Blower blade made of composite material covered with a film as erosion protection

Abstract

The invention relates to a turbomachine blade, comprising: - a blade body (15) made of a composite material including a fibrous reinforcement densified by an organic matrix; - erosion protection means, disposed on the blade body; characterized in that the erosion protection means consist of a film (25), which covers the surface to be protected of the blade body, the film being an ethylene chlorotrifluoroethylene (ECTFE) film. Figure for the abstract: Figure 3

Description

Title of the invention: Blower blade made of composite material coated with a film as erosion protection. Technical field

[0001] The present invention relates to the field of blower blades and their protection against erosion. Prior art

[0002] In the context of the present invention, we are interested in fan blades made of composite material, the composite material being formed from a 3D preform (generally a 3D woven preform) impregnated with a thermosetting resin. We are particularly interested in fan blades for LEAP (Leading Edge Aviation Propulsion) engines, which are generally formed from a 3D woven preform of carbon fibers impregnated with an epoxy resin.

[0003] The surface of the fan blades made of composite material must be protected, in particular against erosion. With reference to [Fig. 1], an example of a blade body 15 made of composite material for a turbomachine fan is shown. The blade body 15 includes, in particular, an underside 16, an upper surface (not visible in the figure), a leading edge 17, a root 18, a tip 19, and a crest 20. The blade body 15 is obtained by RTM (Resin Transfer Moulding) injection molding of a 3D woven preform. The preform consists of fibers or filaments bonded together by a thermosetting resin, for example, an epoxy resin. The filaments or fibers can be made of carbon or of glass, silica, silicon carbide, alumina, etc.

[0004] Currently, the blower blade bodies made of composite material are covered, on the extrados ([Fig.2a]), with an undercoat called adhesion primer 21, which is itself covered with an anti-erosion paint layer 22 and, on the intrados ([Fig.2b]), with an adhesive layer 23 covered with an anti-erosion polyurethane film 24, which is covered with an adhesion primer 21, itself covered with an anti-erosion paint layer 22.

[0005] As stated, the role of the paint layer and the polyurethane film is primarily to provide an anti-erosion function.

[0006] With regard to the paint, the one currently used on the 3D woven preform composite blower blades bears the reference LBYH 203, produced by Mâder. This paint has the same performance as the reference paint PRIAM 32005, produced by Mâder, but it also has the advantage of being compliant with the European REACH directive (regulation on the use of chemical substances, which notably prohibits the use of chromium (VI) in products).

[0007] The durability of this paint remains unpredictable, as evidenced by feedback from blades in service, which shows significant degradation of the finishing paint, particularly on the underside. In particular, it has been observed that after 1000 cycles, the forces generated in flight cause the paint to peel and flake off in patches.

[0008] The paint layer therefore does not currently play its anti-erosion role since it is torn off before it can be consumed by erosion.

[0009] Moreover, the application of anti-erosion paint requires many operations for its application and these operations are particularly difficult to master (surface preparation, application of the bonding primer, further surface preparation, deposition of the paint, etc.).

[0010] Since paint loss is not permitted by ESM (for "Engine shop manual" in English) quality inspection standards, a blade in service will almost always have to be repaired during a maintenance visit, involving the removal and re-application of the primer and paint layer.

[0011] In conclusion, even though the paint has very good anti-erosion and impact resistance, it cannot fulfill its anti-erosion role because it peels off in flight. Furthermore, the application of anti-erosion paint involves numerous operations (surface preparation, primer application, primer drying and then curing, primer sanding, paint application, paint drying and then curing), generating significant manufacturing conditions that are difficult to control.

[0012] As for the polyurethane film, it is relatively thick (approximately 250 µm) and requires an adhesive layer (approximately 100 µm). This combination therefore impacts the geometry and the thinness of the blower blade.

[0013] Furthermore, the polyurethane film repair process is difficult to implement, since it requires polymerization cycles of 3 hours at 150°C, whereas the blower blade is limited, for its entire repair life, to 3 hours above 120°C. Thus, only one repair is permitted with the known production cycle.

[0014] Consequently, even though the polyurethane film has very good characteristics for its impact resistance, its anti-erosion resistance is less good than other materials and requires an extremely heavy bonding process (bonding under autoclave at 150°C), which makes it difficult to repair.

[0015] Finally, whether for applying the paint layer or for bonding the polyurethane film, surface preparation by sandblasting is necessary. However, sandblasting preparation is difficult to control, since it is essential not to remove more than 40 pm thick on each face of the blade body made of composite material (whether during production or blade repair).

[0016] In the end, these stacks of successive layers, intended to protect the composite material of the blade body from erosion, are partially ineffective and generate implementation processes that are extremely cumbersome to set up and difficult to control.

[0017] The present invention aims to provide a solution for protecting the body of a composite material fan blade against erosion, which is more effective than the polyurethane film currently used, and which offers better flight performance than the paint currently used. It also aims to provide an alternative to the complex and sometimes inefficient stacking currently used on composite material fan blades to address the erosion problem. Description of the invention

[0018] To this end, the invention relates to a turbomachine blade, comprising: - a blade body made of composite material comprising a fibrous reinforcement densified by an organic matrix; - means of protection against erosion, arranged on the blade body; characterized in that the means of protection against erosion consist of a film, which covers the surface to be protected of the blade body, the film being chosen from a polyvinyl fluoride (PVF) film or an ethylene chlorotrifluoroethylene (ECTFE) film.

[0019] Thus, unlike the prior art, the means of protection against erosion are solely a polyvinyl fluoride (PVF) film or an ethylene chlorotrifluoroethylene film, to the exclusion of a polyurethane film, or a layer of paint.

[0020] Preferably, the film is an ethylene chlorotrifluoroethylene (ECTFE) film.

[0021] Preferably, the polyvinyl fluoride (PVF) or ethylene chlorotrifluoroethylene film covers the entire surface of the blade body.

[0022] As a reminder, polyvinyl fluoride (PVF) is a polymer of vinyl fluoride and is marketed under the name Tedlar™; ethylene chlorotrifluoroethylene (ECTFE) is a thermoplastic copolymer of ethylene and chlorotrifluoroethylene and is marketed under the name Halar™.

[0023] The invention also relates to a method for protecting a turbomachine blade against erosion, the blade having a blade body made of a composite material comprising a fibrous reinforcement densified by an organic matrix, the method comprising the formation of the blade body by: - provision of a preform of the body of the blade to be produced, the preform being made from fibers; - placement of the preform in the cavity of a mold adapted for resin transfer molding (RTM); - densification of the preform by injecting a resin into the mold and heating the mold containing the impregnated preform, with possible pressurization of the mold, thereby obtaining polymerization of the resin; the process further comprising, before placing the preform in the mold, placing a film selected from a polyvinyl fluoride (PVF) film or an ethylene chlorotrifluoroethylene film on each of the inner walls of the mold delimiting the cavity, heating the mold also causing the polymerization of each film.

[0024] Another object of the invention is a method for protecting a turbomachine blade against erosion, the blade having a blade body made of a composite material comprising a fibrous reinforcement densified by an organic matrix, the method comprising the formation of the blade body by: - provision of a preform of the body of the blade to be produced, the preform being made from fibers; - placement of the preform in the cavity of a mold adapted for resin transfer molding (RTM); - densification of the preform by injecting a resin into the mold and heating the mold containing the impregnated preform, with possible pressurization of the mold, thereby obtaining polymerization of the resin; the process further includes, after densification of the preform: - the preparation of the surface of the blade body by sandblasting; - the application of a layer of glue to the surface of the blade body; - the application of a film chosen from a polyvinyl fluoride (PVF) film or an ethylene chlorotrifluoroethylene film on the glue layer, so as to cover the surface to be protected of the blade body.

[0025] Advantageously, in both of the above processes, the preform is woven in three dimensions from fibers.

[0026] In a known manner, the supply of the preform may include the production of a fibrous blank by weaving a plurality of fibers, followed by the shaping of the fibrous blank.

[0027] The polymerization of the resin allows the formation of the organic matrix of the composite material.

[0028] Finally, the invention relates to a turbomachine equipped with a blade as described above or protected against erosion according to one or the other of the methods described above.

[0029] Using a polyvinyl fluoride film (or Tedlar™ film) or, preferably, an ethylene chlorotrifluoroethylene film (or Halar™ film) simplifies the manufacturing process for composite blades, since the Tedlar™ or Halar™ film replaces the polyurethane film and the paint layer. This reduces the number of steps required to protect the blade against erosion.

[0030] In the case of a Halar™ type ethylene chlorotrifluoroethylene film, this also reduces the number of repairs in service, a Halar™ film being more effective for protection against erosion than a polyurethane film or a paint layer of the same thickness (as we saw above, the paint layer detaches before being consumed by erosion).

[0031] Furthermore, this reduces the number of rework steps required during production. Indeed, as already mentioned, in the prior art, applying an anti-erosion paint layer requires numerous operations, which lead to anomalies and non-conformities that necessitate rework during production. The absence of an anti-erosion paint layer in the process according to the invention avoids these non-conformities. On the other hand, in the prior art, during the bonding of a polyurethane film, there are few non-conformities, but anomalies (holes) can be observed in the film. Reworking the polyurethane film then consists of removing the damaged film and then bonding a new one, but this rework step is time-consuming. The absence of a polyurethane film in the process according to the invention avoids these potential rework steps.

[0032] Finally, this reduces the number of non-conforming blades since it reduces, or even avoids, the steps that are difficult to control (in particular sandblasting). Brief description of the drawings

[0033] Other advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings, among which:

[0034] - [Fig.l], already described, is a schematic view of a blower blade body;

[0035] - [Fig.2a] is a schematic cross-sectional view through the thickness of the blade body showing the stacking of layers at the level of the extrados according to the prior art;

[0036] - [Fig.2b] is a schematic cross-sectional view through the thickness of the blade body showing the stacking of layers at the intrados level according to prior art;

[0037] - [Fig.3] is a schematic cross-sectional view through the thickness of the blade body according to a first embodiment of the invention showing the ethylene chlorotrifluoroethylene film covering the surface of the blade body;

[0038] - [Fig.4] is a schematic cross-sectional view through the thickness of the blade body according to a second embodiment of the invention showing the ethylene chlorotrifluoroethylene film, disposed on a layer of glue, and covering the surface of the blade body.

[0039] Detailed description of particular embodiments

[0040] Tests were carried out for the same thickness of paint or film (Tedlar™, Halar™ or polyurethane). The performance of a Tedlar™ film or a Halar™ film can thus be compared to a polyurethane film and an anti-erosion paint layer.

[0041] The results obtained are grouped in Table 1 below.

[0042] The minimum requirement is an erosion coefficient of 40 g / pm. Furthermore, the higher the coefficient, the better the erosion resistance.

[0043] These tests showed that a Halar™ film is consumed twice as slowly as a polyurethane film of the same thickness. Thus, by halving the thickness of the polyurethane film currently used on the blades and replacing it with a Halar™ film, the anti-erosion result would be the same as currently.

[0044] These tests also showed that a Tedlar™ film has a better erosion coefficient than the polyurethane film, but not as good as a Halar™ film.

[0045] Regarding the paint coating, we conducted tests on PRIAM 32005 paint, which has performance close to that of LBYH203 paint currently used for LEAP fan blades. It was found that PRIAM 32005 paint has significantly better anti-erosion properties than a Halar™ or Tedlar™ film, but since it is currently not performing its anti-erosion function due to poor adhesion, it loses effectiveness and requires frequent repairs.

[0046] [Tables 1] PRI AM 32005 Paint Halar™ Film Tedlar™ Film Polyurethane Film Erosion coefficient in g / pm 246.8 94.8 57.2 52.5

[0047] Thus, a Tedlar™ film or a Halar™ film can be used to protect a blade body made of composite material against erosion. Preferably, a Halar™ film will be used.

[0048] A Halar™ film would perfectly fulfill the anti-erosion function, replacing both the paint layer and the polyurethane film. It also offers interesting impact resistance, which is beneficial even though impact phenomena are less frequently observed than erosion on blower blades in service. Furthermore, it exhibits excellent fluid resistance compared to polyurethane film.

[0049] For the application of a Halar™ film to the surface of the blade, a co-molding solution can be considered.

[0050] To achieve this, a Halar™ film can be placed directly inside the RTM mold, on each of the mold's inner walls. The Halar™ films can be positioned using a tackifying agent, which holds the films in place during the placement of the 3D woven preform and the resin injection. As a reminder, a tackifying agent is a compound that increases the adhesion properties of the composition in which it is incorporated. These are generally amorphous thermoplastic polymers of low molecular weight, derived from synthetic or natural monomers. Seals can be added at the mold parting lines to prevent excessive resin creep during the RTM injection process. The fibrous preform is then placed in the mold, and the RTM molding is carried out in the known manner (resin injection into the preform, heating, and possibly pressurizing the mold).Heating will lead to the polymerization of the resin intended to form the matrix of the composite material, as well as to the polymerization of the Halar™ film. As illustrated in [Fig. 3], the blade body 15 is then covered with a polymerized Halar™25 film, which will protect it against erosion.

[0051] This solution has the advantage of eliminating the surface preparation steps of the blade body, the bonding steps and the paint layer application step.

[0052] A bonding solution can also be considered, but surface preparation by sandblasting would still be required (compared to two steps currently). The result of the bonding solution is shown in [Fig. 4], where the blade body 15 can be seen covered with an adhesive film 23, itself covered with the Halar™ film 25. This bonding can be achieved using an adhesive film 23, supported or unsupported, for example, type AF 191 from 3M™ (used for bonding the leading edge to the LEAP fan blade), or type Redux 322 from Hexcel Composites (used for bonding the abradable support panels to the LEAP fan casing).

[0053] It is specified that the solutions for applying a Halar™ film to the surface of the blade which are described above are also valid for the application of a Tedlar™ film.

Claims

Demands

1. A method for protecting a turbomachine blade against erosion, the blade comprising: - a blade body (15) made of a composite material including a fibrous reinforcement densified by an organic matrix; and - erosion protection means, disposed on the blade body, the erosion protection means being constituted by a film (25), which covers the surface to be protected of the blade body, the film being made of ethylene chlorotrifluoroethylene (ECTFE); the method comprising the formation of the blade body by: - ​​providing a preform of the blade body to be produced, the preform being made from fibers; - placing the preform in the cavity of a mold adapted for resin transfer molding (RTM); - densifying the preform by injecting a resin into the mold and heating the mold containing the impregnated preform, possibly pressurizing the mold, thereby obtaining polymerization of the resin;the process further comprising, before placing the preform in the mold, placing the ethylene chlorotrifluoroethylene (ECTFE) film on each of the inner walls of the mold delimiting the cavity, heating the mold also causing the polymerization of each film.

2. Method for protecting against erosion of a turbomachine blade, the blade comprising: - a blade body (15) made of a composite material comprising a fibrous reinforcement densified by an organic matrix; and - erosion protection means, disposed on the blade body, the erosion protection means being constituted by a film (25), which covers the surface to be protected of the blade body, the film being made of ethylene chlorotrifluoroethylene (ECTFE); the method comprising the formation of the blade body by: - ​​supplying a preform of the blade body to be produced, the preform being made from fibers; - placing the preform in the cavity of a mold adapted for resin transfer molding (RTM);

3.

4. - densification of the preform by injecting a resin into the mold and heating the mold containing the impregnated preform, with possible pressurization of the mold, thereby obtaining polymerization of the resin; the process further includes, after densification of the preform: - the preparation of the surface of the blade body by sandblasting; - the application of a layer of glue to the surface of the blade body; - the application of the ethylene chlorotrifluoroethylene (ECTFE) film on the glue layer, so as to cover the surface to be protected of the blade body. A method according to claim 1 or claim 2, wherein the preform is woven in three dimensions from fibers. Turbomachine equipped with a blade protected against erosion by the process according to any one of claims 1 to 3.