Hybrid metal / composite blade with fabric orientation adapted to mechanical stresses

Abstract

The invention relates to a blade (1) made of composite material, comprising a fiber reinforcement material, which is densified by an organic matrix and provided with a metal element (5) in an attachment area (4), the blade being characterized in that, in at least one zone of the attachment area, the reinforcement material comprises a surface fabric orientation adapted to the mechanical stress direction by having a first skin thread extending in the main mechanical stress direction (DA) and bonded to a second skin thread transverse to the first skin thread, the first skin thread occupying the majority of the surface area of ​​said zone of said attachment area.

Description

Technical Field

[0001] The present invention relates to a blade made of a composite material with an organic matrix (hereinafter referred to as "CMO material"), which is provided with a metal element and whose fabric orientation is adapted to the mechanical stresses acting on all or part of the attachment area to this element in order to reduce the risk of separation of the latter. Background Art

[0002] It is known to use components made of CMO materials to produce cold section elements of aircraft turbines, such as fan blades. It is also known to add metal elements to composite materials to improve their properties, for example to glue a protective metal foil on the leading edge of a fan blade to increase resistance to impacts encountered in operation (bird strikes, hail or debris). However, the stresses applied during operation can in some cases lead to the separation of metal elements. The present invention aims to overcome this problem. Summary of the invention

[0003] The invention relates to a blade made of composite material, comprising a fiber reinforcement densified by an organic matrix and provided with a metal element in the attachment area,

[0004] The blade is characterized in that in at least one zone of the attachment area, the reinforcement material includes a surface fabric orientation, which is adapted to the direction of the mechanical stress by having a first skin line, which extends along the main mechanical stress direction and is bonded to a second skin line transverse to the first skin line, and the first skin line is in the majority on the surface of the zone of the attachment area.

[0005] The inventors have noticed that the thread orientation on the surface of the reinforcement material on the attachment area affects the adhesion of the metal element to the CMO material during operation. Therefore, the present invention proposes to preferentially use first skin threads oriented in the direction of the main stress on the entire or part of the attachment area to reduce the risk of separation of the metal element.

[0006] The principal stress directions depend on the type of blade and metal element under consideration and can be easily determined by a person skilled in the art. The principal stress directions may correspond to the axial direction of the blade (corresponding to the direction of the chord length of the blade and the direction of the airflow), or to the radial direction of the blade or vane (corresponding to the direction of the axis connecting the root to the tip of the blade).

[0007] In an exemplary embodiment, in the region of the attachment area, the proportion of the first skin line on the surface is at least equal to twice the proportion of the second skin line on the surface.

[0008] Such examples apply in particular to mechanical stresses which are applied predominantly in a given direction.

[0009] In an exemplary embodiment, the fiber reinforcement material is woven in such a way that, at least in the skin, a progressive weave is formed between said regions of the attachment area and regions of the blade located outside the attachment area.

[0010] In this case, the reinforcement can be locally adjusted to improve the grip of the metal element without modifying the reinforcement outside the attachment area. The fabric can therefore be designed differently inside and outside the attachment area to achieve the best performance.

[0011] In an exemplary embodiment, the attachment area includes a first region having a first surface line at a first ratio, and a second region, different from the first region, having the first surface line at a second ratio different from the first ratio.

[0012] This example is particularly suitable for situations where the orientation of the mechanical stress varies greatly in the attachment area, thereby further reducing the risk of separation of the metal element. According to this example, the first line is in the majority in the first zone, but it is more likely that in the second zone, the first line can always be in the majority, or the second line can be in the majority. In particular, in the second zone, the ratio of the first line to the second line can be balanced, about 50 / 50.

[0013] Different examples of blades to which the present invention may relate are discussed below.

[0014] In an exemplary embodiment, the metal element is a protective foil covering the leading edge of the blade, and the main mechanical stress direction corresponds to the axial direction of the blade. In particular, the blade may be a fan blade. According to a variant, the blade is an outlet guide vane ("OGV").

[0015] According to another example, the blade defines an internal cavity and the metal element is a vane inserted into the internal cavity, the main mechanical stress direction corresponds to the radial direction of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] Figure 1 is a cross-sectional view of an example of a blade according to the invention, taken in a direction transverse to the radial direction, the blade being provided with a protective metal foil.

[0017] [ Figure 2 ] Figure 2 The plane transverse to the axial direction is shown. Figure 1 Detail of the fiber reinforcement of the blade located in the attachment area.

[0018] [ Figure 3 ] Figure 3 A variant of a blade according to the invention is shown. DETAILED DESCRIPTION

[0019] Figure 1 There is shown a blade 1 comprising a CMO material 3 provided with a protective metal foil 5. In general, the blade 1 may be a rotating blade or a stationary blade. Figure 1 The example relates to a rotating blade, here a fan blade. The CMO material 3 comprises: a fiber-reinforced material 10, the structure of which will be described below, and which is densified by an organic matrix. By way of example, the fiber-reinforced material 10 can be formed by carbon filaments, and the matrix can be an epoxy resin. However, the person skilled in the art will recognize that: depending on the application under consideration, other materials can be used. The CMO material 3 has a leading edge 13 at the upstream end and a trailing edge 33 at the downstream end, and an aerodynamic profile 23 between the leading edge 13 and the trailing edge 33. Unless otherwise specified, the terms "upstream" and "downstream" are relative to the direction of the airflow. In a manner known per se, the profile 23 comprises a lower surface 23a and an upper surface 23b, the shape of which is adapted to the desired aerodynamic properties. The air flows around the blade 1 in an axial direction DA, and the blade 1 extends in a radial direction DR.

[0020] exist Figure 1 In the example of FIG. 1 , a foil 5 is added to the CMO material 3 in the attachment area 4 located on the leading edge 13. The foil 5 can protect the CMO material 3 from impacts by objects such as hail, birds or debris. For example, the foil 5 can be made of titanium or a titanium alloy. The foil 5 can be fixed to the CMO material 3 by gluing.

[0021] Figure 2A possible example of a fabric orientation of a fiber reinforcement 10 on the attachment area is shown, which fabric orientation is adapted to the direction of mechanical stresses to which it is subjected in operation, in order to improve the attachment of the metal element 5. The adapted fabric orientation is present in the skin P of the fiber reinforcement 10, that is, in its surface area S facing the metal element 5 (here on its outer surface). The fiber reinforcement has different fabric properties (here on different weaving patterns) between the skin P and the core C. The fiber reinforcement 10 comprises: first skin threads 11p1-11p2, which are oriented in the axial direction DA and bonded to second skin threads 12p transverse to the first skin threads 11p1-11p2. In the illustrated example, the first skin threads 11p1-11p2 are woven together with the second skin threads 12p using a two-dimensional weave (for example a satin pattern). However, the invention is not limited to such an embodiment. The first skin threads 11p1 appear more on the surface S than the second threads 12p and are therefore better able to resist mechanical stresses applied mainly in the axial direction DA. The second skin wire 12p is bonded to the first skin wire 11p1-11p2 by being covered by the first portion 11p1 of the first skin wire which then appears on the surface S and by covering the second portion 11p2 of the first skin wire, which then locally appears on the surface S. For each second skin wire 12p, the number of first skin wires 11p1 in the first portion can be greater than the number of first skin wires 11p2 in the second portion. In all or part of the attachment area, the area defined by the portion of the first skin wire 11p1 on the surface S is greater than the area defined by the portion of the second skin wire 12p on the surface S. In the illustrated example, the fiber reinforcement material 10 has a three-dimensional weave at the core C, for example with an "interlocking" pattern, in which the second core wire 12c weaves multiple layers of the first core wire 11c. The weaving evolves to locally modify the fabric orientation in the skin P compared to the area Z located outside the attachment area 4. In particular, only the weaving pattern in the skin P can be adjusted on the attachment area 4 without modifying the core weaving pattern C. The adjusted fabric orientation may extend to the entire attachment area 4, or only to a small part thereof (e.g. only to a part of its height). Generally speaking, the adjusted fabric orientation, in which the first skin threads 11p1-11p2 are in the majority, may extend to an area at least equal to 10% (e.g. at least equal to 50%) of the area of ​​the attachment area 4. Generally speaking, the first skin threads 11p1-11p2, 11c may be weft threads and the second threads 12p, 12c may be warp threads, but when the opposite is considered, this does not depart from the scope of the invention.

[0022] Already Figure 1 and Figure 2 The description presented provides various details related to the construction of an example of a mixing blade 1 according to the invention. A possible manufacturing example of this blade 1 is discussed below.

[0023] First, the fiber reinforcement material 10 is produced by weaving using a method known per se and providing a majority of the first skin threads 11p1 on the surface S in the attachment region 4, such as Figure 2 As shown. The metal foil 5 is then covered with an adhesive and added to the fiber reinforcement 10 on the attachment area 4. The assembly is then placed in a mold and, for example by implementing a resin transfer molding ("RTM") technique known per se, a resin is introduced to impregnate the pores of the fiber reinforcement (). The assembly is then baked in the mold to crosslink the resin, thereby obtaining an organic matrix as well as the adhesive and forming a bond between the foil and the resin. After any finishing operations (such as machining or painting), a blade 1 ready for installation on a turbine fan disk is obtained. According to this method, the same baking step is used to crosslink the resin and the adhesive, so that the implementation is simplified compared to the case where the foil 5 is glued to a pre-prepared CMO material.

[0024] exist Figure 1 and Figure 2 In the example of a mixing blade 1 of FIG. 5 , the metal element 5 is arranged on the outer surface of the CMO material 3, in this case on its leading edge 13. However, the present invention is not limited to such Figure 3 The embodiment shown involves introducing metal elements inside the CMO material, which will be described below.

[0025] Figure 3 The blade 100 shown in the figure comprises a metal winglet 105 defining: a root portion 105a for fixing to a rotating disk; and an armature portion 105b introduced into an internal cavity of the CMO material 103, wherein the portion 105b is fixed in the attachment area 104, for example by gluing. For example, the blade 100 can be a non-flow-guiding fan blade ("open fan"). Similar to what has been described above, the fabric orientation on the surface of the CMO reinforcement material 103 is adapted to the mechanical stresses encountered in the attachment area 104. However, in the illustrated case, this orientation is more special, since the attachment area 104 has two different zones Rp and Rd, which are offset and non-overlapping in the radial direction DR and have different fabric orientations. The distal zone Rd has a higher proportion of first surface lines, which are directed here in the radial direction DR to withstand the centrifugal loads of the component. The above in combination with Figure 2The details described concerning the main characteristics of the first threads and their bonding to the second threads are appropriately applicable after taking into account the differences in thread orientation. The proximal zone Rp (i.e. the zone closer to the root 105a) is subjected to a more balanced load and can therefore adopt a lower proportion of first threads on the surface than in the distal zone Rd, in particular in this zone the ratio between the first threads and the second threads can be approximately 50 / 50. In general, the invention proposes to adapt the orientation of the skin fabric on the attachment area to the stresses in operation, and the case has been described in which at least one zone of the attachment area contains a greater proportion of first threads than the proportion of second threads. However, in the specific case of the invention, it is possible to have an attachment area that has, at least partially, a balanced distribution of first threads and second threads (approximately 50 / 50), a proportion of first threads oriented in the direction of the main mechanical stress of 50%, also regarded as a majority within the meaning of the invention.

Claims

1. A blade (1; 100) made of composite material, comprising a fiber reinforcement (10) densified by an organic matrix and provided with a metal element (5; 105) in an attachment area (4; 104), The blade is characterized in that, in at least one zone (Rd; Rp) of the attachment area, the reinforcement material comprises a surface fabric orientation (S) adapted to the direction of mechanical stress by having a first skin thread (11p1) extending in the main mechanical stress direction (DA; DR) and bonded to a second skin thread (12p) transverse to the first skin thread, the first skin thread being in the majority on the surface of the zone of the attachment area, The blades are like this: The metal element (5) is a protective foil covering the leading edge (13) of the blade, and the main mechanical stress direction corresponds to the axial direction (DA) of the blade, the axial direction corresponding to the chord length of the blade, or The blade defines an internal cavity, and the metal element (105) is a winglet inserted into the internal cavity, the winglet defines a root (105a) for fixing to a rotating disk, the main mechanical stress direction corresponds to the radial direction (DR) of the blade, and the radial direction corresponds to the axis connecting the root to the top of the blade.

2. The blade (1; 100) according to claim 1, wherein: In the region of the attachment area (4; 104), the proportion of the first skin lines (11p1) on the surface is at least equal to twice the proportion of the second skin lines (12p) on the surface.

3. The blade (1; 100) according to claim 1 or 2, wherein: The fiber reinforcement is woven in such a way that, at least in the skin (P), there is a progressive weaving between the zone of the attachment area (4; 104) and a zone (Z) of the blade located outside the attachment area.

4. The blade (1) according to claim 1, wherein: The metal element (5) is a protective foil covering the leading edge (13) of the blade, and wherein the main mechanical stress direction corresponds to the axial direction (DA) of the blade, the axial direction corresponding to the chord length of the blade, the blade being a fan blade.

5. The blade (1) according to claim 1, wherein: The metal element (5) is a protective foil covering the leading edge (13) of the blade, and wherein the main mechanical stress direction corresponds to the axial direction (DA) of the blade, the axial direction corresponding to the chord length of the blade, the blade being an outlet guide vane.

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