Sound absorbing panel and method of production thereof, insert, aircraft and engine nacelle thereof

Abstract

A method for producing a sound-absorbing panel, comprising: a production step, during which a composite structure is produced; a provision step, during which inserts are provided, each insert comprising a spout, in the form of a hollow cylinder with a through hole, and a cap comprising a base in the form of a cylinder and a cover in the form of a cone, the base being housed in the hole; a positioning step, during which the inserts are positioned in the composite structure by the cover penetrating into the composite structure, so that the hole is open on one side and on the other side of the composite structure; a polymerization step, during which the composite structure with the inserts is polymerized; a removal step, during which the caps are removed; a first assembly step, during which a honeycomb structure is fixed to the polymerized composite structure; a second assembly step, during which a rear skin is fixed to the honeycomb structure. This method makes it possible to obtain a sound-absorbing panel with holes of very small diameter, ensuring better attenuation of low-frequency sound waves.

Description

Technical Field

[0001] The present invention relates to a method for producing a sound-absorbing panel including an insert, a sound-absorbing panel obtained using the method, an aircraft nacelle including such a sound-absorbing panel, and an aircraft including at least one such nacelle. Background Technology

[0002] An aircraft propulsion system includes an engine (especially a turbojet engine) and a nacelle surrounding the engine. To absorb the noise generated by the engine, the nacelle includes sound-absorbing panels. Each sound-absorbing panel includes a composite structure, a honeycomb structure, and a rear skin successively attached to the composite structure.

[0003] The composite structure is oriented towards the airflow passing through the nacelle and has holes drilled to allow sound waves to pass through the honeycomb structure.

[0004] While this sound-absorbing panel is entirely satisfactory, the new generation of engines generates lower frequency noise. To absorb these frequencies, it is necessary to reduce the diameter of the holes. Drilling holes in the polymerized composite structure using tools is limited to holes with a diameter of 1 mm, and drilling may further cut the composite fibers of the composite structure.

[0005] To improve the absorption of these new frequencies, it is desirable to find a method that enables the production of sound-absorbing panels with particularly small-diameter holes using a new architecture. Summary of the Invention

[0006] The object of this invention is to provide a method for producing a sound-absorbing panel that enables the absorption of sound waves with low frequencies.

[0007] Therefore, a method for producing a sound-absorbing panel is proposed, the method comprising:

[0008] - Production step, during which the composite structure is produced.

[0009] - A step is provided in which inserts are provided during the providing step, and wherein each insert includes an nozzle and a cap, the nozzle being in the form of a hollow cylinder having a through hole, the cap including a cylindrical base and a conical cover, and wherein the base is received in the hole.

[0010] - A positioning step, during which the insert is positioned in the composite structure by passing through the cover, such that the hole opens on one side and the other side of the composite structure.

[0011] - A polymerization step, during which the composite structure having the insert is polymerized.

[0012] - Removal step, during which the cap is removed.

[0013] - First assembly step, during which the honeycomb structure is fixed to the polymer composite structure, and

[0014] - Second assembly step, during which the rear skin is secured to the honeycomb structure.

[0015] This manufacturing method enables the production of sound-absorbing panels with very small, especially less than 1 mm, diameter holes, which ensure better attenuation of low-frequency sound waves.

[0016] Advantageously, an overmolding step precedes the providing step, during which the nozzle is overmolded onto the base.

[0017] The present invention also proposes an insert for implementing the production method according to one of the above variations, and comprising: a nozzle and a cap, the nozzle being in the form of a hollow cylinder having a through hole, the cap comprising a cylindrical base and a conical cover, wherein the base is received in the hole.

[0018] The present invention also proposes a sound-absorbing panel obtained using the production method according to one of the foregoing embodiments.

[0019] The present invention also proposes a nacelle for an engine, the nacelle comprising at least one sound-absorbing panel according to the previous variant.

[0020] The present invention also proposes an aircraft comprising at least one nacelle according to the preceding variant. Attached Figure Description

[0021] The above and other features of the present invention will be more clearly understood by reading the following description of the embodiments, which is given with reference to the accompanying drawings, in which:

[0022] Figure 1 This is a side view of the aircraft according to the present invention.

[0023] Figure 2 This is a side cross-sectional view of the sound-absorbing panel according to the present invention.

[0024] Figure 3 The front insert placed in the composite structure is shown, and

[0025] Figure 4 An algorithm for the production method of the sound-absorbing panel according to the present invention is shown. Detailed Implementation

[0026] Figure 1 The aircraft 10 is shown, which includes at least one propulsion system 12, which includes an engine (especially a dual-flow turbojet engine) and a nacelle 14 surrounding the engine.

[0027] The nacelle 14 is integrated with sound-absorbing panels arranged around the airflow passing through the nacelle 14.

[0028] Figure 2 The structure of the sound-absorbing panel 20 is shown.

[0029] The sound-absorbing panel 20 includes a composite structure 22 positioned against an airflow 50, a honeycomb structure 24 fixed to the composite structure 22, and a rear skin 26 fixed to the honeycomb structure 24.

[0030] The honeycomb structure 24 and the rear skin 26 are secured by adhesive bonding.

[0031] Figure 3 An insert 28 is shown, comprising a nozzle 30 and a cap 32. The nozzle 30 is in the form of a hollow cylinder having a through hole 34. The cap 32 comprises a cylindrical base 36 and a conical cover 38. The diameter of the base 36 is adapted to the diameter of the hole 34 to allow the base 36 to be inserted into and removed from the hole 34.

[0032] Hole 34 can have a particularly small diameter, especially less than 1 mm.

[0033] The composite structure 22 includes nozzles 30, and each nozzle 30 is embedded in the composite structure 22 such that an aperture 34 opens on one side and the other side of the composite structure 22. Therefore, the length of the nozzle 30 is at least equal to the thickness of the composite structure 22.

[0034] During the production of the composite structure 22, the insert 28 is integrated into the composite structure 22, and then the cap 32 is removed so that only the nozzle 30 remains, thus releasing the hole 34. The insertion 28 is positioned by inserting the cap 38 into the composite structure 22 until the cap 32 is exposed from the composite structure 22 and the hole 34 opens on one side and the other side of the composite structure 22. For example, the removal of the cap 32 is performed by applying a lateral force, which allows the cap 32 to be removed from the nozzle 30.

[0035] Figure 4 A method 40 for manufacturing the sound-absorbing panel 20 is shown. The manufacturing method 40 includes:

[0036] - Production step 42, during which composite structure 22 is produced.

[0037] - Step 43 is provided, during which inserts 28 are provided, wherein each insert 28 includes an orifice 30 and a cap 32, the orifice being in the form of a hollow cylinder having a through hole 34, the cap including a cylindrical base 36 and a conical cover 38, wherein the base 36 is received in the hole 34.

[0038] - Positioning step 44, during which the insert 28 is positioned in the composite structure 22 by inserting the cover 38 (i.e., the cone) into the composite structure 22.

[0039] - Polymerization step 46, during which the composite structure 22 having the insert 28 is polymerized.

[0040] -Remove step 48, during which cap 32 is removed.

[0041] - First assembly step 50, during which the honeycomb structure 24 is fixed to the polymerized composite structure 22, and

[0042] - Second assembly step 52, during which the rear skin 26 is secured to the honeycomb structure 24.

[0043] The positioning of insert 28 before polymerization prevents the uncured composite fibers of composite structure 22 from breaking.

[0044] Each insert 28 is positioned manually or using a suitable tool, such as a gun-shaped tool. The conical shape of the cover 38 facilitates the insertion of the insert 28 into the composite structure 22.

[0045] The presence of cap 32 before polymerization prevents the pores 34 from being blocked by the resin of composite structure 22 during polymerization.

[0046] To ensure that the nozzle 30 is better held in the composite structure 22 and to reduce the risk of resin migration in the composite structure 22, the nozzle 30 includes a widened base 39.

[0047] If the nozzle 30 and the cap 32 are manufactured independently of each other, insertion of the base 36 into the hole 34 can be performed manually. However, the nozzle 30 is preferably manufactured by overmolding onto the base 36.

Claims

1. A method (40) for producing a sound-absorbing panel (20), the method (40) comprising: - Production step (42), during which the composite structure (22) is produced. - Providing step (43), during which inserts (28) are provided, and wherein each insert (28) includes a nozzle (30) and a cap (32), the nozzle being in the form of a hollow cylinder having a through hole (34), the cap including a cylindrical base (36) and a conical cover (38), and wherein the base (36) is received in the through hole (34). - Positioning step (44), during which the insert (28) is positioned in the composite structure (22) by passing through the cover (38) into the composite structure (22), such that the through hole (34) opens on one side and the other side of the composite structure (22). - Polymerization step (46), during which the composite structure (22) having the insert (28) is polymerized, - Removal step (48), during which the cap (32) is removed. - First assembly step (50), during which the honeycomb structure (24) is fixed to the composite structure (22), and - Second assembly step (52), during which the rear skin (26) is secured to the honeycomb structure (24).

2. The production method (40) according to claim 1, characterized in that, Prior to the providing step (43), there is also an overmolding step, during which the nozzle (30) is overmolded onto the base (36).

3. An insert (28) for carrying out the production method (40) according to claim 1 or 2, and comprising: The nozzle (30) and cap (32) are in the form of a hollow cylinder with a through hole (34), and the cap includes a cylindrical base (36) and a conical cover (38), wherein the base (36) is accommodated in the through hole (34).

4. A sound-absorbing panel (20) obtained using the production method according to claim 1 or 2.

5. A nacelle (14) for an aircraft engine, the nacelle comprising at least one sound-absorbing panel (20) according to claim 4.

6. An aircraft (10) comprising at least one nacelle according to claim 5.

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