Abstract:
The invention relates to a structural component for an aircraft or spacecraft, comprising a component core extended across a component area, a first and second cover layer, which are formed on two opposite bounding surfaces of the component core and extend across the component area, a plurality of braces, which are distributed across the component area and connect the first and second cover layers to each other through the component core, and a stiffening belt, which extends between the cover layers along a stiffening line that extends substantially parallel to the component area.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to PCT/EP2010/056860 filed May 19, 2010, which claims the benefit of and priority to U.S. Provisional Application No. 61/181,045, filed May 26, 2009 and German Patent Application No. 10 2009 026 458.2, filed May 25, 2009, the entire disclosures of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a structural component for an aircraft or spacecraft and a method for producing a structural component of this type. The invention further relates to an aircraft or spacecraft comprising a structural component of this type. 
         [0003]    Although applicable to any structural components, the present invention and the problem on which it is based will be explained in greater detail with reference to fuselage shells of commercial aircraft. 
         [0004]    EP 1134069 discloses the production of structural components for an aircraft in a double-shell construction using sandwich components which comprise a foam core. Structural components of this type, in particular when produced using fibre-reinforced plastics materials, offer a great weight advantage compared with structural components made from conventional materials such as aluminium. However, production and handling of structural components of this type in a double-shell construction for assembly to form larger structures, for example of an aircraft or spacecraft, is extremely time and cost intensive. Furthermore, damage sustained during assembly is expensive to repair. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the present invention is therefore to enable the reliable and economical application of double-shell structural components. 
         [0006]    The idea on which the present invention is based consists in reinforcing a structural component which is extended in a planar manner over a component area and which comprises two face sheets connected via a core enclosed between them, in that a reinforcing belt is provided between the face sheets, which belt stretching along a reinforcement path between the face sheets, which path extends substantially parallel to the component area. Since the reinforcing belt, like the core, extends in the interior between the face sheets, it can be formed by methods used in the production of the sandwich, which offers great cost advantages compared to an assembly using conventional reinforcing elements such as stringers and formers. Since the reinforcing belt extends inside the face sheets, it is furthermore protected from damage between the face sheets. 
         [0007]    According to a preferred development, the component core comprises a foam material. This enables cost-effective production of the structural component, as the struts in the foam material are formed as provisionally supporting auxiliary material and connected to the face sheets, wherein the foam material can simply remain inside the component core in a cost-saving manner due to its lightness. Alternatively, the foam can be removed in order to achieve an even lower weight. 
         [0008]    According to a preferred development, the struts each comprise a fibre bundle infiltrated with resin. This enables the structural component to be produced economically, as the struts are, for example, formed in the foam material using a simple stitching method and infiltrated with resin in the resulting through holes. 
         [0009]    According to a preferred development, the reinforcing belt is formed by a region of increased density of the struts in the component core. This enables extremely low production costs as the reinforcing belt can be produced using methods and devices already used for the insertion of the struts. Furthermore, the struts can be inserted almost without geometric limitations on the course of the reinforcing belt. 
         [0010]    According to an alternative preferred development, the reinforcing belt is formed by an insert which extends over the reinforcement path in the component core. In this way, a high level of stability can be achieved. Furthermore, the stable interconnection of face sheets which abut one another along the insert is made possible. Preferably, the insert comprises a tubular fibre braid which surrounds an insert core because this structure is particularly stable and has a low dead weight. 
         [0011]    According to a preferred development, at least one strut penetrates the component core and the insert core. In this way, the insert is particularly rigidly connected. The strut preferably extends diagonally to the component area as it is thus easy to insert from the outside. 
         [0012]    According to a preferred development, the component area comprises a curvature in at least one direction in space, wherein the reinforcing belt extends helically diagonally to the direction of the curvature. The component can thus advantageously be reinforced against torsional vibrations along the curvature axis. 
         [0013]    According to a preferred development, a first and a second reinforcing belt are provided which extend intersecting one another at an angle. The component can thus advantageously be reinforced against deformation in the case of loading in different directions. 
         [0014]    According to a preferred development, the reinforcing belt extends in a first and a third portion substantially in a corresponding direction and comprises a split into two annularly connected branches in a portion arranged between the first and third portions. In this way, the reinforcing belt can be guided around planar cut-outs in the structural component, for example window cut-outs, without substantial loss of stability. 
         [0015]    In the following, the invention is described in greater detail on the basis of embodiments with reference to the accompanying figures of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In the figures: 
           [0017]      FIG. 1  shows a sectional view of an exemplary structural component according to an embodiment; 
           [0018]      FIG. 2  shows a side view of a fuselage barrel section of an aircraft comprising a structural component according to an embodiment; 
           [0019]      FIG. 3  shows a schematic sectional view of a structural component comprising a lining, according to an embodiment; 
           [0020]      FIG. 4  shows a representation of a production method according to an embodiment for the structural component shown in  FIG. 3 ; 
           [0021]      FIG. 5  shows a schematic sectional view of a structural component comprising an insert, according to a further embodiment; 
           [0022]      FIG. 6  shows a schematic sectional view of a structural component comprising a window opening, according to an embodiment; and 
           [0023]      FIG. 7  shows a schematic sectional view of a structural component comprising a door opening, according to an embodiment. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0024]    In the figures, like reference numerals denote like or functionally identical components, unless indicated otherwise. 
         [0025]      FIG. 1  shows a sectional view of a structural component  102  comprising a component core  408  which is made from a foam material and is extended in a planar manner over a component area of the sandwich component, on the opposite, substantially parallel sides of which component core a first  401  and second  402  facing made of a fibre material are formed. The component area extends parallel to the facings  401 ,  402  and is perpendicular to the plane of projection of  FIG. 1 . Between the first  401  and second  402  facings, struts  403  made from fibre bundles extend through the component core  408 , the ends  406  of which struts rest against the facings  401 ,  402 . Facings  401 ,  402  and struts  403  are filled with a common polymer matrix. 
         [0026]    The struts  403  are distributed over the whole component area of the structural component  102  with a substantially constant minimum areal density. In addition, the areal density of the struts  403  is increased beyond the minimum areal density along an elongate region of a reinforcing belt  106 , which extends along a reinforcement path  104  between the face sheets, which path  104  extends substantially parallel to the component area. The structural component  102  thus has an increased rigidity in the region of the reinforcing belt  106 . 
         [0027]      FIG. 2  shows a side view of a fuselage barrel section  206  of an aircraft. The fuselage barrel geometry is divided in a longitudinal direction, wherein the upper half of the fuselage barrel is formed by a structural component  102  having a double-shell construction, as shown in  FIG. 1 . This structural component  102  is produced in one piece, for example using a mould having an inner mould surface, in order to ensure the outer tolerances. The lower half  202  of the fuselage barrel can, for example, be produced in a similar way using metal or another material. 
         [0028]    In the structural component  102 , reinforcing belts  106 ,  106 ′,  106 ″,  106 ′″ formed by the increased areal density of struts  403  extend in a longitudinal direction  203  of the aircraft and in directions which extend oblique to the longitudinal direction of the aircraft and to the curvature direction  204  of the substantially cylindrically curved structural component  102  and which wind helically diagonally around the fuselage barrel section  206 . In this case, the diagonally extending reinforcing belts  106 ,  106 ′ intersect at an angle α of approximately 90°. 
         [0029]    In the fuselage barrel section  206  a row of window openings  208  is formed, which openings are surrounded by annular reinforcements  200 . The annular reinforcements  200  are included in the course of the reinforcing belts  106 ,  106 ′,  106 ″,  106 ′″ in that, for example, a first portion  211  of the reinforcing belt  106  extends in the direction of the diagonal reinforcement path  104 , until it abuts an annular reinforcement  200  around a window opening  208 . In a second portion  212  in the region of the window opening, the annular reinforcement  200  assumes the function of the reinforcing belt which here divides into two annularly connected branches. On the opposite side of the annular reinforcement  200 , these branches meet and the course of the reinforcing belt continues in a third portion  213  in the direction of the reinforcement path  104 . 
         [0030]    The reinforcement design shown is only an example and can be fully adjusted to local loading (load introductions, cut-outs). Geometric variations in the foam (variations in thickness, curvatures, ramps) can further be included in the reinforcement design. 
         [0031]      FIG. 3  shows a schematic sectional view of a further structural component  102  which is assembled from a first component half  311  comprising a foam core  408  and face sheets  401 ,  402 , and a second component half  312  comprising a foam core  408 ′ and face sheets  401 ,  402 , along a joint line which extends in the centre of  FIG. 3  perpendicular to the plane of projection. Along the joint line an insert  302 ,  300  is inserted between the face sheets  401 ,  401 ′ and  402 ,  402 ′, which insert comprises an insert core  302  made from foam material, and a sheathing  300  made from tubular fibre braid. The sheathing  300  is, for example, infiltrated with resin, together with the face sheets  401 ,  401 ′,  402 ,  402 ′ and the struts  403 . The insert functions as a reinforcing belt  106  by means of the sheathing. 
         [0032]      FIG. 4  schematically shows a possible production method for the structural component of  FIG. 3 , wherein part of the respective core  408 ,  408 ′ is removed from the two component halves  311 ,  312  and the insert  300 ,  302  is inserted in lieu thereof. The integration of the insert can be further reinforced via the insertion of additional struts  500 ,  502  which penetrate the face sheets  401 ,  401 ′,  402 ,  402 ′ and the sheathing  300  of the insert  300 ,  302 . 
         [0033]      FIG. 6  shows a schematic sectional view of a structural component  102  comprising an opening for a window  600 , wherein a reinforcement belt consisting of three portions  211 ,  212 ,  213  as described with reference to  FIG. 2  extends over the window opening. The annular insert  200  is, for example, constructed in the same way as the insert  300 ,  302  in  FIG. 3 .  FIG. 7  shows a schematic sectional view of a structural component  102  comprising an opening for a door  704 . As additional reinforcement, supports  700  and a further facing  702  are fitted on the inner face of the aircraft fuselage. 
         [0034]    Although the present invention has presently been described on the basis of preferred embodiments, it is not restricted thereto, but can be modified in many different ways. 
         [0035]    For example, further structural components of an aircraft such as aerofoils or tail units can be constructed in the manner described. 
         [0036]    In the following preferred embodiments of the structural component, the fuselage cell, the aircraft or spacecraft and the method are explained. 
         [0000]    1. A structural component for an aircraft or spacecraft, comprising:
 
a component core extended over a component area;
 
a first and second face sheet which are formed extending over the component area on two opposite boundary faces of the component core;
 
a plurality of struts distributed over the component area, which struts connect the is first and second face sheets to one another via the component core; and
 
a reinforcing belt which extends along a reinforcement path between the face sheets, said path extending substantially parallel to the component area.
 
2. The structural component according to embodiment 1, wherein the component core comprises a foam material.
 
3. The structural component according to embodiment 1, wherein the struts each comprise a fibre bundle infiltrated with resin.
 
4. The structural component according to embodiment 1, wherein the reinforcing belt is formed by means of a region of increased density of the struts in the component core.
 
5. The structural component according to embodiment 1, wherein the reinforcing belt is formed by means of an insert in the component core, which insert extends over the reinforcement path.
 
6. The structural component according to embodiment 5, wherein the insert comprises a tubular fibre braid which surrounds an insert core.
 
7. The structural component according to embodiment 5, wherein at least one strut, in particular a strut extending diagonally, penetrates at least one face sheet and the insert.
 
8. The structural component according embodiment 1, wherein the component area comprises a curvature in at least a curvature direction, the reinforcing belt extending helically diagonally in the curvature direction.
 
9. The structural component according to embodiment 1 wherein a first and a second reinforcing belt which extend intersecting one another at an angle (a) are provided.
 
10. The structural component according to embodiment, wherein the reinforcing belt extends in a first and a third portion substantially in the direction of the reinforcement path and comprises a split into two annularly connected branches in a second portion arranged between the first and third portions.
 
11. A fuselage shell for an aircraft or spacecraft comprising a structural component according to any one of claims  1  to  10 .
 
12. An aircraft or spacecraft comprising a fuselage shell according to embodiment 11 or a structural component according to embodiment 1.
 
13. A method for producing a structural component for an aircraft or spacecraft, comprising the following steps:
 
preparation of a component core which is expanded over a component area and comprises a foam material;
 
arrangement of a first and second face sheet on two opposite boundary faces of the component core, which face sheets extend over the component area;
 
formation of a plurality of struts distributed over the component area, which struts connect the first and second face sheet to one another via the component core; and
 
insertion of a reinforcing belt which extends along a reinforcement path between the face sheets, which reinforcement path extends substantially parallel to the component area.
 
14. The method according to embodiment 13, wherein the insertion of the reinforcing belt results from the formation of the struts in an increased areal density.
 
15. The method according to embodiment 13 wherein a step of at least partial removal of the foam material is provided.
 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           102  structural component 
           104  reinforcement path 
           106  reinforcing belt 
           200  ring structure 
           202  lower shell 
           203  longitudinal direction of aircraft 
           204  direction of curvature 
           206  fuselage barrel section 
           211 - 213  belt portions 
           300  tube braid 
           302  insert core 
           311 ,  312  component halves 
           401 ,  402  facing 
           403  strut 
           406  anchor 
           408  component core 
           500 ,  502  additional struts 
           600  window 
           500  vertical strut 
           502  diagonal strut 
           700  support 
           702  further facing