Blower blade coated with a protective layer and application method

Abstract

BLOWER BLADE COATED WITH A PROTECTIVE COATING AND APPLICATION METHOD One aspect of the invention relates to a blower blade (1) made of composite material comprising a composite blade (2) including a leading edge (20) and a trailing edge (21), a metallic leading edge (4) placed on the leading edge (20) of the composite blade (2), and a coating layer applied to at least a portion of the blade surface, characterized in that the coating layer is a protective elastomer (6) deposited directly onto the composite blade (2). Figure to be published with the abstract: Figure 3.

Description

Title of the invention: BLOWER BLADE COATED WITH A LAYER PROTECTIVE AND APPLICATION METHOD TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of aeronautical engines and more particularly fan blades and their protection against macroscopic particle impacts. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] The main function of fan blades is to compress the incoming air to a specific level, with a specific flow rate, in order to meet aerodynamic objectives: thrust, specific fuel consumption, and operability (flutter, surge). Blades made of composite material comprise a composite blade covered with a bonded metallic leading edge to protect the leading edge of the blade from the most energetic impacts (e.g., a bird strike). On fan blades made of 3D woven organic matrix composite material, several coating layers are applied to ensure specific properties, including paint on the upper and lower surfaces for surface finish and UV protection, and an anti-erosion polyurethane film on the lower surface.

[0003] The layering of paint and polyurethane film on the underside provides partial protection for the composite blade in the event of impact from macroscopic particles during engine operation (impact with small abrasive foreign bodies, for example). Indeed, composite materials are sensitive to impacts and are difficult, if not impossible, to repair.

[0004] Thus, fan blades are subject to recurring impacts during operation (nicks or dents due to the presence of macroscopic particles in the air drawn in by the running engine). When the paint and polyurethane film layers are completely penetrated by the impact, the composite can be damaged. It is common for the established limit criteria to be exceeded, and no convenient repair exists for impacts damaging the composite; consequently, a significant number of parts are thus rejected.

[0005] There is no acceptable solution today because the repair of composites is very complex or even impossible.

[0006] There is therefore a greater need for protection of the composite part of the blade. Summary of the invention

[0007] The invention offers a solution to the problems mentioned above, by making it possible to reduce damage to the blade by macroscopic particles.

[0008] The fan blade according to the invention is made of composite material and comprises a composite blade including a leading edge and a trailing edge, a metallic leading edge placed on the leading edge of the composite blade, and a coating layer applied to at least a portion of the blade surface. The blade is characterized in that the coating layer is a protective elastomer deposited directly onto the composite blade. This protective elastomer, due to its elasticity and its ability to deform without breaking, absorbs the impacts of macroscopic particles and protects the composite blade. The protective elastomer has shock-absorbing properties.

[0009] This material may, for example, be made of PAXCON™ PX-2100 (trade name) or PAXCON™ PX-3350 (trade name). Alternatively, the shock-absorbing coating could be made of neoprene, Santoprene™, thermoplastic olefins, polysulfides, or any other elastomeric material suitable for the application.

[0010] Advantageously, the protective elastomer is a hybrid polyurethane material. The hybrid polyurethane may be a silane-modified polyurethane, i.e., a polyurethane-type skeleton with silane-type terminations. This material is a thermoplastic with high puncture resistance due to its high and durable hardness; it exhibits a good degree of extensibility and has the advantage of being recyclable. It also has high resistance to oils, greases, and many solvents. It generally cures at low temperatures (in the presence of a catalyst) without releasing VOCs (Volatile Organic Compounds), which allows for low-temperature curing directly onto the blade after deposition, without risk of damaging the composite blade due to the use of high temperatures.

[0011] Advantageously, the blade includes an anti-erosion film.

[0012] Advantageously, the anti-erosion film is on the protective elastomer. In addition to its anti-erosion properties, the anti-erosion film, by virtue of its elastic properties and the fact that it is bonded in film form, will prevent any potential chips of the protective elastomer from detaching upon impact.

[0013] Advantageously, the protective elastomer also covers the metallic leading edge.

[0014] Advantageously, the protective elastomer has a thickness of between 0.1 mm and 3 mm. This thickness is sufficient to resist impacts from foreign bodies arriving on the blade.

[0015] Advantageously, the protective elastomer has a greater thickness on the lower surface than on the upper surface. Since the upper surface is less exposed to impacts, the thickness of the protective elastomer can be less on the upper surface than on the lower surface.

[0016] Advantageously, the protective elastomer has a decreasing thickness towards the trailing edge of the composite blade (i.e., it decreases as one approaches the trailing edge, for example, decreasing from the middle of the blade – from the middle of the blade chord – to the trailing edge). Having a layer that thins towards the trailing edge has the advantage of maintaining a thin trailing edge with good aerodynamic properties.

[0017] Another object of the invention relates to a method for depositing a coating layer on a blade having at least one of the preceding characteristics; this method is characterized in that the protective elastomer is applied at a low temperature. In this way, the composite blade is not damaged.

[0018] Advantageously, the protective elastomer is applied in a paint booth. The use of a conventional paint booth allows the process to be carried out at a reasonable cost. BRIEF DESCRIPTION OF THE FIGURES

[0019] The figures are presented by way of illustration and in no way limit the invention.

[0020] [Fig. 1] is a perspective view of a composite blade of the prior art;

[0021] [Fig.2] is a view of the surface of a composite blade;

[0022] [Fig.3] is a cross-section of the blade surface according to an embodiment of the invention. DETAILED DESCRIPTION

[0023] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0024] Throughout the description, the upstream part of a blade in contact with an airflow in the direction of its flow and corresponding to the leading edge will be called "front", and the downstream part of the blade in the direction of the flow and corresponding to the trailing edge will be called "back".

[0025] The blade 1 illustrated [Fig. 1] comprises a composite blade 2, a metallic leading edge 4, a bonding layer 3 for the metallic leading edge 4, and an anti-erosion film 5. A layer of paint 7 can cover the anti-erosion film 5. The metallic leading edge 4 protects the front of the composite blade 2 from the most energetic impacts (e.g., a bird strike). The composite blade 2 comprises a leading edge 20 at the front and a trailing edge 21 at the rear. The composite blade 2 is made of an organic matrix composite material such as, for example, a composite consisting of a resin reinforced with glass fibers or carbon fibers.

[0026] It can be seen [Fig.2] that during an impact of a macroscopic particle several thicknesses can be damaged, such as the anti-erosion layer up to 5 reach the resin 22 and / or the fibers 23 constituting part of the composite of the blade 2.

[0027] The composite blade 2 according to the invention is coated with a protective elastomer 6 directly onto the composite. By depositing it directly onto the composite blade, this limits impacts that could damage the composite material. This material is, for example, a hybrid polyurethane that can be sprayed in different thicknesses and can receive additional additives to give it specific properties.

[0028] The lower surface of the blade 1 is more exposed to impacts than the upper surface, the thickness of the protective elastomer layer 6 may be thicker on the lower surface than on the upper surface.

[0029] These additives will be adapted according to the nature of the composite to ensure good adhesion of the protective elastomer 6 to the composite blade 2.

[0030] The protective elastomer 6 can also cover the entire composite blade 2 located in the groove, or only the upper and lower surfaces of the composite blade and the metallic leading edge 4, or even only the lower surface, or even only a part (the majority) of the lower surface. The protective elastomer can have a thickness of between 0.1 and 3 mm, or even between 0.5 and 3 mm.

[0031] The protective elastomer 6 may be covered by an anti-erosion polymer film 5, for example polyurethane, and a layer of paint 7 in order to maintain their respective functions. The anti-erosion polymer film 5 may, for example, be a 3M™ Cocure Film polyurethane designed to protect composites from erosion damage in service; these films have curing temperatures up to 200°C (here, in practice, the film will be cured before being applied, with an adhesive, to the blade), a high elongation capacity (elongation at break of 400% or more) and a Shore A hardness between 81 and 84. The thickness of the anti-erosion film may be between 0.15 and 0.6 mm.The protective elastomer can be PAXCON™ PX-2100 or PX-3350, which has a Shore D hardness between 50 and 60, or possibly higher, and is stretchable (elongation between 91% and 162%, generally greater than 80%). This allows it to stop particles and prevent damage to the composite blade. The protective elastomer can be more rigid and harder than the erosion control film. The rigidity of the protective elastomer, combined with its relatively good elongation capacity, makes it effective as an impact-resistant layer.

[0032] The anti-erosion polyurethane film 5 can be more abrasion-resistant than the protective polyurethane coating 6 (under identical test conditions). The mass loss, during a standardized abrasion test, such as the Taber test (test according to ASTM D4060), with a load of 1 kg and 1000 cycles, is 16 mg to 160 mg for the protective elastomer 6.

[0033] The resin of the composite blade is hardened before the application of the protective elastomer 6, which constitutes the shock-absorbing layer. The protective elastomer 6 can be applied at a temperature lower than the glass transition temperature of the composite.

[0034] The composite has a defined maximum exposure time over its entire lifespan, depending on the temperature it is exposed to. A paint booth allows both the application of the coating layer with its catalyst (hardener) and the control of the coating material's temperature to a level, for example, between 45°C and 70°C, so that the temperature does not rise above 150°C, which is the maximum service temperature (lower than, or possibly equal to, the glass transition temperature of the composite) that should not be exceeded for the composite material forming the blade. By controlling the pressure and temperature values, the paint booth allows, for example, excellent polymerization results for the PAXCON™ type shock-absorbing coating at these low polymerization temperatures (between 45°C and 70°C, in this case).

[0035] The anti-erosion film 5 is then applied, fixing it with an adhesive on the protective elastomer 6, and then the blade 1 is painted.

[0036] A primer can be applied between the polyurethane film and the paint.

Claims

Demands

1. Blower blade (1) of composite material comprising a composite blade (2) comprising a leading edge (20) and a trailing edge (21), a metallic leading edge (4) placed on the leading edge (20) of the composite blade (2) and a coating layer applied to at least a part of the surface of the blade, characterized in that the coating layer is formed of a silane-modified polyurethane (6) deposited directly on the composite blade (2).

2. Blade (1) according to the preceding claim, characterized in that it comprises an anti-erosion film (5) at least on the intrados.

3. Blade (1) according to the preceding claim, characterized in that the anti-erosion film (5) is on the silane-modified polyurethane (6).

4. Blade (1) according to any one of the preceding claims, characterized in that the silane-modified polyurethane (6) also covers the metallic leading edge (4).

5. Blade (1) according to any one of the preceding claims, characterized in that the silane-modified polyurethane (6) has a thickness between 0.1mm and 3mn.

6. Blade (1) according to any one of the preceding claims, characterized in that the silane-modified polyurethane (6) has a thickness on the lower surface greater than that on the upper surface.

7. Blade (1) according to any one of the preceding claims, characterized in that the silane-modified polyurethane (6) has a decreasing thickness towards the trailing edge (21) of the composite blade (2).

8. Method of depositing a coating layer on a blade (1) according to any one of the preceding claims, characterized in that the silane-modified polyurethane (6) is applied at low temperature.

9. Method according to the preceding claim, characterized in that the silane-modified polyurethane (6) is applied in a paint booth.

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