SHOVEL WITH COMPOSITE STRUCTURE AND IMPROVED PLY DROP ALIGNMENT

Description

DOMAINE DE L'INVENTION

[0001] The present invention relates to a turbine fan blade for a turbomachine, of the type comprising a foot configured to be inserted into a cavity of a fan disk, a blade adapted to extend in an airflow and defining a blade tip opposite the foot, and a strut connecting the foot to the blade, the blade having an intrados, an extrados, a leading edge and a trailing edge, the blade being elongated along a longitudinal direction from the foot to the blade tip, said longitudinal direction being substantially orthogonal to a chord direction from the leading edge to the trailing edge, the blade being composed at least in part of a composite material structure comprising a fibrous reinforcement obtained by three-dimensional weaving and a matrix in which the fibrous reinforcement is embedded, the fibrous reinforcement comprising a plurality of interwoven layers,each layer being formed of warp strands extending substantially orthogonally to the chord direction and of weft strands extending substantially orthogonally to the longitudinal direction, the warp and weft strands including incomplete strands each having a terminal end on the intrados or extrados, the intrados and / or extrados having layer exit lines each connecting the terminal ends of the incomplete strands of the same layer.

[0002] The invention also relates to a turbomachine fan comprising a plurality of blades of the aforementioned type, a turbomachine comprising such a fan, and an aircraft comprising such a turbomachine. ARRIERE-PLAN TECHNOLOGIQUE

[0003] Turbomachine blades, and in particular fan blades, are subjected to significant mechanical and thermal stresses and must meet strict weight and size requirements. It has therefore been proposed to use blades composed at least partially of a composite material structure with a fibrous reinforcement densified by a polymer matrix. These blades are lighter than metallic blades with equivalent propulsive characteristics and offer satisfactory heat resistance.

[0004] Such dawns are known for example from EP 1 526 285.

[0005] Most often, blades have a thickness that decreases from the stem to the tip. They also taper towards the leading and trailing edges. To achieve this decreasing thickness with a blade made of a composite material structure, the number of layers composing the structure is generally reduced as one approaches the tip, leading edge, and trailing edge. This is accomplished by extending the strands forming these layers out of the structure and interrupting them along layer exit lines on the lower or upper surface, as described, for example, in EP 3 292 991.

[0006] During an engine's lifetime, fan blades are subjected to impacts from birds and hailstones. Aircraft engine certification regulations therefore logically mandate a certain level of resistance for fan blades to these types of impacts. However, the resistance of composite blades to such impacts tends to differ from that of their metallic counterparts. To comply with certification regulations, composite blades are often thicker, which can complicate the design process for managing the blade's aerodynamic performance and could partially negate the weight savings resulting from the use of composite materials.

[0007] Solutions have been proposed, for example in EP 3 292 991, WO 2020 / 089345 and FR 3 087 711, to resolve this type of problem and improve the mechanical behavior of composite blades under such impacts. These solutions may be satisfactory but could also benefit from further optimization. EXPOSE DE L'INVENTION

[0008] One objective of the invention is to improve the mechanical behavior of composite structure blades in the event of impact from birds or hailstones.

[0009] To this end, the invention relates, according to a first aspect, to a turbine blade for a turbomachine of the aforementioned type, in which at least one layer exit line includes at least one transverse portion located between the foot and 70% of the blade height, of which a top portion, the or each transverse portion extending globally along a transverse direction substantially orthogonal to the local tangent to the chain strands, the or each top portion extending over at most 10% of the distance between the leading edge and the trailing edge measured parallel to the transverse direction.

[0010] According to particular embodiments of the invention, the blade also has one or more of the following characteristics, taken individually or in any technically possible combination(s): where each transverse portion located between the root and 70% of the blade height extends over no more than 10% of the distance between the leading edge and the trailing edge measured parallel to the transverse direction; the number of layer exit lines on the lower surface is greater than the number of layer exit lines on the upper surface in a low 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 layer exit lines on the lower surface is, over the entire blade, greater than the number of layer exit lines on the upper surface; at least one layer exit line includes a terminal portion that extends from the blade tip to 90% of the blade height, advantageously to 60% of the blade height,the terminal portion(s) extending overall in a direction of extension forming an angle between 5° and 85° with the local tangent to the warp strands; for the terminal portion(s), the direction of extension forms an angle between 5° and 85° with the local tangent to the weft strands; at least one terminal portion is constituted by an inclined terminal portion whose direction of extension forms an angle between 10° and 65°, advantageously between 15° and 45°, with the local tangent to the warp strands; for the inclined terminal portion(s), the direction of extension forms an angle between 25° and 80°, advantageously between 45° and 75°, with the local tangent to the weft strands; a majority of the terminal portions are constituted by inclined terminal portions; the blade includes an attached shield covering the composite structure along the leading edge,the shield having a downstream edge on the intrados and a downstream edge on the extrados, the terminal portion(s) on the intrados side fulfilling at least one of the following criteria at each of its points: ∘ the terminal portion is spaced from the downstream edge on the intrados by a distance greater than or equal to three times the mesh width of the fibrous reinforcement, and ∘ the tangent to the terminal portion forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to the downstream edge on the intrados at the height of said point, and the terminal portion(s) on the extrados side fulfilling at least one of the following criteria at each of its points: ∘ the terminal portion is spaced from the downstream edge on the extrados by a distance greater than or equal to three times the mesh width of the fibrous reinforcement, and ∘ the tangent to the terminal portion forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to the downstream edge on the extrados at the height of said point.

[0011] The invention also relates, according to a second aspect, to a turbomachine blower comprising a plurality of blades as defined above.

[0012] The invention also relates, according to a third aspect, to a turbomachine comprising such a blower.

[0013] Finally, according to a fourth aspect, the invention relates to an aircraft comprising such a turbomachine. BREVE DESCRIPTION DES FIGURES

[0014] Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which: there Figure 1 is a top view of an aircraft according to an exemplary embodiment of the invention, the Figure 2 is a perspective view, from a three-quarter front angle, of a turbomachine from the aircraft of the Figure 1 , there Figure 3 is a side view of a fan blade of the turbomachine of the Figure 2 , there Figure 4 is a simplified cross-sectional view along a plane marked IV-IV on the Figure 3 , there Figure 5 is a perspective view, from a three-quarter front angle, of a composite material structure of the dawn of the Figure 3 , there Figure 6 is a perspective view, from a three-quarter rear angle, of the composite material structure of the Figure 5 , there Figure 7 is a simplified cross-sectional view, according to a plane marked VII-VII on the Figure 6 , part of the structure made of composite material, the Figure 8 is a view of a detail marked VIII of the Figure 4 , and the Figure 9 is a view of a detail marked IX of the Figure 7 . DESCRIPTION DETAILLEE

[0015] Aircraft 10 shown on the Figure 1 includes 12 turbomachines to propel it.

[0016] In the example shown, aircraft 10 is an airplane. It conventionally comprises a fuselage 14, a tail assembly 16, and two wings 18. The turbomachines 12 are two in number and are each housed under a respective wing 18. Alternatively (not shown), the turbomachines 12 are arranged along the fuselage 14, for example, near the tail assembly 16. In yet another alternative (also not shown), aircraft 10 comprises a single turbomachine 12 or at least three turbomachines 12.

[0017] One of the 12 turbomachines is shown on the Figure 2 As can be seen in this Figure, it includes a nacelle 20 intended to be attached to a wing 18 or to the fuselage 14 of the aircraft 10, a fan 22 and a fairing 24 surrounding the fan 22. It also includes, in a conventional manner, a compressor, a combustion chamber and a turbine (not shown), the turbine being mechanically connected to the fan 22 to drive it in rotation around its axis.

[0018] The turbomachine 12 is typically a turbofan engine, advantageously with a high bypass ratio.

[0019] The fairing 24 delimits the air stream. It is fixedly mounted on the nacelle 20. In the illustrated example, it is located inside the nacelle 20. In an alternative configuration (not shown), the turbomachine 12 is without a fairing.

[0020] The blower 22 includes a blower rotor 26 adapted to be driven in rotation relative to the nacelle 20 about an axis of rotation X which here coincides with the main axis of the turbomachine 12. The blower rotor 26 includes a hub 28, commonly called the "blower disc", and a plurality of blades 30 fixed to the hub 28 and extending in substantially radial directions from the hub 28. In the example shown, the blades 30 are all identical, and arranged with a constant angular gap between two successive blades 30.

[0021] There figure 3 illustrates schematically one of these blades 30. This blade 30 includes a foot 32, a blade 34 with an aerodynamic profile and a strut 36.

[0022] The foot 32 is designed to allow the blade 30 to be attached to the hub 28, for example by means of a pinned fastener (not shown). For this purpose, the foot 32 is configured to be inserted into a recess (not shown) in the hub 28.

[0023] In the example shown, foot 32 is dovetail shaped. Alternatively (not shown), foot 32 may have any shape suitable for attaching blade 30 to hub 28.

[0024] The blade 34 is designed to be placed in an airflow, when the turbomachine 12 is in operation, in order to generate lift. It defines, at its end opposite the foot 32, a blade head 38.

[0025] Blade 34 also has an intrados 40 ( Figure 4 ), an extrados 42, a leading edge 44 and a trailing edge 46.

[0026] The blade 34 still has a blade head edge 47, formed by the free edge of the blade 30 furthest from the foot 32. The blade head edge 47 is suitable to extend along an internal surface of the fairing 24 surrounding the blower.

[0027] The strut 36 corresponds to the area of ​​the blade 30 extending between the root 32 and the blade 34, that is, between the outlet of the spans 48 and the inter-blade platforms (not shown) which internally delimit the secondary flow channel. The strut 36 is therefore not configured to extend into an airflow.

[0028] The blade 30 is elongated along a longitudinal axis Y orthogonal to the X axis and extending from the foot 32 to the head 38. The longitudinal axis Y is also orthogonal to a chord direction C ( Figure 4 ) connecting the leading edge 44 to the trailing edge 46.

[0029] Here and in the following, "blade height" means a distance measured along the Y axis between a point on the blade 30 and the exit of the spans 48. This distance is most often expressed dimensionlessly, as a percentage of the distance from the leading edge 47 to the exit of the spans 48.

[0030] As seen on the Figure 4 The blade 30 has a blade core 49 at which the thickness of the blade 30 along the chord direction C is maximum. In other words, the thickness of the blade 30 decreases from the blade core 49 towards each of the leading edge 44 and trailing edge 46. The blade core 49 is centered on the longitudinal axis Y.

[0031] In the example shown, the blade 30 is twisted around the blade core 49, so that the chord C pivots around the longitudinal axis Y as a function of the blade height.

[0032] With reference to the Figure 4 The 30 blade is here composed of a 50 structure made of composite material. As visible on the Figures 5 And 6 , this structure 50 extends here along the longitudinal axis Y from the foot 32 to the head 38, along the chord direction C from the leading edge 44 to the trailing edge 46 and along the thickness of the blade 30 from the lower surface 40 to the upper surface 42. In particular, the structure 50 substantially follows the shape of the blade 30. Optionally, it defines, at least in part, the outer surface of the blade 30.

[0033] Due to the similar shape between the blade 30 and the structure 50, the same terms will be used here and thereafter to refer both to surface regions of the blade 30 and to the elements of the structure 50 that relate to it. Thus, the term "intrados 40" refers both to the intrados of the blade 30 itself, and also to the face of the structure 50 on the intrados side, even though this face does not directly define the intrados of the blade 30 (that is, even if the face of the structure 50 on the intrados side is covered by another element). Similarly, the term "extrados 42" refers both to the extrados of the blade 30 itself, and also to the face of the structure 50 on the extrados side, even though this face does not directly define the extrados of the blade 30 (that is, even if the face of the structure 50 on the extrados side is covered by another element).

[0034] Structure 50 is commonly referred to as the "body" of blade 30.

[0035] Still referring to the Figure 4 The wing 30 is also composed here of an added shield 52 covering the composite structure 50 along the leading edge 44. This shield 52 is formed of two fins 54, 55 connected to each other at the top 56 of the shield 52. A first fin 54, located on the side of the lower surface 40, defines a downstream edge on the lower surface 57 of the shield 52. The second fin 55, located on the side of the upper surface 42, defines a downstream edge on the upper surface 58 of the shield 52.

[0036] The two fins 54, 55 define between them a cavity 59 in which is housed an upstream end 60 of the structure 50.

[0037] Shield 52 is typically made of metallic tinsel.

[0038] With reference to the Figure 7 , structure 50 includes a fibrous reinforcement 62 and a matrix 64 in which the fibrous reinforcement 62 is embedded.

[0039] The fibrous reinforcement 62 comprises a plurality of interwoven layers 66, 68, stacked according to the thickness of the blade 30, that is to say in the direction going from the intrados 40 to the extrados 42.

[0040] Each layer 66, 68 is formed of warp strands 71 ​​and weft strands 72. Each warp strand 71 extends from the foot 32 to the head 38, substantially orthogonally to the chord direction C. Each weft strand 72 extends from the blade core 49 to each of the leading edge 44 and trailing edge 46, substantially orthogonally to the longitudinal axis Y.

[0041] By "approximately orthogonally", it is understood here and in the following that the strands 70, 72 form an angle between 85 and 95° with the direction or axis concerned (here respectively the direction of chord C and the longitudinal axis Y)

[0042] The fibrous reinforcement 52 is obtained by three-dimensional weaving, i.e. some at least of the warp strands 71 ​​belonging to one layer 66, 68 bind weft strands 72 belonging to another layer 66, 68. Three-dimensional weaving techniques are described for example in WO 2006 / 136755.

[0043] As seen on the Figure 8 , the warp strands 71 ​​are arranged along warp columns 73 each formed by the juxtaposition, according to the thickness of the blade 30, of the warp strands 71 ​​of the different layers 66, 68. Thus, each warp column 73 extends along a surface roughly orthogonal to the direction of chord C. Each warp strand 71 belongs to a single warp column 73.

[0044] Each chain column 73 is substantially parallel to its neighbors. In other words, for each blade height, the normal to each chain column 73 forms an angle less than or equal to 5° with the normal to each of its neighbors.

[0045] The view of the Figure 7 corresponds to a cut in a column of chain 73. The figure 7 This illustrates one of the many planes that repeat along the chord direction C between the leading edge 44 and the trailing edge 46. The other planes are similar to the plane illustrated, except that the warp strands 71 ​​are offset along the longitudinal direction so that the warp strands 71 ​​and the weft strands 72 are linked at different heights depending on the plane.

[0046] As seen on the Figure 9 , the weft strands 72 are arranged according to weft columns 74 each formed by the juxtaposition, according to the thickness of the blade 30, of the weft strands 72 of the different layers 66, 68. Thus, each weft column 74 extends along a surface substantially orthogonal to the longitudinal axis Y.

[0047] Each weft strand 72 belongs to a single weft column 74

[0048] Each 74-frame column is substantially parallel to its neighbors. In other words, the normal to each 74-frame column forms an angle of less than or equal to 5° with the normal to each of its neighbors.

[0049] Moreover, each weft column 74 is substantially orthogonal to each warp column 73, that is to say that, for each pair weft column 74 - warp column 73, the average normal to the weft column 74 is substantially orthogonal to the average normal to the warp column 73.

[0050] Back to the Figure 7 The layers 66, 68 comprise at least one complete layer 66, in which each of the warp strands 71 ​​extends from the foot 32 to the head 38 and each of the weft strands 72 extends from the leading edge 44 to the trailing edge 46, and partial layers 68 comprising incomplete warp strands 75 and / or incomplete weft strands 76. The incomplete warp strands 75 consist of warp strands 71 ​​that are interrupted on the surface of the structure 50, before the head 38, to allow a reduction in the thickness of the blade 30 along the longitudinal axis Y. The incomplete weft strands 76 consist of weft strands 72 that are interrupted on the surface of the structure 50, before the leading edge 44 and / or the trailing edge 46, to allow a reduction in the thickness from dawn 30 following the direction of rope C.

[0051] It should be noted that a first strand 71, 72 which, although interrupted at the intrados 40 or the extrados 42, is prolonged by a second strand 71, 72 beginning substantially where the first strand 71, 72 ends, is not considered to constitute an incomplete strand 75, 76.

[0052] Each incomplete strand 75, 76 has at least one terminal end 78 on the intrados 40 or on the extrados 42. The terminal ends 78 of the incomplete strands 75, 76 of the same layer 68 are spaced two by two by a distance on the order of the mesh width of the fibrous reinforcement 62.

[0053] By "mesh width of the fibrous reinforcement 62", we mean here and in the following the average between, on the one hand, the average distance between the warp columns 73 and, on the other hand, the average distance between the weft columns 74.

[0054] For each partial layer 68, the terminal ends 78 of the incomplete strands 75, 76 composing it are connected to each other by a layer output line 80, 81, 82, 83 ( Figures 5 And 6 ) respective present at the intrados 40 or the extrados 42. This exit line of layer 80, 81, 82, 83 is constituted by a curve of class at least C 1< (or by a set of two curves each of class at least C') running through the intrados 40, respectively the extrados 42.

[0055] Each layer exit line 80, 81, 82, 83 forms a boundary between two blade regions (not referenced): an inner region extending from the layer exit line 80, 81, 82, 83 to the foot 32, and an outer region extending from the layer exit line 80, 81, 82, 83 to each of the leading edge 44, trailing edge 46, and tip edge 47. The inner region has, at each point, a number of strands 71, 72 stacked according to the blade thickness 30 greater than or equal to a first value. The outer region has, at each point, a number of strands 71, 72 stacked according to the blade thickness 30 less than or equal to a second value strictly less than the first value. In other words, the number of strands 71, 72 stacked according to the thickness of the blade 30 is lower in the outer region than in the inner region.

[0056] Here, the number of exit lines from layers 80 and 81 on the lower surface of the 40th wing is greater than the number of exit lines from layers 82 and 83 on the upper surface of the 42nd wing in a low region of dawn 30 extending from foot 32 to 30% of dawn height. This numerical superiority of exit lines from layers 80 and 81 on the lower surface of the 40th wing over exit lines from layers 82 and 83 on the upper surface of the 42nd wing is further observed in a broad region of dawn 30 extending from foot 32 to 70% of dawn height and even across the entire dawn 30th wing.Alternatively (not shown), the numerical superiority of layer 80, 81 exit lines on the lower surface of the wing (intrados 40) over layer 82, 83 exit lines on the upper surface of the wing (extrados 42) is observed only in the lower region of dawn 30 (i.e., the number of layer 80, 81 exit lines on the lower surface of the wing (intrados 40) is less than the number of layer 82, 83 exit lines on the upper surface of the wing (extrados 42) in an intermediate region of dawn 30 extending from 30% of dawn height to 70% of dawn height) or only in the lower and extended regions of dawn 30 (i.e., the number of layer 80, 81 exit lines on the lower surface of the wing (intrados 40) is less than the number of layer 82, 83 exit lines on the upper surface of the wing (extrados 42) in the region extending beyond 70% of the dawn height).As a further alternative (still not shown), the numerical superiority of the exit lines of layer 80, 81 at the intrados 40 over the exit lines of layer 82, 83 at the extrados 42 is observed in the extended region of dawn 30 but not in the lower region (i.e. the number of exit lines of layer 80, 81 at the intrados 40 is less than or equal to the number of exit lines of layer 82, 83 at the extrados 42 in the lower region of dawn 30 and greater than the number of exit lines of layer 82, 83 at the extrados 42 in the intermediate region) [to be confirmed]*.

[0057] This feature gives the Aube 30 improved resistance to "large bird" type impacts.

[0058] As seen on the Figures 5 And 6The layer exit lines 80, 81, 82, 83 include continuous layer exit lines 80, 82 and discontinuous layer exit lines 81, 83. Each continuous layer exit line 80, 82 consists of a single curve of class at least C1< running along the lower surface 40, respectively the upper surface 42, from the leading edge 44 to the trailing edge 46. Each discontinuous layer exit line 81, 83 comprises a first segment 85 consisting of a curve of class at least C1< running along the lower surface 40, respectively the upper surface 42, from the leading edge 44 to the leading edge 47 and a second segment 87 consisting of a curve of class at least C1< running along the lower surface 40, respectively the upper surface 42, from the leading edge 47 to the trailing edge 46.

[0059] Each continuous layer exit line 80, 82 has a vertex (unreferenced), consisting of the point on the layer exit line 80, 82 furthest from foot 32.

[0060] Each continuous layer exit line 80, 82 includes at least one transverse portion 90 extending globally along a transverse direction T substantially orthogonal to the local tangent to the warp strands 71. In other words, for each of the incomplete warp strands 75 opening onto the transverse portion 90, the transverse direction T is substantially orthogonal to the plane locally tangent to the warp column 73 to which said incomplete warp strand 75 belongs, that is to say to the plane tangent to said warp column 73 at the level of the terminal end 78 of the incomplete warp strand 75.

[0061] By "extends globally along a direction", it is understood here and in the following that the element concerned (here the transverse portion 90) is included in a band centered on said direction and of width equal to four times the mesh width of the fibrous reinforcement 62. In other words, said direction constitutes a median of the element concerned and each point of said element is distant from said direction by a distance less than or equal to twice the mesh width of the fibrous reinforcement 62.

[0062] By "approximately orthogonal", we understand here and in the following that the directions concerned form an angle between 85 and 95° with each other.

[0063] The transverse direction T is also substantially parallel to the local tangent to the weft strands 72. In other words, each of the weft strands 72 abutting the intrados 40 or the extrados 42 along the transverse direction T is substantially parallel to said transverse direction T over the entire extension of the transverse portion 90.

[0064] By "approximately parallel", we understand here and in the following that the directions concerned form an angle of less than or equal to 5° with each other.

[0065] A transverse portion 90 of each continuous layer exit line 80, 82 is constituted by a vertex portion 92 including the vertex of said layer exit line 80, 82. Each vertex portion 92 located between the foot 32 and 70% of 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.

[0066] In general, each transverse portion 90 located between the foot 32 and 70% of 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.

[0067] This management of the exit positions of the strands 71, 72 optimizes their robustness. Thus, the resistance of the blade 30 to "large bird" type impacts is reinforced.

[0068] Each discontinuous layer exit line 81, 83 includes at least one terminal portion 96 which extends from the blade head 38, in particular from the head edge 47, up to 90% of blade height, advantageously 60% of blade height.

[0069] This terminal portion 96 extends globally along an extension direction E forming an angle between 5° and 85° with the local tangent to the warp strands 71. In other words, for each of the incomplete warp strands 75 opening onto the terminal portion 96, the extension direction E forms an angle between 5° and 85° with the plane locally tangent to the warp column 73 to which said incomplete warp strand 75 belongs, that is to say with the plane tangent to said warp column 73 at the level of the terminal end 78 of the incomplete warp strand 75.

[0070] The extension direction E also forms an angle between 5° and 85° with the local tangent to the weft strands 72. In other words, for each of the incomplete weft strands 76 opening onto the terminal portion 96, the extension direction E forms an angle between 5° and 85° with the plane locally tangent to the weft column 74 to which said incomplete weft strand 76 belongs, that is to say with the plane tangent to said weft column 74 at the level of the terminal end 78 of the incomplete weft strand 76.

[0071] Each terminal portion 96 on the intrados side 40 also fulfills at least one of the following criteria at each of its points: the terminal portion 96 is spaced from the downstream edge to the intrados 57 of the shield 52 by a distance greater than or equal to three times the mesh width of the fibrous reinforcement 62, and the tangent to the terminal portion 96 forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to said downstream edge to the intrados 57 at the height of said point.

[0072] In other words, for any section of a terminal portion 96 on the intrados side 40 distant from the downstream edge to the intrados 57 of the shield 52 by a distance less than three times the mesh width of the fibrous reinforcement 62, the tangent to the terminal portion 96 at each point of said section forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to said downstream edge to the intrados 57 at the height of said point.

[0073] Each terminal portion 96 on the extrados side 42 also fulfills at least one of the following criteria at each of its points: the terminal portion 96 is spaced from the downstream edge to the extrados 58 of the shield 52 by a distance greater than or equal to three times the mesh width of the fibrous reinforcement 62, and the tangent to the terminal portion 96 forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to said downstream edge to the extrados 58 at the height of said point.

[0074] In other words, for any section of a terminal portion 96 on the extrados side 42 distant from the downstream edge to the extrados 58 of the shield 52 by a distance less than three times the mesh width of the fibrous reinforcement 62, the tangent to the terminal portion 96 at each point of said section forms an angle greater than or equal to 5°, advantageously greater than or equal to 15°, with the tangent to said downstream edge to the extrados 58 at the height of said point.

[0075] A majority of said terminal portions 96, here all terminal portions 96, are constituted by inclined terminal portions 98 whose extension direction E forms an angle between 10° and 65°, advantageously between 15° and 45°, with the local tangent to the warp strands 71. In other words, for each of the incomplete warp strands 75 opening onto an inclined terminal portion 98, the extension direction E of said inclined terminal portion 98 forms an angle between 10° and 65°, advantageously between 15° and 45°, with the plane locally tangent to the warp column 73 to which said incomplete warp strand 75 belongs, that is to say with the plane tangent to said warp column 73 at the level of the terminal end 78 of the incomplete warp strand 75.

[0076] For each inclined terminal portion 98, the extension direction E also forms an angle between 25° and 80°, advantageously between 45° and 75°, with the local tangent to the weft strands 72. In other words, for each of the incomplete weft strands 76 opening onto the inclined terminal portion 98, the extension direction E of said inclined terminal portion 98 forms an angle between 25° and 80°, advantageously between 45° and 75°, with the plane locally tangent to the weft column 74 to which said incomplete weft strand 76 belongs, that is to say with the plane tangent to said weft column 74 at the level of the terminal end 78 of the incomplete weft strand 76.

[0077] These characteristics give the Aube 30 enhanced resistance to "small bird" type impacts.

[0078] Thanks to the features of the embodiment described above, the mechanical behavior of a composite blade in the event of a bird or hailstone impact is improved. This allows the blade to be thinner while maintaining constant strength, thus reducing weight and improving aerodynamic performance.

Claims

1. A blade (30) for a turbomachine fan, comprising a root (32) configured to be attached to a fan disk (28) and a vane (34) capable of extending in an air flow and defining a blade head (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 head (38), said longitudinal direction (Y) being substantially orthogonal to a chord direction (C) extending from the leading edge (44) to the trailing edge (46), the blade (30) being composed at least in part of a structure (50) made of composite material comprising a fiber reinforcement (62) obtained by three-dimensional weaving and a matrix (64) in which the fiber reinforcement is embedded (62), the fiber reinforcement (62) comprising a plurality of intermingled plies (66, 68), each ply (66, 68) being formed of warp yarns (71) extending substantially orthogonally to the chord direction (C) and weft yarns (72) extending substantially orthogonally to the longitudinal direction (Y), the warp yarns (71) and weft yarns (72) including incomplete yarns (75, 76) that each have a terminal end (78) on the pressure side (40) or the suction side (42), the pressure side (40) and / or the suction side (42) having ply drop lines (80, 81, 82, 83) each connecting the terminal ends (78) of the incomplete yarns (75, 76) of a same ply (66, 68), wherein at least one ply drop line (80, 82) includes at least one transverse portion (90) located between the root (32) and 70% of the blade height, including an apex portion (92), characterized in that the or each transverse portion (90) extends generally along a transverse direction (T) substantially orthogonal to the local tangent to the warp yarns (71), the or each apex portion (92) 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).

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

3. The blade (30) according to claim 1 or 2, wherein the number of ply drop lines (80, 81) on the pressure side (40) is greater than the number of ply drop lines (82, 83) on the suction side (42) in a low region of the blade (30) comprised 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.

4. The blade (30) according to any one of the preceding claims, wherein the number of ply drop lines (80, 81) on the pressure side (40) is, over the entire blade (30), greater than the number of ply drop lines (82, 83) on the suction side (42).

5. The blade (30) according to any one of the preceding claims, wherein at least one ply drop line (81, 83) comprises a terminal portion (96) which extends from the blade head (38) up to 90% of the blade height, advantageously up to 60% of the blade height, the or each terminal portion (96) extending generally in a direction (E) of extension forming an angle comprised between 5° and 85° with the local tangent to the warp yarns (71).

6. The blade (30) according to claim 5, wherein, for the or each terminal portion (96), the direction (E) of extension forms an angle comprised between 5° and 85° with the local tangent to the weft yarns (72).

7. The blade (30) according to claim 5 or 6, wherein at least one terminal portion (96) is constituted by an inclined terminal portion (98) whose direction (E) of extension forms an angle comprised between 10° and 65°, advantageously comprised between 15° and 45° , with the local tangent to the warp yarns (71).

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

9. The blade (30) according to claim 7 or 8, wherein a majority of the terminal portions (96) are made up of inclined terminal portions (98).

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

11. The blade (30) according to any one of the preceding claims, wherein the root (32) is configured to be inserted into a cell of a fan disk (28), the blade (30) also comprising a stilt (36) connecting the root (32) to the vane (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 turbomachine (12) according to claim 13.