REINFORCING ELEMENT FOR A STRUCTURAL PROFILE, STRUCTURAL ARRANGEMENT, AIRCRAFT OR SPACECRAFT, AND METHOD FOR PRODUCING A STRUCTURAL ARRANGEMENT

Abstract

A reinforcing element for a structural profile, in particular for a round, oval or elliptical structural tube, includes a composite structure, which has a hollow-cylindrical, helically wound mesh of fiber strands which form an inner shell surface configured to receive the structural profile, wherein the fiber strands are respectively embedded in a matrix material, which has an electroactive polymer which can be stretched along a longitudinal extent of the fiber strands by application of an electrical voltage, such that the composite structure can be expanded by application of the electrical voltage to introduce the structural profile into the composite structure and can be shrunk by switching off the electrical voltage to fix the structural profile on the shell surface in the composite structure.

Claims

1. A reinforcing element for a structural profile, comprising: a composite structure, which has a hollow-cylindrical, helically wound mesh of fiber strands which form an inner shell surface configured to receive the structural profile, wherein the fiber strands are respectively embedded in a matrix material, which has an electroactive polymer which can be stretched along a longitudinal extent of the fiber strands by application of an electrical voltage such that the composite structure can be expanded by application of the electrical voltage in order to introduce the structural profile into the composite structure and can be shrunk by switching off the electrical voltage in order to fix the structural profile on the shell surface in the composite structure.

2. The reinforcing element as claimed in claim 1, wherein the fiber strands respectively together with the matrix material form material strips which are wound helically around the shell surface.

3. A structural arrangement, comprising: a structural profile; and a reinforcing element as claimed in claim 1 which locally surrounds the structural profile, wherein the composite structure is shrunk from an unshrunk state for the application of a tensile stress and is thereby connected to the structural profile with a force fit.

4. The structural arrangement as claimed in claim 3, wherein the structural profile comprises a round, oval or elliptical structural tube.

5. The structural arrangement as claimed in claim 3, wherein the structural profile has two longitudinal portions, wherein the reinforcing element surrounds two mutually opposite ends of the respective longitudinal portions and thus connects the two longitudinal portions to each other.

6. The structural arrangement as claimed in claim 3, wherein the reinforcing element is configured and arranged to stiffen the structural profile.

7. The structural arrangement as claimed in claim 6, wherein the reinforcing element is configured and arranged to provide local bending stiffening.

8. The structural arrangement as claimed in claim 6, wherein the reinforcing element is configured and arranged to introduce axial loads into the structural profile.

9. The structural arrangement as claimed in claim 3, wherein the reinforcing element has a receptacle which is coupled to the composite structure and is configured to transmit axial loads to the composite structure.

10. The structural arrangement as claimed in claim 3, wherein the composite structure is configured such that the mesh of fiber strands axially lengthens and radially contracts during axial tensile loading such that the force fit to the structural profile is automatically reinforced.

11. An aircraft or spacecraft with a structural arrangement as claimed in claim 3.

12. The aircraft or spacecraft as claimed in claim 11, wherein the structural profile is configured as a structural tube which is connected to a primary structure of the aircraft or spacecraft and is configured to connect at least one component to the primary structure.

13. The aircraft or spacecraft as claimed in claim 12, wherein the structural tube is arranged axially on a fuselage structure of the aircraft or spacecraft.

14. The aircraft or spacecraft as claimed in claim 12, wherein at least one of: the at least one component is connected to the structural tube via the reinforcing element, or the structural tube is connected to the primary structure via the reinforcing element.

15. The aircraft or spacecraft as claimed in claim 12, wherein the composite structure is configured for dimensionally stable transmission of conventional flight loads by the force fit, applied with the shrinking of the composite structure, to the structural tube.

16. The aircraft or spacecraft as claimed in claim 11, wherein the composite structure is configured for shape-changing transmission of axial overloads, to the structural profile by axial lengthening and radial contraction.

17. A method for producing a structural arrangement as claimed in claim 3, comprising: arranging the shrunk reinforcing element in the unshrunk state on a structural profile by application of an electrical voltage in such a manner that the inner shell surface locally surrounds the structural profile; performing tolerance compensation by displacing the reinforcing element along the structural profile into a final position; and switching off the electrical voltage to fasten the inner shell surface to the structural profile by shrinking the composite structure.

18. The method as claimed in claim 17, wherein the reinforcing element is configured to connect a component to the structural profile, wherein performing the tolerance compensation comprises coupling the component to the reinforcing element and finally positioning the component in its installation position such that the component is connected to the structural profile by shrinking the composite structure of the reinforcing element in the installation position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be explained in more detail below with reference to the exemplary embodiments indicated in the schematic figures. In the figures:

[0037] FIGS. 1A and 1B show a schematic view of a reinforcing element according to one embodiment of the invention with (1A) and without (1B) electrical voltage applied;

[0038] FIG. 2 shows a top view of the reinforcing element from FIGS. 1A and 1B which is attached to a structural profile;

[0039] FIGS. 3A, 3B, 4A, 4B, 5A and 5B show longitudinal and cross-sectional views of the reinforcing element and structural profile according to FIG. 2 during different installation steps;

[0040] FIG. 6 shows a longitudinal sectional view of a structural arrangement according to one embodiment of the invention;

[0041] FIG. 7 shows a cross-sectional view of the structural arrangement according to FIG. 6;

[0042] FIG. 8 shows a top view of the structural arrangement according to FIGS. 6 and 7;

[0043] FIG. 9 shows a top view of a structural arrangement according to a further embodiment of the invention;

[0044] FIG. 10 shows a top view of a structural arrangement according to yet another embodiment of the invention;

[0045] FIG. 11 shows a top view of an aircraft or spacecraft; and

[0046] FIG. 12 shows a schematic flow diagram of a method for producing a structural arrangement according to one embodiment of the invention.

[0047] The appended figures are intended to impart further understanding of the embodiments of the invention. They illustrate embodiments and serve in conjunction with the description to explain principles and concepts of the invention. Other embodiments and many of the stated advantages arise in relation to the drawings. The elements of the drawings are not necessarily shown true-to-scale in relation to one another.

[0048] Elements, features and components which are identical, have the same function and act in the same manner are provided in each case with the same reference numbers in the figures of the drawing, unless indicated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] FIGS. 1A and 1B show a schematic view of a reinforcing element 1 according to one embodiment of the invention with (FIG. 1A) and without (FIG. 1B) electrical voltage U applied. FIGS. 2 to 5 show the installation of the reinforcing element 1 on a structural profile 7.

[0050] The reinforcing element 1 is hollow-cylindrical and is provided for reinforcing the structural profile 7, for which purpose it is pushed thereon. The reinforcing element 1 is formed with a composite structure 2. The composite structure 2 contains a hollow-cylindrical, helically wound mesh 3 of fiber strands 4 which are respectively embedded in a matrix material 6. The composite structure 2 thus forms an inner shell surface 5 which is designed for receiving the structural profile 7.

[0051] In the embodiment illustrated, the fiber strands 4 are in each case formed together with the matrix material 6 as material strips which are wound helically around the shell surface 5. Each fiber strand 4 can be embedded individually in the matrix material 6. In this way, a multiplicity of composite threads are provided, wherein the mesh is designed as a mesh, which can be seen from the outside here, of such composite threads. Alternatively, a plurality of fiber strands can also be jointly embedded in a respective material strip of matrix material 6.

[0052] The matrix material 6 here comprises an electroactive polymer which is stretchable by application of an electrical voltage U along a longitudinal extent of the fiber strands 4, i.e., of the material strips. The matrix material 6 is designed in such a manner that the composite structure 2 can be expanded by application of the electrical voltage U in order to introduce the structural profile 7 into the composite structure 2 (at FIG. 1B) and can be shrunk by switching off of the electrical voltage U (FIG. 1A) in order to fix the structural profile 7 on the shell surface 5 in the composite structure 2 by applying a circumferential tensile force during the shrinkage.

[0053] FIGS. 3A to 5B show an exemplary installation sequence to illustrate these functional principles. As can be gathered from FIGS. 3A to 5B in this respect, the structural profile 7 is, for example, a round tube. Of course, other profile cross sections are possible in further embodiments. Furthermore, it can be gathered from these figures that the structural profile 7 can have, for example, two longitudinal portions 7a which are connected to one another via the reinforcing element 1. However, it goes without saying that the reinforcing element 1 is also attachable to a single-part structural tube.

[0054] In FIGS. 3A and 3B, a voltage is applied to the matrix material 6 and, owing to this actuation of the electroactive polymer, the composite structure 2 is in the extended (expanded) state in which the structural profile 7 can be pushed between the shell surface 5. In this case, the two longitudinal portions 7a are pushed for this purpose from one side in each case, and therefore the reinforcing element 1 surrounds two opposite ends of the respective longitudinal portions 7a.

[0055] In the unshrunk state illustrated here, the reinforcing element 1 is applied with predetermined play to the structural profile 7 such that it surrounds the structural profile 7 and is displaceable in the axial direction. A spacing or a clearance fit is correspondingly provided at least in sections between the inner shell surface 5 of the composite structure 2 and an outer surface of the structural profile 7, this ensuring simple displaceability. The concentric arrangement illustrated here with a comparatively large intermediate space between the structural profile 7 and the adjustment element 1 should be understood as being purely illustrative. A play can in actual fact also be provided to be comparatively small. In particular, it can be a clearance fit which, however, also permits simple displaceability of the reinforcing element along the structural profile 7.

[0056] In FIGS. 4A and 4B, this operation is finished and the two longitudinal portions 7a lie against each other inside the shell surface 5. In FIGS. 5A and 5B, the applied electrical voltage U is now switched off, which leads to shrinkage of the composite structure 2 (cf. arrows). The components 1, 7 can be configured here in such a manner that this generates a peripheral tensile force and a superficial pressure around the entire structural profile 7 (as symbolized by the arrows indicated at the inner shell surface 5).

[0057] The uniform pressure on the structural profile 7 leads on the one hand to a force fit between the reinforcing element 1 and structural profile 7 such that the reinforcing element 1 is fastened to the structural profile 7 by shrinkage and forms a structural arrangement 10 therewith. In addition, the peripherally applied pressure increases the resistance of the structural profile 7 to bending. At the same time, a connecting fit between the two longitudinal portions 7a of the structural profile 7 is created.

[0058] A structural arrangement 10 of this type can be used, for example, for an aircraft or spacecraft to support X loads, i.e., loads acting in the flight direction. A structural profile 7 can be formed in a different manner depending on the structure of such an aircraft or spacecraft. Of course, this can be a metal profile, but it would also be conceivable to provide a fiber composite profile.

[0059] The embodiment illustrated is a hollow profile cross section. The structural profile is accordingly a tube. Profile cross sections of this type advantageously have high resistance to bending, which is advantageous in particular for a targeted load support. In further embodiments, however, a solid structural profile 7 would also be conceivable.

[0060] The structural profile 7 is locally surrounded by the reinforcing element 1, as is described with respect to the figures. The composite structure 2 of the reinforcing element 1 is shrunk for the application of a tensile stress. In this way, a force fit is produced between the reinforcing element 1 and the structural profile 7 and a local peripheral pressure is applied to the structural profile 7.

[0061] In the embodiment illustrated, the reinforcing element 1 is designed and arranged for local bending stiffening of the structural profile 7. The structural arrangement 10 correspondingly has an increased resistance to bending in the region of the reinforcing element 1 as a result of the applied pressure.

[0062] FIG. 6 shows a longitudinal sectional view of a structural arrangement 10 according to a further embodiment.

[0063] In addition to the bending stiffening effect, the reinforcing element 1 is also designed here for the introduction of axial loads into the structural profile 7. For this purpose, the reinforcing element 1 has a receptacle 11 which is coupled to the composite structure 2 and is designed for transmitting axial loads, which are symbolized here by an arrow Fx, to the composite structure 2.

[0064] The receptacle 11 firstly comprises a clamp 8 which engages around the composite structure 2 in the region of a longitudinal side end of the composite structure 2. The clamp 8 is preferably an uninterrupted sleeve-like clamp 8. In further embodiments, however, it would also be conceivable to provide an interrupted clamp 8 upon which, in particular, a prestress acts.

[0065] The clamp 8 is peripherally connected to the composite structure 2. For this purpose, both form-fitting and integrally bonded connections are conceivable.

[0066] For example, the receptacle 11 can be couplable or coupled to the composite structure 2 in an integrally bonded manner via the matrix material 6. For example, the clamp 8 is formed integrated with the reinforcing element 1, it also being possible for shrinkable or expandable materials to be used for the clamp. For this purpose, in the case of a fabric 3 embedded jointly in the matrix material 6, the clamp can already be embedded during production. Otherwise, the clamp 8 can be connected retrospectively to the matrix material.

[0067] The clamp 8 has one or more force introduction elements 9. The embodiment illustrated involves two oppositely arranged articulation points which in each case allow a bearing with at least one rotational degree of freedom. This can involve in particular a bolt bearing. Dual axis bearings or ball joint bearings are, however, also conceivable. In this way, the transmission of torques to the structural profile 7 is avoided and therefore the targeted support of axial loads, symbolized here by an arrow Fx, is ensured via the force introduction element 9.

[0068] If a tensile force Fx is applied to the connecting element 1 via such a force introduction element 9, this is initially transmitted to the structural profile 7 via the shrunk composite structure 2. The reinforcing element 1 is preferably configured in such a manner that the customary operating loads can be transmitted in this way, in particular flight loads in the case of an aircraft or spacecraft. The composite structure 2 is correspondingly configured for dimensionally stable transmission of conventional flight loads by the force fit, which is applied with the shrinkage, to the structural tube.

[0069] However, if excessive loads occur, for example in the event of a crash, the particular functionality of the mesh 3 comes into effect. The composite structure 2 is configured in such a manner that, in the case of excessive axial tensile loading Fx, the mesh 3 of fiber strands 4 axially lengthens and radially contracts such that an additional pressure is applied to the structural profile and the force fit to the structural profile 7 is automatically reinforced. The composite structure 2 is correspondingly configured for shape-changing transmission of axial overloads Fx, in particular crash loads, to the structural profile by axial lengthening and radial contraction.

[0070] For this purpose, for example, the mesh 3 is designed as a biaxial, helical mesh made from material strips, with it being possible for there not to be any fibers or strips in the x direction, which, in particular, represents the flight direction. Such a mesh 3 is able to lengthen in the event of a tensile force and at the same time reduce its diameter or radially contract. A configuration is possible here which allows this mechanism to come into effect at a predetermined tensile force threshold, in particular only in the event of an excessive load.

[0071] The pressure which additionally acts on the structural profile 7 in the case of engagement of an excessive tensile force Fx is illustrated here with further arrows engaging on the inner shell surface 5. In this way, on the one hand, the fastening by a force fit is strengthened and furthermore the local resistance of the structural profile 7 to bending is once again additionally increased. This thus involves a self-helping design and a configuration of the reinforcing element since it is capable of automatically increasing the holding forces and also the stiffening forces under higher loading.

[0072] FIG. 7 shows a cross-sectional view of the structural arrangement 10 according to FIG. 6.

[0073] It can be seen that the clamp 8 here is formed peripherally. The force introduction elements 19 are received at two opposite points in a recess of the clamp 8, for example in a form-fitting manner. In further embodiments, an integral formation of the force introduction elements 9 with the clamp 8 would also be conceivable. In particular, the force introduction elements 9 can also be provided partially embedded in the clamp 8.

[0074] FIG. 8 shows a top view of the structural arrangement 10 according to FIGS. 6 and 7.

[0075] In this view, the peripheral formation of the clamp 8 can be seen once again. Furthermore, the helically wound structure of the fabric 3 of the composite structure 2 is apparent from FIG. 6 and in FIG. 1.

[0076] FIG. 9 shows a top view of a structural arrangement 10 according to a further embodiment.

[0077] The structural profile 7 is designed here as a structural tube connected to a primary structure 12 of an aircraft or spacecraft. The structural tube is designed for connecting a component 13 to the primary structure 12 to support it in flight direction X.

[0078] The primary structure 12 is illustrated here merely schematically and has, purely by way of example, a plurality of ribs 15 and a skin 16 of a fuselage 21 of an aircraft or spacecraft 20. The structural tube runs in flight direction X and is arranged axially on the fuselage 21. The structural tube is connected here in each case to the ribs 15, for example by means of tube clamps 17.

[0079] The structural tube together with a reinforcing element 1 forms a structural arrangement 10 as is described essentially with respect to FIGS. 6 to 8. A Samer rod 14 is coupled at one end to at least one force introduction element 9 of the reinforcing element 1 and is coupled at its other end to the component 13 via a force transmission element 19. In this way, the component 13 is connected to the structural tube via the reinforcing element 1 and thus provides an axial support in the X direction for the component 13.

[0080] Such a component 13 can be, for example, a cabin element which is supported in this manner in flight direction X. For example, a galley, an on-board toilet or another cabin monument can be provided as the component 13.

[0081] Particularly simple installation of components 13 of this type can be realized particularly advantageously in this way. A method for producing a structural arrangement 10 of this type can be gathered from FIG. 12 in the form of a flow diagram. The method M comprises, under M1, arranging an unshrunk reinforcing element 1 on the structural profile 7 with application of an electrical voltage U in such a manner that the inner shell surface 5 locally surrounds the structural profile 7. The method M comprises, under M2, furthermore performing tolerance compensation by displacing the reinforcing element 1 along the structural profile 7 into a final position. The method M comprises, under M3, furthermore switching off the electrical voltage U in order to fasten the inner shell surface 5 to the structural profile 7 by shrinking the composite structure 2.

[0082] In order to connect the component 13 to the structural profile 7, the performing of the tolerance compensation comprises coupling the component 13 to the reinforcing element 1 and finally positioning the component 13 in its installation position. For this purpose, the reinforcing element can be axially freely displaced. The component 13 can subsequently be connected to the structural profile 7 by shrinking the composite structure 2 of the reinforcing element 1 in the installation position. Advantageously, in this way, no additional tolerance-compensating measures, such as floating bearings or the like, are necessary.

[0083] FIG. 10 shows a top view of a structural arrangement 10 according to yet another embodiment.

[0084] In this embodiment, a reinforcing element 1 is likewise provided, wherein the latter is provided here for connecting the structural tube to the primary structure 12. Instead of the articulated force introduction elements 9, sockets 18 which are fastened to the ribs 15 and are fastened with the clamp 8 are provided here. In the unshrunk state, the structural tube pushed into the reinforcing elements 1 can be axially freely displaced therein.

[0085] The method for producing the structural arrangement 10 runs here substantially identically to that described with respect to FIG. 9, with the difference that the structural profile is freely movable relative to the reinforcing element for tolerance compensation. Tolerances, in particular manufacturing tolerances of the primary structure 12, can therefore be compensated for here by the reinforcing element 1. After final positioning, the structural tube can then subsequently be fastened by switching off the electrical voltage U. For example, axial manufacturing tolerances of an aircraft fuselage can therefore be easily compensated for without additional measures.

[0086] Of course, this type of connection of the structural tube can be combined with the connection of a component 13 according to FIG. 9. For this purpose, an additional reinforcing element 1 can be provided or optionally also a reinforcing element 1, which is present in any case for the connection to the primary structure 12, can be provided with additional force introduction elements.

[0087] FIG. 11 shows a top view of an aircraft or spacecraft 20.

[0088] The aircraft or spacecraft 20 has a fuselage 21 which has the primary structure 12 described with respect to FIGS. 9 and 10. The structural profile 7 is indicated merely schematically by dashed lines to illustrate the axial profile, the structural profile being connected to the primary structure 12. The connection to the primary structure 12 can be designed in particular according to FIG. 10. The structural profile 7 is provided for supporting cabin elements, such as galleys, on-board toilets or other cabin monuments, is provided in the form of components 13 in the axial direction X and is designed as a structural tube reinforced by the reinforcing element 1.

[0089] In the preceding detailed description, various features for improving the stringency of the illustration have been combined in one or more examples. However, it should be clear here that the above description is merely illustrative, and does not have a restricted nature in any way. It serves to cover all the alternatives, modifications and equivalents of the various features and exemplary embodiments. Many other examples will be clear immediately and directly to a person skilled in the art on the basis of their specialist knowledge in view of the above description.

[0090] The exemplary embodiments have been selected and described in order to be able to present the principles underlying the invention and their application possibilities in practice as well as possible. As a result, specialist personnel can modify and use the invention and its various exemplary embodiments in an optimum way with respect to the intended purpose of use. In the claims and the description, the terms including and having are used as neutral terms for the corresponding term comprising.

[0091] 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.

LIST OF REFERENCE SIGNS

[0092] 1 Reinforcing element [0093] 2 Composite structure [0094] 3 Mesh [0095] 4 Fiber strand [0096] 5 Inner shell surface [0097] 6 Matrix material [0098] 7 Structural profile [0099] 7a Longitudinal portion [0100] 8 Clamp [0101] 9 Force introduction element [0102] 10 Structural arrangement [0103] 11 Receptacle [0104] 12 Primary structure [0105] 13 Component [0106] 14 Samer rod [0107] 15 Rib [0108] 16 Skin [0109] 17 Tube clamp [0110] 18 Socket [0111] 19 Force transmission element [0112] 20 Aircraft or spacecraft [0113] 21 Fuselage [0114] U Electrical voltage [0115] X Aircraft X direction [0116] M Method [0117] M1-M3 Method steps