Search results for "composite"
showing 10 items of 4584 documents
A physical-based constitutive model for surface integrity prediction in machining of OFHC copper
2017
International audience; Due to the rising interest in predicting machined surface integrity and sustainability, various models for metal cutting simulation have been developed. However, their accuracy depends deeply on the physical description of the machining process. This study aims to develop an orthogonal cutting model for surface integrity prediction, which includes a physical-based constitutive model of Oxygen Free High Conductivity (OFHC) copper. This constitutive model incorporates the effects of the state of stress and microstructure on the work material behavior, as well as a dislocation density-based model for surface integrity prediction. The coefficients of the constitutive mod…
Prise en eau par composites carbone/époxy et leur effet sur le comportement mécanique : application aux réparations de structures en composite par co…
2013
Le travail présenté dans ce mémoire avait pour objectif d’étudier le processus de la pénétration d'eau dans les composites en carbone/époxyde dans un premier temps, et dans un deuxième temps, d’étudier l’effet de la prise en eau par ces matériaux sur les performances mécaniques des composites et leur joints collés. L'intégration de ces phénomènes physiques dans la modélisation numérique est d'une grande importance dans la prédiction de la durabilité d’une structure en composite subissant un vieillissement hygrothermique. Par conséquent, ce travail consiste non seulement en des observations expérimentales, mais aussi en des simulations numériques. Des corrélations entre les résultats obtenus…
Flash microwave synthesis and sintering of nanosized La0.75Sr0.25Cr0.93Ru0.07o3–δ for fuel cell application.
2009
International audience; Perovskite-oxide nanocrystals of La0.75Sr0.25Cr0.93Ru0.07O3–δ with a mean size around 10 nm were prepared by microwave flash synthesis. This reaction was performed in alcoholic solution using metallic salts, sodium ethoxide and microwave autoclave. The obtained powder was characterised after purification by energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM). The results show that integrated perovskite-type phase and uniform particle size were obtained in the microwave treated samples. At last the synthesised powder was directly used in a sin…
Development and characterization of a bio-based epoxy matrix for high-grade bio-based composites
2019
This study aims to develop 100% bio-based hemp/epoxy composites for semi-structural and structural applications. The thermal and mechanical performances of a 100% bio-based matrix derived from biomassare evaluated and reveal properties in the same order of magnitude as those obtained for polyepoxides based on DGEBA, that means a glass transition temperature of approximately 150°C and mechanical properties in the order of 120MPa for the maximum stress and 3.2 GPa for the tangent apparent modulus. This natural origin matrix is then used for the manufacture of composites reinforced with hemp rovings. The bending properties of these 100% bio-based materials are equivalent to those determined fo…
Development and characterization of a bio-based epoxy matrix for high-grade bio-based composites
2019
This study aims to develop 100% bio-based hemp/epoxy composites for semi-structural and structural applications. The thermal and mechanical performances of a 100% bio-based matrix derived from biomassare evaluated and reveal properties in the same order of magnitude as those obtained for polyepoxides based on DGEBA, that means a glass transition temperature of approximately 150°C and mechanical properties in the order of 120MPa for the maximum stress and 3.2 GPa for the tangent apparent modulus. This natural origin matrix is then used for the manufacture of composites reinforced with hemp rovings. The bending properties of these 100% bio-based materials are equivalent to those determined fo…
ZnO(core)/TiO2(shell) composites : influence of TiO2 microstructure, N-doping and decoration with Au nanoparticles on photocatalytic and photoelectro…
2017
The aim of the thesis is to study the influence of microstructure of ZnO/TiO2 composites on their properties in photocatalytic degradation of organic pollutants, and in photoassisted water oxidation. To realize such study we chose the design based on ZnO nanorods supported on ITO (Indium Tin Oxide)-coated glass electrode. The ZnO nanorods were then covered with a layer of TiO2 under different conditions. The composition and microstructure of the obtained ZnO(core)/TiO2(shell) composites were modified in the aim to elucidate how these parameters influence their photocatalytic activity. The results of studies lead to elaboration of two most distinctive variants of sol-gel procedure that allow…
Détection d'endommagement dans les composites à l'aide des micro-ondes. Comparaison avec la thermographie infrarouge
2011
International audience; On compare dans cette étude deux méthodes de détection d'endommagement dans les composites : une basée sur la technologie des structures propagatives électromagnétiques dans la gamme des micro-ondes et l'autre basée sur la mesure de champs thermiques dans la gamme des infrarouges. Toutes deux sont appliquées à la détection des ruptures de fibres et du délaminage dans des composites fibres/résine de type verre/époxy et carbone/époxy.
Comparison between 2 Different Composite Nd3+:YVO4 Crystals in a Fibre Coupled Diode Pumped Laser
2008
International audience; We detail the performances of two composite Nd3+YVO4crystals, realised with two different sticking techniques. We tested them inside a fibre coupled diode end pumped laser.
γ-ray induced GeODC(II) centers in germanium doped α-quartz crystal
2011
International audience; Main luminescence of α-quartz crystal doped with germanium results from the luminescence of a self-trapped exciton (STE) near germanium. In as grown Ge-doped α-quartz crystal, the luminescence associated with the twofold coordinated Ge center (GeODC) in amorphous silica glass doped with germanium, was never observed. In this work, we performed experiments to investigate if a GeODC like luminescence could appear after a γ-irradiation of a Ge-doped α-quartz crystal. The answer is positive: under excitation with pulsed light of an ArF laser (193 nm): a new luminescence with two bands -- a blue one associated to a time constant of about 100 μs appears and another one wit…
Raman investigation of the drawing effects on Ge-doped fibers
2011
International audience; We have investigated the Raman activity of various germanosilicate fibers and their associated preforms. Our data indicate an enhancement in small rings' (3-member rings) concentration in the silica-based matrix of the fibers during the drawing process. The generation of such rings appears compatible with an increase of the sample density and fictive temperature. The data regarding the drawing effects on the fiber stress appear less clear, and it is possible to suggest that in some cases the drawing could lower the tensile stress. Finally we have also provided evidence that changing the drawing conditions within the usual range of application leads to no significant …