Blade having composite structure with improved ply decline orientation

Abstract

The disclosed fan blade is at least partially composed of a structure (50) made from a composite material, the structure comprising a fibrous reinforcement (62) and a matrix (64). The fibrous reinforcement (62) includes a plurality of plies (66, 68), each of which is formed of warp yarns (71) and weft yarns (72). The warp yarns (71) and the weft yarns (72) comprise incomplete yarns (75, 76), each having an end (78) on the pressure side (40) or the suction side (42). The pressure side (40) and the suction side (42) each have at least one ply decline that connects the ends (78) of the incomplete yarns (75, 76) of the same ply (66, 68). In the lower region of the blade and / or in the extension region of the blade, the number of ply-down lines on the pressure side (40) is greater than the number of ply-down lines on the suction side (42).

Description

Technical Field

[0001] The present invention relates to a blade for a turbine fan of the following type, the blade of this type comprises a root configured to be inserted into a groove of a fan disk, a blade body capable of extending in an air flow and defining a blade head opposite to the root, and a support connecting the root to the blade body, the blade having a pressure side, a suction side, a leading edge and a trailing edge, the blade extending in a longitudinal direction extending from the root to the blade head, the longitudinal direction being substantially perpendicular to a chord direction extending from the leading edge to the trailing edge, the blade at least partially consisting of a structure made of a composite material, the structure comprising a fiber reinforcement obtained by three-dimensional weaving and a matrix, the fiber reinforcement being embedded in the matrix, the fiber reinforcement comprising a plurality of interwoven plies, each ply being formed by a warp yarn extending substantially perpendicular to the chord direction and a weft yarn extending substantially perpendicular to the longitudinal direction, the warp yarn and the weft yarn comprising incomplete yarns, the incomplete yarns each having an end on the pressure side or the suction side, the pressure side and the suction side each having at least one ply reduction line, the at least one ply reduction line connecting the ends of the incomplete yarns of the same ply.

[0002] The invention also relates to a turbomachine fan comprising a plurality of blades of the above-described type, to a turbomachine comprising such a fan, and to an aircraft comprising such a turbomachine. Background Art

[0003] Turbine blades, in particular fan blades, are subject to significant mechanical and thermal stresses and must meet stringent weight and size requirements. It has therefore been proposed to use blades consisting at least partially of a composite structure comprising a fiber reinforcement densified by a polymer matrix, which are lighter than metal blades with equivalent propulsion characteristics and have satisfactory thermal resistance.

[0004] Such a blade is known from EP 1 526285, for example.

[0005] Most commonly, the thickness of the blade decreases from the pillar to the blade head. The blade also thins towards the leading edge and the trailing edge. In order to obtain such a reduced thickness for a blade consisting of a composite material structure, the number of plies constituting the structure generally decreases as the blade head, the leading edge and the trailing edge are approached. For this purpose, the yarns forming these plies are removed from the structure and interrupted along a ply reduction line on the pressure side or the suction side, as described, for example, in EP 3292991.

[0006] During the life of the engine, fan blades are subject to impacts from birds and hail. Therefore, certification rules for aircraft engines logically require fan blades to have a certain resistance to this type of impact. However, composite blades tend not to resist such impacts the same way as their metallic equivalents. Therefore, to meet certification rules, composite blades are often thicker, which can make the design more complex in order to manage the aerodynamic performance of the blade and can partially offset the weight savings from using composite materials.

[0007] Solutions have been proposed, for example, in EP 3292991, WO 2020 / 089345 and FR 3087711 to solve this type of problem and improve the mechanical performance of composite structure blades facing such impacts. These solutions may be satisfactory, but they also need to be optimized. Summary of the invention

[0008] The object of the present invention is to improve the mechanical properties of a blade having a composite structure when struck by birds or hail.

[0009] To this end, according to a first aspect, the invention relates to a blade for a turbine fan of the type described above, wherein in a lower region of the blade between the root and 30% of the blade height, and / or in an extension region of the blade between the root and 70% of this height, the number of ply reduction lines on the pressure side is greater than the number of ply reduction lines on the suction side.

[0010] According to a particular embodiment of the invention, the blade also has one or more of the following features alone or in any technically possible combination:

[0011] - over the entire blade, the number of ply reduction lines on the pressure side is greater than the number of ply reduction lines on the suction side;

[0012] - at least one ply reduction line comprises at least one transverse portion located between the root and 70% of the blade height, the transverse portion comprising a tip portion, the or each transverse portion extending substantially along a transverse direction substantially perpendicular to a local tangent to the warp yarns, the or each tip portion extending over at most 10% of the distance between the leading edge and the trailing edge measured parallel to the transverse direction;

[0013] - the or each transverse portion situated between the root and 70% of the blade height extends over at most 10% of the distance between the leading edge and the trailing edge measured parallel to the transverse direction;

[0014] at least one ply reduction line comprises an end portion extending from the blade head to 90% of the blade height, advantageously to 60% of the blade height, the or each end portion extending substantially along an extension direction making an angle of between 5° and 85° with a local tangent to the warp yarns;

[0015] - for the or each end portion, the direction of extension forms an angle of between 5° and 85° with a local tangent to the weft yarn;

[0016] at least one end portion consists of an inclined end portion, the extension direction of which forms an angle of between 10° and 65°, advantageously between 15° and 45° with a local tangent to the warp yarn;

[0017] - for the or each inclined end portion, the direction of extension forms an angle with a local tangent to the weft yarn of between 25° and 80°, advantageously between 45° and 75°;

[0018] - most of the terminal portion consists of an inclined terminal portion;

[0019] - the blade comprises an additional shroud covering the composite structure along the leading edge, the shroud having a downstream edge on the pressure side and a downstream edge on the suction side, the or each end portion on the pressure side meeting at each point of said end portion on the pressure side at least one of the following criteria:

[0020] the terminal portion is spaced apart from the downstream edge on the pressure side by a distance greater than or equal to three times the mesh width of the fiber reinforcement, and

[0021] a tangent to the terminal portion forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with a tangent to the downstream edge on the pressure side at the height of said point,

[0022] The or each end portion on the suction side satisfies at least one of the following criteria at each point of the end portion on the suction side:

[0023] - the terminal portion is spaced apart from the downstream edge on the suction side by a distance greater than or equal to three times the mesh width of the fiber reinforcement, and

[0024] A tangent to the terminal portion forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with a tangent to the downstream edge on the suction side at the height of said point.

[0025] According to a second aspect, the invention also relates to a turbomachine fan comprising a plurality of blades as defined above.

[0026] According to a third aspect, the invention also relates to a turbomachine comprising such a fan.

[0027] Finally, according to a fourth aspect, the invention relates to an aircraft comprising such a turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features and advantages of the invention will emerge on reading the following description given by way of example only and with reference to the accompanying drawings, in which:

[0029] - Figure 1 is a top view of an aircraft according to an exemplary embodiment of the present invention,

[0030] - Figure 2 yes Figure 1 A three-quarter front perspective view of the aircraft's turbine.

[0031] - Figure 3 yes Figure 2 Side view of a turbine fan blade,

[0032] - Figure 4 It is along Figure 3 A simplified cross-sectional view of the plane marked IV-IV in FIG.

[0033] - Figure 5 yes Figure 3 A three-quarter frontal perspective view of the composite structure of the blade.

[0034] - Figure 6 yes Figure 5 Three-quarter rear perspective view of the composite structure.

[0035] - Figure 7 Is part of the composite structure along Figure 6 A simplified cross-sectional view of the plane marked VII-VII in FIG.

[0036] - Figure 8 yes Figure 4 A view of the detail marked VIII, and

[0037] - Fig. 9 yes Figure 7 View of the detail marked IX. DETAILED DESCRIPTION

[0038] Figure 1 The illustrated aircraft 10 includes a turbine 12 for propelling it.

[0039] In the example shown, the aircraft 10 is an airplane. In conventional manner, the airplane comprises a fuselage 14, a horizontal tail 16 and two wings 18. Here, there are two turbines 12, each housed under a respective wing 18. As a variant (not shown), the turbines 12 are arranged along the fuselage 14, for example close to the horizontal tail 16. As another variant (also not shown), the aircraft 10 comprises a single turbine 12 or at least three turbines 12.

[0040] Figure 2 1 shows one of the turbomachines 12. As can be seen from this figure, the turbomachine comprises a nacelle 20 for fixing to the wing 18 or fuselage 14 of the aircraft 10, a fan 22 and a cowling 24 surrounding the fan 22. In a conventional manner, the turbomachine also comprises a compressor, a combustion chamber and a turbine (not shown), the turbine being mechanically connected to the fan 22 so as to rotate the fan about its axis.

[0041] The turbomachine 12 is typically a twin-flow turbojet engine, advantageously with a high bypass ratio.

[0042] The fairing 24 defines an air flow path. The fairing is fixedly mounted on the nacelle 20. In the example shown, the fairing is arranged inside the nacelle 20. As a variant (not shown), the turbine 12 has no fairing.

[0043] The fan 22 comprises a fan rotor 26 which can be driven in rotation relative to the nacelle 20 about an axis of rotation X which here coincides with the main axis of the turbine 12. The fan rotor 26 comprises a hub 28, generally referred to as a "fan disk", and a plurality of blades 30 fixed to the hub 28 and extending in a substantially radial direction from the hub 28. In the example shown, the blades 30 are all identical and are arranged with a constant angular spacing between two consecutive blades 30.

[0044] Figure 3 One of the blades 30 is schematically shown. The blade 30 comprises a root 32, an airfoil 34 having an aerodynamic profile, and a strut 36.

[0045] The root portion 32 is used to enable the blade 30 to be fixed to the hub 28, for example, by means of a pin fastener (not shown). To this end, the root portion 32 is configured to be inserted into a groove (not shown) of the hub 28.

[0046] In the example shown, the root 32 is dovetail-shaped. As a variant (not shown), the root 32 has any shape suitable for assembling the blade 30 on the hub 28 .

[0047] The blade airfoil 34 is adapted to be placed in an air flow when the turbine 12 is in operation so as to generate lift. At its end opposite the root 32 , the blade airfoil defines a blade head 38 .

[0048] The blade airfoil 34 also has a pressure side 40 ( Figure 4 ), suction side 42 , leading edge 44 and trailing edge 46 .

[0049] The blade airfoil 34 also has a blade head edge 47 constituted by the free edge of the blade 30 which is furthest from the root 32. The blade head edge 47 can extend along the inner surface of the spinner 24 surrounding the fan.

[0050] The strut 36 corresponds to the region of the blade 30 extending between the root 32 and the airfoil 34, that is, between the exit of the bearing surface 48 and an inter-blade platform (not shown) which internally delimits a secondary flow path. The strut 36 is therefore not configured to extend into the air flow.

[0051] The blade 30 is elongated along a longitudinal axis Y that is perpendicular to the axis X and extends from the root 32 to the head 38. The longitudinal axis Y is also perpendicular to the chord direction C ( Figure 4 ).

[0052] Here and hereinafter, the term "blade height" refers to the distance measured between a point on the blade 30 and the departure from the bearing surface 48 along the axis Y. This distance is usually expressed in a dimensionless manner as a percentage of the distance from the head edge 47 to the departure from the bearing surface 48.

[0053] As in Figure 4 As seen in FIG. 4 , the blade 30 has a blade core 49 where the thickness of the blade 30 in the chord direction C is greatest. In other words, the thickness of the blade 30 decreases from the blade core 49 toward each of the leading edge 44 and the trailing edge 46. In particular, the blade core 49 is centered on the longitudinal axis Y.

[0054] In the example shown, the blade 30 is twisted about the blade core 49 so that the chord C pivots about the longitudinal axis Y according to the blade height.

[0055] refer to Figure 4 Here, the blade 30 is composed of a structure 50 made of a composite material. Figure 5 and Figure 6 , the structure 50 here extends from the root 32 to the head 38 along the longitudinal axis Y, from the leading edge 44 to the trailing edge 46 along the chord direction C, and from the pressure side 40 to the suction side 42 along the thickness of the blade 30. In particular, the structure 50 substantially matches the shape of the blade 30. Optionally, the structure 50 at least partially defines the outer surface of the blade 30.

[0056] Due to this shape proximity between the blade 30 and the structure 50, the same terms will be used here and below to refer to the surface areas of the blade 30 and the elements of the structure 50 associated therewith. Thus, the term "pressure side 40" refers to both the pressure side of the blade 30 itself and the surface of the structure 50 on the side of the pressure side, even if the surface does not directly define the pressure side of the blade 30 (i.e., even if the surface of the structure 50 on the side of the pressure side is covered by another element). Similarly, the term "suction side 42" refers to both the suction side of the blade 30 itself and the surface of the structure 50 on the side of the suction side, even if the surface does not directly define the suction side of the blade 30 (i.e., even if the surface of the structure 50 on the side of the suction side is covered by another element.

[0057] The structure 50 is often referred to as the “body” of the blade 30 .

[0058] Still refer to Figure 4 Here, too, the blade 30 is constituted by an additional shroud 52 covering the composite structure 50 along the leading edge 44. This shroud 52 is formed by two fins 54, 55 connected together at the top end 56 of the shroud 52. The first fin 54, arranged on the side of the pressure side 40, defines a downstream edge 57 of the shroud 52 on the pressure side. The second fin 55, arranged on the side of the suction side 42, defines a downstream edge 58 of the shroud 52 on the suction side.

[0059] The two fins 54 , 55 define between them a cavity 59 in which the upstream end 60 of the structure 50 is housed.

[0060] The shield 52 is typically made of metal foil.

[0061] refer to Figure 7 , the structure 50 includes a fiber reinforcement 62 and a matrix 64 in which the fiber reinforcement 62 is embedded.

[0062] The fiber reinforcement 62 comprises a plurality of interwoven plies 66 , 68 which are stacked along the thickness of the blade 30 , ie in a direction extending from the pressure side 40 to the suction side 42 .

[0063] Each ply 66, 68 is formed of a warp yarn 71 and a weft yarn 72. Each warp yarn 71 extends substantially perpendicularly to the chord direction C from the root 32 to the head 38. Each weft yarn 72 extends substantially perpendicularly to the longitudinal axis Y from the blade core 49 to each of the leading edge 44 and the trailing edge 46.

[0064] The term "substantially perpendicular" means here and hereinafter that the yarns 70, 72 form an angle of between 85° and 95° with the direction or axis in question (here the chord direction C and the longitudinal axis Y, respectively).

[0065] The fiber reinforcement 52 is obtained by three-dimensional weaving, ie at least some of the warp yarns 71 belonging to a ply 66, 68 are combined with weft yarns 72 belonging to the other ply 66, 68. Three-dimensional weaving techniques are described, for example, in WO 2006 / 136755.

[0066] As in Figure 8 As seen in FIG. 1 , the warp yarns 71 are arranged in warp yarn rows 73, each warp yarn row being formed by juxtaposition of warp yarns 71 of different plies 66, 68 along the thickness of the blade 30. Thus, each warp yarn row 73 extends along a surface that is substantially perpendicular to the chord direction C.

[0067] Each warp yarn 71 belongs to a single warp yarn row 73 .

[0068] Each warp yarn row 73 is substantially parallel to its adjacent warp yarn row. In other words, for each blade height, the normal line of each warp yarn row 73 forms an angle less than or equal to 5° with the normal line of each adjacent warp yarn row.

[0069] Figure 7 The view corresponds to a cross section in the warp yarn row 73. Therefore, Figure 7 One of many planes is shown that repeats between the leading edge 44 and the trailing edge 46 along the chord direction C. The other planes are similar to the plane shown except that the warp yarns 71 are offset in the longitudinal direction so that the warp yarns 71 and the weft yarns 72 are connected at different heights depending on the plane.

[0070] As in Fig. 9 As seen in FIG. 1 , the weft yarns 72 are arranged according to weft yarn columns 74, each weft yarn column being formed by juxtaposition of weft yarns 72 of different plies 66, 68 along the thickness of the blade 30. Thus, each weft yarn column 74 extends along a surface substantially perpendicular to the longitudinal axis Y.

[0071] Each weft yarn 72 belongs to a single weft yarn column 74 .

[0072] Each weft yarn column 74 is substantially parallel to its adjacent weft yarn column. In other words, the normal line of each weft yarn column 74 forms an angle of less than or equal to 5° with the normal line of each adjacent weft yarn column.

[0073] Furthermore, each weft yarn row 74 is substantially perpendicular to each warp yarn row 73 , that is, for each weft yarn row 74 -warp yarn row 73 pair, the average normal of the weft yarn row 74 is substantially perpendicular to the average normal of the warp yarn row 73 .

[0074] Return to Figure 7, the plies 66, 68 include at least one complete ply 66, each warp yarn 71 extending from the root 32 to the head 38, each weft yarn 72 extending from the leading edge 44 to the trailing edge 46, and the partial ply 68 includes an incomplete warp yarn 75 and / or an incomplete weft yarn 76. The incomplete warp yarn 75 is composed of the warp yarn 71 interrupted at the surface of the structure 50 before the head 38, so as to be able to reduce the thickness of the blade 30 along the longitudinal axis Y. The incomplete weft yarn 76 is composed of the weft yarn 72 interrupted at the surface of the structure 50 before the leading edge 44 and / or the trailing edge 46, so as to be able to reduce the thickness of the blade 30 along the chord direction C.

[0075] It will be noted that the first yarn 71, 72, although interrupted on the pressure side 40 or the suction side 42, is extended by the second yarn 71, 72, which starts essentially from where the first yarn 71, 72 ends, and the first yarn is not considered to constitute an incomplete yarn 75, 76.

[0076] Each incomplete yarn 75, 76 has at least one end 78 on the pressure side 40 or the suction side 42. The ends 78 of the incomplete yarns 75, 76 of the same ply 68 are spaced apart from each other by a distance which is approximately the mesh width of the fiber reinforcement 62.

[0077] Here and hereinafter, the term “mesh width of the fiber reinforcement 62 ” denotes the average of the average distances between the rows of warp threads 73 on the one hand and the average distances between the rows of weft threads 74 on the other hand.

[0078] For each partial ply 68, the ends 78 of the incomplete yarns 75, 76 that make up it pass through the corresponding ply reduction lines 80, 81, 82, 83 ( Figure 5 and Figure 6 The ply reduction lines 80, 81, 82, 83 are formed by at least a class C ply passing through the pressure side 40 and the suction side 42, respectively. 1 of curves (or a set of two curves, each of which is at least of class C 1 The curve composition).

[0079] Each ply reduction line 80, 81, 82, 83 forms a boundary between two regions of the blade (not given reference numerals): an inner region extending between the ply reduction line 80, 81, 82, 83 and the root 32, and an outer region extending between the ply reduction line 80, 81, 82, 83 and each of the leading edge 44, the trailing edge 46 and the head edge 47. The inner region has at each point a number of yarns 71, 72 stacked along the thickness of the blade 30 that is greater than or equal to a first value. The outer region has at each point a number of yarns 71, 72 stacked along the thickness of the blade 30 that is less than or equal to a second value, the second value being strictly less than the first value. In other words, the number of yarns 71, 72 stacked along the thickness of the blade 30 is less in the outer region than in the inner region.

[0080] Here, in the lower region of the blade 30 extending from the root 32 to 30% of the blade height, the number of ply decreasing lines 80, 81 on the pressure side 40 is greater than the number of ply decreasing lines 82, 83 on the suction side 42. This numerical advantage of the ply decreasing lines 80, 81 on the pressure side 40 relative to the ply decreasing lines 82, 83 on the suction side 42 can still be observed in the region of the blade 30 extending from the root 32 to 70% of the blade height and even over the entire blade 30. As a variant (not shown), the numerical advantage of the ply decrement lines 80, 81 on the pressure side 40 relative to the ply decrement lines 82, 83 on the suction side 42 is observed only in the lower region of the blade 30 (that is, in an intermediate region of the blade 30 extending from 30% to 70% of the blade height, the number of ply decrement lines 80, 81 on the pressure side 40 is less than the number of ply decrement lines 82, 83 on the suction side 42) or is observed only in the lower extension region of the blade 30 (that is, in a region extending over 70% of the blade height, the number of ply decrement lines 80, 81 on the pressure side 40 is less than the number of ply decrement lines 82, 83 on the suction side 42). As a further variant (still not shown), a numerical advantage of the ply decrease lines 80, 81 on the pressure side 40 relative to the ply decrease lines 82, 83 on the suction side 42 is observed in the extended region of the blade 30, but not in the lower region (that is, in the lower region of the blade 30, the number of ply decrease lines 80, 81 on the pressure side 40 is less than or equal to the number of ply decrease lines 82, 83 on the suction side 42, and in the middle region, the number of ply decrease lines 80, 81 on the pressure side 40 is greater than the number of ply decrease lines 82, 83 on the suction side 42).

[0081] This feature makes the blade 30 more resistant to "big bird" type strikes.

[0082] As in Figure 5 and Figure 6As seen in FIG. 1 , the ply reduction lines 80, 81, 82, 83 include continuous ply reduction lines 80, 82 and discontinuous ply reduction lines 81, 83. Each continuous ply reduction line 80, 82 is formed by a layer of at least Class C extending from the leading edge 44 to the trailing edge 46 along the pressure side 40 and the suction side 42, respectively. 1 Each discontinuous ply reduction line 81, 83 includes a first section 85 and a second section 87, the first section 85 being composed of at least Category C ply reduction lines extending from the leading edge 44 to the head edge 47 along the pressure side 40 and the suction side 42, respectively. 1 The second section 87 is composed of a curve of at least category C extending from the head edge 47 to the trailing edge 46 along the pressure side 40 and the suction side 42 respectively. 1 The curve composition.

[0083] Each successive ply taper line 80 , 82 has a apex (not given a reference number) formed by the point of the ply taper line 80 , 82 farthest from the root 32 .

[0084] Each of the continuous ply reduction lines 80, 82 comprises at least one transverse portion 90 extending substantially along a transverse direction T which is substantially perpendicular to a local tangent line of the warp yarns 71. In other words, for each of the incomplete warp yarns 75 open on the transverse portion 90, the transverse direction T is substantially perpendicular to a plane locally tangent to the warp yarn column 73 to which said incomplete warp yarn 75 belongs, that is, perpendicular to a plane tangent to said warp yarn column 73 at the end 78 of said incomplete warp yarn 75.

[0085] Here and hereinafter, the term “extending substantially along a direction” means that the element in question (here the transverse portion 90) is comprised in a band centered on said direction and having a width equal to four times the mesh width of the fiber reinforcement 62. In other words, said direction constitutes the midline of the element in question and each point of said element is located at a distance from said direction less than or equal to twice the mesh width of the fiber reinforcement 62.

[0086] Here and in the following, the term "substantially perpendicular" means that the directions in question form an angle between 85° and 95°.

[0087] The transverse direction T is also substantially parallel to the local tangent of the weft yarns 72. In other words, each of the weft yarns 72 flush with the pressure side 40 or the suction side 42 along the transverse direction T is substantially parallel to said transverse direction T over the entire extension of the transverse portion 90.

[0088] Here and below, "substantially parallel" means that the directions in question form an angle of less than or equal to 5° between them.

[0089] The transverse portion 90 of each continuous ply decreasing line 80, 82 is constituted by a tip portion 92 including the tip of said ply decreasing line 80, 82. Each tip portion 92, located between the root 32 and 70% of the blade height, extends over at most 10% of the distance measured parallel to the transverse direction T between the leading edge 44 and the trailing edge 46.

[0090] Typically, each transverse portion 90 located between the root 32 and 70% of the blade height extends over at most 10% of the distance between the leading edge 44 and the trailing edge 46 measured parallel to the respective transverse direction T of said transverse portion 90 .

[0091] This regulation of the decreasing position of the yarns 71 , 72 allows their solidity to be optimized. Thus, the resistance of the blade 30 to “big bird” type strikes is enhanced.

[0092] Each discontinuous ply reduction line 81 , 83 comprises at least one terminal portion 96 extending from the blade head 38 , in particular from the head edge 47 , to 90% of the blade height, advantageously to 60% of the blade height.

[0093] The end portion 96 extends substantially along an extension direction E which forms an angle between 5° and 85° with a local tangent line of the warp yarn 71. In other words, for each of the incomplete warp yarns 75 that are open on the end portion 96, the extension direction E forms an angle between 5° and 85° with a plane that is locally tangent to the warp yarn column 73 to which the incomplete warp yarn 75 belongs, that is, with a plane that is tangent to the warp yarn column 73 at the end 78 of the incomplete warp yarn 75.

[0094] The extension direction E also forms an angle of between 5° and 85° with the local tangent line of the weft yarn 72. In other words, for each of the incomplete weft yarns 76 that are open at the end portion 96, the extension direction E forms an angle of between 5° and 85° with a plane that is locally tangent to the weft yarn column 74 to which the incomplete weft yarn 76 belongs, that is, with a plane that is tangent to the weft yarn column 74 at the end 78 of the incomplete weft yarn 76.

[0095] Each end portion 96 on the side of the pressure side 40 also meets at least one of the following criteria at each point of the end portion:

[0096] the terminal portion 96 is spaced apart from the downstream edge 57 of the shroud 52 on the pressure side by a distance greater than or equal to three times the mesh width of the fiber reinforcement 62 , and

[0097] The tangent of the terminal portion 96 forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent of said downstream edge 57 on the pressure side at the height of said point.

[0098] In other words, for any section of the end portion 96 on the pressure side 40 that is spaced apart from the downstream edge 57 of the shroud 52 on the pressure side by a distance less than three times the mesh width of the fiber reinforcement 62, a tangent line of the end portion 96 at each point of the section forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with a tangent line of the downstream edge 57 on the pressure side at the height of the point.

[0099] Each end portion 96 on the suction side 42 also meets at least one of the following criteria at each point of the end portion:

[0100] the terminal portion 96 is spaced apart from the downstream edge 58 of the shroud 52 on the suction side by a distance greater than or equal to three times the mesh width of the fiber reinforcement 62 , and

[0101] The tangent of the terminal portion 96 forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with a tangent of said downstream edge 58 on the suction side at the height of said point.

[0102] In other words, for any section of the end portion 96 on the suction side 42, wherein the distance between the end portion 96 and the downstream edge 58 of the shroud 52 on the suction side is less than three times the mesh width of the fiber reinforcement 62, the tangent of the end portion 96 at each point of the section forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent of the downstream edge 58 on the suction side at the height of the point.

[0103] Most of the end portions 96, here all of the end portions 96, consist of inclined end portions 98, the extension direction E of which forms an angle of between 10° and 65°, advantageously between 15° and 45°, with the local tangent of the warp yarn 71. In other words, for each of the incomplete warp yarns 75 opening on the inclined end portion 98, the extension direction E of the inclined end portion 98 forms an angle of between 10° and 65°, advantageously between 15° and 45°, with the plane locally tangent to the warp yarn column 73 to which the incomplete warp yarn 75 belongs (that is, with the plane tangent to the warp yarn column 73 at the end 78 of the incomplete warp yarn 75).

[0104] For each inclined end portion 98, the extension direction E also forms an angle of between 25° and 80°, advantageously between 45° and 75°, with the local tangent line of the weft yarn 72. In other words, for each of the incomplete weft yarns 76 that open on the inclined end portion 98, the extension direction E of the inclined end portion 98 forms an angle of between 25° and 80°, advantageously between 45° and 75°, with the plane that is locally tangent to the weft yarn column 74 to which the incomplete weft yarn 76 belongs (that is, with the plane that is tangent to the weft yarn column 74 at the end 78 of the incomplete weft yarn 76).

[0105] These features impart to the blade 30 increased resistance to "bird" type strikes.

[0106] Due to the features of the above-described embodiments, the mechanical properties of the blade with composite structure are improved in the event of impact with birds or hail. This makes it possible to refine the blade while maintaining constant resistance, thereby improving weight and improving aerodynamic performance.

Claims

1. A blade (30) for a turbine fan, the blade comprising: a root portion (32) configured to be attached to a fan disk (28); and, a blade body (34) capable of extending in an air flow and defining a blade head (38) opposite to the root (32), the blade (30) having a pressure side (40), a suction side (42), a leading edge (44) and a trailing edge (46), the blade (30) being elongated in a longitudinal direction (Y) extending from the root (32) to the blade head (38), the longitudinal direction (Y) being substantially perpendicular to a chord direction (C) extending from the leading edge (44) to the trailing edge (46), the blade (30) being at least partially constituted by a structure (50) made of composite material, the structure comprising a fiber reinforcement (62) obtained by three-dimensional weaving and a matrix (64), the fiber reinforcement (62) being embedded in the matrix, the fiber reinforcement (62) being The fiber reinforcement (62) comprises a plurality of interwoven plies (66, 68), each ply (66, 68) being formed by warp yarns (71) extending substantially perpendicular to the chord direction (C) and weft yarns (72) extending substantially perpendicular to the longitudinal direction (Y), the warp yarns (71) and the weft yarns (72) comprising incomplete yarns (75, 76), each incomplete yarn having an end (78) on the pressure side (40) or the suction side (42), the pressure side (40) and the suction side (42) each having at least one ply reduction line (80, 81, 82, 83), the at least one ply reduction line connecting the ends (78) of the incomplete yarns (75, 76) of the same ply (66, 68), Wherein, in a lower region of the blade (30) between the root (32) and 30% of the blade height, and / or in an extended region of the blade (30) between the root (32) and 70% of the blade height, the number of ply reduction lines (80, 81) on the pressure side (40) is greater than the number of ply reduction lines (82, 83) on the suction side (42).

2. The blade (30) according to claim 1, wherein: Over the entire blade (30), the number of ply decreasing lines (80, 81) on the pressure side (40) is greater than the number of ply decreasing lines (82, 83) on the suction side (42).

3. The blade (30) according to claim 1 or 2, wherein: At least one ply reduction line (80, 82) includes at least one transverse portion (90) located between the root (32) and 70% of the blade height, the transverse portion including a tip portion (92), the transverse portion (90) or each transverse portion extending generally along a transverse direction (T) substantially perpendicular to a local tangent to the warp yarns (71), the tip portion (92) or each tip portion extending over at most 10% of the distance between the leading edge (44) and the trailing edge (46) measured parallel to the transverse direction (T).

4. The blade (30) according to claim 3, wherein: The or each transverse portion (90) located between the root (32) and 70% of the blade height extends over at most 10% of the distance between the leading edge (44) and the trailing edge (46) measured parallel to the transverse direction (T).

5. The blade (30) according to any one of the preceding claims, wherein: At least one ply reduction line (81, 83) comprises an end portion (96) extending from the blade head (38) to 90% of the blade height, advantageously to 60% of the blade height, the end portion or each end portion (96) extending substantially along an extension direction (E) forming an angle of between 5° and 85° with a local tangent to the warp yarn (71).

6. The blade (30) according to claim 5, wherein: For the or each end portion (96), the extension direction (E) forms an angle of between 5° and 85° with a local tangent to the weft yarn (72).

7. The blade (30) according to claim 5 or 6, wherein: At least one end portion (96) consists of an inclined end portion (98), the extension direction (E) of which forms an angle with the local tangent of the warp yarn (71) between 10° and 65°, advantageously between 15° and 45°.

8. The blade (30) according to claim 7, wherein: For the or each inclined end portion (98), the extension direction (E) forms an angle with a local tangent to the weft yarn (72) comprised between 25° and 80°, advantageously between 45° and 75°.

9. The blade (30) according to claim 7 or 8, wherein: A majority of the end portion (96) is comprised of an angled end portion (98).

10. A blade (30) according to any one of claims 5 to 9, comprising an additional shroud (52) covering the composite structure (50) along the leading edge (44), the shroud (52) having a downstream edge (57) on the pressure side and a downstream edge (58) on the suction side, the tip portion (96) on the pressure side (40) or each tip portion on the pressure side meeting at each point of the tip portion on the pressure side at least one of the following criteria: the terminal portion (96) is spaced apart from the downstream edge (57) on the pressure side by a distance greater than or equal to three times the mesh width of the fiber reinforcement (62), and a tangent to the terminal portion (96) forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with a tangent to the downstream edge (57) on the pressure side at the height of the point, The end portion (96) on the suction side (42), or each end portion on the suction side, meets at least one of the following criteria at each point of the end portion on the suction side: the terminal portion (96) is spaced from the downstream edge (58) on the suction side by a distance greater than or equal to three times the mesh width of the fiber reinforcement (62), and The tangent of the terminal portion (96) forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent of the downstream edge (58) on the suction side at the height of the point.

11. A blade (30) according to any one of the preceding claims, wherein: The root portion (32) is configured to be inserted into a groove of a fan disk (28), and the blade (30) further includes a support (36) connecting the root portion (32) to the blade airfoil (34).

12. A turbomachine fan (22) comprising a plurality of blades (30) according to any one of the preceding claims.

13. A turbomachine (12) comprising a fan (22) according to claim 12.

14. An aircraft (10) comprising a turbine (12) according to claim 13.

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