DE102006048641B4 - Connection structure for an aircraft or spacecraft and method of manufacturing the same - Google Patents

Abstract

Connection structure (20; 63) for an aircraft or spacecraft, comprising a structural component (3; 50) and a stringers (11, 12, 13; 51 ... 54), which are connected via attachment regions (8, 9, 10, 34, 35; 61a ... 61d, 64a ... 64d) is connected to the structural component (3; 50), at least one of the attachment regions (8,9,10,14,35; 61a ... 61d, 64a. ..64d) a high-impact-resistant material (5; 55) for a local increase in the energy absorption capacity of the at least one connection region (8, 9, 10; 61a ... 61d) is introduced between the structural component and the stringer, wherein the stringer (11, 12, 13; 51 ... 54) has a foot section (15; 57) for a support on the structural component (3; 50), and wherein the high-impact material (5; 55) is arranged in the region of the foot section (15; 57).

Description

The present invention relates to a connection structure for an aerospace vehicle and to a method of manufacturing such a connection structure for an aerospace vehicle.

Although applicable to any connection structures, the present invention and its underlying problem with respect to a stiffened fuselage shell of an aircraft are explained in more detail.

Hull shells and stringer are increasingly made of fiber composites, especially carbon fiber reinforced plastic (CFRP). Fuselage shells and stringer thereby have a structure of several layers of fiber fabric, which are connected to each other by means of a cured resin matrix, in particular epoxy resin. Typically, as stringers, T-stringers having a leg to which they are connected to the hull shell and a land portion extending substantially perpendicular to the hull shell are used to stiffen the hull shell. The foot of the T-stringer is connected to the fuselage shell by means of the resin matrix.

Under normal operating conditions of an aircraft, tensile, compressive and shear stresses act in the hull shell parallel to the hull shell plane. In addition, a substantial portion of the hull shell with acting perpendicular to the plane of the fuselage shell forces resulting from the pressure difference between the cabin and the environment, applied. In addition, the hull shell occasionally exposed impacts, so short-term and intense force. An example of such impact is a rubber patch of a tattered tire landing on the hull shell at high speed.

Such impacts in such fuselage shells made of fiber composite material are often trigger for a damage initiation in the fuselage shell. This results in a power flow, starting from the impact along the fuselage shell over the T-Stringer foot into the web section of the T-stringer. Especially in the lateral attachment areas of the T-Stringerfußendes and the foot of the T-stringer, which is located directly below the web portion of the T-stringer, it comes for a short time to very high voltage spikes in the resin matrix. The result is a brittle fracture of the resin matrix in these attachment regions. As a result, the T-Stringer detaches itself from the fuselage shell and it comes to the catastrophic collapse of this.

The German patent application DE 38 36 442 A1 describes a material for impact-stressed components. This is provided for example on leading edges of wings or tail on aircraft.

The publication US 4 331 723 A describes a fiber composite structure in which a spar is attached by means of resin to an associated skin.

The object of the present invention is to provide an improved connection structure between a structural component and a stringer, wherein, in particular, detachment of the stringer from the structural component under the influence of impacts is to be prevented.

According to the invention, this object is achieved by a connection structure having the features of patent claim 1 or by a method for producing a connection structure having the features of patent claim 11.

Accordingly, a connection structure for an aerospace vehicle having a structural member and a stringer which is connected to the structural member via attachment areas is provided. In at least one of the connection areas, a high-impact-resistant material for a local increase in the energy absorption capacity of the at least one connection region is introduced.

Furthermore, a method for producing such a connection structure for an aircraft or spacecraft is provided. The method steps are briefly described below. First, a structural component and a stringer, which can be connected to one another via connection regions, are provided. Then, a high impact material is introduced into at least one of the attachment regions for a local increase in the energy absorption capacity of the at least one attachment region. An assembly of the structural component and the stringer on the connection areas can be done before or after the introduction of the high impact material.

The idea underlying the present invention is that the stress peaks resulting from the impact are damped in the connection regions between the hull shell and stringer by a high-impact-resistant material. Thus, it no longer comes to failure of the resin matrix or the connection between the structural component and stringer. Accordingly, by means of the invention, a release of the stringer from the hull shell, for example as a result of an impact and thus the catastrophic collapse of the hull shell, can be advantageously prevented. Thus, will created a more stable and thus safer connection structure.

In the subclaims there are advantageous embodiments and improvements of the invention.

In this patent application, a "structural component" is to be understood as meaning, in particular, flat components, for example fuselage shells, wing shells or rudder shells.

High-impact materials in the present application are materials which have a significantly higher energy absorption capacity than epoxy resin. By "energy acceptability" is meant the absorption of mechanical work without failure of the high impact material.

In this application, "joining" is to be understood as meaning any joining in the sense of the DIN standard "joining", whereby in particular laying, nesting, riveting, screwing, sewing and gluing are possible.

According to a preferred embodiment of the invention, the high-impact material is formed as a thermoplastic material. By "thermoplastic material" is meant in this application a material which consists of 100% thermoplastic, so for example of polyethylene and / or polyamide. By "thermoplastic material" in this application, but also mixtures (these are also referred to as modified matrix) of resin, in particular epoxy resin, plastic fibers, and thermoplastics to understand. The thermoplastic content of the thermoplastics in the thermoplastic material is below in percentages by weight, ie based on the total weight of the thermoplastic material, consisting of plastic fibers and / or resin and / or thermoplastic specified.

According to a further preferred development of the invention, the structural component has a fiber composite material and / or the stringer has a fiber composite material. Fiber composites are to be preferred because of their low weight with high strength in the aerospace industry. Alternatively, however, it can also be provided that, for example, the structural component is made of metal, in particular of an aluminum alloy, and only the stringer has a fiber composite material. Of course, only the stringer can be made of metal, in particular an aluminum alloy, and the structural component can have a fiber composite material. The fiber composites of the stringer and the structural member may have the same or different compositions. These measures allow an optimization of the connection structure in terms of strength and weight.

According to a preferred development of the invention, the thermoplastic material has a higher thermoplastic content than the respective fiber composite materials. This results in a higher energy absorption capacity in certain connection areas.

In the present case, a "connection region" is understood to mean a region in which the stringer is connected to the structural component. Multiple areas arise when one area has the high impact material and another area does not have this high impact material.

According to a further preferred embodiment of the invention, the thermoplastic content of the thermoplastic material is between 5% and 100%, in particular between 50% and 80%, furthermore preferably between 60% and 70%. Such a thermoplastic component is optimal in terms of energy absorption capability, while still a sufficient strength, so maximum tensile, compressive and shear stress in the connection areas, which comprise the thermoplastic material is guaranteed.

In a further preferred embodiment of the invention, the stringer has a foot portion in which it rests on the skin shell, and / or a web portion, which is aligned substantially perpendicular to the skin shell. On the one hand, such stringers can be fastened well to sheet-like structural components and, on the other hand, stiffen the structural component sufficiently.

The thermoplastic material is preferably arranged in the region of the foot section, in particular in the region of the region of the foot section pointing away from the web section, and / or in the region of the web section. By "in the area" are here preferably a few centimeters, in particular a distance of 0 cm to 5 cm from the web portion or the ends of the foot section to understand. Upon impact with the hull shell, there is a flow of force from the plane of the fuselage shell first into the end portions of the stringer's foot sections, through the foot sections, and into the bridge section. The power flow changes its direction several times, whereby at the points of the direction changes to increased loads comes. Therefore, it is expedient to provide the stringer with thermoplastic material in these areas in order to provide increased energy absorption in these areas.

According to a further preferred embodiment of the invention, the thermoplastic material is arranged between the foot portion and the structural component. Such a local introduction of the thermoplastic material can be easily realized in terms of manufacturing technology.

According to a preferred embodiment, the thermoplastic material is formed as a sewing thread, in particular as a thermoplastic thread. A "thermoplastic thread" in this application is understood to mean a thread which consists of 100% thermoplastic. Such sewing is rationally feasible production technology and allows a targeted introduction of the thermoplastic material in the connection structure. Experimentally, it has been determined that the thermoplastic threads do not dissolve under the action of pressure or heat on the connection structure, in particular during the curing of the fiber composite connection structure.

Preferably, the sewing thread forms a seam which takes place in the longitudinal direction of the stringer and sewn the stringer base to the structural component. This results in a simple manufacturability with favorable power flow.

In a preferred embodiment, the sewing thread connects the foot portion, in particular in its end region and / or in the region of the web portion, to the structural component. This arrangement is even more favorable in terms of force flow resulting from impact.

In a further preferred embodiment of the invention, the thermoplastic material is formed as a textile fabric, fiber scrims and / or crosslinked thermoplastic granules. Particularly in the case of connection structures made of fiber composite materials, thermoplastic materials formed in this way can be inserted very easily into the fiber structure of the structural component or of the stringer and thus processed efficiently. Furthermore, a good connection between the thermoplastic material and the fiber layers of the structural component and / or the stringer is achieved.

Preferably, the stringer is designed as a T, Z, C, L or Ω stringer. Depending on the load case, it is therefore possible to provide an optimal form of the stringer for a specific application.

According to a further preferred development of the invention, the structural component is designed as a skin shell, in particular a hull shell of the aircraft.

In a further preferred embodiment of the invention, the first and / or the second fiber composite CFRP, in particular CFRP prepreg material, on or based on semi-finished textile products, such as fabrics, laid o. Ä .. CFRP has a high strength at low weight , In addition, CFRP prepreg material is easy to process.

According to a further preferred development of the invention fastening means are provided, in particular screws or rivets, for connecting the stringer with the structural component.

In addition or as an alternative to fastening the stringer to the structural component by means of the resin matrix and / or the high-impact-resistant material, fastening means can be provided which can receive further energy from the impact.

According to a further preferred embodiment of the method according to the invention, the arrangement consisting of structural component, stringer and connection areas is cured by means of pressure and / or heat to form the connection structure. Accordingly, the structural component, the stringer and the attachment areas are assembled in the dry or wet state and then cured.

According to a further preferred improvement of the method according to the invention, a resin matrix is introduced into the structural component and the stringer. In the case where the structural component and / or the stringer are provided as dry semi-finished fiber products, a resin matrix must be introduced in the course of the method for producing the connecting structure.

By "dry" fibers are not yet understood in this application impregnated with resin fibers. In contrast, "wet" fibers already impregnated in resin but not yet cured fibers meant. Furthermore, "semi-finished fiber products" are to be understood as meaning, in particular, fiber fabrics, in particular unidirectional fiber fabrics, woven or fiber mats.

According to a preferred embodiment of the method according to the invention, the structural component or the stringer is provided as a semi-finished fiber product, prepreg material, at least partially cured fiber composite material. There are consequently a large number of possible combinations with regard to the materials which are provided for forming the structural component and / or the stringer.

For example, dry fiber webs can be combined with already cured web sections of stringers, the Stringer feet are provided, for example, prepreg material.

According to a further preferred embodiment of the method according to the invention, this has a hand lay, prepreg, transfer molding and / or vacuum infusion method. In the event that the structural component and / or the stringer are provided dry, it may be advantageous in terms of manufacturing technology to introduce the resin matrix into the fiber layer by means of vacuum infusion methods.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the accompanying figures of the drawing.

From the figures shows:

1 a process state in the manufacture of a connection structure according to an embodiment of the present invention, wherein thermoplastic material is arranged over a large area between a skin shell and a stringer;

2 the connection structure, which according to the method of 1 is made;

3 a process state in the production of a connection structure according to another embodiment of the present invention, wherein the thermoplastic material is introduced as a sewing thread; and

4 the connection structure, which according to the method of 3 is made.

In all figures of the drawing the same or functionally identical elements - unless otherwise stated - have been provided with the same reference numerals.

1 shows a laminating device 1 which a contour 2 having. The contour 2 is shaping for a skin shell 3 , For example, a hull shell of an aircraft, wherein the skin shell is preferably composed of not yet cured layers of CFRP material.

An applicator 4 wears a thermoplastic material 5 on the skin shell 3 on. The thermoplastic material 5 in this embodiment, by weight percent, preferably has a composition of 40% polyethylene and 60% epoxy resin.

The application of the thermoplastic material 5 takes place along several, preferably three parallel, connection areas 8th . 9 and 10 , The thermoplastic material 5 is applied here as a powder. Equally, however, it would also be possible to apply fiber layers of thermoplastic material and / or to overlap them with the fibers of the skin shell. Subsequently, T-stringer 11 . 12 and 13 by means of a depositing device 14 on the skin shell 3 on the connection areas 8th . 9 . 10 stored.

The T-Stringer 11 . 12 and 13 are also made of CFRP material and are only partially cured. The T-Stringer 11 . 12 and 13 be with her foot 16 on the skin shell 3 discontinued, in which case a web section 17 perpendicular to the foot 16 and thus to the skin shell 3 extends.

After fitting the skin shell 3 with the T-stringers 11 . 12 . 13 , this arrangement becomes under pressure and heat to the connection structure 20 , as in 2 shown, cured.

Out 2 it can be seen that the stringer 13 essentially of two L-shaped layers CFK 21 and 22 is trained. The layers 21 . 22 subdivide again into many layers of fiber fabric (not shown here). A gusset 23 , typically a strand of fibers, fills one of the layers 21 . 22 unfilled space on.

The layers 21 . 22 are each on one leg 24 . 25 cohesively connected to each other and form the web section 17 out.

The two other thighs 28 . 29 extend in opposite directions and together form the foot 16 out. The thigh 28 . 29 each have toes at their ends 30 . 31 on which to the skin shell 3 flattened out.

Furthermore, in 2 the connection areas 8th . 9 . 10 . 34 . 35 shown. The connection areas 8th . 9 . 10 each have the thermoplastic material 5 on. The connection areas 8th and 10 are each at the end of the thighs 28 . 29 under the toes 30 . 31 arranged. The connection area 9 is below the gusset 23 educated.

Further, the foot is 16 the stringer 13 about the connection areas 34 . 35 with the skin shell 3 connected. In these areas, the connection takes place by means of gluing the resin matrix in the layers 21 . 22 with the resin matrix in the skin layer 3 ,

For example, an impact works in the point 36 on the skin shell 3 That's how it turns out 36 resulting force flow over the connection areas 8th . 9 . 10 . 34 . 35 in the stringer 13 initiated. In the connection areas 8th . 10 the power flow changes its direction from the skin shell 3 out in the stringer 13 into, and in the connection area 9 the diversion of the Power flow from the foot 16 in the bridge section 17 into it. So at the points where there is a significant change in direction of the power flow, namely in the connection areas 8th . 9 and 10 , According to the invention, the thermoplastic material is preferably provided. It is by means of the invention thus an energy absorption or damping in these connection areas 8th . 9 . 10 achieved.

The connection areas 34 . 35 have a lower energy absorption capacity than the attachment areas 8th . 9 . 10 , but preferably have a higher tensile strength.

3 also shows the laminator 1 and the contour 2 , The contour 2 is thereby shaping a skin shell 50 as a dry fiber fabric on the contour 2 rests. T-stringer 51 . 52 . 53 . 54 are on the skin shell 50 arranged. The T-Stringer 51 ... 54 are also present as a dry, especially interwoven, fiber fabric.

Subsequently, the T-stringer 51 ... 54 by means of a sewing device 56 that is a thermoplastic material 55 provides with the skin shell 50 sutured. This is the foot 57 the stringer 51 in the longitudinal direction and adjacent to the web section 58 or the tiptoe 59 . 60 with the skin shell 50 sutured. As sewing threads 61a ... 61d Here, a thermoplastic threads are used, which preferably consist of 100% polyethylene.

Subsequently, the arrangement consisting of the skin shell 50 and the T-stringers 51 ... 54 preferably impregnated in a vacuum infusion process with a matrix, in particular an epoxy resin matrix. In a further process step, the resin-impregnated arrangement by heat and pressure, for example in an autoclave, to the in 4 illustrated connection structure 63 hardened.

Components that are not described further correspond to those from 2 , The sewing threads 61a and 61d fix the tiptoes 59 respectively. 60 on the skin shell 50 and thus form a first and second connection area. The sewing threads 61b and 61c extend right and left side of the web section 58 For example, run crosswise through the foot 57 and the skin shell 50 through and thus form a third and fourth connection area. The first to fourth connection areas serve to absorb energy, for example as a result of an impact.

There are also connection areas 64a ... 64d provided, with the foot 57 by means of resin with the skin shell 50 is glued. These connection areas 64a ... 64d preferably have one opposite the connection areas 61a ... 61d lower energy absorption capacity, but have a higher maximum tensile strength (N / mm ² ), so the voltage, after exceeding it to a failure in these connection areas 64a ... 64d comes.

A detachment of the stringer 13 . 58 from the skin shells 3 . 50 as a result of an impact 36 can thus be effectively prevented.

The invention is not limited to the special connection structure shown in the figures or to the method for producing such a connection structure.

The individual sequence of individual method steps of the method according to the invention can be changed in a variety of ways. The design of the individual process steps themselves can also be modified. For example, in the in 3 instead of a dry stringer, a wet stringer, or even a stringer with a cured land portion and wet foot.

Furthermore, the geometry of the skin shell and the stringer can be modified in many ways. Instead of T-stringers, Ω stringer can also be used, which are connected to a skin shell in the area of their foot sections. By "stringer" is meant any type of stiffening element, including, for example, a bulkhead.

It is also conceivable that only one connection region between the stringer and the structural component is provided, wherein this entire connection region is provided with thermoplastic material.

LIST OF REFERENCE NUMBERS

1

laminating

2

contour

3

skin shell

4

applicator

5

Thermoplastic Material

8th

connecting region

9

connecting region

10

connecting region

11

Stringer

12

Stringer

13

Stringer

14

laying device

15

foot section

17

web section

20

connecting structure

21

location

22

location

23

gore

24

leg

25

leg

28

leg

29

leg

30

toe

31

toe

34

connecting region

35

connecting region

36

A hit

50

skin shell

51

T-stringer

52

T-stringer

53

T-stringer

54

T-stringer

55

Thermoplastic Material

56

sewing equipment

57

foot section

58

web section

59

toe

60

toe

61a ... 61d

sewing threads

63

connecting structure

64a ... 64d

connecting regions

Claims (23)

Connection structure ( 20 ; 63 ) for an aircraft or spacecraft, with a structural component ( 3 ; 50 ) and a stringer ( 11 . 12 . 13 ; 51 ... 54 ), which via connection areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ) with the structural component ( 3 ; 50 ), wherein in at least one of the attachment areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ) a high impact material ( 5 ; 55 ) for a local increase in the energy absorption capacity of the at least one connection region ( 8th . 9 . 10 ; 61a ... 61d ) is introduced between the structural component and stringer, wherein the stringer ( 11 . 12 . 13 ; 51 ... 54 ) a foot section ( 15 ; 57 ) for a support on the structural component ( 3 ; 50 ), and wherein the high impact material ( 5 ; 55 ) in the area of the foot section ( 15 ; 57 ) is arranged. Connecting structure according to claim 1, characterized in that the high-impact-resistant material ( 5 ; 55 ) is formed as a thermoplastic material. Connecting structure according to claim 1 or 2, characterized in that the structural component ( 3 ; 50 ) a fiber composite material and / or the stringer ( 11 . 12 . 13 ; 51 ... 54 ) comprises a fiber composite material. Connecting structure according to claim 3, characterized in that the thermoplastic material has a higher thermoplastic content than the respective fiber composites. Connecting structure according to one of claims 2 to 4, characterized in that the thermoplastic content of the thermoplastic material is between 5% and 100%. Connecting structure according to claim 5, characterized in that the thermoplastic content of the thermoplastic material is between 50% and 80%. Connecting structure according to one of the preceding claims, characterized in that the stringer ( 11 . 12 . 13 ; 51 ... 54 ) a bridge section ( 17 ; 58 ) which is substantially perpendicular to the structural component ( 3 ; 50 ) is aligned. Connecting structure according to claim 7, characterized in that the high impact material ( 5 ; 55 ) in the end region pointing away from the web section ( 30 . 31 ; 59 . 60 ) of the foot section ( 15 ; 57 ) and / or in which at the web section ( 17 ; 58 ) adjacent area of the foot section ( 15 ; 57 ) is arranged. Connecting structure according to one of the preceding claims, characterized in that the high-impact-resistant material ( 5 ; 55 ) as sewing thread ( 61a ... 61d ) is trained. Connecting structure according to claim 9, characterized in that the sewing thread ( 61a ... 61d ) is formed as a thermoplastic thread. Connecting structure according to claim 9 or 10, characterized in that the sewing thread ( 61a ... 61d ) forms a seam, which in the longitudinal direction of the stringer ( 51 ... 54 ) and the foot section ( 57 ) of the stringer ( 51 ... 54 ) with the structural component ( 50 Sewn. Connecting structure according to one of claims 2 to 8, characterized in that the thermoplastic material is formed as a textile fabric, fiber structure and / or crosslinked thermoplastic grains. Method for producing a connection structure ( 20 ; 63 ) for an aircraft or spacecraft, comprising the following steps: providing a structural component ( 3 ; 50 ) and a stringer ( 11 . 12 . 13 ; 51 ... 54 ), which are connected via connection areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ) are connectable to each other; Introducing a highly impact-resistant material into at least one of the attachment areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ) between the structural component and the stringer for a local increase in the energy absorption capacity of the at least one connection region ( 8th . 9 . 10 ; 61a ... 61d ), the high impact material ( 5 ; 55 ) between a foot section ( 16 ; 57 ) of the stringer ( 11 . 12 . 13 ; 51 ... 54 ) and the structural component ( 3 ; 50 ) is arranged; and assembling the structural component ( 3 ; 50 ) and the stringer ( 11 . 12 . 13 ; 51 ... 54 ) via the connection areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ). A method according to claim 13, characterized in that the high impact material ( 5 ; 55 ) is formed as a thermoplastic material. A method according to claim 13 or 14, characterized in that the arrangement consisting of the structural component ( 3 ; 50 ), the stringer ( 11 . 12 . 13 ; 51 ... 54 ) and the connection areas ( 8th . 9 . 10 . 34 . 35 ; 61a ... 61d . 64a ... 64d ) by means of pressure and / or heat to form the connection structure ( 20 ; 63 ) is cured. Method according to one of claims 13 to 15, characterized in that a resin matrix in the structural component ( 3 ; 50 ) and the stringer ( 11 . 12 . 13 ; 51 ... 54 ) is introduced. A method according to claim 16, characterized in that as the resin matrix, an epoxy resin in the structural component ( 3 ; 50 ) and the stringer ( 11 . 12 . 13 ; 51 ... 54 ) is introduced. Method according to one of the preceding claims 13 to 17, characterized in that the structural component ( 3 ; 50 ) and / or the stringer ( 11 . 12 . 13 ; 51 ... 54 ) is provided as semi-finished fiber product, prepreg material, at least partially cured fiber composite material. Method according to one of claims 14 to 18, characterized in that the thermoplastic content of the thermoplastic material is selected by weight percent between 5% and 100%. A method according to claim 19, characterized in that the thermoplastic content of the thermoplastic material is selected by weight percent between 50% and 80%. Method according to one of claims 13 to 20, characterized in that the stringer ( 11 . 12 . 13 ; 51 ... 54 ) with the structural component ( 3 ; 50 ) by means of a sewing thread ( 61a ... 61d ) from the high impact resistant material ( 5 ; 55 ) is sewn. A method according to claim 21, characterized in that as sewing thread ( 61a ... 61d ) a thermoplastic thread is used. Method according to one of claims 13 to 22, characterized in that the high-impact material ( 5 ; 55 ) as a textile fabric, fiber fabric, powder and / or aerosol is introduced.

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