FIBROUS STRUCTURE FOR THE PRODUCTION OF A PART IN COMPOSITE MATERIAL

Abstract

The present invention relates to a fibrous structure (900) for making a part (90) of composite material, the fibrous structure (900) comprising a stack of several layers of fibers (910, 912, 914), and a reinforcing element (920) situated between a lower layer (912) and an upper layer (914), wherein the reinforcing element (920) comprises: - a support (922) interposed between the lower (912) and upper (914) layers and having a lower face (922a) covered by the lower layer (912), and an upper face (922b) covered by the upper layer (914), and - strands (924) projecting from the lower (922a) and upper (922b) faces of the support (922) and engaged respectively in the lower (912) and upper (914) layers. Figure for the abstract: Fig. 4

Description

Title of the invention: FIBER STRUCTURE FOR THE PRODUCTION OF A PART IN 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 fibrous structure for manufacturing such composite parts. The invention also relates to a composite part comprising such a fibrous structure and a method for manufacturing this fibrous structure for producing the composite part. 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 forming a fibrous structure. The fibrous reinforcement can be produced by three-dimensional (3D) weaving or by stacking (or draping) and superimposing several layers / plies (multilayer). The matrix can be obtained by transforming a resin (or, in other words, a matrix precursor), for example, by heat treatment. The resin can be injected into a fibrous preform (corresponding to the fibrous reinforcement without matrix densification), or the fibrous preform can be pre-impregnated with the resin (also referred to as "prepreg").

[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 (in particular, a ceramic matrix composite, CMC). The manufacture of such a turbomachine component generally begins by draping a succession of layers of fibers (such as aluminum oxide fibers) over a shaped or flat mold to create the fibrous preform, which has a layered shape. The manufacturing process continues with the densification of this fibrous preform by the matrix (for example, composed mainly of aluminum oxide). This involves impregnating the preform with the matrix precursor and consolidating the matrix to obtain the fibrous structure of the final component.

[0005] However, in the case of a fibrous structure obtained by draping (or in other words by stacking or layering), this fibrous structure may present A weakness exists at the interface between successive and adjacent fiber layers. Indeed, at the interfaces between the layers of the fibrous structure, the material's cohesion is ensured solely by the matrix, without reinforcement or a transverse cohesive structure. This interface between successive and adjacent layers can be subject to damage, particularly in the event of thermal shock or impacts from a foreign body. These interface zones can therefore be conducive to the appearance and propagation of cracks within the layers of the part's fibrous structure.

[0006] By way of example, [Fig.1] schematically illustrates a cross-sectional view of a fibrous structure 900 comprising a stack of several layers of fibers 910. During a shock or impact represented by an arrow F, cracks Z can form in particular in the matrix within or between the layers 910 of the fibrous structure 900 of the part 90.

[0007] There is, therefore, a need to strengthen the interlaminar mechanical strength of a fibrous structure for the production of a part in composite material, in particular for an aircraft turbomachine. Summary of the invention

[0008] The present invention proposes a simple, effective and economical solution to the aforementioned disadvantages of the prior art.

[0009] To this end, the invention proposes a fibrous structure for the production of a part in composite material, in particular for an aircraft turbomachine, the fibrous structure comprising a stacking of several layers of fibers, and at least one reinforcing element located between at least one lower layer of fibers and at least one upper layer of fibers.

[0010] According to the invention, said at least one reinforcing element comprises: - a layer-shaped support, which is interposed between the lower and upper fiber layers, this support having a lower face covered by said at least one lower fiber layer, and an upper face covered by said at least one upper fiber layer, and - protruding strands on the lower and upper faces of the support and engaged respectively in the lower and upper fiber layers.

[0011] Thus, this solution makes it possible to achieve the aforementioned objective. In general, the fibrous structure according to the invention makes it possible to significantly increase the out-of-plane mechanical strength of the composite material part, and in particular its resistance to thermal shock and impacts from foreign bodies. To this end, the reinforcing element of the fibrous structure comprises both a support and strands projecting from this support. The support provides a solid base for connecting the lower and upper layers. The strands are engaged, in particular, along Radial and transverse directions, relative to the stacking direction of the fiber layers, are incorporated in the lower and upper layers to significantly strengthen the bond between them. With the cohesion of the fiber layers at the interface reinforced, the fibrous structure is no longer susceptible to the formation and propagation of cracks within the layers. Consequently, a composite material incorporating such a fibrous structure (particularly as a fiber reinforcement densified by the matrix) effectively withstands stress and offers an optimized lifespan.

[0012] The term "fibrous structure" means a structure comprising layers of fibers which are in particular densified (or in other words impregnated or embedded) by a matrix.

[0013] The term “fibrous preform” means a fibrous reinforcement also comprising layers of fibers which are intended to be densified by the matrix.

[0014] The term “support” for a reinforcing element means a support made of fibers and which is in particular formed of fibers.

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

[0016] - the support is chosen from a fiber ply, a fiber ribbon, fiber strands and fiber threads;

[0017] - the support is at least partially coated with a binder, for example a fugitive binder, or of a matrix, for example ceramic;

[0018] - each of the strands and the support comprises ceramic fibers, for example based of alumina;

[0019] - each of the strands comprises oxide fibers coated with a matrix, for example made of sintered ceramic;

[0020] - the strands each have a cross-sectional diameter of less than 2 mm, for example this diameter is between 0.1 and 1 mm;

[0021] - the strands each have a maximum height of 2 mm relative to the face corresponding, for example this height is between 0.2 and 1 mm;

[0022] - the average linear density of the strands is equal to at least one strand over a distance between 1 and 3 mm along the support.

[0023] The invention also relates to a part made of composite material, in particular for an aircraft turbomachine, comprising a fibrous structure according to one of the features of the invention, the part being for example a housing or a turbomachine nozzle.

[0024] The invention also relates to an aircraft turbomachine comprising at least one part made of composite material according to the invention.

[0025] The invention further relates to a method for manufacturing a fibrous structure according to one of the features of the invention, for producing a part made of composite material, the method comprising the steps of: (a) to achieve the stacking of several layers of fibre by draping, and (b) insert at least one reinforcing element between at least one lower fibre layer and at least one upper fibre layer to form said fibrous structure.

[0026] According to the invention, step (b) is carried out by interposing the support between the lower and upper fiber layers, and by engaging the strands in said lower and upper fiber layers.

[0027] Step (b) may include at least one or more substep(s) (b2) of compacting the lower fiber layer and / or the upper fiber layer with the strands by means of, for example, a mechanical roller or a pressure membrane.

[0028] Preferably, step (b) may comprise two substeps (b2) of compacting the lower and upper fiber layers with the strands. In this configuration, a first compaction may be carried out on the lower fiber layer, and then a second compaction may be carried out on the upper fiber layer.

[0029] The pressurization at substep (b2) can be achieved by overpressure or by vacuum. Brief description of the figures

[0030] 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:

[0031] [Fig. 1] is a schematic axial cross-sectional view of a fibrous structure with cracks according to the prior art,

[0032] [Fig.2] 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,

[0033] [Fig. 3] is a schematic perspective view representing an example of a composite material part of [Fig. 2], which is an exhaust nozzle of the turbomachine,

[0034] [Fig. 4] is a schematic axial cross-sectional view representing a first example of a fibrous structure of the composite material part of [Fig. 1] or 2,

[0035] [Fig.5] is a schematic axial cross-sectional view representing a reinforcing element of the fibrous structure of [Fig.4],

[0036] [Fig.6] is a schematic perspective view representing a first example of the reinforcement element of [Fig.5],

[0037] [Fig.7] is a schematic perspective view representing a second example of the reinforcement element of [Fig.5],

[0038] [Fig.8] is a schematic perspective view representing a third example of the reinforcement element of [Fig.5],

[0039] [Fig.9] is a schematic axial cross-sectional view representing a second example of a fibrous structure of the composite material part of [Fig.1] or 2,

[0040] [Fig. 10] is a schematic axial cross-sectional view representing a third example of a fibrous structure of the composite material part of [Fig. 1] or 2,

[0041] [Fig. 1 1] is a block diagram of the steps in a manufacturing process for the fibrous structure of Figures 4, 9 and 10,

[0042] [Fig. 12] schematically represents in axial section an example of a manufacturing process for [Fig. 11].

[0043] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0044] 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 an 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 the longitudinal 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.

[0045] Fig. 1 has been described in the technical background of this application and illustrates a cross-sectional view of a prior art fibrous structure 900 which has Z cracks in the fiber layers 910.

[0046] The invention can be applied generally to any part 90 made of composite material, in particular for an aircraft turbomachine 1.

[0047] The aircraft turbomachine 1 can be a turbojet, a turboprop or a turbomotor.

[0048] Fig. 2 illustrates an example of an aircraft turbomachine 1 extending along a longitudinal X axis.

[0049] The turbomachine 1 may comprise, from upstream to downstream, a fan 2 (or in other words a propeller), at least one compressor (such as a low-pressure compressor 3 and a high-pressure compressor 4), a combustion chamber 5, at least one turbine (such as a high-pressure turbine 6 and a low-pressure turbine 7), and possibly a gas exhaust nozzle 8.

[0050] With reference to [Fig.2], the blower 2 can be surrounded by a housing 20 called a blower housing, and the low-pressure compressor 3 can also be surrounded by an intermediate housing 30. These blower housings 20 and intermediate housing 30 can extend around the X axis.

[0051] Figure 3 illustrates, by way of example, the nozzle 8 comprising a plug 80 (or, in other words, an external shield). The nozzle 8 can be a part of revolution extending around the X-axis.

[0052] The fan housing 20, the intermediate housing 30 and / or the nozzle 8 can be made of composite material. Thus, at least one of these parts of the turbomachine 1 can constitute, without limitation, the composite material part 90 of the invention.

[0053] The composite material part 90 may include a first matrix, such as a ceramic matrix (CMC, acronym for Ceramic Matrix Composite) or an organic matrix (CMO, acronym for Organic Matrix Composite). This first matrix may form the so-called final matrix of the fibrous structure 900. The term "final matrix" refers to the matrix that permanently binds the fibers of the fibrous structure 900.

[0054] Advantageously, the first die of part 90 is made of CMC ceramic.

[0055] Part 90 may include a fibrous structure 900.

[0056] The fibrous structure 900 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. Advantageously, the fibrous structure 900 may comprise predominantly ceramic fibers. By "predominantly," it is understood that the weight proportion of ceramic fibers is greater (for example, greater than 50% by weight) than the weight proportion of the remaining components of the fibrous structure (such as the other fibers and / or the resin of the fibrous structure).

[0057] The fibrous structure 900 comprises a stack of several layers of fibers 910, 912, 914. As mentioned above, the layers of fibers 910, 912, 914 can be densified (or otherwise said impregnated or embedded) by a first matrix (such as CMC ceramic).

[0058] With reference to figures 4, 9 and 10, the stacking of the fiber layers 910 can be carried out along a stacking axis A.

[0059] The stacking of fiber layers 910 may comprise at least two layers of fibers 910, such as at least one bottom layer of fibers 912 (hereinafter layer lower 912) and at least one upper fiber layer 914 (hereinafter upper layer 914) which are superimposed one on top of the other.

[0060] The stacking of fiber layers 910 may include more than two layers of fiber 910. In particular, the lower layer 912 may be located on one or more layers of fiber 910, and / or one or more layers of fiber 910 may be located on the upper layer 914 ([Fig.10]).

[0061] Each layer of fibers 910, 912, 914 may comprise ceramic fibers, carbon fibers, glass fibers, polyamide fibers, aramid fibers, or a mixture of at least two of these fibers. Preferably, each layer of fibers 910, 912, 914 may comprise ceramic fibers, such as oxide fibers. For example, the ceramic fibers may be based on aluminum oxide, or alumina (Al₂O₃). Even more preferably, each layer of fibers 910, 912, 914 may comprise predominantly ceramic fibers, such as alumina fibers. "Predominantly" means a higher proportion by weight of ceramic fibers (for example, greater than 50% by weight) than the proportion by weight of the remaining components of the corresponding fiber layer 910 (such as fibers and / or resin of that layer).

[0062] Each layer of fibers 910, 912, 914 may have a first thickness E9i0 measured, in particular, along a plane parallel to the stacking axis A. This first thickness E9i0 may be less than 1 mm. The first thickness E9i0 may be less than 0.5 mm. Preferably, particularly for parts 90 whose total thickness is small and less than 5 mm, or even less than 1.5 mm, the first thickness E9iq may be between 0.05 and 0.3 mm.

[0063] The fibrous structure 900 includes at least one reinforcing element 920 located between at least one lower fiber layer 912 and at least one upper fiber layer 914.

[0064] Advantageously, the fibrous structure 900 can include several reinforcing elements 920 each located between two adjacent layers of fibers 910 forming the lower layer 912 and upper layer 914 ([Fig.12]).

[0065] Even more advantageously, the fibrous structure 900 may include at least one reinforcing element 920 between each layer of fibers 910 of the fibrous structure (in other words, the upper layer 914 of one reinforcing element 920 may be the lower layer 912 of another subsequent reinforcing element 920). In this configuration, strands 924 (described below) of one of the reinforcing elements 920 may interweave within at least one intermediate fiber layer with strands 924 of the other subsequent reinforcing element 920.

[0066] According to one of the features of the invention, the reinforcing element 920 comprises a support 922.

[0067] The support 922 is in the form of a layer. Preferably, the support 922 can have an elongated shape along a longitudinal axis B which is substantially perpendicular to the stacking axis A.

[0068] The support 922 is intercalated between the lower 912 and upper 914 layers, particularly when the stack comprises at least two layers of fibers 910. The support 922 has a lower face 922a covered by the lower layer 912, and an upper face 922b covered by the upper layer 914.

[0069] The support 922 can be chosen from a fiber ply ([Fig.6]), a fiber ribbon ([Fig.7]), one or more fiber strands, and one or more fiber yarns ([Fig.8]).

[0070] In the case of the support 922 in the form of folds or ribbon, this support 922 may include a single fold or ribbon between the lower 912 and upper 914 layers, so as to form the lower 922a and upper 922b faces covering, respectively, the lower 912 and upper 914 layers.

[0071] In the case of the support 922 in the form of a wick or wire, this support 922 may comprise several wicks or wires arranged successively between the lower 912 and upper 914 layers (in particular along the axis B), so as to form the lower 922a and upper 922b faces covering, respectively, the lower 912 and upper 914 layers.

[0072] The support 922 may have a length L922 measured in particular along the axis B. This length L922 may be substantially equal to that of the lower layer 912 and upper layer 914.

[0073] The support 922 may have a width 1922, measured in particular along a plane transverse to axis B. This width 1922 may be between 1 mm and 30 cm, particularly in the case of the support 922 in the form of a ribbon. Preferably, the width 1922 may be at least 5 mm. Even more preferably, the width 1922 may be between 5 mm and 100 cm.

[0074] The support 922 may have a second thickness E922 measured, in particular, along a plane parallel to axis A. This second thickness E922 may be equal to, less than, or greater than the first thickness E910. The second thickness E922 may be less than 1 mm. Preferably, the second thickness E922 may be between 0.02 mm and 0.5 mm, particularly in the case of the support 922 in the form of folds and / or ribbon.

[0075] The support 922, particularly in the form of a wick and / or wire, may have a first diameter D922. This first diameter D922 may be less than 3 mm. Preferably, the first diameter D922 may be between 0.05 and 3 mm. Preferably between 0.05 and 1 mm. Preferably between 0.08 and 0.3 mm. When the support 922 is in the form of a strand with the first diameter D922 of approximately 3 mm, the second thickness E922 of this strand may be greater than the first thickness E910 of one of the fiber layers 910, 912, 914.

[0076] The dimensions (i.e. length L922, width 1922, second thickness E922, first diameter D922) and / or the shapes (i.e. folds, ribbon, strand(s), thread(s)) of the support(s) 922 may vary according to the layers of fibers 910 and / or the dimensions desired to produce the final part 90.

[0077] The support 922 may comprise ceramic fibers, for example alumina-based (Al12O3). According to one embodiment, the support 922 may comprise carbon fibers, glass fibers, polyamide fibers, aramid fibers, or a mixture of at least two of these fibers.

[0078] The support 922 may be at least partially coated with a first binder or a second matrix. The first binder may be a fugitive binder. This fugitive binder may be removed (for example, by evaporation) or melted into or replaced by the first matrix, which forms the final matrix of the fibrous structure 900. The second matrix may be ceramic. Preferably, the support 922 may be entirely coated with this second matrix. By way of example, the second matrix may be ceramic, such as alumina-based. According to another embodiment, the second matrix may be organic, such as epoxy.

[0079] The reinforcing element 920 also includes strands 924 (or in other words, pins) projecting on the lower 922a and upper 922b faces of the support 922.

[0080] With reference to figures 5 to 8, the strands 924 can extend radially and / or transversely (with respect to axis B) from the support 922.

[0081] These strands 924 are engaged respectively in the lower layer 912 and upper layer 914.

[0082] With reference to Figures 4, 9 and 10, the strands 924 can be engaged in at least one of the fiber layers 910, i.e. the lower layer 912 or the upper layer 914. In particular, the strands 924 can be engaged through these fiber layers and preferably between the fibers of the corresponding fiber layer.

[0083] Advantageously, the strands 924 can be engaged in at least two layers of fibers 910, in particular when the fibrous structure 900 comprises one or more layers of fibers 910 below the lower layer 912 and / or one or more layers of fibers 910 above the upper layer 914. In other words, each of the strands 924 can be engaged through at least two (or more than two) layers of fibers 910.

[0084] The strands 924 and the support 922 can be monobloc (i.e. made from material).

[0085] The strands 924 may each have a second diameter D924 in cross-section that is less than 2 mm. For example, this second diameter D924 may be between 0.1 and 1 mm.

[0086] The strands 924 can each have a maximum height H924 of 2 mm relative to the corresponding face 822a, 822b. For example, this height H924 can be between 0.1 and 1 mm.

[0087] The strands 924 can be distributed regularly along the support 922.

[0088] The average linear density of the 924 strands can be equal to at least one 924 strand on a distance of between 1 and 10 mm along the support 922.

[0089] The dimensions (i.e. the second diameter D922, height H924, linear density) of each strand 924 can vary according to the layers of fibers 910 and / or the dimensions desired to produce the final part 90.

[0090] Each of the strands 924 can be a monofilament or a fiber or a set of fibers. The fiber or set of fibers can then be a set of filaments.

[0091] Each of the strands 924 may comprise ceramic fibers, for example alumina-based. According to one embodiment, each strand 924 may comprise carbon fibers, glass fibers, polyamide fibers, aramid fibers, or a mixture of at least two of these fibers.

[0092] Each of the strands 924 may comprise oxide fibers coated with a third matrix, for example made of sintered ceramic. This third ceramic matrix may be alumina-based. According to another embodiment, the third matrix may be organic, such as epoxy.

[0093] Each of the strands 924 can be stiffened by a second binder (or otherwise called "binder" in English) or any other element allowing the strands 924 to be stiffened and in particular by binding the fibers or filaments which constitute it. The second binder can then be fugitive organic, that is to say, one which can be eliminated to be replaced by the ad hoc matrix of the composite, for example during a consolidation phase of the fibrous structure 900.

[0094] The present application will now describe the different possible configurations of the fibrous structure 900 according to the invention, in particular with reference to Figures 4 to 10.

[0095] Figures 4 to 8 illustrate a first example of the fibrous structure 900.

[0096] The fibrous structure 900 according to the first example comprises a stack of two layers of fibers 910 (in particular matrix densified), respectively, the lower layer 912 and the upper layer 914. The reinforcing element 920 is between the lower layer 912 and the upper layer 914. As described above, the support 922 is intercalated between these lower 912 and upper 914 layers, and the strands 924 are engaged respectively in the lower 912 and upper 914 layers.

[0097] With reference to [Fig.6], the support 922 can be a fiber ply.

[0098] With reference to [Fig.7], the support 922 can be a fibre ribbon.

[0099] With reference to [Fig.8], the support 922 can be a fiber wire.

[0100] The support 922 in the form of folds, ribbon or wire may have at least one of the characteristics described above with reference to the 922 fiber support and the 924 strands.

[0101] Fig. 9 illustrates a second example of the fibrous structure 900.

[0102] This second example of a fibrous structure 900 differs from the fibrous structure 900 of the first example by the support 922. Indeed, the support 922 is in the form of fiber strands. Thus, several fiber strands form the support 922 intercalated between the lower layer 912 and the upper layer 914.

[0103] Fig. 10 illustrates a third example of the fibrous structure 900.

[0104] This third example of fibrous structure 900 differs from the fibrous structure 900 of the first and second examples by the layers of fibers 910.

[0105] The fibrous structure 900 of the third example comprises a stack of more than two layers of fibers 910 (in particular, matrix-densified). Specifically, the lower layer 912 is superimposed on a layer of fibers 910, and another layer of fibers 910 is superimposed on the upper layer 914. In this configuration, the reinforcing element 920 is intercalated between the lower layer 912 and the upper layer 914, each of which is covered by an additional layer of fibers 910. This increases the cohesion in the core (or, in other words, in a central portion) of the fiber layers 910.

[0106] The present application will now describe a method for manufacturing the fibrous structure 900, as described above with reference to Figures 4 to 10.

[0107] Fig. 10 summarizes the successive steps of the process, with optional steps represented by dotted lines.

[0108] According to the invention, the method comprises the steps of: (a) carrying out the stacking of several layers of fibers 910, 912, 914 by draping, and (b) inserting at least one reinforcing element 920 between at least one lower layer 912 and at least one upper layer 914 to form the fibrous structure 900.

[0109] Step (a) can be carried out manually or automatically, for example by a suitable machine. The draping can be carried out automatically, for example according to the AFP technique (English acronym for "Automated Fibre Laying" for automated fibre laying), the ATL technique (English acronym for "Automated Tape Laying" for automated tape laying) or the P&P technique (English acronym for "Pick&Place" for a picking and positioning system).

[0110] Step (b) is carried out by inserting the support 922 between the lower 912 and upper 914 layers, and by engaging the strands 924 respectively in the lower 912 and upper 914 layers.

[0111] In particular, step (b) may include at least one substep (bi) deposition of the support 922 between the lower 912 and upper 914 layers.

[0112] Step (b) may include at least one or more substep(s) (b2) compaction of the lower layer 912 and / or the upper layer 914 in particular with the reinforcing element 920 by means of, for example, a roller or a pressure membrane.

[0113] Substep (b2) allows for the application of additional mechanical force to reinforce the engagement of the strands 924 in the fiber layers 910, 912, 914. Furthermore, this substep (b2) allows for the consolidation of the fibrous structure 900.

[0114] Preferably, step (b) may include two substeps (b2) of compacting the lower 912 and upper 914 fiber layers of the reinforcing element 920. In this configuration, a first compaction can be carried out on the lower 912 fiber layer, then a second compaction can be carried out on the upper 914 fiber layer.

[0115] Advantageously, substep (b2) can be carried out on the lower layer 912 and / or the upper layer 914 with the support 920 and / or the strands 924.

[0116] The pressurization at substep (b2) can be achieved by overpressure or by vacuum.

[0117] Figure 12 illustrates an example of the manufacturing process according to the invention. In this example, the fibrous structure 900 is formed by first draping at least two layers of fibers 910, respectively the first and second layers. This second layer corresponds to a first lower layer 912 on which a first reinforcing element 920 is deposited. Then, two further layers of fibers 910, respectively the third and fourth layers, are draped over this first reinforcing element 920. This is carried out in such a way that the strands 924 of the first reinforcing element 920 are engaged respectively in the first lower layer 912 (i.e., the second layer) and a first upper layer 914 corresponding to the third layer stacked on the first reinforcing element 920.Optionally, an initial compaction of the assembly can be carried out to reinforce the engagement of the strands through the first lower 912 and upper 914 layers. Then, a second reinforcing element 920 is deposited on the fourth layer which corresponds to a second lower 912 layer on which a second reinforcing element 920 is deposited. Finally, two other layers of fibers 910, respectively fifth and sixth layers, are stacked on this second element. reinforcement 920 is draped. This is also done in such a way that the strands 924 of the second reinforcement element 920 are engaged respectively in the second lower layer 912 (i.e., fourth layer) and a second upper layer 914 corresponding to the fifth layer stacked on the second reinforcement element 920. Optionally, a second compaction of the assembly can be carried out to reinforce the engagement of the strands 924 through the first and second lower layers 912 and upper layers 914.

Claims

Demands

1. A fibrous structure (900) for making a part (90) of composite material, in particular for an aircraft turbomachine (1), the fibrous structure (900) comprising a stack of several layers of fibers (910, 912, 914), and at least one reinforcing element (920) located between at least one lower layer of fibers (912) and at least one upper layer of fibers (914), characterized in that said at least one reinforcing element (920) comprises: - a layer-shaped support (922), which is intercalated between the lower (912) and upper (914) fiber layers, this support (922) having a lower face (922a) covered by said at least one lower layer of fibers (912), and an upper face (922b) covered by said at least one upper layer of fibers (914),and - strands (924) projecting from the lower (922a) and upper (922b) faces of the support (922) and engaged respectively in the lower (912) and upper (914) fiber layers.

2. Fibrous structure according to claim 1, characterized in that the support (922) is selected from a fiber ply, a fiber ribbon, fiber strands and fiber yarns.

3. Fibrous structure according to claim 1 or 2, characterized in that the support (922) is at least partly coated with a binder, for example a fugitive binder, or with a matrix, for example ceramic.

4. Fibrous structure according to any one of the preceding claims, characterized in that each of the strands (924) and the support (922) comprises ceramic fibers, for example based on alumina.

5. Fibrous structure according to any one of the preceding claims, characterized in that each of the strands (924) comprises oxide fibers coated with a matrix, for example made of ceramic, sintered.

6. Fibrous structure according to any one of the preceding claims, characterized in that the strands (924) each have a cross-sectional diameter (D924) of less than 2 mm, for example this diameter (D924) is between 0.1 and 1 mm.

7. Fibrous structure according to any one of the preceding claims, characterized in that the strands (924) each have a maximum height (H924) of 2 mm relative to the corresponding face (922a, 922b), for example this height (H924) is between 0.2 and 1 mm.

8. Fibrous structure according to any one of the preceding claims, characterized in that the average linear density of the strands (824) is equal to at least one strand (924) over a distance of between 1 and 3 mm along the support (922).

9. Part (90) of composite material, in particular for an aircraft turbomachine (1), comprising a fibrous structure (900) according to any one of the preceding claims, the part (90) being for example a housing (20, 30) or a nozzle (8) of a turbomachine.

10. Aircraft turbomachine (1) comprising at least one part (90) made of composite material according to claim 9.

11. A method for manufacturing a fibrous structure (900) according to any one of claims 1 to 8, for producing a part (90) made of composite material, the method comprising the steps of: (a) carrying out the stacking of several layers of fibers (910, 912, 914) by draping, and (b) inserting at least one reinforcing element (920) between at least one lower layer of fibers (912) and at least one upper layer of fibers (914) to form said fibrous structure (900), characterized in that step (b) is carried out by interposing the support (922) between the lower (912) and upper (914) fiber layers and by engaging the strands (924) in said lower (912) and upper (914) fiber layers.

12. A manufacturing method according to claim 11, characterized in that step (b) comprises at least one or more substep(s) (b2) of compacting the lower fiber layer (912) and / or the upper fiber layer (914) with the strands (924) by means of, for example, a roller or a pressure membrane.

Images