Preform and one-piece vane for turbomachine

Abstract

A fiber preform for a turbine engine blade, the preform comprising a main fiber structure (40) obtained by a single piece of three-dimensional weaving, said main first structure (40) comprising a first longitudinal segment (41) suitable for forming a blade root, a second longitudinal segment (42) extending the first longitudinal segment (41) and suitable for forming an airfoil portion (22), and a first transverse segment (51) extending transversely from the junction (49) between the first and second longitudinal segments (41, 42) and suitable for forming a first tongue for a first platform, wherein the first transverse segment (51) extends axially over a length that is less than 30%, preferably less than 15%, of the length of the junction (49) between the first and second longitudinal segments (41, 42).

Claims

1. A fiber preform for a turbine engine blade, the preform comprising a main fiber structure obtained by a single piece of three-dimensional weaving, said main first structure comprising: a first longitudinal segment suitable for forming a blade root; a second longitudinal segment extending the first longitudinal segment and suitable for forming an airfoil portion; and at least one transverse segment extending transversely from a junction between the first and second longitudinal segments and suitable for forming a tongue for a platform; wherein the at least one transverse segment extends axially over a length that is less than 30% of a length of the junction between the first and second longitudinal segments.

2. A preform according to claim 1, wherein the at least one transverse segment includes a plurality of transverse segments extending transversely in a same direction from the junction between the first and second longitudinal segments and suitable for forming tongues for a common platform; wherein said longitudinal segments are spaced apart from one another.

3. A preform according to claim 1, wherein the main fiber structure further includes at least one additional transverse segment extending transversely from the junction between the first and second longitudinal segments, in a direction opposite to the at least one transverse segment, and suitable for forming a tongue for a second platform.

4. A preform according to claim 1, wherein the at least one transverse segment extends axially from a front end of the junction between the first and second longitudinal segments.

5. A preform according to claim 1, wherein the at least one transverse segment extends axially from a rear end of the junction between the first and second longitudinal segments.

6. A preform according to claim 1, wherein the at least one transverse segment is formed by at least a portion of a free flap said free flap and said second longitudinal segment being woven jointly in a non-interlinked manner, said non-interlinking starting at the junction between the first and second longitudinal segments.

7. A preform according to claim 1, further comprising at least one fiber strip, that is woven independently of the main fiber structure, and that is of a width substantially equal to the length of the junction between the first and second longitudinal segments, and that is suitable for forming a platform.

8. A preform according to claim 7, wherein the fiber strip is fitted to the at least one transverse segment or at least one additional transverse segment of the main fiber structure by being put against a bottom surface of said at least one transverse segment or the at least one additional transverse segment.

9. A preform according to claim 7, wherein a top surface of the fiber strip is flush with a top surface of the at least one transverse segment or the at least one additional transverse segment.

10. A preform according to claim 1, wherein the at least one transverse segment extends axially over a length that is less than 15% of the length of the junction between the first and second longitudinal segments.

11. A turbine engine blade comprising: a blade root; an airfoil portion; and a platform extending transversely to the airfoil portion at a level of a junction between the blade root and the airfoil portion; said blade being characterized in that it is made as a single piece of composite material by means of a fiber preform according to claim 1, said preform being shaped in a mold and embedded in a matrix.

12. A turbine engine fan, characterized in that it comprises a plurality of blades according to claim 11.

13. A turbine engine, characterized in that it includes at least one blade according to claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are diagrammatic and seek above all to illustrate the principles of the invention.

(2) In the drawings, from one figure to another, elements (or portions of an element) that are identical are identified using the same reference signs.

(3) FIG. 1 is a section view of a turbine engine in accordance with the disclosure.

(4) FIG. 2 is a perspective view of a blade in accordance with the disclosure.

(5) FIG. 3 is a perspective view, prior to assembly, of a preform suitable for obtaining such a blade.

(6) FIGS. 4A and 4B are diagrams showing the main fiber structure of the preform.

(7) FIG. 5 shows non-interlinking in simplified manner.

(8) FIG. 6 is a perspective view of the preform once assembled and shaped.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) In order to make the invention more concrete, an embodiment is described below in detail with reference to the accompanying drawings. It should be recalled that the invention is not limited to this embodiment.

(10) FIG. 1 is a view of a bypass turbojet 1 in accordance with the disclosure and shown in section on a vertical plane containing its main axis A. From upstream to downstream in the flow direction of the air stream, it comprises a fan 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6, and a low pressure turbine 7. In its upstream portion, the turbojet 1 has an outer casing 8 and an inner casing 9 defining two concentric flow passages, namely a primary passage I and a secondary passage II.

(11) FIG. 2 is a diagrammatic perspective view of a blade 20 of the fan 2. Such a blade 20 comprises a blade root 21 and an airfoil portion 22. The airfoil portion 22 serves mainly to perform the aerodynamic function of the blade 20, while the blade root 21 serves mainly to fasten the blade 20 and provide it with mechanical strength.

(12) The blade root 21 has a dovetail profile enabling it to be fastened in a slot in a fan disk.

(13) The blade 20 also has pressure-side and suction-side platforms 31 and 32 extending substantially orthogonally to the airfoil portion 22 and on either side thereof, level with the boundary blade root 21 and the airfoil portion 22. These platforms 31 and 32 serve to make up a smooth and aerodynamic inner wall for the flow passage and they provide a diameter transition from upstream to downstream across the fan 2.

(14) In this embodiment, the blade 20 is a fan blade having a dovetail root 21 and two platforms 31 and 32. Nevertheless, in other examples, it could be some other type of blade, a stationary blade (i.e. a vane) or a moving blade, for a compressor or possibly for a turbine, or indeed for an intermediate casing or a rear casing, to mention only some examples. It could thus equally well include upper platforms or indeed fastener flanges at the root or at the tip of the blade.

(15) FIG. 3 shows the preform 70 for making this example blade 20. It comprises a three-dimensionally woven main fiber structure 40 together with two fiber strips 60 that are likewise woven three-dimensionally, but independently of the main fiber structure 40.

(16) The main fiber structure 40 comprises a first longitudinal segment 41 and a second longitudinal segment 42 defined by a boundary 49. The main fiber structure 40 also has four transverse segments 51, 52, 53, and 54 extending transversely from the boundary 49 that forms the junction between the first and second longitudinal segments 41 and 42.

(17) A first transverse segment 51 extends on the pressure side from the front end of the main fiber structure 40, i.e. from the leading edge of the blade 20. Its axial length, i.e. its length along the boundary 49, is equal to about 20% of the length of the boundary 49.

(18) A second transverse segment 52 also extends on the pressure side, but from the rear end of the main fiber structure 40, i.e. from the trailing edge of the blade 20. Its axial length, i.e. its length along the boundary 49, is likewise about 20% of the length of the boundary 49.

(19) A third transverse segment 53 extends on the suction side opposite from and in line with the first transverse segment 51, i.e. from the front end of the main fiber structure 40. Its axial length corresponds substantially to the axial length of the first transverse segment 51.

(20) A fourth transverse segment 54 likewise extends on the suction side opposite from and in line with the second transverse segment 51, i.e. from the rear end of the main fiber structure 40. Its axial length corresponds substantially to the axial length of the second transverse segment 51.

(21) The weaving of this main fiber preform 40 is described below with reference to FIGS. 4A and 4B. These two figures are in longitudinal section level with the first and third transverse segments 51 and 53, i.e. in the proximity of the front edge of the main fiber structure 40. Nevertheless, the weaving is entirely analogous level with the second and fourth transverse segments 52 and 54.

(22) FIG. 4A shows the three-dimensionally woven main fiber structure 40. FIG. 4B shows the same main fiber structure 40 after it has been shaped. This main fiber structure 40 is described from upstream to downstream in the weaving direction T, i.e. upwards in the figures. Nevertheless, the weaving could perfectly well be made from the other end and in the opposite direction.

(23) In this embodiment, the main fiber structure 40 is woven three-dimensionally using carbon fibers with a 3D interlock weave.

(24) At the upstream end, the weaving begins with a zone of interlinking L in which the first longitudinal segment 41 is woven to form the root 21 of the blade 20.

(25) Downstream from this zone of interlinking L, there begins a zone of non-interlinking D in which a first free flap 50a, a second longitudinal segment 42, and a second free flap 50b are woven jointly but in non-interlinked manner so as to leave respective planes 61 and 62 of non-interlinking.

(26) Methods of weaving that make such non-interlinking possible are now well known in the field of 3D weaving. By way of illustration, FIG. 5 is a simplified diagram of such non-interlinked weaving. In the zone of interlinking L, all of the layers of warp yarns c (orthogonal to the plane of the figure) are connected to one another by weft yarns t (running along the plane of the figure), thereby forming a single strip b0. Conversely, in the zone D of non-interlinking, two strips b1 and b2 are woven jointly but in non-interlinked manner, i.e. with independent weft yarns t for each strip b1, b2, such that a plane P of non-interlinking is arranged between the two strips b1 and b2. Naturally, such an arrangement can equally well be provided in the warp direction as in the weft direction, and thus equally well for warp strands or for weft strands.

(27) Furthermore, within this zone D of non-interlinking, layer exits are provided progressively along the weaving T between the second longitudinal segment 42 and each of the free flaps 50a, 50b.

(28) Methods of weaving that enable such layer exits to be provided are now well known in the field of 3D weaving. Specifically, the weft yarns are caused to leave free certain warp yarns, referred to as “floated yarns” since, not being attached to any weft yarn, they “float”, and can subsequently be shaved off: layers may thus be eliminated in full or in part, thereby enabling certain zones of the preform to be reduced in thickness. In this embodiment, this serves to thin down the second longitudinal segment 42 and thus the airfoil portion 22 that is made therefrom.

(29) On this topic, it should be observed that these exits of layers are made in this example inside the main fiber structure 40 while it is being woven: the floated warp yarns are thus enclosed, i.e. hidden, between the second longitudinal segment 42 and one or the other of the free flaps 50a and 50b.

(30) Once weaving is terminated, the free flaps 50a and 50b are cut so as to form respectively the first and third transverse segments 51 and 53. These segments are then folded outwards as shown by the arrows so as to occupy their final transverse positions: they form respective support tongues for the pressure-side and suction-side platforms 31 and 33.

(31) Once the free flaps 50a and 50b have been cut, the floated yarns lying at the surface of the second longitudinal segment 42 become accessible and can be shaved off.

(32) Furthermore, and in independent manner, the fiber strips 60 are woven, either three-dimensionally as in this example, or else two-dimensionally. Each of them extends over a length that corresponds to the length of the boundary 49 between the first and second longitudinal segments 41 and 42.

(33) At its front end, the top surface of each fiber strip 60 has a first notch 61 of shape corresponding substantially to the shape of the first transverse segment 51 or of the third transverse segment 53, as the case may be. In other words, the depth of the notch 61 corresponds to the thickness of the corresponding first or third transverse segment 51 or 53; the axial length of the notch 61 corresponds to the axial length of the corresponding first or third transverse segment 51 or 53; and the transverse width of the notch 61 corresponds to the transverse width of the corresponding first or third transverse segment 51 or 53.

(34) In the present example, the first notch 61 extends over the entire width of the fiber strip 60 in question. Thus, the fiber strip 60 possesses a width at its front end that corresponds to the transverse width of the corresponding first or third transverse segment 51 or 53.

(35) In analogous manner, at its rear end, the top surface of each fiber strip 60 likewise includes a second notch 62 of shape that corresponds substantially to the shape of the corresponding second or fourth transverse segment 52 or 54.

(36) In the present example, the second notch 62 extends likewise over the entire width of the fiber strip 60 in question. Thus, at its rear end, the fiber strip 60 possesses a width that corresponds to the transverse width of the corresponding second or fourth transverse segment 52 or 54.

(37) Each fiber strip 60 is then fitted under a pair of transverse segments 51, 52 or 53, 54, with all of the transverse segments 51-54 then being received in the notches 61 or 62. Consequently, the top surface of each fiber strip 60 is flush to the top surface of the transverse segments 51-54.

(38) As shown in FIG. 6, the preform 70 as prepared in this way may be moistened in order to soften it and make it easier to take the fibers out of register. It is then placed in a forming mold having an inside space that matches the shape desired for the preform 70.

(39) The preform 70 is then dried in order to stiffen it, thereby blocking the shape as imposed by the shaping. Finally, the preform 70 is placed in an injection mold having the dimensions desired for the final blade 20, with a matrix being injected into the mold, specifically an epoxy resin. By way of example, such injection may be performed by the known resin transfer molding (RTM) technique. At the end of this step, a blade 20 is thus obtained that is made of composite material comprising a preform 70 woven out of carbon fibers that is embedded in an epoxy matrix. The blade 20 may possibly be finished off by machining steps.

(40) In the present embodiment, each fiber strip 60 is adhesively bonded under the transverse segments 51-54. Nevertheless, in other embodiments, the fiber strip 60 could merely be put into place in the injection mold together with the main fiber structure 40, with the fiber strip 60 being bonded on the main fiber structure 40 as a result of this co-injection when the matrix solidifies.

(41) Although the present invention is described with reference to specific embodiments, it is clear that modifications and changes may be undertaken on the embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, individual characteristics of the various embodiments shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings need to be considered in a sense that is illustrative rather than restrictive.

(42) It is also clear that all of the characteristics described with reference to a method can be transposed singly or in combination to a device, and vice versa, all of the characteristics described with reference to a device can be transposed, singly or in combination to a method.