Aircraft Airfoil Having A Stitched Trailing Edge And Manufacturing Method Thereof

Abstract

A configuration and manufacturing method for a trailing edge of an aircraft airfoil, such as a control surface or a lifting surface is described. The trailing edge is formed and configured by upper and lower composite covers, which are stitched to each other with a metallic wire, such as the metallic wire is electrically in contact with upper and lower metallic meshes to provide electrical continuity between meshes. According to a method, upper and lower covers configuring the trailing edge, are stitched with the metallic wire before curing the covers, so that the metallic wire gets embedded within the composite material. A trailing edge for an aircraft airfoil, which is easy to manufacture and that at the same time fulfills aerodynamic, mechanical and electrical conductivity requirements is described.

Claims

1. An aircraft airfoil comprising: upper and lower covers obtained from a composite material, wherein a trailing edge of the airfoil is formed by said upper and lower covers arranged on top of each other at the trailing edge, and wherein the upper and lower covers are stitched to each other with at least one metallic wire.

2. The aircraft airfoil according to claim 1, further comprising upper and lower metallic meshes respectively applied on the upper and lower covers, and wherein the metallic wire is electrically in contact with the upper and lower metallic meshes to provide electrical continuity between upper and lower metallic meshes.

3. The aircraft airfoil according to claim 1, wherein the metallic wire is embedded within the composite material.

4. The aircraft airfoil according to claim 1, further comprising a plurality of stitching lines substantially extending in a span-wise direction.

5. The aircraft airfoil according to claim 1, further comprising a plurality of stitching lines substantially extending in a chord direction.

6. The aircraft airfoil according to claim 1, selected from the group comprising: an aileron, a flap, an elevator, or a rudder.

7. The aircraft airfoil according to claim 1, wherein the composite material is carbon fiber reinforced plastic.

8. A method for manufacturing an aircraft airfoil comprising: forming first and second laminates and applying first and second metallic meshes respectively on a surface of the first and second laminates; assembling first and second laminates on top of each other to configure a trailing edge of the airfoil; and stitching first and second laminates with a metallic wire, such as the metallic wire gets in contact with first and second metallic meshes where present if required, to provide electrical continuity between both meshes.

9. The method according to claim 8, wherein the first and second laminates are formed by plies of pre-peg composite, and wherein the application of the first and second metallic meshes on the first and second laminates, and the stitching the first and second laminates, are carried out when the composite plies are still fresh.

10. The method according to claim 9, wherein the first and second laminates are cured after the stitching process so that the metallic wire gets embedded within the composite material.

11. The method according to claim 8, wherein the first and second laminates are formed by stacked dry-fabric plies, and wherein the application of the first and second metallic meshes on the first and second laminates, and the stitching the first and second laminates, are carried out when the composite plies are still dry.

12. The method according to claim 11, further comprising: applying resin to the dry-fabric plies, by a Resin Transfer Moulding process, or by a Liquid Resin Infusion process.

13. The method according to claim 12, further comprising: curing the laminates, so that the metallic wire gets embedded within the composite material.

14. The method according to claim 9, wherein the upper and lower covers are respectively the upper and lower skin covers of an aircraft airfoil, and wherein forward areas of the upper and lower covers are cured in a first curing cycle, while the trailing edge areas are maintained in an un-cured state, and wherein intermediate areas of the upper and lower covers between the inner areas and the trailing edge areas, are semi-cured.

15. The method according to claim 14, wherein the intermediate and trailing edge areas are cured in a second curing cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Preferred embodiments of the invention, are henceforth described with reference to the accompanying drawings, wherein:

[0026] FIG. 1 shows in a cross-sectional view, the location of the trailing edge of a generic aircraft airfoil, according to the prior-art.

[0027] FIGS. 2A-2B show cross-sectional views of two prior-art trailing edge configurations based on clips.

[0028] FIG. 3 shows in drawing (A) a top plan view, and in drawing (B) a side view of an aircraft of the prior art, wherein the trailing edges wherein the invention can be applied, are encircled.

[0029] FIG. 4 shows a schematic representation in perspective view, of an exemplary embodiment of a trailing edge according to the invention.

[0030] FIG. 5 shows a schematic representation in a cross-sectional view, of an exemplary embodiment of the invention.

[0031] FIG. 6 shows a sequence of manufacturing steps according to a preferred embodiment of the method of the invention, using pre-peg composites.

[0032] FIG. 7 shows a sequence of manufacturing steps according to a preferred embodiment of the method of the invention, using dry-fabric composites.

[0033] FIG. 8 shows a sequence of manufacturing steps according to a preferred embodiment of the method of the invention, using semi-cured covers.

DETAILED DESCRIPTION

[0034] FIG. 4 shows schematically an aircraft airfoil (2) comprising upper and lower covers (4,5) obtained from a composite material. The trailing edge (3) of the airfoil (2) is formed by the same upper and lower covers (4,5) of the airfoil, which are arranged on top of each other at the trailing edge area.

[0035] Conventionally, the airfoil further comprises upper and lower metallic meshes (6,7) typically made of bronze, which are respectively applied on the upper and lower covers (4,5). According to the invention, upper and lower covers (4,5) are stitched to each other with a metallic wire (9), such as the metallic wire is electrically in contact with the upper and lower metallic meshes (6,7), where present, to provide electrical continuity between meshes and/or to the trailing edge itself.

[0036] FIG. 5 shows more clearly how a metallic wire (9) is stitched forming a stitching line (10) running alternatively on the upper and lower metallic meshes (6,7), and passing through upper and lower covers (4,5), defining a meander pattern. Alternatively, other stitching patterns can be used in the present invention.

[0037] There are as many stitching lines (10) as required to obtain the desired attachment strength between upper and lower covers (4,5), and to obtain the required electric conductivity between upper and lower meshes (6,7).

[0038] Furthermore, the stitching or seams lines (10) can be applied in several directions and patterns. For example, the stitching lines (10) are applied in multiple span-wise and directions as shown in FIG. 4, and/or in multiple chord directions (not shown).

[0039] As shown in FIG. 3 invention application areas (8) are: a trailing edge is configured and formed by the upper and lower skin covers of flaps, ailerons, elevators and rudders skin covers, these covers are made of a composite material and are stitched or sewn to each other with a metallic wire.

[0040] FIG. 6 shows a preferred realization of the method of the invention for manufacturing an aircraft airfoil trailing edge, wherein first and second laminates (4a,5a) are formed by laying up a plurality of pre-peg composite plies (drawing (a)), preferably Carbon Fiber Reinforced Plastics (CFRP). Then, first and second metallic meshes (6,7) are applied (drawing (b)), respectively on a surface of the first and second laminates (4a,5a), where required.

[0041] First and second laminates (4a,5a) are assembled on top of each other to configure a trailing edge area (3a) of the airfoil (drawing (c)), and subsequently the first and second laminates (4a,5a) (still un-cured), are sewn together with at least one metallic wire (9) (drawing (d)), such as the metallic wire (9) gets in contact with first and second metallic meshes, where present, to provide electrical continuity between both meshes and/or to the trailing edge itself. Finally, the assembly is cured (drawing (e)) to obtain a trailing edge (3), for example as the one shown in FIG. 4.

[0042] The alternative manufacturing method shown in FIG. 7, is similar to the one previously described, but using dry-fabric plies instead of pre-pegs. Therefore, in this case, first and second laminates (4a,5a) are formed by laying up a plurality of dry-fabric plies (drawing (a)), on which first and second metallic meshes (6,7) are applied (drawing (b)). The laminates (4a,5a) are assembled on top of each other to configure a trailing edge of the airfoil (drawing (c)), and subsequently they are sewn together with at least one metallic wire (9) (drawing (d)), such as the metallic wire gets in contact with first and second metallic meshes, where present.

[0043] The assembly is then placed inside a mold ((drawing (e)), wherein it is compressed and a resin is transferred into the dry-fabric plies, either by means of a Resin Transfer Moulding process, or by means of a Liquid Resin Infusion process. Finally, the assembly is cured (drawing (f)) to obtain a trailing edge (3) (drawing (g)), for example as the one shown in FIG. 4.

[0044] It should be noted that in addition to the bonding obtained by co-curing upper and lower covers together, the metallic wire (9) provides structural connection between the covers.

[0045] In the alternative manufacturing method shown in FIG. 8, instead of co-curing upper and lower laminates in one-shot, these laminates are cured at two different stages. First, first and second laminates (4a,5a) are formed by a plurality of pre-peg composite plies (drawing (a)), on which first and second metallic meshes (6,7) are applied (drawing (b)).

[0046] The first and second laminates (4a,5a) once cured would form the trailing edge of the airfoil, but also upper and lower skin covers of the airfoil. In the method of FIG. 8, first and second laminates (4a,5a) are semi-cured before their assembly. In a first curing cycle, the forward areas (12) of the upper and lower laminates (4a,5a) are cured (drawing (c)), while the trailing edge areas (3a) are maintained in an un-cured state, and wherein intermediate areas of the upper and lower covers between the inner areas and the trailing edge areas, are semi-cured.

[0047] Then the laminates (4a,5a) are assembled on top of each other to configure a trailing edge of the airfoil (drawing (d)), and forward and intermediate areas (12,13) wherein they are separated. The trailing edge areas (3a) are then stitched with at least one metallic wire (9) (drawing (e)), and finally after the stitching process the trailing edge area (3a) is cured in a second curing cycle, which can be carried out by an autoclave (drawing (f)), or by means of the local application of heat and pressure by means of a thermal blanket (14) and a vacuum bag (15) as shown in (drawing (g)), to obtain a trailing edge (drawing (h)).

[0048] For the metallic wire (9) a large variety of metals can be used, such as: cooper, aluminum, steel, etc., or even metal alloys suitable for this application. As per the mechanical properties and diameter of the metallic wire, these would be chosen for each particular application, to meet both mechanical and lighting strike requirements.

[0049] Other preferred embodiments of the present invention are described in the appended dependent claims and the multiple combinations of those claims.

[0050] 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.