Mechanical behavior of an oxide/oxide composite

Les composites oxyde/oxyde sont des matériaux composites à matrice céramique (CMC) dont l’emploi est envisagé pour les arrière-corps de moteurs d’avion. Leur utilisation se justifie principalement par: une très bonne tenue à l’oxydation, un comportement mécanique intéressant à de hautes températures,et un faible coût de mise en œuvre. L’objectif de ce papier est de présenter les composites oxyde/oxyde via leur microstructure particulière,et d’étudier le lien entre endommagement et comportement mécanique. Le couplage plan-hors plan s’opérant lors d’une sollicitation en traction s’avère être un indicateur d’endommagement intéressant. Le poster s’appuiera sur des recherches bibliographiques ainsi que sur des résultats d’essais de traction instrumentés avec capteurs d’émission acoustique et corrélation d’images. La pertinence des moyens expérimentaux ainsi que les objectifs de recherches futures sont finalement évoqués.Oxide/oxide composites are ceramic matrix composite materials (CMC) intended to be used innew generation aircraft engines. The main purposes for the use of this type of materials are: an outstanding oxidation durability, an interesting mechanical behavior up to high temperatures, and a moderate manufacturing cost. The aim of this paperis to introduce oxide/oxide composites through their particular microstructure,and the analysis of the connection between damage mechanisms and mechanical behavior. The in-plane / out-of-plane coupling occurring during tensile solicitation is an interesting damage indicator. This presentation is based on literature studies and the results of tensile tests monitored by acoustic emission and digital image correlation. The relevance of experimental techniques as well as future investigation goals will finally be mentioned

Bearing damage identification in oxide/oxide ceramic matrix composite with a new test design

In this paper, the mechanisms of damage of an oxide/oxide ceramic matrix composite bearing are studied with a new experimental setup, the balanced quarter hole device (BQH). This test was designed to allow direct observation of the damage development on a material subjected to bearing failure. In a standard bearing experiment, real time monitoring is extremely difficult to set up, and post mortem observations of the bearing plane can be biased by the cutting operation. High speed cameras were used to take pictures of the bearing plane so that the damage development could be studied and a damage chronology established. The validity of the setup was verified by comparing the results obtained with those of a standard bearing test. Two different stacking sequences were studied, and the influence of the material microstructure and composite machining was investigated. It was shown that the first critical damage, matrix cracks, appeared before the load drop, and then led to delamination and kink bands, causing the final failure of the material

Sur l'oxydation du cuivre et de ses alliages III.—Influence de la microstructure sur l'oxydation du cuivre pur;

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Contribution à l' étude de l'oxydation du cuivre

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Sur I'oxydation sèche du cuivre et de ses alliages II.‐Etude de I'oxydation isotherme du cuivre pur

This paper deals with the kinetics of thermal oxidation, in pure oxygen at atmospheric pressure, of electrolytically polished copper at 173° C and 247° C. These temperatures were chosen so as to be on either sides of 224° C, because previous work had chosen that this temperature coincided with the appearance of cupric oxide in the films. It was confirmed in the present paper that cupric oxide is a product of the oxidation of cuprous oxide and not of the copper itself. The oxidation of cuprous oxide only starts when the latter is sufficiently thick (circa 2,500 Å). It was also confirmed that films containing cupric oxide are much less adherent than those of pure suprous oxide. Copyright © 1951 Wiley‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Sur l'oxydation sèche du cuivre et de ses alliages I, Influence de la température sur l'oxydation isochrone du cuivre pur

Electropolished samples of copper were kept in contact with dry oxygen under atmospheric pressure, at temperatures ranging from 100° to 900° C. Oxide films were formed. These were all examined under the microscope, by electron diffraction and in some cases by X ray diffraction and with an electron microscope. They were also analysed qualitatively and quantitatively, by Miley's electrochemical method. It was shown that the direct oxidation of copper always led to cuprous oxide Cu2O. At temperatures higher than 224° C cuprous oxide was in its turn oxidized to cupric oxide CuO. Above 317° C the rate of oxidation was so great that cuprous oxide could no longer be detected in the films. It appeared also that the first layers of cuprous oxide had a strong [III] orientation, which disappeared as soon as film thickness reached about 700A. Cupric oxide behaved in a quite different manner. At first it was randomly orientated, but recrystallized as it thickened, and finally showed, in very thick films, a very marked orientation. Finally it was shown that the beginning of scalling coincided with the first appearance of cupric oxide but disappeared for temperatures higher than 800° C. Copyright © 1951 Wiley‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Contribution à l'étude des surfaces métalliques. I. Influence de la microstructure superficielle du cuivre poli électrolytiquement sur son diagramme de diffraction électronique

Les auteurs confirment la possibilité d' obtenir des surfaces de cuivre pratiquement parfaites par polissage électrolytique. l' aspect des diagrammes électroniques de ces surfaces a pu être interprété plus sûrement grâce a l' utilisation d' une méthode expérimentale mieux adaptée à l' étude du problème. Copyright © 1956 Wiley‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Influence de faibles quantités de nickel sur l'oxydation du cuivre

The authors have studied the influence of small quantities of nickel on the oxidation in pure oxygen at atmospheric pressure, of copper at temperatures equal to and below 200°C. Under these conditions, there always exists a large region where only Cu 2O is formed. This study shows that: 1. (1) the alloys of Cu-Ni containing 5 and 10% nickel oxidize less rapidly than pure copper during the period studied. 2. (2) alloys containing 0,5 and 1% nickel oxidize more rapidly during an initial period, the length of which varies inversely with the nickel content. 3. (3) the alloys containing 0,1 per cent oxidizes the most rapidly during the period investigated. 4. (4) the oxide CuO always appears sooner on these alloys. © 1959.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Oxydation du cadmium et mecanisme de la germination de l'oxyde

Treatment of solid cadmium at temperatures near its melting point in a low partial pressure of oxygen strongly modifies the behavior of the metal during subsequent oxidation in the domain within which nucléation of cadmium oxide takes place. The observed facts-multiplication of the number of oxide nucléation sites, disappearance of the incubation period and a displacement of the nucléation domain towards low partial oxygen pressures-are attributed to a dissolution of oxygen in the cadmium. These results confirm the mechanism proposed by Bérnard and his collaborators which state that the formation of oxide nuclei is attributed to a supersaturation of oxygen in the surface layer of the metal. © 1963.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Structure de monocristaux d'alliage cuivre-nickel fabriqués par la technique de bridgman

Copper-nickel single crystals, in which the concentration Co of nickel ranges between 102 and 105 ppm, are grown from the melt by the Bridgman technique. Selective oxidation of the nickel in those crystals reveals a characteristic cellular structure, which can be related to constitutional supercooling. This is quite similar to many other alloys previously studied, in which the solute lowers the melting point of the solvent. According to Tiller's criteria, a plane interface should be stable for concentrations of nickel lower than 103 ppm. By means of selective oxidation in alloys containing 102 ppm of solute, no cellular segregation can be detected, though this technique is more sensitive than others used in this work, such as the autoradiography of 63Ni, the electron microprobe and the electron scanning microscope. © 1972.SCOPUS: ar.jinfo:eu-repo/semantics/publishe