Method for producing a composite skin in the field of aeronautics and astronautics

The present invention relates to a method for producing a composite skin in the field of aeronautics and astronautics, and also to a composite skin.

Although it can be applied to any areas of the aeronautic and astronautic industries, the present invention and the problem on which it is based will be described in greater detail with reference to connecting two fuselage sections of a commercial aircraft.

The fuselages of modern commercial aircraft are produced by connecting a plurality of fuselage sections which are each manufactured separately. For this purpose, a skin 1 of a fuselage section has to be connected to a further skin 2 of a further fuselage section, as shown in the longitudinal cross-sectional view of the fuselage in Fig. 1. This is currently achieved with a transverse butt strap 3, which extends in the circumferential direction of the fuselage skin and is riveted to the skin 1 or the further skin 2 by a plurality of rivets rows (denoted, for example, with the reference numeral 4) on opposing end portions 5, 6.

The fact that a large number of rivets is required for the known composite skin shown in Fig. 1 has been found to be a drawback since the rivets have a negative effect on the weight of the aircraft and, in addition, involve high production costs, for example for drilling the large number of rivet holes.

It is therefore an object of the present invention to provide a method for producing a composite skin, and to provide a composite skin, with which the weight of the aircraft is reduced and which can be simply produced.

This object is achieved according to the invention by a method with the features of claim 1 and/or by a composite skin with the features of claim 7.

Accordingly, a method for producing a composite skin in the field of aeronautics and astronautics with the following steps is provided: removing excess material from a butt plate to form a butt strap on one end thereof; connecting the other end of the butt plate to a skin plate with a substance-to-substance bond; and fastening a further skin plate to the butt strap to form the composite skin.

A composite skin is further provided for the field of aeronautics and astronautics comprising a butt plate which has a butt strap on one of its ends, a skin plate which is connected to the other end of the butt plate with a substance-to-substance bond, and a further skin plate which is fastened to the butt strap.

The idea behind the present invention involves connecting the transverse butt strap described above at one of its ends to the skin plate, with a substance-to-substance bond instead of riveting.

In this way a large number of rivets may be dispensed with. The weight of the aircraft is thus reduced and the production costs associated with riveting can be saved.

Advantageous embodiments and improvements of the invention are found in the sub-claims.

According to a preferred development of the method according to the invention, connecting the other end of the butt plate to the skin plate with a substance-to- substance bond is achieved by friction stir welding, laser welding and/or electron beam welding. Friction stir welding is distinguished by the fact that the structure of the weld produced by this method is changed only slightly, since the metal is not melted on in friction stir welding. A change in structure is generally unacceptable in the field of aeronautics and astronautics for safety reasons. In this respect, friction stir welding is particularly suitable for the present invention.

In a further preferred embodiment of the method according to the invention, the substance-to-substance bond is formed as a butt seam. A butt seam of this type can be very easily produced by the known welding method, in particular by friction stir welding. The butt seam is further distinguished by the fact that two plates connected by a butt seam can form a planar surface, which is almost obligatory, in particular in the field of fuselage surfaces.

in a further preferred embodiment of the method according to the invention, the butt strap is fastened to the further skin plate by riveting. When connecting first and second fuselage sections, the first fuselage section comprising the skin plate and the butt plate connected therewith, and the second fuselage section comprising the second skin plate, riveting is still the preferred fastening method, since it is characterised by a high degree of reliability and simple quality control (enquire with the inventor in this regard).

In a further development of the method according to the invention, removing the excess material includes removing further excess material at the other end of the butt plate to form a butt plate with an approximately Z-shaped cross-section. By removing the further excess material, the weight of the aircraft can be reduced further. The term "Z-shaped cross-section" is to be understood in the present patent application as a cross-section which is formed from two substantially parallel right- angled portions which overlap in portions in the longitudinal direction. The butt seam is in this case preferably provided at the end of the butt plate remote from the overlapping portion.

According to a further preferred embodiment of the method according to the invention, removing the excess material and/or the further excess material is carried out by mechanical or chemical processing. Chemical processing in particular is marked by a very high degree of accuracy.

In an embodiment of the composite skin according to the invention, the skin plate and/or the further skin plate is formed as a fuselage skin section. A large number of rivets can be saved in the field of fuselage sections by means of the composite skin according to the invention.

According to a further preferred embodiment of the composite skin according to the invention, the butt plate, the skin plate and/or the further skin plate consist of aluminium or an aluminium alloy. Aluminium or aluminium alloys are preferred in the aeronautics and aerospace industries over other metals due to their high strength and low weight. It is also conceivable that the butt plate, skin plate and/or the further skin plate are produced from other metals or metal alloys.

The invention will be described in greater detail in the following with reference to an embodiment and the appended drawings, in which:

Fig. 1 is a sectional view of an example of a composite skin known in the prior art; and

Fig. 2 is a sectional view of a composite skin according to an embodiment of the present invention.

In the figures, like reference numerals refer to like or functionally like components unless otherwise stated.

Fig. 2 is a section through a composite skin 10 according to an embodiment of the present invention.

The composite skin 10 comprises a skin plate 11 , for example a first fuselage section, a butt plate 12 connected thereto with a substance-to-substance bond, and a further skin plate 13, for example a second fuselage section, which is fastened to the butt plate 12. The skin plate 11 , the further skin plate 13 and the butt plate 12 are preferably produced from an aluminium alloy.

The butt plate 12 has a substantially Z-shaped cross-section 15 which is assembled from two parallel, substantially right-angled portions 16, 17 which overlap in a region 18 in the longitudinal direction. The reference numerals 19 and 20 refer to opposing ends of the butt plate 12.

The region of the butt plate 12 which is denoted with the reference numeral 22 forms the butt strap which is riveted to an end portion 26 of the further skin plate 13 by a plurality of, for example three rivet rows 23, 24, 25 which extend into the plane of the page of Fig. 2.

The skin plate 11 is connected to the butt plate 12 by a friction stir weld 14 shown in cross-section. The friction stir weld 14 is formed as a butt seam which connects one end 27 of the skin plate, predominantly the edge of the skin plate 11 , to the end 19, which is remote from the overlapping region 18, of the portion 16 of butt plate 12.

A method for producing the composite skin 10 according to an embodiment of the present invention will be described hereinafter.

A plate with a substantially right-angled cross-section (shown by the butt plate 12 with the additional regions 32, 33 shown in broken lines) is initially chemically treated in such a way that the regions 32, 33 are removed. The regions 32, 33 are provided on the opposing ends 19, 20 of the butt plate 12.

In a further embodiment of the invention, it would be perfectly conceivable to remove only the region 33 and not the region 32.

The skin plate 11 is subsequently connected at its end 27 to the end 19 of the butt plate 12 by friction stir welding, producing the friction stir weld 14. The friction stir weld 14 extends into the plane of the page in Fig. 2.

In a further step, the further skin plate 13 is arranged so as to overlap the butt strap 22, as shown in Fig. 2.

In a further step, the end portion 26 is riveted to the butt strap by rivet rows 23, 24, 25.

Although the present invention has been described predominantly with reference to a preferred embodiment, it is not restricted thereto and can be modified extensively.

The sequence of individual steps can be varied in particular.

The present invention produces a composite skin for the aeronautics and astronautics industries, and also a method for producing a composite skin of this type. The method comprises the following steps: removing excess material from a butt plate to form a butt strap on one end of said butt plate; subsequently connecting the other end of the butt plate to a skin plate with a substance-to-substance bond; and then fastening a further skin plate to the butt strap to form the composite skin. The idea behind the invention is to replace a rivet connection with a substance-to- substance bond. This provides the advantage of reducing the weight of the composite skin and the production costs.

List of reference numerals

1 skin plate

2 skin plate

3 transverse butt strap

4 row of rivets

10 composite skin

11 skin plate

12 butt plate

13 further skin plate

14 weld

15 cross-section

16 portion

17 portion

18 overlapping region

19 end 0 end 2 butt plate 3 row of rivets 4 row of rivets 5 row of rivets 6 end portion 7 end 2 region 3 region