Repairing of parts made of composite material covered with an Anti-erosion film

Abstract

The invention relates to a method for repairing a part (100) made of an organic-matrix composite material at least partially covered with an anti-erosion film (30), the method comprising the following steps: - removing the anti-erosion film from a damaged area (50) of the part; - removing an initial adhesive (32), initially attaching the film to the damaged area, so as to form a recessed portion (55); - depositing a repair adhesive (38) in the recessed portion (55) or on one face of a patch of a replacement anti-erosion film (30') shaped to replace the film of the damaged area; - placing the patch of the replacement film (30') on the damaged area; - and polymerising the repair adhesive (38) at a polymerisation temperature of less than 100°C forming a repaired area (60) to replace the damaged area (50).

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: REPAIR OF PARTS MADE OF COMPOSITE MATERIAL COATED WITH AN ANTI-EROSION FILM

[0003] TECHNICAL FIELD

[0004] The present invention relates to the repair of parts made of organic matrix composite (OMC), i.e. comprising a fibrous reinforcement densified by a matrix of organic nature, and in particular the repair of an anti-erosion film covering the surface of a part made of composite material.

[0005] The invention relates more particularly to the field of gas turbines, and especially to turboshaft engines for aircraft. In particular, the invention applies to a fan blade of a turboshaft engine for aircraft.

[0006] PREVIOUS TECHNIQUE

[0007] A common method for producing composite parts is the liquid process. This process involves creating a fibrous preform, roughly in the shape of the part to be manufactured, which will serve as reinforcement for the composite material. This preform is then impregnated with a liquid composition containing a precursor of the matrix material. The precursor is usually a polymer, such as a thermoplastic or thermosetting resin, possibly diluted in a solvent. The transformation of the precursor into the matrix is ​​achieved through heat treatment, after the removal of any solvent and the crosslinking of the polymer. The fabrication of an organic matrix composite blade for a gas turbine aircraft engine is described in US patent 2016 / 243777.

[0008] CMO parts can be damaged as a result of shock or impact. This is the case, for example, with the blades or fan housings of aircraft engines, which are subjected during operation to impacts with foreign objects such as birds or other debris.

[0009] Furthermore, the surface of the composite fan blades must also be protected against erosion. Currently, the underside of the composite fan blade body is covered with an anti-erosion film bonded with adhesive. However, this anti-erosion film can suffer erosion and / or localized damage, such as tearing, during operation due to impacts from foreign objects like gravel. Wear of the anti-erosion film can cause problems during engine operation. Thus, wear of the anti-erosion film will no longer protect the part and could potentially lead to the loss of some pieces of the film, or even the entire film covering the blade surface.

[0010] Failure to repair will result in the part being discarded, which is unacceptable both economically and environmentally.

[0011] Similarly, the visual appearance of the part will be degraded and could generate customer reluctance. Indeed, fan blades are the first parts seen by passengers boarding the aircraft.

[0012] Therefore, the damaged area must be repaired in order to restore the integrity of the structural resistance and prevent any propagation of defects from the damaged area before the part can be put back into service.

[0013] Currently, repairing or replacing the erosion control film using the original adhesive requires temperatures above 120°C. However, such temperatures accelerate the aging of the CMO composite material. Therefore, repairing the erosion control film can impact the part's lifespan.

[0014] The objective of the present invention is therefore to overcome these drawbacks by proposing another method for repairing the anti-erosion film of a part made of composite material.

[0015] SUMMARY OF THE INVENTION

[0016] To this end, the invention relates to a method for repairing a part made of organic matrix composite material covered at least partially with an anti-erosion film, the anti-erosion film being fixed to the part by a layer of an initial adhesive, the method comprising the following steps:

[0017] - the removal of the anti-erosion film from a damaged area of ​​the part,

[0018] - the removal of the initial layer of glue from the damaged area to create a hollowed-out section,

[0019] - the supply of a replacement anti-erosion film patch, the patch being shaped to replace the anti-erosion film in the damaged area,

[0020] - the application of a layer of repair adhesive in the hollowed-out portion or on one face of the replacement anti-erosion film patch,

[0021] - the placement of the replacement anti-erosion film patch at the damaged area so that the repair adhesive layer is arranged between the part and the replacement anti-erosion film patch, - the polymerization of the repair adhesive at a polymerization temperature below 100°C forming a repaired area in place of the damaged area.

[0022] The invention thus proposes a repair method capable of overcoming the aforementioned drawbacks.

[0023] Indeed, the invention proposes a method for repairing a part made of composite material covered with an anti-erosion film, particularly when the latter has been damaged, making it possible to avoid discarding parts before the end of their potential, while reducing economic and environmental impacts.

[0024] The repair process according to the invention makes it possible to reliably repair, without damaging the composite of the part, any CMO structure covered with an anti-erosion film damaged due to contact wear or following superficial damage outside the contact areas, for example an impact related to a release of debris in the turbine.

[0025] Advantageously, the process allows the part to be repaired using a low-temperature paste repair adhesive, avoiding any overheating of the part as a whole or locally.

[0026] The repair process according to the invention thus allows the replacement of the damaged anti-erosion film in its entirety or in the form of patches, hot or cold, by selection of a low temperature paste adhesive, adapted to the constraints of the part, in particular a blower blade made of CMO material.

[0027] The method according to the invention may comprise one or more of the following features, taken individually or in combination with each other in all technically possible combinations:

[0028] - the repair adhesive is a two-component epoxy paste that polymerizes at a temperature between 20°C and 70°C;

[0029] - the process includes, after the polymerization step, a finishing step at least in the repaired area, preferably by sanding;

[0030] - the process includes, after the polymerization step, a step of applying at least one layer of paint to the repaired area;

[0031] - the anti-erosion film and / or the replacement anti-erosion film is a polyurethane film;

[0032] - the process includes, before the step of removing the anti-erosion film from the damaged area, a masking step using a first adhesive, preferably Teflon®, so as to delimit an area of ​​anti-erosion film to be removed in the damaged area; - the process includes, after the removal of the initial adhesive layer, a cleaning step of the hollowed-out portion;

[0033] - the process includes, before the polymerization step, a step of applying a second adhesive to hold the replacement anti-erosion film patch against the part during the polymerization step, and after the polymerization step, a step of removing the second adhesive;

[0034] - the process includes a step of applying a layer of a patch-retaining material for the replacement anti-erosion film against the part;

[0035] - the material layer is a layer of flexible material, for example silicone, or a metal part;

[0036] - the part is a blade, specifically a fan blade for an aircraft turbomachine.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be better understood and other details, features and advantages of the present invention will become more apparent upon reading the description of a non-limiting example that follows, with reference to the accompanying drawings in which:

[0039] - Figure 1 is a schematic axial cross-sectional view of a turbofan engine to which the invention applies;

[0040] - Figure 2 is a perspective and cutaway view of an aeronautical engine comprising a fan to which the invention applies;

[0041] - Figure 3 is a schematic perspective view of a part made of composite material such as a blower blade to which the invention applies;

[0042] - Figure 4 is a schematic perspective view of the turbine blade of Figure 3 covered with an anti-erosion protection;

[0043] - Figure 5 shows a cross-sectional view of the blade in Figure 4, showing an example of the multi-layered structure of the different elements of the part to be repaired, particularly the blade on the intrados side;

[0044] - Figure 6 is a flowchart of a repair process according to the invention of a part made of organic matrix composite (OMC);

[0045] - Figure 7 is a schematic view similar to Figure 5 after a step of removing a damaged part of the part being repaired; and - Figure 8 is a schematic cross-sectional view of the part in Figure 5 after repair of the damaged part.

[0046] Elements having the same functions in different implementations have the same references in the figures.

[0047] In the figures, the scales and proportions are not strictly respected for the purposes of illustration and clarity.

[0048] Furthermore, in the description and claims, the terminology axial, radial and transverse will be adopted without limitation, the axial axis being parallel to the longitudinal axis of the turbomachine according to the invention.

[0049] Thus, the terms "axial" and "axially" are defined with respect to the axial axis, which is parallel to the longitudinal axis of the turbomachine. The terms "radial" and "radially" are defined with respect to the radial axis, which is perpendicular to the longitudinal axis of the turbomachine.

[0050] In the description, and unless otherwise stated, the terms "internal" and "external" are used as non-limiting references to the radial distance from the longitudinal axis around which the lubrication chamber extends, the term "internal" defining an area radially closer to the longitudinal axis of the reducer, as opposed to the term "external".

[0051] DESCRIPTION OF IMPLEMENTATION METHODS

[0052] The invention applies generally to any part made of organic matrix composite material, that is to say comprising a fibrous reinforcement densified by a matrix, the part being further covered at least partially with an anti-erosion film.

[0053] An erosion protection film or anti-erosion film is a coating that resists erosion and, by covering an area of ​​the body of the part, protects it against erosion by improving the resistance of that area to the erosion phenomenon.

[0054] The invention will be described below in the context of its application to the repair of a fan blade for an aircraft gas turbine or turbomachine engine, particularly one used in aircraft. In particular, the invention applies to fan blades for LEAP engines (Leading Edge Aviation Propulsion), which are generally formed from a three-dimensional woven preform of carbon fibers impregnated with an epoxy resin.

[0055] Such an engine is shown in longitudinal section in Figure 1 and in perspective and cutaway view in Figure 2. With reference to Figures 1 and 2, a turbomachine 1 is shown, which has a central longitudinal axis 2 around which its various components extend. It comprises, from upstream to downstream along a principal direction 5 of gas flow through this turbomachine, a fan 3, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 11, a high-pressure turbine 7, and a low-pressure turbine 8.

[0056] Conventionally, after passing through the blower 3, the air splits into a central primary flow 12a and a secondary flow 12b which surrounds the primary flow. The primary flow 12a flows into a main gas circulation channel 14a, passing through the compressors 4, 6, the combustion chamber 11, and the turbines 7, 8. The secondary flow 12b flows into a secondary channel 14b, radially delimited outwards by an engine casing, surrounded by a nacelle 9.

[0057] The blower 3 includes a movable wheel 16 composed of a plurality of blades 20 each mounted on a turbine rotor 17 and surrounded by a blower housing 18 having a shape of revolution.

[0058] Figure 3 shows an example of a composite material blade 20 for a turbomachine fan. The blade 20 comprises a blade 22, with an aerodynamic profile, elongated in a longitudinal direction, and a foot 24 formed by a thicker section, for example with a bulbous cross-section, connected by a strut 25 to the blade 22. The blade 20 is mounted on the turbine rotor 17 by engaging the foot 24 in a correspondingly shaped housing provided at the periphery of the rotor.

[0059] The blade 22 has an intrados face 26 and an extrados face (not visible in the figure) extending between a leading edge 27 and a trailing edge 28 opposite the leading edge. In other words, the blade 22 is laterally bounded by the intrados face 26 and the extrados face connecting the leading edge 27 and the trailing edge 28. The leading edge 27 is positioned upstream, following the direction of gas flow in the turbomachine. The intrados 26 and extrados faces are curved, and are respectively concave and convex.

[0060] The 20 awl is made of organic matrix composite material. In other words, it consists of fibers or filaments bonded together by a matrix, that is to say, it includes a fibrous reinforcement densified by a matrix typically corresponding to a polymer resin, such as a thermoplastic or thermosetting resin, possibly diluted in a solvent.

[0061] The filaments or fibers can be made of carbon, glass, ceramic (for example silicon carbide), aramid, silica, alumina, etc.

[0062] The polymer resin is, for example, an epoxy, bismaleimide, or polyimide resin. The fibrous reinforcement is made from a fibrous texture obtained, for example, by three-dimensional weaving in a single piece, the texture being shaped in a tool. The resulting fibrous reinforcement is then densified by the matrix, for example, using the well-known RTM injection molding process (Resin Transfer Molding). The manufacture of such a blade is described in particular in US document 2016 / 243777.

[0063] Areas susceptible to erosion and / or impact from this blade must be protected, particularly the leading edge 27, which is protected in a known manner using a metal shield 29, and the lower surface 26, using an erosion control film 30, as shown in Figure 4. Generally, the erosion control film 30 is a polyurethane film, a material belonging to the diverse family of polymers and plastics, which is bonded to the lower surface for reinforcement. Using a thermoplastic film allows it to be sufficiently malleable to conform to the three-dimensional shape of the blade, and especially its blade itself.

[0064] As is known, the erosion control film 30 (generally a polyurethane film) is bonded to the blade 20, specifically the blade blade, by gluing. This is done, for example, by applying a layer of adhesive 32, referred to as the "initial adhesive" or original adhesive, made of a thermosetting polymer chosen from epoxy, polyester, or other types of adhesives, in film or paste form, with or without a backing, to the blade blade before applying the metal shield and the erosion control film. Preferably, the initial adhesive is 3M® AF191 M. The assembly is then cured, for example, in an autoclave, for 3 hours at 150°C.

[0065] In addition, generally, blade protection advantageously includes the application of an anti-erosion paint 34 over the entire blade body, with the exception of the leading edge shield 29 27.

[0066] Figure 5 shows a cross-sectional view of a part 100, and in particular of a blade showing a multi-layered structure, i.e., a superposition of the different elements of the blade on the lower surface. Thus, a blade 20 is obtained having an anti-erosion polyurethane film 30 bonded to the lower surface 26 of the blade body using an initial layer of adhesive 32, covered with a layer of a bonding material or primer 34 and an anti-erosion paint layer 36 applied to the entire blade, including the lower and upper surfaces.

[0067] For example, the assembly formed by the erosion control film 30 and its adhesive 32 has a thickness of 0.4 mm, and the paint layer 36 has a thickness of approximately 0.1 mm. The primer 34 is, for example, a silane / ethanol type adhesion primer. It promotes the adhesion of the paint layer 36. However, when the composite material of the part 100 and / or that of the erosion control film 30 has a surface finish compatible with paint adhesion, the prior application of a primer 34 is not necessary, and the paint 36 can be applied directly to the exposed surface of the composite material of the part 100 and the erosion control film 30.

[0068] A method for repairing part 100 (in this application case, a blade 20), and in particular the anti-erosion film 30, will now be detailed with reference to Figure 6, which shows a flowchart of this method. The dotted steps are optional, representing variants of the repair method according to the invention.

[0069] In figures 4 and 5, part 100 (in this application example a blade 20) and in particular the anti-erosion film 30, also shows a damaged area 50 resulting for example from an impact with an object ingested by the blower of the motor, for example a bird, debris, ice, etc.

[0070] This damaged area 50 has a damaged anti-erosion film 26. In addition, and as shown in the example in Figure 5, this damaged area 50 may show wear of the protective paint layer 36 and its possible associated primer layer 34.

[0071] The process includes a step S10 of removing the anti-erosion film at the damaged area 50 of the part 100. During this step S10, partial or total removal of the damaged anti-erosion film 30 is carried out, so as to remove the damaged part 50 of this damaged anti-erosion film.

[0072] In the case of partial removal of the damaged erosion control film 30, this step is preferably preceded by a preliminary masking step S5 using a first adhesive to delimit an area of ​​erosion control film to be removed within the damaged area 50. The first adhesive used in this step is, for example, Teflon®. In S10, the damaged erosion control film 30 is removed with a blade-type tool, such as a scalpel, protruding tool, chisel, or other similar tool, without damaging the organic matrix composite material of the part 100. The process then continues with a step S20 of removing the initial adhesive layer 32 from the damaged area 50 to create a hollowed-out portion 55 and expose the external surface of the part 100.

[0073] The removal of the initial adhesive, preferably an AF191 M adhesive from 3M®, is carried out by scraping and / or sanding.

[0074] This gives us, as illustrated in figure 7, a hollowed portion 55 which opens onto the external surface of the part 100 and in particular onto the intrados 26 of the blade 20.

[0075] Preferably, after the removal S20 of the initial glue layer 32, the hollowed portion 55 can be cleaned in S25. During this step S25, the external surface of the part 100, and in particular the intrados 26 of the blade 20, is advantageously cleaned and degreased with, for example, isopropyl alcohol.

[0076] The process then includes a step S30 of supplying a 30' replacement anti-erosion film patch or a complete replacement anti-erosion film if it is necessary to replace all of the original anti-erosion film. The 30' patch is shaped to replace the 30' anti-erosion film in the damaged area 50. In other words, the 30' patch has been pre-cut to the dimensions of the damaged area 50 that has been removed.

[0077] The replacement 30' anti-erosion film is a polyurethane film, preferably from the company 3M®.

[0078] Preferably, the replacement 30' anti-erosion film is a polyurethane film of the same material and thus having the same properties as the original 30' anti-erosion film.

[0079] To fix the new replacement anti-erosion film or film patch 30', the process includes depositing S40 a layer of repair adhesive 38 in the hollowed portion 55 and / or on one face of the replacement anti-erosion film patch 30' which must be fixed to the external surface of the part 100 and in particular on the intrados 26 of the blade 20. Advantageously, the repair adhesive 38 is a two-component epoxy paste that polymerizes at a temperature between 20°C and 70°C.

[0080] Repair adhesive 38 is not harmful to the resin of the CMO of part 100.

[0081] For example and preferably, repair glue 28 is the glue referenced EA9396 from the company LOCTITE / HENKEL®.

[0082] Then, during a step S50, the replacement anti-erosion film patch 30' is placed at the damaged area 50, and more specifically in the hollowed area 55, so that the repair adhesive layer 38 is arranged between the part 100 and the replacement anti-erosion film patch 30'.

[0083] The 30' replacement anti-erosion film patch is positioned precisely so that the edges of the junctions between the 30' replacement anti-erosion film patch and the rest of the original 30' anti-erosion film of the part are perfectly joined, i.e. edge to edge.

[0084] The process continues with a step S60 of polymerization of the repair adhesive 38 at a polymerization temperature below 100°C forming a repaired area 60 in place of the damaged area 50, as illustrated in Figure 8.

[0085] During this step, once deposited in the recess 55 and covered with the replacement anti-erosion film patch 30', the repair adhesive 38 undergoes a polymerization treatment to harden it, for example, a heat treatment, resulting in a repair area 60 (Figure 8). The assembly formed by the repair adhesive layer 38 and the replacement anti-erosion film patch 30' positioned on the part 100 can be heated using a conventional heating method such as an oven, autoclave, heat gun, etc., or left to air dry.

[0086] Regardless of the heating method (autoclave, press-clave, etc.), the fabrics used for the curing cycle under a tarpaulin (draining fabrics, demolding fabrics, etc.) cover part 100 to create a vacuum under the tarpaulin, i.e., to draw out the air and press the assembly against part 100. Part 100, placed under the tarpaulin and under vacuum, will be heated with a permanent vacuum during the curing cycle in order to limit and eliminate porosity in the glue, which is detrimental to the mechanical properties of the bond.

[0087] In the case of a local heating method such as a heating mat, the whole can be confined to the area grouping all the 30' repair patches.

[0088] Before the S60 polymerization step of the repair adhesive 38, the process may advantageously include a step S65 for applying a second adhesive to hold the replacement anti-erosion film patch 30' against the part 100 during the S60 polymerization step. After the S60 polymerization step, the second adhesive is removed in S65. This alternative is shown schematically by the arrows F50 in Figure 6.

[0089] Advantageously, the process includes, after the polymerization step S60, a finishing step S70 at least at the level of the repaired area 60, preferably by sanding, in order to remove any excess repair glue 38 which may flow and / or regain the aerodynamic profile of the blade.

[0090] In the case where, in the damaged area 50, the erosion control film 30 is initially coated with a layer of paint 36 as illustrated in Figures 5, 7, and 8, the process includes a preliminary step of partially or completely removing the erosion control paint 27, for example by a stripping process, such as manual sanding, so as to at least remove the erosion control paint in the damaged area of ​​the damaged erosion control film 26 (mainly located near the tip of the blade). More specifically, the paint 102 and the primer 101 are first removed, for example by sanding, from the damaged area 20 in order to expose the organic matrix composite material 100 in this area.

[0091] Similarly, the process may include after the polymerization step S60 and, where appropriate, after the finishing step S70, a step S80 of applying at least one layer of protective paint 36 to the repaired area 60 or to the entire surface of the part 100.

[0092] If necessary, a primer layer 34 and a protective paint layer 36 are applied to the repaired area in order to reconstitute, if necessary, the initial primer layer 34 and the initial paint layer 102 present on the composite coating of the part 100.

[0093] The protective paint layer 36, and if necessary a primer layer 34, can be applied to the part even if initially the part to be repaired was not coated with it.

[0094] Furthermore, the process may advantageously include an application step S90 of a layer of material to hold the replacement anti-erosion film patch 30' against the part 100 during the polymerization cycle of the repair adhesive 38. The material is preferably a flexible material such as silicone, metallic foil, or a metallic or plastic part. This material layer is shaped to hold the replacement anti-erosion film patch 30' against the part 100, restore the aerodynamic profile of the part 100, and allow for localized application of pressure to the repair adhesive 38.

[0095] Steps S70 for finishing, S80 for applying at least one layer of protective paint 36 and S90 for applying a layer of patch-retaining material for the replacement anti-erosion film 30' are optional and can be cumulative in different execution orders.

[0096] The invention, as described, thus proposes a method for repairing a part made of organic matrix composite material covered with an anti-erosion film, in particular a fan blade for an aircraft turbomachine, in order not to discard the parts before their end of potential, while reducing economic and environmental impacts.

[0097] Note that the examples illustrated in the figures are in no way limiting; the repair process according to the invention applies to any CMO structure covered with a damaged anti-erosion film that needs to be repaired due to contact wear or following superficial damage outside the contact areas, for example, an impact related to the release of debris in the turbine.

Claims

DEMANDS 1. A method for repairing a part (100) made of organic matrix composite material covered at least partially with an anti-erosion film (30), the anti-erosion film being fixed to the part by a layer of an initial adhesive (32), the method comprising the following steps: - the removal (S10) of the anti-erosion film (30) at the level of a damaged area (50) of the part (100), - the removal (S20) of the initial adhesive layer (32) at the level of the damaged area (50) so as to form a hollowed-out portion (55), - the supply (S30) of a replacement anti-erosion film patch (30'), the patch being shaped to replace the anti-erosion film (30) of the damaged area (50), - the application (S40) of a layer of repair adhesive (38) in the hollowed portion (55) or on one face of the patch of the replacement anti-erosion film (30'), - the placement (S50) of the replacement anti-erosion film patch (30') at the damaged area so that the repair adhesive layer (38) is arranged between the part (100) and the replacement anti-erosion film patch (30'), - the polymerization (S60) of the repair adhesive (38) at a polymerization temperature below 100°C forming a repaired area (60) in place of the damaged area (50).

2. Method according to claim 1, wherein the repair adhesive (38) is a two-component epoxy paste that polymerizes at a temperature between 20°C and 70°C.

3. A method according to claim 1 or 2, comprising after the polymerization step (S60), a finishing step (S70) at least at the level of the repaired area (60), preferably by sanding.

4. A method according to any one of the preceding claims, comprising after the polymerization step (S60), an application step (S80) of at least one coat of paint (36) on the repaired area (60).

5. A method according to any one of the preceding claims, wherein the anti-erosion film (30) and / or the replacement anti-erosion film (30') is a polyurethane film.

6. A method according to any one of the preceding claims, comprising before the step (S10) of removing the anti-erosion film (30) at the level of the damaged area (20), a masking step (S5) using a first adhesive, preferably made of Teflon®, so as to delimit an area of ​​anti-erosion film to be removed in the damaged area (50).

7. A method according to any one of the preceding claims, comprising after the removal (S20) of the initial glue layer, a cleaning step (S25) of the hollowed portion (55).

8. A method according to any one of the preceding claims, comprising prior to the polymerization step (S60), an application step (S55) of a second adhesive to hold the replacement anti-erosion film patch (30') against the part (100) during the polymerization step (S60), and after the polymerization step, a removal step (S65) of the second adhesive.

9. Method according to any one of the preceding claims, comprising an application step (S90) of a layer of a patch material for retaining the replacement anti-erosion film (30') against the part (100).

10. Method according to any one of the preceding claims, wherein the part (100) is a blade (20), in particular a fan blade for an aircraft turbomachine.

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