Structural element

Abstract

A structural element, in particular for an aircraft, such as an airplane, contains a laminate having a plurality of layers made of a fiber composite plastics material with carbon fibers, a lightning protection layer and optionally an electrically insulating dielectric protection layer. The laminate contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers.

Claims

1. A structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, and wherein a topmost layer of the laminate is formed by the hybrid layer.

2. The structural element according to claim 1, wherein the absorption fibers are steel fibers.

3. The structural element according to claim 1, wherein the absorption fibers are stainless steel fibers.

4. The structural element according to claim 1, wherein the hybrid layer is formed of one of a unidirectional layer, a braid, an interlaid scrim or a woven fabric made of carbon fibers and absorption fibers.

5. The structural element according to claim 1, wherein the lightning protection layer contains a metallic foil.

6. The structural element according to claim 1, wherein the electrically insulating dielectric protection layer is arranged above the lightning protection layer.

7. The structural element according to claim 1, wherein all layers of the laminate, not including the lightning protection layer, are hybrid layers which comprise a carbon fiber-absorption fiber composite.

8. The structural element according to claim 1, wherein every n-th layer of the laminate is a hybrid layer, n being a natural whole number.

9. The structural element of claim 1, wherein the structural element comprises a fuselage element of an aircraft.

10. The aircraft of claim 1, wherein the lightning protection layer is arranged between the electrically insulating dielectric protection layer and the laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers and at least one hybrid layer.

11. The structural element of claim 10, wherein at least one hybrid layer is directly adjacent to the lightning protection layer.

12. A structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, and wherein a bottommost layer of the laminate is formed by the hybrid layer.

13. A structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, wherein the insulating, dielectric layer contains allotropes of carbon, the fraction of the allotropes of carbon being below the percolation threshold.

14. The structural element according to claim 13, wherein the allotropes of carbon contain at least one of carbon short fibers or CNTs.

15. A structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, wherein the electrically insulating dielectric protection layer is arranged above the lightning protection layer wherein the metallic foil is made of copper or a copper base alloy.

16. An aircraft comprising: structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, and wherein a topmost layer of the laminate is formed by the hybrid layer.

17. The aircraft of claim 16, wherein the structural element comprises a fuselage element of the aircraft.

18. The structural element of claim 16, wherein the lightning protection layer is arranged between the electrically insulating dielectric protection layer and the laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers and at least one hybrid layer.

19. The aircraft of claim 18, wherein at least one hybrid layer is directly adjacent to the lightning protection layer.

20. An aircraft comprising: a structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, and wherein a bottommost layer of the laminate is formed by the hybrid layer.

21. An aircraft comprising: a structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, and wherein the insulating, dielectric layer contains allotropes of carbon, the fraction of the allotropes of carbon being below the percolation threshold.

22. An aircraft comprising: a structural element comprising: a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, and a lightning protection layer, wherein the laminate additionally contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers, further comprising an electrically insulating dielectric protection layer, wherein the electrically insulating dielectric protection layer is arranged above the lightning protection layer wherein the metallic foil is made of copper or a copper base alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some embodiments of the invention will be described in further detail in the following, with reference to a FIGURE. The FIGURE schematically shows the layer structure of a structural element according to some embodiments of the invention (the structure of which can be both planar and curved).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) A structural element according to some embodiments of the invention is a fuselage element of an airplane, which is basically constructed from a laminate made of layers of carbon fiber composite plastics material 3. The matrix material is an epoxy resin. The top and bottom layer of the laminate comprises a hybrid layer 4, which comprises a carbon fiber-absorption fiber composite. The absorption fibers in this particular example are steel or stainless steel fibers. An expanded copper foil is laminated on the top hybrid layer 4 as a lightning protection layer 2. An electrically insulating dielectric protection layer 1 is applied on top of this. If the airplane is struck by lightning during the flight, and the structural element is struck, an explosion of the lightning protection layer results. However, the 3 to 5 times greater elongation at break of the stainless steel fibers in comparison to the carbon fibers of the laminate produces a better absorption of the energy of the shockwaves caused by an explosion of the lightning protection layer or the epoxy resin matrix. This leads to the whole CFRP structure being less badly damaged by the lightning strike. Although the carbon fibers break down, this does not lead to the whole CFRP structure being catastrophically mechanically damaged. Furthermore, the electrical and thermal conductivity of the stainless steel fibers in the hybrid layers 4 achieves considerably reduced thermal damage. The repair costs of the damaged structural element according to the invention would be significantly lower than if it were constructed conventionally. The described effects furthermore allow the copper foil, which evenly distributes the strike current and the heat introduced by the plasma channel, to be designed to be thinner than is conventional. A portion of the weight is therefore saved which would be conventionally necessary for the lightning protection.

(3) According to a variant of the embodiment (not explicitly shown), in addition to the top and bottom hybrid layer 4, every fourth layer of the CFRP structure is also replaced by a hybrid layer.

(4) According to a further variant, the insulating, dielectric protection layer 1 contains allotropes of carbon, the fraction of the carbon short fibers being below the percolation threshold. According to the embodiment, this further reduces the thermal and mechanical damage of the structural element according to the invention.

(5) It can be advantageous to provide the whole fuselage with structural elements of the invention, or also regions that are particularly at risk from lightning strike, e.g., in the region of the fuselage or of the airfoil.

(6) The invention relates to a structural element, in particular for an aircraft, such as an airplane, which contains a laminate comprising a plurality of layers made of a fiber composite plastics material comprising carbon fibers, a lightning protection layer and optionally an electrically insulating dielectric protection layer. According to some embodiments of the invention, the laminate contains at least one hybrid layer, which comprises a carbon fiber-absorption fiber composite, the elongation at break of the absorption fiber being greater than the elongation at break of the carbon fibers.

(7) 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.