Mixing of fibers in fiber reinforcements for fan blades

Abstract

The present invention relates to a fan blade (3) made of composite material, wherein the fiber reinforcement of the fan blade includes a first strand (12) having a first stiffness, a second strand (13) having a second stiffness, and a third strand (14) having a third stiffness less than the first stiffness and greater than the second stiffness. The blade includes a first part (15), a second part (16), and a third part (17). The first part includes only the first strand (12), the second part includes only the second strand (13), and the third part is located between the first part and the second part (15, 16) and includes the first strand, the second strand, and the third strand (12, 13, 14). There is a gradual transition of properties at the interface between the different parts (15, 16, 17).

Description

Technical Field

[0001] This invention relates generally to the field of turbines, and more specifically to the field of fan blades of such turbines and methods of manufacturing such fan blades.

[0002] More specifically, the present invention applies to fan blades made of composite materials and the interaction between the fan blades and the inlet of the main flow. Background Technology

[0003] Turbine blades (especially fan blades) are subjected to large mechanical and thermal stresses and must meet stringent weight and volume requirements. Therefore, the use of blades made of composite materials, comprising fiber reinforcements densified from a polymer matrix, has been proposed. These blades are lighter than metal blades with equivalent propulsion properties and exhibit satisfactory heat resistance.

[0004] During engine certification and service life, fan blades are exposed to bird and hail attacks. However, the initial and favorable areas for damage propagation vary depending on the type of object impacting the blades (specifically, the size and mass of the object) and the type of fan (rotational speed and number of blades). Therefore, the mechanical properties of the fan blades are optimized during the blade design phase to meet certification requirements.

[0005] Furthermore, current designs tend to reduce the thickness of composite materials used in the blades in the leading-edge region, trailing-edge region, or even the entire structure to improve aerodynamic performance. However, this reduces the blades' ability to withstand impacts under the same materials and stacking rules.

[0006] To improve the resistance of blades to impacts, particularly bird strikes, the mixing of fibers in composite materials has been proposed. For example, it has been proposed to replace a portion of the carbon fiber reinforcement in a blade made of composite material with glass fiber, which forms the trailing edge of the reinforcement. This mixing allows for improved blade performance upon impact. However, given the variable thickness of the blade, managing the property transitions between fibers is complex and creates weakened regions at the carbon / glass fiber interface. Summary of the Invention

[0007] Therefore, one object of the present invention is to overcome the above-mentioned disadvantages by providing a fan blade for a turbine that improves performance when attacked without creating a weakened region.

[0008] Another object of the present invention is to improve the blending of blades made of composite materials, including fiber reinforcements densified by a matrix, in particular to smooth the performance gradient in a simple and effective manner, while improving the performance of the blades under attack.

[0009] Therefore, according to a first aspect, the present invention provides a turbine fan blade comprising a structure made of a composite material, the structure comprising a fiber reinforcement and a matrix obtained by three-dimensional weaving of strands, the fiber reinforcement being embedded in the matrix. The fiber reinforcement comprises a first portion and a second portion distinct from each other, the strands of the fiber reinforcement comprising first strands made of a first material having a first stiffness, and second strands made of a second material different from the first material, the second material having a second stiffness less than the first stiffness. The first portion comprises only the first strands, and the second portion comprises only the second strands. Furthermore, the fiber reinforcement also includes a third portion positioned between the first and second portions, the third portion simultaneously comprising the first, second, and third strands, the third strand having a third stiffness less than the first stiffness and greater than the second stiffness. Moreover, within the third portion, the volume density of the first strands gradually decreases from the first portion along the direction of the second portion, and the volume density of the second strands gradually decreases from the second portion along the direction of the first portion.

[0010] According to the first aspect, some preferred but non-limiting features of the fan blades are the following features, used alone or in combination:

[0011] - The third part includes a first section that contacts the first part, a second section that contacts the second part, and a central section that extends between the first section and the second section. The first section has no second line, and the second section has no first line.

[0012] - The central component only includes the third strand.

[0013] - The fan blade includes a first region, in which a second portion includes a blade shank and a suction sidewall, reaching a height between 0% and 30% of the airfoil height, the second portion extending along a chord from an upstream limiting portion and a downstream limiting portion, the upstream limiting portion extending at a distance from the leading edge of the blade, the distance being between 2% and 10% of the chord length, preferably about 7%, the downstream limiting portion extending at a distance from the trailing edge of the blade, the distance being between 10% and 60% of the chord length, preferably about 55%; and a third portion surrounding the second portion, while extending on both sides of the second portion along a chord length portion described below, the chord length portion being about 5% of the chord length;

[0014] - The fan blade includes a second region, in which a second portion includes a leading edge of the blade and a pressure sidewall, and the second portion extends at a height between 40% and 65% of the blade height and at a chord length between 20% and 40%, for example, about 40% of the chord length; and a third portion extends from the leading edge in the direction of the pressure sidewall while surrounding the second portion at a length equal to 50% of the chord length;

[0015] - The second and third portions each extend at a thickness equal to one-third of the thickness of the fiber reinforcement;

[0016] - The fan blade includes a third region in which the second portion includes the trailing edge of the blade and extends over all or part of the height of the airfoil and over a length equal to at most 10% of the chord length; the third portion is adjacent to the second portion and extends along the second portion over a length equal to at most 10% of the chord length; and the second and third portions each extend over the entire thickness of the fiber reinforcement.

[0017] - The first, second, and third strands include the meridian strands that are distributed to form a meridian column;

[0018] - The fan blade includes a fourth region in which a second portion includes the tip and trailing edge of the blade and extends over a height of at most 10% of the blade height and a length between 40% and 100% of the chord length; a third portion extends from the tip of the blade over the entire length of the second portion and over a height of at most 5% of the blade height; and the second and third portions each extend over the entire thickness of the fiber reinforcement.

[0019] -Among them, the first strand, the second strand, and the third strand include latitude strands distributed to form latitude rows;

[0020] - The fiber reinforcement includes only one first part, one or more second parts, and one or more third parts;

[0021] - The elastic modulus of the first strand is between 240 GPa and 350 GPa, preferably greater than or equal to 250 GPa, and the first strand can include carbon fiber;

[0022] - The elastic modulus of the second strand is between 150 GPa and 190 GPa, and the second strand may comprise glass fiber or basalt fiber; and / or

[0023] - The elastic modulus of the third strand is between 180 and 250 GPa, and the third strand can include aramid fibers.

[0024] According to a second aspect, the present invention relates to a turbine fan comprising a plurality of fan blades according to a first aspect.

[0025] According to a third aspect, the present invention proposes a turbine including this type of fan and an aircraft including such a turbine.

[0026] According to a fourth aspect, the present invention provides a fiber reinforcement for use in fan blades according to the first aspect. Attached Figure Description

[0027] Other features, objects, and advantages of the invention will be revealed by the following description, which is purely illustrative and non-limiting and must be read with reference to the accompanying drawings, in which:

[0028] Figure 1 This is a schematic diagram illustrating an example of a fiber reinforcement for a fan blade according to one embodiment, showing a plurality of potential mixed regions of the fibers of the fiber reinforcement according to one embodiment of the invention, including a transparent region (18);

[0029] Figure 2 It is a fiber-reinforced member along Figure 1 A cross-sectional view of plane AA;

[0030] Figure 3 It is a fiber-reinforced member along Figure 1 A cross-sectional view of plane BB;

[0031] Figure 4 This is a simplified schematic diagram illustrating an example of the mixing of the first, second, and third strands within a third portion of the fiber reinforcement according to the invention; and

[0032] Figure 5 This is a perspective view of an exemplary embodiment of a fan including blades according to the present invention.

[0033] In all the accompanying drawings, similar elements have the same reference numerals. Detailed Implementation

[0034] In this application, upstream and downstream are defined with reference to the normal flow direction of gas through the turbine in fan 1. Furthermore, the radial axis of symmetry X of fan 1 is referred to as the axis of rotation of fan 1. The axial direction corresponds to the direction of axis X of fan 1, and the radial direction is the direction perpendicular to and passing through this axis.

[0035] The turbine fan 1 includes a fan disk 2 that carries a plurality of fan blades 3 associated with an inter-blade platform.

[0036] Each blade 3 includes a structure made of composite material, comprising: a fiber reinforcement 4 obtained by three-dimensional weaving; and a matrix in which the fiber reinforcement 4 is embedded.

[0037] This composite material structure includes a root 5, a shank 6, and an airfoil 7 with an aerodynamic profile. The root 5 is designed to allow the blades 3 to attach to the fan disk 2, and for this purpose extends between the bottom of a recess formed in the disk 2 and the outlet of the recess's span. The airfoil 7 with its aerodynamic profile is, in itself, positioned in the airflow to generate lift during turbine operation. Finally, the shank 6 corresponds to region 20e of the airfoil 7, which extends between the root 5 and the airfoil 7, i.e., between the outlet of the span and the platform between the blades 3. Therefore, the shank 6 is not configured to extend into the airflow.

[0038] The blade 3 also includes, in a manner known per se, a leading edge 8, a trailing edge 9, a pressure-side I wall, and a suction-side E wall. The leading edge 8 is configured to extend towards the gas flow entering the turbine. The leading edge corresponds to a front portion with an aerodynamic profile that faces the air flow and splits the flow into a pressure-side I flow and a suction-side E flow. The trailing edge 9, in itself, corresponds to a rear portion with an aerodynamic profile, in which the pressure-side I flow and the suction-side E flow re-merge.

[0039] Finally, the structure is formed by multiple blade segments 3, which are stacked from the bottom 5 along a stacking axis that extends radially relative to the rotation axis X of the fan 1.

[0040] In the following text, the distance along the stacking axis Z will be designated as "height". Therefore, the height H of the airfoil 7 corresponds to the distance along the stacking axis Z between the lower limiting portion 10 of the airfoil intersecting with the shank 6 and the tip 11 of the airfoil. The height H of the airfoil 7 is measured at the intersection of the leading edge 8 and the lower limiting portion 10 of the airfoil 7.

[0041] The fiber reinforcement 4 can be formed as a single piece from a fiber preform, which is obtained through three-dimensional or multi-layer weaving with varying thickness. The fiber reinforcement comprises warp and weft strands, which may specifically include carbon, glass, basalt, and / or aramid fibers. The matrix is ​​typically a polymer matrix, such as epoxy resin, bismaleimide, or polyimide. The blade 3 is then formed by molding using a vacuum resin injection method of the type Resin Transfer Molding (RTM) or Vacuum Resin Transfer Molding (VARRTM).

[0042] Figure 1The blade 3 is schematically shown. To obtain the fan 1 blade 3 made of composite material according to the invention, the fiber reinforcement 4 of the blade has been formed from a three-dimensionally woven fiber preform before resin injection or by matrix densification and possible machining. Three-dimensional weaving means that the warp strands follow a winding trajectory to connect the weft strands belonging to different weft strand layers together, except in unbonded areas. It should be noted that three-dimensional weaving (especially three-dimensional weaving with interlocking patterns) can include 2D weaving of the surface. Different three-dimensional weaving patterns can be used, such as interlocking patterns, multi-satin patterns, or multi-grid patterns, as specifically described in document WO 2006 / 136755.

[0043] The strands of fiber reinforcement 4 include:

[0044] - A first strand 12 made of a first material having a first stiffness;

[0045] - A second strand 13 is made of a second material different from the first material, the second material having a second stiffness less than the first stiffness; and

[0046] - A third strand 14 is made of a third material different from the first and second materials. The third material also has a third stiffness that is greater than the second stiffness and less than the first stiffness.

[0047] As a non-limiting example, the first strand 12 may be made of a material with a stiffness E (tensile modulus of elasticity or first stiffness) between 240 GPa and 350 GPa, the second strand 13 may be made of a material with a stiffness E (or second stiffness) between 150 GPa and 190 GPa, and the third strand 14 may be made of a material with a stiffness E (or third stiffness) between 180 GPa and 250 GPa. The factor between the values ​​of the first stiffness E and the second stiffness E may, for example, be between 1.5 and 2. The factor between the values ​​of the first stiffness E and the third stiffness E may, for example, be between 1.5 and 1.2.

[0048] As an example, the first strand 12 may be made of carbon fiber with a first stiffness E greater than or equal to 250 GPa, the second strand 13 may be made of glass fiber with a second stiffness E of about 165 GPa, and the third strand 14 may be made of aramid fiber with a third stiffness of about 200 GPa.

[0049] The breaking elongation of the first strand can be between 1.5 and about 2.5, for example, about 2. The breaking elongation of the second strand can be between about 4 and about 6, for example, about 5. The breaking elongation of the third strand can be between about 2.5 and about 3. Typically, in the strand transition region, a maximum 30% breaking elongation loss gradient along one direction over 15 mm to 20 mm is considered, and / or a maximum 30% breaking elongation loss gradient along that direction or the other direction over 15 mm to 20 mm.

[0050] The first strand 12, the second strand 13, and the third strand 14 are distributed in the fiber preform to form the first part 15, the second part 16, and the third part 17, thereby:

[0051] - Part 15 only includes the first line 12;

[0052] - Part 16 is separate from and different from Part 15, and includes only the second line 13; and

[0053] - The third part 17 is positioned between the first part 15 and the second part 16, and includes the third line 14.

[0054] In addition, in order to smooth the performance gradient between the first part 15 and the second part 16, the third part 17 includes the first line 12 and the second line 13 in addition to the third line 14. It should be noted that in the third part 17, the volume density of the first line 12 gradually decreases from the first part 15 along the direction of the second part 16, and the volume density of the second line 13 gradually decreases from the second part 16 along the direction of the first part 15.

[0055] In one embodiment, the fiber reinforcement 4 includes only one first part 15, one or more second parts 16, and one or more third parts 17.

[0056] Optionally, the fiber reinforcement 4 may include a plurality of second portions, which are different from each other and are separated from the first portion 15 in pairs by an associated third portion 17.

[0057] More precisely, the first strand 12 has a high elastic modulus, for example, greater than 250 GPa, and the function of the first strand is to enable the design specifications of the blade 3 to be met, particularly the frequency state of the blade 3. Therefore, the first portion 15 forms the main part of the fiber reinforcement 4, particularly the portion of the fiber reinforcement 4 that generally includes the low and thick portion of the blade 3 (i.e., the root 5, shank 6, and lower portion of the airfoil 7 of the blade 3), and the main part of the suction side wall E of the blade 3, resulting in a higher natural frequency of the blade 3. Therefore, this allows for the limitation or at least separation of the frequency intersection between the first energy natural mode of the blade 3 and the engine harmonics.

[0058] The second strand has a lower stiffness (elastic modulus E) than the first strand 12. The function of the second strand is to limit the initiation and propagation of damage to the blade 3 during an attack by an object (particularly a bird). One or more second portions 16 thus form one or more portions of the reinforcement 4 that may be subjected to load in the event of an object attack. Typically, and as will be described in detail below, in cases where the blade 3 may receive impacts from heavy birds (“large birds”), the second portion 16 extends on a portion of the leading edge 8 (in the central region of the blade 3, at a distance from the lower limiting portion 10 and from the tip 11 of the blade and on the pressure side I) (region 18) and / or on the suction side E at the shank 6 (region 19). Furthermore, when the blade 3 may receive impacts from medium-sized birds, the second portion 16 extends over the entire thickness of the blade 3 on all or part of the trailing edge 9 (region 20) and / or at the tip 11 of the blade 3 (region 21). Of course, Part 2, Section 16, can extend over all or part of Regions 18-21.

[0059] One or more third portions 17 extend between the first portion 15 and the second portion 16 and are configured to serve as an interface between the first portion 15 and the second portion 16 to limit weakening due to material discontinuities. When the strands of the fiber reinforcement 4 include only the first strand 12 in the first portion 15 of the blade 3 and only the second strand 13 in the second portion 16 of the blade 3, and the first portion 15 and the second portion 16 are connected end-to-end in the reinforcement 4, the resulting blade 3 effectively avoids damage to the blade 3 in the regions 18-21 including the second strand 13. However, the applicant has noted that without the third portion 17, i.e., by abruptly introducing the second strand 13 at the interface between the first portion 15 and the second portion 16 of the fiber reinforcement 4 while simultaneously eliminating the first strand 12, the resulting blade 3 is at risk of severe damage at that interface upon impact, because the interface between the two portions 11, 12 of the reinforcement 4 is weakened due to the strong discontinuity in material properties. Considering the large difference between the corresponding stiffness of the first strand 12 and the corresponding stiffness of the second strand 13, a simple mixture of the first strand 12 and the second strand 13 cannot sufficiently smooth the performance gradient. Therefore, smoothing is achieved by introducing a third strand 14 in the third part 17 and by the gradual decrease in the volume density of the first strand 12 and the second strand 13 in the third part 17.

[0060] Therefore, the third part 17 allows for a smooth and regular transition between the material properties of the first part 15 and the second part 16. For this purpose, the bulk density of the second strand 13 gradually increases within the third part 17 from the first part 15 towards the second part 16. Thus, at the interface between the first part 15 and the third part 17, the bulk density of the second strand 13 is zero, the bulk density of the third strand 14 is low, and the bulk density of the first strand 12 is very high. Conversely, at the interface between the third part 17 and the second part 16, the bulk density of the second strand 13 is very high, while the bulk density of the first strand 12 is zero, and the bulk density of the third strand 14 is low.

[0061] To optimize the resistance of blade 3 to impact, in addition to region 21 including blade tip 11, the second strand 13 is the warp strand of reinforcement 4 (i.e., a strand extending along the stacking axis Z of blade 3 segment). In fact, in regions 18-20, damage (or breakage of blade 3) begins in the chord direction and cracks in the radial direction, so the strength of the reinforcement must be increased in the warp direction.

[0062] On the other hand, in region 21 including the tip 11 of blade 3, the second strand 13 includes a weft strand.

[0063] In region 18, the second portion 16 extends at the leading edge 8 over a chord length portion described below, which is between 10% and 50% of the total chord C of the blade 3. Preferably, the chord length portion C is between 20% and 40% of the total chord C of the blade 3, for example, about 40%. For a given segment of the blade 3 (and therefore for a given point on the stacking axis Z), the chord C here refers to the generally axial straight line segment connecting the leading edge 8 of the blade 3 to the trailing edge 9 of the blade 3.

[0064] As previously described, the second portion 16 extends only a portion of the height of the airfoil 7 in the central region of the blade 3. In one embodiment, the lower edge of the second portion 16 is at a distance at least equal to 10% of the height H of the blade 7 (measured from the lower limit 10 of the blade 3), preferably at a distance approximately equal to 40% of that height H. Furthermore, the upper edge of the second portion 16 is at a distance at most equal to 70% of the height H of the airfoil 7 (measured from the lower limit 10 of the blade 3), preferably at a distance approximately equal to 65% of that height H.

[0065] In one exemplary embodiment, to optimize the blade 3's resistance to large bird strikes, the lower edge of the second portion 16 is located at a distance equal to 40% of the height H of the airfoil 7, and the upper edge of the second portion 16 is located at a distance equal to 65% of the height H (these distances are measured from the lower limiting portion 10 of the blade 3). This exemplary embodiment makes it possible to improve the performance of the blade 3 in the event of a large bird strike, and also facilitates the manufacture of the blade and limits the additional spread caused by the second strand 13 having a smaller elastic modulus than the first strand 12.

[0066] Furthermore, the second portion 16 is positioned at the pressure side wall I and does not extend to the suction side wall E. Therefore, in region 18, the second portion 16 does not extend over the entire thickness of the fiber reinforcement 4, but only at the skin of the fiber reinforcement.

[0067] In region 18, the third portion 17 is then positioned to form an interface at each point between the second portion 16 and the first portion 15. Therefore, except at the pressure-side I wall (where the second portion 16 forms the pressure-side I wall), the second portion 16 is enclosed within the third portion 17. Thus, the third portion 17:

[0068] - Between the lower edge of the second part 16 and the handle 6, it extends on the following part, the height of which may be between 5% and 10% of the height H of the airfoil 7;

[0069] - Between the upper edge of the second part 16 and the tip 11, it extends on the following portion, the height of which may be between 5% and 10% of the height H of the airfoil 7;

[0070] - The second part 16 extends along the direction of the leading edge 8 and the trailing edge 9 on both sides of the chord length portion C, which is approximately 5% of the chord length C; and

[0071] - It extends between the second section 16 and the suction side wall E at a thickness (the dimension along the axis perpendicular to the stack axis and substantially perpendicular to the pressure side wall I at the measurement point) equal to one-third of the total thickness of the fiber reinforcement 4.

[0072] like Figure 3 As shown, in region 18, the leading edge 8 thus includes a second portion 16, a third portion 17 and a first portion 15 sequentially from the pressure side wall I to the suction side wall E. The thickness of each of these portions 15, 16, 17 (in a plane perpendicular to the stacking axis Z intersecting the third portion 17) is approximately equal to one-third of the total thickness of the fiber reinforcement (in that plane).

[0073] In region 19, the second portion 16 extends along a chord length portion (described below) at a distance from the leading edge 8 and the trailing edge 9, the chord length portion being between 10% and 50% of the total chord length C of the blade 3. Preferably, the chord length portion C is between 30% and 40% of the total chord length C of the blade 3, for example, about 38%. Furthermore, the upstream limiting portion (towards the leading edge 8) of the second portion 16 extends at a distance from the leading edge 8, the distance being between 2% and 10% of the chord length C, preferably about 7%, and the downstream limiting portion (towards the trailing edge 9) of the second portion 16 extends at a distance from the trailing edge 9, the distance being between 10% and 60% of the chord length C, preferably about 55%.

[0074] As previously described, the second portion 16 extends only over a portion of the height H of the airfoil 7 in the lower region of the blade 3. In one embodiment, the second portion 16 extends from the shank 6 to a height less than or equal to 30% of the height H of the airfoil 7.

[0075] The second portion 16 is also positioned at the suction side wall E and does not extend to the pressure side wall I. The thickness of the second portion 16 is between 10% and 40% of the thickness of the fiber reinforcement 4, preferably about one-third of the total thickness. Therefore, in region 19, the second portion 16 does not extend over the entire thickness of the fiber reinforcement 4, but only at the skin of the fiber reinforcement.

[0076] In region 19, the third portion 17 is then positioned to form an interface at each point between the second portion 16 and the first portion 15. Therefore, except at the suction side E-wall (where the second portion 16 is on the skin), the second portion 16 is encapsulated within the third portion 17. Thus, the third portion 17:

[0077] - Between the lower edge of the second part 16 and the root 5, it extends on the following part, the height of which may be between 5% and 10% of the height H of the airfoil 7;

[0078] - Between the upper edge of the second part 16 and the tip 11, it extends on the following portion, the height of which may be between 5% and 10% of the height H of the airfoil 7;

[0079] - The second part 16 extends along the direction of the leading edge 8 and the trailing edge 9 on both sides of the chord length portion C, which is approximately 5% of the chord length C; and

[0080] - It extends between the second part 16 and the pressure side I wall at a thickness described below, which (in a plane perpendicular to the stacking axis Z intersecting the third part 17) is equal to one-third of the total thickness of the fiber reinforcement 4 (in that plane).

[0081] In region 20, the second portion 16 extends at any point on the stacking axis Z of the blade 3 along the chord length portion C described below, which is approximately 10% of the total chord length C.

[0082] Preferably, the second portion 16 extends from the tip 11 of the blade 3. Ideally, in order to optimize the resistance of the blade 3 to bird strikes, the second portion 16 extends generally over the entire height of the blade 3, that is, from the tip 11 of the blade 3 to the root 5 (or as a variant to the stalk 6).

[0083] In a variant embodiment, to simplify the identification of the root 5 / stem 6 region of the blade 3 and to improve the performance of the trailing edge 9 against intrusions by all types of objects (large birds, medium birds, and small birds), the second portion 16 may extend only a portion of the height of the airfoil 7 to its lower edge, which extends at a distance between 0% (in the case where the second portion 16 extends over the entire airfoil 7) and 65% of the height H of the airfoil 7. Therefore, the height of the second portion 16 in region 20 is between 35% and 100% of the height G of the airfoil 7.

[0084] In another variant embodiment, the distance between the lower limiting portion 10 of blade 3 and the lower edge of the second portion 16 (along the stacking axis Z of blade 3) is greater than 65% of the height H of airfoil 7. Therefore, the height of the second portion 16 is less than 35% of the height H of airfoil 7. This second variant embodiment facilitates manufacturing and limits the additional spread caused by the stiffness of the second strand 13 being less than that of the first strand 12. However, compared to the first embodiment, the improvement in performance of the trailing edge 9 relative to the intrusion of medium-sized and small-sized bird types is smaller.

[0085] Therefore, the dimensions of the blade 3 allow for the determination of a distance from which the second strand 13 is introduced into the fiber reinforcement 4 to combine the necessary stiffness for the frequency state (first strand 12) and the elongation at break for resistance to attack (second strand 13).

[0086] In region 20, the second part 16 extends over the entire thickness of the fiber reinforcement 4, from the pressure side wall I to the suction side wall E.

[0087] In region 20, a third portion 17 is then positioned to form an interface at each point between the second portion 16 and the first portion 15. Therefore, the third portion 17 extends from the second portion 16 and the tip 11 of the blade 3, extends over the entire thickness of the fiber reinforcement 4, and extends between the lower edge and the root 5 of the second portion 16. Thus, the third portion 17:

[0088] - Between the lower edge of the second part 16 and the root 5, it extends on the following part, the height of which may be between 5% and 10% of the height H of the airfoil 7;

[0089] - Extending from the second portion 16 along the direction of the leading edge 8 on the chord length portion C described below, the chord length portion being approximately 10% of the chord length C; and

[0090] - Extends over the entire thickness of fiber reinforcement 4.

[0091] In region 21, the second portion 16 extends from the trailing edge 9 and includes a tip 11 over the entire thickness of the reinforcement 4, specifically in the chord length portion described below, which is between 40% and 100% of the total chord C of the blade 3. Preferably, the chord C portion is between 40% and 80% of the total chord C of the blade 3.

[0092] Furthermore, the second part 16 extends at 5% to 10% (preferably about 5%) of the height H of the airfoil 7.

[0093] In region 19, the third portion 17 is then positioned to form an interface at each point between the second portion 16 and the first portion 15. Therefore, the second portion 16 is defined by the third portion 17. Thus, the third portion 17:

[0094] - Extends over a portion between the lower edge of the second part 16 and the root 5, the height of which may be between 5% and 10% of the height H of the airfoil 7, preferably about 5%;

[0095] - Extending from the second part 16 along the direction of the leading edge 8 on the chord length portion described below, the chord length portion being approximately 5% of the chord length C; and

[0096] - Extends over the entire thickness of fiber reinforcement 4.

[0097] The geometry of the second part 16 in regions 18-21 can be arbitrary. In fact, as mentioned above, regions 18-21 allow for the modification of the mechanical properties of the blade 3 in areas where lamellae may form. Therefore, the geometry of regions 18-21 can be selected based on testing or simulation that allows for the identification of regions most likely to form lamellae for the fiber texture under consideration.

[0098] When the fiber reinforcement 4 includes the second portion 16 and the third portion 17 in regions 20 and 21, then the fiber reinforcement includes a third strand 14 in the warp and weft directions in the overlapping portions of these regions 20 and 21.

[0099] The change in the volume density of the first strand 12, the second strand 13, and the third strand 14 can be achieved by continuously entering / leaving the preform weave at different warp planes (in regions 18-20) or weft planes (in region 21) constituting the third part 17, such as... Figure 4 As schematically illustrated, typically at the interface between the first and second portions 17, the first strand 12 is gradually removed by cutting the first strand 12 on the surface of the preform before injection and by simultaneously introducing a third strand 14 between these warp (and corresponding weft) planes. Similarly, at the interface between the third and second portions 16, the third strand 14 is gradually removed while a second strand 13 is simultaneously introduced between these warp (and corresponding weft) planes. In this way, the first portion 15, the second portion 16, and the intermediate portion 16 are formed from a single component during the weaving process.

[0100] For an exemplary embodiment of the mixing of meridian strands, please refer to the applicant's document FR 3087701. The same operating mode can be implemented for latitude strands (region 21).

[0101] Typically, the described configuration is effective for engines whose fans can have an outer diameter of approximately 1.8 to 3 meters. The number of fan blades 3 can be either 16 or 18. Regardless of the fan diameter, the number of fan blades 3 will be minimized as much as possible. In different standards, the selection of parameters (particularly regions 18, 19, 20, and / or 21 including the second and third sections) will depend more specifically on the performance of the fan blades 3 and the "intrusion frequency / size" combination. In fact, for the same engine target, different strategies for frequency performance or frequency response can be selected under different intrusion conditions, for example, by avoiding the intersection of vibrations with the engine's energy harmonics to push back the blades 3 and blade response. For example, a selection can be made to position the intersection at the instantaneous engine speed.

[0102] The mixing of strands in the fiber reinforcement 4 also broadens the design scope due to the additional contribution to mechanical strength. For example, compared to a blade 33 containing only the first strand 12 (with a high elastic modulus), the profile of the blade 3 can be improved at the leading edge 8 of the preform 4, or at the trailing edge 9 of the preform 4, or along the entire height H of the airfoil 7. This allows for optimization of the mass of the blade 3 and the aerodynamic performance of the fan 1 (by obtaining a thinner profile or by reducing the hub ratio, which relates to reducing the centrifugal force caused by the mass of the blade 3).

Claims

1. A turbine fan blade (3), the turbine fan blade comprising a structure made of a composite material, the structure comprising: A fiber reinforcement (4) obtained by three-dimensional weaving of strands, and a matrix, wherein the fiber reinforcement (4) is embedded in the matrix, the fiber reinforcement (4) comprising a first part (15) and a second part (16) that are different from each other, wherein the strands of the fiber reinforcement (4) comprise a first strand (12) made of a first material having a first stiffness, and a second strand (13) made of a second material different from the first material having a second stiffness less than the first stiffness, wherein the first part (15) comprises only the first strand (12), and the second part (16) comprises only the second strand (13). The turbine fan blade (3) is characterized in that the fiber reinforcement (4) further includes a third portion (17) positioned between the first portion (15) and the second portion (16), the third portion (17) comprising a first strand (12), a second strand (13), and a third strand (14), the third strand (14) having a third stiffness less than the first stiffness and greater than the second stiffness. Furthermore, within the third part (17), the volume density of the first strand (12) gradually decreases from the first part (15) along the direction of the second part (16), and the volume density of the second strand (13) gradually decreases from the second part (16) along the direction of the first part (15).

2. The turbine fan blade (3) according to claim 1, wherein, The third part (17) includes a first section that contacts the first part (15), a second section that contacts the second part (16), and a central section that extends between the first section and the second section. The first section has no second strand (13), and the second section has no first strand (12).

3. The turbine fan blade (3) according to claim 2, wherein, The central area only includes the third line (14).

4. The turbine fan blade (3) according to any one of claims 1 to 3, wherein the turbine fan blade includes a first region (18), in which: - The second part (16) includes the shank (6) and suction sidewall (E) of the turbine fan blade (3), reaching a height (H) between 0% and 30% of the height (H) of the airfoil, and the second part extends along a chord (C) from the upstream and downstream limiting portions, the upstream limiting portion extending at a distance from the leading edge (8) of the turbine fan blade (3), the distance being between 2% and 10% of the chord (C) length, and the downstream limiting portion extending at a distance from the trailing edge (9) of the turbine fan blade (3), the distance being between 10% and 60% of the chord (C) length; and - The third part (17) surrounds the second part (16) and extends on both sides of the second part (16) at a chord (C) length of 5% of the chord (C) length.

5. The turbine fan blade (3) according to any one of claims 1 to 3, wherein the turbine fan blade includes a second region (19), in which: - The second portion (16) includes the leading edge (8) and pressure sidewall (I) of the turbine fan blade (3), extending at a height (H) between 40% and 65% of the height (H) of the turbine fan blade (3) and at a chord (C) portion between 20% and 40% of the chord (C) length; and - The third portion (17) extends from the leading edge (8) along the direction of the pressure sidewall (I) and surrounds the second portion (16) in a portion whose length is equal to 50% of the chord (C) length.

6. The turbine fan blade (3) according to claim 4, wherein, The second part (16) and the third part (17) each extend on a thickness equal to one-third of the thickness of the fiber reinforcement (4).

7. The turbine fan blade (3) according to any one of claims 1 to 3, the turbine fan blade comprising a third region (20), in which: - The second part (16) includes the trailing edge (9) of the turbine fan blade (3) and is located on all or part of the height (H) of the airfoil and on a length of at most 10% of the chord (C) length; - The third portion (17) is adjacent to the second portion (16) and extends along the second portion (16) for a length at most 10% of the length of the chord (C); and - The second part (16) and the third part (17) each extend over the entire thickness of the fiber reinforcement (4).

8. The turbine fan blade (3) according to any one of claims 1 to 3, wherein, The first line (12), the second line (13) and the third line (14) include meridian lines distributed to form a meridian column.

9. The turbine fan blade (3) according to any one of claims 1 to 3, the turbine fan blade comprising a fourth region (21), in which: - The second part (16) includes the tip (11) and trailing edge (9) of the turbine fan blade (3), and at a height (H) of at most 10% of the height (H) of the turbine fan blade (3) and at a length between 40% and 100% of the chord (C) length; - The third portion (17) extends from the tip (11) of the turbine fan blade (3) over the entire length of the second portion (16) and at most 5% of the height (H) of the turbine fan blade (3); and - The second part (16) and the third part (17) each extend over the entire thickness of the fiber reinforcement (4).

10. The turbine fan blade (3) according to claim 9, wherein, The first, second and third strands (14) include latitude strands distributed to form latitude rows.

11. The turbine fan blade (3) according to any one of claims 1 to 3, wherein, The fiber reinforcement (4) includes only one first part (15), one or more second parts, and one or more third parts.

12. The turbine fan blade (3) according to any one of claims 1 to 3, wherein, The elastic modulus of the first strand (12) is between 240 GPa and 350 GPa, and the first strand (12) can include carbon fiber.

13. The turbine fan blade (3) according to any one of claims 1 to 3, wherein, The elastic modulus of the second strand (13) is between 150 GPa and 190 GPa, and the second strand (13) may include glass fiber or basalt fiber.

14. The turbine fan blade (3) according to claim 12, wherein, The elastic modulus of the third strand (14) is between 180 and 250 GPa, and the third strand (14) may comprise aramid fibers.

15. The turbine fan blade (3) according to claim 4, wherein, The upstream limiting portion extends at a distance from the leading edge (8) of the turbine fan blade (3), the distance being 7% of the chord (C) length.

16. The turbine fan blade (3) according to claim 4, wherein, The downstream limiting portion extends at a distance from the trailing edge (9) of the turbine fan blade (3), the distance being 55% of the chord (C) length.

17. The turbine fan blade (3) according to claim 5, wherein, The second portion extends at a height (H) between 40% and 65% of the height (H) of the turbine fan blade (3) and at a chord (C) portion that is 40% of the chord (C) length.

18. The turbine fan blade (3) according to claim 12, wherein, The elastic modulus of the first strand (12) is greater than or equal to 250 GPa.

19. A turbine fan comprising a plurality of turbine fan blades (3) according to any one of claims 1 to 18.

20. A fiber reinforcement for use in a turbine fan blade (3) according to any one of claims 1 to 18.

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