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1

Thanomsilp, Chuleeporn. "Toughening composites for liquid composite moulding." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390838.

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2

Christen, Jean-Loup. "Acoustic transmission through composite shells with noise treatment : Modelling and sensitivity." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC028.

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La transmission acoustique de plaques et de coques est un problème présent dans de nombreuses industries, de l'automobile à l'aéronautique en passant par le génie civil. Il s'agit alors, en présence d'une source externe, de limiter le niveau de bruit à l'intérieur d'une cavité enclose par une structure vibrante, qu'il s'agisse d'une voiture, d'un avion ou d'un immeuble.Les matériaux composites sont de plus en plus largement utilisés par toutes les industries du transport, du fait de leur faible masse rapportée à leur grande rigidité. Ces caractéristiques, utiles pour réduire la consommation énergétique des véhicules, sont cependant un handicap lorsqu'il s'agit de limiter le niveau de bruit intérieur. Il est alors nécessaire d'ajouter des protections acoustiques. On s'intéresse dans ce travail à la transmission d'un bruit produit à l'extérieur de la cavité, et à des solutions antibruit passives, utilisant des matériaux poreux absorbants. Ceux-ci, mousses ou laines minérales, présentent en général de bonnes performances acoustiques pour des fréquences élevées, mais nettement mois intéressantes en basses fréquences. Ce travail s'inscrit dans le cadre d'un projet international ayant pour objectif d'étudier la réduction de bruit à travers des structures composites incluant des protections acoustiques passives. Deux axes y sont privilégiés, la modélisation et l'analyse de sensibilité. En effet, les matériaux poreux et composites présentent souvent de grandes incertitudes, dues au procédé de fabrication, à la difficulté de mesure, ou encore simplement à des choix de conception à faire. On cherche donc à s'assurer de la robustesse des solutions étudiées.Cette thèse est organisée en trois parties. La première traite de la modélisation des structures composites et des traitements poroélastiques. On s'intéresse surtout à deux types de structures, les plaques et les cylindres, pouvant dans les deux cas inclure un grand nombre de couches et de matériaux différents. La deuxième partie traite des méthodes d'analyse de sensibilité, et d'applications dans le cas de la transmission acoustique à travers des structures composites. On s'intéressera enfin dans la troisième partie à l'effet du traitement poroélastique, à travers des études numériques et expérimentales
Acoustic transmission through plates and shells is a problem that appear in many applications, for example in the automotive or aerospace industries, or in civil engineering. The idea is to reduce the noise level inside a caivty enclosed by a vibrating structure, which may be a car, a plane or a building. Composite materials are widely used in the transportation industries due to their light weight and high mechanic resistance, but these features tend to increase the acoustic transparency of the structures, thus making it necessary to add acoustic protections for reducing noise in the enclosed cavity. The most frequently used acoustic protections take the form of layers of poroelastic materials, which are very efficient noise absorbers in high frequencies, but perform less efficiently in lower frequency ranges.This thesis is part of an international project aimed at improving the noise reduction performance of composite structures through passive sound packages. This implies the development of reduced models of acoustic transmission through such structures, and optimization studies on these models. Besides, the robustness of a solution with respect to uncertainties in the model have to be ensured. This thesis is organised in three parts, dealing with numerical modelling, sensitivity analysis for acoustic transmission and the effect of a porous treatment on sound transmission
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3

Podnos, Eugene Grigorievich. "Application of fictitious domain method to analysis of composite materials /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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4

Palmer, Nathan Reed. "Smart Composites evaluation of embedded sensors in composite materials /." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/palmer/PalmerN0809.pdf.

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As an emerging form of renewable energy, horizontal wind turbines have experienced advancements in improving efficiency and reliability. These advances have pushed the limits of current technology used in wind turbines. Smart blades have been proposed as a method of addressing these limitations. Sensor integration within blade construction is the first step in development of smart blades. Thus, several low cost sensors were chosen, 1 axis strain gages, polyvinylidene fluoride films (PVDF), and single mode fiber optics either coated in acrylate or polyimide. To ensure successful bonding between sensor and composite two surface treatment techniques were developed. The first, dipping of the sensor into a bath of 20% by weight solution of nitric acid and the second was submersion of the sensor in the nitric acid for ten seconds prior to removal. These treatments were compared against sensors not surface treated prior to embedding. These sensors were embedded within samples created of fiberglass and epoxy or vinyl ester resin. Two different material tests were conducted. Tensile testing allowed for evaluation of sensor sensitivity, sensor failure point, material tensile modulus, and material tensile strength. Mode I fracture toughness evaluation, indicated the level of successful bonding which occurred during resin curing. Field Emission Scanning Electron Microscopy (FESEM) was conducted to further confirm the level of bonding between resin and sensor, post fracture. Results for embedded strain gages showed an adverse effect for vinyl ester samples. Epoxy samples fared better, thus concluding manufacturing success for epoxy samples, submersion being preferred, and alternative methods needed for vinyl ester samples. PVDF films had good qualitative FESEM images combined with increasing trends. It was concluded that integration for both resin groups with sensors submerged in nitric acid was successful. Fiber optics coated in acrylate also showed good bonding under FESEM imaging as well as testing. It was thus concluded that submersion was the preferred treatment. Lastly, fiber optics coated in polyimide embedded in vinyl ester composites showed significant drawbacks and it was concluded that alternative methods need exploration. Those embedded in epoxy were successfully integrated and submersion in nitric acid showed the most potential.
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5

Zhang, Fangzhou. "Multiscale modeling of laminated composites under extreme environmental conditions." Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0027/document.

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À haute température, l'oxygène réagit avec la matrice organique du matériau composite, ce qui change les propriétés du matériau et réduit la résistance à la rupture globale. Mais la compréhension de la dégradation du composite stratifié oxydé, en particulier son comportement à l'échelle du pli, est aujourd'hui limitée et phénoménologique. Les travaux dans cette thèse ont été réalisés pour donner notre contribution sur les aspects méthodologiques de ce sujet. Des essais sont réalisés pour caractériser expérimentalement le comportement d'éprouvette oxydée : en particulier, un nouveau essai, l'essai 'oxy-délaminage', a été développé pour identifier la ténacité du matériau composite vieilli. Une stratégie a été proposée d'étudier le problème à partir des propriétés de la matrice oxydée à l'échelle fibre/matrice et jusqu'à la reproduction et la prédiction du comportement de fissuration transversale des échantillons oxydés à échelle méso via un procédé d'homogénéisation
At high temperature, the oxygen reacts with the organic matrix of composite material, which changes the material properties and reduces the resistance to global failure. But understanding on the degradation of the oxidized composite laminate, particularly its damage behavior, is now limited and phenomenological. Work in this thesis has been made to give our contribution to the methodological aspects of this topic. Tests are performed to characterize experimentally the behaviors of the oxidized specimens: in particular, a new test test oxy-delamination ', was developed to identify the tenacity of composite material aged. A strategy has been proposed to study the problem from the properties the oxidized matrix at the fiber/matrix scale up to the reproduction and predicting the behavior of transverse cracking of the sample at the scale of a ply via a homogenization process
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6

Do, Nascimento Oliveira Jose Emidio. "Deformation and damage analysis of composite beams equipped with polyvinylidene fluoride film sensors /." [S.l. : s.n.], 2008. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1001&context=td_cput.

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7

Yang, Heechun. "Modeling the processing science of thermoplastic composite tow prepreg materials." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/17217.

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8

Somanath, Nagendra. "A finite element cure model and cure cycle optimization for composite structures." Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04272010-020304/.

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9

Call, Russell Kent. "Parameter establishment and verification of a fabrication stress model and a thermo-kinetic cure model for filament wound structures." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040256/.

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10

Klug, Jeremy Hager. "High-performance adhesive systems for polymer composite bonding applications /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9883.

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11

Ducept, Fabrice. "Prévision de la rupture des assemblages collés composite/composite et acier/composite." Poitiers, 1996. http://www.theses.fr/1996POIT2366.

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Dans le cadre de la mécanique linéaire de la rupture, on détermine un critère d'amorçage en mode mixte dans un composite verre/époxyde. Les montages utilises sont DCB, ENF et MMB. Le rapport des modes obtenu a partir de la théorie des poutres est proche de celui qui utilise les valeurs expérimentales des complaisances. Le point d'amorçage correspondant au point de perte de linéarité de la courbe charge/déplacement est voisin de celui qui correspond au premier signal acoustique. On vérifie que le critère de délaminage est indépendant de l'épaisseur des éprouvettes. Suivant la même démarche, on recherche un critère pour un assemblage colle composite/composite. Ce critère est différent du précédent a cause des valeurs d'énergie d'amorçage plus élevées pour l'assemblage et de la stabilité atypique de ces essais. Enfin, une étude est menée sur la séparation des modes dans le cas d'une éprouvette asymétrique. Des essais de délaminage montrent qu'une approche qui prend en compte le champ de singularité au voisinage de la pointe de fissure est mieux adaptée qu'une approche du type théorie des poutres. Les expériences réalisées sur des assemblages acier/composite n'ont pas permis de trancher en faveur de l'une ou l'autre méthode
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12

Westin, Mikael. "Liquid Composite Molding of Multiphase Composites Using Resin with Nanofibrillated Cellulose : Distribution of Particles and Effect on Composite Properties." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-121.

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Two objectives have served as the basis for the present work. The first objective was to experimentally verify the output of a Monte Carlo-based model on particle deposition in porous structures (i.e. fiber preform) during the resin transfer molding (RTM) process. This model is expected to have a positive impact on process optimization and reduce costs by enabling theoretical prediction of how particles are deposited when nanoparticle filled resin is used in RTM. The second objective was to produce a multiphase composite where the epoxy (EP) matrix makes use of the mechanical enhancement that cellulose nanofibres (CNF) can impart when incorporated into the liquid phase of the used polymer matrix. The study was conducted by production of the CNF-filled EP matrix, and by using this to produce multiphase composites out of glass- as well as carbon fibers. The RTM was carried out in collaboration with CSI Composite Solutions and Innovations Oy (Vilppula, Finland). Characterization techniques, including Raman spectroscopy, optical and electron microscopy were used to investigate the microstructure and for assessment of the CNF distribution in the produced composites. These observations were qualitatively compared with the output from the proposed model to evaluate its applicability. EP/CNF nanocomposites (i.e. the consolidated resin) were evaluated by tensile test to investigate the influence of CNF on the mechanical properties of epoxy. Three-point bending tests (ISO 14125) was performed on the multiphase composite to evaluate the impact of CNF-inclusion in the matrix. Obtained results indicate that the model is consistent with the process by which the CNF are deposited in RTM, as both the model and experiment show that the CNF are accumulated in the upper layers (injection side) of the preform. However, work remains to be done for the model to fully comply with specific aspects of the used reinforcement in RTM (e.g. pore size and geometry of the used fiber reinforcement), and thus predict the correct deposition profile and penetration depth of the CNF. The mechanical tests showed that the incorporation of CNF in the epoxy provides a composite with enhanced performance relative a reference without the CNF. The percentage change relative the reference composite was up to 22 % in flexural strength and 25 % in flexural modulus. It is suggested that the increase in mechanical performance is a result of CNF accumulation due to filtering in the fiber preform.
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13

Jouve, Christophe. "Etude de matériaux composites dans des structures : métal-composite-métal, métal-composite-semiconducteur : application aux capteurs en phase gazeuse." Lyon 1, 1993. http://www.theses.fr/1993LYO10232.

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Les solides organiques offrent des perspectives prometteuses de materiaux pour la realisation de dispositifs electroniques. La sensibilite de ces materiaux a un environnement physico-chimique conduit a les utiliser pour l'integration de capteurs intelligents. Le travail que nous presentons concerne des structures minces de polyethylene (ldpe) dans lequel sont inclus des sels de complexes a transfert de charges (ctc). La methode d'elaboration permet de realiser des films conducteurs de quelques microns d'epaisseur dans lesquels la cristallisation des sels depend des conditions d'elaboration. Une part importante de cette etude est consacree a la correlation entre la composition des films et leurs proprietes de conduction electrique. Nous cherchons aussi, en plus de l'optimisation du procede d'elaboration, a contribuer a une meilleure comprehension des mecanismes de conduction electrique qui restent a eclaircir en ce qui concerne ces materiaux. Les mesures en continu mettent en evidence des phenomenes d'injection au-dela d'une zone ohmique a 10#3v/cm. Les mesures en alternatif (jusqu'a 1 mhz) revelent, suivant la concentration en sels de ttf-tcnq, des variations plus ou moins importantes de la conductivite autour de 100 khz. Des hypotheses concernant le comportement en frequence sont proposees. Ces resultats permettent de determiner differents parametres propres a ces structures et qui caracterisent les modes de conduction observes. Dans l'objectif de l'exploitation de ces films comme detecteur d'entite gazeuse, des essais d'absorption ont ete realises avec de l'oxygene, du dioxide d'azote, du dioxyde de carbone ainsi que sous atmosphere humide. Les premiers resultats obtenus par absorption sont tres encourageants pour la mise au point et le developpement de dispositifs capteurs utilisant ces materiaux
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14

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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15

Chang, Sheau-Miin. "Critical evaluation of strong organic fibers vis-a-vis mechanical performance in flexible structures." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/8479.

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16

Kokan, David R. "Development and use of an improved filament-winding process model." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/12261.

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17

Ward, William F. "A theoretical investigation into the inelastic behavior of metal-matrix composites." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/17244.

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18

Veazie, David R. "Modeling of fiber reinforced composites incorporating distinct interface properties." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/17385.

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19

Kothidar, Arjun. "Use of finite element method to evaluate the strength response of notched composite laminates under tension." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/A_Kothidar_120508.pdf.

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Thesis (M.S. in mechanical engineering)--Washington State University, December 2008.
Title from PDF title page (viewed on July 6, 2009). "Department of Mechanical and Materials Engineering." Includes bibliographical references (p. 115-118).
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20

Tompson, Carl G. "Radiographic determination of the lay-up influence on fatigue damage development under bearing/bypass conditions." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29689.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr. Steve Johnson; Committee Member: Dr. Andrew Makeev; Committee Member: Kyriaki Kalaitzidou. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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21

Gambone, Livio R. "The effect of R-ratio on the mode II fatigue delamination growth of unidirectional carbon/epoxy composites." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29968.

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An investigation of the effect of R-ratio on the mode II fatigue delamination of AS4/3501-6 carbon/epoxy composites has been undertaken. Experiments have been performed on end notched cantilever beam specimens over a wide range of R-ratios (-l ≤R ≤0.50). The measured delamination growth rate data have been correlated with the mode II values of strain energy release rate range ∆G[formula omitted]), maximum strain energy release rate (G[formula omitted]) and stress intensity factor range (∆K[formula omitted]). The growth rate is dependent on the R-ratio over the range tested. For a constant level of ∆G[formula omitted], the crack growth rate decreases with increasing R-ratio. A similar trend is observed when the data is plotted as a function of G[formula omitted]. The effect of plotting the growth rate as a function of ∆K[formula omitted] is to produce an R-ratio dependence opposite to that obtained by either the ∆G[formula omitted] or G[formula omitted] approach. For a constant level of ∆K[formula omitted], the crack growth rate increases with increasing R-ratio. Master equations which completely characterize the fatigue behaviour as a function of ∆G[formula omitted] and ∆K[formula omitted] have been derived, based on the observation that the growth rate law exponent, n and constant, A are unique functions of R-ratio. Values for n are surprisingly large and increase with increasing R-ratio whereas values for A decrease with increasing R-ratio. The effect of time-at-load has been considered in an attempt to explain the existence of the R-ratio dependence of the growth rate. The correct trend can be established for the exponent, n but not for the constant, A. Friction between the crack faces, particularly at higher R-ratios, is proposed as a possible explanation for the observed anomaly. Further evidence of a frictional mechanism operating at higher R-ratios has been discovered through a postmortem fracture surface examination. Additional fractographic observations are presented over the entire range of R-ratios tested. In regions subjected to negative R-ratio cycling, there is no evidence of the characteristic mode II hackle features. Instead, loose rounded particles of matrix material are found. An extensive amount of hackling is observed in regions subjected to low positive R-ratio cycles. The extent of hackle damage visibly decreases in areas where higher levels of R-ratio are imposed. A correlation between the general fracture surface morphology and the fatigue data provides support for the hypothesis that energy for delamination is always available in sufficient quantity, and that growth is dependent on the stresses ahead of the crack tip being sufficiently high.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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22

Wu, Xiang. "Thermoforming continuous fiber reinforced thermoplastic composites." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/9383.

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23

Hsu, Sheng-yuan. "On the prediction of compressive strength and propagation stress of aligned fiber-matrix composites /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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24

Yan, Chang (Karen). "On homogenization and de-homogenization of composite materials /." Philadelphia, Pa. : Drexel University, 2003. http://dspace.library.drexel.edu/handle/1860/246.

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25

Lee, Jaehong. "Vibration, buckling and postbuckling of laminated composites with delaminations." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-170322/.

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26

Alvarez-Valencia, Daniel. "Structural Performance of Wood Plastic Composite Sheet Piling." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/AlvarezValenciaD2009.pdf.

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27

Morin, Victor. "Elaboration de composites multiférroïque et caractérisation de l'effet magnétoélectrique." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN030/document.

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L'effet magnétoélectrique (ME) est la modification de la polarisation électrique par l'application d'un champ magnétique (effet ME direct), ou bien la modification de l'aimantation magnétique par l'action d'un champ électrique (effet ME inverse).L'utilisation de matériaux composites permet de reproduire de manière extrinsèque cet effet. Le couplage mécanique entre des matériaux magnétostrictifs et piézoélectriques fournit un effet ME extrinsèque plus important à température ambiante que celui fournit intrinsèquement. Nous avons dégagé (théoriquement et expérimentalement) différentes caractéristiques de matériaux nécessaires à l'obtention d'un effet ME important et justifé l'utilisation de ferrite et de PZT dans les composites ME. Nous expliquons dans cette thèse, les méthodes de fabrications des différentes géométries de composites étudiées (empilement de couches ou bien inclusions d'une phase dans l'autre). En particulier, l'utilisation du frittage non conventionnel par Spark Plasma Sintering, pour améliorer le couplage mécanique y est abordée. En nous focalisant sur la géométrie en multicouche, nous avons montré l'importance de facteurs tels que le champ démagnétisant ou encore la symétrie de la structure. Nous présentons un prototype de capteur de courant utilisable en génie électrique. Nous en avons montré sa bonne linéarité et sensibilité, mais aussi ses défauts en terme de bande passante
The magnetoelctric (ME) response consists in the modification of the electric polarization by an applied magnetic field (direct effect) or the modification of the magnetic polarization by an applied electric field (inverse effect). Intrinsic multiferroics are rather uncommon and the effect is often weak at room temperature. An alternative route to achieve ME effect, consists in using magnetostrictive and piezoelectric materials and coupling the two phases by mechanical stress. We draw (theoretically and experimentally) some material characteristics to achieve an importantME effect, which justify the use of ferrite and PZT. We describe the production process of the two studied connectivity schemes (stack of layers or inclusion of a phase in another). We focus on the sintering by Spark Plasma Sintering as a potential improvement of the mecanical bonding. We devoted a part of our work on multilayer composite and showed the importance of some factors such as the demagnetizing effect or the symmetry of the structure. We introduce a current sensor prototype suitable for electrical engineering application. We showed its good linearity and sensitivity but also some effects of its bandwidth
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Vogler, Tracy John. "On the failure and post-failure of fiber composites in compression /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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29

Roy, Annette. "Comportement mécanique en sollicitations monotone et cyclique d'assemblages collés composite-composite et composite-acier." Poitiers, 1994. http://www.theses.fr/1994POIT2257.

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Une analyse numerique en elements finis suggere que les assemblages colles composite/composite et acier/composite presentent des mecanismes d'endommagement differents: pour les assemblages symetriques, une fissure principale s'amorce dans la partie chargee du composite puis se propage en mode mixte (i+ii); pour les assemblages heterogenes, la fissure principale s'amorce sur le bord libre et se propage essentiellement en mode i. La contrainte normale interlaminaire est le critere qui commande l'amorcage de la rupture, ceci est mis en evidence par les phenomenes de vitesses en traction monotone. La differenciation des mecanismes d'endommagement des deux types d'assemblages se retrouve sur leurs durees de vie en fatigue, qui varie en fonction des conditions de chargement imposees. Enfin, l'evolution de l'endommagement en traction monotone comme en fatigue peut etre suivie par une methode extensometrique
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30

Farooq, Mohammed. "Development of FRP based composite fibre for fibre reinforced cementitious composites." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57668.

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This thesis describes a method of development of a novel fibre based on fibre reinforced polymers (FRP), for use fibre reinforcement in concrete. Thermosetting epoxy resin matrix were reinforced with E-glass, S-glass, and Carbon fibre to produce different types of composite fibres. The FRP panels were produced using the Vacuum Infusion technique, and then cut to different fibre sizes. The volume fractions of reinforcements within the FRP fibre were controlled by using woven and unidirectional fabrics. The number of layers of reinforcing fibres were also changed, to obtain the optimal thickness of the fibres. The FRP material was characterized by means of tensile tests and microscope image analysis. Four different compositions of FRP were produced with tensile strengths ranging from 195 MPa to 950 MPa. The different combinations in geometry broadened the total number of fibres investigated to 12. Single fibre pullout tests were performed to obtain the fundamental fibre-matrix interfacial bond parameters for the different FRP fibres. The FRP fibres, being hydrophilic, along with having a unique rough surface texture, showed a good bond with cement matrix. A bond strength superior to industrially available straight steel fibres and crimped polypropylene fibres has been observed. The 3 best fibres were then chosen to examine the flexural behaviour FRP fibre reinforced concrete beams. The optimized FRP fibres, one each of Glass FRP and Carbon FRP were then further investigated to study the effect of matrix maturity, temperature, fibre inclination, and loading rate on the fibre-matrix interfacial behaviour using single fibre pullout tests. Scanning Electron Microscope (SEM) analysis was carried out to identify the effect of above-mentioned factors on the surface characteristics of the fibre. An attempt was also made to optimize the fibre-matrix interface to achieve an optimized failure mechanism by coating the fibre with oil. The ability of the fibre to transfer stresses across a cracked section over extended periods has been investigated by means of fibre-relaxation tests. Finally, to assess durability, the fibres were conditioned at high pH and high temperature after which single fibre pullout, direct tension tests, & SEM analysis were conducted.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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31

Brown, Jessica H. "A machine system for the rapid production of composite structures." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19452.

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32

Ellerby, Donald Thomas. "Processing and mechanical properties of metal-ceramic composites with controlled microstructure formed by reactive metal penetration /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10583.

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33

Cheung, Yin Nee. "Investigation of concrete components with a pseudo-ductile layer /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20CHEUNGY.

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34

Peterson, Nels Royal. "Wood-thermoplastic composites manufactured using beetle-killed spruce from Alaska's Kenai Peninsula." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/N_Peterson_060508.pdf.

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35

Sacks, Serena. "Effects of thermal aging on the mechanical behavior of K3B matrix material and its relationship to composite behavior." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18865.

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36

Breunig, Thomas M. "Nondestructive evaluation of damage in SiC/Al metal matrix composite using x-ray tomographic microscopy." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19999.

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37

Anegunta, Swetha. "Manufacture and rehabilitation of guard-rail posts using composites for superior performance." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1419.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xvii, 153 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 120-123).
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38

Addou, Fouzi. "Métallisation de guide d'onde en matériau composite à matrice époxy par un procédé DLI-MOCVD." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0081/document.

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La fabrication de guides d’ondes à partir d’un matériau composite CFRP isolant, nécessite de rendre la surface interne conductrice électriquement. Cela peut s’effectuer par métallisation, mais des verrous technologiques apparaissent en raison de la géométrie complexe associée à une surface inerte. Le CFRP est composé d’époxy dont la température de transition vitreuse est de 216 °C, ce qui limite le choix des techniques de métallisation. De plus, l’énergie de surface du polymère qui compose la surface du CFRP est plutôt faible (20-40 mJ/m2) et non polaire, ce qui conduit à une adhérence faible des revêtements métalliques. Le procédé DLI-MOCVD est utilisé pour le dépôt du revêtement métallique car il combine un contrôle rigoureux des débits de réactifs, des vitesses de croissance élevées et il est adapté pour revêtir des substrats tridimensionnels. Le choix du métal (le cuivre) est basé sur un savoir-faire antérieur de l’équipe de recherche, pour la possibilité de le déposer à une température bien inférieure à 216 °C, et bien entendu pour son excellente conductivité électrique et sa résistance au vieillissement ambient. Le film de Cu est élaboré à partir du précurseur organométallique (hfac)Cu(MHY), développé par P. Doppelt au CNRS. Ce précurseur qui se présente sous forme liquide à Tambiante, est dilué dans de l’octane anhydre pour pouvoir être injecté par le système DLI. Après avoir implémenté un réacteur dédié au travaux de la thèse, une étude de cinétique chimique du dépôt à partir du précurseur a permis de définir les conditions expérimentales optimales ; notamment la température de dépôt fixée à 195 °C. Les revêtements obtenus sont partiellement couvrants et sont conducteurs. Leur adhérence avec le substrat est nulle. Par conséquent, on sélectionne puis on teste différents prétraitements du substrat afin de modifier la morphologie et la réactivité de la surface CFRP. On montre à travers six prétraitements que la formation de rugosité de surface favorisant l'ancrage mécanique est un caractère prépondérant pour l’amélioration de l’adhérence, par rapport à la modification chimique. Les deux prétraitements les plus performants sont le traitement par voie humide CircupositTM et le traitement in situ à l’O3 A ce stade, les films sont conducteurs et adhérents mais ils ne mouillent pas intégralement la surface du composite lors du dépôt. On démontre alors que l’injection d’un précurseur de cobalt (Co2(CO)5) en alternance avec le dépôt de Cu permet d’obtenir un revêtement de cuivre métallique, pur à plus de 98 %, couvrant, conducteur et adhérent. A ce stade, le rôle du précurseur de Co n’est pas clairement établi. Néanmoins, les études préliminaires d’industrialisation du procédé consistant à améliorer les rendements et vitesses de croissance sont entreprises. Notamment, les coûts sont abaissés en remplaçant le solvant octane. Avec ce solvant, le dépôt de Cu est adhérent sans prétraitement préalable de la surface du substrat. A noter que le précurseur de Co est toujours nécessaire pour assurer une couverture complète de la surface CFRP. C’est dans ces conditions de dépôt, et après quelques ajustements paramétriques que les premiers guides d’ondes de 60 mm sont revêtus. Les résultats des tests de cyclage thermique étant positifs, la longueur des guides d’ondes à revêtir est augmentée à 300 mm, dimension minimale pour pouvoir effectuer des tests de transmission des ondes radiofréquences : la propriété finale. Cette modification géométrique requière une phase d’optimisation plus complexe afin de garantir l’uniformité en épaisseur et en propriétés électriques sur toute la longueur. Les guides d’ondes de 300 mm métallisés passent les cyclages thermiques avec succès. Les tests radiofréquences indiquent un taux de transmission des ondes < 30 dB, ce qui est tout à fait acceptable d’un point de vue applicatif. En revanche, les pertes sont importantes en comparaison avec l’existant, mais de nombreuses pistes d’améliorations sont proposées
The manufacturing of waveguides from insulating C fibers reinforced polymer composites necessitates to render internal surfaces electrically conductive. This can be achieved by metallization but technological bottlenecks arise due to the complex geometry and the chemical inertia of the surface. The CFRP matrix is composed of RTM6 epoxy whose glass-transition temperature equals 216 °C, limiting the choice of metallization techniques. Additionally, the surface energy of the polymer (constituting the surface of the CFRP) is low (20-40 mJ/m2) and non-polar, i.e. a poor adherence is expected for metallic coatings. A DLI-MOCVD process is used to form the metallic coating because it combines a good control of reactive fluxes, high deposition rates, and because it is relevant for the coating of three-dimensional substrates. The choice of the metal (Cu) is dictated by the anterior know-how of the research group, by the possibility to deposit at a temperature well below 216 °C, and because Cu shows an excellent electrical conductivity and a good resistance to ambient ageing. The Cu film is formed from the organometallic precursor (hfac)Cu(MHY), developed par P. Doppelt at CNRS (Paris). The precursor is diluted in anhydrous octane to make it injectable by DLI. After the mounting and implementation of the DLI-MOCVD reactor dedicated to the PhD work, a study of the chemical kinetics of the deposition from this precursor helped in the definition of the optimal conditions; noticeably the deposition temperature fixed at 195 °C. The coatings are partially covering and interfacial adherence is poor, but they are conductive. Consecutively, we identify, develop and test several pretreatments in order to modify the topography and reactivity of the CFRP surface. Based on 6 recipes, we show that mechanical anchorage is preponderant over the chemical reactivity to improve the adherence. The two best pretreatments are the solution chemistry treatment CircupositTM, and the in situ treatment with O3. At this stage of the work, Cu films are conductive and adherent but they do not wet the entire composite surface, even after long deposition duration. We then demonstrate that the injection of a Co precursor (Co2(CO)5) alternating with the Cu deposition leads to the formation of a pure metallic Cu film (> 98%) which is covering, conductive and adherent. The role of the Co precursor is not yet established. Nevertheless, we start the preliminary process industrialization studies consisting in the improvement of the growth rate and the yield. Noticeably, costs are decreased by replacing the octane solvent. With it, the Cu coating is adherent without any pretreatment of the substrate surface! The Co precursor is still necessary to ensure the proper covering of the entire surface, though. In these conditions, and after adjustments of some parameters, the first 60 mmlong waveguides are coated. The thermal cycling resistance is excellent. Therefore, waveguides length is increased to 300 mm, the minimum dimension for the radiofrequency transmission tests (final property) to be correct. The increase of length causes a complex adaptation of the process in order to guarantee the deposition of a uniform coating over the length, in terms of thickness and electrical properties. Radiofrequency tests result in a stationary waves rate < 30 dB, which is acceptable at the industrial level. Yet, losses are too important in comparison with current waveguides, but many proposals are formulated to improve our solution
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39

Granat, Cécile. "Étude des mécanismes d’auto-adhésion entre élastomère et matériau composite : Impact des paramètres de formulation et de mise en oeuvre des élastomères et du composite sur les caractéristiques de l’assemblage." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0054.

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Dans de nombreux domaines, tels que l’aéronautique et l’aérospatial, les matériaux composites sont utilisés par soucis d’allègement des structures. Pour cette même raison, les assemblages mettant en jeu ces matériaux sont préférentiellement réalisés par collage. Ce mode d’assemblage présente aussi l’avantage d’éviter tout risque d’endommagement engendré par des ruptures de fibres. Néanmoins, chacune des opérations de mise en œuvre du collage doit être maîtrisée, en particulier lorsque des élastomères réticulés, réputés peu aptes au collage, sont impliqués. Ainsi, un primaire est généralement utilisé pour assurer l’adhésion entre l’élastomère et le matériau composite. Dans ce travail de thèse, il s’agit de supprimer l'étape d’enduction du primaire à la surface de l’élastomère réticulé avant bobinage des fibres imprégnées de résine. Cette suppression vise à réduire les risques Hygiène Sécurité Environnement (primaire classé Cancérigène, Mutagène et Reprotoxique) et permet de simplifier les cycles de fabrication. Pour assurer l’adhésion entre l’élastomère réticulé à base d’EPDM et le matériau composite à matrice époxyde sans élément intermédiaire, il est essentiel de comprendre les mécanismes de formation de l’assemblage : création de liaisons physiques, influence de la rugosité de surface, diffusion de monomères et réactions chimiques. Cette compréhension permet par la suite de modifier la formulation des matériaux, dans notre cas remplacer le copolymère présent dans l’élastomère, afin d’améliorer l’adhésion et de s’affranchir de tout traitement de surface
In many fields, in particular in aeronautic and aerospace, assemblies by bonding instead of bolting are used in order to lighten structures involving composite materials. Furthermore chemical bonding minimizes the risk of damage by fibers breaking. In this context, our research work concerns the assembly between a cured elastomer, known to be difficult to be bonded, and a composite material without using adhesives which are classified as carcinogenic, mutagenic and toxic agent. In order to have a good adhesion between cured EPDM elastomer and composite material with epoxy resin without adhesive, it is crucial to understand mechanisms of self assembly of these materials: role of physical bonds, influence of roughness, monomers diffusion and chemical reactions. This good understanding allows us editing material formulations, in our case copolymer in elastomer, to improve adhesion and remove surface treatment
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40

Na, Gwang-Seok. "Load-displacement behavior of frame structures composed of fiber reinforced polymeric composite materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26699.

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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr. Leroy Z. Emkin; Committee Co-Chair: Dr. Abdul-Hamid Zureick; Committee Member: Dr. Dewey H. Hodges; Committee Member: Dr. Kenneth M. Will; Committee Member: Dr. Rami M. Haj-ali. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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41

Raimondi, Luca <1980&gt. "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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42

Wood, Geoffrey Michael. "Treatment of polyethylene fibre for improved fibre to resin adhesion in composite applications." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28528.

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Tensile properties of polyethylene fibres are shown to be very good in comparison to properties of other advanced composite reinforcing fibres. Nevertheless, the use of polyethylene fibres in polymeric matrix composites suffers due to a poor fibre to resin adhesion. However, its ballistic properties are excellent because of the poor adhesion and also fibre ductility. Applications involving structural use of polyethylene fibres are limited by, among others, the low compressive and shear strengths. These are affected strongly by the degree of adhesion. Improvements in bonding are expected to result in greater commercial appeal for the fibres as the property limitations are reduced. Ultra Violet radiation has been shown previously, in laboratory scale batch studies, to induce graft co-polymerization of monomers to polyethylene films. Improvements in wettability and adhesion result when the grafted polymer is compatible to the bonding medium. In this study the technique was adapted to bench scale, continuous fibre treatment, whereby the monomer was surface grafted to the polyethylene substrate. Acrylic acid monomer was used for this due to its relative safety, small molecular size, and high reactivity. Reaction initiation was provided by use of a benzophenone photosensitizer due to the stability of polyethylene to UV radiation. The reaction was performed by pre-coating the fibres with reactants, then exposure to UV radiation. Results of the continuous process for fibre treatment indicate that the monomer concentration and temperature of the preliminary soakings are key variables. Adhesion improvement was measured by single fibre pullout tests and interlaminar shear strength (ILSS) tests. Of these, the ILSS appeared to be more sensitive for judging small improvements. Tensile tests were used to judge property deterioration due to treatment, and flexural property tests gave a preliminary indication of material behavior. The ILSS showed marked improvement from 1.5 ksi for untreated material to over 5.2 ksi for the better treatments. A competing treatment, plasma, shows ILSS values around 3 ksi. The flexural test indicated that failure of UV-grafted polyethylene was in tension, whereas failure of plasma and untreated material was in compression. The study has proven successful in improving the adhesion of polyethylene fibres to an epoxy resin matrix. Commercial viability is currently being developed through decreased process residence times and irradiation exposures.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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43

Bocchieri, Robert Thomas. "Time-dependent deformation of a nonlinear viscoelastic rubber-toughened fiber composite with growing damage /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008280.

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44

Scott, David William. "Short- and long-term behavior of axially compressed slender doubly symmetric fiber-reinforced polymeric composite members." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19276.

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45

do, Nascimento Oliveira Jose Emidio. "Deformation and damage analysis of composite beams equipped with polyvinylidene fluoride film sensors." Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1284.

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In many engineering applications, it is desirable to know the behaviour of structures and systems under loading conditions. One reason is to help optimize the design and prevent damage and failure which might occur during in service and operation. Damage represents a serious problem which can cause catastrophic failure of structures, machines and systems. Therefore for safe operation, efficient and reliable methods for inspection and monitoring of damage are required. Different methods for health monitoring of structures such as non destructive testing (NDT) and strain gauges are widely used. These methods have proven to be efficient in terms of resolution and response. However, some disadvantages associated with them include the vicinity of the area under inspection which must be well known, equipment to acquire the necessary information is expensive and in many cases high skills are required for operation. On the other hand, advances in materials science and MEMS systems has promoted the use of new materials with piezoelectric properties. This include mainly polymeric and ceramic materials which after processed can be used for structural health monitoring. These materials offer a number of advantages such as lightweight, sensitivity, toughness, durability, and low cost. The present research work investigates the feasibility of using a polymeric material, Polyvinylidene Fluoride (PVDF) as a sensor for deformation and defect detection in structures. The sensors are embedded in composite cantilevered type beams to detect defects at distinct locations along the beam’s length. The defect detection method proposed is based on experimental tests and Finite Element simulations. Experimental tests on defect free and beams with manufactured internal flaws were conducted. Numerical (FEM) simulations of defect free and flawed beam models containing sections of reduced elastic modulus to represent the damage were conducted using ANSYS software. The experimental tests have been used for the validation of the numerical solution. Results have shown that the defect location changes the stiffness and indeed the frequency of vibration. For flaws near the fixed end of the beams, lower frequencies are obtained as compared to flaws away from the fixed end. PVDF sensors were used to acquire the natural frequencies of the beams for the first mode of vibration. Good agreement was verified between experimental and numerical simulation results. The work has demonstrated that PVDF film sensors can be used as possible candidates for defect detection. The analysis of the behaviour embedded PVDF sensors near the fixed end of cantilever beams, represents an initial and important step towards the application of measuring static and dynamic behaviour of structures as part of a health monitoring process.
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46

Wong, Yi Wai. "Fabrication of grid-domed textile composite and its application in safety helmets /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20WONG.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 136-139). Also available in electronic version. Access restricted to campus users.
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47

Maillet, Irène. "Propagation de délaminage par fatigue vibratoire dans un matériau composite." Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0010/document.

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Dans le domaine aéronautique les structures sont soumises à de la fatigue sonique due aux phénomènes aéro-acoustiques. Le dimensionnement statique actuel des avions composites couvre les cas de charge en fatigue. Mais avec le besoin de toujours plus réduire la masse de l’avion et l’augmentation des connaissances dans le comportement matériau, les marges statiques vont être réduites dans un futur proche et la propagation par fatigue deviendra un enjeu majeur. Il sera donc nécessaire d’évaluer la possibilité de propagation d’un délaminage dû à une erreur de fabrication ou un impact dans une structure composite. Dans ce contexte, une méthode a été proposée pour étudier la propagation de délaminage sous chargement vibratoire. Tout d’abord, des essais de caractérisation de la propagation de délaminage sous chargement vibratoire ont été mis en place et validés pour les deux principaux modes de rupture. Les effets induits par la fréquence élevée de sollicitation, auto-échauffement induit et vitesse de chargement élevée, ont été pris en compte dans la mise au point et le traitement de ces essais. Ensuite, des outils numériques ont été développés pour permettre la simulation d’une structure délaminée sous chargement vibratoire et l’étude de la propagation du délaminage. A l’aide des approches expérimentales et numériques mises en place et des données matériau identifiées, l’analyse a pu être conduite sur un cas réel de structure aéronautique. Un essai de fatigue vibratoire sur une structure de reprise de plis a ainsi été réalisé. L’évolution du délaminage pendant l’essai est représenté de façon satisfaisante par le modèle numérique
Because of their lightness, stress adaptive design and strong stiffness, composite materials are more and more used in aeronautics. Aeronautical structures are submitted to vibrations during their service life due to aerodynamic turbulent flow around the structure. The current static design of composite aircraft covers fatigue loading cases. But with the need to more and more lighten the structure, and the knowledge increase in material behavior, the static reserve factors will be reduced in the near future and sonic fatigue will become a major issue. It will be necessary to evaluate the possibility of a delamination propagation in a composite structure due to a manufacturing error or to an impact. In this context, a method has been proposed to study the propagation of a delamination under vibratory loading. Firstly, tests to characterize the propagation of delamination under vibration loading have been developed and validated for the two main failure modes. The effects induced by the highfrequency loading, self-heat generation and high speed loading, were considered in the elaboration of these tests and in the data reduction. Then, numerical tools have been developed to allow the simulation of a delaminated structure under vibratory loading in order to study the delamination propagation. Using experimental and numerical approaches and the material data identified, the analysis could be conducted on a real case of aircraft structure. A vibration fatigue test on a ply-drop structure has been achieved. The evolution of delamination during the test is adequately modelized by the numerical model
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48

James, Aaron. "Development of composites materials from waste paper and plastic." Australian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070130.165426/index.html.

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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.
A thesis submitted for the degree of Doctor of Philosophy, Industrial Research Institute Swinburne, Swinburne University of Technology - 2006. Typescript. "August 2006". Includes bibliographical references (p. 361-389).
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49

Wright, Richard J. "Bolt bearing creep behavior of highly loaded polymer matrix composites at elevated temperatures." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17362.

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50

Beck, Richard. "Manufacturing with prestaged thermosetting towpreg." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19030.

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