ASSEMBLY INTENDED FOR AN AIRCRAFT TURBOMACHINE

Abstract

The assembly (1) for an aircraft turbomachine comprises a composite part (P1) having a first opening (2), at least one metal part (P2) having a second opening (3), a clamping device (4) for the parts (P1, P2) and having a screw (5) passing through the openings (2, 3), and a reinforcing element (7) mounted in the first opening (2) and arranged between the screw (5) and the composite part (P1), the reinforcing element (7) having a tubular structure (8) having a first end (10) having a frustoconical external surface bearing against a portion of an edge (2A) of the first opening (2), this external surface (10B) being non-smooth and having a predetermined roughness or microstructure. Figure for the abbreviation: Figure 2

Description

Description Title of the invention: ASSEMBLY INTENDED FOR A TUR- AIRCRAFT BOMACHINE Technical field of the invention

[0001] — The present invention relates to an assembly for a turbomachine for aircraft comprising at least one mechanical part made of composite material and a reinforcing element of this part. The present invention also relates to a tur- aircraft engine incorporating such an assembly. Technical background

[0002] In general, fuel consumption and therefore greenhouse gas emissions The greenhouse effect of an aircraft depends on its mass. Therefore, it is common to try to make a lighter aircraft by reducing the mass of some of these elements, notably its turbomachinery.

[0003] This can be achieved by replacing certain metal parts in the acoustic panels, casings or even rectifiers ("Outlet Guide Vanes" or OGV in English), by parts made of composite material.

[0004] It is known to produce these non-metallic parts from an organic matrix (CMO) or thermoplastic or thermosetting resin by molding by resin transfer (Resin Transfer Molding or RTM), by infusion, by draping, by low and high pressure injection, by compression, or by any other shaping process.

[0005] — Although these composite material parts have as their main advantage Because they are lighter than metal parts with a similar function, they are also less mechanically resistant and less rigid.

[0006] Furthermore, the fixing of a part made of composite material with a part made of metal by a clamping device, such as a bolt or a screw-nut system, generates clamping forces on each of the parts. These clamping forces are all the more important- supports for parts used in turbomachinery where the clamping force corresponds to The weight is equivalent to several hundred to thousands of Newtons. Generally speaking, These tightening efforts generate stresses that concentrate around the orifice of passage of the clamping device and at the level of the bearing surface of the element tightening (screw, nut, washer, etc.) against the non-metallic part. The fact that these stresses are not distributed over the entire part made of composite material has for as a consequence, possible matting, cracks, or even breakage of the part.

[0007] — Furthermore, the assemblies used in turbomachinery are subjected to temp- very high temperatures which often cause a decrease in mechanical properties the parts that make them up. Furthermore, metal and composite parts react differently to high temperatures because their coefficients of thermal expansion (CTE) are different. This can lead, for the composite part, to additional stresses around the clamping device's opening, but also through its thickness, where the CTE is highest. Consequently, the clamping forces and operating temperature of the assemblies in aircraft turbomachinery lead, more or less rapidly, to damage or even breakage of the integrated composite material parts. Summary of the invention The present invention aims to overcome this drawback by locally reinforcing the part made of composite material. To this end, the invention relates to an assembly for an aircraft turbomachine, comprising: a first mechanical part made of composite material and comprising a first opening of passage, at least one second mechanical part made of metal and comprising a second passage opening, a clamping device for said mechanical parts, the clamping device comprising a screw passing through said passage holes, and a reinforcing element mounted in said first passage opening and arranged between said screw and said first mechanical part, said reinforcing element comprising a tubular structure, one end of which has a an external frustoconical surface configured to rest on a first portion of an edge of the first passage opening. According to the invention, said assembly is characterized in that said frustoconical external surface is not smooth and has a predetermined roughness or microstructure. The frustoconical outer surface of the reinforcing element bears against the edge of the composite part. The roughness or microstructure of this bearing surface is determined to enhance the adhesion or cohesion of the reinforcing element to the composite part. Advantageously, the outer surface bears against the resin of this composite material, which improves this adhesion or cohesion effect. The surface structuring is preferably not an additional layer or an added layer and is therefore preferably integrated into said reinforcing element or directly formed on this reinforcing element. This could be a simple surface roughness, such as knurling or anything else structuring. This texturing serves to increase cohesiveness at interfaces and to maintain the latter in the out-of-plane direction in the absence of the clamping device (such as a screw / nut system). If the surface texture is too pronounced, it can also have the opposite effect and degrade the interface / bond between the different elements. Therefore, the texture is predetermined to avoid this effect. Advantageously, the tubular structure includes at a second end, opposite the first end, an annular collar which is configured to bear axially on the first mechanical part, all around said first passage orifice. Thus, thanks to the invention, the reinforcing element locally strengthens the composite part. The stresses due to clamping forces during the fastening of the assembly parts are then distributed throughout the entire composite part. This improved stress distribution is achieved jointly by the frustoconical shape of one end of the reinforcing element, which increases the contact surface with the clamping device, and by the annular collar of the other end of the reinforcing element. Furthermore, the shape of the two ends allows for better retention of the reinforcing element against the composite part without the need for other means. The assembly may also exhibit one or more of the following characteristics, taken alone or in combination with each other: - the annular collar is housed, and preferably fully housed, in a bore of the first mechanical part, - the tubular structure comprises an external cylindrical surface configured to extend opposite a second portion of the edge of the first passage orifice, - said cylindrical external surface is not smooth and has a predetermined roughness or microstructure, such as, for example, knurling, -- where each external surface has knurling, - the frustoconical external surface extends over a length at least equal to the length along which the cylindrical external surface extends, - the external frustoconical surface has a cone angle between 15 degrees and 90 degrees, and preferably between 15 and 60 degrees, - the tubular structure has a radial thickness that can vary between 1 millimeter and 5 millimeters, and preferably between 1 and 2 millimeters, - the first and second ends of the tubular structure have virtually identical external diameters, - the first end of the element has a frustoconical internal surface shaped to receive a conical head of said screw, - said external surface has a roughness of between 0.3 and 0.5 millimeters, particularly for a temperature between -40°C and 150°C; in the present application, roughness represents the distance between the lowest bottoms of the hollows on the surface and the highest peaks of the bumps on this surface, and can therefore be considered equivalent to the amplitude of the relief of this surface; a roughness of between 0.03 mm and 0.5 mm can ensure that the reinforcing element remains at ambient temperature even in the absence of the clamping device. -- the conical head of said screw extends over a length at least equal to half the length of the frustoconical internal surface of said reinforcing element, -- the reinforcing element is made of a metallic material such as stainless steel or INCONEL®, or any other material with or without surface protection (painting, anodizing, galvanizing, chrome plating, etc.) to avoid or limit galvanic couples with said composite material, and -- the reinforcing element can be overmolded or inserted against the first mechanical part. The invention also relates to a turbomachine comprising at least one assembly according to one of the preceding characteristics. Brief description of the figures Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for which reference should be made to the accompanying drawings in which: [Fig.1] The [Fig.1] is a schematic view of an assembly for an aircraft turbomachine; [Fig.2] Fig.2 is a cross-sectional and perspective view of an embodiment of an assembly according to the invention; [Fig.3] Fig.3 represents a double axial section of a reinforcing element of an assembly having an angle of approximately 45 degrees according to the invention; [Fig.4] Fig.4 represents a double axial section of a reinforcing element of an assembly having an angle of approximately 60 degrees according to the invention; [Fig.5] Fig.5 represents a double axial section of a reinforcing element of an assembly having an angle of approximately 30 degrees according to the invention; [Fig.6] Fig.6 illustrates a double axial section of an assembly according to a particular embodiment. Detailed description of the invention The mass of the turbomachinery of an aircraft, whether it be a civil or military transport aircraft or a helicopter, can be reduced by replacing certain parts. taliques present in certain assemblies (casings, acoustic panels, rectifiers, etc.) by parts made of composite material, for example with an organic matrix (hereinafter "CMO part"). Figures 1 and 3 represent such an assembly 1 which comprises at least two mechanical parts P1 and P2. The first mechanical part P1 is made of CMO type composite material (hereinafter "part P1"). It extends in a plane T1 and has a first through-hole 2 with an edge 2A. The assembly | also includes at least one second mechanical part P2 made of metallic material (hereinafter "part P2"). This metal part P2 extends in another plane parallel to plane T1 and also includes a second through-hole 3. The CMO part P1 and the metal part P2 are arranged against each other such that the through-holes 2 and 3 are opposite each other. Although not shown, the assembly | may further include other mechanical parts arranged against the metal part P2. As shown in particular in Figures 1 and 2, assembly 1 also includes a clamping device 4 that secures parts P1 and P2 together against each other. In a preferred embodiment, the clamping device 4 is of the bolt type and may include at least one screw 5 and one nut 6. The screw 5 is arranged along a longitudinal axis XX and passes through the two through holes 2 and 3. In the following description, a coordinate system associated with the clamping device 4 is used. This coordinate system is defined in terms of the longitudinal axis XX along which the screw 5 of the clamping device 4 is arranged and the plane T1 which is perpendicular to the longitudinal axis XX and which includes a radial direction R. The adjectives "upper" and "lower" are defined, respectively, in the direction of the screw 5 along the longitudinal axis XX (represented in particular by an arrow F) and in the direction opposite to the direction represented by the arrow F. As for the radial direction R, it is defined radially in a cross-section to the longitudinal axis XX, from the center representing the position of the longitudinal axis XX in the plane T1. The adjectives "internal" and "external" are defined with respect to the radial direction R, respectively, towards the longitudinal axis XX and away from the longitudinal axis XX. The screw 5 of the clamping device 4 comprises a head 5A arranged at an upper end on the side of the CMO part P1 and a lower threaded portion. The nut 6 is fixed to the threaded portion of the screw 5 on the side of the metal part P2. In a particular embodiment, the clamping device 4 may include one or more washers (not shown), arranged between the head SA of the screw 5 and the CMO part P1, or between the nut 6 and the metal part P2. Alternatively, a washer may also be arranged between the CMO part P1 and the metal part P2. Assembly 1 according to the invention can be used in aircraft turbomachinery. The clamping device 4 must therefore allow for the fastening and retention of parts P1 and P2 together at high temperatures. The coupling forces between parts P1 and P2 can be very significant, even though part P1, made of CMO, has reduced mechanical properties due to temperature effects. Thus, in a preferred embodiment, the assembly 1 includes a reinforcing element 7, as shown in [Fig. 2]. The reinforcing element 7 is mounted in the through-hole 2, against the edge 2A. The reinforcing element 7 is further positioned between the screw 5 and the CMO part P1. The presence of the reinforcing element 7 locally strengthens the CMO part P1 to limit the concentration of mechanical stresses at the edge 2A of the through-hole 2 when parts P1 and P2 are fastened together. In a preferred embodiment, the reinforcing element 7 is made of a metallic material. This metallic material may be stainless steel, INCONEL®, or another material. The advantage of this type of material is that it limits or even eliminates galvanic torque effects that can occur between the reinforcing element 7 and the mechanical parts P2, which may be reinforced with carbon fibers. As shown in particular in Figures 2 to 5, the reinforcing element 7 comprises a tubular structure 8 arranged along the longitudinal axis XX. In a preferred embodiment, this tubular structure 8 has a thickness ranging from 1 mm to 5 mm. This thickness is, for example, 2 mm. The tubular structure 8 consists of a cylindrical hollow body 9 through which the screw 5 passes, a first upper end 10, and a second lower end 11. The cylindrical body 9 of the tubular structure 8 is arranged between the upper end 10 and the lower end 11. The upper end 10 has an external surface 10B which is frustoconical in shape. This frustoconical external surface 10B is shaped to bear against a first portion 2Aa of the edge ZA. The external surface 10B forms a truncated cone which is defined by a length L1 and, in its widest part radially, by an external diameter.In the following description, length is defined as the distance over which an element extends along the longitudinal axis XX. In a preferred embodiment, the angle al of the truncated cone formed by the external surface 10B can vary between 15 degrees and 90 degrees. Preferably, the cone angle al varies between 15 degrees and 60 degrees, as shown in Figures 3, 4 and 5. The thickness of the tubular structure 8 depends in particular on this angle. Furthermore, the truncated conical shape of the external surface 10B increases the bearing surface of the reinforcing element 7 against the CMO part P1. This increased bearing surface allows for a better distribution of the stresses due to clamping forces on The part Pl is positioned at the edge 2A of the through-hole 2. Thus, the larger the bearing surface 10B, the lower the stresses in the composite part. For example, increasing the bearing surface by 25% on the screw head reduces the stress within the material by a factor of approximately 4. This reduces the risk of compression and / or deformation of part PI. Furthermore, by decreasing the angle al of the cone formed by the external surface 10B, the mechanical stress resulting from the clamping forces on the CMO part P1 is reduced. Indeed, for a reinforcement element of a given height or axial dimension, reducing the angle al minimizes stresses; therefore, the smaller the angle, the less stress the composite part experiences. As shown in Figures 3 to 5, the body 9 of the tubular structure 8 also has a cylindrical external surface 9B that extends longitudinally opposite a second portion 2Ab of the edge 2A of the passage orifice 2. This second portion 2Ab, to which the external surface 9B of the body 9 is conformed, has a cylindrical shape. The cylindrical external surface 9B extends over a length L2 along the longitudinal axis XX. The length L2 depends on the value of the angle al and can also depend on the thickness of the CMO part P1. In a preferred embodiment, the length L2 of the cylindrical external surface 9B can be substantially equal to the length L1 of the frustoconical external surface 10B, as shown in [Fig. 3]. Alternatively, the length L1 is greater than the length L2, as shown in Figures 3 and 5. Increasing the length L1 relative to the length L2 reduces the stresses experienced by the CMO part P1. In a preferred embodiment, the external cylindrical surfaces 9B and frustoconical surfaces 10B are not smooth and have a predetermined roughness or microstructure. These surfaces therefore have a predefined surface structure. This microstructure is, for example, knurling. This optimizes the adhesion of the reinforcing element 7 to the CMO part P1. In a variant, only the external frustoconical surface 1OB has such a microstructure. Furthermore, as shown in Figures 2 to 5, the tubular structure 8 may optionally include, at its lower end 11, an annular collar 12 extending in the radial direction R. In the drawings, dashed lines delimit the contour of the lower end of the reinforcing element in the case where the latter does not include a collar 12. Preferably, the values ​​of the external diameters of the upper end 10 and of the collar 12 of the lower end 11 are substantially identical. The value of the diameter depends on the value of the angle al. For example, when the angle al is close to 30 degrees, the value of the diameter of the lower end 11 is minimal; the value of the diameter of the lower end 11 is maximum when the angle al is equal to 90 degrees. In a preferred embodiment, the annular collar 12 bears axially against a third portion 2Ac of the edge 2A of the through-hole 2. This third portion 2Ac forms a bore 13 made in a lower part of the CMO component P1. The annular collar 12 is thus housed, preferably entirely housed, in the bore 13. The presence of the annular collar 12 at the lower end 11 allows the reinforcing element 7 to increase the local reinforcement of part P1. The stresses related to the coupling forces are distributed not only in the plane T1 but also along the longitudinal axis XX, thanks to the presence of the collar 12. The specific shapes of the ends 10 and 11 of the reinforcing element 7 thus lead to a reduction in the risk of deformation or even cracking of part P1, including at the high operating temperatures of an aircraft turbomachine. Furthermore, clamping or encompassing the through-hole 2 results in greater stability and less play between part P1 and the reinforcing element 7 during the clamping of parts P1 and P2 together. In addition, the presence of the annular collar 12 allows for a reduction in the thickness of the tubular structure 8. The radial thickness of the reinforcing element can vary. When this thickness is relatively large, a flange is not necessary, which is advantageous. Because of the absence of a flange, the reinforcing element is easier to manufacture (requiring less machining, for example). The increased thickness also compensates for the increased stresses due to the absence of a flange. Furthermore, the upper end 10 of the reinforcing element 7 has an internal surface 10A which is shaped to the head SA of the screw 5. In a particular embodiment, the internal surface 10A is frustoconical in shape so that a conical head SA of the screw 5 bears against it, as shown in figures 3, 4 and 5. The internal surface 10A extends over a length similar to the length LI of the external surface 1OB. In a preferred embodiment, the bearing length L3 of the conical head 5A of the screw 5 on the internal surface 10A is at least equal to half the length LI, as shown in [Fig. 6]. Thus, increasing the length and therefore the bearing surface of the conical head SA against the internal surface 10A of the reinforcing element 7 reduces the stress within the CMO part P1. In a variant, the internal surface 10A is cylindrical or rectangular, as shown in [Fig. 2]. The head SA of the screw bears against the internal surface 10A, which is arranged in a plane. Alternatively, the screw head could be milled and frustoconical in shape so as to bear at least partially against an internal surface 10A of complementary shape. commentary on the reinforcement element, as illustrated in [Fig.3]. Furthermore, in a preferred embodiment, the reinforcing element 7 is overmolded onto the mechanical part made of CMO composite material. In another embodiment, the reinforcing element is inserted into the CMO mechanical part. This insertion can be performed cold or hot under pressure. The insertion can also be performed by pressure and ultrasound. The assembly according to the invention therefore offers the advantages of allowing local reinforcement, directly on the friction zones, of the composite part P1 and improving the transmission and distribution of clamping forces on this composite part P1. In doing so, very high clamping forces can be applied to the parts in order to optimize the stability of the assembly. The external surface 10B preferably has a roughness between 0.3 and 0.5 mm, particularly for temperatures between -40°C and 150°C. The structure of the reinforcing element 7 also depends on its insertion against the composite material part. For example, in the case of purely mechanical insertion, the structure can be more pronounced, with a maximum value of 0.5 mm and a minimum value greater than 0.3 mm. In the case of co-molding, the roughness could be lower, and the maximum value could be less than 0.5 mm.

Claims

Demands

1. Assembly intended for a turbomachine for aircraft, comprising: a first mechanical part (P!) made of material composite and comprising a first passage opening (2), at least one second mechanical part (P2) made of metal and comprising a second passage opening (3), a clamping device (4) for said mechanical parts (P1, P2), the clamping device (4) comprising a screw (5) passing through said passageways (2, 3), and a reinforcing element (7) mounted in said first orifice of passage (2) and arranged between said screw (5) and said first mechanical part (P1), said reinforcing element (7) comprising a tubular structure (8) having a first end (10) presents an external surface (10B) with a truncated cone configuration to take support from a first portion (2Aa) of an edge @A) of the first passage opening (2), said assembly (1) being characterized in that said external surface (10B) frustoconical is not smooth and has a roughness or micro- predetermined structure.

2. Assembly (1) according to claim 1, characterized in that the tubular structure (8) includes at a second end (11), opposite at the first end (10), an annular collar (12) which is configured to bear axially on the first piece (P1) mechanical, all around said first passage orifice (2).

3. Assembly (1) according to claim 2, characterized in that the The annular collar (12) is housed, and preferably fully housed, in a bore (13) of the first mechanical part (P1).

4. Assembly (1) according to any one of the preceding claims, characterized in that the tubular structure (8) comprises an external surface (9B) cylindrical shape configured to extend in relation to a second portion (2Ab) of the edge (2A) of the first passage orifice (2).

5. Assembly (1) according to claim 3, characterized in that said external surface (9B) cylindrical is not smooth and has a roughness or a predetermined microstructure.

6. Assembly (1) according to claim 4 or 5, characterized in that the The frustoconical external surface (10B) extends over a length (L1) at less than or equal to the length (L2) along which the surface extends external (9B) cylindrical.

7. Assembly (1) according to any one of the preceding claims, characterized in that the frustoconical external surface (10B) has an angle (al) of a cone between 15 degrees and 90 degrees.

8. Assembly (1) according to any one of the preceding claims, characterized in that the tubular structure (8) has a thickness radial which can vary between 1 millimeter and 5 millimeters.

9. Assembly (1) according to claim 2, characterized in that the first and second ends (10, 11) of the tubular structure (8) have their external diameters are virtually identical.

10. | Assembly (1) according to any one of the preceding claims, characterized in that the first end (10) of the reinforcing element (7) has a frustoconical internal surface (10A) shaped for receive a conical head (5A) of said screw (5).

11. | Assembly (1) according to any one of the preceding claims, characterized in that said external surface (10B) has a roughness between 3 hundredths and 5 tenths of a millimeter.

12. Aircraft turbomachine comprising at least one assembly (1) according to any one of the preceding claims.