Lobed tubular piece made of a composite with unidirectional fibers

Abstract

A method for manufacturing a fibrous tubular structure including lobes, in which fibers are draped/deposited on a mandrel having a shape corresponding to that of the fibrous structure, includes draping/deposition carried out such that at least one group of fibers has a same orientation with respect to the axis (A) of said fibrous structure, then, the fibers having been draped over an angular sector less than the total periphery of the mandrel, one of the ends of the fibrous structure is separated from the mandrel in order to allow the continuation of the draping on the same mandrel.

Claims

1. A method for manufacturing a tubular fibrous structure with lobes, the method comprising: drape-molding/depositing fibers on a mandrel having a shape corresponding to that of the tubular fibrous structure, the drape-molding/depositing being performed so that at least one group of fibers has a same orientation with respect to a longitudinal axis (A) of said tubular fibrous structure, wherein fibers from the at least one group of fibers are drape-molded/deposited over an angular sector smaller than a total periphery of the mandrel to form a discrete segment of fibers on the angular sector, an end of the fibrous structure being separated from the mandrel in order to enable further drape-molding on the mandrel and formation of the tubular fibrous structure with lobes.

2. The method according to claim 1, wherein a circumference of the mandrel corresponds to a shape of a portion of a fibrous structure comprising an area of revolution and an area forming at least two lobes.

3. The method according to claim 1, wherein the mandrel has a reduced shape corresponding, or fitting, to that of a portion of a final piece over a predetermined angular sector.

4. The method for manufacturing according to claim 1, wherein prior to drape-molding/depositing the fibers on the mandrel, a separation film is wound on the mandrel.

5. The method for manufacturing according to claim 4, wherein the separation film is separated from the mandrel at a same time as the tubular fibrous structure on which the separation film is supported.

6. The method for manufacturing according to claim 1 further comprising: impregnating the fibers by a matrix in the form of a unidirectional ribbon of fibers before the drape-molding/depositing; and after final winding of the fibers onto a tubular shape, curing by polymerization, or in the case of ceramic matrices by sintering or densification.

7. The method for according to claim 6, wherein the impregnation with the matrix occurs after the drape-molding/depositing over the tubular shape, wherein fibers embedded in a preform are in a resin adapted to be cured by polymerization.

8. The method for manufacturing according to claim 6, wherein a material forming the matrix is an organic matrix or a ceramic matrix.

9. The method for manufacturing according to claim 1, wherein a composite piece obtained from the tubular fibrous structure has an open portion, in which an angular sector is missing.

10. The method for manufacturing according to claim 1, further comprising separating the end of the fibrous structure from the mandrel and drape-molding/depositing another group of fibers onto the mandrel.

11. The method for manufacturing according to claim 1, further comprising drape-molding/depositing fibers from the at least one group of fibers to form at least one of the lobes of the tubular fibrous structure.

Description

DRAWINGS

(1) In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

(2) FIG. 1 represents a perspective view of a flow mixer for a turbojet engine according to the present disclosure;

(3) FIG. 2 represents a perspective view of a portion of the fibrous structure covering two lobes of the mixer of FIG. 1; and

(4) FIG. 3 illustrates a method for manufacturing the fibrous structure of FIG. 2.

(5) The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

(6) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

(7) In FIG. 1, there is represented a mixer for an aircraft turbojet engine, centered around a longitudinal axis A.

(8) Such a mixer typically comprises an upstream portion 1 (with respect to the direction of the air flow in operation, indicated by the arrow F) with a substantially circular cross-section, and a downstream portion 3 having recesses 5 and bosses 7, commonly called lobes 9.

(9) Such a mixer is intended to be disposed on the trailing edge of the nozzle separating the cold air flow from the hot air flow of an aircraft bypass turbojet engine, in order to achieve a better mixing of these two flows, and thus improve the acoustic performance and the consumption of the engine.

(10) According to the present disclosure, the mixer is made with a fibrous structure 11, shown more particularly in FIG. 2, formed of one or several non-woven fibrous structure(s) in particular with ceramic fibers, each non-woven fibrous structure comprising at least one group of fibers having the same orientation with respect to the axis A (the fibers of each such group being designated as “unidirectional”).

(11) The term “unidirectional” means overall layers of fibers or filaments disposed in wicks or laps and substantially parallel to each other.

(12) In FIG. 2, there is shown a first group of fibers 13 oriented with respect to the direction of the longitudinal axis A, and a second group of fibers 15 oriented with respect to a direction transverse to the axis.

(13) In another form, the fibrous structure 11 extends over all of the lobes of the mixer, possibly making several revolutions. In this way, the fibrous structure of the mixer is made in one piece, which avoids cutting and partially superimposing laps of fibrous structure as has been the case in the prior art.

(14) The fibrous structure may include between two lobes and up to a plurality of lobes, and these lobes may have different shapes.

(15) This fibrous structure may comprise several non-woven fibrous structures partially or totally superimposed or juxtaposed relative to each other.

(16) This fibrous structure may comprise fibers having a multitude of orientations, depending on mechanical and structural requirements.

(17) The material(s) forming said fibers are selected in particular from the group comprising glass, basalt, carbon, silicon carbide, aluminum oxides, aluminosilicates.

(18) In one form, the final piece obtained from the fibrous structure comprises an organic matrix or a ceramic matrix.

(19) The impregnation of the fiber by the matrix may be carried out at the level of a unidirectional ribbon of fibers before the deposition in the case of the so-called “pre-impregnated” methods and followed, after final winding on the tubular shape with scrolls, by a polymerization curing, or in the case of ceramic matrices by sintering or densification.

(20) The impregnation with the matrix may also be completed or completely carried out after the drape-molding on the tubular shape with scrolls by the RTM (Resin Transfer Molding) method, infusion, and more generally by any method allowing embedding the fibers of the preform in a resin suitable for polymerization curing, or in the case of ceramic matrices by sintering or densification.

(21) The mixer obtained with the fibrous structure according to the present disclosure may have lobes whose height is continuously increasing towards the downstream end of the piece.

(22) The sidewalls of the lobes may be according to any planes or in any shape.

(23) The mixer may have an open portion, in which an angular sector is missing.

(24) In FIG. 3, there is schematically represented a method for manufacturing the fibrous structure 11 of FIG. 1.

(25) As shown, a film 17 has been wound over several revolutions around a take-up mandrel 19.

(26) This mandrel is a kind of spool with a particular shape corresponding to the shape of the fibrous structure 11 to be made.

(27) By a fiber deposition head 21 mounted for example at the end of the arm 23 of a robot, the fibers having the different desired orientations with respect to the axis A of the tubular final piece are drape-molded/deposited over the film 17. Accordingly, a non-woven fibrous structure composed of unidirectional fibers is thus obtained.

(28) Once the fibers have been drape-molded over an angular sector smaller than the total periphery of the mandrel, one of the ends of the film 17 is detached from the mandrel, freeing the surface of the mandrel from the already drape-molded preform portion, in order to enable further drape-molding on the same mandrel and following the already drape-molded fibrous preform.

(29) Depending on the shape repetition of the lobes of the tubular piece, each fibrous structure may cover from 2 lobes or up to a full revolution or more than one revolution of the tubular piece.

(30) In particular, if the lobes are identical or if one out of two of the lobes are identical, it will be possible to constitute a full revolution at least of the piece with lobes with the same fibrous structure.

(31) Before or after winding on the molding tool whose shape corresponds to that of the final piece, the fibrous structure 11 may be impregnated with the material intended to form the composite matrix before being cured so as to obtain the final piece, namely the flow mixer.

(32) Following that is the curing of the matrix to stiffen the piece.

(33) Of course, the present disclosure is not limited to the described and represented form provided as an illustrative and non-limiting example.

(34) For example, such a mixer may also be used to mix two concentric flows in different fields (hydraulic or gas, without necessarily being hot, but with the same concerns for mixing, cost, etc.). The fibrous structure may be made of ceramic, organic (polyester, polyamide, polyethylene, etc.) metallic, glass, basalt, carbon, silicon carbide, aluminum oxides, aluminosilicates fibers.

(35) Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

(36) As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

(37) The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.