METHOD FOR MANUFACTURING A BLADE FROM COMPOSITE MATERIAL CONTAINING A CLAMPING ELEMENT

Abstract

The invention relates to a method for manufacturing a blade (7) made of composite material for a turbomachine, comprising the following steps: (a) production of a fibrous preform by weaving fibers and intended to form part of the blade, (b) shaping and stiffening of the fibrous preform in a preforming tool, (c) placement of the fibrous preform in a mold, (d) densification of the fibrous preform with a resin to form the blade, wherein, before and / or after step (c), the method further comprises a step (i) of introducing fiber webs into the mold so as to cover at least part of an edge of the fibrous preform, these fiber webs having a corrugated or serrated edge; during step (d), the fiber webs are also densified with the resin to form the serration element. Figure for the abstract: Figure 5

Description

Title of the invention: METHOD FOR MANUFACTURED A BLADE FROM COMPOSITE MATERIAL COMPRISING A CLAMPING ELEMENT technical field

[0001] The invention relates to the field of turbomachinery, particularly aircraft turbomachinery, and more specifically to the propulsion propellers of such turbomachinery which include blades. More particularly, the invention relates to a method for manufacturing a blade made of composite material for such turbomachinery, and more precisely to improving the noise reduction of these blades during operation. Technical background

[0002] An aircraft turbomachine conventionally comprises a gas generator that drives at least one propeller. The gas generator includes at least one compressor, one combustion chamber, and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the propeller rotor 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 may be unfaired. 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 having an intrados and an extrados connected to each other by a leading edge and a trailing edge.

[0006] It is known to manufacture turbomachine blades, such as fan or turbomachine stator blades, from composite material to reduce mass while maintaining good mechanical properties. For example, composite material blades are manufactured by injecting a resin, for example by resin transfer molding (RTM, acronym for "Resin Transfer Molding") into a fibrous preform.

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

[0008] The elements influencing this propulsive efficiency to the first order are those related to the low-pressure parts of the turbomachine, such as a low-pressure turbine, a The low-pressure transmission system consists of the propeller and a secondary flow guiding the flow over it. These low-pressure sections contribute immediately to thrust generation. The known guiding principle for improving propulsive efficiency is to reduce the propeller's compression ratio, thereby decreasing the flow velocity at the turbine outlet and the associated kinetic energy losses.

[0009] One of the main consequences of this decrease in flow velocity at the turbomachine outlet is that a higher mass flow rate of air must be treated in the low-pressure section (particularly the secondary flow) to ensure a given thrust level, which is determined by the aircraft's characteristics. This therefore leads to an increase in the turbomachine's bypass ratio. The bypass ratio, or BPR (Bypass Ratio), is defined as the ratio between the mass flow rate passing through the secondary flow (also called the cold flow) around the gas generator and the mass flow rate passing through the primary flow (also called the hot flow) in the gas generator, which feeds, in particular, the combustion chamber.This increase in secondary flow rate directly necessitates an increase in the propeller diameter, and consequently, in the external dimensions of the surrounding retention housing in the case of a shrouded propeller, as well as in the nacelle forming the aerodynamic envelope of this retention housing. To achieve high dilution rates, the retention housing is removed, switching to configurations with unshrouded propellers, since this retention housing became too large, too heavy, and generated significant drag.

[0010] In the case of a shrouded propeller, the nacelle surrounding the propeller includes internal acoustic treatment which reduces noise emissions outside the turbomachine.

[0011] In the case of an unfaired propeller, other solutions must be found to reduce propulsion noise. To address the noise emission problem, a noise reduction technology already known for fans and inspired in particular by the wings of nocturnal birds of prey consists of incorporating serrations (or simply serrations) on the trailing edges of the blades (such as so-called fan rotor blades) or on the leading edges of the blades (such as so-called stator blades of a turbomachine rectifier). Serrations are aeroacoustic elements. They are characterized by a tooth-like geometry, with varying numbers and sizes, extending along the trailing or leading edge. Serrations can cause variations in the blade chord as a function of the radial height, with varying 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 in other words, undulations or teeth), whether identical or not. 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 airflow passing through the blades with more or less turbulence) which varies according to the engine speed of the turbomachine.

[0013] Furthermore, the serration element must be both easily repairable (since it is visible to passengers) and resistant to damage of the type HCF (English acronym for "High-Cycle Fatigue") which can generate cracks in the serration 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 incorporating such a serration element, such as: - the serration element has a complex geometry with, in particular, teeth exhibiting variations in dimensions (such as its thickness, length, shape, spacing between the teeth, cambers forming angles [32, etc.]) which can alter and create a misalignment with the composite material (especially the woven fibers) during shaping in an RTM injection mold, - The placement of the serration element on the leading or trailing edge can be complex, particularly for complex geometries (dimensions and shape) of the airfoil blades, - the teeth of the serration element have thin walls (on the order of 2.5 mm minimum) which can be damaged during handling, and - produce the serration element with a reasonable mass so as not to weigh down the helix and with good mechanical properties to resist in particular after impact of 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 serration element can be long, complex and costly.

[0016] In this context, it is advantageous to propose a solution that overcomes at least one of the aforementioned drawbacks, particularly by optimizing and robustening the integration of a serration element into a blade made of composite material. Summary of the invention

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

[0018] To this end, the invention relates to a method for manufacturing a blade made of composite material for a turbomachine, in particular for an aircraft, said blade comprising a blade having a leading edge, a trailing edge, an intrados and an extrados extending between the leading edge and the trailing edge, the blade further comprising at least one serration element on the leading edge and / or the trailing edge, the process comprising the following steps: (a) production of a fibrous preform by weaving fibers, this fibrous preform being intended to form part of the blade, (b) shaping and stiffening of the fibrous preform in a preforming tool, (c) placing the fibrous preform in a mold, and (d) densification of the fibrous preform by a resin to form the blade.

[0019] According to the invention: - before and / or after step (c), the process further comprises a step (i) of introducing fibre sheets into the mold so as to cover at least part of an edge of the fibrous preform, these fibre sheets having a wavy or serrated edge, - during step (d), the fibre sheets are also densified by the resin to form said at least one serration element.

[0020] The manufacturing process according to the invention makes it easier and more robust to integrate the serration element within the blade. To this end, the invention proposes forming the serration element and the blade as a single unit (or in other words, as a single piece) in composite material. The fiber layers intended to form the serration element are thus directly attached to at least part of an edge of the fibrous preform before the densification step. This single-piece connection is simple to implement (particularly in an automated manner), strong, and difficult to damage during operation. In particular, the direct integration of the serration element onto the fibrous preform makes it possible to form a more robust blade, especially with respect to the technical constraints mentioned in the technical background, and with good fiber cohesion throughout the entire fibrous preform.This significantly improves the mechanical strength of this blade during operation, for example in the turbomachine.

[0021] Furthermore, the method according to the invention has the following advantages: - lighten or maintain a reasonable mass of the blade by making the serration element and the blade in one and the same composite material; - facilitate the realization of the complex geometry of the serration element, in particular by directly producing the teeth and angles [32 in the mold at the densification stage; - maintain a geometry of a reported subset of the fiber sheets on the edge of the fibrous preform, so as to limit the transmission of stresses from the fibrous preform to the hollow portions of the serration element; - facilitate the repair and / or replacement of the fiber layers of the element serrations; - minimize the loss of fibers and / or resin, for example when cutting the fibrous preform, especially compared to a direct machining solution of the serration element on the leading edge or trailing edge; - to automate all or at least part of the steps of the process; and - a significant gain in cost and manufacturing time of the blade.

[0022] The invention therefore has the advantage of being based on a simple design, offering very high reliability, and minimal impact in terms of cost, mass, and size. In this way, the blade obtained according to the process of the invention helps to limit environmental impacts, particularly by reducing its mass.

[0023] The term "serration element" refers to a part having teeth projecting from at least a portion of that part. These teeth may have a U and / or V shape in axial section. The number and size of these teeth may vary, and they may extend along the serration element. The serration element may also be referred to as a toothed or corrugated element.

[0024] The manufacturing process according to the invention may include one or more of the following features, taken individually or in combination with each other:

[0025] - in which: - before step (c), the first layers of fibers are positioned directly in the mold, and - after step (c), second layers of fibers are positioned directly on the edge of the fibrous preform or even on top of the first layers of fibers, so that the edge of the preform is sandwiched between the first and second layers of fibers;

[0026] - third layers of fibers are intercalated between the first and second tablecloths and located next to the edge, without covering it;

[0027] - before or during step (i), the process also includes a step (ii) of adding of a layer of glue between the layers of fibers and the edge of the fibrous preform, the glue layer being for example epoxy-based;

[0028] - the process further comprises, before step (b), a step (iii) of cutting the fibrous preform to form a recess in the fibrous preform;

[0029] - the mold comprises at least one cavity, part of which has a complete shape commentary on the wavy or toothed edge of the fiber sheets;

[0030] - before step (d), the process includes at least one compaction step of the fibrous preform and fiber sheets;

[0031] - the fiber sheets are made by weaving fibers or superimposing several layers of fibers;

[0032] - the fibrous preform and the fiber webs are pre-impregnated with a resin before step (d);

[0033] - the resin is thermosetting or thermoplastic, for example epoxy-based;

[0034] — step (d) is carried out by heating to a temperature between 150°C and 200°C, preferably around 180°C;

[0035] — the fibrous preform is formed of unidirectional (1D) woven fibers, in two dimensions (2D) or three dimensions (3D);

[0036] — the fibrous preform comprises carbon fibers, glass fibers, fibers aramid, ceramic fibers (such as silicon carbide) or a mixture of at least two of these fibers;

[0037] — the fiber webs comprise carbon fibers, glass fibers, aramid fibers, ceramic fibers (such as silicon carbide) or a mixture of at least two of these fibers;

[0038] — the fibre sheets have an elongated shape along said edge of the preform fibrous;

[0039] — the fibre sheets extend over at least 70% of the length of said edge of the fibrous preform;

[0040] — the fibre sheets extend at most over 90% of the length of said edge of the fibrous preform;

[0041] — at least some of the fibre layers have a first surface which covers di directly said edge of the fibrous preform and / or which is separated from this edge of the fibrous preform by other layers of fibers, and a second surface which directly covers the other layers of fibers or which is covered by these other layers of fibers, the first surface having a greater extent than the second surface;

[0042] — at least some of the fibre layers are only covered by layers of fibers or interleaved between two layers of fibers;

[0043] — at least some of the fibre layers do not cover the edge of the preform fibrous;

[0044] — the fibre sheets are pre-impregnated for example with a resin;

[0045] — the fibre sheets are dry (or in other words, non-prepregnant, i.e. that these sheets are not pre-impregnated with resin);

[0046] — the fibrous preform is dry (or in other words non-prepreg);

[0047] — the layers of fibers introduced into the mold comprise first layers of fibers and second layers of fibers, and possibly third layers of fibers

[0048] — the wavy or toothed edge is intended to form the serration element;

[0049] — said edge of the fibre sheets is corrugated and / or toothed;

[0050] — said edge of the fibre sheets comprises undulations or teeth (or said otherwise protruding portions);

[0051] — said undulations or teeth have identical or different shapes different from each other;

[0052] — said undulations or teeth each have a general polygonal shape (such as triangular, rectangular, etc.);

[0053] — said undulations have a profile obeying a periodic law, by example of sinusoidal type;

[0054] — the undulations are in the form of a periodic signal having one or more har moniques;

[0055] — said undulations or teeth are distributed more or less regularly along said edge of the fibrous preform.

[0056] The present invention may also relate to a composite material blade for a turbomachine, in particular for an aircraft, this blade being obtained by a manufacturing process according to one of the features of the invention.

[0057] The present invention may also relate to an aircraft turbomachine, comprising at least one blade made of composite material according to the invention.

[0058] The turbomachine can be a turbojet, turboprop or aircraft turboengine. Brief description of the figures

[0059] The present invention will be better understood and other details, features and advantages of the present invention will become more apparent upon reading the following description of a non-limiting example, with reference to the accompanying drawings in which:

[0060] [Fig.1] is a schematic half axial cross-sectional view representing a ducted propeller aircraft turbomachine and a ducted stator, the propeller and stator each comprising blades;

[0061] [Fig.2] is a schematic perspective view representing an unfaired propeller turbomachine and an unfaired stator, the propeller and stator each comprising blades;

[0062] [Fig.3] is a schematic profile view representing a first example of a turbine blade of the turbomachine of [Fig.1] or [Fig.2], the blade having a serration element on a leading edge of the blade;

[0063] [Fig.4] is a schematic profile view representing a second example of a turbine blade of the turbomachine of [Fig.1] or [Fig.2], the blade having a serration element on a trailing edge of the blade;

[0064] [Fig.5] is a block diagram of a manufacturing process for the blade of [Fig.3] or of the [Fig.4];

[0065] [Fig.6] is a schematic perspective view of a fibrous preform intended to form part of the blade of [Fig.4];

[0066] [Fig.7a] is a perspective view of a mold allowing densification of the fibrous preform;

[0067] [Fig.7b] is a schematic perspective and enlarged view of the mold of [Fig.7a];

[0068] [Fig.8] is a partial axial cross-sectional view schematically representing layers of fibers on an edge of the fibrous preform according to an embodiment of the invention;

[0069] [Fig.9] is a schematic perspective view of the mold of [Fig.8] including the deposit of fibre sheets;

[0070] [Fig. 10] is a schematic perspective view of the mold of [Fig. 9] further including the deposition of the fibrous preform;

[0071] [Fig. 1 1] is a schematic perspective view of the mold of [Fig. 10] further comprising the deposition of other layers of fibres;

[0072] [Fig. 12] is a partial axial cross-sectional view schematically representing a layer of glue intercalated between the fiber layers and the edge of the fibrous preform according to another embodiment of the invention.

[0073] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0074] By convention, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis (such as that of a turbomachine or a blade). The terms "radial" or "vertical" refer 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 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.

[0075] The invention can be applied, without limitation, to a turbomachine 10, in particular an aircraft turbomachine. The turbomachine 10 can be a turbojet, turboshaft engine or turboprop.

[0076] The turbomachine 10 can extend around a longitudinal axis X.

[0077] The turbomachine 10 can conventionally include a gas generator that drives at least one propeller 1. The gas generator includes at least one com a pressurizer, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the propeller rotor for its rotational drive.

[0078] A propeller 1 can be shrouded. This is the case of a fan in a turbomachine of the turbojet or turbofan type for example.

[0079] By way of example and without limitation, [Fig. 1] illustrates such a turbomachine 10 comprising, from upstream to downstream in the direction of gas flow F along the longitudinal axis X, the shrouded propeller 1 (also called the 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]).

[0080] A propeller 1 may be unfaired ([Fig.2]). This is the case for a turboprop engine, for example.

[0081] By way of example and without limitation, [Fig.2] illustrates such a turbomachine 10 comprising the unfaired propeller 1.

[0082] The turbomachine 10 can therefore include the propeller 1 whether it is shrouded or not upstream and a rectifier 3 downstream.

[0083] The propeller 1 may include blades 7 (called rotor blades) extending around the X-axis. The blades 7 of the propeller 1 allow the intake of an airflow. This airflow, in the case of the turbomachine 10 of [Fig. 1], is notably capable of splitting into a primary flow and a secondary flow. The primary flow passes through a primary channel of the turbomachine 10, while the secondary flow is directed towards a secondary channel surrounding the primary channel.

[0084] The rectifier 3 includes blades 7 (called stator blades) extending around the X axis. The blades 7 of the rectifier 3 make it possible to rectify the flow at the outlet of an upstream rotor in order to provide maximum thrust at the outlet of the turbomachine 10.

[0085] 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 figures 3 and 4. This blade 7 can be movable from the propeller 1 or fixed from the rectifier 3.

[0086] Dawn 7 can extend as follows: - an elongation axis A (approximately vertical in figures 3 and 4) which is approximately perpendicular or inclined to the X axis of the turbomachine 10, - a longitudinal axis B (approximately horizontal in figures 3 and 4) which is approximately perpendicular to axis B, and - a transverse axis C which is substantially perpendicular to axes A and B.

[0087] The blade 7 comprises a blade 70 that can be connected to a blade foot 76. The blade 70 includes a leading edge 73, a trailing edge 74, an intrados 71 and an extrados 72 extending between the leading edge 73 and the trailing edge 74.

[0088] The blade 70 can have an aerodynamic profile to form the aerodynamic part of the blade 7. For this, the blade 70 can have a curved profile of variable thickness between the leading edge 73 and its trailing edge 74 of the blade 7.

[0089] In the examples in Figures 3 and 4, the blade 70 can extend along the axis A between a first end and a second end opposite to the first end.

[0090] 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 movable in rotation around the axis X. The second end is free and configured to form a vertex 75 (or a head) of blade 7.

[0091] The blade 70 also includes 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 helps to reduce the aerodynamic noise generated by the blade in operation.

[0092] The blade 70 can thus comprise a serration element 8 located either at the leading edge 73 ([Fig. 3]) or at the trailing edge 74 ([Fig. 4]), or two different serration elements 8 located, respectively, on the leading edge 73 and the trailing edge 74 (not shown in the figures). By way of example, the serration element 8 can be located on the leading edge 73 when the blade 7 corresponds to that of the propeller 1 of the unfaired turbomachine. The serration element 8 can be on the trailing edge 74 when the blade 7 corresponds to that of the stator 3 of the faired turbomachine.

[0093] The serration element 8 may include undulations or teeth 82 (or, in other words, projecting portions). For example, the serration element 8 may include between five and twenty teeth 82. These teeth 82 may be aligned with each other, in particular along the leading edge 73 or the trailing edge 74. The teeth 82 may extend partially or completely over the leading edge 73 and / or the trailing edge 74. The teeth 82 may be identical or non-identical to each other. The teeth 82 may be designed to reduce noise in the mid-range emission spectrum without significantly worsening other frequencies at other engine speeds.

[0094] The undulations or teeth 82 may have identical shapes or different shapes from each other.

[0095] The undulations or teeth 82 can each have a general polygonal shape (such as triangular, rectangular, etc.).

[0096] The ripples may have a profile obeying a periodic law, for example, a sinusoidal one. For example, the ripples may be in the form of a periodic signal having one or more harmonics.

[0097] The undulations or teeth 82 can be distributed more or less regularly along the leading edge and / or the trailing edge.

[0098] The serration element 8 can cause variations in the blade chord as a function of the radial height (relative to the axis A), with variable thicknesses and a very thin leading edge 73 or trailing edge 74.

[0099] Furthermore, the blade 7 may optionally include a metal reinforcement (not shown in the figures). This metal reinforcement may at least partially cover the leading edge 73 or the trailing edge 74. Advantageously, the metal reinforcement may extend over the entire height (relative to axis A) and over a portion in length (relative to axis B) of the lower surface 71 and the upper surface 72 from the leading edge 73.

[0100] Preferably, the metal reinforcement may have a U or V shape in cross-section with respect to axis A, so as to cover at least part of the leading edge 73 or the trailing edge 74.

[0101] The metal reinforcement helps to protect the blade (in particular the blade blade) against external shocks (gravel from a runway, hailstones, birds, etc.) and against erosion of the blade.

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

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

[0104] The blade 7 is made of composite material. The blade 7 may include a fibrous preform 700 which may be embedded (or in other words densified) in a resin (or in other words a polymeric matrix after densification of the resin).

[0105] By "fibrous preform" is meant an intermediate part for the realization of the final blade 7. The composite material may be, for example, an organic matrix composite (OMC) or a ceramic matrix composite (CMC).

[0106] Organic matrix composites (OMCs) and ceramic matrix composites (CMCs) replace metallic parts in certain sections of turbomachinery (such as blades). Furthermore, their use contributes to optimizing aircraft performance, particularly by improving turbomachine efficiency and reducing the overall mass of the turbomachine, thereby significantly reducing harmful emissions (CO, CO2, NOx, etc.).

[0107] With reference to Figures 5 to 12, the present application will now describe a method for manufacturing the blade 7 as described above.

[0108] In accordance with the invention, the method for manufacturing the blade 7 in material The composite includes the following steps: (a) production of a fibrous preform 700 by weaving fibers, (b) shaping and stiffening of the fibrous preform 700 in a preforming tool, (c) placement of the fibrous preform 700 in a mold M, and (d) densification of the fibrous preform 700 by a resin to form the blade 7.

[0109] One of the distinctive features of the invention is that: - before and / or after step (c), the process further includes a step (i) of introducing fiber sheets 80 into the mold M so as to cover at least part of an edge 740 of the fibrous preform 700, these fiber sheets 80 having a corrugated or serrated edge 800, - during step (d), the fibre sheets 80 are also densified by the resin to form the serration element 8.

[0110] As mentioned previously, the introduction of fiber sheets 80 on the edge 740 of the fibrous preform allows, in particular during the densification step (d), the serration element 8 to be bound and formed in a monobloc fashion on the leading edge 73 or the trailing edge 74 of the blade.

[0111] Fig. 5 summarizes the steps of the manufacturing process of the invention, in which the optional steps of the process are represented by dotted lines.

[0112] In step (a), the fibrous preform 700 can be formed from woven fibers in two dimensions or in three dimensions.

[0113] The fibrous preform 700 may include carbon fibers, glass fibers, aramid fibers, ceramic fibers (such as silicon carbide) or a mixture of at least two of these fibers.

[0114] The fibrous preform 700 can be pre-impregnated with a resin, in particular before the densification step (d). Alternatively, the fibrous preform 700 can be said to be "dry", i.e., that it is not pre-impregnated with resin.

[0115] The fibrous preform 700 is intended to form part of the blade 70. In particular, the fibrous preform 700 can form the leading edge 73, the trailing edge 74, the lower surface 71 and the upper surface 72 of the blade 70.

[0116] The fibrous preform 700 may include at least one edge 740. This edge 740 may be intended to form the leading edge 73 or the trailing edge 74 of the blade 70. In other words, the edge 740 may extend into the leading edge 73 or the trailing edge 74. The edge 740 may have an elongated shape along a plane substantially parallel to the axis A. The edge 740 may be smooth and flat.

[0117] Step (a) may also include pre-cutting, for example manually, any loose fibers (such as warp yarn fibers) on the preform fibrous 700 obtained after weaving of fibers.

[0118] Advantageously, the process may further include, before step (b), a step (iii) of cutting the fibrous preform 700 to form a recess 742 in the fibrous preform 700. This recess 742 makes it possible in particular to form an edge corresponding in particular to the edge 740 and with a smooth surface suitable for receiving the fiber sheets 80.

[0119] Alternatively, the recessed surface 742 may not be smooth. In this configuration, the recessed surface 742 may have, for example, a zigzag, curved, or mixed surface.

[0120] The recess 742 (or, in other words, a hollowed-out portion) can be formed at the edge 740 of the fibrous preform and / or towards the interior of the fibrous preform 700 (namely, on an intrados and / or an extrados face of the fibrous preform). Figure 6 illustrates, without limitation, the recess 742 at the edge 740 of the fibrous preform 700, which is intended to form the trailing edge 74. Alternatively, the recess 742 can be located on an edge of the fibrous preform on the side of the leading edge 73.

[0121] The recess 742 can extend over at least 70% of the length of the edge 740 of the fibrous preform. The length of the edge 740 can be measured substantially along axis A. In particular, the recess 742 can extend over at most 90% of the length of the edge 740 of the fibrous preform.

[0122] The cutting of the fibrous preform 700 can be carried out by at least one technique selected from: a water jet, a circular blade, an ultrasonic knife, and a pair of scissors. The ultrasonic knife can have a long, pointed blade.

[0123] Step (b) allows for preforming the woven fibrous preform 700 obtained at the end of step (a) or (iii). This step (b) can be carried out in suitable preforming tooling (not shown in the figures).

[0124] Step (b) may include a substep (bj) of applying water to the fibrous preform obtained, for example, at the end of step (a) or step (iii). This allows the fibrous preform 700 to be wetted. The fibrous preform is thus moistened with water, making it easier to handle.

[0125] Step (b) may include a substep (b2) of positioning the fibrous preform 700 obtained in step (a) or (iii) in the preforming tooling. For this purpose, the fibrous preform 700 may have tracer fibers on its surface which can be aligned with laser projections of theoretical tracer fiber positions of warp and weft yarns formed, for example, by the preforming tooling.

[0126] Step (b) may include a substep (b3) of drying by heating, for example by placing the closed preforming tooling in an oven or autoclave. Drying may be carried out at a temperature above 100°C and for a duration of a few hours. Drying allows, in particular, the water used for wetting to be extracted from the fibrous preform.

[0127] In step (c), the fibrous preform 700, obtained in particular at the end of step (b) or (i), can be placed in a suitable mold M. The positioning of the fibrous preform in the mold M can also be carried out using fiber tracers on the surface of the fibrous preform and their laser projections.

[0128] With reference to Figures 7a and 7b, the mold M may include geometries of the serration element 8, such that the fibrous preform 700 and the densified (or embedded) fiber layers 80 of the resin are as close as possible to the desired geometry of the blade 7. The mold M may thus include the various undulations (in particular the angles [32 illustrated in [Fig. 7b]) and / or camber of the blade 7 and the serration element 8.

[0129] The angle

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

[0130] Advantageously, the mold M can include at least one cavity M7 of which a part M80 has a shape complementary to the wavy or toothed edge 800 of the fiber sheets 80. This makes it easier to form the serration element 80 with its desired tooth geometry 82.

[0131] In particular, the cavity M7, intended to form the blade 7, may comprise a first cavity portion M7Oo and a second cavity portion M80. The first cavity portion M7Oo may have a shape complementary to the fibrous preform 700, to facilitate the positioning and subsequent densification of the fibrous preform 700 in the mold. The second cavity portion M80 may be configured to receive the fiber sheets 80 (preferably the corrugated or toothed edge 800).

[0132] Advantageously, the 800 edge can be wavy and / or toothed.

[0133] The edge 800 may therefore include undulations or teeth (or in other words, protruding portions). These undulations or teeth of the edge 800 may have identical or different shapes.

[0134] The undulations or teeth of the edge 800 can each have a general polygonal shape (such as triangular, rectangular, etc.).

[0135] The undulations of the edge 800 may have a profile obeying a periodic law, for example of sinusoidal type.

[0136] The undulations of the edge 800 can be in the form of a periodic signal having one or more harmonics.

[0137] The undulations or teeth can be distributed more or less regularly along the edge 800 of the fibrous preform.

[0138] Step (i) of introducing fiber mats 80 into the mold M can be carried out before step (c) and / or after step (c).

[0139] The fibre webs 80 can be made by weaving fibre or by superimposing several layers of fibre.

[0140] The fiber webs 80 may include carbon fibers, glass fibers, aramid fibers, ceramic fibers (such as silicon carbide) or a mixture of at least two of these fibers.

[0141] The type of weaving of the fiber webs 80 (for example in two dimensions or three dimensions), the orientation of the fibers (for example from 0° and / or 45°) and / or the nature of the fibers (for example carbon fibers, aramid fibers, etc.) can vary according to the desired stiffness.

[0142] The fiber webs 80 can be pre-impregnated with a resin, in particular before the densification step (d). Alternatively, the fiber webs 80 can be said to be "dry", i.e., they are not pre-impregnated with resin.

[0143] The fibre sheets 80 can have an elongated shape, particularly along the edge 740 of the fibrous preform.

[0144] The fiber layers 80 can extend over at least 70% of the length of the edge 740 of the fibrous preform (relative to axis A). In particular, the fiber layers 80 can extend over a maximum of 90% of the length of the edge 740 of the fibrous preform.

[0145] Advantageously, at least some of the fibre 80 mats can be covered only by fibre 80 mats or interleaved between two fibre 80 mats.

[0146] At least some of the fibre layers 80 may not cover the edge 740 of the fibrous preform 700.

[0147] At least some of the fiber layers 80 have a first surface 812 and a second surface 814, the first surface 812 having a larger extent than the second surface 814. The first surface 812 directly covers the edge 740 of the fiber preform and / or is separated from this edge 740 of the fiber preform by other fiber layers. The second surface 814 directly covers the other fiber layers or is covered by these other fiber layers. In particular, when the fiber sheets 80 comprise several fiber sheets superimposed one on top of the other, the first surface 812 of some of the fiber sheets may be that which directly covers the edge 740, and that of the superimposed fiber sheets (for example the sheets furthest out with respect to axis B) which may be separated from this edge 740 by other fiber sheets arranged between the edge 740 and the superimposed fiber sheets.

[0148] Figures 8 to 12 illustrate a preferred embodiment, in which the fiber layers 80 may comprise first 810 and second 820 layers of fibers, and possibly third layers of fibers 830 intercalated at least partially between the first 810 and second 820 layers of fibers.

[0149] The first 810 and second 820 fiber layers can each have: - a surface 812a of the first surface 812 which directly covers the edge 740, - another surface 812b of the first surface 812 which is separated from this edge 740 by another fiber layer from among the corresponding first 810 or second 820 fiber layers, - a surface 814a of the second surface 814 which directly covers the third layers of fibers 830, and / or - another surface 814b of the second surface 814 which is covered by another fibre sheet among the first 810 or second 820 corresponding fibre sheets.

[0150] The third fiber layers 830 may only have the second surface 814. In particular, at least some fiber layers among the third fiber layers 830 may comprise: - the surface 814a of the second surface 814 which can directly cover the first 810 or second 820 layers of fibers, and / or - the other surface 814b which can be covered by other fibre layers among the third fibre layers 830.

[0151] Figure 8 illustrates, in a non-limiting manner, the first fiber layers 810 having the first surface 812, 812a, 812b and the second surface 814, 814a, 814b, and the third fiber layers 830 having the second surface 814, 814a, 814b. The first surface 812 has a greater extent than the second surface 814. Thus, the second surface 814 of the fiber layers 810, 820, 830 can extend beyond the edge 740, or in other words, along the edge 740.

[0152] With reference to [Fig. 8], a fiber layer from among the first 810 and second 820 fiber layers can only be covered by another fiber layer from among the corresponding first 810 and second 820 fiber layers. Alternatively, a fiber layer from among the first 810 and second 820 fiber layers can be interleaved between two fiber layers from among the corresponding first 810 and second 820 fiber layers, particularly when more than two fiber layers 810, 820 are superimposed on one another.

[0153] On [Fig.8], the third layers of fibers 830 may not cover the edge 740 of the fibrous preform.

[0154] Advantageously, before step (c), the first layers of fibers 810 can be positioned directly in the mold M, and after step (c), the second layers of fibers 820 can be positioned directly on the edge 740 of the fibrous preform 740 or even on the first layers of fibers 810, so that the edge 740 of the fibrous preform 740 is intercalated between the first 810 and second 820 layers of fibers.

[0155] The third layers of fibers 830 can be intercalated between the first 810 and second 820 layers and located next to the edge 740, without covering it.

[0156] With reference to [Fig.9], the first layers of fibre 810 can be positioned, for example manually, in the second part of cavity M80 of the mold M.

[0157] With reference to [Fig. 10], the fibrous preform 700 obtained in step (b) can be positioned, for example manually, in the first part of cavity M700 of mold M. More particularly, the edge 740 of the fibrous preform can be positioned on the first layers of fibers 810, so that a part of these first layers of fibers 810 covers a first face of the edge 740 (in particular at the level of the recess 742) and the other part of these first layers of fibers 810 partially forms the wavy or toothed edge 800.

[0158] With reference to [Fig. 11], the second layers of fibers 820 can be positioned, for example manually, in the second part of cavity M80 of the mold M. In particular, the second layers of fibers 820 can be positioned on a second face of the edge 740 of the fibrous preform (in particular of the indentation 742) and on the first layers of fibers 810 (in particular at the corrugated or serrated edge 800). The second layers of fibers 820 can be superimposed on the first layers of fibers 810, so that the edge 740 is at least partially interposed between the first 810 and second 820 layers of fibers.

[0159] Optionally, the third layers of fibers 830 can be intercalated between the first 810 and second 820 layers of fibers, outside the edge 740 of the fibrous preform.

[0160] The process may also include a step (ii) of adding a layer of glue 9 between the fiber layers 80 and the edge 740 of the fibrous preform 700. This step (ii) may be carried out before or during step (i).

[0161] Fig. 12 illustrates in a non-limiting way the glue layer 9 intercalated between the edge 740 of the fibrous preform and the fiber layers 810, 820, 830.

[0162] The adhesive layer 9 may be epoxy-based. For example, the adhesive layer 9 may be a PR520 type epoxy resin or an AF191-M type epoxy marketed, for example, by the company 3M.

[0163] The process may include at least one compaction step of the fibrous preform 700 and the fiber webs 80. This compaction step may be carried out before step (d). The compaction step may be carried out during or after step (c) of placing the fibrous preform 700 and the fiber webs 80 in the mold M, in which the fibrous preform 700 and / or the fiber webs 80 may be pre-impregnated or dry.

[0164] By way of example, the compaction step allows several layers of fibers 80 to be assembled on the fiber preform 700, and then a protective film and a tarpaulin to be placed around the mold M. Next, a vacuum is created in the tarpaulin, so as to apply a predetermined pressure to compact the fiber preform 70 and the layers of fibers 80. The compaction step can be carried out over a period of, for example, about 15 minutes.

[0165] The compaction step can be repeated every four to five additional layers of fiber 80 until the desired final number of layers of fiber 80 is reached.

[0166] The compaction step makes it possible in particular to limit porosity and delamination, and also to limit a possible height difference (in particular between the fiber layers 80 and the fibrous preform 700) which may correspond to a greater thickness than desired.

[0167] A single compaction step may be sufficient when the number of fiber layers 80 is, for example, less than three fiber layers 80 to form the corrugated or serrated edge.

[0168] Several compaction steps may be required when the number of superimposed fiber layers 80 is, for example, greater than four fiber layers 80 to form the corrugated or serrated edge.

[0169] The densification step (d) allows polymerization or hardening of the fibrous preform 700 and the fiber webs 80, in particular of the resin in polymer matrix so as to form the blade 7 in composite material.

[0170] Step (d) can be carried out by heating to a temperature between 150°C and 200°C, preferably about 180°C.

[0171] The resin (for example, that which is injected in step (d) and / or that pre-impregnates the fiber webs 80) may be thermosetting or thermoplastic. For example, the resin may be based on epoxy, polyepoxide, polyimide, polybis-maleimide, polyurethane, polyester, or vinylester. Alternatively, the resin may be a polymer of the type LMPAEK® marketed by Victrex.

[0172] Advantageously, the fibrous preform 700 can be formed from carbon fibers that are woven in three dimensions, and this fibrous preform can be embedded in the epoxy-based resin. The fiber webs 80 can be formed from carbon fibers that are woven and pre-impregnated with a resin of the HexPly® 8552 or MTM49-L type.

[0173] In the case of pre-impregnated fiber webs 80, during step (d), the injected resin (e.g., PR520 epoxy) allows these fiber webs 80 to be bonded to the edge 740 of the fiber preform. This injected resin cannot impregnate fiber webs 80 that are pre-impregnated with resin (e.g., HexPly® 8552 or MTM49-L resin). Heating in step (d), by example at 180°C, allows simultaneous polymerization and hardening of the injected resin (e.g. PR520 epoxy resin) and the resin impregnating the fiber webs 80 (e.g. HexPly® 8552 or MTM49-L resin) and the fibrous preform 700.

[0174] In the case of dry fiber webs 80, the injected resin (for example, PR520 epoxy resin) in step (d) can impregnate the fibers of both the fiber webs 80 and the fibrous preform 700. Heating in step (d), for example to 180°C, thus allows simultaneous polymerization and hardening of the injected resin (for example, PR520 epoxy resin) which therefore impregnates both the fiber webs 80 and the fibrous preform 700.

[0175] The process may include a final finishing step (e) of the blade 7. By way of example, step (e) may include machining the contour of the blade 7 obtained in step (d) to remove excess length. The excess length removed may be between 10 and 30 mm.

Claims

Demands

1. A method for manufacturing a blade (7) of composite material for a turbomachine (10), in particular for an aircraft, said blade (7) comprising a blade (70) having a leading edge (73), a trailing edge (74), an intrados (71) and an extrados (72) extending between the leading edge (73) and the trailing edge (74), the blade (70) further comprising at least one serration element (8) on the leading edge (73) and / or the trailing edge (74), the method comprising the following steps: (a) production of a fibrous preform (700) by weaving fibers, this fibrous preform being intended to form a portion of the blade (70), (b) shaping and stiffening of the fibrous preform (700) in a preforming tool, (c) placement of the fibrous preform (700) in a mold (M), (d) densification of the fibrous preform (700) by a resin to form the blade (7), characterized in that: - before and / or after step (c),The process further comprises a step (i) of introducing fiber webs (80) into the mold (M) so as to cover at least part of an edge (740) of the fibrous preform (700), these fiber webs (80) having a corrugated or serrated edge (800), - during step (d), the fiber webs (80) are also densified by the resin to form said at least one serration element (8).

2. A manufacturing method according to claim 1, wherein: - before step (c), first layers of fibers (810) are positioned directly in the mold (M), and - after step (c), second layers of fibers (820) are positioned directly on the edge (740) of the fibrous preform or even on the first layers of fibers (810), so that the edge (740) of the preform is intercalated between the first (810) and second (820) layers of fibers.

3. A manufacturing method according to claim 2, wherein third layers of fibers (830) are interleaved between the first (810) and second (820) layers and located next to the edge (740), without covering it.

4. A manufacturing method according to claim 1 or 2, wherein, before or during step (i), the process also includes a step (ii) of adding a layer of glue (9) between the fiber sheets (80) and the edge (740) of the fibrous preform (700), the glue layer being for example epoxy-based.

5. A manufacturing method according to any one of the preceding claims, wherein the method further comprises, prior to step (b), a step (iii) of cutting the fibrous preform (700) to form a recess (742) in the fibrous preform.

6. A manufacturing method according to any one of the preceding claims, wherein the mold (M) comprises at least one cavity, a portion of which has a shape complementary to the corrugated or toothed edge (800) of the fiber webs (80).

7. A manufacturing process according to any one of the preceding claims, wherein prior to step (d), the process includes at least one compaction step of the fibrous preform (700) and the fiber webs (80).

8. A manufacturing method according to any one of the preceding claims, wherein the fiber webs (80) are made by weaving fibers or superimposing several layers of fibers.

9. A manufacturing method according to any one of claims 1 to 8, wherein the fibrous preform (700) and the fiber webs (80) are pre-impregnated with a resin before step (d).

10. A manufacturing method according to any one of the preceding claims, wherein the resin is thermosetting or thermoplastic, for example epoxy-based.

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