FIBROUS PREFORM OF A BLADE MADE OF COMPOSITE MATERIAL COMPRISING A SERRATION ELEMENT AND METHOD FOR MANUFACTURING SUCH A BLADE

Abstract

The invention relates to a fiber preform (700) of a blade for a turbomachine, in particular an aircraft, having a blade and a root, the blade comprising serration elements (8) on a leading edge and / or a trailing edge of the blade, the fiber preform (700) being obtained by weaving fibers and which is embedded in a polymer matrix, the fiber preform (700) comprising a first part intended to extend into the blade and a second part intended to extend into the root, characterized in that said fiber preform (700) comprises a corrugated or toothed edge (702) which is intended to extend into said serration elements (8). Figure for abstract: Figure 7

Description

Title of the invention: FIBROUS PREFORM OF A BLADE MADE OF COMPOSITE MATERIAL COMPRISING A SERRATION ELEMENT AND METHOD FOR MANUFACTURING SUCH A BLADE DAWN Technical field

[0001] The invention relates to the field of turbomachines, in particular aircraft turbomachines, and in particular to the propulsion propellers of these turbomachines which comprise blades. In particular, the invention relates to blades made of composite material for such turbomachines. More specifically, the invention relates to a fiber preform for such blades comprising a serration element, as well as a method for manufacturing such blades. Technical background

[0002] An aircraft turbomachine conventionally comprises a gas generator which drives at least one propeller. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the rotor of the propeller for its rotational drive.

[0003] A propeller can be shrouded. This is the case for a fan in a turbomachine of the turbojet or turbofan type for example.

[0004] A propeller can be unducted. This is the case for a turboprop or an “open-rotor” type architecture, for example.

[0005] A propeller comprises an annular row of blades rotating about a longitudinal axis of the turbomachine. Each blade comprises a blade connected to a root. The blade comprises a lower surface and an upper surface connected to each other by a leading edge and a trailing edge.

[0006] It is known to produce turbomachine blades, such as blades of a fan or a turbomachine rectifier, from composite material to reduce the mass while having good mechanical properties. For example, the blades from composite material are produced by injecting a resin, for example by injection molding of a liquid resin (RTM, acronym for the English expression "Resin Transfer Molding") into a fiber preform.

[0007] The search for minimizing polluting emissions linked to air transport involves in particular the improvement of all the efficiencies of propulsion systems (or in other words of turbomachines), and more particularly of propulsive efficiency which characterizes the efficiency with which the energy communicated to the air passing through the engine is converted into useful thrust.

[0008] The elements influencing this propulsive efficiency to the first order are those linked to the low pressure parts of the turbomachine, such as a low pressure turbine, a low pressure transmission system, the propeller and a secondary flow guiding the flow of this propeller. These low pressure parts make it possible to contribute immediately to the generation of thrust. The known guiding principle for improving the propulsive efficiency consists of reducing the compression ratio of the propeller, thereby reducing the flow speed at the outlet of the turbomachine and the losses by kinetic energy linked to it.

[0009] One of the main consequences of this reduction in flow speed at the outlet of the turbomachine is that it is necessary to make the low pressure part (in particular the secondary flow) process a higher mass flow of air in order to ensure a given thrust level, which is fixed by the characteristics of the aircraft. This therefore leads to an increase in the bypass ratio of the turbomachine. The bypass ratio or BPR (English acronym for "ByPass Ratio") is defined as the ratio between the mass flow passing in the secondary flow (or otherwise called cold flow) around the gas generator, and the mass flow passing in the primary flow (or otherwise called hot flow) in the gas generator and supplying in particular the combustion chamber.This increase in secondary flow has the direct effect of requiring an increase in the diameter of the propeller, and consequently the external dimensions of the retention casing surrounding it in the case of the ducted propeller, as well as the nacelle constituting the aerodynamic envelope of this retention casing. To aim for high dilution rates, the retention casing is removed to move to configurations with unducted propellers since this retention casing was becoming too large, too heavy and generated significant capture drag.

[0010] In the case of a shrouded propeller, the nacelle surrounding the propeller includes an internal acoustic treatment which makes it possible to reduce noise emissions outside the turbomachine.

[0011] In the case of an unducted propeller, other solutions for reducing propulsive noise must be found. To address the noise emission problem, a noise reduction technology already known on fans and inspired in particular by the wings of nocturnal raptors consists of arranging serrations on the trailing edges of the blades (such as the so-called fan rotor blades) or on the leading edges of the blades (such as the so-called stator blades of a turbomachine rectifier). Serrations are aero-acoustic elements. They are characterized by a geometry in the form of teeth that are more or less numerous, more or less large and that evolve along the trailing edge or the leading edge. Serrations can cause variations of the blade chord as a function of radial height, with variable thicknesses and a very thin trailing or leading edge.

[0012] The principle of reducing noise emissions generated by the blades lies in spatially shifting the noise sources distributed along the leading edge or the trailing edge by means of serrations (or otherwise said undulations or teeth), which may or may not be identical. For this principle to apply, the dimensions (height, length, thickness, etc.) of the serrations must be adapted to the incident aerodynamic field (such as the air flow passing through the blades with more or less turbulence) which varies according to the engine speed of the turbomachine.

[0013] Furthermore, the clamping element must be both easily repairable (since it is visible to passengers) and resistant to damage of the HCF type (acronym for “High-Cycle Fatigue”) which can generate cracks in the clamping element (and consequently in the blade) during operation.

[0014] In addition, several other constraints must be taken into account for the production of blades made of composite material comprising such a clamping element, such as: - the clamping element has a complex geometry, in particular with teeth having variations in dimensions (such as its thickness, length, shape, spacing between the teeth, cambers forming angles [32, etc.) which can alter and form a misalignment with the composite material (in particular the woven fibers) during shaping in an RTM injection mold, - the placement of the clamping element on the leading edge or the trailing edge can be complex, particularly for complex geometries (dimensions and shape) of the aerodynamic profile blades, - the teeth of the clamping element have low thicknesses (around 2.5 mm minimum) which can be damaged during handling, and - produce the clamping element with a reasonable mass so as not to weigh down the propeller and with good mechanical properties to resist impact from external objects (such as birds, hailstones or lightning).

[0015] In addition to the aforementioned technical constraints, the manufacture of the blade in composite material comprising the clamping element can be long, complex and expensive.

[0016] In this context, it is interesting to propose a solution making it possible to overcome at least one of the aforementioned drawbacks, in particular by optimizing and making robust the integration of a clamping element in a blade made of composite material. Summary of the invention

[0017] The present invention provides a simple, effective and economical solution to the aforementioned drawbacks of the prior art.

[0018] For this purpose, the invention relates to a fiber preform of a blade for a tur- bomachine, in particular an aircraft, having a blade and a root, the blade comprising clamping elements on a leading edge and / or a trailing edge of the blade, the fiber preform being obtained by weaving fibers and which is embedded in a polymer matrix, the fiber preform comprising a first part intended to extend into the blade and a second part intended to extend into the root.

[0019] According to the invention, said fiber preform comprises a corrugated or toothed edge which is intended to extend into said clamping elements.

[0020] Thus, this solution makes it possible to achieve the aforementioned objective. For this, the invention proposes to link (and also to form) the clamping elements and the blade in a single piece (or in other words in a single piece and in a single piece) made of composite material. The clamping elements are thus integrated directly within the fiber preform forming the blade and the root of the blade, by the corrugated or toothed edge.

[0021] This single-piece connection is simple to implement (particularly in an automated manner), solid and difficult to damage during operation. In particular, the direct integration of the clamping elements within the fiber preform makes it possible to form a more robust blade, particularly with regard to the technical constraints mentioned in the technical background and with good cohesion of the fibers throughout the entire fiber preform. This significantly improves the mechanical strength of this blade during operation, for example in the turbomachine.

[0022] The invention therefore has the advantage of being based on a design that is simple to produce, offering very high reliability, and is not very penalizing in terms of cost, mass and size. In this way, the blade according to the invention helps to limit environmental impacts, in particular by reducing the mass.

[0023] The term "serration element" means a part comprising teeth projecting from at least part of this part. These teeth may have a U and / or V shape in axial section. These teeth may be more or less numerous, more or less large and move along this serration element. The serration element may also be designated by a tooth or undulation element.

[0024] The present invention also relates to a blade for a turbomachine, in particular for an aircraft, said blade comprising a blade and a root, the blade comprising a leading edge, a trailing edge, a lower surface and an upper surface connected to the lower surface by the leading edge and the trailing edge, the blade further comprising clamping elements on the leading edge and / or the trailing edge, said blade being made of composite material and comprising a fiber preform according to one of the particularities of the invention, said fiber preform extending into the blade and the root of the blade. According to the invention, the fiber preform comprises the corrugated or toothed edge which extends into the clamping elements.

[0025] The fiber preform and / or the blade according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another:

[0026] — fiber preform for the manufacture of the blade;

[0027] - the polymer matrix is ​​thermosetting or thermoplastic, for example epoxy base or a polymer of the LMPAEK® type marketed by Victrex;

[0028] — said edge of the fiber preform is corrugated and / or toothed;

[0029] — said edge of the fiber preform comprises undulations or teeth (or said otherwise projecting portions);

[0030] — said undulations or teeth have identical or different shapes. different from each other;

[0031] — said undulations or teeth each have a general polygonal shape (such as triangular, rectangular, etc.);

[0032] — said undulations have a profile obeying a periodic law, by example of sinusoidal type;

[0033] — the ripples are in the form of a periodic signal having one or more har moniques;

[0034] — said undulations or teeth are distributed more or less regularly along said edge of the fibrous preform;

[0035] — wavy or toothed edge extends over a predetermined length (or said otherwise a predetermined height) of the fiber preform;

[0036] — this predetermined length is between 50% and 100% of a length total (or otherwise said total height) of the fiber preform;

[0037] — the fiber preform is formed of fibers woven in two or three dimensions measurements;

[0038] — the fiber preform comprises carbon fibers, glass fibers, fibers aramid, ceramic fibers (such as silicon carbide) or a mixture of two or more of these fibers.

[0039] The present invention also relates to an aircraft turbomachine, comprising at least one blade made of composite material according to the invention.

[0040] The turbomachine may be a turbojet, turboprop or aircraft turboshaft engine.

[0041] The present invention further relates to a method of manufacturing a blade made of composite material according to one of the features of the invention, for a turbomachine, in particular for an aircraft.

[0042] The blade comprises a blade and a root, the blade comprising a leading edge, a leading edge trailing edge, an intrados and an extrados connected to the intrados by the leading edge and the trailing edge, the blade further comprising clamping elements on the leading edge and / or the trailing edge, said blade being made of composite material and comprising a fiber preform (in particular according to one of the particularities of the invention), said fiber preform extending into the blade and the root of the blade. This fibrous preform includes the corrugated or toothed edge that extends into the serration elements.

[0043] The method comprises the following steps: (a) production of a fiber preform by weaving fibers, this fiber preform comprising a part intended to extend into the blade, and a part intended to extend into the root of the blade, (b) shaping and stiffening the fiber preform in a preforming tool, (c) densification of the fiber preform in a mold by a resin to form the blade.

[0044] According to the invention, the method further comprises, before step (c), a step (i) of cutting the fiber preform to form a wavy or toothed edge which is intended to extend into the clamping elements of the blade.

[0045] The manufacturing method according to the invention makes it possible to facilitate and make more robust the integration of the clamping elements within the blade. For this, the clamping elements, corresponding to the corrugated or toothed edge of the fiber preform, are formed by cutting directly at the intermediate stage of the fiber preform for producing the blade, and in particular before the densification step. This has the following advantages: - lighten or maintain a reasonable mass of the blade by making the clamping elements, the blade and the root in a single composite material; - produce the clamping elements in a single cutting step without the need for additional steps (such as gluing, machining, etc.); - facilitate the production of the complex geometry of the clamping elements, in particular by directly producing the teeth and angles [32 by the mold at the densification stage; - minimize the loss of fibers and / or polymer matrix when cutting the fiber preform, in particular compared to a solution of direct machining of the clamping elements on the leading edge or the trailing edge; - use innovative cutting techniques; - automate all the steps or at least part of the steps of the process, - a significant gain in cost and manufacturing time of the blade; and - contribute to limiting environmental impacts.

[0046] The invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0047] - step (i) is carried out before step (b);

[0048] - step (i) is carried out after step (b);

[0049] - the cutting of said at least one edge of the fiber preform is carried out by at least a technique chosen from: a water jet, a circular blade, an ultrasonic knife and a pair of scissors;

[0050] - step (i) comprises the use of a cutting guide, comprising for example the shape of the wavy or toothed edge to be produced;

[0051] - the method further comprises a step (v) of depositing a tackifier on the preform fibrous at the wavy or toothed edge, this step (v) being carried out in step (b) or after step (i);

[0052] - step (i) is carried out over a predetermined length of the fiber preform,

[0053] — the tackifier comprises between 20% and 85% by mass of epoxy resin, preferably approximately 25% by mass of epoxy resin;

[0054] — the tackifier comprises between 15 and 80% by mass of solvent, preferably approximately 75% by mass of solvent. Brief description of the figures

[0055] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which:

[0056] [Fig.l] is a half schematic view in axial section showing an aircraft turbomachine with a ducted propeller and a ducted rectifier, the propeller and the rectifier each comprising blades;

[0057] [Fig.2] is a schematic perspective view showing a turbomachine with an unducted propeller and an unducted rectifier, the propeller and the rectifier each comprising blades;

[0058] [Fig.3] is a schematic profile view showing a first example of a blade of the turbomachine of [Fig.1] or [Fig.2], the blade comprising serration elements on a leading edge of the blade;

[0059] [Fig.4] is a schematic profile view showing a second example of a blade of the turbomachine of [Fig.1] or [Fig.2], the blade comprising clamping elements on a trailing edge of the blade;

[0060] [Fig.5] is a general block diagram of a method of manufacturing the blade of the invention;

[0061] [Fig.6] is a schematic view showing a cutting profile of a corrugated or toothed edge on a fiber preform of the blade;

[0062] [Fig.7] is a schematic side view of a first example of cutting the fiber preform to form the corrugated or toothed edge;

[0063] [Fig.8] is a perspective view of a second example of cutting the fiber preform to form the corrugated or toothed edge;

[0064] [Fig.9] is a perspective and partial view of a third example of cutting the fiber preform to form the corrugated or toothed edge;

[0065] [Fig. 10] is a perspective and partial view of a fourth example of cutting the fiber preform to form the corrugated or toothed edge;

[0066] [Fig.l 1] is a perspective view of a cutting guide tool on the fiber preform;

[0067] [Fig. 12a] is a perspective view of a mold allowing densification of the fiber preform;

[0068] [Fig. 12b] is an enlarged perspective view of the mold of [Fig. 12a];

[0069] [Fig. 13] is a block diagram of a first example of the manufacturing process of the dawn of invention;

[0070] [Fig. 14] is a block diagram of a second example of the method of manufacturing the blade of the invention.

[0071] Elements having the same functions in different implementations have the same references in the figures. Detailed description of the invention

[0072] By convention, in the description below, the terms “longitudinal” and “axial” qualify the orientation of structural elements extending in the direction of a longitudinal axis (such as a turbomachine). The terms “radial” or “vertical” qualify 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 a positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an inner face facing the longitudinal axis and an outer surface, opposite its inner surface. Similarly, the terms “upstream” and “downstream” are defined with respect to the direction of circulation of the gases in the aircraft propulsion assembly.

[0073] The invention can be applied in a non-limiting manner to a turbomachine 10, in particular an aircraft turbomachine. The turbomachine 10 can be a turbojet, turboshaft or turboprop.

[0074] The turbomachine 10 extends around a longitudinal axis X.

[0075] The turbomachine 10 conventionally comprises a gas generator which drives at at least one propeller 1. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the rotor of the propeller for its rotational drive.

[0076] A propeller 1 may be shrouded. This is the case of a fan in a turbomachine of the turbojet or turbofan type for example.

[0077] By way of example and in a non-limiting manner, [Fig. 1] illustrates such a turbomachine 10 comprising, from upstream to downstream in the direction of flow of the gases F along the longitudinal axis X, the shrouded propeller 1 (also called fan), at least one compressor (such as a low-pressure compressor 2 and / or a high-pressure compressor 4), a combustion chamber 5, at least one turbine 6 (such as a high-pressure turbine and / or a low-pressure turbine) and a nozzle (not shown in [Fig. 1])•

[0078] A propeller 1 may be unducted ([Fig.2]). This is the case of a turboprop for example.

[0079] By way of example and in a non-limiting manner, [Fig.2] illustrates such a turbomachine 10 comprising the unducted propeller 1.

[0080] The turbomachine 10 therefore comprises the propeller 1, whether it is shrouded or not shrouded upstream, and a rectifier 3 downstream.

[0081] The propeller 1 comprises blades 7 (called rotor blades) extending around the axis X. The blades 7 of the propeller 1 allow the suction of an air flow. This air flow in the case of the turbomachine 10 of [Fig.l] is in particular capable of being divided into a primary flow and a secondary flow. The primary flow passes through a primary vein of the turbomachine 10 while the secondary flow is directed towards a secondary vein surrounding the primary vein.

[0082] The rectifier 3 comprises vanes 7 (called stator vanes) extending around the axis X. The vanes 7 of the rectifier 3 make it possible to straighten the flow at the outlet of a rotor located upstream in order to provide maximum thrust at the outlet of the turbomachine 10.

[0083] In the following description, the invention will be described in the context of its application in a non-limiting manner to the blade 7, in particular with reference to FIGS. 3 and 4. This blade 7 may be mobile on the propeller 1 or fixed on the rectifier 3.

[0084] The blade 7 can extend as follows: - an elongation axis A (substantially vertical in figures 3 and 4) which is substantially perpendicular or inclined to the axis X of the turbomachine 10, - a longitudinal axis B (substantially horizontal in figures 3 and 4) which is substantially perpendicular to axis B, and - a transverse axis C which is substantially perpendicular to axes A and B.

[0085] The blade 7 comprises a blade 70 which can be connected to a root 76 of the blade. The blade 70 comprises a leading edge 73, a trailing edge 74, a lower surface 71 and an upper surface 72 connected to the lower surface 71 by the leading edge 73 and the trailing edge 74.

[0086] The blade 70 may have an aerodynamic profile to form the aerodynamic part of the blade 7. For this, the blade 70 may have a curved profile of variable thickness between the leading edge 73 and its trailing edge 74 of the blade 7.

[0087] In the examples of the figures, the blade 70 can extend along the axis A between a first end and a second end opposite the first end.

[0088] The foot 76 can be connected to the second end of the blade 70. It is intended to be fixed to a disk (not shown) for example mobile in rotation around the axis X. The second end is free and configured to form a tip 75 (or a head) of blade 7.

[0089] The blade 70 also comprises at least one serration element 8 on at least a portion of the leading edge 73 and / or at least a portion of the trailing edge 74. As mentioned below, the serration element makes it possible to reduce the noise of aerodynamic origin generated by the blade in operation.

[0090] The blade 70 may thus comprise clamping elements 8 located either at the leading edge 73 ([Fig. 3]) or at the trailing edge 74 ([Fig. 4]), or two different clamping elements 8 located, respectively, on the leading edge 73 and the trailing edge 74 (not illustrated in the figures). By way of example, the clamping elements 8 may be located on the leading edge 73 when the blade 7 corresponds to a propeller of the non-ducted turbomachine. The clamping elements 8 may be on the trailing edge 74 when the blade 7 corresponds to the OGV blade of the ducted turbomachine.

[0091] The clamping elements 8 may extend over a predetermined length (or in other words a predetermined height) of the leading edge 73 and / or the trailing edge 74. This predetermined length may be measured along the axis A. For example, this predetermined length of the clamping elements 8 may be between 50% and 100% of a total length (or total height) of the blade 70, in particular at the level of the leading edge 73 or the trailing edge 74.

[0092] In a non-limiting manner, [Fig. 3] illustrates clamping elements 8 along the entire length of the leading edge 73.

[0093] [Fig. 4] illustrates in a non-limiting manner a metal reinforcement 9 on the leading edge 73 and the clamping elements 8 on the trailing edge 74. The clamping elements 8 can extend over approximately 90% of the total length of the blade 70.

[0094] The clamping elements 8 may comprise undulations or teeth 82 (or in other words, projecting portions). For example, the clamping elements 8 may comprise between five and twenty teeth 82. These teeth 92 may be aligned with each other, in particular along the leading edge 73 or the trailing edge 74. The teeth 92 may extend partially or entirely over the leading edge 73 and / or the trailing edge 74. The teeth 92 may be identical or non-identical to each other.

[0095] The undulations or teeth 82 may have shapes that are identical to each other or different from each other.

[0096] The undulations or teeth 82 may each have a general polygonal shape (such as triangular, rectangular, etc.).

[0097] The ripples may have a profile obeying a periodic law, for example of the sinusoidal type. For example, the ripples may be in the form of a periodic signal having one or more harmonics.

[0098] The undulations or teeth 82 may be distributed more or less regularly along the leading edge and / or the trailing edge.

[0099] The blade 7 may optionally comprise the metal reinforcement 9. This metal reinforcement 9 at least partially covers the leading edge 73, in particular when the trailing edge 74 comprises the clamping elements 8. Advantageously, the metal reinforcement 9 may extend over the entire height (relative to the axis A) and over a lengthwise portion (relative to the axis B) of the intrados 71 and the extrados 72 from the leading edge 73.

[0100] Preferably, the metal reinforcement 9 may have a U or V shape in cross section relative to the axis A, so as to at least partially cover the leading edge 73.

[0101] The metal reinforcement 9 makes it possible to protect the blade (in particular the blade) against external impacts (gravel from a takeoff / landing runway, hailstones, birds, etc.) and against erosion of the blade.

[0102] The metal reinforcement 9 can be fixed by gluing or by projection of a film, for example metallic.

[0103] The metallic material of the metallic reinforcement 9 is for example titanium or an alloy such as a steel (for example a stainless steel) or a nickel and cobalt alloy (NiCo).

[0104] The blade 7 is made of composite material and comprises a fiber preform 700. The fiber preform 700 is obtained by weaving fibers and is embedded in a polymer matrix.

[0105] The fiber preform 700 comprises a part (called the first part) which is intended to extend into the blade 70 and a part (called the second part) which is intended to extend into the root 76. In other words, the fiber preform 700 can be made up and formed from the blade 70 and the root 76.

[0106] By “fiber preform” is meant an intermediate part for producing the final blade 7. The composite material may be, for example, a matrix composite organic (CMO) or ceramic (CMC).

[0107] Organic matrix composite materials (OMC) and ceramic matrix composite materials (CMC) replace metallic material parts in certain parts of turbomachines (such as blades). Furthermore, their use contributes to optimizing aircraft performance, in particular by improving the efficiency of the turbomachine and reducing the overall mass of the turbomachine, significantly reducing emissions harmful to the environment (CO, CO2, Nox, etc.).

[0108] The fiber preform 700 may be formed from two-dimensionally or three-dimensionally woven fibers. The fiber preform 700 may comprise carbon fibers, glass fibers, aramid fibers, ceramic fibers (such as silicon carbide), or a mixture of at least two of these fibers.

[0109] The polymer matrix (or the resin before densification) may be thermosetting or thermoplastic. For example, the polymer matrix may be based on epoxy, polyepoxide, polyimide, polybismaleimide, polyurethane, polyester or vinylester. Alternatively, the polymer matrix may be a polymer of the LMPAEK® type marketed by Victrex.

[0110] Advantageously, the fibrous preform 700 can be formed from carbon fibers which are woven in three dimensions and this fibrous preform is embedded in the epoxy-based polymer matrix.

[0111] One of the particularities of the invention is that the fiber preform 700 comprises a corrugated or toothed edge 702. This edge 702 is intended to extend into the clamping elements 8. In other words, the edge 702 of the fiber preform may correspond to the leading edge 73 or to the trailing edge 74 comprising the clamping elements 8 of the blade 7 called final and ready to be installed in the turbomachine 10.

[0112] Advantageously, the edge 702 of the fiber preform can be corrugated and / or toothed.

[0113] The edge 702 may therefore comprise undulations or teeth (or in other words, projecting portions). These undulations or teeth of the edge 702 may have shapes that are identical to each other or different from each other.

[0114] The undulations or teeth of the edge 702 may each have a general polygonal shape (such as triangular, rectangular, etc.).

[0115] The undulations of the edge 702 may have a profile obeying a periodic law, for example of the sinusoidal type.

[0116] The edge ripples 702 may be in the form of a periodic signal having one or more harmonics.

[0117] The undulations or teeth may be distributed more or less regularly along the edge 702 of the fiber preform.

[0118] The wavy or toothed edge 702 may extend over a predetermined length (or said otherwise a predetermined height) of the fiber preform 700. This predetermined length may be measured along an elongation axis of the fiber preform 700 which may substantially correspond to the axis A of the final blade. For example, this predetermined length of the corrugated or toothed edge 702 may be between 50% and 100% of a total length (or total height) of the fiber preform 700.

[0119] The wavy or toothed edge 702 can be obtained by cutting as described below with reference to the manufacturing method of the blade 7.

[0120] Advantageously, the blade 70, the foot 76 and the clamping elements 8 are formed from a single piece of composite material by means of the woven fiber preform 700 embedded in the polymer matrix.

[0121] With reference to Figures 5 to 14, the present application will now describe a method of manufacturing the blade 7 as described above.

[0122] According to the invention, the method comprises the following steps: (a) production of a fiber preform 700 by weaving fibers, (b) shaping and stiffening the fiber preform 700 in a preforming tool, (c) densification of the fiber preform 700 in a mold M by a resin to form the blade 7.

[0123] The method comprises, before step (c), a step (i) of cutting the fiber preform 700 to form a wavy or toothed edge 702 thereon which extends into the clamping elements 8. This step (i) can be carried out before step (b) or after step (b). Advantageously, the cutting step (i) can be carried out before the step (c) of densifying the fiber preform to directly form the geometry of the clamping elements, while minimizing losses of fibers and resin.

[0124] Steps (a), (b), (c) and (i) are summarized in [Fig.5] and also in Figures 13 and 14, in which the optional or alternative steps of the method are shown in dotted lines.

[0125] Step (a) may comprise a sub-step (aj) of weaving fibers to form a so-called standard profile of the fiber preform 700. As described previously, the fiber preform 700 comprises the first part intended to extend into the blade 70 and the second part intended to extend into the root 76. The first and second parts intended to extend into, respectively, the blade 70 and the 76, may be connected to each other. In other words, this part of the fiber preform may form the root 76 connected to the blade 70 which comprises the leading edge 73, the trailing edge 74, the intrados 71, the extrados 72 connected to the intrados 71 by the leading edge 73 and the trailing edge 74, and the clamping elements 8. This fiber preform 700 may be produced by weaving fibers in two or three dimensions.

[0126] Step (a) may further comprise a sub-step (a2) of pre-cutting, for example manually, any floating fibers (such as warp yarn fibers) on the woven fiber preform 700 obtained in sub-step (ai).

[0127] Step (a) may comprise a sub-step (a3) ​​of cutting the complete contour of the woven fiber preform 700 obtained in sub-step (aj or (a2).

[0128] Step (b) allows preforming of the woven fiber preform 700 obtained at the end of step (a) or (i). This step (b) can be carried out in a suitable preforming tool.

[0129] Step (b) may comprise a sub-step (bj) of applying water to the fiber preform obtained for example at the end of step (a) or step (i). This makes it possible to wet the fiber preform 700. The fiber preform is thus moistened with water, so that it is easier to handle.

[0130] The step may comprise a sub-step (b2) of positioning the fiber preform 700 obtained in step (a) or (i) in the preforming tool. For this, the fiber preform 700 may comprise tracer fibers on the surface which may be aligned with laser projections of positrons of theoretical tracer fibers of warp and weft threads formed for example by the preforming tool.

[0131] Step (b) may comprise a sub-step (b3) of drying by heating, for example by placing the closed preforming tool in an oven or an autoclave. Drying may be carried out with a temperature above 100°C and for a duration of a few hours. Drying makes it possible in particular to dry the water used for wetting or to extract it from the fiber preform.

[0132] The densification step (c) allows polymerization or hardening of the fiber preform 700, in particular of a polymer matrix resin so as to form the blade 7 in composite material. For this, the fiber preform 700 in particular obtained at the end of step (b) or (i) can be placed in a suitable mold M. The positioning of the fiber preform in the mold M can also be carried out using fiber tracers on the surface of the fiber preform and their laser projections.

[0133] With reference to figures 12a and 12b, the mold M can comprise geometries of the clamping elements 8 so that the densification makes it possible to obtain the densified (or embedded) fiber preform of the polymer matrix as close as possible to the geometry of the desired blade 7. The mold M can thus comprise the various undulations (in particular the angles [32 illustrated in [Fig.12b]) and / or camber of the blade 7 and of the clamping element 8.

[0134] The angle [32 can correspond to an angle between a plane tangential to the skeleton of the trailing edge (or in other words to an external surface of the trailing edge) and the X axis.

[0135] The polymer matrix (once the injection resin has been densified) may be, for example, a thermoplastic or thermosetting polymer resin, such as described above.

[0136] The cutting, for example by water jet, in step (i) can be carried out from a predetermined MT cutting profile which can be obtained by a computer-aided system. To define as accurately as possible the contour of the fiber preform, in particular the corrugated or toothed edge 702 making it possible to obtain the clamping elements 8, several data concerning the blade 7 to be produced are recorded in the computer-assisted system (such as the real and final geometry of the blade, the so-called “skeleton” surface of the blade, the geometry of the blade without the clamping elements (or in other words the blade without the “flattened” clamping elements, etc.). This makes it possible to form the so-called “flattened” blade 7 with the clamping elements at the leading edge 73 and / or the trailing edge 74 with these input data, for example on suitable software. Finally, the computer-assisted system makes it possible to extract the cutting profile MT ([Fig.6]) to carry out step (i) by water jet.Thus, the cutting of the fiber preform in step (i) is carried out according to the predetermined cutting profile MT to form in particular the wavy or toothed edge 702 ([Fig.7]).

[0137] Advantageously, the cutting in step (i) makes it easier to produce a complex and particular shape of the wavy or toothed edge 702. Thus, the cutting in step (i) the method may comprise producing the undulations or teeth of the edge 702 described above in step (such as the polygonal shape, the undulations in the form of the periodic signal having one or more harmonics, the profile obeying a periodic law, undulations or teeth of identical shapes to each other, undulations or teeth of different shapes from each other and / or the regular or random distribution of the undulations or teeth along the edge 702). In step (i), the wavy or toothed edge 702 of the fiber preform 700 may be produced by at least one technique chosen from: a water jet, a circular blade, an ultrasonic knife D2 and a pair of scissors D3.

[0138] [Fig.7] illustrates a first example of water jet cutting of the fiber preform to form the corrugated or toothed edge 702.

[0139] [Fig.8] illustrates a second example of cutting, for example manually, by the circular blade Di of the fiber preform to form the corrugated or toothed edge 702. This circular blade cutting is of the pneumatic type, reliable and easy to implement.

[0140] [Fig.9] illustrates a third example of cutting, for example manually, by the ultrasonic knife D2 of the fiber preform to form the wavy or toothed edge 702. The ultrasonic knife D2 can have a long, pointed blade.

[0141] [Fig. 10] illustrates a fourth example of cutting, for example manually, by the pair of scissors D3 of the fiber preform to form the wavy or toothed edge 702.

[0142] The fiber preform 700 may be cut directly by one of the aforementioned techniques to form the corrugated or toothed edge 702 and directly include the elements of serrations 8 on the leading edge 73 and / or the trailing edge 74.

[0143] Step (i) may comprise the use of a cutting guide G comprising, for example, the shape of the wavy or toothed edge 702 to be produced. In particular, the cutting guide G makes it possible to hold the fiber preform in position in order to be able to carry out the cutting using one of the aforementioned techniques ([Fig.l 1]).

[0144] Step (i) can be carried out over a predetermined length (or in other words a predetermined height) of the fiber preform 700. For example, this predetermined cutting length can be between 50% and 100% of the total length of the fiber preform 700, so as to form the wavy or toothed edge 702 over part or all of the length of the fiber preform.

[0145] The method may further comprise a step (v) of depositing a tackifier on the fiber preform 700 at the level of the corrugated or toothed edge 702, this step (v) being carried out in step (b) or after step (i).

[0146] The tackifier may consist of an epoxy resin dissolved in a solvent. The tackifier ensures good cohesion of the woven fibers of the fiber preform 700, in order to obtain good stiffening, particularly at the level of the corrugated or toothed edge(s) 702. In this way, cutting of the fiber preform is greatly facilitated.

[0147] The tackifier may comprise between 20% and 85% by mass of epoxy resin, preferably approximately 25% by mass of epoxy resin. The epoxy resin may be a polyepoxide resin of type PR520, a DiGlycidyl Ether of Bisphenol A resin (having the acronym DGEBA) or a polyepoxide resin based on DiGlycidyl Ether of Bisphenol F (having the acronym DGEBF).

[0148] The tackifier may comprise between 15 and 80% by mass of solvent, preferably approximately 75% by mass of solvent. The solvent may be acetone or any other solvent compatible with the epoxy resin used, i.e. allowing the epoxy resin to be solubilized.

[0149] Preferably, in step (b), the tackifier can be added to the fiber preform before the drying sub-step (b3).

[0150] Step (v) whether carried out in step (b) or after step (i), the tackifier can be added to the fiber preform before the densification step (c).

[0151] The tackifier may be sprayed at the corrugated or toothed edge 702. The amount of tackifier deposited may vary depending on the desired rigidity of the fiber preform 700, particularly at the corrugated or toothed edge 702. Preferably, the amount of tackifier deposited may be a few milliliters per square centimeter on the fiber preform 700.

[0152] The method may comprise a step (d) of final finishing and completion of the blade 7. By way of example, step (d) may comprise machining on the contour of blade 7 to remove excess length. The excess length removed can be between 10 and 30 mm.

[0153] [Fig. 13] illustrates in a non-limiting manner a first example of embodiment of the method of manufacturing the blade 7.

[0154] The method of the first example can successively comprise the following steps: - step (a) of producing the fiber preform 700 by weaving fibers, this step (a) comprising the sub-steps (aj) of weaving fibers and (a2) of pre-cutting floating fibers; - step (i) of cutting the fiber preform to form the wavy or toothed edge 702; - step (b) shaping and stiffening of the fiber preform 700, this step (b) includes: the sub-step (bi) of applying water to the fibrous preform, and sub-step (b2) of placing the fiber preform in the forming tool; step (v) of depositing the tackifier at the wavy or toothed edge 702, and the drying sub-step (b3); - step (c) densification of the fiber preform 700 to form the blade 7 with the clamping elements 8 at the leading edge 73 and / or the trailing edge 74; and - step (d) of final finishing and completion of dawn 7.

[0155] The first method example makes it possible to form the wavy or toothed edge 702 on the flattened fiber preform.

[0156] [Fig. 14] illustrates in a non-limiting manner a first example of embodiment of the method of manufacturing the blade 7.

[0157] The method of the second example can successively comprise the following steps: - step (a) of producing the fiber preform 700 by weaving fibers, this step (a) comprising the following sub-steps: the sub-step (adding of fiber weaving, sub-step (a2) of pre-cutting floating fibers, and the sub-step (a3) ​​of cutting the complete contour of the woven fiber preform 700; - step (b) shaping and stiffening of the fiber preform 700, this step (b) includes: the sub-step (bi) of applying water to the fibrous preform, the sub-step (b2) of placing the fiber preform in the forming tool, and the drying sub-step (b3); - step (i) of cutting the fiber preform to form the wavy or toothed edge 702; - step (v) of depositing the tackifier at the level of the wavy or toothed edge 702; - step (c) densification of the fiber preform 700 to form the blade 7 with the clamping elements 8 at the leading edge 73 and / or the trailing edge 74; and - step (d) of final completion and finishing of the blade 7.

[0158] The second exemplary method makes it possible to form the corrugated or toothed edge 702 on the preformed and dried fiber preform.

Claims

Claims

1. Fibrous preform (700) of a blade (7) for a turbomachine (10), in particular an aircraft, having a blade (70) and a root (76), the blade (70) comprising serration elements (8) on a leading edge (73) and / or a trailing edge (74) of the blade (70), the fibrous preform (700) being obtained by weaving fibers and which is embedded in a polymer matrix, the fibrous preform (700) comprising a first part intended to extend into the blade (70) and a second part intended to extend into the root (76), characterized in that said fibrous preform (700) comprises a corrugated or toothed edge (702) which is intended to extend into said serration elements (8).

2. Fibrous preform according to claim 1, characterized in that the matrix is ​​thermosetting or thermoplastic, for example epoxy-based.

3. Blade (7) for a turbomachine (10), in particular for an aircraft, said blade (7) comprising a blade (70) and a root (76), the blade (70) comprising a leading edge (73), a trailing edge (74), a lower surface (71) and an upper surface (72) connected to the lower surface (71) by the leading edge (73) and the trailing edge (74), the blade (70) further comprising clamping elements (8) on the leading edge (73) and / or the trailing edge (74), said blade (7) being made of composite material and comprising a fiber preform (700) according to claim 1 or 2, said fiber preform (700) extending into the blade (70) and the root (76) of the blade, characterized in that said fiber preform (700) comprises the corrugated edge (702) or toothed which extends into the elements of serrations (8).

4. Aircraft turbomachine (10) comprising at least one blade (7) made of composite material according to claim 3.

5. Method for manufacturing a blade (7) made of composite material according to claim 3, for a turbomachine (10), in particular an aircraft, the method comprising the following steps: (a) producing a fiber preform (700) by weaving fibers, this fiber preform (700) comprising a first part intended to extend into the blade (70), and a second part intended to extend into the root (76) of the blade, (b) shaping and stiffening the fiber preform (700) in a preforming tool, (c) densification of the fibrous preform (700) in a mold (M) by a resin to form the blade (7), characterized in that the method further comprises, before step c), a step (i) of cutting the fibrous preform (700) to form a wavy or toothed edge (702) which is intended to extend into the clamping elements (8) of the blade.

6. Manufacturing method according to claim 5, characterized in that step (i) is carried out before step (b).

7. Manufacturing method according to claim 5, characterized in that step (i) is carried out after step (b).

8. Manufacturing method according to any one of claims 5 to 7, characterized in that the cutting of said at least one edge (702) of the fiber preform is carried out by at least one technique chosen from: a water jet, a circular blade (Di), an ultrasonic knife (D2) and a pair of scissors (D3).

9. Manufacturing method according to any one of claims 5 to 8, characterized in that step (i) comprises the use of a cutting guide (G), comprising for example the shape of the wavy or toothed edge (702) to be produced.

10. Manufacturing method according to any one of claims 5 to 9, characterized in that it further comprises a step (v) of depositing a tackifier on the fibrous preform (700) at the level of the corrugated or toothed edge (702), this step (v) being carried out in step (b) or after step (i).

11. Manufacturing method according to any one of claims 5 to 10, characterized in that step (i) is carried out over a predetermined length of the fiber preform (700).

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