DE102022127923A1 - Wing body and method for producing and repairing a wing body - Google Patents

Abstract

The invention relates to a wing body for a flying object with a wing box which has a first flow surface section of a flow surface facing the surrounding air flow, and with a wing leading edge arranged in the flow direction in front of the wing box, which has a second flow surface section of the flow surface, so that the wing box and wing leading edge form an aerodynamically flowable flow profile, characterized in that at least the second flow surface section of the wing leading edge is formed at least partially from a flat, metallic shape memory alloy, wherein the metallic shape memory alloy is designed such that it returns to its original shape by tempering if it has previously been deformed by the application of force.

Description

The invention relates to a wing body for a flying object with a wing box which has a first flow surface section of a flow surface facing the surrounding air flow, and with a wing leading edge arranged in the flow direction in front of the wing box, which has a second flow surface section of the flow surface, so that the wing box and wing leading edge form an aerodynamically flowable flow profile.

The invention also relates to a method for repairing such a wing body and a method for its production.

In the sense of the present invention, the term "wing body" refers to those elements of a flying object that are arranged in a protruding manner from the fuselage of the flying object and that, when the flying object is used as intended, are exposed to air flow from surrounding layers, thereby causing aerodynamic forces. In particular, the wings (airfoils) and the tail units (horizontal stabilizer, vertical stabilizer) are wing bodies in the sense of the present invention.

The profile surfaces of the wing bodies of flying objects, such as the wings of commercial aircraft, initially have laminar boundary layers when exposed to airflow, but in today's commercial aircraft these quickly turn into turbulent boundary layers. Such a turbulent boundary layer has a significantly higher frictional resistance than a laminar boundary layer. The instability of the boundary layer, which leads to the transition, is promoted by shape deviations, such as gaps and steps in the contour of the profile surface.

Permissible values for these shape deviations are, for example, 0.5 mm for steps against the flow direction and 0.1 mm for steps in the direction of flow.

If such shape deviations are avoided, particularly in the front area of the aerodynamic functional surface, this leads to a later change in the flow from a laminar boundary layer to a turbulent boundary layer and thus to an expanded area of laminar flow around the profile. This in turn leads to a reduction in drag and direct fuel savings or an increased range of the aircraft.

Apart from the benefits of improved laminarity, significantly larger deviations (e.g. several millimeters) from the specified aerodynamic contour at the wing leading edge can lead to a loss of lift and endanger the flight safety of the aircraft. Such large deviations can be caused by the impact of large hailstones or other foreign objects. In this case, a repair of the leading edge is essential to ensure sufficient flight safety.

Basically, such wing bodies, especially the wings of commercial aircraft, consist of a wing box with two diametrically opposed wing shells that are held inside the wing box with the help of spars and ribs and also serve to maintain the required profile contour of the wing. The wing box often also forms an internal fuel tank. The wing leading edge is attached in the direction of flow in front of the wing box, which connects the outer flow surface of the wing box with the outer flow surface of the wing leading edge to form a flow profile and also contains the high-lift systems in the slats provided on some aircraft (slats or Kruger flaps). The wing leading edge is the exposed area of the wing body that is first exposed to the surrounding air masses and thus makes an important contribution to maintaining the laminar boundary layer flow.

It is known that in conventional commercial aircraft the wing or wing body is made from an aluminum material, whereby the structure of the wing leading edge is often merged with the structure of the wing box. Such a riveted connection is characterized by the fact that a corresponding bolt or a connecting element is guided through the surface of the respective structure, whereby a corresponding closure is then provided on the outer edges. For this purpose, the leading wing edge and one of the wing shells of the wing box are arranged to overlap and then connected with several riveted connections, whereby such a riveted connection represents an additional disturbance on the flow surface and thus has a negative effect on the boundary layer. The rivet head on the flow surface promotes the transition from the laminar to a turbulent boundary layer, so that such a riveted connection in the leading edge area should generally be avoided.

Another way to reduce the total weight of a flying object, especially a conventional commercial aircraft, and thus save fuel, is to make parts of the fuselage and the wing body of the flying object out of a fiber composite material, for example a CFRP (carbon fiber plastics) or GFRP (glass fiber plastics) material. Structurally critical components are also increasingly being made from these materials in order to save weight.

Although fiber composites have a very favorable weight-to-stability ratio, components made from fiber composites are susceptible to external forces acting on the component perpendicular to the fiber plane of the fiber composites. A wing leading edge made from fiber composites must therefore generally be protected by a protective layer to prevent damage to the wing leading edge made from fiber composites when external forces are applied. Otherwise, external influences such as hail or bird strikes would lead to erosion, which can impair the stability and integrity of the wing leading edge.

However, it has been shown that such an outer protective layer on the leading edge of the wing must also be replaced regularly so that the leading edge of the wing continues to promote the maintenance of a laminar boundary layer flow. This is because the deformation caused by an external force on the leading edge of the wing usually leads to a very early transition from a laminar boundary layer flow to a turbulent boundary layer flow, which must be avoided for the reasons mentioned above.

Repairing such a deformed flow surface is usually quite complex, as the outer protective layer must be removed from the wing body and a new protective layer applied. This can result in considerable maintenance intervals, which negates the advantage of laminar boundary layer flow for the purpose of saving fuel.

It is therefore an object of the present invention to provide an improved wing body for flying objects in which the outer flow surface can be easily and quickly repaired.

The object is achieved according to the invention with the wing body according to claim 1. Advantageous embodiments of the invention can then be found in the corresponding subclaims.

According to claim 1, a wing body for flying objects is proposed, wherein the wing body has a wing box and a wing leading edge arranged in front of the wing box in the flow direction. Together, the wing box and the wing leading edge form an aerodynamically flowable flow profile, wherein the wing box also includes the wing trailing edge. The wing body has an outer flow surface around which the outer air masses flow. For this purpose, the wing box has a first flow surface section which interacts with the second flow surface section of the wing leading edge to form a common flow surface.

According to the invention, it is provided that at least the second flow surface section of the wing leading edge is formed at least partially from a flat, metallic shape memory alloy, wherein the metallic shape memory alloy is designed such that it returns to its original shape by tempering if it has previously been deformed by the action of force.

Preferably, the entire area of the nose of the wing's leading edge is provided with such a metallic shape memory alloy, as this is the exposed area that is most frequently affected by deformations and damage. If deformations such as dents, dents and the like are found in the area of the wing's leading edge after use of the flying object, the original shape can be restored without deformations by tempering the shape memory alloy to a temperature that is in most cases material-dependent. To do this, the wing's leading edge or the wing body is tempered by a heating device external or integrated in the wing body until the shape memory alloy returns to its original shape, thereby eliminating the deformations in the wing's leading edge.

It was recognized that deformations such as hail damage or bird strikes, which often occur on wing leading edges, can be eliminated using a shape memory alloy by tempering the shape memory alloy to the appropriate temperature.

This makes it possible to repair such deformation-related damage to the leading edge of the wing by simply tempering it, so that the leading edge of the wing or its protective layer does not need to be replaced. The wing body can therefore be returned to its original state in a very short time, which means that a laminar boundary layer flow can be achieved over the entire operation of the aircraft.

Another advantage is that the material used for a wing body is fiber composite materials can be used, as the leading edge of the wing can now be protected using the shape memory alloy as a protective layer. The wing body, but in particular the leading edge of the wing, is manufactured or formed from a fiber composite material, with the flat, metallic shape memory alloy as a protective layer protecting the underlying structure made of the fiber composite material.

It can be provided that an elastic layer (for example made of an elastomer) is arranged between the flat, metallic shape memory alloy and the fiber composite structure of the wing leading edge, so that severe deformations of the outer protective layer made of the shape memory alloy do not damage the underlying fiber composite structure of the wing leading edge.

This makes it possible to use fiber composite materials for wing bodies, with easy repair of the wing leading edge possible due to the shape memory alloy.

According to one embodiment, the metallic shape memory alloy comprises or consists of a nickel-titanium alloy.

According to one embodiment, it is provided that the metallic shape memory alloy has a first martensitic material state in which the metallic shape memory alloy is in its original shape, and a second austenitic material state that can be changed by tempering and in which the metallic shape memory alloy returns to its original shape if it has been deformed in the first material state by the action of external force.

For the purpose of repair, the shape memory alloy is tempered in such a way that the shape memory alloy changes from the first martensitic material state (also called phase or martensite) to the second austenitic material state (also called phase or austenite), so that the shape memory alloy returns to its original shape and all damage caused by deformations such as dents or dings is eliminated.

The original shape of the shape memory alloy is the shape in which the outer flow surface formed by the shape memory alloy does not show any deformations and in principle promotes a laminar boundary layer flow.

According to one embodiment, it is provided that the wing body has a tempering device which cooperates with the part of the flow surface which is formed from the flat, metallic shape memory alloy for tempering the shape memory alloy.

Such a tempering device can, for example, be integrated into the structure of the wing's leading edge. If the wing's leading edge is made from a fiber composite material that has electrically conductive fibers, these can be energized in the area of the shape memory alloy so that the area of the wing's leading edge with the shape memory alloy heats up due to the electrical resistance. It is also conceivable, however, that the tempering device has corresponding fluid channels that are integrated into the structure of the wing's leading edge so that a tempered fluid can flow through the fluid channels in order to temper the shape memory alloy to the desired temperature. Such a tempered fluid can, for example, be the bleed air of the engines.

It is also conceivable that the shape memory alloy is heated directly or indirectly by means of induction and/or infrared radiation.

According to one embodiment, it is provided that the tempering device is part of a de-icing system for de-icing the wing body.

The object is also achieved according to the invention with the method for repairing such a wing body according to claim 6, wherein the part of the flow surface which is formed from the flat, metallic shape memory alloy is tempered to a temperature at which the shape memory alloy returns to its original shape if it was previously deformed by the action of force.

First, a wing body according to one of claims 1 to 5 is provided for the process. Such a wing body has deformations in the area of its flat, metallic shape memory alloy caused by external forces, which often promote a transition to turbulent boundary layer flow. The wing body is then tempered, at least in the area of the shape memory alloy, to a corresponding temperature at which the shape memory alloy returns to its original shape. After the shape memory alloy has cooled, these deformations are removed and the wing body is repaired.

• - Bereitstellen eines Flügelkörpers mit einem Flügelkasten sowie einer in Strömungsrichtung vor dem Flügelkasten angeordnete Flügelvorderkante,
• - Herstellen zumindest eines Teils der Strömungsoberfläche des bereitgestellten Flügelkörpers aus einer metallischen Formgedächtnislegierung in einer ursprünglichen Form unterhalb einer ersten Temperatur,
• - Temperieren des hergestellten Teils der Strömungsoberfläche oberhalb einer zweiten Temperatur,
• - Abkühlen des hergestellten Teils der Strömungsoberfläche, nach dem die zweite Temperatur überschritten wurde, unter die erste Temperatur,
• - Anordnen des hergestellten Teils der Strömungsoberfläche an den Flügelkörper derart, dass dieser Bestandteil der Strömungsoberfläche des Flügelkastens wird.

The object is also achieved according to the invention with the method for producing such a wing body according to claim 7. The method comprises the following steps:

• - Providing a wing body with a wing box and a wing leading edge arranged in front of the wing box in the direction of flow,
• - producing at least part of the flow surface of the provided wing body from a metallic shape memory alloy in an original shape below a first temperature,
• - Tempering the produced part of the flow surface above a second temperature,
• - cooling the manufactured part of the flow surface after the second temperature has been exceeded to below the first temperature,
• - Arranging the manufactured part of the flow surface on the wing body in such a way that it becomes part of the flow surface of the wing box.

The production of at least part of the flow surface from the shape memory alloy can be carried out using a closed tool mold. First, a semi-finished product made of a shape memory alloy is provided, the semi-finished product is then placed in the tool mold and the tool mold is then closed. The tool mold has the desired shape in which the shape memory alloy should be in its original form.

The shape memory alloy, which has been brought into its original shape in this way, can now be removed from the tool mold or remain in the tool mold when the subsequent tempering process begins. The shape memory alloy is tempered to the required temperature and then cooled very quickly so that the shape memory alloy has learned or "trained" its original shape.

If the shape memory alloy is later tempered above this certain temperature, which may depend on the material, it returns to the original shape it acquired during the manufacturing process.

The shape memory alloy produced in this way can now be applied as a protective layer to the desired area of the wing's leading edge and connected to it. The shape memory alloy can be connected to the wing's leading edge by gluing, for example.

According to one embodiment, after cooling, the tempering and cooling process is repeated once or several times.

According to one embodiment, it is provided that the manufactured part of the flow surface forms at least part of the flow surface of the wing leading edge.

According to one embodiment, the first temperature is the beginning of the martensitic material state and the second temperature is the beginning of the austenitic material state.

• 1 schematische Darstellung eines Flügelkörpers im Querschnitt;
• 2 schematische Darstellung der Herstellung der an Formgedächtnislegierung.

The invention is explained by way of example with reference to the accompanying figures. It shows:

• 1 schematic representation of a wing body in cross section;
• 2 Schematic representation of the production of the shape memory alloy.

1 shows schematically in a highly simplified representation the cross section through a wing body 10, which has a wing box 11, which is only partially shown, and a wing leading edge 30 arranged in front of the wing box 20 in the flow direction. The wing box 20 has an internal support structure 21, which can be formed, for example, from a fiber composite material and which gives the wing box 20 its stability and integrity. Half shells 22 can be provided, by which the wing box 20 is limited on two opposite sides (here, the top and bottom). The half shells 22 can also form the first flow surface section 23 of the outer flow surface of the wing body 10.

The wing leading edge 30 which adjoins it also has an internal support structure 31 which can also be made of a fiber composite material. To separate the support structure 31 from the air masses flowing around it, the wing leading edge 30 is given an outer protective layer 32 which forms the second flow surface section 33.

The first flow surface section 23 together with the second flow surface section 33 forms an outer flow surface and thus an outer flow profile, which can transfer lift forces or other forces to the aircraft when the flow profile is flowed against by external air masses.

The outer protective layer 32 of the wing leading edge 30, which forms part of the outer flow surface of the wing body 10, is made according to the invention from a metallic shape memory alloy that has "remembered" the original shape of the protective layer 32. The original shape of the protective layer 32 corresponds to the desired shape of the wing leading edge on the outer flow surface without restrictive deformations or damage.

Advantageously, the original shape of the protective layer 32 is designed to promote a laminar boundary layer flow.

The wing leading edge 30 further comprises a heating device 40, which can be completely contained in the wing leading edge 30 or only certain parts thereof. The heating device 40 is designed to heat the protective layer 32 to a temperature at which the protective layer 32 formed from the metallic shape memory alloy returns to its original shape, so that damage to the protective layer 32 in the form of dents or bulges is removed.

If the heating device 40 is part of the wing body 10, damage to the wing leading edge 30 can also be repaired during an intermediate stop or in connection with simple maintenance measures by tempering the shape memory alloy.

The production of such a protective layer 32 from the shape memory alloy is in 2 indicated schematically. First, a quasi-endless semi-finished product 50 is provided, which represents an elongated sheet wound on a roll made of a metallic shape memory alloy. A plate 51 is then cut from this elongated sheet 50, from which the protective layer 32 is then to be produced.

For this purpose, a mold 60 is provided, which has a lower mold half 61 and an upper mold half 62. The lower mold half 61 has a component cavity into which the plate 51 is pressed with the help of the upper mold half 62. The result is shown in step 2 of the 2 recognizable.

Subsequently, the plate 51 located in the component cavity is tempered between the upper mold half 62 and the lower mold half 61 above the austenite temperature so that the plate 51 is consolidated in the original shape.

The protective layer 32 formed in this way is then removed from the mold 60 and immersed in a cold liquid bath 63 so that the temperature of the protective layer 32 falls below the martensite temperature in a short time. Steps 1 to 3 can then be repeated until a sufficient memory effect of the protective layer 32 has been achieved.

List of reference symbols

10

Wing body

20

Wing box

21

Supporting structure

22

Half shells

23

first flow surface section

30

Wing leading edge

31

Supporting structure

32

Protective layer made of shape memory alloy

33

second flow surface section

40

Heating device

50

Semi-finished product of a shape memory alloy

51

prefabricated plate

60

Forming tool

61

lower mold half

62

upper mold half

63

Liquid bath

Claims (10)

Wing body (10) for a flying object with a wing box (20) which has a first flow surface section (23) of a flow surface facing the surrounding air flow, and with a wing leading edge (30) arranged in the flow direction in front of the wing box (20) and which has a second flow surface section (33) of the flow surface, so that the wing box (20) and the wing leading edge (30) form a flow profile around which flow can occur aerodynamically, characterized in that at least the second flow surface section (33) of the wing leading edge (30) is formed at least partially from a flat, metallic shape memory alloy, the metallic shape memory alloy being designed such that it returns to its original shape through tempering if it has previously been deformed by the application of force. Wing body (10) after Claim 1 , characterized in that the metallic shape memory alloy comprises or consists of a nickel-titanium alloy. Wing body (10) after Claim 1 or 2 , characterized in that the metallic shape memory alloy has a first martensitic material state in which the metallic shape memory alloy is in its original shape, and has a second austenitic material state which can be changed by tempering and in which the metallic shape memory alloy returns to its original shape if it has been deformed in the first material state by the action of external force. Wing body (10) according to one of the preceding claims, characterized in that the wing body (10) has a tempering device which cooperates with the part of the flow surface which is formed from the flat, metallic shape memory alloy for tempering the shape memory alloy. Wing body (10) after Claim 4 , characterized in that the tempering device is part of a de-icing system for de-icing the wing body (10). Method for repairing a wing body (10) according to one of the Claims 1 until 5 , characterized in that the part of the flow surface which is formed from the flat, metallic shape memory alloy is tempered to a temperature at which the shape memory alloy returns to its original shape if it has previously been deformed by the action of force. Method for producing a wing body (10), the method comprising the following steps: - providing a wing body (10) with a wing box (20) and a wing leading edge (30) arranged in front of the wing box (20) in the flow direction, - producing at least part of the flow surface of the provided wing body (10) from a metallic shape memory alloy in an original shape below a first temperature, - tempering the produced part of the flow surface above a second temperature, - cooling the produced part of the flow surface below the first temperature after the second temperature has been exceeded, - arranging the produced part of the flow surface on the wing body (10) in such a way that it becomes part of the flow surface of the wing box (20). Procedure according to Claim 7 , characterized in that after cooling, the process of tempering and cooling is repeated once or several times. Procedure according to Claim 7 or 8th , characterized in that the manufactured part of the flow surface forms at least part of the flow surface of the wing leading edge (30). Method according to one of the Claims 7 until 9 , , characterized in that the first temperature is the beginning of the martensitic material state and the second temperature is the beginning of the austenitic material state.

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