomenon. It was also noted that flexural properties increased with the increase in S/d. A change in failure morphology was noted with the change of S/d from 16 to 32. It was thus determined that a S/d ratio of at least 32 was required in order to promote flexural failure (as opposed to shear failure). For the S2-glass fibre/E-glass fibre/epoxy hybrid system, this change appeared more obvious in comparison with that the other two hybrid systems with this change being accompanied by a significant increase in flexural strength.The main general conclusions that could be drawn from this investigation were that, although the flexural modulus appeared to obey the rule of mixture, an increase in flexural strength together with the presence of a hybrid effect, would most probably be observed when the fibre substituted at the compressive side possessed a significantly lower modulus combined with significantly higher compressive strength as demonstrated by the hybrid TR50S carbon - E-glass FRP composites. The most significant change in properties was exhibited by the first layer substitution whilst increasing the value of S/d resulted in an increase of flexural strength, with S/d = 32 being determined to be sufficient in order to promote flexural failure as opposed to shear failure.
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Dow, Douglas Donald. "Finite Element and Experimental Analyses of Hybrid Joints Subjected to Fully Reversed Flexure Fatigue Loading." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DowDD2008.pdf.
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Hulatt, Jonathan A. "The structural characterisation of hybrid beams using APCs ideally suited for civil construction." Thesis, University of Surrey, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252374.
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Small, Aaron Charles. "Novel hybrid materials and their applications : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry /." RestrictedArchive@Victoria -- VUW staff and students only, 2008. http://restrictedarchive.vuw.ac.nz.helicon.vuw.ac.nz/handle/123456789/1298.
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