Indication bolt for monitoring adhesive bonds in structural elements

Abstract

A structural element includes a first component and a second component; a bonded joint, by which the first component and the second component are interconnected; and an indication bolt, which is fixed to the first component and the second component. The indication bolt is designed to indicate when the first component and the second component have moved relative one another.

Claims

1. A structural element, comprising: a first component and a second component; a bonded joint, by which the first component and the second component are interconnected; and an indication bolt, which is fixed to the first component and the second component, wherein the indication bolt is designed to indicate when the first component and the second component have moved relative to one another, wherein the indication bolt has a predetermined breaking point, which deforms under a predetermined loading of the indication bolt introduced by the relative movement of the first and second component or breaks under the predetermined loading of the indication bolt introduced by the relative movement of the first and second component to detect whether the relative movement of the first component and the second component has taken place, wherein the predetermined breaking point is a narrowed region adjacent to a head of the indication bolt.

2. The structural element as claimed in claim 1, wherein the indication bolt is designed to plastically deform when the first component and the second component have moved relative to one another.

3. The structural element as claimed in claim 1, wherein the indication bolt is received in at least one opening in the first component and/or second component, wherein the at least one opening in the first component and/or the second component has a diameter that is larger than a diameter of the indication bolt.

4. The structural element as claimed in claim 1, wherein the head of the indication bolt is fixed to the first component, and the indication bolt has an elongated foot, which is fixed to the second component, wherein the head deflects under a predetermined loading of the indication bolt in relation to the foot, or wherein the head detaches from the foot of the indication bolt under a predetermined loading of the indication bolt.

5. The structural element as claimed in claim 1, wherein the head of the indication bolt is recessed in the first component, such that the first component together with the head form a flush surface.

6. The structural element as claimed in claim 1, wherein the indication bolt comprises a cavity, which is opened in the event of deformation of the indication bolt.

7. The structural element as claimed in claim 6, wherein the cavity contains a detectable substance.

8. The structural element as claimed in claim 6, wherein the cavity contains a signal color substance.

9. The structural element as claimed in claim 1, wherein the indication bolt is riveted to the structural element.

10. The structural element as claimed in claim 1, wherein a foot of the indication bolt is screwed into at least the second component.

11. An aircraft, comprising: a structural element comprising: a first component and a second component; a bonded joint, by which the first component and the second component are interconnected; and an indication bolt, which is fixed to the first component and the second component, wherein the indication bolt is designed to indicate when the first component and the second component have moved relative to one another, wherein the indication bolt has a predetermined breaking point, which deforms under a predetermined loading of the indication bolt introduced by the relative movement of the first and second component or breaks under the predetermined loading of the indication bolt introduced by the relative movement of the first and second component to detect whether the relative movement of the first component and the second component has taken place, wherein the predetermined breaking point is a narrowed region adjacent to a head of the indication bolt.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a schematic three-dimensional view of a supporting structure of an aircraft in accordance with one embodiment of the invention.

(2) FIG. 2 shows a schematic cross section through a structural element in accordance with one embodiment of the invention.

(3) FIG. 3 shows a schematic cross section through a structural element having an undamaged indication bolt in accordance with one embodiment of the invention.

(4) FIG. 4 shows a schematic cross section through a structural element having a damaged indication bolt in accordance with one embodiment of the invention.

(5) FIG. 5 shows a schematic cross section through a structural element having a damaged indication bolt in accordance with one embodiment of the invention.

(6) FIG. 6 shows a schematic cross section through a structural element having a damaged indication bolt in accordance with one embodiment of the invention.

(7) FIG. 7 shows a schematic cross section through a structural element having an undamaged indication bolt in accordance with one embodiment of the invention.

(8) FIG. 8 shows a schematic cross section through a structural element having a damaged indication bolt in accordance with one embodiment of the invention.

(9) FIG. 9 shows a flow diagram for a method for detecting a defective bonded joint in accordance with one embodiment of the invention.

(10) FIG. 10 shows a schematic cross section through a structural element having an indication bolt in accordance with one embodiment of the invention.

(11) In principle, identical or similar parts are provided with like reference signs.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(12) FIG. 1 shows a detail of a supporting structure 10 of an aircraft 12, which has an outer skin 18 stiffened by formers 14 and stringers 16. The stringers 16 comprise bonded reinforcements, which run in a longitudinal direction of the aircraft 10.

(13) FIG. 2 shows a detail from FIG. 1 with a structural element 20, which shows part of the outer skin 18 and part of a stringer 16. Here, the stringer 16 is formed by an outer shell 22, which forms part of the outer skin 18, and an inner shell 24, which is bonded to the outer shell 22. On the whole, the supporting structure has a shell structure with glued-in reinforcements.

(14) The outer shell 22 here represents a first component 22 of the structural element 20, which is connected to the inner shell 24 as second component 24 via a bonded joint 26 in the form of a glue line.

(15) The first component 22 and the second component 24 are additionally connected via an indication bolt 28, which is arranged in a region 30 such that it is exposed to a high load in the event of failure of the bonded joint 26.

(16) As is clear from FIG. 1, one or more bonded joints 26 between the two components 22, 24 can be secured in each case via a number of indication bolts 28.

(17) FIG. 3 shows a detail from FIG. 2. In a surrounding environment of the indication bolt 28, the two components 22, 24 can be constructed in a planar and/or plate-like manner. The bonded joint 26 may comprise a layer of adhesive material between the two components 22, 24.

(18) The indication bolt 28 is received in an opening 32 in the structural element 20 and is fixed to the structural element 20. For this purpose, the indication bolt 28 has a foot 34, which is fixed by way of a thickening 36 to the second thickening, such that the indication bolt 28 is held on the second component 24 in the opening 32. The indication bolt 28 also has a head 38, which is thickened in relation to the foot 34, such that the indication bolt 28 is also held on the first component 22 in the opening 32.

(19) When the bonded joint 26 is damaged and the two components 22, 24 are loaded by forces and loads that are exerted onto the structural component 20, a relative movement beyond a predetermined limit value may be produced. By way of example, the two components 22, 24 may lift from one another and/or may shift along the bonded joint 26.

(20) The predetermined limit value can be set, for example, via the resilient behavior of the indication bolt 28 or via a play between the indication bolt 28 and the first component 22 and/or the second component 24. By way of example, the opening 32 has a diameter that is slightly larger than the diameter of the foot 34 of the indication bolt 28.

(21) In the case of a sufficient large relative movement of the two components 22, 24, the indication bolt is then loaded in such a way that, for example, the head 38 thereof is sheared off or at least bent.

(22) Between the head 38 and the foot 34, the indication bolt 28 has a predetermined breaking point 40, which constitutes a narrowed portion of the indication bolt 28. The size of the predetermined breaking point 40 is coordinated such that the predetermined breaking point 40 at least permanently deforms or tears in the event of a determined load on the indication bolt 28.

(23) FIG. 4 shows that the head 38 of the indication bolt 28 can be shifted or bent by a deformation of the indication bolt 28 relative to the foot 34.

(24) As is clear from FIG. 3, the head 38 can be received, for example, in an indentation 42, such that the surface of the head 38 is flush with the surface of the first component 22 when the indication bolt 28 is not deformed. Following the deformation, the head 38 may protrude beyond the indentation, such that a deformation of the indication bolt 28 is easily visible from outside as well.

(25) FIG. 5 shows that the head 38 in the event of deformation of the indication bolt 28 can also be fully separated from the foot 34, such that the indentation 42 is exposed.

(26) Although, as is shown in FIG. 6, the head 38 of the indication bolt 28 does not exhibit visible deformation, a crack 44, for example through the predetermined breaking region 40, can be detected by way of a measuring device or sensor 46, which for example determines eddy currents in the indication bolt 28 or electrical resistance thereof.

(27) In FIG. 7 it is illustrated that the indication bolt 28 may have a cavity 50, in the interior of which a substance 52 is enclosed when the indication bolt 28 is not deformed.

(28) If the indication bolt 28 deforms, for example in that the head 38 is sheared off in part, a connection from the cavity 50 outwardly is produced, and the substance 52, for example a signal color, can escape from the indication bolt 28.

(29) In FIG. 7, it is additionally shown that the opening 32 can penetrate the two components 22, 24 fully, or however also penetrates the second component 24 only partially. In both cases the indication bolt 28 can be screwed or glued into the second component 24.

(30) FIG. 8 shows a method for detecting damage to the structural element 20, in which it is determined whether the two components 22, 24 have loaded the indication bolt 28 to such an extent that the indication bolt has deformed.

(31) Referring to the flow chart of FIG. 9, in step 100, the two components 22, 24 are bonded, such that the bonded joint 26 is produced.

(32) In step 102, an opening 32 through the two components 22, 24 is produced. By way of example, the opening can be provided already during the production of the components 22, 24 or can be drilled subsequently in the two components 22, 24. The opening 32 can be produced at the same time as the bonding in step 100, beforehand, or subsequently.

(33) In step 104, an indication bolt 28 is inserted into the opening 32. The indication bolt 28 does not have to be rigidly connected to both components 22, 24, but can be fixed merely in the opening 32 such that it is loaded when the two components 22, 24 move relative to one another. The fixing can be provided in part to the conical head 38, for example.

(34) The foot 34 of the indication bolt 28 for example can be screwed and/or glued into one of the components 22, 24. The indication bolt 28 can also be held in the opening 32 by way of a rivet connection.

(35) The structural element 20 can then be used for its intended purpose. If the bonded joint 26 is damaged (for example by an overload or by material fatigue), the two components 22, 24 can move relative to one another (beyond a predetermined limit value). The indication bolt 28 is configured or designed such that it starts to deform when this limit value is exceeded.

(36) Due to the deformation of the indication bolt 28, the head 38 of the indication bolt 28 for example may be bent or sheared off and/or a cavity 50 in the interior of the indication bolt 28 may be opened as shown in FIG. 8.

(37) In step 106, the integrity of the indication bolt 28 is tested. This can be performed by visual check, by means of a measuring device and/or a sensor 46.

(38) With a visual check it is possible to determine whether the head 38 of the indication bolt 28 is bent or still present or whether a signal color 52 has leaked. A bent or absent head 38 or the presence of a signal color 52 indicates that the bonded joint 26 has been damaged.

(39) With a measuring device or sensor 46, an eddy current measurement can be carried out on the indication bolt 28, or an electrical resistance of the indication bolt 28 can be determined. If the eddy current or the resistance falls below a predetermined value, this indicates damage to the bonded joint 26.

(40) With a measuring device or sensor 46, a substance 52 leaking from the indication bolt 28 can be detected (for example whilst the substance is leaking). This can be implemented simultaneously during the intended use of the composite element 20. With a measuring device or sensor 46, a sound that is emitted by the indication bolt 28 in the event of deformation or shattering can also be recorded. The sensor values can be recorded and analyzed later. A sounding of the measuring device or sensor 46 or certain sensor values then indicates damage to the bonded joint 26.

(41) FIG. 10 shows a further embodiment of an indication bolt 28, which is designed to move in a predefined direction in the event of a lifting of the joint 26. The indication bolt 28 for example may have barbs 48 or corrugations (asymmetric with respect to the direction). When, for example, the two components 22, 24 lift a number of times from one another, the indication bolt 28 moves in the direction described by the arrow. It is then possible to check by visual check whether the indication bolt 28 protrudes from the opening 32, which indicates that the bonded joint 26 is defective.

(42) In addition, it is noted that comprising does not rule out any other elements or steps, and a or one does not rule out a plurality. It is also noted that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other above-described exemplary embodiments. Reference signs in the claims are not to be considered as limiting.