Abstract: Within the pores of a porous thermostructural composite material, there is form an aerogel or xerogel made up of a precursor for a refractory material, the precursor is transformed by pyrolysis to obtain an aerogel or xerogel of refractory material, and then it is silicided by being impregnated with a molten silicon type phase. The aerogel or xerogel is formed by impregnating the composite material with a composition containing at least one organic, organometalloid, or organometallic compound in solution, followed by in situ gelling. The method is applicable to improving the tribological properties or the thermal conductivity of C/C or C/SiC composite material parts, or to making such parts leakproof.

Abstract: A turbine ring assembly for a gas turbine includes a one-piece split ring (10) of ceramic matrix composite (CMC) material, a CMC wedge-shaped part (20) having flanks in contact with the ends of the ring, on either side of the split, so as to close the ring, and an annular metal support structure (40) surrounding the CMC ring and in contact therewith over the major fraction of its outline, the CMC ring being mounted with prestress in the metal structure, at least one element (26) exerting a resilient return force on the wedge-shaped part to keep it in contact with the ends of the CMC ring when the split opens under the effect of differential expansion between the annular metal structure and the CMC ring, and at least one element for preventing the CMC ring from turning about its axis.

Abstract: The method comprises: using chemical vapor infiltration to form a first continuous interphase on the fibers of a fiber structure made of refractory fibers, the interphase having a thickness of no more than 100 nanometers; impregnating the fiber structure with a consolidation composition comprising a carbon or ceramic precursor resin; forming a fiber preform that is consolidated by shaping the impregnated fiber structure and using pyrolysis to transform the resin into a discontinuous solid residue of carbon or ceramic; using chemical vapor infiltration to form a second continuous interphase layer; and densifying the preform with a refractory matrix. This preserves the capacity of the fiber structure to deform so as to enable a fiber preform to be obtained that is of complex shape, while nevertheless guaranteeing the presence of a continuous interphase between the fibers and the matrix.

Abstract: The method comprises: using chemical vapor infiltration to form a first continuous interphase on the fibers of a fiber structure made of refractory fibers, the interphase having a thickness of no more than 100 nanometers; impregnating the fiber structure with a consolidation composition comprising a carbon or ceramic precursor resin; forming a fiber preform that is consolidated by shaping the impregnated fiber structure and using pyrolysis to transform the resin into a discontinuous solid residue of carbon or ceramic; using chemical vapor infiltration to form a second continuous interphase layer; and densifying the preform with a refractory matrix. This preserves the capacity of the fiber structure to deform so as to enable a fiber preform to be obtained that is of complex shape, while nevertheless guaranteeing the presence of a continuous interphase between the fibers and the matrix.

Abstract: The invention relates to a structuring assembly (13) for an exhaust nozzle, including the following main elements: (a) an outer skin (22) including a non-acoustic portion (33); (b) an inner structuring skin (23); (c) an acoustic structure (21) including cells (27) having a cellular core, said acoustic structure being arranged between the outer skin (22) and the inner structuring skin (23), at least one of said main elements being made of a composite material, and the acoustic structure (21) being supported between the outer skin (22) and inner structuring skin (23) by linking means (31; 41) attached to the inner structuring skin (23) and to the non-acoustic portion (33) of the outer skin (22) so as to transfer the stresses onto the inner structuring skin (23) and the non-acoustic portion (33) of the outer skin (22). The invention also relates to an exhaust nozzle for a nacelle, comprising such a structuring assembly (13), as well as to a nacelle.

Abstract: In a composite material part having a ceramic matrix and including a fibrous reinforcement which is densified by a matrix consisting of a plurality of ceramic layers having a crack-diverting matrix interphase positioned between two adjacent ceramic matrix layers, the interphase includes a first phase made of a material capable of promoting the diversion of a crack reaching the interphase according to a first propagation mode in the transverse direction through one of the two ceramic matrix layers adjacent to the interphase, such that the propagation of the crack continues according to a second propagation mode along the interphase, and a second phase consisting of discrete contact pads that are distributed within the interphase and capable of promoting the diversion of the crack that propagates along the interphase according to the second propagation mode, such that the propagation of the crack is diverted and continues according to the first propagation mode through the other ceramic matrix layer that is adj

Abstract: In order to assemble together two parts (154, 162) of materials having different coefficients of expansion via mutually engaged edge portions (154a, 162a), tongues (170) are formed in the thinned edge of one of the parts, the tongues being separated by slots (172) obtained by cutting or machining the material of the part, and the parts are assembled together by fastening (174) via the tongues. The edge portions are mutually engaged in such a manner as to be in substantially leaktight contact at the high temperatures encountered in operation. The method is applicable in particular to assembling together parts made respectively of metal and of ceramic composite material, in particular in an aviation gas turbine, for example, upstream and downstream secondary nozzles.

Abstract: A turbine nozzle element including an inner annular platform sector, an outer annular platform sector, and at least one vane extending between the platform sectors and connected to both of them. The nozzle element includes a single piece of composite material including fiber reinforcement densified by a matrix that is at least partially ceramic, and the fiber reinforcement includes a fiber structure that is woven by three-dimensional or multi-layer weaving, and that presents continuity throughout the volume of the nozzle element and throughout the periphery of the vane.

Abstract: To densify thin porous substrates (1) by chemical vapor infiltration, the invention proposes using loading tooling (10) comprising a tubular duct (10) disposed between first and second plates (12, 13) and around which the thin substrates for densification are disposed radially. The tooling as loaded in this way is then placed inside a reaction chamber (20) in an infiltration oven having a reactive gas admission inlet (21) connected to the tubular duct (11) to enable a reactive gas to be admitted into the duct which distributes the gas along the main faces on the substrates (1) in a flow direction that is essentially radial. The reactive gas can also flow in the opposite direction, i.e. it can be admitted into the tooling (10) from its outer envelope (16) and can be removed via the duct (11).

Abstract: A rotor includes a disc, on which are fixed vanes, and platforms between these vanes. The rotor is particularly remarkable in that the platforms are fixed securely and tightly to the disc. To this end, the disc includes between two successive vanes an upstream stop projecting axially from the upstream surface, and each platform includes: a plate, a retaining groove extending axially and in which the upstream stop of the disc is engaged, an axial stop bearing axially against the upstream surface of the disc.

Abstract: A reinforcing fiber texture for a composite material part is made by multi-layer three-dimensional weaving with a satin type weave or a multiple satin type weave. The texture comprises at least three layers of weft yarns T interlaced by warp yarns C, each warp yarn taking hold in alternation of one weft yarn in n from a first layer of weft yarns and of one weft yarn in n of a second layer of weft yarns adjacent to the first, the number n being an integer not less than 3. The paths of the warp yarns are similar and they are offset in the warp direction.

Abstract: An annular combustion chamber has an inner wall and an outer wall of ceramic matrix composite material, together with a chamber end wall that is connected to the inner and outer walls. Elastically-deformable link elements connect the inner wall and the outer chamber walls to inner and outer metal casings. Each of the inner and outer chamber walls is subdivided circumferentially into adjacent sectors along longitudinal edges, each sector extending continuously from the end wall to the opposite end of the chamber and being folded outwards from the chamber at each of its longitudinal edges to form a portion having a U-shaped cross-section terminated by a folded-back margin that is spaced apart from the outer face of the corresponding chamber wall. The link elements are connected to the inner and outer chamber walls by being fastened to the sector margins.

Abstract: An assembled annular combustion chamber comprises an annular inner wall and an annular outer wall made of ceramic matrix composite material together with a chamber end wall connected to the inner and outer walls and provided with orifices for receiving injectors. Elastically-deformable link parts connect the inner wall and the outer wall of the chamber to inner and outer casings that are made of metal. The assembly formed by the inner wall, the outer wall, and the combustion chamber end wall is subdivided circumferentially into adjacent chamber sectors, each sector being made as a single piece of ceramic composite material and comprising an inner wall sector, an outer wall sector, and a chamber end wall sector. The link parts connect the inner metal casing and the outer metal casing respectively to each inner wall sector of the combustion chamber and to each outer wall sector of the chamber. The chamber end wall sectors are in contact with a one-piece ring to which they are connected.

Abstract: An assembled annular combustion chamber comprises an annular inner wall and an annular outer wall made of ceramic matrix composite material together with a chamber end wall connected to the inner and outer walls and provided with orifices for receiving injectors. Elastically-deformable link parts connect the inner wall and the outer wall of the chamber to inner and outer casings that are made of metal. The assembly formed by the inner wall, the outer wall, and the combustion chamber end wall is subdivided circumferentially into adjacent chamber sectors, each sector being made as a single piece of ceramic composite material and comprising an inner wall sector, an outer wall sector, and a chamber end wall sector. The link parts connect the inner metal casing and the outer metal casing respectively to each inner wall sector of the combustion chamber and to each outer wall sector of the chamber. The chamber end wall sectors are in contact with a one-piece ring to which they are connected.

Abstract: An environmental barrier for a substrate of ceramic matrix composite material containing silicon, in particular containing SiC, is formed by an anticorrosion protection layer containing an aluminosilicate type compound of an alkali or alkaline-earth or rare earth element, e.g. BSAS, with a chemical barrier forming layer of aluminum nitride being interposed between the substrate and the anticorrosion protection layer.

Abstract: A vibration damper for a rotor blade of a gas turbine engine, includes a plate for placing between an inner bearing surface and an outer bearing surface of the rotor, the bearing surfaces extending in directions that are substantially axial and being radially spaced apart from each other, the plate being folded so as to form two plate portions that are inclined relative to each other, the mass of the plate being distributed in such a manner that its center of gravity is situated on the side of one of these plate portions, the free end of the other plate portion being designed to bear radially against the inner bearing surface, and the junction zone between the two plate portions being designed to bear radially against the outer bearing surface under the effect of centrifugal force when the rotor is rotating so as to provide axial sealing against gas.

Abstract: A method of smoothing the surface of a ceramic matrix composite material part that presents a surface that is undulating and rough. The method includes depositing a refractory vitreous coating on the surface of the part, the vitreous coating essentially containing silica, alumina, baryte, and lime.

Abstract: A method of fabricating a composite-material turbomachine blade having platform incorporated therein includes separately making a blade platform element that comprises rigidified fiber reinforcement and that has a shape close to that of a platform of the blade to be fabricated, with at least one opening being formed through the platform element. The opening has the shape of the profile of the airfoil of the blade to be fabricated. Three-dimensional weaving is used to make a flexible fiber blank as a single piece that includes blade airfoil-and-root preform portions. The platform element is engaged, via its opening, on the flexible fiber blank while deforming it so as to assemble the platform element with the fiber blank. The fiber blank is shaped together with the platform element assembled thereon to obtain a blade preform of a shape that is close to the shape of the blade to be fabricated. After shaping, the blade preform is consolidated in its shape in a shaper.

Abstract: The invention relates to a turbomachine blade made of composite material and presenting a root with a bulb-shaped end suitable for engaging in a slot of a rotor disk. In characteristic manner, the end of the root of the blade is provided, beside one of its front faces, with a projecting portion having two symmetrical fins about the axial midplane of the root, each fin having a bearing face suitable for limiting tilting of the blade relative to the rotor disk about the axial direction.

Abstract: A turbine ring assembly includes a ring support structure and a plurality of ring sectors, each including a single piece of ceramic matrix composite material. Each ring sector includes a first portion forming an annular base with an inside face defining an inside face of the turbine ring and an outside face from which there extends two tab-forming portions including ends that are engaged in housings in the ring support structure. The ring sectors present a section that is substantially ?-shaped and the ends of the tabs are held without radial clearance by the ring support structure. The tabs can have a free length in meridian section that is not less than three times their mean width.