阅读说明：本技术 用于气流控制的飞行器结构 (Aircraft structure for airflow control ) 是由 多特·丹德尔斯 伯恩哈德·施利普夫 克里斯蒂安·哈克 于 2020-02-26 设计创作，主要内容包括：披露了一种用于气流控制的飞行器结构(11),所述飞行器结构包括穿孔面板(13),所述穿孔面板具有指向结构内部(17)的内表面(15)；与周围气流(21)接触的外表面(19)；以及连接所述内表面(15)和所述外表面(19)的多个微孔(23)。减小飞行器结构的重量同时保持所需的疲劳强度的目的得以实现在于：一个或多个长形止裂元件(25)附接至所述穿孔面板(13)的内表面(15),并且所述止裂元件(25)被配置成抑制裂纹在所述穿孔面板(13)内扩张。(An aircraft structure (11) for airflow control is disclosed, comprising a perforated panel (13) having an inner surface (15) directed towards a structure interior (17); an outer surface (19) in contact with an ambient air flow (21); and a plurality of micropores (23) connecting the inner surface (15) and the outer surface (19). The object of reducing the weight of the aircraft structure while maintaining the required fatigue strength is achieved in that: one or more elongated crack stop elements (25) are attached to the inner surface (15) of the perforated panel (13), and the crack stop elements (25) are configured to inhibit crack propagation within the perforated panel (13).)

1. An aircraft structure (11) for airflow control, the aircraft structure comprising

A perforated panel (13) having an inner surface (15) directed towards the structure interior (17); an outer surface (19) in contact with an ambient air flow (21); and a plurality of micropores (23) connecting said inner surface (15) and said outer surface (19),

it is characterized in that the preparation method is characterized in that,

one or more elongated crack stop elements (25) are attached to the inner surface (15) of the perforated panel (13) and

the crack stop element (25) is configured to inhibit crack propagation within the perforated panel (13).

2. The aircraft structure according to claim 1, wherein the crack arresting element (25) extends in a main load direction of the aircraft structure 11.

3. The aircraft structure according to claim 1 or 2, wherein the crack arresting element (25) has a higher fatigue strength than the perforated panel (13).

4. The aircraft structure according to any one of claims 1 to 3, wherein the crack arrest element (25) is formed as a strip of Fibre Reinforced Plastic (FRP) material.

5. The aircraft structure according to any one of claims 1 to 4, wherein the crack arresting elements (25) have a width (w) in the range 1/100 to 1/1, preferably 1/25 to 1/15, most preferably 1/20 of the distance (d) between every two adjacent crack arresting elements (25).

6. The aircraft structure according to any one of claims 1 to 5, wherein the microholes (23) in the perforated panel (13) also extend through the crack arrest element (25).

7. The aircraft structure of any one of claims 1 to 6, further comprising: an inner panel (29) mounted to the perforated panel (13) via a stiffener (31) attached to an inner surface (15) of the perforated panel (13).

8. The aircraft structure of claim 7, wherein at least some of the crack arresting elements (25) are arranged between the inner surface (15) of the perforated panel (13) and at least some of the stiffeners (31).

9. The aircraft structure of claim 7 or 8, wherein at least some of the stiffeners (31) are formed as crack arrest elements (25).

10. The aircraft structure according to claim 9, wherein the stiffener (31) is formed as a crack arrest element (25) by configuring the material of the stiffener (31) for arresting cracks.

11. The aircraft structure according to claim 9 or 10, wherein the stiffener (31) is formed as a crack arrest element (25) by configuring the shape of the stiffener (31) for arresting cracks.

12. The aircraft structure according to claim 11, wherein the stiffener (31) has an increased thickness at least at a head (33) attached to the inner surface (15) of the perforated panel (13).

13. An aircraft (1) comprising a fuselage (3), a wing (5), a vertical tail (7), and a horizontal tail (9), wherein an aircraft structure (11) according to any one of claims 1 to 12 is arranged at the wing (5) and/or the vertical tail (7) and/or the horizontal tail (9).

Technical Field

The present invention relates to an aircraft structure configured for airflow control, preferably for Hybrid Laminar Flow Control (HLFC). Another aspect of the invention relates to an aircraft comprising such an aircraft structure.

Background

The aircraft structure comprises a perforated panel having an inner surface directed towards the interior of the structure; an outer surface in contact with an ambient gas stream; and a plurality of micro-cells distributed on the perforated panel and connecting the inner surface and the outer surface. The perforated panel is preferably formed of a metal material such as titanium.

Such aircraft structures are known to be associated with HLFC systems in which air is drawn or blown through the micro-holes in the perforated panel to favorably influence the ambient airflow along the aircraft structure to increase lift and reduce drag, and therefore reduce fuel consumption. However, the micro-holes required for sucking or blowing air easily induce the generation and expansion of cracks through the perforated panel, and thus reduce the fatigue strength of the perforated panel. Therefore, in order to obtain the required fatigue strength, a higher panel thickness is required, which however increases the weight of the aircraft structure.

Disclosure of Invention

It is therefore an object of the present invention to reduce the weight of an aircraft structure while maintaining the required fatigue strength.

This object is achieved in that: one or more elongated crack stop elements are attached to the inner surface of the perforated panel. Preferably, a plurality of crack stop elements are provided which extend parallel to each other. The crack stop element is preferably bonded to the inner surface of the perforated panel, but may also be bolted or riveted to the inner surface of the perforated panel. The crack arrest element is configured to inhibit a crack from propagating within the perforated panel past the crack arrest element, i.e., from one side of the crack arrest element to the other. Inhibiting crack propagation refers to arresting or at least slowing crack propagation. This may also mean deflecting the crack propagation into an insignificant direction parallel to the crack arrest member.

By means of such a crack arrest element, crack propagation, in particular with respect to a direction transverse to the crack arrest element, can be prevented or at least slowed down, so that the fatigue strength of the perforated panel and thus of the aircraft structure is increased. In other words, the thickness of the perforated panel can be reduced without reducing the fatigue strength of the perforated panel, which in turn leads to a reduction in the weight of the aircraft structure and therefore to a reduction in the fuel consumption of the associated aircraft.

According to a preferred embodiment, the crack arresting elements extend longitudinally in a direction transverse to the flight direction of the associated aircraft. Preferably, the crack arresting elements extend in an angular range of 0 ° to 45 °, further preferably 0 ° to 30 °, most preferably 0 ° to 15 °, with respect to the main load direction, preferably with respect to the spanwise direction. In this way, the crack arrest element also extends transversely, preferably perpendicularly, to the intended direction of crack propagation.

According to another preferred embodiment, the crack arresting element has a fatigue strength which is much higher than the perforated panel, in particular much higher than the relevant adjacent part of the perforated panel, in particular with respect to a load exerted in the longitudinal direction of the crack arresting element. In this way, cracks in the perforated panel that expand towards the crack arrest element will be stopped, deflected into a direction parallel to the crack arrest element, or at least slowed down due to the higher fatigue strength of the crack arrest element.

According to yet another preferred embodiment, the crack stop element is formed as a strip of Fibre Reinforced Plastic (FRP) material. In case the perforated panel is made of a metal material, the local Fiber Metal Laminate (FML) is thus formed by the FRP strip together with the perforated panel in the area of the strip. The volume ratio of the metal and the FRP may be, for example, 1/1 or the like. Such FML is particularly suitable for crack arrest due to its high resistance to crack growth.

According to another preferred embodiment, the crack stop elements have a width perpendicular to the longitudinal extension and along the inner surface of the perforated panel in the range 1/100 to 1/1, preferably 1/25 to 1/15, most preferably 1/20 of the distance between every two adjacent crack stop elements. A lower width of the crack stop element may be advantageous, as less micro-pores are covered by the crack stop element, whereas a larger width may provide a more effective crack stop. Thus, the width is ideally adjusted as required by the particular application.

According to another preferred embodiment, the micro-holes in the perforated panel also extend through the crack stop element. In this way, the micro-holes are not covered by the crack stop elements and air can be sucked and blown through the micro-holes in a uniform manner. This is particularly advantageous in case the crack stop element has a higher width, so that in this case a higher number of micro-holes will be covered. However, owing to simpler production and higher strength, especially in the case of crack stop elements of lower width in which only few micropores are covered, non-perforated crack stop elements may also be preferred.

In another preferred embodiment, the aircraft structure further comprises an inner panel mounted to the perforated panel via a stiffener attached to an inner surface of the perforated panel, for example by gluing. The inner panel and the reinforcement are preferably made of FRP material. The stiffener may be part of the inner panel or may be a separate part attached to the outside of the inner panel, for example by co-curing, moulding or gluing. For example, the stiffener may have a Z-shaped profile mounted to the inner panel and the perforated panel, or may have an omega-shaped profile or a trapezoidal-shaped profile integral with the inner panel or mounted to the inner panel and to the perforated panel. By adding such an inner panel, a double-walled, stiffener-reinforced aircraft structure is formed, which is particularly advantageous for use in an airflow control system, since the outer perforated panel is additionally supported.

It is particularly preferred that at least some of the crack stop elements are arranged between the inner surface of the perforated panel and at least some of the stiffeners. For example, the crack stop elements may be provided at each stiffener, or may be provided only at some of the stiffeners, e.g. at every other stiffener. Additionally, the crack stop element may be attached to the inner surface of the perforated panel at a location between the stiffeners (e.g., intermediate each two adjacent stiffeners). In this way, the stiffener may be used to secure the crack stop element to the perforated panel and no additional bonding or securing needs to be applied to the associated crack stop element.

Additionally or advantageously, it is preferred that at least some of the stiffeners are formed as crack stop elements. In this way, there is no need or need to provide and fix a small number of separate crack stop elements to the perforated panel.

It is particularly preferred that the reinforcement is formed as a crack arrest element by configuring the material of the reinforcement for arresting cracks. In particular, the material of the stiffener is selected such that the stiffener has a fatigue strength that is higher than the perforated panel, in particular higher than the portion of the perforated panel to which the respective stiffener is attached. In this way, crack arrest is provided only by adjusting the material of the corresponding reinforcement to be provided anyway accordingly. Separate crack stop elements can be kept.

Additionally or alternatively, it is preferred that the reinforcement is formed as a crack arrest element by configuring the shape, in particular the profile, of the reinforcement for arresting cracks. In particular, the shape of the stiffener is chosen such that the stiffener has a fatigue strength that is higher than the perforated panel, in particular higher than the portion of the perforated panel to which the respective stiffener is attached. In this way, crack arrest is provided only by correspondingly adjusting the shape of the corresponding reinforcement to be provided anyway. Separate crack stop elements can be kept.

It is particularly preferred that the stiffener has an increased thickness at least at the portion attached to the inner surface of the perforated panel. This increased thickness of the stiffener provides increased fatigue strength for preventing or at least mitigating crack propagation within the perforated panel.

Another aspect of the invention relates to an aircraft. An aircraft includes a fuselage, wings, a vertical tail, and a horizontal tail. The aircraft structure according to any one of the preceding embodiments is arranged at the wing and/or vertical tail and/or horizontal tail of the aircraft. The above-described features and advantages in connection with an aircraft structure apply correspondingly to an aircraft.

Drawings

In the following, preferred embodiments of the invention are described in more detail with the aid of the figures.

Figure 1 is a perspective view of an aircraft according to the invention,

fig. 2 is a schematic representation (overhead and cross-sectional view) of an embodiment of an aircraft structure, having a crack stop element in the form of a low-width FRP strip,

fig. 3 is a schematic representation (overhead and cross-sectional view) of an embodiment of an aircraft structure, having a crack stop element in the form of a high-width FRP strip,

fig. 4 is a schematic representation (overhead and sectional view) of an embodiment of an aircraft structure with crack stop elements arranged between omega-shaped stiffeners and perforated panels,

fig. 5 is a schematic representation (overhead and sectional view) of an embodiment of an aircraft structure, with a crack stop element arranged between a Z-shaped stiffener and a perforated panel,

fig. 6 is a schematic illustration (top view and cross-sectional view) of an embodiment of an aircraft structure with crack stop elements arranged in connection with the stiffeners and furthermore arranged between every two adjacent stiffeners,

fig. 7 is a schematic representation (overhead and sectional view) of an embodiment of an aircraft structure with crack stop elements arranged in connection with every other stiffener,

fig. 8 is a schematic representation (top view and cross-sectional view) of an embodiment of an aircraft structure with crack arrest elements in the form of stiffeners, wherein every other stiffener has a special material suitable for arresting cracks,

fig. 9 is a schematic representation (top view and cross-sectional view) of an embodiment of an aircraft structure with crack arrest elements in the form of stiffeners, wherein every other stiffener has a thickened shape suitable for arresting cracks.

Detailed Description

In fig. 1, an embodiment of an aircraft 1 according to the invention is shown. The aircraft 1 comprises a fuselage 3, wings 5, a vertical tail 7, and a horizontal tail 9. At the wings 5, the vertical tail 7 and the horizontal tail 9, the aircraft 1 comprises an aircraft structure 11 according to any of the embodiments described below.

In fig. 2, a first embodiment of an aircraft structure 11 according to the invention is shown. The aircraft structure 11 comprises a perforated panel 13 having an inner surface 15 directed towards the structure interior 17; an outer surface 19 in contact with an ambient air flow 21; and a plurality of microholes 23 distributed on perforated panel 13 and connecting inner surface 15 and outer surface 19. The perforated panel 13 is formed of a titanium material. A plurality of elongated crack stop elements 25 are attached to the inner surface 15 of the perforated panel 13 parallel to each other. The crack stop element 25 is configured to inhibit the crack from propagating within the perforated panel 13 past the crack stop element 25.

The crack arrest elements 25 extend longitudinally in the main load direction corresponding to the span wise direction of the aircraft structure 11. Furthermore, the crack stop element 25 is formed as a strip of Fibre Reinforced Plastic (FRP) material having a fatigue strength which is much higher than the relevant adjacent part of the perforated panel 13, thereby forming a local Fibre Metal Laminate (FML) together with the perforated panel 13 in the area of the strip. The width w of the crack stop elements 25 of the embodiment shown in fig. 2 is about 1/25 of the distance d between every two adjacent crack stop elements 25.

The embodiment shown in fig. 3 differs from the embodiment of fig. 2 in that the width w of the crack stop elements 25 is about 1/10 of the distance d between every two adjacent crack stop elements 25. Furthermore, due to the high width w of the crack stop element 25, the micro-holes 23 of the perforated panel 13 also extend through the crack stop element 25, so that the micro-holes 23 are not blocked by the crack stop element 25.

In both fig. 2 and 3 it is shown how the crack stop element 25 inhibits the propagation of cracks by: a) prevention of cracks 27; b) slowing the expansion of the crack 27; and c) deflecting the propagation of the crack 27 to an insignificant direction parallel to the crack stop element 25.

In fig. 4 to 9, various embodiments of the aircraft structure 11 are shown, wherein the aircraft structure 11 further comprises an inner panel 29 mounted to the perforated panel 13 via a stiffener 31 attached to the inner surface 15 of the perforated panel 13. The inner panel 29 and the reinforcement 31 are made of FRP material. In the embodiment of fig. 4, 6, 7 and 9, the stiffener 31 has an omega-shaped profile integral with the inner panel 29 and attached to the perforated panel 13. In the embodiment of fig. 5 and 8, the stiffener 31 has a Z-shaped profile attached to the inner panel 29 and the perforated panel 13. At least some of the crack stop elements 25 are disposed between the inner surface 15 of the perforated panel 13 and at least some of the stiffeners 31.

In the embodiment shown in fig. 4 to 6, a crack stop element 25 in the form of an FRP strip is arranged between each reinforcement 31 and the perforated panel 13. In the embodiment shown in fig. 6, the crack stop element 25 is additionally attached to the inner surface 15 of the perforated panel 13 at an intermediate position between each two adjacent stiffeners 31. In the embodiment shown in fig. 7, the crack stop elements 25 are also in the form of FRP strips, but only at every other reinforcement 31.

In the embodiment shown in fig. 8 and 9, instead of being in the form of FRP strips, the crack stop elements 25 are formed by the reinforcement 31 itself. In particular, at least some of the stiffeners 31 are formed as crack stop elements 25. In the embodiment of fig. 8, the reinforcement 31 is formed as a crack stop element 25 by configuring the material of the reinforcement 31 for crack prevention, i.e. selecting the material of the reinforcement 31 such that the reinforcement 31 has a higher fatigue strength than the perforated panel 13.

In the embodiment of fig. 9, the stiffener 31 is formed as a crack stop element 25 by configuring the shape of the stiffener 31 for crack arrest, i.e. selecting the shape of the stiffener 31 such that the stiffener 31 has a higher fatigue strength than the perforated panel 13. This is achieved by providing an increased thickness at the head 33 of the stiffener 31 which is attached to the inner surface 15 of the perforated panel 13.