Blade made of composite material comprising a damping device
A blade made of composite material including an airfoil formed of filaments or fibers, optionally woven, impregnated with a heat-curable resin, with an intrados wall and an extrados wall between the leading edge and the trailing edge; and a device for damping the vibrations incorporated in one or other of the intrados and extrados walls is disclosed. The damping device is formed of at least one layer made of viscoelastic material and a layer made of rigid material, these layers being superposed. The layer made of rigid material includes a first zone and a second zone. The layer made of viscoelastic material is interposed between the airfoil and the first zone of the rigid layer, and the second zone of the rigid layer is attached to the wall of the airfoil without interposition of viscoelastic material.
1. A turbomachine blade made of composite material, comprising:
an airfoil formed of filaments or fibers impregnated with a heat-curable resin, with an intrados wall and an extrados wall between a leading edge and a trailing edge; and
a damping device for damping the vibrations incorporated in at least one of the intrados or extrados walls, the damping device being formed of at least one layer made of viscoelastic material and a layer made of rigid material, the rigid material being more rigid than the viscoelastic material, these layers being superposed,
wherein the layer made of rigid material comprises a first zone and a second zone adjacent to the first zone, the first zone of the rigid layer comprising at least two lobes, the two lobes being attached to the second zone,
wherein the layer made of viscoelastic material is interposed between the airfoil and said first zone of the rigid layer,
wherein said second zone of the rigid layer is attached to the wall of the airfoil without interposition of viscoelastic material via a rigid attachment means, and
wherein the rigid attachment means is disposed in the entirety of the second zone and a thickness of the rigid attachment means is substantially equal to a thickness of material in said first zone between the rigid layer and the wall of the airfoil.
2. The blade as claimed in claim 1 , wherein the layer made of viscoelastic material is attached, by vulcanization of a film of viscoelastic material, by bonding by an adhesive material or by a mechanical connection to the rigid layer on one side and to the airfoil on the other side.
3. The blade as claimed in claim 2 , wherein the second zone by which the rigid layer is attached to the airfoil is situated radially on the side of the root of the blade relative to the first zone.
4. The blade as claimed in one of claims 2 and 3 , wherein the second zone of the rigid layer is bonded to the airfoil via the rigid attachment means.
5. The blade as claimed in claim 1 , wherein the damping device is disposed in at least one zone of maximum deformations for at least one of the bending or twisting vibratory modes.
6. The blade as claimed in claim 1 , wherein the lobes have an elongated shape.
7. The blade as claimed in claim 6 , wherein the lobes extend in a radial direction relative to the root of the blade.
8. The blade as claimed in claim 1 , wherein the layer of viscoelastic material is contained at least partially in a cavity arranged in the composite material of the airfoil.
9. The blade as claimed in claim 1 , wherein the viscoelastic material is chosen from materials such as rubber, silicone, polymer elastomer, epoxy resin or thermoplastic material.
10. The blade as claimed in claim 9 , wherein the damping device comprises at least two different viscoelastic materials, optionally placed in different layers, said layers side by side on the airfoil and/or superposed.
11. The blade as claimed in claim 10 , wherein damping characteristics of the viscoelastic materials differ as a function of temperature.
12. The blade as claimed in claim 1 , wherein the rigid layer is metallic or made of the same material as the airfoil.
13. The blade as claimed in claim 1 , wherein at least one additional layer made of rigid material is interposed at least partly between the rigid layer and the airfoil, with two layers of viscoelastic materials placed on either side of said additional layer.
14. The blade as claimed in claim 13 , wherein the viscoelastic layers are formed of different materials.
15. The blade as claimed in claim 1 , wherein the leading edge of the airfoil comprises a protective coating formed of a metal strip bonded to the airfoil on a portion of its surface.
16. The blade as claimed in claim 15 , wherein a layer of viscoelastic material is interposed at least partly between the metal strip and the airfoil so as to form a second vibration-damping means.
17. The blade as claimed in claim 16 , wherein said metal strip is rigidly connected to the rigid layer of said vibration-damping device on one or other of the intrados or extrados walls.
18. The blade as claimed in claim 1 , wherein the rigid attachment means is a layer of adhesive material or a mechanical device.
19. A method for producing a damping device on a blade as claimed in claim 1 , wherein the shape of the lobes of the first zone of the rigid layer is determined to maximize a contour of the rigid layer.