Composite part with smooth outer face and manufacturing method thereof

Abstract

A part for an aircraft turbojet engine nacelle is made of a composite material and includes at least one outer face (S1), a fibrous preform including fiber locks and having a surface(s) delimiting depressions between fiber locks, a covering material which at least partially covers the surface(s) of the fibrous preform and in particular the depressions, and a matrix which binds entirely the covering material and the fibrous preform. The covering material is a fibrous mat and the outer face (S1) is smooth. A method for manufacturing such a part includes manufacturing the fibrous preform, providing a fibrous mat, depositing the fibrous preform and fibrous mat in a mold, dispersing the matrix between the fibers of the preform and mat and consolidating the fibrous preform and mat.

Claims

1. A part for an aircraft turbojet engine nacelle, the part being made of a composite material and including at least one outer face, the part comprising: a fibrous preform including fiber locks and a surface defining depressions between the fiber locks, the depressions having a height between one and two times a height of the fiber locks; a covering material which at least partially covers the surface of the fibrous preform and the depressions; and a matrix which binds the covering material and the fibrous preform, wherein the covering material is an unwoven fibrous mat including at least one fiber extending substantially parallel to the at least one outer face of the part and above at least one of the depressions between the fiber locks of the fibrous preform, wherein the at least one outer face is smooth.

2. The part according to claim 1, wherein a thickness of the unwoven fibrous mat is smaller than half a thickness of the fiber locks of the fibrous preform.

3. The part according to claim 1, wherein a thickness of the unwoven fibrous mat is smaller than one fifth of a thickness of the fiber locks of the fibrous preform.

4. The part according to claim 1, wherein the fibrous preform includes ceramic fibers.

5. The part according to claim 1, wherein the fibrous preform includes ceramic fibers selected from the group consisting of carbides, borides, oxides, and silicides.

6. The part according to claim 1, wherein the fibrous preform includes silicon carbide (SiC) fibers.

7. The part according to claim 1, wherein the fibrous preform includes alumina or aluminosilicates-based fibers.

8. The part according to claim 1, wherein the fibrous preform includes at least 60% alumina-based fibers.

9. The part according to claim 1, wherein the matrix is a ceramic matrix.

10. The part according to claim 1, wherein the matrix is a ceramic matrix selected from the group consisting of carbides, borides, oxides, and silicides.

11. The part according to claim 1, wherein the matrix is a silicon carbide (SiC) matrix.

12. The part according to claim 1, wherein the matrix is an alumina or aluminosilicates-based matrix.

13. The part according to claim 1, wherein the matrix is at least 60% alumina-based matrix.

14. The part according to claim 1, wherein the unwoven fibrous mat includes ceramic fibers.

15. The part according to claim 1, wherein the unwoven fibrous mat includes ceramic fibers selected from the group consisting of carbides, borides, oxides, and silicides.

16. The part according to claim 1, wherein the unwoven fibrous mat includes silicon carbide (SiC) fibers.

17. The part according to claim 1, wherein the unwoven fibrous mat includes alumina-based fibers.

18. The part according to claim 1, wherein the unwoven fibrous mat includes at least 60% alumina-based fibers.

19. A method for manufacturing a part according to claim 1, the method comprising: manufacturing the fibrous preform; providing the unwoven fibrous mat; depositing the fibrous preform and the unwoven fibrous mat between two faces of a mold; dispersing the matrix between fibers of the fibrous preform and fibers of the unwoven fibrous mat; and consolidating the fibrous preform and the unwoven fibrous mat, wherein the matrix dispersed between the fibers of the fibrous preform and the fibers of the unwoven fibrous mat is heat-treated.

20. The manufacturing method according to claim 19, wherein the step of manufacturing the fibrous preform is performed in the mold.

21. The manufacturing method according to claim 19, wherein the unwoven fibrous mat is deposited on at least one of the two faces of the mold, and the step of manufacturing the fibrous preform is carried out in the mold, on the unwoven fibrous mat.

22. The manufacturing method according to claim 21, wherein the step of depositing the unwoven fibrous mat is repeated in the mold and on the fibrous preform such that the unwoven fibrous mat is on both faces of the fibrous preform.

23. The manufacturing method according to claim 19, wherein the step of providing the unwoven fibrous mat is carried out by scattering cut fibers on at least one of the mold and the fibrous preform.

24. The manufacturing method according to claim 19, wherein the consolidation step includes a thermomechanical treatment step.

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 is a schematic sectional view of a part made of a composite material according to the present disclosure;

(3) FIG. 2 is an enlarged schematic sectional view of a variant of a part made of a composite material according to the present disclosure;

(4) FIG. 3 is a schematic representation of a method according to the present disclosure;

(5) FIG. 4 is a schematic sectional view of a part made of a composite material disposed in the mold according to the present disclosure;

(6) FIG. 5 is a schematic sectional view of a variant of the part made of a composite material of FIG. 1; and

(7) FIG. 6 is a schematic perspective view of a nacelle incorporating a part made of a composite material according to the present disclosure.

(8) 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

(9) 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.

(10) FIG. 1 represents a part 10 made of a composite material, having a smooth outer face S1, and an inner face S2.

(11) The part 10 includes a fibrous preform 11, a fibrous mat 12, an alumina based ceramic matrix 13, which binds the entirety of the fibrous mat 12 and of the fibrous preform 11.

(12) The fibrous preform 11 includes four laps 30 of fibers grouped together in the form of fiber locks 11′.

(13) Each of these locks each includes a plurality of fiber filaments (not represented) disposed parallel to each other.

(14) The locks 11′ of the same lap 30 have various directions in the outer face plane S1.

(15) In the plane of the section of FIG. 1, some locks 11′ are parallel to the sectional plane (locks represented by serpentine shapes) and others are intersecting (locks represented by circles or ellipses).

(16) The fibrous preform 11 has a surface “s” delimiting depressions 14 between some locks 11′.

(17) The fibrous mat 12 includes fibers 15. It covers the surface “s” of the fibrous preform 11 and in particular the depressions 14.

(18) Because of the orientations and arrangements of locks 11′ and the rigidity of the fibers which inhibits them from being deformed without the risk of breaking, the depressions 14 have an increased width corresponding to the width of two locks, and a depth corresponding to the thickness of one to three laps 30 of locks 11′.

(19) In various forms, the fibrous mat 12 has a maximum thickness of half the thickness of a lap 30 of the fibrous preform 11, a thickness of one-third of the thickness of a lap 30 of the fibrous preform 11, or a thickness of one-fifth of the thickness of a lap 30 of the fibrous preform 11.

(20) The fibrous mat 12 includes fibers 15 randomly disposed and interconnected by any mechanical, physical and chemical means, but not woven or knitted.

(21) As example, the part 10 is made of a composite material with an aluminum oxides ceramic matrix and whose fibers of the fibrous preform 11 and of the fibrous mat 12 are alumina fibers, and in one form includes at least 60% of alumina, grouped together in locks 11′ with a linear density comprised between 3,000 and 20,000 deniers. The width of each fiber is generally smaller than 20 μm, and in one example the width of each fiber is between 10 and 15 μm.

(22) According to this example, the envelope section of fiber locks 11′ of the fibrous preform is substantially oval or ellipsoidal with a larger width comprised between 2 mm and 15 mm.

(23) A lap 30 of locks 11′ composed by alumina-based fibers having a density between 3.2 and 3.9, and a fiber volume ratio in the range of 50%, has a basis weight comprised between 80 g/m.sup.2 and 250 g/m.sup.2 and a thickness comprised between 0.08 and 0.3 mm.

(24) In the case of woven locks 11′, a lap of woven locks of the fibrous preform 11 may have a thickness comprised between 0.15 and 0.4 mm.

(25) The depressions 14 have a maximum width in the range of 1 to 30 mm in width and in the range of 0.1 mm to 1 mm in depth.

(26) Still according to this example, the fibrous mat 12 has a basis weight comprised between 10 and 70 g/m.sup.2 of alumina fibers, such as for example, a basis weight between 15 and 50 g/m.sup.2; and a thickness comprised between 0.02 and 0.3 mm, such as for example, between 0.03 and 0.15 mm.

(27) In a variant represented in FIG. 2, the fibers 15 of the fibrous mat 12 are long fibers disposed in planes parallel to the outer face S1 of the part 10.

(28) Furthermore, the fibers 15 of the fibrous mat 12 extend over at least two locks 11′ of the fibrous preform, covering at least one depression 14.

(29) The fibrous mat 12 includes at least one fiber 15 whose length is longer than the largest width of the depressions 14 between the locks 11′ of the fibrous preform 11.

(30) At least one portion of the fibers 15 of the fibrous mat 12 has a length comprised between 2 and 30 mm.

(31) In one form, the fibrous mat 12 is made from fiber locks with an initial linear density comprised between 1,000 and 20,000 deniers. The locks are spread out, so as to distribute their constituent fibers so as not to have more than 100 fibers clusters parallel to each other, or less than 100 deniers.

(32) The locks may also be cut so as to have lengths of fibers of about 15 mm.

(33) In another form, the fibrous mat 12 includes at least 50% of total mass comprising fibers with lengths longer than 15 mm.

(34) In still another form, the fibrous mat 12 includes more than 50% fibers of lengths comprised between 15 and 50 mm.

(35) The fibers 15 of the fibrous mat 12 are randomly oriented in multiple directions in the plane of the fibrous mat, and distributed so that: in any 5 mm.sup.2 surface of the fibrous mat, at least five fibers clusters may be observed in different directions.

(36) In another form, the fibers 15 are distributed and crossed with each other in the fibrous mat 12 so that there is no gap between fibers longer than 2 mm and wider than 1 mm.

(37) In yet another form, the fibers of the fibrous mat are bound together by a water-soluble product, for example a polyvinyl or glycol polyethylene alcohol based product.

(38) FIG. 3 illustrates one form of the method for manufacturing the part 10 as previously described, in which the first step is a step of manufacturing 20 the fibrous preform 11, by depositing laps 11′ of fibers in a mold M including a first face 16 and a second face 17 (FIG. 4).

(39) During this step 20 of manufacturing the fibrous preform, the laps 11′ are deposited on the first face 16 of the mold (FIG. 4)

(40) The first face 16 and the second face 17 have complementary shapes.

(41) Then a step 21 of depositing a fibrous mat 12 is carried out on said fibrous preform 11 and the mold M is closed so that the first face 16 and the second face 17 trap the fibrous mat 12 and the fibrous preform 11. In this step, the fibrous mat 12 may cover opposite faces of the fibrous preform 11 thereby covering depressions 14 between the fibers of each face of the fibrous preform 11.

(42) Afterwards, an injection step 22 is performed, in which the ceramic matrix 13 is injected in solution in a binder, into the mold M so as to fill the depressions 14.

(43) This injection step 22 is followed by a step 23 of consolidating the assembly formed by the fibrous preform 11, the fibrous mat 12 and the matrix 13, by thermomechanical treatment.

(44) The consolidation step 23 is carried out in the mold M.

(45) Alternatively, the consolidation step is carried out after demolding.

(46) In the example of a composite part with an alumina oxides-based ceramic matrix, the thermomechanical treatment includes a step of drying the matrix and eliminating the binder products and organic residues by steaming of the set formed by the fibrous preform 11, the fibrous mat 12 and the matrix 13, between 30° C. and 500° C. for 0.2 to 150 h.

(47) Afterwards, the thermomechanical treatment includes a step of sintering 24 at least partially the matrix by heat treatment between 1000° C. and 1400° C., for 5 to 60 minutes in order to generate bonds between each grain of the matrix, and between the matrix and the fibers of the fibrous preform and the fibrous mat.

(48) In one variant, the fibrous mat 12 is previously pre-impregnated with matrix 13 before the step of depositing 21 on the fibrous preform 11.

(49) In another variant, it is possible to locally drape two superimposed fibrous mats 12 to provide complete coverage of the fibrous preform 11 on non-developable shapes that cannot be integrally covered by the fibrous mat 12.

(50) In another variant, the fibrous mat 12 is produced by scattering cut fibers 15 with an aqueous binder, directly on at least one of the mold M and the fibrous preform 11.

(51) The first face 16 or the second face 17 of the mold is a semi-rigid tarpaulin.

(52) In another form of the method, the first step is a step of depositing (21) the fibrous mat on the first face 16 of the mold M then the fibrous preform 11 is manufactured by depositing laps 11′ of fibers on the fibrous mat 12.

(53) As illustrated in FIG. 4, the third step 22 is performed by introducing the matrix and its binder through an inlet point 18 located on the second face 17 of the mold M.

(54) Furthermore, the second face 17 of the mold M includes at least one vent 19 enabling the exit of gas, solvents, or binder liquids, so as to press the fibrous mat 12 against the second face 17.

(55) Moreover, the first face 16 of the mold M includes at least one vent 19 enabling the exit of gas, solvents, or binder liquids, so as to press the fibrous mat 12 against the second face 17, and enabling the flow of matrix between the fibers of the fibrous mat 12 and of the fibrous preform 11.

(56) In another form of the method, the vents 19 are micro-perforations over all of the faces of the mold M which allows uniformly pressing the fibrous mat 12 onto the second face 17.

(57) FIG. 5 illustrates a variant 100 of the part made of a composite material, having a smooth outer face S1 and inner face S2.

(58) The part 100 includes a fibrous preform 11, a fibrous mat 12, and an alumina-based ceramic matrix 13, which binds the entirety of the fibrous mat 12 and of the fibrous preform 11, the fibrous mat 12 covering the two faces of the fibrous preform 11.

(59) The fibrous preform 11 has a surface “s,” on each of its faces, delimiting depressions 14 between some locks 11′ of fibers.

(60) The fibrous mat 12 includes fibers 15. It covers the surface “s” of the fibrous preform 11 and in particular the depressions 14, on each face of the fibrous preform 11.

(61) The other features of the part 10 made of a composite material, described with reference to FIG. 1, are applicable to the part 100 according to the variant of FIG. 5.

(62) FIG. 6 illustrates a nacelle 200 for a turbojet engine 400, including a part 10 made of a composite material according to the present disclosure, as previously described.

(63) The turbojet engine 400 is connected to an aircraft (not represented) by a mast 300.

(64) In one variant, the nacelle 200 includes a part 100 made of a composite material as described with reference to FIG. 5.

(65) 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.

(66) 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.”

(67) 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.