METHOD FOR MANUFACTURING A FIBROUS PREFORM FOR THE PRODUCTION OF A PART IN COMPOSITE MATERIAL

Abstract

The present invention relates to a method for manufacturing a fibrous preform comprising a conical or frustoconical portion and a stack of fiber layers (502, 504, 506, 508). The method comprises the steps of: - flat draping the fiber layers to form at least one fibrous blank (T50), the fiber layers each having one curved edge (502a, 504a, 506a, 508a; 502b, 504b, 506b, 508b) and two straight edges (502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d), and predetermined dimensions such that the fibrous blank has two circumferential ends (52, 54), each with a stepped shape, and - shaping of The fibrous blank is placed on a conical or frustoconical surface of a forming tool, such that the circumferential ends of the fibrous blank overlap each other by complementary shape. Figure for the abbreviation: Fig. 9

Description

Title of the invention: METHOD FOR MANUFACTURING A FIBROUS PREFORM FOR THE PRODUCTION OF A PART MADE OF COMPOSITE MATERIAL Technical field of the invention

[0001] The present invention relates to the general field of manufacturing composite parts, particularly for aircraft turbomachinery. More specifically, the invention relates to a method for manufacturing a fibrous preform for producing such composite parts. Technical background

[0002] Increasingly, parts, particularly in the aeronautical sector, are being made of composite materials. The use of composite materials is particularly advantageous because they allow for a reduction in component mass combined with good mechanical properties.

[0003] A composite material typically comprises a fibrous reinforcement densified by a matrix. The fibrous reinforcement may be obtained from a three-dimensional (3D) weave or by stacking (or draping) and superimposing several layers / plies (multilayer). The matrix may be obtained by transforming a matrix precursor, for example, by heat treatment.

[0004] By way of example, an exhaust nozzle, a fan housing, and / or an intermediate housing in an aircraft turbomachine can be made of composite material. The manufacture of such turbomachine parts generally begins by draping a succession of fiber layers onto a shaped or flat mold to create the fibrous preform, which has a layered shape. The manufacturing process continues with the formation of a matrix phase within the porosity of the fibrous preform. The matrix can, in particular, be formed by chemical vapor infiltration or by sintering a matrix precursor.

[0005] In some current techniques, draping is performed manually by an operator. These techniques can lead to relatively high production costs and risks of errors in fiber layer positioning. This can result in some variability in the mechanical performance of the resulting parts, or lead to parts with insufficient mechanical properties.

[0006] Automated solutions have thus been developed to reduce the production cost of draping these composite material parts, such as the automatic fiber placement technique (known by the acronym AFP for "Automated Fiber Placement") or the automatic tape placement technique (known by the acronym ATL for "Automated Tape Laying").

[0007] By way of example, a fibrous preform for manufacturing a part from a composite material is obtained by draping layers of woven fibers over a mold having the final shape of the composite part to be produced, each layer of woven fibers having the shape of a ring sector, the layers being stacked one on top of the other. However, this first solution, which consists of forming a fibrous preform from a multitude of sectors, implies multiple overlaps at the different junction zones in order to allow the transfer of forces between the layers. These overlaps induce a significant additional mass. Furthermore, another drawback is that the layers of woven fibers cannot maintain the angular orientations on a cone-like geometric shape, particularly during the shaping process to form the fibrous preform.

[0008] According to another example, the fibrous preform is obtained by draping layers of fibers in the form of unidirectional ribbons over a mold having the final shape of the composite part to be produced, particularly a conical or frustoconical shape in the case of a turbomachine exhaust nozzle. Although this second solution suffers much less from the problem of deformation of the fiber layers due to their reduced width, it can prove more complex to implement. In particular, the ribbon deposition speed must be relatively low to allow for proper draping over the curved surface of the mold. Furthermore, another drawback is that the ends of the ribbons may not remain parallel to each other, and thus may not adhere to the mold surface.

[0009] In this context, it is interesting to propose a solution to overcome the disadvantages of the prior art, by proposing a reliable draping solution to strengthen the mechanical strength and lifespan of a fibrous preform for the production of a part in composite material, in particular for an aircraft turbomachine, while maintaining a reduced mass. Summary of the invention

[0010] The present invention proposes a simple, effective and economical solution to the aforementioned disadvantages of the prior art.

[0011] To this end, the invention proposes a method for manufacturing a fibrous preform for the production of a part in composite material, in particular for an aircraft turbomachine, this fibrous preform comprising at least one portion of conical or frustoconical shape, and which extends around a longitudinal axis X5, the fibrous preform comprising a stack of several layers of fibers in thickness.

[0012] According to the invention, the method comprises: - a step (a) of flat draping the layers of fibers over a draping tool to form at least one flat fiber blank, the fiber layers each having an angular sector shape comprising at least one curved edge and two straight edges joined together by said curved edge, the fiber layers having predetermined dimensions such that each layer of fiber draped over a previously draped layer of fibers has its straight edges set back from the straight edges of the previously draped layer of fibers, so that said at least one fiber blank has two circumferential ends each having a stepped shape and thus steps are formed by the straight edges of the fiber layers, and - a step (b) of shaping said at least one fiber blank on a conical or frustoconical surface of a shaping tool,so that the circumferential ends of said at least one fibrous rudiment overlap each other by complementary shape.

[0013] Thus, this solution makes it possible to achieve the aforementioned objective by providing overlap of the ends of the fiber layers, while avoiding the formation of excess thickness. In general, the fibrous preform obtained by the manufacturing process exhibits optimal mechanical strength while maintaining a low mass. To this end, the fibrous preform is obtained by flat-draping one or more fibrous blanks having two circumferential ends in a stepped shape. This stepped shape of the circumferential ends can correspond, for example, to a bevel extending discontinuously. This bevel can also be referred to by the English term "scarf" or "step".A scarf joint is a specific assembly configuration for at least two elements, in which the ends of these elements to be joined interlock, primarily through their contact surfaces, which may be beveled, chamfered, or angled. The fiber blank(s) are then shaped by joining their circumferential ends so that they overlap (or, in other words, interlock) through complementary shapes. This allows for the perfect alignment of the circumferential ends of a single fiber blank or of several fiber blanks placed side by side on a conical or truncated conical surface of a forming mold, thus creating a stronger bond. This assembly of the circumferential ends through complementary shapes also allows for better distribution of stresses over a larger surface area. compared to a simple butt joint, and better able to withstand environmental variations (such as thermal expansion).

[0014] Furthermore, the process can be easily and optimally carried out by an automated machine, particularly with fiber layer deposition parameters that can be more easily adjusted. This makes it possible to efficiently produce a fibrous preform with at least one predetermined conical or frustoconical portion that can be perfectly used for manufacturing a composite part.

[0015] The method according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0016] — the angular sector, configured to realize, for example, the portion of shape conical of the fibrous preform, includes a curved edge called concave connecting the two straight edges to each other;

[0017] — the angular sector, configured to realize, for example, the portion of shape frustoconical of the fibrous preform, comprises two curved edges, respectively concave and convex, which are connected together by the two straight edges;

[0018] — each of the circumferential ends has a decreasing thickness radially along a circumferential direction;

[0019] - the draping of step (a) forms a single fibrous blank or several blanks fibrous which are arranged circumferentially next to each other around the X5 axis in step (b);

[0020] — in step (a), the layers of fibers are draped flat with dimensions predetermined identical and circumferentially offset from each other, so that at least one of the two circumferential ends has straight edges of each layer of fiber draped over the previously draped layer of fiber that are set back from the straight edges of this previously draped layer of fiber;

[0021] - in step (a), the layers of fibers are draped flat with dimensions predetermined identical and circumferentially offset from each other, so that: - at one of the two circumferential ends, the straight edges of each layer of fibers draped over the previously draped layer of fibers are set back from the straight edges of this previously draped layer of fibers, and - at the other of the two circumferential ends, the straight edges of each layer of fibers draped over the previously draped layer of fibers extend beyond the straight edges of this previously draped layer of fibers;

[0022] - in step (a), the layers of fibers are draped flat with dimensions predetermined, different and centered with respect to each other along the same axis P of symmetry;

[0023] - in step (b), at least one first fibrous rough-out among said several fibrous blanks are arranged in the opposite direction to at least one second fibrous blank of said several fibrous blanks, so that the circumferential ends of said first and second fibrous blanks overlap each other by complementarity of form;

[0024] - the process further comprises a step (c) of compacting the ends circumferential to each other;

[0025] - each of the fiber layers comprises unidirectional and oriented fibers in directions different from the unidirectional fibers of the other fiber layers, step (a) being carried out by draping the fiber layers along directions different from the unidirectional fibers of the other fiber layers;

[0026] — each of the fiber layers comprises unidirectional and oriented fibers in directions similar to unidirectional fibers of the other fiber layers, wherein step (a) is carried out by draping the fiber layers in a direction similar and parallel to that of the unidirectional fibers of the other fiber layers;

[0027] - the conical or frustoconical surface used in step (b) is an external surface of shaping tools;

[0028] - the conical or frustoconical surface used in step (b) is an internal surface of shaping tools;

[0029] - the method further comprises a step (i) of reinforcing at least a part of the fibrous preform by adding filaments or fibers through the layers of fibers, this step (i) being carried out after step (a) or after step (b);

[0030] - step (i) is carried out at least at the circumferential ends of said at least a fibrous rough draft;

[0031] - the fibre layers are pre-impregnated with a matrix precursor;

[0032] - the draping of step (a) is carried out automatically, for example by placement automatic fiber placement (AFP) or automatic fiber layer placement (ATL);

[0033] — the process further comprises a densification step (d) by impregnation of the fibrous preform, in particular obtained at the end of step (b) or step (c), with a matrix precursor;

[0034] — the fibrous preform comprises ceramic fibers (such as oxide fibers or silicon carbide), carbon fibers, glass fibers, polyamide fibers, aramid fibers, or a mixture of at least two of these fibers;

[0035] — the ceramic fibers are based on alumina oxide (Al2O3).

[0036] The invention may also relate to a fibrous preform for the production of a part in composite material, in particular for an aircraft turbomachine, this fibrous preform being obtained by the manufacturing process according to one of the features of the invention.

[0037] The fibrous preform may include at least one conical or frustoconical portion extending around a longitudinal axis X5, and this fibrous preform comprises in thickness a stacking of several layers of fibers.

[0038] The fibrous preform (in particular the conical or truncated conical portion) can be formed by at least one or more fibrous blank(s) having circumferential ends each having a stepped shape and overlapping each other by complementary shape.

[0039] The invention may further relate to a composite material part, in particular for an aircraft turbomachine, comprising a fibrous preform made according to one of the features of the invention. This composite material part may be an exhaust nozzle, a fan housing and / or an intermediate housing of the turbomachine. Brief description of the figures

[0040] The invention will be better understood and other details, features and advantages of the invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0041] [Fig. 1] is a schematic perspective and partial cross-sectional view of an aircraft turbomachine comprising at least one part made of composite material according to the invention,

[0042] [Fig.2] is a schematic perspective view representing an example of a composite material part of [Fig.1], which is an exhaust nozzle of the turbomachine,

[0043] [Fig.3] is a partial schematic cross-sectional view representing a first example of a fibrous preform according to the invention which is used for the production of the composite material part of [Fig.2],

[0044] [Fig. 4] is a partial schematic cross-sectional view representing a second example of the fibrous preform according to the invention,

[0045] [Fig. 5] is a block diagram representing the steps involved in a manufacturing process for the fibrous preform according to the invention,

[0046] [Fig.6] is a partial schematic view of a draping step of a layer of fibres of the process of [Fig.5],

[0047] [Fig.7] is a schematic view representing a first example of a fibrous blank obtained by a first draping method of the process according to the invention,

[0048] [Fig.8] is a schematic view partially representing a second example of a fibrous blank obtained by a second draping method of the process according to the invention,

[0049] [Fig.9] is a schematic view representing the second draping method and the resulting fibrous blank,

[0050] [Fig. 10] is a schematic perspective view representing a shaping step of the fibrous blank of [Fig. 7] or 9 on a first example of shaping tooling,

[0051] [Fig. 11] is a schematic perspective view representing a shaping step of the fibrous blank of [Fig. 7] or 9 on a second example of shaping tooling,

[0052] [Fig. 12] is a schematic view representing a first mode of shaping the fibrous blank of [Fig. 9],

[0053] [Fig. 13] is a schematic view representing a second method of shaping several fibrous blanks of [Fig. 9],

[0054] [Fig. 14] is a schematic view representing a step of strengthening at least part of the fibrous blank according to the process of [Fig. 5],

[0055] [Fig.15] is a partial schematic cross-sectional view of a first method of reinforcing the fibrous blank according to the invention,

[0056] [Fig.16] is a partial schematic and cross-sectional view of a second method of strengthening the fibrous blank according to the invention.

[0057] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0058] Generally, in this application, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis (such as that of the composite material part or the turbomachine). The term "radial" refers to the orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner" and "outer," and "internal" and "external," are used with reference to positioning relative to a radial axis. Thus, a structural element extending along the longitudinal axis has an inner surface facing the longitudinal axis and an outer surface opposite its inner surface.

[0059] The invention can be applied generally to any part 5 made of composite material, in particular for an aircraft turbomachine 10.

[0060] The turbomachine 10 can be a turbojet, a turboprop or a turbomotor.

[0061] Fig. 1 illustrates an example of an aircraft turbomachine 10 extending along a longitudinal axis Xio.

[0062] The turbomachine 10 may include, from upstream to downstream, a blower 11 (or in other words a propeller), at least one compressor (such as a low pressure compressor 12 and a high pressure compressor 13), a combustion chamber 14, at least one turbine (such as a high pressure turbine 15 and a low pressure turbine 16), and optionally a gas exhaust nozzle 17.

[0063] The blower 11 can be surrounded by a blower housing 20, and the low-pressure compressor 12 can also be surrounded by an intermediate housing 30. These blower housings 20 and intermediate housings 30 can extend around the axis Xio-

[0064] The nozzle 17 may include an external shielding housing 40 (also referred to as the "plug"). Figure 2 illustrates a non-limiting example of this shielding housing 40, which may be a part of revolution extending about the axis Xi0. In particular, the shielding housing 40 may have a frustoconical shape extending about the axis Xi0.

[0065] The fan casing 20, the intermediate casing 30 and / or the shielding casing 40 of the nozzle 17 can be made of composite material. Thus, at least one of these parts of the turbomachine 10 can constitute, without limitation, the composite material part 5 of the invention.

[0066] Part 5 may include a fibrous preform 50 obtained by a manufacturing process as described below.

[0067] The fibrous preform 50 comprises at least one conical or frustoconical portion extending around a first axis X5. This first axis X5 may substantially coincide with the longitudinal axis Xi0 of the turbomachine.

[0068] This fibrous preform 50, in particular the conical or truncated conical portion as illustrated in [Fig.2] with reference to the shielding housing 40, allows us to define: - a longitudinal direction, corresponding to the first axis X5, - a radial direction R5 substantially perpendicular to the first axis X5, and - a circumferential direction C5 around the first axis X5.

[0069] The fibrous preform 50 comprises in thickness a stacking of several layers of fibers 502, 504, 506, 508. The layers of fibers 502, 504, 506, 508 can be stacked and arranged radially along the radial direction R5.

[0070] The stacking of the fiber layers 502, 504, 506, 508 may comprise at least two fiber layers (Figures 2 and 3), such that at least one fiber layer lower 502 (hereinafter lower layer 502) and at least one upper fiber layer 504 (hereinafter upper layer 504) are superimposed one on top of the other.

[0071] The stacking of fiber layers 502, 504, 506, 508 may comprise more than two fiber layers. In particular, at least one or more intermediate fiber layers 506, 508 (hereinafter referred to as intermediate layer(s) 506, 508) may be located between the lower layer 502 and the upper layer 504. By way of example, [Fig. 4] illustrates the fibrous preform 50 which may comprise two intermediate layers 506, 508 between the lower layer 502 and the upper layer 504.

[0072] Each of the fiber layers 502, 504, 506, 508 may include unidirectional fibers that are oriented in a different direction from the unidirectional fibers of the other fiber layers 502, 504, 506, 508.

[0073] Alternatively, each of the fiber layers 502, 504, 506, 508 may include unidirectional fibers that are oriented in a direction similar and parallel to that of the unidirectional fibers of the other fiber layers 502, 504, 506, 508.

[0074] The unidirectional fibers of each of the fibrous layers 502, 504, 506, 508 can each be oriented according to a predefined orientation angle. These orientation angles can vary according to the desired stiffness properties for the fabrication of the fibrous preform 50. Each of the orientation angles of the unidirectional fibers can vary between 0° and ±90° with respect to a reference axis of the plane of a fiber layer. For example, these orientation angles can each be chosen from the values ​​of 0°, +30°, -30°, +45°, -45°, +60°, -60°, +90° and -90°.

[0075] The fibrous preform 50, and preferably each layer of fibers 502, 504, 506, 508, may comprise ceramic fibers (such as silicon oxide or silicon carbide fibers), carbon fibers, glass fibers, polyamide fibers, aramid fibers, or a mixture of at least two of these fibers. Preferably, the fibrous preform 50 (and preferably each layer of fibers) may comprise ceramic fibers, such as oxide fibers. By way of example, the ceramic fibers may be based on alumina oxide, or alumina (Al₂O₃). Even more preferably, the fibrous preform 50 (and preferably each layer of fibers) may comprise predominantly ceramic fibers.By "majority", we understand that the proportion by weight of ceramic fibers is greater (for example, greater than 50% by weight) than the proportion by weight of the remaining components of the fibrous preform or corresponding fiber layer (such as other fibers).

[0076] The fibrous preform 50 can be densified by a matrix 509 to form the final part made of composite material. This matrix ensures cohesion between the fibers of the fiber layers.

[0077] The composite material part 5 may comprise a ceramic matrix (CMC acronym for Ceramic Matrix Composite) or an organic matrix (CMO acronym for Organic Matrix Composite).

[0078] Advantageously, the composite material part 5 may include the ceramic matrix. By way of example, the ceramic matrix may be provided and formed by one of the following techniques: - by chemical vapor infiltration (CVI, or Chemical Vapor Infiltration), - by infiltration of the fibrous preform by a slip containing ceramic particles, then infiltration by a composition including molten silicon, - by infiltration of the fibrous preform by a slip loaded with ceramic particles, then sintering of the ceramic particles.

[0079] Each of the fiber layers 502, 504, 506, 508 can be pre-impregnated with a matrix precursor. This precursor can be intended to form the matrix 509. Alternatively, each of the fiber layers 502, 504, 506, 508 can be dry (i.e., without prior impregnation of the matrix precursor).

[0080] The precursor can be a resin when part 5 is made with an organic matrix.

[0081] At least one stack of the fiber layers 502, 504, 506, 508 can form a fiber blank T50, T50a, T50b. In particular, the fiber preform 50 can comprise a single fiber blank T50, T50a, T50b, or several fiber blanks T50a, T50b arranged circumferentially side by side around the first axis X5, overlapping each other. This fiber blank(s) can form the fiber preform, and consequently the fiber reinforcement of the composite material part 5, which provides its mechanical strength.

[0082] Each fibrous blank T50, T50a, T50b can include two circumferential ends 52, 54. In the examples in Figures 2 to 4, the fibrous preform 50 can include a first circumferential end 52 and a second circumferential end 54 extending opposite this first circumferential end 52.

[0083] One of the features of the invention is that each of these circumferential ends 52, 54 has a stepped (or beveled) shape and overlaps by complementary shape with another circumferential end 52, 54.

[0084] When the fibrous preform 50 is formed by a single fibrous blank T50, T50a, T50b, the first 52 and second 54 circumferential ends of a single and same fibrous blank T50, T50a, T50b can be connected to each other by complementarity of shape around the first axis X5.

[0085] When the fibrous preform 50 is formed of several fibrous blanks circumferentially connected next to each other with reference to [Fig.2], the circumferential ends 52, 54 of at least one of the several fibrous blanks Tsoa, T50b can each be connected to a circumferential end 52, 54 of another of the several fibrous blanks T50a, T50b by complementarity of shape around the first axis X5.

[0086] Each of the circumferential ends 52, 54 may have a thickness E52, E54 (measured along the radial direction R5) which decreases radially discontinuously along the circumferential direction C5. The thickness E52, E54 may decrease radially inwards or outwards along the circumferential direction C5.

[0087] Alternatively, one of the thicknesses E52, E54 can decrease radially inwards, and the other of the thicknesses E52, E54 can decrease radially outwards. In the examples of Figures 2 to 4, and without limitation, the thickness E52 of the first circumferential end 52 can decrease radially inwards along the circumferential direction C5, and the thickness E54 of the second circumferential end 54 can decrease radially outwards. This allows these two circumferential ends 52, 54 to be connected by complementary shape.

[0088] Advantageously, the fibrous preform 50 may include at least one or more reinforcing element(s) 500. Each reinforcing element 500 may extend through the fiber layers 502, 504, 506, 508, for example along the radial direction R5 ([Fig. 3]). This reinforcing element 500 thus enhances the mechanical strength of the fibrous preform 50.

[0089] The reinforcing element 500 can be located at least at the circumferential ends 52, 54. This makes it possible to reinforce the cohesion of the fiber layers at the connection of the circumferential ends 52, 54.

[0090] The reinforcing element 500 can be located on a portion 51 of the fibrous preform 50 illustrated in [Fig. 2]. This portion 51 can correspond to an upper part of the composite material component 5, intended in particular for installation under an aircraft wing. This prevents cracking of this upper part of the component 5, which is generally subjected to thermal shocks due to rain and / or hail.

[0091] The reinforcing element 500 can be located over the entire fibrous preform 50.

[0092] The reinforcing element 500 may include filaments or fibers 510. These filaments or fibers 510 can extend through the layers of fibers 502, 504, 506, 508. [Fig.3] illustrates, in a non-limiting way, filaments or fibers 510 extending through lower fiber layers 502 and upper fiber layers 504, at the level of the first 52 and second 54 circumferential ends.

[0093] The filaments or fibers 510 can be made of ceramic (such as alumina oxide) or of another material compatible with the fiber layers (such as carbon fibers, glass fibers, polyamide fibers, aramid fibers, etc.).

[0094] The filaments or fibers 510 can be integrated by the "tufting" technique ([Fig.15]) or the needle-punching technique ([Fig.16]), which are described below.

[0095] The present application will now describe a method for manufacturing the fibrous preform 50, as described above with reference to Figures 2 to 4. This fibrous preform 50 can be used to produce the part 5 in composite material, as illustrated in [Fig.2].

[0096] Fig. 5 summarizes the successive steps of the manufacturing process of the fibrous preform 50, with optional steps being represented by dotted lines.

[0097] The manufacturing process includes a step (a) of flat draping the layers of fibers 502, 504, 506, 508 on a draping tool 6 to form at least one flat fibrous blank T50, T50a, T50b.

[0098] Step (a) can be carried out by draping at least two layers of fibers 502, 504, 506, 508 flat. In the examples shown in Figures 7 to 13, and without limitation, four layers of fibers 502, 504, 506, 508 can be draped flat and one on top of the other during step (a). The number of fiber layers draped in step (a) can vary depending on the desired dimensions of the fibrous preform 50 to be produced to form the composite part 5.

[0099] The fiber layers 502, 504, 506, 508, which are draped in step (a), may be pre-impregnated with the matrix precursor. Alternatively, these fiber layers 502, 504, 506, 508 may be dry. In this alternative, a matrix precursor may be injected into the fibrous preform 50 to densify (or sinter) and consolidate this fibrous preform 50 and thus form the composite part 5.

[0100] The draping of step (a) can be carried out automatically, for example by automatic fiber placement (AFP) or by automatic fiber layer placement (ATL).

[0101] With reference to [Fig.6], the draping tooling 6 may include a support having a flat surface 60 on which the layers of fibers 502, 504, 506, 508 are draped flat. These layers of fibers 502, 504, 506, 508 may be deposited by a fiber application machine 62, such as is used in the AFP or ATL technique.

[0102] The flat surface 60 defines a Cartesian plane comprising a second X-axis and a third Y-axis. A fourth Z-axis, together with the X and Y axes, defines a Cartesian coordinate system. A circumferential direction C50, lying in the XY plane, defines the direction along which the curved edges of the fiber layers extend.

[0103] The layers of fibers 502, 504, 506, 508 thus draped in step (a) each have an angular sector shape having at least one curved edge 502a, 504a, 506a, 508a; 502b, 504b, 506b, 508b, and two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d which are connected together by this curved edge 502a, 504a, 506a, 508a; 502b, 504b, 506b, 508b.

[0104] In particular, the first circumferential end 52 may have a first straight edge 502c, 504c, 506c, 508c; and the second circumferential end 54 may have a second straight edge 502d, 504d, 506d, 508d opposite to this first straight edge.

[0105] The angular sector may include a first concave curved edge 502a, 504a, 506a, 508a.

[0106] According to a first embodiment, the angular sector configured to form, for example, the conical portion of the fibrous preform 50, may include the first curved edge 502a, 504a, 506a, 508a. This first curved edge 502a, 504a, 506a, 508a may connect the two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d to each other. In the configuration of the conical portion, the two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d can be connected, on the one hand, to the first curved edge 502a, 504a, 506a, 508a, and on the other hand, to a tip of the angular sector.

[0107] The angular sector may further include a second convex edge 502b, 504b, 506b, 508b. The first 502a, 504a, 506a, 508a and second 502b, 504b, 506b, 508b edges may be connected together by the two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d.

[0108] According to a second embodiment, the angular sector configured to realize, for example, the truncated cone-shaped portion of the fibrous preform 50, comprises the two curved edges, respectively, concave 502a, 504a, 506a, 508a and convex 502b, 504b, 506b, 508b, which are connected together by the two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d. In the examples in Figures 6 to 13, the concave edges 502a, 504a, 506a, 508a, may have dimensions (such as a circumferential extent) greater than those of the convex edges 502b, 504b, 506b, 508b.

[0109] In the embodiment shown in Figures 8 and 9, the fiber layers 502, 504, 506, 508 have predetermined dimensions (such as a circumferential extent), so that each fiber layer 502, 504, 506, 508 draped over a previously draped fiber layer 502, 504, 506, 508 has its straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d which are set back from the straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d of the previously draped fiber layer, and in such a way that at least one T50 fibrous rough , T5oa, T50b have the two circumferential ends 52, 54 each presenting the stepped shape.

[0110] Steps are thus formed by the straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d of the fiber layers. In particular, the first circumferential end 52 may include first steps formed by the first straight edges 502c, 504c, 506c, 508c; and the second circumferential end 54 may include second steps formed by the second straight edges 502d, 504d, 506d, 508d.

[0111] The thickness of each of the circumferential ends 52, 54, measured along the Z-axis, can decrease as one approaches the other circumferential end. After shaping the fibrous blank to form the fibrous preform 50, the thickness E52, E54 of each of the circumferential ends 52, 54, measured along the radial direction R5, can decrease as one approaches the other circumferential end.

[0112] Step (a) can be carried out by draping the fiber layers 502, 504, 506, 508 in a direction (or orientation) different from that of the unidirectional fibers of the other fiber layers 502, 504, 506, 508. By way of example, at least one of the four fiber layers 502, 504, 506, 508 illustrated in Figures 7 to 9 may have a fiber orientation angle different from that of at least one other of the four fiber layers. As another example, the four fiber layers 502, 504, 506, 508 may have different fiber orientation angles.

[0113] Alternatively, step (a) can be carried out by draping the layers of fibers 502, 504, 506, 508 along a direction (or orientation) similar and parallel to that of the unidirectional fibers of the other layers of fibers 502, 504, 506, 508. By way of example, the four layers of fibers 502, 504, 506, 508 illustrated in [Fig.7] can have identical fiber orientation angles.

[0114] In step (a) and according to a first draping method ([Fig.7]), the layers of fibers 502, 504, 506, 508 can be draped flat with identical predetermined dimensions, and these layers of fibers are draped circumferentially offset from one another so that: - at the first circumferential end 52, the straight edges 504c, 506c, 508c of each layer of fibers 504, 506, 508 draped over the previously draped layer of fibers 502, 506, 508 are recessed relative to the straight edges 502c, 506c, 508c of this previously draped layer of fibers, and - at the level of the second circumferential end 54, the straight edges 504d, 506d, 508d of each layer of fibers 504, 506, 508 draped over the layer of fibers 502, 506, 508 previously draped extend beyond (or in other words, protrude) the straight edges 502d, 506d, 508d of this previously draped layer of fibers.

[0115] This first draping method is illustrated in a non-limiting manner in [Fig. 7], in which circumferential extents a502, a504, a506, a508, as predetermined dimensions of the fiber layers 502, 504, 506, 508, are identical. The term "circumferential extent" refers to the largest dimension of the angular sector of the fiber layers, in particular between the two straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 506d. Each of the fiber layers 502, 504, 506, 508 is also draped in a staggered manner relative to the other fiber layers, in particular to form the circumferential ends 52, 54 in a stepped fashion.

[0116] In step (a) and according to a second draping method (Figures 8 and 9), the layers of fibers 502, 504, 506, 508 can be draped flat with different predetermined dimensions, and these fiber layers are draped centered with respect to each other along the same axis P, called the axis of symmetry, belonging to the XY plane. The circumferential ends 52, 54 of each layer of fibers 502, 504, 506, 508 can thus be located symmetrically with respect to the plane P.

[0117] This second draping method is illustrated in a non-limiting way in Figures 8 and 9, in which the circumferential extents a502, a504, a506, a508, as predetermined dimensions of the fiber layers 502, 504, 506, 508, are different.

[0118] The draping in step (a) can form a single fibrous blank T50, T50a, T50b. Alternatively, the draping in step (a) can form several fibrous blanks T50, T50a, T50b which are configured to be arranged circumferentially next to each other and around the first axis X5 in a step (b) described below.

[0119] The process then includes a step (b) of shaping at least one fibrous blank T50, T50a, T50b obtained in step (a), on a conical or frustoconical surface of a shaping tool 7, so that the circumferential ends 52, 54 of at least one fibrous blank T50 overlap each other by complementary shape.

[0120] The forming tool 7 can be a mold having a conical or frustoconical shape. This conical or frustoconical surface allows the conical or frustoconical portion of the fibrous preform 50 to be formed. The conical or frustoconical surface used in step (b) can be an external surface 72 of the forming tool 7 ([Fig. 10]). In other words, the forming tool 7 can be a male-type mold in this configuration.

[0121] Alternatively, the conical or frustoconical surface used in step (b) can be an internal surface 74 of the forming tool 7 ([Fig. 11]). In other words, the forming tool 7 can be a female-type mold in this configuration variant.

[0122] In step (b) and according to a first shaping method, at least one fibrous blank T50, T50a, T50b, formed for example in step (a) according to the first draping method ([Fig.7]) or the second draping method (figures 8 and 9), can be arranged on the conical or frustoconical surface of the shaping tool 7 so that the circumferential ends 52, 54 are aligned next to each other around the first axis X5 and preferably by complementary shape.

[0123] With reference to [Fig. 12], the shaping of a single fibrous blank T50, T50a, T5ob obtained by the second draping method (figures 8 and 9), can substantially align the straight edges (502c, 502d; 504c, 504d, 506c, 506d; 508c, 508d) of the circumferential ends 52, 54 with each other.

[0124] In step (b) and according to a second shaping method ([Fig. 13]), at least one first fibrous blank T50a among the several fibrous blanks T50, T50a, T50b formed in particular in step (a) according to the second draping method (figures 8 and 9), can be arranged in the opposite direction with respect to at least one second fibrous blank T50b of the several fibrous blanks T50, T50a, T50b, so that the circumferential ends 52, 54 of the first T50a and second T50b fibrous blanks overlap each other by complementarity of shape.

[0125] The process according to the invention may further include a step (c) of compacting the circumferential ends 52, 54 together. This step (c) may be carried out before or after step (b). The compaction reduces the space between the straight edges 502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d of the circumferential ends 52, 54, before, in particular, consolidating the fibrous preform 50 by densification to form the final part 5 in composite material.

[0126] Advantageously, step (c) can be carried out on the circumferential ends 52, 54 connected together by step (b) of the first shaping method ([Fig. 12]). This allows for better assembly and interlocking of the circumferential ends 52, 54 and substantially forms the overlap by complementary shape.

[0127] As illustrated by way of example in Figures 14 to 16, the process may further include a step (i) of reinforcing at least a part of the fibrous preform 50 by adding filaments or fibers 510 through the fiber layers 502, 504, 506, 508.

[0128] Step (i) can be carried out after step (a) or after step (b). In other words, the filaments or fibers 510 can be integrated directly either onto the fibrous blank T50, T50a, T50b before step (b), or onto the fibrous preform 50 obtained after step (b).

[0129] Step (i) can be carried out at least at the circumferential ends 52, 54 of at least one fibrous blank T50, T50a, T50b.

[0130] Step (i) can be performed on at least part 51 of the fibrous preform 50, which may correspond to an upper part of the composite material component 5 intended, in particular, to be installed under an aircraft wing. Step (i) can be performed on the entire fibrous preform 50.

[0131] Step (i) can be carried out by needle punching ([Fig. 16]) or by tufting ([Fig. 15]).

[0132] With reference to [Fig. 15], the filaments or fibers 510 can be inserted through the fiber layers 502, 504, 506, 508 by means of a suitable needle 8. The filaments or fibers 510 can be inserted along a Z-axis, as illustrated, without limitation, in [Fig. 15].

[0133] With reference to [Fig. 16], one or more barbed needles 9, i.e., needles having asperities or hooks, can radially pierce the fiber layers 502, 504, 506, 508, so as to carry away a portion of the fibers originally extending in the plane of a fiber layer, in a direction orthogonal to that plane, so that these carried-away fiber portions pass through the different fiber layers. The barbed needle 9 can pierce the fiber layers along the Z-axis, as illustrated, without limitation, in [Fig. 16].

[0134] The process according to the invention may further include a densification step (d) by impregnating the fibrous preform 5, in particular obtained at the end of step (b) or step (c), with the matrix precursor. This precursor may be pre-impregnated in the fiber layers 502, 504, 506, 508 or injected in step (d). This densification step consolidates the fibrous preform 50 obtained by the manufacturing process of the invention and forms the composite material part 5, particularly for the aircraft turbomachine 10.

Claims

1. Demands A method for manufacturing a fibrous preform (50) for producing a part (5) made of composite material, in particular for an aircraft turbomachine (10), this fibrous preform (50) comprising at least one conical or frustoconical portion, and extending around a longitudinal axis (X5), the fibrous preform (50) comprising in thickness a stacking of several layers of fibers (502, 504, 506, 508), the method being characterized in that it comprises: - a step (a) of flat draping the layers of fibers (502, 504, 506, 508) on a draping tool (6) to form at least one flat fiber blank (T50, T50a, T50b), the layers of fibers (502, 504, 506, 508) each having an angular sector shape comprising at least one curved edge (502a, 504a, 506a, 508a; 502b, 504b, 506b, 508b) and two straight edges (502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d) joined together by said curved edge, the fiber layers (502, 504, 506, 508) having predetermined dimensions such that each fiber layer (502, 504, 506, 508) draped over a previously draped fiber layer (502, 504, 506, 508) has straight edges (502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d) that are set back from the straight edges (502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d) of the previously draped fiber layer, so that said at least one fiber blank (T50, T50a, T50b) has two ends circumferential (52, 54) each having a stepped shape and therefore steps are formed by the straight edges (502c, 502d; 504c, 504d; 506c, 506d; 508c, 508d) of the fiber layers (502, 504, 506, 508), and - a step (b) of shaping said at least one fibrous blank (T50, T50a, T50b) on a conical or frustoconical surface of a shaping tool (7), so that the circumferential ends (52, 54) of said at least one fibrous blank (T50, T50a, T50b) overlap each other by complementary shape.

2. A manufacturing method according to claim 1, characterized in that the draping of step (a) forms a single fibrous blank (T50, T50a, T5ob) or several fibrous blanks (T50, T50a, T50b) which are arranged circumferentially next to each other around the axis (X5) in step (b).

3. A manufacturing method according to claim 1 or 2, characterized in that in step (a), the fiber layers (502, 504, 506, 508) are draped flat with identical predetermined dimensions (a502, a504, a506, a508) and are circumferentially offset from one another, such that: - at one of the two circumferential ends (52), the straight edges (504c, 506c, 508c) of each fiber layer (504, 506, 508) draped over the previously draped fiber layer (502, 506, 508) are set back from the straight edges (502c, 506c, 508c) of this previously draped fiber layer, and - at the other of the two ends circumferential (54), the straight edges (504d, 506d, 508d) of each layer of fibers (504, 506, 508) draped over the layer of fibers (502, 506, 508) previously draped extend beyond the straight edges (502d, 506d, 508d) of this previously draped layer of fibers.

4. A manufacturing method according to any one of claims 1 to 3, characterized in that in step (a), the layers of fibers (502, 504, 506, 508) are draped flat with predetermined dimensions (a502, a504, a506, a508) different and centered with respect to each other along the same axis (P) of symmetry.

5. A manufacturing method according to claim 4 in combination with claim 3, characterized in that in step (b), at least one first fibrous blank (T50a) among said several fibrous blanks (T50, T50a, T50b) is arranged in the opposite direction to at least one second fibrous blank (T50b) of said several fibrous blanks (T50, T50a, T50b), so that the circumferential ends (52, 54) of said first (T50a) and second (T50b) fibrous blanks overlap each other by complementarity of shape.

6. A manufacturing method according to any one of claims 1 to 5, characterized in that it further comprises a step (c) of compacting the circumferential ends (52, 54) together.

7. A manufacturing method according to any one of claims 1 to 6, characterized in that each of the fiber layers (502, 504, 506, 508) comprises unidirectional fibers oriented in directions different from the unidirectional fibers of the other fiber layers (502, 504, 506, 508), step (a) being carried out by draping the fiber layers (502, 504, 506, 508) along directions different from the unidirectional fibers of the other fiber layers (502, 504, 506, 508).

8. A manufacturing method according to any one of claims 1 to 7, characterized in that the conical or frustoconical surface used in step (b) is an external surface (72) of the forming tooling (7).

9. A manufacturing method according to any one of claims 1 to 8, characterized in that the conical or frustoconical surface used in step (b) is an internal surface (74) of the forming tooling (7).

10. A manufacturing method according to any one of claims 1 to 9, characterized in that it further comprises a step (i) of reinforcing at least a part of the fibrous preform (50) by adding filaments or fibers (510) through the layers of fibers (502, 504, 506, 508), this step (i) being carried out after step (a) or after step (b).

11. A manufacturing method according to claim 10, characterized in that step (i) is carried out at least at the circumferential ends (52, 54) of said at least one fibrous blank (T90).

12. A manufacturing process according to any one of claims 1 to 11, characterized in that the fibre layers (502, 504, 506, 508) are pre-impregnated with a matrix precursor.

13. A manufacturing method according to any one of claims 1 to 12, characterized in that the draping of step (a) is carried out automatically, for example by automatic fiber placement (AFP) or by automatic fiber layer placement (ATL).

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