Blade having composite structure with improved ply decline orientation

Abstract

The disclosed fan blade is at least partially composed of a structure (50) made of a composite material, the structure comprising a fibrous reinforcement and a matrix. The fibrous reinforcement includes a plurality of layouts, each of which is formed from warp and weft strands. The warp and weft strands comprise incomplete strands, each having an end on the pressure side (40) or the suction side. The pressure side (40) and the suction side each have at least one ply decline (80, 81) connecting the ends of the incomplete strands of the same ply. The at least one tapering line (81) includes an end portion (96) extending from the blade tip to 90% of the blade height. The end portion (96) extends generally along an extension direction (E) that forms an angle of between 5 DEG and 85 DEG with a local tangent to the warp strands.

Description

Technical Field

[0001] The present invention relates to a turbine fan blade of the following type, which includes a root configured to be inserted into a groove of a fan disk, an airfoil capable of extending in an air flow and defining a blade tip opposite to the root, and a strut connecting the root to the airfoil, 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 tip, 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 warp yarn strands extending substantially perpendicular to the chord direction and weft yarn strands extending substantially perpendicular to the longitudinal direction, the warp yarn strands and the weft yarn strands comprising incomplete strands, each strand 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, each ply reduction line connecting the ends of the incomplete strands 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 conditions. It has therefore been proposed to use blades consisting at least in part of a structure made of composite materials 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 1 526 285, for example.

[0005] Most commonly, the thickness of the blade decreases from the mainstay to the blade tip. The blade also tapers towards the leading and trailing edges. In order to obtain such a reduced thickness for a blade consisting of a structure made of composite material, the number of plies constituting said structure generally decreases as the blade tip, leading and trailing edge are approached. To achieve this, the strands forming these plies are removed from the structure and interrupted along a ply reduction line on the pressure side or suction side, as described, for example, in EP 3 292 991.

[0006] During the life of the engine, fan blades are subject to bird and hail strikes. Aircraft engine certification regulations therefore logically require fan blades to have a certain resistance to this type of impact. However, composite blades tend not to be as resistant to such impacts as their metallic equivalents. Therefore, to meet certification regulations, 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 3 292 991, WO 2020 / 089345 and FR 3 087 711, 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 deserve optimization. Summary of the invention

[0008] The object of the present invention is to improve the mechanical properties of a composite structure blade when it is hit by a bird or hail.

[0009] To this end, according to a first aspect, the object of the present invention is a turbine fan blade of the above-mentioned type, wherein at least one ply reduction line comprises an end portion extending from the blade tip to 90% of the blade height, advantageously to 60% of the blade height, the end portion or each end portion extending generally in an extension direction forming an angle of between 5° and 85° with a local tangent of the warp yarn strands.

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

[0011] - 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 strand;

[0012] 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 line of the warp yarn strand;

[0013] - for the or each inclined end portion, the direction of extension forms an angle with a local tangent to the weft yarn strand of between 25° and 80°, advantageously between 45° and 75°;

[0014] - most of the terminal portion consists of an inclined terminal portion;

[0015] - 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 the end portion on the pressure side at least one of the following criteria:

[0016] 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

[0017] 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,

[0018] The 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:

[0019] - 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

[0020] 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,

[0021] - 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 generally in a transverse direction substantially perpendicular to local tangents to the warp yarn strands, 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;

[0022] - 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;

[0023] - in a lower region of the blade between the root and 30% of the blade height and / or in an extended region of the blade between the root and 70% of the blade height, the number of ply reduction lines on the pressure side is greater than the number of ply reduction lines on the suction side; and

[0024] - Over the entire blade, the number of ply decline lines on the pressure side is greater than the number of ply decline lines on the suction side.

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

[0026] According to a third aspect, a further object of the invention is a turbomachine comprising such a fan.

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

[0028] Other features and advantages of the present invention will appear 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 a composite material structure of a blade.

[0034] - Figure 6 yes Figure 5 A three-quarter rear perspective view of a structure made of composite materials.

[0035] - Figure 7 Is a part of the structure made of composite materials 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 in FIG. 1 , 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 aircraft comprises a fuselage 14, a tail assembly 16 and two wings 18. Here, there are two turbines 12, each mounted under a respective wing 18. In an alternative (not shown), the turbines 12 are arranged along the fuselage 14, for example close to the tail assembly 16. In another alternative (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 turbine 12 is typically a turbofan engine, advantageously having a high bypass ratio.

[0042] The cowling 24 defines an air duct. The cowling is fixedly mounted on the nacelle 20. In the example shown, the cowling is arranged inside the nacelle 20. In an alternative (not shown), the turbine 12 is without a cowling.

[0043] The fan 22 comprises a fan rotor 26 which is rotatable 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 distance 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 fix the blade 30 to the hub 28, for example by means of a pin attachment (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 portion 32 is dovetail-shaped. In an alternative (not shown), the root portion 32 has any shape suitable for assembling the blade 30 to the hub 28.

[0047] When the turbine 12 is in operation, the airfoil 34 can be placed in the air flow so as to generate lift. At the end of the airfoil opposite the root 32 , the airfoil defines a blade tip 38 .

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

[0049] The airfoil 34 also has a blade tip edge 47 constituted by the free edge of the blade 30 farthest from the root 32. The blade tip edge 47 can extend along the inner surface of the cowling 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, in other words between the exit of the support 48 and the inter-blade platform (not shown) which internally delimits the secondary flow duct. The strut 36 is therefore not configured to extend in 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 tip 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 of the blade 30 and the exit of the support 48 along the axis Y. This distance is usually expressed in a dimensionless manner as a percentage of the distance from the tip edge 47 to the exit of the support 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 tip 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 proximity of shapes between the blade 30 and the structure 50, the same terminology will be used herein to refer to both the surface area 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 also to the surface of the structure 50 on the pressure side, even if the surface does not directly define the pressure side of the blade 30 (in other words, even if the surface of the structure 50 on 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 also to the surface of the structure 50 on the suction side, even if the surface does not directly define the suction side of the blade 30 (in other words, even if the surface of the structure 50 on 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. The 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 pressure side 40, defines a downstream edge 57 of the shroud 52 on the pressure side. The second fin 55, arranged on the suction side 42, defines a downstream edge 58 of the shroud 52 on the suction side.

[0059] The two fins 54 , 55 together define 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 stacked along the thickness of the blade 30 , in other words, along a direction extending from the pressure side 40 to the suction side 42 .

[0063] Each ply 66, 68 is formed of a warp strand 71 and a weft strand 72. Each warp strand 71 extends from the root 32 to the tip 38 substantially perpendicular to the chord direction C. Each weft strand 72 extends substantially perpendicular 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" is to be understood here and hereinafter to mean that the strands 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, in other words at least some of the warp strands 71 ​​belonging to a ply 66, 68 are combined with weft strands 72 belonging to the other ply 66, 68. The three-dimensional weaving technique is described, for example, in WO 2006 / 136755.

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

[0067] Each warp thread strand 71 belongs to only one warp thread 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 strands 71 ​​are offset in the longitudinal direction so that the warp strands 71 ​​and the weft strands 72 are connected at different heights depending on the plane.

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

[0071] Each weft thread strand 72 belongs to only one weft thread row 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 column 74 is substantially perpendicular to each warp yarn column 73 , in other words, for each weft yarn column 74 -warp yarn column 73 pair, the average normal of the weft yarn column 74 is substantially perpendicular to the average normal of the warp yarn column 73 .

[0074] Return to Figure 7 , the plies 66, 68 include at least one complete ply 66 for which each warp strand 71 extends from the root 32 to the tip 38 and each weft strand 72 extends from the leading edge 44 to the trailing edge 46, and the partial plies 68 include incomplete warp strands 75 and / or incomplete weft strands 76. The incomplete warp strands 75 are composed of warp strands 71 ​​interrupted at the surface of the structure 50 before the tip 38 so as to be able to reduce the thickness of the blade 30 along the longitudinal axis Y. The incomplete weft strands 76 are composed of weft strands 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 strands 71, 72, although interrupted on the pressure side 40 or the suction side 42, are extended by second strands 71, 72 which begin substantially where the first strands 71, 72 end, the first strands being not considered to constitute incomplete strands 75, 76.

[0076] Each incomplete strand 75, 76 has at least one end 78 on the pressure side 40 or the suction side 42. The ends 78 of the incomplete strands 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 ” will denote the average of the average distances between the rows of warp threads 73 on the one hand and the rows of weft threads 74 on the other hand.

[0078] For each partial ply 68, the ends 78 of the incomplete strands 75, 76 that make them up are located 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 tip edge 47. The inner region has at each point a number of strands 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 strands 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 strands 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 is observed again 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. In an alternative (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 (in other words, 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 extended region of the blade 30 (in other words, in a region extending beyond 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). In another alternative (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 an extended area of ​​the blade 30, but not in the lower area (in other words, in the lower area 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 area, 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 "large bird" strikes.

[0082] As in Figure 5 and Figure 6 As 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 through 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 tip edge 47 through 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 tip edge 47 to the trailing edge 46 through 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 continuous ply reduction line 80, 82 comprises at least one transverse portion 90 extending generally in a transverse direction T substantially perpendicular to a local tangent to the warp yarn strand 71. In other words, for each of the incomplete warp yarn strands 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 strand 75 belongs, in other words, perpendicular to a plane tangent to said warp yarn column 73 at the end 78 of said incomplete warp yarn strand 75.

[0085] Here and hereinafter, the term "generally extending in a direction" will mean that the element in question (here the transverse portion 90) is included 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" will mean that the directions in question form an angle between 85° and 95°.

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

[0088] Here and in the following, the term "substantially parallel" will mean that the directions in question form an angle of less than 5° between each other.

[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 of said transverse portion 90 .

[0091] This regulation of the decreasing position of the strands 71 ​​, 72 optimizes their robustness and thus increases the resistance of the blade 30 to “big bird” strikes.

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

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

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

[0095] Each end portion 96 on 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, the distance between this section and the downstream edge 57 on the pressure side of the shield 52 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 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 thereof:

[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, the distance between this section and the downstream edge 58 on the suction side of the shield 52 is less than three times the mesh width of the fiber reinforcement 62, and 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 strand 71. In other words, for each of the incomplete warp strands 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 strand 75 belongs (in other words, with the plane tangent to the warp yarn column 73 at the end 78 of the incomplete warp yarn strand 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 strand 72. In other words, for each of the incomplete weft strands 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 strand 76 belongs (in other words, with the plane that is tangent to the weft yarn column 74 at the end 78 of the incomplete weft yarn strand 76).

[0105] These features provide blade 30 with increased resistance to "bird" strikes.

[0106] By the features of the above embodiments, the mechanical performance of the composite structure blade is improved in the event of a bird or hail impact. This enables thinner blades while maintaining constant strength, thereby reducing weight and improving aerodynamic performance.

Claims

1. A turbine fan blade (30), comprising: a root portion (32) configured to be attached to a fan disk (28); and, an airfoil (34) capable of extending in an air flow and defining a blade tip (38) opposite 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 tip (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) comprises a plurality of interwoven plies (66, 68), each ply (66, 68) being formed by warp strands (71) extending substantially perpendicular to the chord direction (C) and weft strands (72) extending substantially perpendicular to the longitudinal direction (Y), the warp strands (71) and the weft strands (72) comprising incomplete strands (75, 76), each incomplete strand 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), each ply reduction line connecting the ends (78) of the incomplete strands (75, 76) of the same ply (66, 68), In which at least one ply reduction line (81, 83) includes an end portion (96), which extends from the blade tip (38) to 90% of the blade height, advantageously to 60% of the blade height, and the end portion or each end portion (96) generally extends in an extension direction (E), and the extension direction forms an angle between 5° and 85° with the local tangent of the warp yarn strand (71).

2. The blade (30) according to claim 1, 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 strand (72).

3. The blade (30) according to claim 1 or 2, wherein: At least one end portion (96) consists of an inclined end portion (98), the extension direction (E) of which forms an angle between 10° and 65°, advantageously between 15° and 45°, with the local tangent of the warp yarn strand (71).

4. The blade (30) according to claim 3, wherein: For the or each inclined end portion (98), the extension direction (E) forms an angle with a local tangent to the weft yarn strand (72) comprised between 25° and 80°, advantageously between 45° and 75°.

5. The blade (30) according to claim 3 or 4, wherein: A majority of the end portion (96) is comprised of an angled end portion (98).

6. A blade (30) according to any one of the preceding claims, 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.

7. A blade (30) according to any one of the preceding claims, 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 in a transverse direction (T) substantially perpendicular to a local tangent to the warp yarn strands (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).

8. The blade (30) according to claim 7, 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).

9. A blade (30) according to any one of the preceding claims, 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).

10. A blade (30) according to any one of the preceding claims, 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).

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 strut (36) connecting the root portion (32) to the 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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