Fail-safe system intended for an aircraft

Abstract

The failsafe system (2) is for mechanically fastening two aircraft components (6, 8). The failsafe system (2) includes a first group (14), a second group (16) made of a different material than the first group (14), stacking the first group (14) and the second group (16), wherein at least one of the first and second groups (14, 16) includes at least one layer of composite material.

Description

TECHNICAL FIELD

[0001] The present invention relates to the technical field of fail-safe systems intended for aircraft. BACKGROUND

[0002] Fail-safe systems are used in fuselage architecture to improve the reliability of systems embedded within an aircraft, such as the reliability of fastening two parts of an aircraft. In the latter case, a typical fail-safe system uses two different parts made of different materials, each part having two ends fixed to the two parts, respectively. Traditionally, one part is composed of aluminum, while the other part is composed of titanium.

[0003] The mechanical load resulting from the fastening of the two parts is distributed over the two parts of the fail-safe system. Thus, one part is the primary load path, while the other part is the secondary load path. The primary load path is generally the path that bears the load during normal operation of the system.

[0004] If the part that is the primary load path breaks, for example due to an excessive static load or fatigue, the other part takes over the load from the first part. Thus, the failure of the primary load path does not lead to a serious failure of the system.

[0005] A significant drawback of such traditional fail-safe systems is that corrosion or fatigue can occur and reduce the reliability of the system. Furthermore, these systems require a considerable weight and are costly to manufacture. SUMMARY

[0006] The present invention aims to overcome the aforementioned drawbacks.

[0007] More particularly, the present invention aims to obtain a fail-safe system that will better withstand corrosion and fatigue without being significantly heavy.

[0008] According to a first aspect of the invention, a fail-safe system for mechanically fastening two aircraft parts is proposed, the fail-safe system comprising a first group, a second group made of a material different from that of the first group, the first group and the second group being stacked, wherein at least one of the first group and the second group comprises at least one layer of composite material.

[0009] This arrangement allows to take advantage of the strength of composite materials in fatigue and the very good specific mass of composite materials. Thus, the fail-safe system according to the invention is more resistant to fatigue and corrosion, while it is lighter than fail-safe systems of the prior art.

[0010] Advantageously, each group comprises two zones adapted to be fixed to the two aircraft parts, respectively.

[0011] In an embodiment, the materials of the first and second groups are mechanically bound to each other, for example by gluing, welding or any joining technique. In an alternative embodiment, the materials of the first and second groups are not mechanically fastened.

[0012] Preferably, one of the first and second groups comprises a metal sheet.

[0013] In an embodiment, each group comprises a layer of composite material, the material composition of the layer of the first group and the material composition of the layer of the second group being different.

[0014] Such a particular arrangement allows to obtain a fail-safe system as a single multi-layered part, wherein one of the first and second groups constitutes a first load path, while the other group constitutes a second load path. Thus, a fail-safe effect can be obtained while avoiding a doubling of the number of parts, thereby greatly limiting the increase in weight, bulk and manufacturing costs.

[0015] Advantageously, the first and second groups are simultaneously solidified. However, the first and second groups can be made in two distinct parts without departing from the scope of the invention.

[0016] Preferably, the composite material of the layer of the first group comprises fibers having a first stiffness, the composite material of the layer of the second group comprises fibers having a second stiffness, the first stiffness and the second stiffness being different.

[0017] Thus, the fibers of one of the first and second groups can break, while the fibers of the other of the first and second groups remain unbroken. Thus, the fail-safe effect is further improved.

[0018] It is also foreseen a separator sheet interposed between the first and second groups.

[0019] The breaking of the fibers of the composite material releases a large amount of energy and is a brittle breakage, easily propagating to the subsequent group. Thus, the separator sheet acts as a failure propagation breaker to further improve the fail-safe effect.

[0020] Advantageously, the separator sheet is made of a material having an elongation at break at least equal to the minimum elongation at break, and:

[0021] e min = 2 * max(e1, e2)

[0022] where e min is the minimum elongation at break, e1 is the elongation at break of the fibers of the first group, e2 is the elongation at break of the fibers of the second group.

[0023] The choice of such a material significantly improves the efficiency of the separator sheet acting as a failure propagation breaker.

[0024] Preferably, the separator sheet comprises an elastomer.

[0025] This material is particularly suitable for use as a fault propagation circuit breaker between a group comprising composite material layers or sheets and a group comprising metal plates or composite material layers.

[0026] According to another aspect of the present invention, a method for manufacturing a fail-safe system includes the following steps:

[0027] - At least partially manufacture the first set,

[0028] - Manufacture at least partially a second set, which is made of a material different from that of the first set.

[0029] - Stack the first and second groups

[0030] -The steps of manufacturing the first group and / or manufacturing the second group include using at least one layer of composite material.

[0031] Preferably, the step of manufacturing the first group includes stacking multiple layers of the first composite material, and the step of manufacturing the second group includes stacking multiple layers of the second composite material, wherein the first composite material and the second composite material are different, and the method further includes simultaneously curing the first group and the second group after the step of manufacturing the second group.

[0032] According to a third aspect of the invention, the use of the fail-safe system described above in an aircraft is proposed. Attached Figure Description

[0033] The invention and its advantages will be better understood through a study of the detailed description of specific embodiments given by non-limiting examples and illustrated in the accompanying drawings, wherein:

[0034] - Figure 1 This is a perspective view of a fail-safe system according to a first example of the present invention.

[0035] - Figure 2 yes Figure 1 A front view of a fail-safe system.

[0036] - Figure 3 yes Figure 1 and 2 A cross-sectional view of a fail-safe system.

[0037] - Figure 4 This is a perspective view of a fail-safe system according to a second example of the present invention.

[0038] - Figure 5 yes Figure 4 A cross-sectional view of a fail-safe system.

[0039] - Figure 6 This is a perspective view of a fail-safe system according to a third example of the present invention.

[0040] - Figure 7 yes Figure 6 A cross-sectional view of a fail-safe system.

[0041] - Figure 8 This is a perspective view of a fail-safe system according to the fourth example of the present invention.

[0042] - Figure 9 yes Figure 8 A cross-sectional view of a fail-safe system, and

[0043] - Figure 10 A method for manufacturing a fail-safe system is shown. Detailed Implementation

[0044] refer to Figure 1 The diagram schematically illustrates a fail-safe system 2 according to a first example of the invention. The fail-safe system 2 is intended for installation in an aircraft, more specifically in the fuselage structure. However, the fail-safe system 2 can be used in other parts of the aircraft without departing from the scope of the invention.

[0045] An orthogonal direct vector basis 4 is defined to be attached to the fail-safe system 2. Basis 4 consists of vectors X, Y, and Z.

[0046] In this application, the terms “down” and “up” or variations thereof will be understood as relative to a radix-4 reference when the vector Z points vertically upward.

[0047] Similarly, the word "cylindrical" will be understood according to its conventional definition, which is a surface formed by all points on all lines parallel to a given line and passing through a fixed planar curve in a plane not parallel to the given line.

[0048] In the example shown, fail-safe system 2 is designed to mechanically fasten two aircraft components 6 and 8. Figures 1 to 9 Above, components 6 and 8 are schematically depicted as cylindrical parts having a circular cross-section around an axis parallel to vector X. Of course, any geometry of aircraft components 6 and 8 may be used without departing from the scope of the invention.

[0049] from Figure 1 and 2 As can be seen, fail-safe system 2 has an elongated shape, with its longitudinal direction parallel to vector Z. Figure 3 The sectional view is along Figure 2The plane III-III shown is perpendicular to vector Y. The fail-safe system 2 is mechanically fixed to aircraft component 6 near its upper end 10 and to aircraft component 8 near its lower end 12. In the example shown, the fail-safe system 2 is mechanically fixed to aircraft components 6 and 8 via cylindrical holes (not marked) that respectively accommodate portions of aircraft components 6 and 8. However, different fixing methods may be used without departing from the scope of the invention.

[0050] Now for reference Figure 3 The fail-safe system 2 can be divided into a central group 14 and a peripheral group 16. The peripheral group 16 consists of two subgroups 18 and 20. Group 14 and subgroups 18 and 20 are basically planar and perpendicular to vector X. Group 14 and subgroups 18 and 20 are stacked, with group 14 inserted between subgroups 18 and 20.

[0051] In the first example, group 14 and subgroups 18 and 20 are each composed of multilayer sheet or layer composite materials. The composite materials constituting group 14 and subgroups 18 and 20 include epoxy resin and reinforcing fibers. The reinforcing fibers of the composite materials in subgroups 18 and 20 differ from the reinforcing fibers of the composite materials in group 14. More specifically, the stiffness s of the reinforcing fibers in subgroups 18 and 20... 16 The stiffness of the reinforcing fiber of group 14 14 different.

[0052] In this example, the reinforcing fiber of group 14 is carbon fiber, while the reinforcing fibers of subgroups 18 and 20 are glass fiber.

[0053] Fail-safe requirements can be met by using two different groups of composite materials, each made of a different material with different reinforcing fibers and having a different stiffness. For example, carbon composite group 14 can be the primary load path, while glass composite group 16 can be the secondary load path. Under those conditions, group 14 bears the load during normal operation. If group 14 fails, group 16 will take over the load. In other words, fail-safe functionality is ensured through a single multi-layered composite component.

[0054] Although it is assumed in this example that the central group 14 is the primary load path and the peripheral group 16 is the secondary load path, the composition and / or size of groups 14 and 16 can be modified without departing from the scope of the invention, such that the peripheral group 16 becomes the primary load path and the central group 14 becomes the secondary load path.

[0055] Similarly, group 16 can be modified without departing from the scope of the invention so that it includes only one of subgroups 18 and 20.

[0056] In the illustrated example, groups 14 and 16 are each made of a multilayer composite material. However, it is conceivable, without departing from the scope of the invention, that a group is made of only a single layer of composite material.

[0057] This invention is not limited to the reinforcing fibers described above. In particular, without departing from the scope of this invention, carbon fiber or glass fiber may be reversed or replaced by other fibers, such as polymer fibers, flax fibers, basalt fibers, steel fibers, etc.

[0058] Figure 4 and 5 A fail-safe system 22 according to a second example of the present invention is shown. Identical elements have the same reference numerals. Figure 5 The sectional view along with Figure 3 The sectional view is cut off from the same plane.

[0059] The difference between fail-safe system 22 and fail-safe system 2 is that the central assembly 14 is replaced by a central assembly 24 made of a metal plate. Glass composite material assemblies 18 and 20 are overmolded onto the metal plate 24.

[0060] In this example, for instance, metal plate 24 is used as the primary load path, while glass fiber composite assembly 16 is used as the secondary load path.

[0061] As in the first example, the glass fiber composite assembly 16 can be used as the primary load path, while the metal plate 24 can be used as the secondary load path. Similarly, in another variation, assembly 24 can be composed of multiple layers of composite material, while assembly 16 can be composed of two metal plates surrounding the composite assembly 24.

[0062] exist Figure 6 and 7 The figure depicts a fail-safe system 26 according to a third example of the present invention. Identical elements have the same reference numerals. Figure 7 The sectional view along with Figure 3 The sectional view is cut off from the same plane.

[0063] The difference between fail-safe system 26 and fail-safe system 2 is that it also includes separators 28 and 30 between groups 14 and 16. That is, separator 28 is inserted between subgroup 18 and group 14, and separator 30 is inserted between group 14 and subgroup 20.

[0064] Separators 28 and 30 are made of materials with an elongation at break e 2830 Made of [material name]. Elongation e 2830 It has more than twice the breaking elongation of the most stretchable reinforcing fibers in groups 14 and 16. In other words:

[0065] e 2830 ≥2*max(ecarbon e glass )

[0066] Among them, e carbon and e glass These are the elongation at break of carbon fiber and glass fiber, respectively.

[0067] In this example, separators 28 and 30 are made of elastomer.

[0068] Although separators 28 and 30 have been described with reference to examples of each group made of composite material layers, in Figure 4 and 5 In the example, the separator can be inserted next to group 24, which is made of metal plates.

[0069] In the latter case, the elongation at break of the separator is e 2830 It can be, for example, twice the elongation at break of the reinforcing fibers in composite group 16. That is to say, in Figure 4 and 5 In the example:

[0070] e 2830 ≥2*e glass

[0071] Figure 8 and 9 A fail-safe system 32 according to a fourth example of the present invention is shown. Identical elements have the same reference numerals. Figure 9 The sectional view along with Figure 3 The sectional view is cut off from the same plane.

[0072] The difference between fail-safe system 32 and fail-safe system 2 is that group 14 includes three subgroups 34, 36, and 38. Subgroups 34, 18, 36, 20, and 38 are stacked in this order.

[0073] Now for reference Figure 10 The method of manufacturing the fail-safe system 32 will now be described.

[0074] Figure 10 The method includes a first step E01 for manufacturing sub-assembly 34. In step E01, multiple layers of carbon composite material are stacked. Step E01 ends when sub-assembly 34 is manufactured.

[0075] The method includes a second step E02 for manufacturing sub-assembly 18. In step E02, a multilayer glass composite material is directly stacked on sub-assembly 34 formed during the previous step E01. Step E02 ends when sub-assembly 18 is manufactured and stacked on sub-assembly 34.

[0076] The method also includes steps E03, E04, and E05, whereby the individual subgroups 36, 20, and 38 are directly stacked on top of previously manufactured subgroups. During each step E03, E04, and E05, the manufactured subgroups are formed directly by stacking composite material layers on top of the subgroups manufactured in the previous steps. During steps E03 and E05, the stacked composite material layers comprise carbon fibers, while during step E04, the stacked composite material layers comprise glass fibers. At the end of step E05, groups 14 and 16 are manufactured and stacked as follows: Figure 8 and 9 As shown.

[0077] Then, Figure 10 The method includes a sixth step, E06, in which groups 14 and 16 are cured simultaneously. At the end of step E06, groups 14 and 16 are stacked to form a single multilayer composite part.

[0078] Right now, Figure 10 The method does not include any additional steps compared to methods for manufacturing classic composite material parts. Therefore, this invention allows for the manufacture of fail-safe systems without increasing manufacturing costs, weight, or making the components more bulky.

Claims

1. A fail-safe system (2, 22, 26, 32) for mechanically fastening two aircraft components (6, 8), the fail-safe system (2, 22, 26, 32) comprising a first group (14, 24) and a second group (16), the second group (16) being made of a material different from that of the first group (14, 24), the second group (16) comprising two subgroups (18, 20), stacking the first group (14, 24) and the second group (16), the first group being inserted between the two subgroups (18, 20), wherein, At least one of the first and second groups (14, 16) includes at least one layer of composite material; The first group (14, 24) and at least two subgroups (18, 20) are substantially planar, and cylindrical holes extending through the thickness of the first group (14, 24) and the second group (16) are respectively used to receive a portion of two aircraft components (6, 8) to mechanically secure the fail-safe system to the aircraft components.

2. The fail-safe system (22) according to claim 1, wherein, One of the first and second groups (24, 16) includes a metal plate.

3. The fail-safe system (2, 26, 32) according to claim 1, wherein, Each group (14, 16) includes a composite material layer, and the material composition of the layer in the first group (14) is different from that of the layer in the second group (16).

4. The fail-safe system (2, 26, 32) according to claim 3, wherein, The composite material of the first group (14) of layers includes fibers with a first stiffness, and the composite material of the second group (16) of layers includes fibers with a second stiffness, wherein the first stiffness and the second stiffness are different.

5. The fail-safe system (26) according to any one of claims 1 to 4 further includes a separator (28, 30) inserted between the first group (14) and the second group (16).

6. The fail-safe system (26) according to claim 5, which is dependent on claim 4, wherein, The separators (28, 30) are made of a material whose elongation at break is at least equal to the minimum elongation at break, and: ， Among them, e min e1 is the minimum breaking elongation, e2 is the breaking elongation of the fibers in the first group (14), and e2 is the breaking elongation of the fibers in the second group (16).

7. The system (26) according to claim 5 or 6, wherein, The separators (28, 30) comprise an elastomer.

8. A method of manufacturing a fail-safe system (2, 22, 26, 32) according to any one of claims 1 to 7, comprising the following steps: - At least partially manufacture (E01) the first group (14, 24). - To manufacture at least partially (E02) a second group (16) made of a material different from that of the first group (14, 24), The second group (16) includes two subgroups (18, 20). - Stack (E02) first group (14, 24) and second group (16). The first group is inserted between the two subgroups (18, 20). - Wherein, the step (E01) of manufacturing the first group (14, 24) and / or the step (E02) of manufacturing the second group (16) involve using at least one layer of composite material; Fail-safe systems (2, 22, 26, 32) are used to mechanically fasten two aircraft components (6, 8).

9. The method according to claim 8, wherein, The step (E01) of manufacturing the first group (14) includes stacking multiple layers of the first composite material, and the step (E02) of manufacturing the second group (16) includes stacking multiple layers of the second composite material, wherein the first composite material and the second composite material are different, and the method further includes simultaneously curing (E06) the first group (14) and the second group (16) after the step (E02) of manufacturing the second group (16).

10. Use of the fail-safe system (2, 22, 26, 32) according to any one of claims 1 to 7 in an aircraft.

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