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Bulsara, Vatsal N. "Effects of fiber spatial distribution and interphase on transverse damage in fiber-reinforced ceramic matrix composites." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/21429.
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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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Clews, Justin David. "Ultrasonic consolidation of continuous fiber metal matrix composite tape." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 190 p, 2009. http://proquest.umi.com/pqdweb?did=1885474451&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Zhuang, Linqi. "Fiber/matrix interface crack propagation in polymeric unidirectional composite." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17391.
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Fiber/matrix interface cracking plays an important role in determining the final failure of unidirectional composites. In the present study, energy release rate (ERR) for fiber/matrix interface debond growth originated from fiber break in unidirectional composite is calculated using 5-cylinders axisymmetric and 3-D FEM models with hexagonal fiber arrangement. In the model the debonded fiber is central in the hexagonal unit which is surrounded by effective composite. The effect of neighboring fibers focusing on local fiber clustering on the ERR is analyzed by varying the distance between fibers in the unit. Two different scenarios are considered, one is the steady-state debond where debond are long and thus there is no interaction between debond tip and fiber break; the other case is when debond are relatively short when debond tip interacts with fiber break. The steady-state ERR is calculated from potential energy difference between a unit in the bonded region far away from the debond front and a unit in the debonded region far behind the debond front. The ERR for different modes of crack propagation is obtained from a FEM model containing a long debond by analyzing the stress at the debond front. For very short debonds, the ERR was calculated by both the J integral and the Virtual crack closure technique (VCCT).For steady-state debond growth, results show that in mechanical axial tensile loading fracture Mode II is dominating, it has strong angular dependence (effect of closest fibers) but the average ERR is not sensitive to the local fiber clustering. In thermal loading the Mode III is dominating and the average ERR is highly dependent on the distance to neighboring fibers. For short debod growth, results show that the debond growth is Mode II dominated and that the ERR strongly depends on the angular coordinate. The local fiber clustering has larger effect on the angular variation for shorter debonds and the effect increases with larger local fiber volume fraction. Finally, the ERR values from 5-cylinder axisymmetric model could be considered as upper bound for the 3-D hexagonal model.Godkänd; 2016; 20160415 (linzhu); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Linqi Zhuang Ämne: Polymera konstruktionsmaterial/Polymeric Composite Material Uppsats: Fiber/Matrix Interface Crack Propagation in Polymeric Unidirectional Composite Examinator: Professor Janis Varna, Avdelningen för materialvetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Diskutant: PhD, R&D Manager Anders Holmberg, ABB AB Composites, Piteå. Tid: Fredag 27 maj, 2016 kl 15.00 Plats: F531, Luleå tekniska universitet
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Davis, Jean E. "Micromechanical modeling of fiber fragmentation in a single fiber metal matrix composite specimen." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17909.
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Zhuang, Linqi. "Effects of Non-uniform Fiber Distribution on Fiber/matrix Interface Crack Propagation in Polymeric Composites." Doctoral thesis, Luleå tekniska universitet, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62974.
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Fiber/matrix interface cracking plays an important role in determining the final failureof unidirectional (UD) composites. When subjected to longitudinally tensile loading,fiber/matrix interface debonds originate from fiber breaks or initial defects propagatealong loading direction. Depending on the quality of fiber/matrix interface, debondscould keep growing longitudinally which leads to the degradation of compositestiffness or kink out of interface and connect with neighboring debonds or fiberbreaks that forms a so called critical fracture plane which leads to the final failure ofUD composite. For UD composite subjected to transversely tensile loading, theinitiation, growth and coalesce of arc-shape fiber/matrix interface debonds result inthe formation of macro-size transverse cracks, the propagation and multiplication ofthese transverse cracks, although would not directly lead to the final failure ofcomposite, could cause significant stiffness degradation of composite structures.In the presence thesis, the growth of a fiber/matrix interface debond of a UDcomposite with hexagonal fiber packing under longitudinal and transverse tensileloading was investigated numerically, with the special focus on the influence ofneighboring fibers. In the current study, energy release rate (ERR) is considered as thedriving force for the debond growth and was calculated based on J Integral andVirtual Crack Closure Technique (VCCT) using finite element software ANSSY.Papers A – C in the present thesis deal with the influence of neighboring fibers on theERR of a debond emanating from a fiber break under longitudinal loading condition.In longitudinal loading case, debond growth is mode II dominated. In paper A, anaxisymmetric model consisting 5 concentric cylinders that represent broken fiber withdebond, surrounding matrix, neighboring fibers, surrounding matrix and effectivecomposite was generated. It’s found that there are two stages of debond growth, thefirst stage is when debond length is short, the ERR decreases with increasing debondlength, and the presence of neighboring fibers significantly increase the ERR ofdebond. For relatively long debond, the debond growth is steady when ERR is almostconstant regardless of debond length. In steady state of debond growth, the presenceof neighboring fibers have little effect on the ERR. In papers B and C, a 3-D modelwas generated with broken fiber and its 6 nearest fibers in a hexagonal packed UDcomposite were modelled explicitly, surrounded by the homogenized composite. Based on the obtained results, it’s shown that ERR is varying along debond front, andhas its maximum at the circumferential location where the distance between two fibercenter is the smallest. This indicates that the debond front is not a circle. For steadystate debond, the presence of neighboring fibers have little effect on averaged ERR(averages of ERR along debond front). For short debond, the presences ofneighboring fibers increases the averaged ERR, and that increase is more significantwhen inter-fiber distance is the smallest. Paper D investigates the growth of afiber/matrix debond along fiber circumference under transverse loading. It’s foundthat debond growth in this case is mixed-mode, and both mode I and mode II ERRcomponents increase with increasing debond angle and then decreases. Debondgrowth is mode I dominated for small debond angle and then switch to mode IIdominated. The presence of neighboring fibers have an enhancement effect on debondgrowth up to certain small debond angle and then changes to a protective effect. InPaper E, the interaction between two arc-size debond under transverse loading isinvestigated. It’s found that when two debonds are close to each other, the interactionbetween two debond becomes much stronger, and that interaction leads to the increaseof ERR of each debond significantly, which facilitates further growth for bothdebond.
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Zu, Seung-Don. "The effect of irregular fiber distribution and error in assumed transverse fiber CTE on thermally induced fiber/matrix interfacial stresses." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3800.
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Thermally induced interfacial stress states between fiber and matrix at cryogenic
temperature were studied using three-dimensional finite element based micromechanics.
Mismatch of the coefficient of thermal expansion between fiber and matrix, and
mismatch of coefficient of thermal expansion between plies with different fiber
orientation were considered. In order to approximate irregular fiber distributions and to
model irregular fiber arrangements, various types of unit cells, which can represent nonuniformity,
were constructed and from the results the worst case of fiber distributions
that can have serious stress states were suggested. Since it is difficult to measure the
fiber transverse coefficient of thermal expansion at the micro scale, there is an
uncertainty problem for stress analysis. In order to investigate the effect of error in
assumed fiber transverse coefficient of thermal expansion on thermally induced
interfacial stresses, systematic studies were carried out. In this paper, the effect of
measurement errors on the local stress states will be studied. Also, in order to determine
fiber transverse CTE values from lamina properties, a back calculation method is used
for various composite systems.
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Swain, Robert Edward. "The role of the fiber/matrix interphase in the static and fatigue behavior of polymeric matrix composite laminates." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07122007-103938/.
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Hu, Yile, and Yile Hu. "Peridynamic Modeling of Fiber-Reinforced Composites with Polymer and Ceramic Matrix." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625367.
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This study focuses on developing novel modeling techniques for fiber-reinforced composites with polymer and ceramic matrix based on Peridynamic approach. To capture the anisotropic material behaviors of composites under quasi-static and dynamic loading conditions, a new peridynamic model for composite laminate and a modified peridynamic approach for non-uniform discretization are proposed in this study. In order to achieve the numerical implementation of the proposed model and approach, a mixed implicit-explicit solver based on GPU parallel computing is developed as well.
The new peridynamic model for composite laminates does not have any limitation in fiber orientation, material properties and stacking sequence. It can capture the expected orthotropic material properties and coupling behaviors in laminates with symmetric and asymmetric layups. Unlike the previous models, the new model enables the evaluation of stress and strain fields in each ply of the laminate. Therefore, it permits the use of existing stress- or strain-based failure criteria for damage prediction. The computation of strain energy stored at material points allows the energy-based failure criteria required for delamination propagation and fatigue crack growth. The capability of this approach is verified against benchmark solutions, and validated by comparison with the available experimental results for three laminate layups with an open hole under tension and compression.
The modified peridynamic approach for non-uniform discretization enables computational efficiency and removes the effect of geometric truncations in the simulation. This approach is a modification to the original peridynamic theory by splitting the strain energy associated with an interaction between two material points according to the volumetric ratio arising from the presence of non-uniform discretization and variable horizon. It also removes the requirement for correction of peridynamic material parameters due to surface effects. The accuracy of this approach is verified against the benchmark solutions, and demonstrated by considering cracking in nuclear fuel pellet subjected to a thermal load with non-uniform discretizations.
Unlike the previous peridynamic simulations which primarily employs explicit algorithm, this study introduces implicit algorithm to achieve peridynamic simulation under quasi-static loading condition. The Preconditioned Conjugate Gradient (PCG) and Generalized Minimal Residual (GMRES) algorithms are implemented with GPU parallel computing technology. Circulant preconditioner provides significant acceleration in the convergence of peridynamic analyses. To predict damage evolution, the simulation is continued with standard explicit algorithms. The validity and performance of this mixed implicit-explicit solver is established and demonstrated with benchmark tests.
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Lhotellier, Frederic C. "Matrix-fiber stress transfer in composite materials elasto-plastic model with an interphase layer." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/40934.
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The matrix-fiber stress transfer in glass/epoxy composite materials was studied using analytical and experimental methods. The mathematical model that was developed calculates the stress fields in the fiber, interphase, and neighboring matrix near a fiber break. This scheme takes into account the elastic-plastic behavior of both the matrix and the interphase, and it includes the treatment of stress concentration near the discontinuities of the fibers. The radius of the fibers and the mechanical properties of the matrix were varied in order to validate the mathematical model. The computed values for the lengths of debonding, plastic deformation, and elastic deformation in the matrix near the fiber tip were confirmed by measurements taken under polarized light on loaded and unloaded single fiber samples. The fiber-fiber interaction was studied experimentally using dog-bone samples that contained seven fibers forming an hexagonal pattern.
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Yang, Fan. "Oxidation and mechanical damage in unidirectional SiC/Si#N# composite at elevated temperatures." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19057.
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Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
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King, Joel David. "Characterization of the corrosion of a P-130x graphite fiber reinforced 6063 aluminum metal matrix composite." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25734.
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Etheridge, George Alexander. "Investigation of progressive damage and failure in IM7 carbon fiber/5250-4 bismaleimide resin matrix composite laminates." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19669.
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Wolford, Gabriela Fernanda. "Failure Initiation and Progression in Internally Pressurized Non-Circular Composite Cylinders." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/43299.
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In this study, a progressive failure analysis is used to investigate leakage in internally pressurized non-circular composite cylinders. This type of approach accounts for the localized loss of stiffness when material failure occurs at some location in a structure by degrading the local material elastic properties by a certain factor. The manner in which this degradation of material properties takes place depends on the failure modes, which are determined by the application of a failure criterion. The finite-element code STAGS, which has the capability to perform progressive failure analysis using different degradation schemes and failure criteria, is utilized to analyze laboratory scale, graphite-epoxy, elliptical cylinders with quasi-isotropic, circumferentially-stiff, and axially-stiff material orthotropies. The results are divided into two parts. The first part shows that leakage, which is assumed to develop if there is material failure in every layer at some axial and circumferential location within the cylinder, does not occur without failure of fibers. Moreover before fibers begin to fail, only matrix tensile failures, or matrix cracking, takes place, and at least one layer in all three cylinders studied remain uncracked, preventing the formation of a leakage path. That determination is corroborated by the use of different degradation schemes and various failure criteria. Among the degradation schemes investigated are the degradation of different engineering properties, the use of various degradation factors, the recursive or non-recursive degradation of the engineering properties, and the degradation of material properties using different computational approaches. The failure criteria used in the analysis include the noninteractive maximum stress criterion and the interactive Hashin and Tsai-Wu criteria. The second part of the results shows that leakage occurs due to a combination of matrix tensile and compressive, fiber tensile and compressive, and inplane shear failure modes in all three cylinders. Leakage develops after a relatively low amount of fiber damage, at about the same pressure for three material orthotropies, and at approximately the same location.Master of Science
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Gardner, Slade Havelock II. "An Investigation of the Structure-Property Relationships for High Performance Thermoplastic Matrix, Carbon Fiber Composites with a Tailored Polyimide Interphase." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30757.
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The aqueous suspension prepregging technique was used to fabricate PEEK and PPS matrix composites with polyimide interphases of tailored properties. The structure-property relationships of Ultem-type polyimide and BisP-BTDA polyimide which were made from various water soluble polyamic acid salts were studied. The molecular weight of the polyimides was shown to be dependant upon the selection of the base used for making the polyamic acid salt. The development of an Ultem-type polyimide with controlled molecular weight and properties similar to commercial Ultem 1000 was accomplished with the Ultem-type TPA+ polyamic acid salt. Both the Ultem-type polyimides and the BisP-BTDA polyimides derived from the NH4+ salt and the TMA+ salt were shown to crosslink at elevated temperatures.
Blends of Ultem-type polyimide with PEEK and BisP-BTDA polyimide with PEEK were prepared to study the structure-property relationships of model composite matrices. Since both polyimides are miscible with PEEK, interdiffusion of the polyimides with PEEK is expected, however, the interdiffusion behavior is complicated by the crosslinking mechanism of the polyimides.
Ultem-type polyimide interphase, PEEK matrix composites and BisP-BTDA polyimide interphase, PEEK matrix composites were fabricated using the aqueous suspension prepregging technique and evaluated to determine the effects of the interphase properties on the bulk composite performance and durability. Three different Ultem-type polyimides from the NH4+, TMA+ and TPA+ polyamic acid salts were used and two different BisP-BTDA polyimides from the NH4+ and TMA+ polyamic acid salts were used. The transverse flexure strength was used to qualitatively rank the composites by level of interfacial shear strength. The longitudinal tensile strength of the composites was shown to vary with relative interfacial shear strength. The trend of these data qualitatively support the existence of a maximum longitudinal tensile strength at an optimum interfacial shear strength. Notched fatigue testing of the Ultem-type polyimide interphase, PEEK matrix composites showed that the initial split growth rate increased with decreasing relative interfacial shear strength.
Ultem-type polyimide interphase, PPS matrix composites were fabricated using the aqueous suspension prepregging technique and evaluated to determine the effects of the interphase properties on the bulk composite performance. Three different Ultem-type polyimides from the NH4+, TMA+ and TPA+ polyamic acid salts were used. The transverse flexure strength was used to qualitatively rank the composites by level of interfacial shear strength. The longitudinal tensile strength of the composites was shown to vary with relative interfacial shear strength. The trend of these data qualitatively support the existence of a maximum longitudinal tensile strength at an optimum interfacial shear strength.Ph. D.
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Lee, Chun-Sho. "A process simulation model for the manufacture of composite laminates from fiber-reinforced, polyimide matrix prepreg materials." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40298.
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A numerical simulation model has been developed which describes the manufacture of composite laminates from fiber-reinforced polyimide (PMR-15) matrix prepreg materials. The simulation model is developed in two parts. The first part is the volatile formation model which simulates the production of volatiles and their transport through the composite microstructure during the imidization reaction. The volatile formation model can be used to predict the vapor pressure profile and volatile mass flux. The second part of the simulation model, the consolidation model, can be used to determine the degree of crosslinking, resin melt viscosity, temperature, and the resin pressure inside the composite during the consolidation process. Also, the model is used to predict the total resin flow, thickness change, and total process time. The simulation model was solved by a finite element analysis.
Experiments were performed to obtain data for verification of the model. Composite laminates were fabricated from ICI Fiberite HMF2474/66C carbon fabric, PMR-15 prep reg and cured with different cure cycles. The results predicted by the model correlate well with experimental data for the weight loss, thickness, and fiber volume fraction changes of the composite. An optimum processing cycle for the fabrication of PMR-15 polyimide composites was developed by combining the model generated optimal imidization and consolidation cure cycles. The optimal cure cycle was used to manufacture PMR-15 composite laminates and the mechanical and physical properties of the laminates were measured. Results showed that fabrication of PMR-15 composite laminates with the optimal cure cycle results in improved mechanical properties and a significantly reduced the processing time compared with the manufacturer's suggested cure cycle.Ph. D.
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Kohlman, Lee W. "Evaluation of Test Methods for Triaxial Braid Composites and the Development of a Large Multiaxial Test Frame for Validation Using Braided Tube Specimens." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333047848.
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Jordan, Alex Michael. "FIBER-COMPOSITE IN SITU FABRICATION: MULTILAYER COEXTRUSION AS AN ENABLING TECHNOLOGY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1467832877.
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Elouaer, Abdelmonem. "Contribution à la compréhension et à la modélisation du comportement mécanique de matériaux composites à renfort en fibres végétales." Thesis, Reims, 2011. http://www.theses.fr/2011REIMS003/document.
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L’industrie des matériaux composites ne cesse d’évoluer et de croître en mettant en place de nouveaux matériaux et de nouvelles technologies. En substitution des matériaux d’origine fossile que les matériaux d’origine naturelles (et surtout végétales) commencent à voir le jour. C’est dans ce contexte que notre travail de recherche est proposé. Il s’intéresse à la caractérisation du comportement mécanique d’un composite à matrice Polypropylène, renforcé avec des fibres de Chanvre et du bois de Chanvre (Chènevotte). Les différents moyens et techniques de caractérisation, utilisés par la présente étude, ont montré que ces nouveaux matériaux sont dotés de propriétés, en particulier mécaniques, de haut niveau, qui viennent rivaliser avec celles des autres composites classiques à base de fibres de verre et de carbone.Les essais expérimentaux en statique et de fatigue, ont révélé beaucoup de détails en comparaison avec d’autres matériaux composites. Ces informations ont permis de créer une sorte de base de données qui pourra servir de référence pour d’autres composites de la même famille à base de fibres végétales. Ainsi, des mécanismes d’endommagement ont été mis en évidence grâce aux essais mécaniques (traction monotone, charge-décharge, …) associés à des observations microscopiques (Microscope Electronique à Balayage), et à des outils de détection du dommage basés sur l’émission acoustique. Par le biais de cette technique, nous avons pu apprécier la qualité et l’importance de l’interface fibre/matrice qui est un paramètre fondamental pour la présente étude et pour la détermination de la loi de comportement du composite.La modélisation micromécanique a été intégrée dans ce travail de thèse, grâce au modèle de Mori-Tanaka. Le comportement des matériaux à l’endommagement n’a pas été pris en considération ; seule l’élasticité a été étudiée. A l’aide de ce modèle, nous avons pu remonter aux propriétés intrinsèques des constituants (le module d’élasticité longitudinale des renforts: Chanvre et Chènevotte)The composites industry continues to evolve and grow by developing new materials and new technologies. Replacing fossil materials by materials with natural origin (especially vegetable) seems to be one of the most promising. In this context our research is proposed. It is interested to characterize the mechanical behavior of a polypropylene matrix composite reinforced with fibers of Hemp and Wood of Hemp (Chenevotte). The various means and characterization techniques used in this study showed that these new materials have interesting mechanical properties, coming rival those of other conventional composites based on carbon and glass fibers.The experimental static and fatigue tests have revealed many details in comparison with other composite materials. The information help creates a database that can serve as reference for other composites of the same family and vegetable fibers. Mechanisms of damage have been highlighted through mechanical tests (tensile monotonous charge-discharge …) associated with microscopic observations (Scanning Electron Microscope), and tools for damage detection based on emission acoustics. Thanks to this technique, we could improve the quality of the interface fiber / matrix which is a basic parameter for this study and for determining the behavior of composite.Micromechanical modeling has been integrated in this thesis, through the Mori-Tanaka model. The behavior of materials during damage has not been taken into account: only the elasticity has been studied. Using this model, we were able to trace the intrinsic properties of the constituents (the longitudinal modulus of elasticity of the reinforcements: Hemp and Chenevotte)
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Hart, Robert James. "Characterization of carbon fiber polymer matrix composites subjected to simultaneous application of electric current pulse and low velocity impact." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1143.
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The use of composite materials in aerospace, electronics, and wind industries has become increasingly common, and these composite components are required to carry mechanical, electrical, and thermal loads simultaneously. A unique property of carbon fiber composites is that when an electric current is applied to the specimen, the mechanical strength of the specimen increases. Previous studies have shown that the higher the electric current, the greater the increase in impact strength. However, as current passes through the composite, heat is generated through Joule heating. This Joule heating can cause degradation of the composite and thus a loss in strength. In order to minimize the negative effects of heating, it is desired to apply a very high current for a very short duration of time. This thesis investigated the material responses of carbon fiber composite plates subjected to electrical current pulse loads of up to 1700 Amps. For 32 ply unidirectional IM7/977-3 specimens, the peak impact load and absorbed energy increased slightly with the addition of a current pulse at the time of an impact event. In 16 ply cross-ply IM7/977-2 specimens, the addition of the current pulse caused detrimental effects due to electrical arcing at the interface between the composite and electrodes. Further refinement of the experimental setup should minimize the risk of electrical arcing and should better elucidate the effects of a current pulse on the impact strength of the specimens.
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Turkyilmaz, Gokhan. "Processing And Assessment Of Aluminum Ceramic Fiber Reinforced Aluminum Metal Matrix Composite Parts For Automotive And Defense Applications." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610751/index.pdf.
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The aim of this study was to produce partially reinforced aluminum metal matrix
composite components by insertion casting technique and to determine the effects
of silicon content, fiber vol% and infiltration temperature on the mechanical
properties of inserts, which were the local reinforcement parts of the components.
Silicon content of alloys was selected as 7 wt% and 10 wt%. The reinforcement
material, i.e. Saffil fiber preforms, had three different fiber vol% of 20, 25 and 30
vol% respectively. The infiltration temperatures of composite specimens were fixed
as 750 °C and 800 °
C. In the first part of the thesis, physical and mechanical properties of composite specimens were determined according to the parameters of silicon content of the matrix alloy, infiltration temperature and vol% of the reinforcement phase. X-ray diffraction examination of fibers resulted as the fibers mainly composed of deltaalumina fibers and scanning electron microscopy analyses showed that fibers had planar isotropic condition for infiltration. Microstructural examination of composite specimens showed that appropriate fiber/matrix interface was created together with small amount of micro-porosities. Bending tests of the composites showed that as fiber vol% increases flexural strength of the composite increases. The highest strength obtained was 880.52 MPa from AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers and infiltrated at 750 °
C. Hardness values were also increased by addition of Saffil fibers and the highest value was obtained as 191 HB from vertical to the fiber orientation of AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers. Density measurement revealed that microporosities existed in the microstructure and the highest difference between the theoretical values and experimental values were observed in the composites of 30 vol% Saffil fiber reinforced ones for both AlSi7Mg0.8 and AlSi10Mg0.8 matrix alloys. In the second part of the experiments, insertion casting operation was performed. At casting temperature of 750 °
C, a good interface/component interface was obtained. Image analyses were also showed that there had been no significant fiber damage between the insert and the component.
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Russell, Blair Edward. "Material Characterization and Life Prediction of a Carbon Fiber/Thermoplastic Matrix Composite for Use in Non-Bonded Flexible Risers." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/30797.
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In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response Group (MRG) at Virginia Tech had the primary responsibility to develop the models for long-term behavior, especially remaining strength and life. The MRG is also responsible for the characterization of the material system with a focus on the effects of time, temperature, and environmental exposure. The present work is part of this effort. The motivation to use a composite material in a non-bonded flexible riser for use in the offshore oil industry is put forth. The requirements for such a material are detailed. Strength analysis and modeling methods are presented with experimental data. The effect of matrix crystallinity on composite mechanical properties is shown. A new method for investigating matrix behavior at elevated temperatures developed. A remaining strength life prediction methodology is recalled and applied to the case of combined fatigue and rupture loading.Master of Science
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SOUZA, LUCIO ROSSI DE. "EFFECTS OF AGING IN WATER AND LUBRICATING OIL ON THE CREEP BEHAVIOR OF POLYMER MATRIX COMPOSITE REINFORCED WITH GLASS FIBER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26952@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Esse estudo tem como objetivo verificar as consequências do envelhecimento no comportamento à fluência de um material compósito reforçado por fibras de vidro, em função de diferentes tipos de envelhecimento e temperaturas de ensaio. Para tanto, corpos de prova envelhecidos em água e óleo, bem como outros sem qualquer envelhecimento, foram ensaiados à fluência em 25 graus Celsius e 60 graus Celsius. As análises se basearam nas propriedades mecânicas relativas ao processo de fluência obtidas tanto experimentalmente quanto a partir de modelos viscoelásticos e semiempíricos. Dentre as condições experimentais empregadas, o parâmetro que mais influenciou o processo de fluência foi a temperatura. Os efeitos da temperatura no processo de fluência foram determinantes inclusive para a escolha do modelo que melhor se ajustou aos pontos experimentais. Na temperatura de 25 graus Celsius, independente do meio ou tempo de envelhecimento, o modelo de melhor ajuste foi o de Potência, enquanto que na temperatura de 60 graus Celsius, o modelo de Andrade foi o que melhor se ajustou aos pontos experimentais. No entanto, observou-se, também, que os diversos tipos de envelhecimentos alteraram algumas propriedades, como o módulo de Young.
The objective of this work is to verify the consequences of ageing on the creep deformation behavior of a fiberglass composite material, as a function of various combinations of ageing means, ageing times, and test temperatures. For this purpose, samples aged in water and oil, as well as samples not aged at all, were tested to creep deformation at 25 Celsius Degree and 60 Celsius Degree. The results analysis were based on mechanical properties, related to the creep deformation process, obtained both directly from the experiments and from viscoelastic and semi-empirical mathematical models. From all the experimental conditions used on this work, the one that most influenced the creep deformation process was temperature. The effects of temperature on the creeping process, that they were even decisive to select the best fitting model for the experimental data. For the 25 Celsius Degree tests, regardless of ageing mean or time, the mathematical model that best fitted the data was the Power model, as for the 60 Celsius Degree tests, the best model to fit the experimental data was Andrade. However, it was noticed that ageing by itself was also capable of changing some mechanical properties, as Young modulus, for example.
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Butler, Joseph Edmund. "In-situ Fiber Strength Distribution in NextelTM 610 Reinforced Aluminum Composites." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32433.
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MetPreg, a composite developed by Touchstone Research Laboratories (Tridelphia, WV), is an aluminum metal matrix composite reinforced by continuous NextelTM 610 alumina fibers. The question is, after processing, are the NextelTM fibers affected in any way that their strengthening contribution to the composite is reduced? From experimentation and statistical analysis, a strength distribution of pre-processed NextelTM 610 fibers is formed and an empirical correlation is developed relating strength to the observed flaw size on the failed single fibers. This correlation is then independently applied to flaw size information gathered from fibers on the fracture surface of MetPreg samples to develop a separate strength distribution of post-processed NextelTM 610 fibers. The pre- and post-processed distributions are compared to one another to determine the effect, if any, that composite processing has on the strength of NextelTM 610 fibers. The results indicate that the in-situ strength distribution of fibers was increased by composite processing.Master of Science
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Nenov, Stanislav Stojanov. "Technologie výroby sklolaminátového dílu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318775.
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Diploma thesis is focused on production technology of the glass fibre polyester part. It introduces characteristics of the composite materials and their dividing by the reinfocement geometry, reinforcement dimensions, reinfocement material and matrix materiál. In the final chapters thesis describes production technologies and proces of launching new part from 3D data to data and drawings of the mould including creation of the technological process.
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Zhang, Wenyong. "Modification of carbon fiber / epoxy matrix interphase in a composite material : Design of a self-healing interphase by introducing thermally reversible Diels-Alder adducts." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0127/document.
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Une interphase fibre de carbone/matrice époxy thermiquement auto-réparable a été construite sur la base de liaisons covalentes Diels-Alder (D-A) thermiquement réversibles. L’interphase modifiée par D-A a été formée en greffant des groupes maléimide sur la surface de la fibre de carbone et en introduisant des groupes furane dans le réseau polyépoxy. La capacité d’auto-réparation interfaciale a été caractérisée par le test de déchaussement de la micro-goutte. La surface de la fibre de carbone a subi un traitement en trois étapes : (i) oxydation par l’acide nitrique, (ii) amination par la tétraéthylènepentamine (TEPA) et (iii) greffage de bismaléimide (BMI). Après chaque étape de traitement, les modifications physico-chimiques de surfaces de la fibre ont été caractérisées par microscopies (MEB et AFM) et par spectroscopies (XPS, et ATR-FTIR). La modification de la matrice a été effectuée en copolymérisant le furfuryl glycidyl éther (FGE) au réseau époxy/amine et les propriétés de la matrice ont été évaluées par TGA, DSC, ATR-FTIR, et traction uniaxiale. Le caractère réversible des liaisons Diels-Alder a été également vérifié par DSC, TGA et RMN. Pour caractériser les capacités d'auto-réparation de l’interphase modifiée par D-A, les propriétés mécaniques et les capacités d'auto-réparation de l'interphase construite en combinant la matrice DGEBA-FGE/amine avec une série de fibres de carbone greffés par BMI ont été mesurées en fonction du temps d’oxydation préalable au greffage (gouvernant la réactivité de la fibre de carbone). Enfin, car le FGE joue un double rôle dans le système interfacial modifié par D-A, à la fois dans l’architecture en intervenant comme allongeur de chaîne entre nœuds de réticulation du réseau époxyde et au niveau de l’interphase en contribuant dans la formation des liaisons réversibles, l'influence de la concentration de FGE dans la matrice a été étudiée sur les propriétés mécaniques de l'interphase et également sur les propriétés mécaniques de la matrice. Par conséquent, ce travail a permis d’aboutir à la procédure optimale pour construire une interphase fibre de carbone/époxy thermiquement auto-réparable basée sur des liaisons covalentes Diels-Alder (thermo réversibles). L'interphase ainsi formée possède non seulement des capacités d’auto-réparations multiples, mais également des propriétés mécaniques compatibles avec une approche ‘matériau composite’. En effet, les propriétés mécaniques globales des matériaux composites, comme attendu, sont dépendantes des caractéristiques de cette interphase mais ne seront pas réduites par la présence de celle-ci notamment pour assurer la durabilité du matériau compositeA thermally self-healable carbon/epoxy interphase was designed based on Diels-Alder (D-A) thermally reversible covalent bonds. The D-A modified interphase was formed between maleimide groups grafted on carbon fiber surface and furan groups introduced into epoxy network. The self-healing ability was characterized by a micromechanical approach using the micro-droplet debonding test. In this work, carbon fiber surface underwent a three-step treatment to graft maleimide groups, including HNO3 oxidization, tetraethylenepentamine (TEPA) amination, and bismaleimide (BMI) grafting. The fiber surface physico-chemical modifications after each treatment step were characterized by microscopies (SEM, and AFM) and spectroscopies (XPS, and ATR-FTIR). The matrix modification was carried on mixing furfuryl glycidyl ether (FGE) into epoxy/amine network and the properties of modified matrix were studied by TGA, DSC, ATR-FTIR, and tensile tests. The reversible character of Diels-Alder bond was also followed by DSC, TGA, and NMR. The interfacial mechanical properties and the self-healing abilities of the D-A modified interphases, built by combining DGEBA-FGE/amine matrix with a serial of BMI-grafted carbon fibers tuned as a function of the oxidization time were investigated. At last, since FGE plays a double-role in D-A modified interfacial system, i.e. chain extender in epoxy network and self-healing agent in the interphase, the influences of FGE content in matrix on the mechanical properties of interphase and also on the mechanical properties of cured matrix were evaluated. As a consequence, this study allowed to achieve the best process to build a thermally self-healable carbon/epoxy interphase based on thermally reversible Diels-Alder covalent bonds. The formed interphase has not only the successive self-healable abilities but also the required mechanical properties. Additionally, the overall mechanical properties of the composite material based on this interphase will not be weakened significantly after the interfacial modifications
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Hunt, Richard K. "A transmission electron microscope characterization of sodium sulfate hot corrosion of silicon carbide fiber-reinforced lithium aluminosilicate glass-ceramic matrix composite." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA286164.
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Raman, Venkadesh. "A smart composite based on carbon fiber and epoxy matrix for new offshore wind-turbines. Multi-scale numerical and analytical modelings." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0016.
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Les structures intelligentes fondées sur des matériaux composites ont été développées pour surveiller les structures qui doivent fonctionner dans des applications industrielles exigeantes, dans des environnements difficiles comme c’est le cas de l’aéronautique, de l’aérospatiale, du génie civil, des centrales nucléaires et chimiques ...). L'étude actuelle est axée sur la suggestion d’un nouveau matériau composite intelligent qui peut être utilisé avec succès dans les pâles d’éoliennes offshore de nouvelle génération. En effet, pour accentuer leur rendement, les pales de nouvelle génération doivent dépasser une longueur de 100m, ce qui représente actuellement une cible hors d’atteinte étant donné que les matériaux composites constitutifs sont fondés sur des fibres de verre, notamment connues pour être lourdes et dépourvues de rigidité significative. Par conséquent, le passage aux fibres de carbone (plus légères et 3 fois plus rigides) devient obligatoire. Dans cette thèse, nous proposons la mise en place d'un matériau composite intelligent à base de fibres de carbone et de matrice époxy (ici appeler matériau parent). Les capteurs à fibre optique (FOS) et les capteurs à résistance quantique (QRS) seront utilisés pour la détection de déformation dans toute la structure. Ce choix devrait permettre une documentation précise et un envoi instantané d'informations critiques aux ingénieurs. Pour atteindre cet objectif de développement d'un nouveau matériau intelligent pour une application critique dans la production d’énergie éolienne offshore, nous avons choisi de proposer un document de recherche regroupant plusieurs aspects du sujet, résumés en 5 chapitres. La thèse est fondée sur des modélisations numériques et analytiques. Le document n'a pas l'ambition d'être exhaustif. Il est destiné à présenter une recherche pragmatique qui met l'accent sur la façon dont les domaines de faiblesse mécanique peuvent être diagnostiqués, quelles sont les solutions qui peuvent être suggérées et comment nous pouvons les soutenir, quelles sont les questions relatives à l'utilisation de capteurs intégrés et les résultats expérimentaux qui permettent l'évaluation du statut actuel de la performance du matériau et les moyens d’en améliorer les performancesSmart structures have been developed as to monitor structures that have to operate in demanding industrial applications with includes harsh environments (Aeronautics and aerospace, Civil engineering, nuclear and chemical power plants…), too. Current study is focused on the suggestion of new smart composite materials that can be successfully used for wind blade structures in offshore energy generation farms. Indeed, to bring expectable energy-generation performances, new generation wind blades have to exceed 100m length, which is a hardly achievable target given that actual constitutive composite materials are based on glass-fibers, that are notably known to be very heavy and lacking stiffness. Therefore, the switch to carbon fibers (lighter and stiffer) becomes mandatory. In this thesis, we propose the implementation of a smart composite material that is based on carbon fibers and epoxy matrix (here called parent material). Fiber Optic Sensors (FOS) and Quantum-Resistive Sensors (QRS) will be used for detection of over-strained areas all over the structure. This choice is expected to enable for accurate documentation and instant sending of critical information to engineers. To achieve this goal of development of a new smart material for a critical application in offshore wind generation, we have chosen to illustrate it in a research document that is grouping several aspects, summarized in 5 chapters. The thesis is conducted using numerical and analytical modelings. The document is not having the ambition to be exhaustive. It is intended to present a pragmatic research that emphasize how areas of mechanical weakness can be diagnosed, what are the solutions that can be suggested and how we can support them, what are the issues pertaining to the use of embedded sensors and some experimental results that give appraisal of current performance status and what could be future trends
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永正, 邵., and Yongzheng Shao. "Study on the effects of matrix properties on the mechanical properties of carbon fiber reinforced plastic composites." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902982/?lang=0, 2015. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902982/?lang=0.
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It was found that a significant improvement of mechanical properties of CFRPs can be achieved by the adjustment of the matrix properties such as toughness and CF/matrix adhesion via the chemical modification, as well as the physical modification by a small amount of cheap and environment-friendly nano fibers. Based on investigation of fracture mechanisms at macro/micro scale, the effects of matrix properties and nano fiber on the mechanical properties of CFRP have been discussed. Subsequently, the relationship has been characterized by a numerical model to show how to modulate the parameters of the matrix properties to achieve excellent fatigue properties of CFRP.博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Durkin, Craig Raymond. "Low-Cost Continuous Production of Carbon Fiber-Reinforced Aluminum Composites." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19857.
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The research conducted in this study was concerned with the development of low-cost continuous production of carbon fiber/aluminum composites. Two coatings, alumina and zirconia, were applied to the fibers to protect against interfacial degradation. They were applied using a sol-gel method and common metal salts. The fibers were infiltrated with molten aluminum using an ultrasound sonicator. The resultant composites were well-infiltrated and were tested in tension to determine their mechanical properties. Strengths were only 15-35% of the theoretical values predicted by the rule of mixtures. The composite microstructure revealed a sizable void fraction and that the fibers within the composites did not contain any coating on their surface. It was hypothesized that this was a result of few exposed graphite plane edges on the fiber surface, causing poor adhesion of the oxide coating to the fiber surface. To improve adhesion, an amorphous carbon coating was applied to the fiber surface, but still the oxide coatings were removed from the fibers upon infiltration. It was found, however, that the carbon coating on its own did strengthen the interface between the fiber and the aluminum.
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Boufaida, Zakariya. "Analyse des propriétés mécaniques de composites taffetas verre/matrice acrylique en relation avec les propriétés d’adhésion des fibres sur la matrice." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0108/document.
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Cette thèse est essentiellement consacrée à la caractérisation et à l’analyse des propriétés mécaniques de matériaux composites constitués d’un renfort taffetas verre et d’une résine acrylate (Elium®). Avant l’apparition de la résine Elium® sur le marché en 2013, les polymères acrylates n’étaient pas utilisés dans l’industrie des composites fibres longues. Dans le volet expérimental de la thèse, nous nous intéressons principalement à l’influence de l’ensimage (traitement de surface appliqué aux fibres pour favoriser l’adhésion de la matrice) sur le comportement mécanique de nos composites. En complément de différents essais mécaniques macroscopiques « classiques » (traction, flexion etc.), nous avons utilisé des techniques d’analyse locales fines (mesures de champ cinématique, microtomographie X, Microscopie Électronique à Balayage, nanoindentation…) qui nous ont permis de caractériser et d’étudier certains mécanismes locaux de déformation et d’endommagement. L’influence de l’ensimage sur les propriétés en fatigue a été mise en évidence grâce à des mesures d’autoéchauffement pour lesquelles nous avons développé un traitement original des données. A l’issue de nos investigations, nous avons pu quantifier le bénéfice qui résulte de l’utilisation d’un ensimage spécifiquement conçu pour favoriser l’adhésion d’un polymère acrylate sur des fibres de verre. Dans le volet « simulation numérique » de la thèse, nous avons modélisé le comportement mécanique de nos composites taffetas verre/matrice acrylate grâce au solveur spectral CraFT (Composite response and Fourier Transforms). Le détail des champs de contrainte et de déformation a été obtenu à l’échelle de la mésostructure et révèle une structuration périodique induite par la présence du renfort tissé. Une analyse quantitative a permis de vérifier que les champs de déformation qui ont été obtenus grâce au solveur CraFT sont en très bon accord avec des mesures réalisées par corrélation d’images. A partir du champ de contrainte, nous avons mis en évidence les régions de la mésostructure qui subissent les plus fortes sollicitations mécaniques. En visualisant par microtomographie X la structure interne d’éprouvettes précédemment déformées, nous avons pu établir le lien entre la localisation de l’endommagement au sein de la mésostructure et les régions de concentration de contrainte que la simulation numérique avait mises en évidenceThis thesis is devoted to the characterization and the analysis of the mechanical properties of composite materials made of a plain weave glass fiber reinforcement and an acrylic resin (Elium®). Before the commercialization of the Elium resin in 2013, acrylics polymers were not used in the composite industry. In the experimental part of this thesis, we mainly focused on the sizing effect (surface treatment of the fibers to enhance the bonding between the matrix and the fibers) on the mechanical behavior of our composites. The characterizations were carried out through classical macroscopic mechanical tests (tensile, bending, shearing…) but using metrological tools for local analysis (full-field strain measurements, X ray micro-tomography, Scanning Electron Microscopy, Nano-indentation etc.). We were able to study strain and damage phenomena at local scales. Fatigue properties of the sizing were highlighted by heat build-up experiments. To analyze these measurements, an original data treatment has been developed which makes clear the benefit of an acrylic sizing in order to enhance the bonding between glass fibers and our acrylic matrix. In the theoretical part of this thesis, we studied the mechanical behaviour of our glass fiber plain weave/acrylic resin composite through a numerical simulation based on the CraFT spectral solver (Composite response and Fourier Transforms). Local stress and strain fields were obtained at the mesoscopic scale. The strain field analysis shows a periodic structure induced by the presence of the plain weave reinforcement. By a quantitative study, a good agreement between the numerical strain field obtained by CraFT and the 3D-DIC experimental strain measurements was found. The numerical stress field analysis reveals regions were a high local stress occurs. Comparing with X ray micro-tomography observationsof the internal structure of previously loaded composite sampleswe noticed that the damages occurring inside the mesostructure are totally correlated with the local stress concentration revealed by CraFT numerical simulations
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Pawar, Prashant M. "Structural Health Monitoring Of Composite Helicopter Rotor Blades." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/273.
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Helicopter rotor system operates in a highly dynamic and unsteady aerodynamic environment leading to severe vibratory loads on the rotor system. Repeated exposure to these severe loading conditions can induce damage in the composite rotor blade which may lead to a catastrophic failure. Therefore, an interest in the structural health monitoring (SHM) of the composite rotor blades has grown markedly in recent years. Two important issues are addressed in this thesis; (1) structural modeling and aeroelastic analysis of the damaged rotor blade and (2) development of a model based rotor health monitoring system. The effect of matrix cracking, the first failure mode in composites, is studied in detail for a circular section beam, box-beam and two-cell airfoil section beam. Later, the effects of further progressive damages such as debonding/delamination and fiber breakage are considered for a two-cell airfoil section beam representing a stiff-inplane helicopter rotor blade. It is found that the stiffness decreases rapidly in the initial phase of matrix cracking but becomes almost constant later as matrix crack saturation is reached. Due to matrix cracking, the bending and torsion stiffness losses at the point of matrix crack saturation are about 6-12 percent and about 25-30 percent, respectively. Due to debonding/delamination, the bending and torsion stiffness losses are about 6-8 percent and about 40-45 percent after matrix crack saturation, respectively. The stiffness loss due to fiber breakage is very rapid and leads to the final failure of the blade. An aeroelastic analysis is performed for the damaged composite rotor in forward flight and the numerically simulated results are used to develop an online health monitoring system. For fault detection, the variations in rotating frequencies, tip bending and torsion response, blade root loads and strains along the blade due to damage are investigated. It is found that peak-to-peak values of blade response and loads provide a good global damage indicator and result in considerable data reduction. Also, the shear strain is a useful indicator to predict local damage. The structural health monitoring system is developed using the physics based models to detect and locate damage from simulated noisy rotor system data. A genetic fuzzy system (GFS) developed for solving the inverse problem of detecting damage from noise contaminated measurements by hybridizing the best features of fuzzy logic and genetic algorithms. Using the changes in structural measurements between the damaged and undamaged blade, a fuzzy system is generated and the rule-base and membership functions optimized by genetic algorithm. The GFS is demonstrated using frequency and mode shape based measurements for various beam type structures such as uniform cantilever beam, tapered beam and non-rotating helicopter blade. The GFS is further demonstrated for predicting the internal state of the composite structures using an example of a composite hollow circular beam with matrix cracking damage mode. Finally, the GFS is applied for online SHM of a rotor in forward flight. It is found that the GFS shows excellent robustness with noisy data, missing measurements and degrades gradually in the presence of faulty sensors/measurements. Furthermore, the GFS can be developed in an automated manner resulting in an optimal solution to the inverse problem of SHM. Finally, the stiffness degradation of the composite rotor blade is correlated to the life consumption of the rotor blade and issues related to damage prognosis are addressed.
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Charlier, Quentin. "Adhesion phenomena in thermoplastic composites based on acrylic matrices obtained by free radical polymerization." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI140.
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Ce mémoire de thèse s’intéresse aux phénomènes d’adhésion dans des composites à matrice thermoplastique obtenus par polymérisation radicalaire de mélanges réactifs. Après une courte introduction bibliographique sur les thématiques d’adhésion et d’adhérence, les propriétés générales des principaux éléments constitutifs des assemblages finaux sont étudiées séparément pour discuter de leur pertinence en vue d’une application composite. Une attention particulière est portée sur les systèmes réactifs acryliques à l’état liquide. L’étude se concentre ensuite sur les mécanismes réactionnels et l’évolution des propriétés des systèmes réactifs lors de la polymérisation. Ces problématiques sont de première importance pour anticiper les mécanismes gouvernant l’adhésion dans les composites obtenus mais aussi pour appréhender les potentielles problématiques à venir lors des étapes de mise en forme. Enfin, une étude est spécifiquement dédiée au cas de l’adhésion entre matrice acrylique et fibres de verre dans des composites à fibres de renfort continues. Les propriétés à l’interface verre/acrylique ont été évaluées à l’échelle microscopique dans des systèmes modèles et à l’échelle macroscopique dans des composites unidirectionnels, c'est à dire pouvant les défauts d’adhésion générés lors de la mise en forme. L’ensemble de ces résultats permet de se positionner quant à l’utilisation de solutions acryliques thermoplastiques pour des applications composites structurauxThese PhD research works focus on adhesion phenomena involved in thermoplastic composites based on acrylic matrices obtained by free radical polymerization. After a short bibliographic section introducing some basics on adhesion phenomena and practical adhesion measurements, properties of elementary constituents are assessed to discuss their relevancy for composite applications. Special attention is paid to acrylic reactive systems and properties of acrylic resins at liquid state. Then, the reaction mechanisms involved in free radical polymerization are detailed. The changes in acrylic system properties during polymerization are investigated to anticipate further processing-related issues. At last, a study is dedicated to the assessment of interfacial adhesion between glass fiber and acrylic matrices in fiber reinforced composites. Interfacial properties are characterized at microscale in model systems and at macroscale in real-sized composites, i.e. integrating process-induced defects. From overall results, the relevancy of acrylic thermoplastic solutions for structural composite applications is discussed
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Oliveira, Nunes Andréa. "Composites renforcés à fibres de carbone : récupération des fibres par vapo-thermolyse, optimisation du procédé." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0006/document.
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La demande mondiale en fibre de carbone est estimée à 89 000 tonnes en 2020. Une quantité croissante de déchets de composites renforcés à fibres de carbone (PRFC) est donc attendue. Le recyclage des fibres de carbone, produits de forte valeur ajoutée, contenues dans les composites, présente des avantages économiques et environnementaux qui sont aujourd'hui la force motrice pour le développement des filières de recyclage. L'objectif est de récupérer les fibres de carbone afin de pouvoir envisager un réemploi dans d'autres applications. Leurs propriétés mécaniques et structurales doivent alors être le plus proche possible de celles des fibres neuves. C'est dans ce but que le procédé de vapo-thermolyse a été développé au sein du laboratoire RAPSODEE. La vapo-thermolyse est le procédé qui combine la pyrolyse et la vapeur d'eau surchauffée à pression ambiante afin de décomposer la matrice organique du composite. Le travail a consisté à effectuer une étude de l'échelle laboratoire à l'échelle pilote sur la valorisation des composites à fibres de carbone par le procédé de vapo-thermolyse. Notre étude se focalise sur les composites thermoplastiques provenant des chutes de fabrication. Deux types de composites, disponibles en industrie, avec les matrices polyamide 6 et polysulfure de phénylène ont été utilisées. Les analyses thermogravimétriques et l'étude cinétique ont permis une compréhension initiale du comportement thermique des composites et ont prouvé l'efficacité de la présence de la vapeur d'eau. A l'échelle pilote, des plans d'expériences ont été effectués pour déterminer les meilleures conditions opératoires du procédé de vapo-thermolyse, en regardant l'efficacité de la dégradation des résines polymériques et la qualité des fibres obtenues. Les fibres récupérées avec les conditions opératoires optimales sont propres, régulières et similaires aux fibres neuves. Elles conservent plus de 80 % de leur résistance à la traction initiale. Les liquides et gaz sortants du procédé ont été identifiés et quantifiés. A la fin, une analyse du cycle de vie (ACV) a permis de comparer les impacts environnementaux d'un scénario sans recyclage des composites et un autre avec recyclage par le procédé de vapo-thermolyse. Cette étude montre que la valorisation des composites par récupération des fibres de carbone, amène des avantages évidents d'un point de vue environnementalThe global demand for carbon fiber is forecast to rise to 89,000 tonnes by 2020, therefore an increasing amount of carbon fiber reinforced polymer (CFRP) waste is expect to be generated. Recycling of carbon fibers, a high value added material, from the composite waste offers both environmental and economic incentives for the development of recycling routes. The aim is to recover the carbon fibers, as close as possible to their initial state, in order to envisage a reuse in other applications. For this purpose, steam-themolysis has been developed at RAPSODEE Laboratory. Steam-thermolysis is a process that combines pyrolysis and superheated steam at atmospheric pressure to decompose the organic matrix of the composite. The work consists of a study of recovering carbon fibers by steam-thermolysis of the composites at both the laboratory and pilot scale. In this work the samples under investigation includes thermoplastic composites from manufacturing cut-offs. Two commercially available composites of polyamide and polyphenylene sulfide resins were studied. Thermo-gravimetric analyses and kinetic studies were conducted to understand the thermal behavior of the samples and to prove the efficiency of the steam-thermolysis compared to conventional pyrolysis. At the pilot scale, an experimental design was carried out to determine the best possible operational conditions of the steam-thermolysis process in terms of the removal efficiency of the polymer matrix and the quality of the recovered carbon fibers. The carbon fibers recovered from the optimized steam-thermolysis process presented a resin free and uniform surface. They retained over 80 % of their original tensile strength. The outgoing liquids and gases of the process were identified and quantified. Finally, a life cycle assessment (LCA) was performed to compare a scenario without recycling with one where the composites are recycled by steam-thermolysis. According to this study, the recycling of CFRP, with recovery of carbon fibers, provides clear environmental advantages
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Jablonská, Markéta. "Ověření skutečných fyzikálně-mechanických parametrů kompozitního materiálu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240445.
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Diploma thesis deals with composite materiál and it is dedicated to steel fiber concreat. The thesis focuses on verification of mechanical parameters of the steel fiber concrete. Especially on the compressive (tensile) strength at first cracking and the compressive strength in cracked state. Testing was conducted on concrete different tensile with 30 kg on m3 steel fibers KrampeHarex DE 50/1,0 N. The thesis is divided into theoretical and experimental part.
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Beguinel, Johanna. "Interfacial adhesion in continuous fiber reinforced thermoplastic composites : from micro-scale to macro-scale." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI051.
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L’intérêt croissant de l’industrie pour les matériaux composites thermoplastiques est motivé par leurs propriétés de thermoformabilité, de recyclabilité ainsi que leurs capacités de cadences de production élevées. Le développement de matériaux pré-imprégnés thermoplastiques, apparus dès les années 1980, s’est imposé comme un moyen efficace de contourner les fortes viscosités des polymères utilisés en réduisant la distance d’écoulement des polymères à l’état « fondu ». Cette étude s’est plus particulièrement intéressée au développement de composites à base de tissus de verre et de carbone pré-imprégnés par un latex acrylique, le TPREG I. En outre, les propriétés mécaniques élevées des matrices acryliques, alliées à un coût relativement faible, en font un matériau intéressant, de nature à permettre un saut technologique dans la conception et la fabrication de composites structuraux à matrice organique. Notre étude s’est concentrée sur la mesure de l’adhésion à l’interface fibre/matrice acrylique car cette région est au cœur du transfert de charge de la matrice vers les fibres et conditionne donc les propriétés mécaniques du composite. Nous avons choisi d’évaluer l’adhésion interfaciale en combinant des analyses de mouilllage avec des tests mécaniques aux échelles microscopique et macroscopique. Le test micromécanique de la microgoutte permet de mettre en évidence le rôle central de l’ensimage des fibres sur la contrainte de cisaillement interfaciale. L’adhésion thermodynamique, déterminé par des mesures d’énergie de surface, est en accord avec la contrainte de cisaillement et souligne l’influence de la polarité de l’ensimage. A l’échelle macroscopique, les essais de traction hors-axe sur composites unidirectionnels permettant de solliciter l’interface en cisaillement quasi-plan ont mis en exergue une corrélation entre les échelles micro et macro. L’étude a également permis de dégager une forte augmentation de l’adhésion grâce à une modification de la matrice acrylique, ainsi qu’une dégradation des propriétés interfaciales à l’échelle micro par vieillissement hydrolytique. Cette étude constitue une première base de données concernant les propriétés interfaciales de composites thermoplastiques acryliques et démontre l’importance d’une étude multi-échelles dans la conception de nouveaux compositesThe present study was initiated by the development of a new processing route, i.e. latex-dip impregnation, for thermoplastic (TP) acrylic semi-finished materials. The composites resulting from thermocompression of TPREG I plies were studied by focusing of interfacial adhesion. Indeed the fiber/matrix interface governs the stress transfer from matrix to fibers. Thus, a multi-scale analysis of acrylic matrix/fiber interfaces was conducted by considering microcomposites, as models for fiber-based composites, and unidirectional (UD)macro-composites. The study displayed various types of sized glass and carbon fibers. On one hand, the correlation between thermodynamic adhesion and practical adhesion, resulting from micromechanical testing, is discussed by highlighting the role of the physico-chemistry of the created interphase. Wetting and thermodynamical adhesion are driven by the polarity of the film former of the sizing. On the other hand, in-plane shear modulus values from off-axis tensile test results on UD composites are consistent with the quantitative analyses of the interfacial shear strength obtained from microcomposites. More specifically, both tests have enabled a differentiation of interface properties based on the fiber sizing nature for glass and carbon fiber-reinforced (micro-)composites. The study of overall mechanical and interface properties of glass and carbon fiber/acrylic composites revealed the need for tailoring interfacial adhesion. Modifications of the matrix led to successful increases of interfacial adhesion in glass fiber/acrylic composites. An additional hygrothermal ageing study evidenced a significant loss of interfacial shear strength at micro-scale which was not observed for UD composites. The results of this study are a first step towards a database of relevant interface properties of structural TP composites. Finally, the analyses of interfaces/phases at different scales demonstrate the importance of a multi-scale approach to tailor the final properties of composite parts
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Ayari, Houssem. "Modélisation micromécanique de l’effet des chargements cycliques et de la vitesse de déformation sur l’endommagement de l’interface fibre-matrice dans les composites SMC." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE033.
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L’objectif de cette étude est de modéliser les réponses mécaniques de deux matériaux composites SMC soumis à des sollicitations de types fatigue et dynamique. Pour mener à bien cet objectif, une étude bibliographique a été menée sur les propriétés et la modélisation des comportements dynamique et cyclique des matériaux composites à renforts discontinus. L’endommagement à l’interface fibre-matrice apparait comme étant le phénomène moteur dans les composites SMC dont le comportement peut être qualifié d’élastique endommageable. Ainsi, un modèle micromécanique basé sur une technique d’homogénéisation dans lequel un critère local statistique de rupture à l’interface fibre-matrice a été introduit a été développé et a permis de traduire le comportement monotone des SMC étudiés a été développé. Les résultats expérimentaux extraits de la littérature ont permis l’extension du modèle micromécanique aux cas des chargements cycliques et dynamiques. Quatre approches complémentaires tous fondé sur la prise en compte des dommages interfaciaux ont été développées. Notamment, le critère a été formulé en fonction des contraintes limites normales et tangentielles locales, des vitesses de chargement locales correspondantes et du nombre de cycle afin de prédire le comportement dynamique et cyclique. Ainsi, les réponses mécaniques sous chargement monotone, la dégradation progressive des propriétés mécaniques sous chargement dynamique et cyclique et la durée de vie des deux composites SMC étudiés ont pu être prédites avec une bonne concordance avec les résultats expérimentaux obtenus à l’échelle microscopique et macroscopiqueThe aim of this study is to model the mechanical behavers of two SMC composite materials subjected to fatigue and dynamic loadings. To achieve this goal, a bibliographic study was carried out on the modeling of the dynamic and cyclic behavior of SMC composite. Fiber-matrix interface decohesion is a main local damage mechanism in SMC composites. This phenomenon is introduced in the Mori and Tanaka approach through a local damage criterion which defines step by step the number of micro-cracks to be introduced in the homogenization scheme of this model during loading until final failure.Indeed, this model allows predicting the monotonic behavior of the studied SMCs. The experimental results, extracted from literature, have allowed the extension of the micromechanical model in the cases of cyclic and dynamic loadings. Four complementary approaches, all based on the consideration of interfacial damage, have been developed as a function of the local normal and tangential stress values, the corresponding strain rate and the number of cycles.Thus, the mechanical response under monotonic loading at different strain rates from quasi-static to dynamic was also predicted. For the fatigue loading, the progressive degradation of the mechanical properties and the fatigue lifetime of the two investigated SMC composites were predicted in good agreement with the experimental results obtained at microscopic and macroscopic scale
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Poussines, Laurence. "Développement de nouveaux matériaux pour l'infusion de composites." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0132/document.
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Ce travail de thèse vise à adapter un système polymère au procédé d’élaboration par infusion d’une structure en matériaux composite pour fuselage d’avion. Ce système doit répondre à certaines exigences de viscosité, de température d’infusion, de stockage mais également de prix. La méthodologie mise en place consiste à s’approprier le procédé de mise en oeuvre afin de valider le choix des résines, de les caractériser à l’état initial et enfin d’étudier leur durabilité vis-à-vis d’un vieillissement hygrothermique. La caractérisation des propriétés a mis en évidence des comportements différents à l’état initial en termes de transition vitreuse, résilience et viscosité. L’étude du vieillissement hygrothermique montre une chute des propriétés fortement liée à l’évolution chimique des réseaux polymères qui a pour origine majeure l’hydrolyse de plusieurs liaisons. Enfin, un test d’adhérence est mis en place afin d’évaluer l’interface fibre/résine. Ce test a permis d’estimer les différents traitements de surface effectués sur les fibresThe work presented in this thesis was done to adapt a polymer to selected elaboration process by infusion of a composite material structure for an aircraft fuselage. The polymer system must meet certain requirements such as viscosity, infusion temperature, storage but also the price. Our methodology is to understand the process putting into practice in order to validate the resins choice, to characterize the initial state and the study their sustainability towards a hydrothermal ageing. Properties characterization showed different behaviours in initial state, in terms of glass transition, resilience and viscosity. The study of hydrothermal ageing reveals a drop properties closely related to the chemical evolution of polymer networks which has for major origin multiple links hydrolysis. At least an adherence test is carried out to assess the interface fiber/resin. This test was used to estimate the different surface treatments on the fiber
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Vazquez, Calnacasco Daniel. "All-Oxide Ceramic Matrix Composites : Thermal Stability during Tribological Interactions with Superalloys." Thesis, Luleå tekniska universitet, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85513.
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The challenges faced in today’s industry require materials capable of working in chemically aggressive environments at elevated temperature, which has fueled the development of oxidation resistant materials. All-Oxide Ceramic Matrix Composites (OCMC) are a promising material family due to their inherent chemical stability, moderate mechanical properties, and low weight. However, limited information exists regarding their behavior when in contact with other high-temperature materials such as superalloys. In this work three sets of tribological tests were performed: two at room temperature and one at elevated temperature (650 °C). The tests were performed in a pin-on-disk configuration testing Inconel 718 (IN-718) pins against disks made with an aluminosilicate geopolymeric matrix composite reinforced with alumina fibers (N610/GP). Two different loads were tested (85 and 425 kPa) to characterize the damage on both materials. Results showed that the pins experienced ~ 100 % wear increase when high temperature was involved, while their microstructure was not noticeably affected near the contact surface. After high temperature testing the OCMC exhibited mass losses two orders of magnitude higher than the pins and a sintering effect under its wear track, that led to brittle behavior. The debris generated consists of alumina and suggests a possible crystallization of the originally amorphous matrix which may destabilize the system. The data suggests that while the composite’s matrix is stable, wear will not develop uncontrollably. However, as soon as a critical load/temperature combination is attained the matrix is the first component to fail exposing the reinforcement to damage which drastically deteriorates the integrity of the component.
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Duning, Solomon George. "3D Textile PMC Damage Evolution: Effects of Fiber Volume Fraction and Morphology Variation." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461854275.
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Andrade, Rodrigo Rocha. "Influência da proporção de partículas de reforço nas propriedades mecânicas de um compósito experimental." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/6733.
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Previous studies show that there is effective interaction between silanized glass fiber and resin matrix formed by methacrylates; However, there is no information on the use of milled glass fiber and the resin incorporated as a filler particle in order to obtain better mechanical properties in composites for the manufacture of intraradiculares pins. The objectives of this study were to evaluate the influence of different types (barium silicate and / or glass fiber powder) and charged particle concentrations in flexural strength, resistance to diametrical and Knoop microhardness traction, an experimental composite composed of 47.5% loading of particles, 30 % glass fiber and resin matrix of 22.5% (BISGMA and TEGDMA (1: 1)); evaluate the morphology of the filler particles and their interaction with the experimental composite in scanning electron microscopy. For producing glass fiber powder, fibers were milled in a mortar grinder / pestle, and then six experimental groups (N = 10) were prepared, varying the ratio of the kind of charged particle: CONTROL - 47.5% barium silicate and 0.0% glass fiber powder; G7.5 - 40.0% barium silicate and 7.5% glass fiber powder; G17.5 - barium silicate 30.0% and 17.5% glass fiber powder; G27.5 - barium silicate 20.0% and 27.5% glass fiber powder; G37.5% - 10.0% barium silicate and 37.5% glass powder vibrates; G47.5% - 0.0% barium silicate and 47.5% glass fiber powder. Cylindrical samples (3 mm x 6 mm) were produced for the diametral tensile strength test, and samples in bar format (25 mm x 2 mm x 2 mm) for flexural and microhardness knoop throws. Resistance tests were performed at 0.5 mm / min on a universal testing machine (Instron 5965). The Knoop microhardness test was made 0.2 KHN (200 g) for 40 seconds at a hardness tester (Shimadzu HMV2). After verification of normality and homogeneity of data distribution with the Kolmogorov-Smirnov test, the data were submitted to ANOVA and Tukey tests (α = 0.05). Statistical analysis demonstrated (p = 0.001): flexural strength: CONTROL - 259.91 ± 26.01a; G7.5 - 212.48 ± 35.91b; G17.5 - 177.63 ± 24.88bc; G27.5 - 166.58 ± 30.84c; G37.5 - 92.08 ± 6.46d; G47.5 - 80.60 ± 17.89d; Diametral tensile strength: CONTROL - 31.05 ± 2.98a; G7.5 - 14.55 ± 3.70b; G27.5 - 12.65 ± 3.34bc; G17.5 - 8.62 ± 3.51cd; G47.5 - 8.04 ± 1.63d; G37.5 - 6.63 ± 2.85d; Knoop microhardness: CONTROL - 75.69 ± 12.19a; G37.5 - 67.62 ± 1.79ab; G27.5 - 65.72 ± 2.01b; G47.5 - 64.06 ± 1.61b; G7.5 - 62.79 ± 2.79b; G17.5 - 59.87 ± 2.33b. The gradual substitution a percentage of the barium silicate glass fiber powder in a glass fiber reinforced composite trial resulted in a decrease in the results of flexural strength, diametral tensile strength and Knoop hardness. Morphologically, glass fiber powder made up of particles with heterogeneous and larger than the particle of barium silicate. The interaction of the glass fiber powder to the resin matrix and fiber reinforcement have not proved effective.
Estudos prévios demonstram haver efetiva interação entre fibra de vidro silanizada e matriz resinosa formada por metacrilatos; porém, inexiste informação sobre a utilização da fibra de vidro moída e incorporada à resina como partícula de carga, com a finalidade de obter melhores propriedades mecânicas em compósitos destinados à fabricação de pinos intraradiculares. Os objetivos deste trabalho foram: avaliar a influência de diferentes tipos (silicato de bário e/ou pó de fibra de vidro) e concentrações de partícula de carga na resistência flexural, resistência à tração diametral e microdureza Knoop, de um compósito experimental composto por 47,5 % de partículas de carga, 30 % de fibra de vidro e 22,5 % de matriz resinosa (BISGMA e TEGDMA (1:1)); avaliar a morfologia das partículas de carga e sua interação com o compósito experimental em microscopia eletrônica de varredura. Para produção do pó de fibra de vidro, fibras foram moídas em um moinho almofariz/pistilo e então seis grupos experimentais (N = 10) foram confeccionados, variando a proporção do tipo de partícula de carga: CONTROLE – 47,5 % silicato de bário e 0,0 % pó de fibra de vidro; G7,5 – 40,0 % silicato de bário e 7,5 % pó de fibra de vidro; G17,5 – 30,0 % silicato de bário e 17,5 % pó de fibra de vidro; G27,5 – 20,0 % silicato de bário e 27,5 % pó de fibra de vidro; G37,5 % - 10,0 % silicato de bário e 37,5 % pó de vibra de vidro; G47,5 % - 0,0 % silicato de bário e 47,5 % pó de fibra de vidro. Amostras cilíndricas (3 mm x 6 mm) foram produzidas para o teste de resistência à tração diametral, e amostras em formato de barra (25 mm x 2 mm x 2 mm) para os testes de resistência flexural e microdureza knoop. Os testes de resistência foram executados a 0,5 mm/min em máquina de ensaios universais (Instron 5965). O teste de microdureza knoop foi feito a 0,2 KHN (200 g) por 40 segundos em um durômetro (HMV2 Shimadzu). Após verificação de normalidade e homogeneidade de distribuição dos dados com o teste Kolmogorov-Smirnov, os dados foram submetidos aos testes ANOVA e Tukey (α=0,05). Análises estatísticas demonstraram (p=0,001): resistência flexural: CONTROLE - 259,91±26,01a; G7,5 - 212,48±35,91b; G17,5 - 177,63±24,88bc; G27,5 - 166,58±30,84c; G37,5 – 92,08±6,46d ; G47,5 – 80,60±17,89d; Resistência à tração diametral: CONTROLE – 31,05±2,98a; G7,5 – 14,55±3,70b; G27,5 – 12,65±3,34bc; G17,5 – 8,62±3,51cd; G47,5 – 8,04±1,63d ; G37,5 – 6,63±2,85d; Microdureza Knoop: CONTROLE – 75,69±12,19a; G37,5 – 67,62±1,79ab; G27,5 – 65,72±2,01b; G47,5 – 64,06±1,61b; G7,5 – 62,79±2,79b; G17,5 – 59,87±2,33b. A substituição gradativa em percentual do silicato de bário pelo pó de fibra de vidro em um compósito experimental reforçado com fibra de vidro resultou em queda nos resultados de resistência flexural, tração diametral e microdureza knoop. Morfologicamente, a partícula de pó de fibra de vidro apresentou-se heterogênea e com tamanho maior que a partícula do silicato de bário. A interação do pó de fibra de vidro com a matriz resinosa e o reforço de fibra não se mostraram efetivos.
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Fontaine, Pauline. "Traitement thermique de recyclage appliqué aux composites carbone/PEEK et aux mélanges de composites renforcés carbone. Solutions alternatives de valorisation des fibres recyclées." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2020. http://www.theses.fr/2020EMAC0015.
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Les composites renforcés à fibres de carbone (CRFC) sont des matériaux de haute technicité appliqués à de nombreux domaines, du sport à l’aéronautique. Cette dernière décennie a vu leur demande croitre continuellement, générant en conséquence une augmentation du volume de déchets. Incités par les directives Européennes sur la gestion des déchets, des traitements thermiques de recyclage industriel ont été développés afin de récupérer les fibres de carbone issues des CFRC, principalement à matrice thermodurcissable. Actuellement, les CRFC en développement et/ou de dernières générations, utilisent des matrices thermostables telles que le Poly Ether Ether Cétone (PEEK). Une partie des travaux de thèse consiste à étudier la faisabilité de recyclage de ce composite thermostable, seul et en mélange avec d’autres types de composites à matrice thermodurcissable et thermoplastique. Un pilote semi-industriel a été employé sous atmosphères inerte (pyrolyse) et réactives (vapo-thermolyse et air). Les premiers résultats sur des mélanges ont montré que sous atmosphère inerte la récupération des fibres de carbone issues des matrices thermostables est quasi impossible. A l’inverse, les essais sur les composites PEEK en atmosphères oxydantes permettent l’extraction de la fibre mais induisent des modifications morphologiques et chimiques de la surface ainsi qu’une réduction de la résistance en traction. Les travaux de thèse se focalisent également sur des solutions alternatives de valorisation des fibres de carbone recyclées. Ces fibres ont été recouvertes de nanocellulose en tant qu’agent d’ensimage, en vue de leur réutilisation dans de nouvelles formulations. La perte de propriétés mécaniques induite par le recyclage a été partiellement compensée par ce traitement de surface. Des fibres recyclées ont également été incorporées dans un composite à renfort naturel de jute et matrice PA6 dans le but de créer un composite hybride offrant des propriétés équilibrées en termes de résistance, prix et impact écologiqueCarbon Fiber Reinforced Composites (CFRC) are high technical materials applied in various fields from sports to aeronautics. During the last decade, the demand of CFRC has extended significantly resulting in increasing the volume of composite waste generated each year. Incited by European directives, thermal recycling treatments have been developed at industrial scale to recover carbon fibers, mostly from thermosetting composites. Nowadays CFRP in development used thermoresistant resins such as Poly Ether Ether Ketone (PEEK). Part of this work is to study the recycling feasibility of this type of CFRP alone and mixed with thermosetting and thermoplastics matrix based composites. Semi-industrial pilot was used in inert (pyrolysis) and reactive (steam-thermolysis, oxydation) atmosphere conditions. First results of mixture perform in nitrogen have revealed that inert atmosphere cannot allow the recovery of carbon fibers from thermoresistant resins. On the contrary trials on PEEK in oxydative atmospheres enable the extraction of fiber, but induce morphological and chemical modifications and tensile strength reduction. New approach on the recycled carbon fiber valorization have also been studied. These fibers have been coated by nanocellulose as sizing agent for their reuse in new composite formulations. Mechanical properties loss induce by recycling have been offset thank to this surface treatment. Recycled fibers was also incorporate in jute/PA6 composite to create a hybrid composite with balance properties in terms of strength, price and environmental impact
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Lepenies, Ingolf G. "Zur hierarchischen und simultanen Multi-Skalen-Analyse von Textilbeton." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1231842928873-71702.
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Die Arbeit widmet sich der Simulation und der Prognose des Materialverhaltens des Hochleistungsverbundwerkstoffes Textilbeton unter Zugbeanspruchungen. Basierend auf einer hierarchischen mechanischen Modellbildung (Multi-Skalen-Analyse) werden die Tragmechanismen des Verbundwerkstoffes auf drei Strukturebenen abgebildet. Damit lassen sich die den Verbundwerkstoff charakterisierenden mechanischen Kenngrößen aus experimentell ermittelten Kraft-Verschiebungs-Abhängigkeiten ableiten. Diese Kenngrößen sind mit heutiger Messtechnik nicht direkt experimentell bestimmbar. Es wird ein Mikro-Meso-Makro-Prognosemodell (MMM-Prognosemodell) für Textilbeton entwickelt, das basierend auf der Simulation des Mikrostrukturverhaltens das makroskopische Materialverhalten prognostiziert. Die Grundlage dafür bildet die qualitative und quantitative Bestimmung der Verbundeigenschaften zwischen der Filamentbewehrung und der einbettenden Matrix. Für das Verbundverhalten von Rovings in einer Feinbetonmatrix wird, ausgehend von einer Rovingapproximation mit superelliptischem Querschnitt, die partielle Imprägnierung des Rovings und die daraus resultierende Verbundwirkung identifiziert und simuliert. Auf Grundlage der mikro- und mesomechanischen Modelle sowie der Kalibrierung und Verifizierung des MMM-Prognosemodells durch die Simulation von Filament- und Rovingauszugsversuchen wird das makroskopische Zugverhalten von Textilbeton mit Mehrfachrissbildung prognostiziert. Die numerischen Ergebnisse werden durch die Ergebnisse der experimentellen Dehnkörperversuche validiert. Das MMM-Prognosemodell für Textilbeton wird im Rahmen einer hierarchischen Multi-Skalen-Analyse auf Zugversuche von Textilbetonbauteilen angewendet. Weiterhin wird die Verstärkungswirkung einer Textilbetonschicht an Stahlbetonbauteilen unter Biegebeanspruchung zutreffend simuliert. Es wird das nichtlineare Bauteilverhalten abgebildet, wobei die Bauteildurchbiegung, die effektiven Rovingbeanspruchungen und die Beanspruchungen der Filamente im Roving abgebildet werdenThe present work deals with the simulation and the prediction of the effective material behavior of the high performance composite textile reinforced concrete (TRC) subjected to tension. Based on a hierarchical material model within a multi scale approach the load bearing mechanisms of TRC are modeled on three structural scales. Therewith, the mechanical parameters characterizing the composite material can be deduced indirectly by experimentally determined force displacement relations obtained from roving pullout tests. These parameters cannot be obtained by contemporary measuring techniques directly. A micro-meso-macro-prediction model (MMM-PM) for TRC is developed, predicting the macroscopic material behavior by means of simulations of the microscopic and the mesoscopic material behavior. The basis is the qualitative and quantitative identification of the bond properties of the roving-matrix system. The partial impregnation of the rovings and the corresponding varying bond qualities are identified to characterize the bond behavior of rovings in a fine-grained concrete matrix. The huge variety of roving cross-sections is approximated by superellipses on the meso scale. The macroscopic behavior of TRC subjected to tension including multiple cracking of the matrix material is correctly predicted on the basis of the micro- and meso-mechanical models. The calibration and verification of the MMM-PM is performed by simulations of roving pullout tests, whereas a first validation is carried out by a comparison of the numerical predictions with the experimental data from tensile tests. The MMM-PM for TRC is applied to tensile tests of structural members made of TRC. Furthermore, a steel-reinforced concrete plate strengthened by a TRC layer is accurately simulated yielding the macroscopic deflection of the plate, the mesoscopic stress state of the roving and the microscopic stresses of the filaments
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Sbiai, Adil. "Matériaux composites à matrice époxyde chargée par des fibres de palmier dattier : effet de l’oxydation au tempo sur les fibres." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0043/document.
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A travers cette thèse, nous avons pu valoriser les rejets agricoles du palmier dattier (Phoenix L. dactylifera) (fibres issues des folioles) par leur introduction comme renfort fibreux dans la préparation des biocomposites à matrice polyépoxyde (DGEBA/IPD). Le but de la première partie de la thèse était l’étude de la modification chimique des fibres de palmier par oxydation au 2,2, 6,6–tétraméthylpipéridine-1-oxyle (TEMPO). Le suivi cinétique et la topologie de la réaction, ainsi que la caractérisation des fibres à l’état brut et à l’état oxydé, ont été aussi étudiés. Un modèle cinétique original a été proposé ensuite rendant compte du caractère hétérogène de cette réaction chimique. La deuxième partie était consacrée à l’étude cinétique et rhéocinétique de la polymérisation du système DGEBA/IPD seul et en présence de fibres brutes et oxydées. Parallèlement, l’étude thermique de la polymérisation du réseau final a été également réalisée. La dernière partie avait comme but l’étude des propriétés mécaniques aux petites et grandes déformations de ces composites et mettre en évidence l’effet de l’oxydation des fibres sur ces propriétés. D’autre part, le suivi de mise en forme par RTM (moulage par transfert de résine) a montré un effet positif de l’oxydation sur le déroulement de l’injection. Une meilleure mouillabilité du mat des fibres oxydées par la résine est à l’origine de l’amélioration du procédéTo increase in value the agricultural waste products of the date palm tree -phoenix dactylifera l-, especially the fibers from the leaflets, their use as filler in polyepoxide matrix (dgeba / ipd) was investigated to prepare new bio-based composites. Our goal in the first part is to study the chemical modification of palm fiber by oxidation mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl (tempo). The kinetic and the topology of the reaction, as well as the characterization of fibres in rough and oxidized state, were also studied. An original kinetic model was proposed taking into account the heterogeneous character of this chemical reaction. The second part was devoted to study the kinetics and rheokinetic of the polymerization of dgeba / ipd with and without modified and unmodified fibers. This enabled to show the effect of the introduction of the date palm tree fibers (oxidized and non oxidized) on the composite formation. The thermal properties of the prepared composites were also investigated in this part of work. In the last part of this work, the mechanical properties of these composites were investigated and enabled to highlight the effect of the fibers oxidation on these properties. In addition, the effect of oxidation on the course of the injection during the rtm process (moulding by transfer of resin) was investigated. A positive effect of the oxidation of the fibers on the course of the injection was obtained and was attributed to the higher wettability of oxidized fibres by the resin
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Chapoullie, Cedric. "Analyse/Synthèse tridimensionnelle de textures fibreuses." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0100/document.
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Cette thèse s‘inscrit dans le contexte de l‘étude de matériaux fibreux tissés et traite de l‘analyse morphologique de leur texture et de la simulation des arrangements des fibres dans un fil. Le volet « analyse » consiste à extraire des données caractérisant la géométrie des fibres et des fils composant le renfort tissé et s‘appuie sur des images tridimensionnelles issues de tomographies rayon X à haute résolution. Une chaine de traitement d‘images visant à séparer et identifier les fils et les fibres est proposée. Elle s‘appuie sur un algorithme de labellisation du fil et des fibres. Les caractéristiques telles que les diamètres et les orientations de fibres et la densité locale de fibres dans le fil sont ensuite calculées. Le volet « simulation » vise à générer un renfort fibreux « virtuel ». Un algorithme fondé sur la résolution de modèles dynamiques permet de placer au sein d‘un fil, des objets représentant les fibres tout en respectant des contraintes issues des paramètres issus du volet « analyse » ou choisis arbitrairement par l‘utilisateur. L‘ensemble des fibres composant le fil sont alors synthétisés en respect de ces contraintes. Ces deux volets sont appliqués avec succès à la caractérisation et à la synthèse de renforts fibreux de composites thermostructuraux. Les caractéristiques géométriques, estimées sur des tomographies à haute résolution, font ressortir des phénomènes tels que le cisaillement intra fils. La synthèse permet de simuler le placement de fibres à partir de paramètres géométriques obtenus à haute résolution, au sein d‘un fil dont l‘enveloppe est obtenue à basse résolution et donc sur une longueur plus représentative du tissageThe aim of this work is to study fibrous woven materials and to develop morphological analysis of their texture enabling simulation of fibrous layout in yarns. The ―analysis‖ stage consists in data extraction to characterize the geometry of fibers and yarns constituting the woven material, based on tridimensional images generated by high resolution X-ray tomography. An image processing workflow to separate and identify fibers and yarn is proposed. Then, diameters, fiber orientations and local fiber density in yarns are computed. The ―simulation‖ stage targets to generate virtual fibrous materials. An algorithm based on the resolution of a dynamic model allows placing objects representing fibers into a yarn. It uses as input the characteristic parameters previously extracted in the analysis stage or arbitrarily chosen ones. Consequently, all fibers are synthesized according to these constraints. These two stages are successfully applied to characterize and synthesize woven ceramic matrix composites. Geometrical characteristics, extracted from the high-resolution tomographic images, highlight yarn phenomena like shearing planes. The synthesis simulates fibers placement, merging geometrical parameters extracted on high and low resolution. Indeed, using fiber parameters extracted from high resolution images and yarn envelopes from low resolution ones enable generating a result with a more representative woven length
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Cozza, Alessandro. "Bond properties of SRG anchors employed to improve the effectiveness of SRG/FRCM composites." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
Fiber reinforced cementitious matrix (FRCM) composites represent a newly-developed promising alternative to traditional materials for strengthening and retrofitting reinforced concrete and masonry structures. FRCM composites present several advantages with respect to fiber reinforced polymers (FRP) composites. However, while FRP composites have been extensively studied in the last decades and several design guidelines and analytical formulations are available, FRCM composites are still in their infancy and very few data are present in the literature. Thus, another issue that should be solved regards the stated need for the anchorage systems to improve FRP and FRCM strength in situations where debonding or lack of development length is a problem.
In this study, the effectiveness of the anchorage system and the interaction with an externally bonded FRCM were studied on both concrete beams and masonry columns. The columns and beams were tested until failure condition in the Laboratory of Structural and Geotechnical Engineering (DICAM – LISG) of the University of Bologna, via del Lazzaretto 15/5, Bologna.
Test parameters considered for this study are: density of steel fibers, type of anchorages and bending inclination of the fiber exerted as anchorage, respectively 45° for concrete beam and 90° for masonry column.
Test results demonstrate that the introduction of additional anchorages improves the effectiveness of the FRCM composites in terms of resistance and loading capacity.
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Lepenies, Ingolf G. "Zur hierarchischen und simultanen Multi-Skalen-Analyse von Textilbeton." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23636.
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Die Arbeit widmet sich der Simulation und der Prognose des Materialverhaltens des Hochleistungsverbundwerkstoffes Textilbeton unter Zugbeanspruchungen. Basierend auf einer hierarchischen mechanischen Modellbildung (Multi-Skalen-Analyse) werden die Tragmechanismen des Verbundwerkstoffes auf drei Strukturebenen abgebildet. Damit lassen sich die den Verbundwerkstoff charakterisierenden mechanischen Kenngrößen aus experimentell ermittelten Kraft-Verschiebungs-Abhängigkeiten ableiten. Diese Kenngrößen sind mit heutiger Messtechnik nicht direkt experimentell bestimmbar. Es wird ein Mikro-Meso-Makro-Prognosemodell (MMM-Prognosemodell) für Textilbeton entwickelt, das basierend auf der Simulation des Mikrostrukturverhaltens das makroskopische Materialverhalten prognostiziert. Die Grundlage dafür bildet die qualitative und quantitative Bestimmung der Verbundeigenschaften zwischen der Filamentbewehrung und der einbettenden Matrix. Für das Verbundverhalten von Rovings in einer Feinbetonmatrix wird, ausgehend von einer Rovingapproximation mit superelliptischem Querschnitt, die partielle Imprägnierung des Rovings und die daraus resultierende Verbundwirkung identifiziert und simuliert. Auf Grundlage der mikro- und mesomechanischen Modelle sowie der Kalibrierung und Verifizierung des MMM-Prognosemodells durch die Simulation von Filament- und Rovingauszugsversuchen wird das makroskopische Zugverhalten von Textilbeton mit Mehrfachrissbildung prognostiziert. Die numerischen Ergebnisse werden durch die Ergebnisse der experimentellen Dehnkörperversuche validiert. Das MMM-Prognosemodell für Textilbeton wird im Rahmen einer hierarchischen Multi-Skalen-Analyse auf Zugversuche von Textilbetonbauteilen angewendet. Weiterhin wird die Verstärkungswirkung einer Textilbetonschicht an Stahlbetonbauteilen unter Biegebeanspruchung zutreffend simuliert. Es wird das nichtlineare Bauteilverhalten abgebildet, wobei die Bauteildurchbiegung, die effektiven Rovingbeanspruchungen und die Beanspruchungen der Filamente im Roving abgebildet werden.The present work deals with the simulation and the prediction of the effective material behavior of the high performance composite textile reinforced concrete (TRC) subjected to tension. Based on a hierarchical material model within a multi scale approach the load bearing mechanisms of TRC are modeled on three structural scales. Therewith, the mechanical parameters characterizing the composite material can be deduced indirectly by experimentally determined force displacement relations obtained from roving pullout tests. These parameters cannot be obtained by contemporary measuring techniques directly. A micro-meso-macro-prediction model (MMM-PM) for TRC is developed, predicting the macroscopic material behavior by means of simulations of the microscopic and the mesoscopic material behavior. The basis is the qualitative and quantitative identification of the bond properties of the roving-matrix system. The partial impregnation of the rovings and the corresponding varying bond qualities are identified to characterize the bond behavior of rovings in a fine-grained concrete matrix. The huge variety of roving cross-sections is approximated by superellipses on the meso scale. The macroscopic behavior of TRC subjected to tension including multiple cracking of the matrix material is correctly predicted on the basis of the micro- and meso-mechanical models. The calibration and verification of the MMM-PM is performed by simulations of roving pullout tests, whereas a first validation is carried out by a comparison of the numerical predictions with the experimental data from tensile tests. The MMM-PM for TRC is applied to tensile tests of structural members made of TRC. Furthermore, a steel-reinforced concrete plate strengthened by a TRC layer is accurately simulated yielding the macroscopic deflection of the plate, the mesoscopic stress state of the roving and the microscopic stresses of the filaments.
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Clark, Richard L. "Altering the fiber-matrix interphase in semicrystalline polymer matrix composites." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020216/.
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Voirin, Thibaut. "Etude du comportement mécanique et de l’endommagement des composites C/C à basses et hautes températures." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI008.
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Les matériaux composites Carbone/Carbone sont utilisés dans l’industrie aéronautique ainsi que dans l’aérospatial du fait de leurs excellentes propriétés thermomécaniques, de la température ambiante jusqu’à de très hautes températures (< 3000°C). Cependant l’évolution de ces propriétés à hautes températures est peu connue, notamment sous des sollicitations de type freinage auxquelles ces composites peuvent être soumis pour des applications aéronautiques ou dans les sports mécaniques.L’objectif de ce travail était donc d’étudier le comportement mécanique d’un composite C/C stratifié sous des sollicitations mécaniques pouvant intervenir dans une situation de freinage. Ainsi, la compression et le cisaillement ont été particulièrement étudiés, afin de déterminer l’évolution des mécanismes d’endommagement en fonction de la température sous ces modes de chargement. Afin de mener à bien cette étude, plusieurs aspects expérimentaux ont été abordés, tels que la géométrie et la taille des éprouvettes, de même que les difficultés de mesures liées à la réalisation des essais mécaniques à hautes températures. C’est ainsi que des essais originaux de cisaillement interlaminaire à chaud ont pu être réalisés. Parallèlement à ces essais, la microstructure du matériau a été étudiée in-situ et post-mortem par une analyse multi-échelle (à l’échelle des strates, des torons et au niveau des fibres à l’intérieur des torons). L’évolution des propriétés mécaniques a été mise en relation avec les observations microstructurales pour les différents modes de chargement étudiés (compression « Z », compression « XY » et cisaillement interlaminaire), afin de proposer des scenarii d’endommagement du matériau en fonction de la température. Grâce à cette approche, le rôle majeur des dilatations thermiques différentielles des torons sur le frettage des aiguilletages a pu être mis en évidence pour des températures allant jusqu’à 1500°C. Pour des températures supérieures, des effets de plasticité ont été identifiésCarbon/Carbon composites are used in aeronautics and space industries for their excellent thermomechanical properties, from room temperature to very high temperatures (up to 3000°C). Nevertheless, these properties and their evolution at elevated temperatures are not known well enough, specifically for braking-like solicitations such as plane braking or motorsport braking.The main objectives of this work was to study the mechanical behavior of this composite under mechanical solicitations that may occur during a braking situation. Thereby, compressive and shear behavior were studied in particular, in order to determine the evolution of the damage mechanisms depending on the temperature for these loading modes. In order to lead this study successfully, various experimental aspects have been approached, such as sample geometry, as well as measurements issues due to the mechanical testing at high temperatures. This is how original mechanical testing of the interlaminar shear behavior have been performed. Concurrently with these tests, the material microstructure has been studied in-situ and post-mortem with a multi-scale approach (at ply level, at yarn level and at fiber level inside the strands). The evolution of the mechanical properties has been linked to the microstructure evolution for the different loading modes (Z-compression, XY-compression and interlaminar shear) in order to propose damage scenario of the material as a function of the temperature. This approach allowed us to understand the major role of the thermal differential dilatations of the yarn on the shrinking of the needles for temperatures up to 1500°C. For temperatures higher than 1500°C, plasticity effects have been identified