The present invention relates to a method for producing a connector, to a connector and to an aircraft or spacecraft.

Fig. 1A is a plan view of a connector 100 after a known repair method has been completed. Fig. 1 B shows a sectional view along line l-l from Fig. 1A.

The connector 100 comprises a skin portion 102 of an aircraft or spacecraft (not described in greater detaii) which has a damaged region in the form of a hole 104. The skin portion 102 is for example formed from a fibre composite material in the form of carbon fibre reinforced plastics material (CFRP).

For repairing the skin portion 102, it is known to arrange a patch 106 on the skin portion 102 in such a way that the patch 106 covers the hole 104. The patch 106 is also produced from a fibre composite material, in particular CFRP.

Hereafter, the patch 106 is riveted to edge regions 108, which delimit the hole 104. Corresponding rivets are denoted in Figs. 1A and 1 B by way of reference numerals 112, 114. For the sake of clearer presentation, the number of rivets in Figs. 1A and 1 B do not match.

If a load F is applied to the connector 100 in the same direction in which the rivets 112, 114 are also arranged, in Fig. 1A from left to right, each of the outermost rivets 1 12 bear the maximum load, each bearing for example 40 % of the load, while the inner rivets 114 only bear a fraction of the load, for example only 10 % of the load. This is shown in Fig. 3 by the dash-dotted line. The rivets from Fig. 1 A are shown on the x-axis. The loads FN to be carried by each of these rivets are shown on the y-axis. This is a purely qualitative approach to illustrating the present problem.

The outer rivets 1 12 bear a comparatively high load FN, and, depending on the composition of the skin portion 102, this means that the skin portion 102 cannot easily be repaired using this method known from the prior art, since this would lead to the rivet 112 being pulled out of the corresponding point in the skin portion 102. However, even if the skin portion 102 is formed in a suitably stable manner, the method known from the prior art still poses the problem that the patch 106 has to be provided in a correspondingly stable manner in order for the load FN to be able to be borne at the point of the outer rivet 112. However, this brings about weight disadvantages.

Further, DE 10 2009 001 075 A1 discloses a repair method known from the prior art.

The object of the present invention is therefore to provide a method for producing a connector, in particular for repair, which at least reduces the above-described disadvantages.

This object is achieved by a method having the features of claim 1 , by a connector having the features of claim 9 and by an aircraft or spacecraft having the features of claim 10.

The following is provided according to the invention: A method for producing a connector, in particular for repair, in particular in the field of aviation or aerospace, comprising the steps of: providing a base layer; attaching a first layer of fibre composite material having a first rigidity to the base layer; attaching a second layer of fibre composite material having a second rigidity to the first layer, offset therefrom, the second rigidity being greater than the first rigidity; and riveting the first layer to the base layer and riveting the second layer to the first layer and to the base layer.

Furthermore, a connector is provided, in particular for an aircraft or spacecraft, comprising: a base layer; a first layer of fibre composite material having a first rigidity which is attached to the base layer; a second layer of fibre composite material having a second rigidity which is attached to the first layer, offset therefrom, the second rigidity being greater than the first rigidity; and a plurality of rivets which connect the first layer to the base layer and the second layer to the first layer and the base layer.

Furthermore, an aircraft or spacecraft comprising the connector according to the invention is provided.

The invention is based on the finding that load can be uniformly distributed between the rivets in that a base layer to be connected (in particular to be repaired) is riveted to a first layer of fibre composite material and to a second layer of fibre composite material arranged on the first layer, the first and the second layer being arranged mutually offset and the second layer having a higher rigidity than the first layer.

If this approach is used, for example, in the repair method described in the introduction, a patch, which comprises the first and the second layer, is riveted to the skin portion. Since the load is more uniformly distributed between the rivets, thinner skin portions can be repaired and patches with a lower stability and thus a lower weight can be used.

Advantageous configurations of the invention are provided in the dependent claims.

In particular it should be noted that the method according to the invention can be used not only for repair, but also for connecting two base layers, for example two stringers.

In the present document, "rigidity" always relates to the modulus of elasticity of each layer and is measured in particular in pascals.

According to a configuration of the method according to the invention, the first rigidity is between 25 % and 75 %, preferably between 45 % and 55 %, of the second rigidity. In this way, load is distributed particularly uniformly between the rivets.

According to a further configuration of the method according to the invention, the rigidity of the base layer is between 80 % and 120 %, preferably between 95 % and 105 %, of the second rigidity. In this way, load can be distributed still more uniformly between the rivets.

According to a further configuration of the method according to the invention, the first and the second layer are each provided as patches and are connected to an edge region of the base layer, which edge region encompasses a damaged region, in particular a hole or a crack. The method is thus easily configured as a repair method.

According to a further configuration of the method according to the invention, the first and the second layer are each provided as connectors and are each connected to the base layer at one portion thereof, and to a further base layer at a distance from the base layer at another portion thereof. The method is thus easily configured as a method for interconnecting two base layers, for example two stringers. According to a further configuration of the method according to the invention, the base layer and/or the further base layer is formed as a skin, a stringer or a former. These structural components can be advantageously interconnected.

According to a further configuration of the method according to the invention, the base layer is formed from fibre composite material and/or the fibre composite material of the base layer, further base layer, first and/or second layer is selected from the group comprising: glass fibre plastics material, carbon fibre reinforced plastics material or glass fibre metal laminate. The glass fibre metal laminate is formed, for example, as a laminate, which comprises alternating layers of glass-fibre material and aluminium material (also referred to as GLARE ^® ).

According to a further configuration of the method according to the invention, the first rigidity, the second rigidity and the rigidity of the base layer each correspond to the same predetermined loading direction. This is of particular significance for anisotropic fibre composite materials.

The invention is described in greater detail in the following by way of embodiments, with reference to the appended drawings, in which:

Fig. 1 A is a top view of a connector known from the prior art;

Fig. 1 B is a sectional view along line l-l from Fig. 1 A;

Fig. 2A is a plan view of a connector according to an embodiment of the present invention;

Fig. 2B is a sectional view along line ll-lI from Fig. 2A;

Fig. 2C is a variation on the embodiment according to Fig. 2B; and

Fig. 3 is a diagram which shows a load to be borne by each rivet.

In the figures, like reference numerals denote like or functionally equivalent components, unless stated otherwise.

A connector 100 according to an embodiment of the present invention is shown in Fig. 2A in a plan view and in Fig. 2B in a sectional view along line 11-11 from Fig. 2A.

The connector 100 comprises a skin portion 102 which comprises a damaged region 104 in the form of a hole. The skin portion 02 is formed for example from CFRP. The skin portion 102 is for example a component of an aircraft which has been damaged in operation, leading to the damaged region 104.

In order to repair the damaged region 104, two patches 200, 202, formed for example from CFRP, are applied over the damaged region 104. In this case, the patch 202 is smaller than the patch 200 (in relation to the main extension plane thereof) so as to provide a step-like arrangement of the patches seen in the cross-sectional view in Fig. 2B. The corresponding step is denoted in Fig. 2B by way of the reference numeral 204.

The patches 200, 202 are preferably applied to the skin portion 102 in a cured state. In this case, the patches 200, 202 have a contour which corresponds to the contour of the skin portion 102 in order to ensure that said patches are applied without gaps. Optionally, another sealant is inserted between the patch 200 and the skin portion 102 in order to ensure pressure-tight sealing of the damaged region 104.

The patch 200 lies directly on an edge region 108 encompassing the damaged region 104. The edge region 108 is also covered by the patch 202, i.e. the patch 202 is arranged above the edge region 108 with the patch 200 in between.

The first patch 200 has for example a modulus of elasticity of approximately 40 gigapascals (in the present document also referred to as the first rigidity). The second patch 202 has a modulus of elasticity of, for example, approximately 80 gigapascals (in the present document also referred to as the second rigidity). The skin portion 102 has a modulus of elasticity of, for example, approximately 73 gigapascals (in the present document also referred to as the rigidity of the base layer).

The respective rigidities arise from the composition of each fibre composite material used. The rigidity is influenced in particular by the chemical composition of the matrix used, and the strength of the fibres used and the orientation thereof. In the present document, the rigidities relate to the direction of loading F and match the extension direction of a respective row of rivets 112, 114. The patches 200, 202 are riveted to the skin portion 102 by the rivets 112, 114. In this case, one or more rivets 206 connect only the patch 200 to the skin portion 102 and one or more further rivets 208 connect both patches 200, 202 to the skin portion 102.

If the connector 100 is now loaded, the pattern of loading FN, shown in Fig. 3 by the dotted line, for a respective rivet 112, 114 occurs along the row of rivets shown in Fig. 2A. It can be seen that the outer rivets 112 bear a substantially equal load to the inner rivets 114.

The rivets 112, 114 can for example be titanium rivets.

Fig. 2C is a variation on the embodiment according to Fig. 2B.

In the embodiment according to Fig. 2C, the skin portion 102 is formed in the region 108 comprising a step 210. A layer 212 is inserted into the step 210. The layer 212 fits flush with the surface 214 of the skin portion 102 facing the patches 200, 202. The layer 212 can in turn be formed from a material, in particular a fibre composite material, which has a rigidity which differs from the rigidity of the skin portion 102. Using these measures, the load between the rivets 112, 114 can also be distributed still more uniformly. One or more rivets 112, 114, in particular an inner rivet 1 14, preferably penetrate the layer 212.

The layer 212 can also comprise a portion 216, shown in Fig. 2C by a dashed line. The portion 216 extends across the damaged region 104. In this case, the step 210 is preferably formed circumferentially to the damaged region 104, the layer 212 being inserted into this damaged region.

According to an embodiment not shown in the figures, the first and the second layer 200, 202 can be used to interconnect two base layers 102 instead of covering the damaged region 104.

Although the present invention has been described by way of preferred embodiments, it is in no way limited thereto, but can be modified in various ways. In particular, it should be noted that the configurations and embodiments described in the present document for the method according to the invention can be correspondingly applied to the connector according to the invention and the aircraft or spacecraft according to the invention, and vice versa. Further, it should be noted that "a" or "one" does not exclude a plurality in the present document.

List of reference numerals

100 connector

102 skin portion

104 hole

106 patch

108 edge region

112 outer rivet

114 inner rivet

200 patch

202 patch

204 step

206 rivet

208 rivet

210 step

212 layer

214 surface

216 portion

F loading

FN load per rivet