Composite material blade comprising a clamping element and its manufacturing process

Abstract

The invention relates to a composite material turbine blade (7) for a turbomachine, comprising a blade (70) having a leading edge (73), a trailing edge (74), an intrados (71) and an extrados (72), the blade further comprising at least one serration element (8) formed of a succession of teeth (82) and grooves (84) extending along at least a portion of the leading edge (73) and / or the trailing edge (74), wherein the blade (70) comprises a body (79) formed of a first fibrous preform (702) embedded in a resin and the at least one serration element (8) is formed of a second fibrous preform (704) embedded in a resin, the at least one serration element (8) being connected to the body (79) by at least one fusible link (78) configured to break when a force is applied to the at least one element of serrations (8) exceeds a predetermined threshold. Figure for the abbreviation: Figure 4

Description

Title of the invention: COMPOSITE MATERIAL BLADE COMPRISING A CLAMPING ELEMENT AND ITS MANUFACTURING METHOD 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 composite material blades for such turbomachinery, as well as a method for manufacturing such blades. More precisely and advantageously, such blades make it possible to improve the noise reduction of these blades during operation. Technical background

[0002] A propulsion propeller for a turbomachine, particularly for aircraft, may be shrouded as is the case of a fan for example, or may be unshrouded as is the case of an "open-rotor" type architecture for example.

[0003] A propeller generally comprises a plurality 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 of the blade.

[0004] Currently, more and more blades are made of composite material to reduce mass while maintaining good mechanical properties. For example, composite material blades 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 fibrous preform.

[0005] 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 specifically the propulsive efficiency which characterizes the efficiency with which the energy communicated to the air passing through the engine is converted into useful thrust.

[0006] 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 low-pressure transmission system, the propeller, and a secondary flow guiding the flow over this propeller. These low-pressure parts contribute immediately to thrust generation. The known guiding principle for improving propulsive efficiency consists of reducing the rate of compression of the propeller, thereby reducing the flow velocity at the turbomachine outlet and the associated kinetic energy losses.

[0007] 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 known as the cold flow) around the gas generator and the mass flow rate passing through the primary flow (also known as 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.

[0008] In the case of a shrouded propeller, the nacelle surrounding the propeller includes internal acoustic treatment which reduces noise emissions outside the turbomachine.

[0009] 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 grooves running 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.

[0010] The principle of reducing noise emissions generated by the blades lies in spatially shifting the noise sources distributed along the leading or 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 aerodynamic field. incident (such as the airflow passing through the blades with more or less turbulence) which varies according to the engine speed of the turbomachine.

[0011] 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.

[0012] Furthermore, several other constraints must be taken into account for the production of composite material blades incorporating such a serration element, such as: - the serration element has a complex geometry, notably with teeth exhibiting variations in dimensions (such as its thickness, length, shape, spacing between the teeth, cambers forming angles [32 each corresponding to an angle between a plane tangential to an external surface of the trailing edge and an axis of elongation of the blade, etc.) which can alter and create a misalignment with the composite material (particularly the woven fibers) during shaping in an RTM injection mold, - forces passing through the hollows of the serration element can damage the blade, 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).

[0013] 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.

[0014] 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

[0015] The present invention offers a simple, effective and economical solution to the aforementioned disadvantages of the prior art.

[0016] For this purpose, the invention relates to a composite material blade for a turbomachine, in particular for aircraft, said blade comprising a blade formed by at least one fibrous preform embedded in a resin and extending along an axis (A) of elongation, the blade comprising a body which has a leading edge, a trailing edge, an intrados and an extrados connected to the intrados by the leading edge and the trailing edge, the blade further comprising at least one serration element formed of a succession of teeth and hollows extending along at least a part of the leading edge and / or the trailing edge.

[0017] According to the invention, said at least one serration element is connected to the body by at least one fusible link configured to break when a force applied to said at least one serration element exceeds a predetermined threshold.

[0018] Thus, this solution makes it possible to achieve the aforementioned objective. The integration of the fusible link prevents the serration element from damaging the blade body when a force applied to this serration element exceeds a predetermined threshold. More specifically, when a force exceeding the predetermined threshold is applied, particularly at the serrations of the serration element, a force (or, in other words, a stress) known as the breaking force exceeding the predetermined threshold is applied to the fusible link, causing it to break. For example, the fusible link can be designed to break under one or more breaking forces chosen from tension, compression, shear, torsion, and / or bending. The breaking of the fusible link allows the serration element to be separated from the blade body (and therefore from the rest of the blade).In this way, the overstress (or in other words, an overload) applied to the serration element does not propagate to the blade body, and thus does not damage the blade. Consequently, the blade incorporating such a fusible serration element is robust and safe when a force exceeding the predetermined threshold is applied to the serration element.

[0019] Furthermore, the detached serration element can be replaced easily and at a lower cost, rather than repairing or reproducing and replacing the entire blade. The invention also makes it possible to control and limit the mass of material lost following damage to the blade.

[0020] Furthermore, the fusible link can be formed directly within the fibrous preform intended to form the blade body and the serration element. This 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 forming the composite material of the blade. As a result, the mechanical strength of this blade during operation, for example in the turbomachine, is significantly improved.

[0021] Thus, the blade 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 realizing the succession of teeth and hollows (which include angles

[32] ) at the level of the leading edge and / or the trailing edge of the blade; - limit and / or divert the transmission of stresses from the serration element (especially passing through the hollows) to the body of the blade; - facilitate the repair and / or replacement of the serration element (for example, by bonding a new serration element piece to the blade); and - 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.

[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 according to the invention helps to limit environmental impacts, particularly by making the blade more robust with a longer lifespan.

[0023] The term "serration element" refers to a part having teeth projecting on 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 term "predetermined threshold" refers to the force exerted on the serration element during normal operation that maintains the fusible link intact, in particular without damaging the blade. This predetermined threshold is therefore exceeded when this force exerts an excessive overload or overstress on the serration element.

[0025] The blade according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0026] - at least one fusible link comprises a first fusible link line which extends at least in part along the leading and / or trailing edge;

[0027] — at least one fusible link comprises a first fusible link line which extends along the A-axis of elongation, between this A-axis and the leading and / or trailing edge;

[0028] — the first line is located at least partly on the intrados and / or at least in part on the extrados;

[0029] — the first line extends in a straight or curved manner;

[0030] - at least one fusible link further comprises second connecting lines fuses that extend between the first fuse bond line and the leading and / or trailing edge;

[0031] — the second lines are each located at least partly on the intrados and / or the less partly on the extrados;

[0032] — the second lines each extend in a straight or curved manner;

[0033] — at least some of the second fusible link lines are parallel between they ;

[0034] - the body is formed from a first fibrous preform embedded in a resin, and said at least one serration element is formed of at least one second fibrous preform embedded in a resin;

[0035] - at least one fusible link is made with a resin, for example epoxy;

[0036] - at least one fusible link is made from short fibers embedded in the resin, short fibers having a length less than or equal to 20 mm, preferably the length is between 2 and 15 mm;

[0037] — the short fibers have a titration between 10 and 100 K, preferably the the titration is between 12 and 96 K;

[0038] - at least one fusible link comprises pins or bars delimiting between them, or she, the gaps filled by the resin;

[0039] - at least one fusible link is formed by a first edge of the body which is fitted together by complementary shape into a second edge of said at least one serrated element;

[0040] — at least one fusible link comprises a first edge of the body which is fitted by complementarity of form in a second edge of said at least one element of serrations;

[0041] — the first fibrous preform has a first edge which is fitted by complementary shape in a second edge of the second fibrous preform;

[0042] - at least one fusible link is formed by a thinning of the thickness of the pale ;

[0043] - the first and second fibrous preforms are formed in one piece.

[0044] The present application may also relate to an aircraft turbomachine, comprising at least one blade made of composite material according to one of the features of the invention.

[0045] The turbomachine can be a turbojet, turboprop or turbomotor.

[0046] This application also relates to a method for manufacturing a blade made of composite material according to one of the features of the invention, the method comprising the following steps: (a) production of at least one fibrous preform intended to form the body of the blade and at least one serration element, (b) shaping and stiffening of at least one fibrous preform in a preforming tool, (c) placement of at least one fibrous preform in a mold, (d) densification of at least one fibrous preform by the resin to form the blade.

[0047] Said serration element is connected to the body by at least one fusible link during step (d).

[0048] The manufacturing process according to the invention makes it easier and more robust to integrate the serration element within the blade and in particular to in a fusible manner. To this end, the invention proposes forming at least one fusible link between the serration element and the blade body during the densification step. The serration element and the blade body are preferably made as a single piece (or in other words, as one continuous unit) of composite material. In addition to the technical advantages mentioned above with reference to the blade, the process according to the invention allows for the automation of all or at least part of the process steps, resulting in significant savings in the cost and manufacturing time of the blade.

[0049] The manufacturing process according to the invention may include one or more of the following features, taken individually or in combination with each other:

[0050] — step (a) is carried out by producing first and second fibrous preforms intended to form, respectively, the body of the blade and at least one serration element,

[0051] — the pins or bars are positioned in the gaps of at least one fibrous preform at step (c);

[0052] - the pins or bars are positioned between the first and second fibrous preforms in step (c);

[0053] - the first and second edges are nested one inside the other by complementarity of form at step (c);

[0054] - the mold includes a cavity intended to receive the first and second fibrous preforms, this impression having at least one groove intended to extend at the level of the thinning, so as to form at least one fusible link at step (d). Brief description of the figures

[0055] 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:

[0056] [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;

[0057] [Fig.2] is a schematic perspective view representing an unfaired propeller turbomachine and an unfaired stator, the propeller and stator each comprising blades;

[0058] [Fig. 3] is a schematic profile view representing a turbine blade of the turbomachine of [Fig. 1] or [Fig. 2], the blade having a serrated element on one edge attack which is connected to a blade body by a fusible link according to a first example;

[0059] [Fig.4] is a schematic profile view representing another turbine blade of [Fig.1] or [Fig.2], the blade comprising a serration element on a trailing edge which is connected to the blade body by a fusible link according to the first example;

[0060] [Fig.5] is a schematic axial and partial cross-sectional view of the blade comprising a fusible link according to a second example;

[0061] [Fig.6] is a partial schematic view of the blade comprising several fusible links according to a third example;

[0062] [Fig.7] is a schematic perspective and partial view of the blade comprising a fusible link according to a fourth example;

[0063] [Fig.8] is a schematic perspective and partial view of the blade comprising a fusible link according to a fifth example;

[0064] [Fig.9] is a schematic axial and partial cross-sectional view of the blade comprising a fusible link according to a sixth example;

[0065] [Fig. 10] is a schematic perspective view of the blade comprising fusible links according to a seventh example;

[0066] [Fig.1 1] is a schematic perspective view enlarged at the level of certain fusible links of the blade of [Fig. 10];

[0067] [Fig. 12] is a schematic axial and enlarged cross-sectional view of a fusible link variant of the blade of [Fig. 11];

[0068] [Fig. 13] is a block diagram of the steps of a manufacturing process for the blade of [Fig.3] or [Fig.4];

[0069] the [Fig. 14] schematically represents in perspective the first and second fibrous preforms intended to form the blade body and the serration element, and their assemblies;

[0070] [Fig.15] is a schematic perspective and partial view of a mold allowing densification of the first and second fibrous preforms;

[0071] [Fig. 16] is a schematic perspective view of the first fibrous preform positioned in the mold of [Fig. 15];

[0072] [Fig. 17] is a schematic perspective view of the second fibrous preform positioned in the mold of [Fig. 16];

[0073] [Fig. 18] is a schematic perspective and partial view of another mold having grooves;

[0074] [Fig. 19] is a schematic perspective view enlarged at the level of the grooves of the mold of [Fig. 18]

[0075] [Fig.20] is a schematic perspective view of the first and second fibrous preforms positioned in the mold of [Fig. 18];

[0076] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0077] 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.

[0078] 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.

[0079] The turbomachine 10 can extend around a longitudinal axis X.

[0080] The turbomachine 10 can conventionally comprise a gas generator that drives at least one propeller 1. The gas generator comprises 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 rotor of the propeller for its rotational drive.

[0081] A propeller 1 can be shrouded. This is the case of a fan in a turbomachine of the turbojet or turbofan type for example.

[0082] By way of example and not limiting, [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 blower), 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]).

[0083] A propeller 1 may be unfaired ([Fig.2]). This is the case for a turboprop engine, for example.

[0084] By way of example and without limitation, [Fig.2] illustrates such a turbomachine 10 comprising the unfaired propeller 1.

[0085] The turbomachine 10 can therefore include the propeller 1 (whether shrouded or unshrouded) upstream and a rectifier 3 downstream.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] Dawn 7 can extend as follows: - an elongation axis A (approximately vertical in Figures 3 and 4) which is substantially perpendicular or inclined to the X axis of the turbomachine 10,

[0090] - a longitudinal axis B (approximately 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. The blade 7 comprises a blade 70 which can be connected to a blade foot 76. The blade 70 comprises a body 79. This body 79 comprises 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.

[0091] The leading edge 73 of the body 79 can correspond to (or in other words can form) a leading edge of the blade 70. The trailing edge 74 of the body 79 can correspond to (or in other words can form) a trailing edge of the blade 70.

[0092] 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 the trailing edge 74.

[0093] 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.

[0094] 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 X axis. The second end is free and configured to form a vertex 75 (or a head) of blade 7.

[0095] The blade 70 may have a first thickness E70 measured along a plane parallel to the axis C.

[0096] The blade 70 also includes at least one serration element 8 extending along 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.

[0097] 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.

[0098] The serration element 8 may include teeth 82 (or, in other words, undulations or protruding portions). In particular, the serration element 8 is formed of a succession of teeth 82 and recesses 84. Preferably, each recess 84 may extend between two teeth 82. 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 along 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 so as to reduce noise in the mid-range emission spectrum without significantly worsening other frequencies at other engine speeds.

[0099] The teeth 82 may have identical shapes to each other or different shapes from each other.

[0100] The teeth 82 can each have a general polygonal shape (such as triangular, rectangular, etc.).

[0101] The ripples may have a profile obeying a periodic law, for example, a sinusoidal type. For example, the ripples may be in the form of a periodic signal having one or more harmonics.

[0102] The teeth 82 can be distributed more or less regularly along the leading edge 73 and / or the trailing edge 74.

[0103] 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.

[0104] The blade 7 is made of composite material. In particular, the blade 70 (and consequently the blade 7) may comprise at least one fibrous preform which may be embedded (or otherwise densified) in a resin (or otherwise a polymer 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] One of the features of the invention is that the serration element 8 is connected to the body 79 of the blade by at least one fusible link 78 which is configured to break when a force applied to this serration element 8 exceeds a predetermined threshold.

[0108] Advantageously, the body 79 can be formed from a first fibrous preform 702 embedded in a resin, the serration element 8 can be formed from at least a second fibrous preform 704 embedded in a resin.

[0109] The resin of the body 79 may be identical or different from the resin of the serration element 8.

[0110] The serration element 8 can be formed of at least one or more second fibrous preform(s) 704 embedded in the resin.

[0111] The first fibrous preform 702 and / or the second fibrous preform 704 can (or can) be formed of woven fibers, for example in two dimensions or in three dimensions.

[0112] The first fibrous preform 702 and / or the second fibrous preform 704 may (or may) comprise carbon fibers, glass fibers, aramid fibers, ceramic fibers (such as silicon carbide) or a mixture of at least two of these fibers.

[0113] The first fibrous preform 702 and / or the second fibrous preform 704 may be pre-impregnated with the resin (for example, before a densification step (d) described below). Alternatively, the first fibrous preform 702 and / or the second fibrous preform 704 may be said to be "dry," that is, they are not pre-impregnated with resin.

[0114] The first and second fibrous preforms 702, 704 can be formed separately and then assembled together to form the serration element 8 connected to the body 79 of the blade 70 by the fusible link 78 (Figures 5 to 9). Alternatively, the first and second fibrous preforms 702, 704 can be formed in one piece, i.e. from a single piece of material, and in particular in one continuous piece (Figures 10 to 12).

[0115] The resin of the first fibrous preform 702 and / or the second fibrous preform 704 may be thermosetting or thermoplastic. For example, the resin may be based on epoxy (such as PR520 epoxy), polyepoxide, polyimide, polybismaleimide, polyurethane, polyester, or vinyl ester.

[0116] The fusible link(s) 78 may (or can) be located on the leading edge side 73 ([Fig.3]) and / or the trailing edge side 74 ([Fig.4]).

[0117] Preferably, one or more sides of the blade 70 formed by the broken fusible link(s) 78 can (or can) correspond to the leading edge 73 and / or trailing edge 74 of the body 79 (and preferably of the blade 70). Thus, when the serration element 8 separates from the body 79 (and in particular from the blade 70), the leading edge 73 and / or the trailing edge 74 can (or can) be that (or those) of the blade 70. The fusible link(s) 78 can (or can) extend at least partially along the leading edge 73 and / or trailing edge 74. The fusible link(s) 78 can (or can) extend at least partially along the axis A and / or at least partially along the axis B.

[0118] The fusible link(s) 78 may (or may) have a second thickness E78 measured along a plane parallel to the axis C. This second thickness may be identical (figures 5 to 9) or less (figures 10 to 12) than the first thickness E70.

[0119] The present application will now describe the different possible configurations of the fuse link 78 of the blade 7 (described above), with reference to the non-limiting examples in Figures 3 to 12.

[0120] At least two of the examples described below with reference to the fusible link 78, can be combined with each other.

[0121] According to a first example, the fusible link(s) 78 may (or may) include a first line 781 of fusible link which extends at least partly along the leading edge 73 and / or trailing edge 74.

[0122] Preferably, this fusible link 78 can extend along the axis A. This first line 781 extends between this axis A and the leading edge 73 and / or trailing edge 74.

[0123] The first fusible link line 781 can extend partially (Figures 4, 6 and 10) or entirely ([Fig.3]) along axis A.

[0124] The first line 781 can be located at least partly on the intrados 71 and / or at least partly on the extrados 72.

[0125] The first line 781 can extend in a straight line (for example along axis A) or curved.

[0126] The first line 781 may have a length, measured along axis A, that corresponds to at least 50% of the total length of the blade 7. The total length of the blade 7 is measured, in particular, from the foot 76 to the apex 75 along axis A. This length of the first line 781 may be between 50% and 100% of the total length of the blade 7. With reference to [Fig. 4], the length of the first line 781 may be between 70% and 80% of the total length of the blade 7.

[0127] The first line 781 may have a first width measured along axis B, which may be less than 15 mm. Preferably, the first width of the first line 781 may be between 1 and 10 mm.

[0128] According to a second example, at least one fusible link 78 may further comprise second lines 783 of fusible link which extend between the first line 781 and the leading edge 73 and / or trailing edge 74. This makes it possible to form several fusible links 78 and thus facilitate the repeatability and / or replacement of the serration element(s) 8 which have been broken, and thus to preserve the major part of the blade 7 (such as the blade body 79).

[0129] The second lines 783 can each be located at least partly on the intrados 71 and / or at least partly on the extrados 72.

[0130] The second lines 783 can each extend in a straight line (for example along a plane parallel to axis B) or curved.

[0131] The [Fig.6] illustrates, non-limitingly and partially, the vane 7 comprising both the first line 781 and second lines 783 which extend between this first line 781 and the trailing edge 74.

[0132] The second lines 783 can extend substantially perpendicularly (i.e. along axis B) and / or inclinedly with respect to axis A.

[0133] At least some of the second 783 fusible link lines can be parallel to each other.

[0134] By way of example, the second lines can number from two to twenty. In [Fig.6], approximately six second lines 783 are located at the trailing edge 74.

[0135] According to a third example, the fusible link(s) 78 can be made with a resin 780. This resin 780 can, for example, be epoxy. The resin 780 allows the serration element 8 to be bonded to the blade body 79. This resin 780 can be more brittle and / or more ductile compared to the rest of the blade 7 (such as the blade body 79 and the serration element 8), which is formed by at least one fibrous preform. This allows the fusible link 78 made of resin 780 to break first when a force applied to the serration element 8 exceeds the predetermined threshold.

[0136] In particular, the first line 781 and / or the second lines 783 can (or may) be made with resin 780.

[0137] [Fig.5] illustrates in a non-limiting way the first line 781 of fusible bonding made with resin 780. The first 781 and the second 783 lines of [Fig.6] can be made with resin 780.

[0138] The resin 780 can be identical to the resin of the first and second fibrous preform 702, 704.

[0139] According to a fourth example, the fusible link(s) 78 can be made from short fibers 782 embedded in the resin 780, these short fibers 782 having a length of 20 mm or less. These short fibers 782 make the fusible link 78 less brittle. Preferably, the length of the short fibers 782 can be between 2 and 15 mm. Even more preferably, the length of the short fibers 782 can be between 3 and 12 mm. Advantageously, the length of the short fibers 782 can be about 6 mm.

[0140] Fig. 7 illustrates, non-limitingly and partially, the short fibers 782 embedded in the resin of the fusible bond 78.

[0141] The short fibers 782 may have a titration (or otherwise said "titration") of between 10 and 100 K. Preferably, the titration of the short fibers 782 may be between 12 and 96 K.

[0142] The term "count" refers to the number of short fiber filaments, expressed in thousands of deniers (K). For example, a count of 96 K for carbon or glass fibers corresponds to 96,000 individual carbon or glass filaments (or strands).

[0143] These short 782 fibers having a caliber between 12 and 96 K can be cut to lengths between 3 and 12 mm.

[0144] The short 782 fibers can be made of carbon or glass.

[0145] According to a fifth example, the fusible link(s) 78 may (or may) include pins or strips 784 delimiting between them gaps 786 filled by the resin 780. The pins or strips 784 make it possible in particular to control a predefined spacing between the first and second fibrous preforms 702, 704 at the level of the fusible link 78.

[0146] The pins or bars 784 can be located at the level of the first line 781 and / or the second lines 783 of fusible link.

[0147] The pins or bars 784 can be made of resin, preferably similar or of the same nature (i.e. having at least one of the same chemical properties) as the resin 780 of the fusible link 78. Even more preferably, the pins or bars 784 can be made of epoxy.

[0148] The pins or bars 784 may each have a second width measured along axis B, which may be less than 15 mm. Preferably, the second width of the pins or bars 784 may be between 1 and 10 mm. This second width may correspond to a width of the fusible link 78, in particular the first line 781 of the fusible link. The second width of the pins or bars 784 may thus be identical to the first width of the first line 781 of the fusible link.

[0149] According to a sixth example, the fusible link(s) 78 may (or may be) comprised (or formed) by a first edge 740 of the body 79 (in particular of the first fibrous preform 702 of the body 79) which is fitted by complementary shape into a second edge 840 of the serration element 8 (in particular of the second fibrous preform 704 of this serration element 8). This notably allows for a more complex fusible link for improved mechanical strength and repairability.

[0150] Figure 9 illustrates, without limitation, that the first edge 740 may include at least one projecting portion which engages by complementary shape in at least one hollowed portion of the second edge 840. Alternatively, the second edge 840 may include at least one projecting portion which engages by complementary shape in at least one hollowed portion of the first edge 740.

[0151] The first and second edges 740, 840 fitting together, can be located at the level of the first line 781 and / or the second lines 783 of fusible link.

[0152] The first and second edges 740, 840 can also be bonded together by a resin. This resin can be similar to that of the fusible link 78 and / or the first and second fibrous preforms 702, 704.

[0153] The first edge 740 and the second edge 840 can be opposite the edges intended to form the leading edges 73 and trailing edges 74.

[0154] The second fibrous preform 704 may include a third edge 800 which is opposite the second edge 840. This third edge 800 may be corrugated and intended to form the teeth 82 and the hollows 84 of the serration element 8.

[0155] According to a seventh example, the fusible link(s) 78 can be formed by a thinning 788 of the blade 70. This makes it possible to strengthen the mechanical strength, while reducing the mass of the blade 7. Furthermore, the thinning 788 makes it possible in particular to form the fusible link 78 directly within a single fibrous preform 702, 704. In this configuration, the first and second fibrous preforms 702, 704 can be formed in one piece.

[0156] The second thickness E78 at the thinning 788 may be less than the first thickness E70 of the blade 70 (in particular of the body 79 and / or the serration element 8). For example, the second thickness E78 may correspond at most to 80% of the first thickness E70. Preferably, the second thickness E78 can be between 30 and 80% of the first thickness E70.

[0157] The thinning 788 can thus form a groove. This groove may have a cross-section smaller than that of the rest of the blade (such as the body 79 and / or the serration element 8).

[0158] The thinning 788 can be annular ([Fig. 11]) or triangular in cross-section ([Fig. 12]). The triangular shape makes it easier to produce the first and second fibrous preforms 702, 704 by weaving.

[0159] The thinning 788 can be located at the level of the first line 781 and / or the second lines 783 of fusible link.

[0160] The thinned portion at the thinning level 788 may have a volumetric ratio of TVF fibers which may vary (in particular with respect to the body 79 and / or the serration element 8) depending, for example, on the desired predetermined threshold.

[0161] A silicone seal, for example (such as an RTV type seal, an English acronym for "Room Temperature Vulcanizing Silicone") can cover the portion thinned by the thinning 788 to form a continuous aerodynamic surface with the body 79 and the serration element 8.

[0162] The present application will now describe a method for manufacturing the blade 7 comprising the fusible link 78 as described above with reference to Figures 3 to 12.

[0163] Fig. 13 summarizes the successive steps of the manufacturing process of the blade 7 in composite material, and the optional steps are represented in dotted lines.

[0164] According to the invention, the method comprises the following steps: (a) production of at least one fibrous preform 702, 704 intended to form the body 79 of the blade 70 and at least one serration element 8, (b) shaping and stiffening of at least one fibrous preform 702, 704 in a preforming tool, (c) placing at least one fibrous preform 702, 704 in a mold M, and (d) densification of at least one fibrous preform 702, 704 by resin 780 to form the blade 7.

[0165] The serration element 8 is connected to the body 79 by at least one fusible link 78 during step (d).

[0166] In step (a), the at least one fibrous preform 702, 704 may comprise the first fibrous preform 702 and at least one or more second fibrous preform(s) 704.

[0167] The first fibrous preform 702 and / or the second fibrous preform 704 can (or can) be formed by weaving fibers, for example in two dimensions or in three dimensions.

[0168] The first fibrous preform 702 can be intended to form the body 79 comprising the leading edge 73, the trailing edge 74, the lower surface 71 and the upper surface 72 of the blade 70.

[0169] As illustrated by way of example in [Fig. 14], step (a) can separately produce two fibrous preforms, respectively, the first 702 and the second 704 (particularly in the case of the third to sixth examples). Alternatively, step (a) can produce a single fibrous preform corresponding to the first 702 and second 704 fibrous preforms formed in one piece (particularly in the case of the seventh example in Figures 10 to 12).

[0170] Step (a) may also include pre-cutting, for example manually, any loose fibers (such as warp yarn fibers) on the first fibrous preform 702 and / or the second fibrous preform 704 obtained after weaving fibers.

[0171] Step (b) enables preforming of the fibrous preform (in particular the first and second fibrous preforms 702, 704) obtained at the end of step (a). This step (b) can be carried out in suitable preforming tooling (not shown in the figures).

[0172] Step (b) may include a substep (bi) of applying water to the fibrous preform (in particular the first fibrous preform 702 and / or the second fibrous preform 704) obtained, for example, at the end of step (a). This allows the fibrous preform 702, 704 to be wetted. The fibrous preform 702, 704 is thus moistened with water, making it easier to handle.

[0173] Step (b) may include a substep (b2) of positioning the fibrous preform (in particular the first and second fibrous preforms 702, 704) obtained in step (a) or (b1) in the corresponding preforming tool. For this purpose, the fibrous preform 702, 704 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 tool.

[0174] 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 several hours. Drying allows, in particular, the water used for wetting to be dried and extracted from the fibrous preform.

[0175] In step (c), the fibrous preform (in particular the first and second fibrous preforms 702, 704), notably obtained at the end of step (b), can be placed in a mold M adapted. This step (c) is shown in a non-limiting way in figures 14 to 20.

[0176] With reference to Figures 15 and 18, the mold M may include geometries of the serration element 8, such that the second densified (or resin-embedded) fibrous preform 704 is 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] annotated in [Fig. 15]) and / or camber of the blade 7 and the serration element 8.

[0177] The angle

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

[0178] Advantageously, the mold M can include a cavity M70 for receiving the fibrous preform 702, 704. This cavity can include a first part M702 having a shape complementary to the first fibrous preform 702, and a second part M704 having a shape complementary to the second fibrous preform 704. This makes it easier to position the first and second fibrous preforms 702, 704 and subsequently the densification step (d) in this mold M.

[0179] The M70 imprint may include at least one groove M788 intended to extend at the thinning 788 so as to form the fusible link 78 at step (d).

[0180] Following the example of Figures 18 and 19 and without limitation, the mold M may have several grooves 788 allowing the formation of the first line 781 and the second lines 783 of fusible link as illustrated in Figures 10 to 12.

[0181] Figures 15 and 17 illustrate a first embodiment of step (c). In step (c) of the first embodiment, the first fibrous preform 702 can be placed before the second fibrous preform 704 in the mold M.

[0182] Preferably, the second fibrous preform 704 can be positioned at least a predetermined distance from the first fibrous preform 702, so as to form the fusible link 78 between these fibrous preforms 702, 704 in step (d). This predetermined distance can correspond to the predetermined spacing between the first and second fibrous preforms 702, 704.

[0183] The at least one predefined distance between the first and second fibrous preforms 702, 704 can correspond to the dimensions of the first line 781 and / or the second 783 fusible links.

[0184] The predefined distance between the first and second fibrous preforms 702, 704 can be filled by the resin 780.

[0185] With reference to the fourth example of a fusible link 78 described above, short fibers 782 can be arranged and interleaved between the first and second fibrous preforms 702, 704.

[0186] With reference to the fifth example described above, the pins or strips 784 can be positioned in the gaps 786 of the fibrous preform 702, 704 in step (c). This ensures the repeatability of the positioning of the fibrous preforms 702, 704, by creating the gaps 786 filled by the resin 780, particularly in step (d). More specifically, the pins or strips 784 can be positioned between the first and second fibrous preforms 702, 704 in step (c), particularly in this first embodiment.

[0187] With reference to the sixth example described above, the first and second edges 720, 740 of the fibrous preforms 702, 704 can be fitted together by complementarity of shape in step (c), in particular of this first embodiment.

[0188] Figures 18 to 20 illustrate a second embodiment of step (c). In step (c) of the second embodiment, the first and second fibrous preforms 702, 704 can be positioned so that the groove M788 extends at the level of the thinning 788.

[0189] The positioning of the fibrous preforms 702, 704 in the mold M (regardless of the embodiment of step (c)) can also be carried out using the fiber tracers on the surface of these fibrous preforms 702, 704 and their laser projections.

[0190] The densification step (d) allows polymerization or hardening of the fibrous preform (in particular of the first and second fibrous preforms 702, 704), in particular of the resin 780 in polymer matrix so as to form the blade 7 in composite material.

[0191] In particular, the first and second fibrous preforms 702, 704 can be linked together in step (d), so as to form at least one fusible link 78.

[0192] The resin 780 can be injected at this stage (d) to fill the predetermined distance and / or the gaps 786 between the fibrous preforms 702, 704 and thus form the fusible link 78, and optionally to impregnate the fibrous preforms 702, 704. Then, the assembly can be heated to densify and form the blade 7 comprising the fusible link 78 connecting the serration element 8 to the body 79 of the blade 70.

[0193] The heating in step (a) can be carried out at a temperature between 150°C and 200°C, preferably about 180°C, and preferably under pressure.

[0194] As mentioned above, the 780 resin can be epoxy, for example of type PR520.

[0195] The method may include a final finishing step (e) of the blade 7. By way of example, step (e) may include machining on the contour of the blade 7 obtained in step (d) to remove excess length. The excess length removed can be between 10 and 30 mm.

Claims

Demands

1. A blade (7) made of composite material for a turbomachine (10), in particular for aircraft, the blade (7) comprising a blade (70) formed by at least one fibrous preform (702, 704) embedded in a resin and extending along an elongation axis (A), the blade (70) comprising a body (79) having a leading edge (73), a trailing edge (74), an intrados (71) and an extrados (72) connected to the intrados (71) by the leading edge (73) and the trailing edge (74), the blade (70) further comprising at least one serration element (8) formed of a succession of teeth (82) and grooves (84) extending along at least a portion of the leading edge (73) and / or the trailing edge (74), characterized in that said at least one serration element (8) is connected to the body (79) by at least one fusible link (78) configured to break when a force applied to said at least one serration element (8) exceeds a predetermined threshold.

2. Blade made of composite material according to claim 1, characterized in that at least one fusible link (78) comprises a first line (781) of fusible link which extends at least in part along the leading edge (73) and / or trailing edge (74).

3. Blade made of composite material according to claim 2, characterized in that at least one fusible link (78) further comprises second lines (783) of fusible link extending between the first line (781) of fusible link and the leading edge (73) and / or trailing edge (74).

4. Blade made of composite material according to any one of claims 1 to 3, characterized in that the body (79) is formed of a first fibrous preform (702) embedded in a resin, and said at least one serration element (8) is formed of at least a second fibrous preform (704) embedded in a resin.

5. Blade made of composite material according to any one of claims 1 to 4, characterized in that at least one fusible link (78) is made with a resin (780), for example epoxy.

6. A blade made of composite material according to claim 5, characterized in that at least one fusible link (78) is made from short fibers (782) embedded in the resin (780), the short fibers having a length less than or equal to 20 mm, preferably the length is between 2 and 15 mm.

7. Blade made of composite material according to claim 5 or 6, characterized in that at least one fusible link (78) comprises pins or bars (784) delimiting between them gaps (786) filled by the resin (780).

8. Blade made of composite material according to any one of claims 1 to 4, characterized in that at least one fusible link (78) is formed by a first edge (720) of the body (79) which is fitted by complementarity of form into a second edge (840) of said at least one serration element (8).

9. Blade made of composite material according to any one of claims 1 to 4, characterized in that at least one fusible link (78) is formed by a thinning (788) of thickness (E78) of the blade (70).

10. Blade made of composite material according to claim 9, characterized in that the first and second fibrous preforms (702, 704) are formed in one piece.

11. A method for manufacturing a blade (7) made of composite material according to any one of the preceding claims, the method comprising the following steps of: (a) producing at least one fibrous preform (702, 704) intended to form the body (79) of the blade (70) and at least one serration element (8), (b) shaping and stiffening the at least one fibrous preform (702, 704) in a preforming tool, (c) placing the at least one fibrous preform (702, 704) in a mold (M), and (d) densifying the at least one fibrous preform (702, 704) with resin (780) to form the blade (7), characterized in that said at least one serration element (8) is connected to the body (79) by at least one fusible link (78) during the step (d).

12. A manufacturing method according to claim 11 in combination with claims 4 and 7, characterized in that the pins or bars (784) are positioned between the first and second fibrous preforms (702, 704) in step (c).

13. A manufacturing method according to claim 11 in combination with claim 8, characterized in that the first and second edges (740, 840) are nested one inside the other by complementarity of form at step (c).

14. A manufacturing method according to claim 11 in combination with claim 9 or 10, characterized in that the mold (M) comprises a cavity (M70) intended to receive at least one fibrous preform (702, 704), this cavity (M70) having at least one groove (M788) intended to extend at the level of the thinning (788), so as to form at least one fusible link (78) at step (d).

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