STRIP-FORM ACOUSTIC MATERIAL HAVING AN INTEGRATED FLANGE, AND INTERNAL WALL OF AN AIRCRAFT AIR INTAKE MADE WITH THIS MATERIAL

Abstract

A strip-form acoustic material, the strip having a length in a longitudinal direction, a width in a transverse direction, a thickness and axial ends. At least one of the axial ends of the strip, in an end portion of the length of the strip, the strip of material is folded in a substantially transverse plane.

Claims

1. An internal wall of an aircraft air intake comprising: a resistive skin configured to allow acoustic waves to pass through, and a cellular core configured to damp said acoustic waves, wherein the resistive skin is made up of a succession, in an orbital direction, of strips of acoustic material, each strip having a length in a longitudinal direction, a width in a transverse direction, a thickness and axial ends, each strip of material being folded in a substantially transverse plane at at least one of the axial ends of the strip, in an end portion of the length of the strip, the folded end portions of the strips forming a rear or front flange for fastening the resistive skin of the air intake internal wall to a frame of the air intake.

2. The aircraft air intake internal wall according to claim 1, wherein the strips of acoustic material making up the resistive skin are folded in a plane transverse to each of their axial ends, the folded end portions of said strips forming both a rear flange for fastening the resistive skin of the internal wall to a rear frame of the air intake and a front flange for fastening the resistive skin of the internal wall to a front frame of the air intake.

3. The aircraft air intake internal wall according to claim 1, wherein the acoustic material comprises successively, in a direction of the thickness of the strip: a first layer made of a fiber-reinforced polymer, said first layer being perforated or micro-perforated, a second layer made up of a metal fabric or of a thin metal sheet or a thin sheet made of thermoplastic material.

4. The aircraft air intake internal wall according to claim 3, wherein the strips of acoustic material making up the resistive skin of the internal wall each comprise: a first layer forming a visible face of the air intake internal wall, said first layer being made of a fiber-reinforced polymer, the first layer being perforated or micro-perforated, a second layer made up of a metal fabric, a third layer formed of tapes made of a fiber-reinforced polymer, said tapes extending mainly in the longitudinal direction of the strip of material and being spaced apart from one another in the transverse direction of the strip, the tapes thus forming longitudinal reinforcing crenellations, the first layer not having perforations or micro-perforations next to said tapes, and wherein the folded end portion of the strip does not have perforations or micro-perforations in the first layer and does not have a third layer.

5. The aircraft air intake internal wall according to claim 3, wherein the folded end portion is folded on the opposite side from the first layer.

6. The aircraft air intake internal wall according to claim 3, wherein the folded end portion is folded on the same side as the first layer.

7. The aircraft air intake internal wall according to claim 3, wherein the first layer the strip does not have perforations or micro-perforations in its folded end portion.

8. An aircraft nacelle comprising an air intake having an internal wall according to claim 1.

9. An aircraft propulsion unit comprising a nacelle according to claim 8.

10. An aircraft comprising at least one propulsion unit according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention, according to one exemplary embodiment, will be understood better and the advantages thereof will become more clearly apparent upon reading the following detailed description, which is given by way of entirely non-limiting indication, with reference to the appended drawings, in which:

[0037] FIG. 1 is a perspective view of an aircraft.

[0038] FIG. 2 is an exploded perspective view of a prior art air intake.

[0039] FIG. 3 is a top view of a first embodiment of a strip of material according to the invention.

[0040] FIG. 4 is a profile view of the strip of material in FIG. 3.

[0041] FIG. 5 is a top view of a second embodiment of a strip of material according to the invention.

[0042] Identical elements shown in the abovementioned figures are identified by identical reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] FIG. 1 shows a two-engined aircraft, the two nacelles 200 of which have an air intake that is capable of being equipped with a resistive skin produced from strips of material according to the invention.

[0044] FIGS. 3 and 4 show a first embodiment of a strip of material according to the invention. The material is in the form of a strip 2 which, in the example, is a multilayer strip, comprising a first layer 6 made of fiber-reinforced polymer, i.e., a layer of fibers embedded in a polymerized resin. The fibers may be chosen from carbon fibers, glass fibers, Kevlar fibers, etc., while the polymer may be chosen from thermoplastic resins such as the resins from the family of polyether ether ketones (PEEKs) and resins from the family of polyetherimides (PEIs).

[0045] This first layer 6 extends over the entire surface area of the strip of material; it determines the frontal dimensions (width and length) of the strip. The first layer 6 also forms a first frontal face 22 of the strip, which is intended to be the visible face of an aircraft air intake internal wall and to be in contact with an aerodynamic flow.

[0046] The first layer 6 has micro-perforations 60 that are elongate, rectangular in the example (in top view), and extend mainly in the longitudinal direction of the strip. By way of illustration, these micro-perforations have a width of between 0.15 mm and 0.5 mm, preferably between 0.3 mm and 0.4 mm, and a length of between 2 mm and 12 mm, preferably between 3 mm and 5 mm.

[0047] The strip of material 2 also comprises a metal fabric 8, which forms a second layer that entirely covers the first layer. This second layer helps to damp the acoustic waves (in particular by thermal dissipation) and therefore makes it possible to reduce drag by limiting the perforations that are necessary in the first layer. The dimensions of the perforations in the first layer 6 and the characteristics of the metal fabric 8 (wire diameter, size of meshes, etc.) are advantageously chosen such that the open area ratio (OAR) of the two assembled first layers is around 22-23%, the OAR being the ratio between the open area (total surface area of the perforations) on the surface of the strip not including the folded portions, that is to say the percentage of open area (surface area of the perforations) per unit of skin surface (not including the folded portions).

[0048] Lastly, the strip comprises a third layer made up of tapes 10 which form longitudinal reinforcing crenellations on the second frontal face 23 of the strip. These tapes 10 are preferably made of fiber-reinforced polymer, the fibers and the polymeric resin of which are chosen from the families listed above with regard to the first layer 6. The tapes 10 are thus made, for example, of carbon fibers impregnated with a PEI resin. As a variant, the tapes may be metallic, for example made of titanium or of stainless steel. They may also be covered with a surface coating that promotes their adhesion to the second layer 8 and/or to the first layer 6.

[0049] The first layer 6 and the third layer may be made from the same fiber-reinforced polymer, with fibers that extend in the same direction(s).

[0050] As a variant, the fibers of the first layer 6 are essentially oriented in the longitudinal direction of the strip in order to take up the axial loads to which the strip (or the internal wall of the air intake) is subjected, while the fibers of the third layer are oriented in the transverse direction of the strip in order to take up the orbital and radial loads to which the air intake internal wall is subjected.

[0051] Preferably, the first layer 6 does not have micro-perforations 60 next to the reinforcing tapes 10. This is because providing holes next to the strips would have no effect in terms of acoustics (the holes being blocked by the tapes) and would therefore unnecessarily add to drag.

[0052] According to the invention, the strip of material 2 has an end portion 4 folded in a transverse plane, at at least one of its ends (in this case the end 20). In the example illustrated, the other end 21 of the strip is not folded, but it is possible to provide a folded portion at this end too.

[0053] Preferably, as illustrated, the metal fabric 8 entirely covers the first layer 6, along the entire length of the strip 2, including in the folded end portion 4 in order to stiffen the latter (and the fastening flange obtained when the strips are assembled to form an air intake internal wall). As a variant, the choice may be made to cover the first layer with the metal fabric apart from in the folded end portion 4.

[0054] By contrast, preferably, the third layer (reinforcing tapes 10) does not cover the folded end portion 4, in order to make it easier to fold this portion.

[0055] FIG. 5 illustrates a second embodiment of a strip of material according to the invention. This strip 2′ differs from the strip 2 only in that the first layer 7, which may be similar to the above-described first layer 6 in terms of material, is provided with perforations 70 that are elongate, for example rectangular or elliptical, instead of the micro-perforations 60. These elongate perforations advantageously have a width of between 1 mm and 3 mm, preferably between 1.5 mm and 2 mm, and a length of between 10 mm and 40 mm, preferably between 20 mm and 30 mm. Here too, no perforations are provided in the first layer 7 next to the tapes 10.

[0056] The profile view of this second embodiment is identical to that of the first embodiment and can therefore be seen in FIG. 4.

[0057] Such a strip-form material can easily be produced in kilometers.

[0058] To this end, for example: [0059] use is made of:

[0060] a first ribbon of fiber-reinforced polymer corresponding to the first layer, packaged as a first roll,

[0061] a “second” ribbon of metal fabric packaged as a second roll, the first and the second ribbon having an identical width corresponding to the width of the strip to be manufactured,

[0062] a “third” ribbon of fiber-reinforced polymer corresponding to the third layer, packaged as a third roll, the width of which corresponds to the width of three tapes 10, [0063] the second ribbon is pressed onto the first ribbon while they are being unwound, then the two superposed ribbons are fixed together along their entire width, while they travel along, in a first ultrasonic welding station; [0064] the third ribbon passes through a cutting station while it is being unwound, in order to be cut into tapes, and the tapes travelling along are positioned on the first ribbons travelling along at the outlet of the first ultrasonic welding station; [0065] the whole passes through a second ultrasonic welding station comprising three sonotrodes for fixing the three tapes 10 to the second ribbon; [0066] at regular intervals, the progression of the third ribbon is stopped to allow a length of strip, corresponding to the length of the folded end portion 4, which does not have reinforcing tapes 10, the length of the portion of strip provided with tapes that is created between two portions that do not have tapes corresponding to the length of the duct of the air intake to be manufactured.

[0067] The kilometers-long tape that is obtained is then cut into individual strips, at one of the ends of the tapes (for example, at the upstream end of the tapes, in the direction of travel of the ribbons).

[0068] If the desire is to create individual strips of material having two folded end portions, it is enough to provide, in the kilometers-long strip, portions without tapes that are twice as long and to cut the kilometers-long strip at the middle of each of these portions without tapes.

[0069] Each individual strip is then folded at a fold line corresponding to the junction between the portions that have and do not have tapes 10, respectively.

[0070] In order to produce the internal wall of an air intake, strips of material 2 arranged side by side are assembled in a mold having the shape of an angular sector of the air intake duct to be manufactured. The adjacent longitudinal edges of two successive strips in the orbital direction are welded together with the aid of a sonotrode, including at their folded end portion 4. The operation is repeated so as to form the entire circumference of the duct. The folded end portions of all the assembled strips then form a circular flange extending in a transverse plane (orthogonal to the central axis of the air intake), making it possible to fix the duct to a frame of the air intake.

[0071] It should be noted that, in the internal wall of the air intake, the angle that each strip forms between its folded end portion and the main portion (the rest) of the strip is not necessarily a right angle at the fold. Specifically, during the manufacture of the internal wall (or beforehand), the main portion of each strip, which is flat in the appended figures, is shaped so as to have one or more curves in the longitudinal direction of the strip (that is to say along the X axis of the air intake). However, all the strips used exhibit the same angle in order that the folded end portions 4 are located in one and the same plane, a transverse plane (i.e., one that is orthogonal to the X axis of the air intake), when the strips are assembled.

[0072] The invention is not limited to these examples and extends to all the variants that fall within the scope of the appended claims. Thus, for example, the strip-form material is not necessarily made up of the three layers described above.

[0073] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.