STRUCTURAL MONITORING SYSTEM FOR A COMPONENT OF FURNITURE MADE OF COMPOSITE MATERIAL

Abstract

The present invention relates to a structural monitoring system (21) comprising: - at least one optical fiber (23) fixed to an external face or disposed within the composite wall (26), - a laser emitter (27) disposed at a first end of the optical fiber (23) capable of generating an input optical signal, - a laser receiver (28) disposed at a second end of the optical fiber (23) capable of receiving an output optical signal, and - an electronic processing unit (30) capable of detecting, as a function of the output optical signal, a displacement and / or deformation of the optical fiber (23) representative of a mechanical stress applied to the composite wall (26). Figure for the abstract: Figure 2

Description

Title of the invention: STRUCTURAL MONITORING SYSTEM FOR AN ELEMENT OF FURNITURE MADE OF COMPOSITE MATERIAL

[0001] The present invention relates to a structural monitoring system for a furniture element made of composite material. The invention finds a particularly advantageous, but not exclusive, application in the field of aeronautics, for monitoring, using optical fibers, furniture elements of business and first-class passenger seats, such as privacy pods or side consoles associated with the seats.

[0002] Various technologies exist in the prior art for monitoring the health of composite structures. In addition to resistive strain gauges, piezoelectric sensor arrays are known for integration into composite structures to detect variations in mechanical stress, deformation, or potential damage. Piezoelectric sensors exploit the piezoelectric phenomenon, whereby certain materials generate an electrical charge in response to mechanical stress. When these sensors are integrated into a structure, stress variations, such as vibrations or deformations, induce measurable electrical charges, enabling real-time monitoring of the structure's condition.

[0003] This type of sensor has been used for monitoring the structural health of aircraft seat shells made of composite material. However, these solutions have certain limitations, including high sensitivity to positioning and temperature, very localized measurement, material fragility, the need for regular calibration, limited frequency response, maintenance requirements, and complex data interpretation.

[0004] The invention aims to effectively remedy the aforementioned drawbacks by proposing an assembly comprising: - a piece of furniture comprising at least one composite wall, and - a structural monitoring system comprising: - at least one optical fiber fixed to an external face or arranged within the composite wall, - a laser emitter positioned at one end of the optical fiber capable of generating an input optical signal, - a laser receiver located at a second end of the optical fiber capable of receiving an output optical signal, and - an electronic processing unit capable of detecting, based on the output optical signal, a displacement and / or deformation of the optical fiber representative of a mechanical stress applied to the composite wall.

[0005] The invention thus makes it possible to ensure real-time structural monitoring of a furniture component, in particular a side console or an aircraft seat shell, throughout the life cycle of the composite material. The invention allows for a complete analysis of deformations and mechanical stresses, useful for monitoring the condition of the furniture component and for predictive maintenance, enabling intervention before a defect occurs. Furthermore, the invention allows for the rapid, reliable, and secure transmission of a significant amount of information while being minimally intrusive and insensitive to electromagnetic radiation. The invention also exhibits greater dynamic range and sensitivity than traditional sensors. Compared to the use of piezoelectric sensors, the invention makes it possible to significantly increase the number of measurement points and to extract reliable data on the seat's behavior.The invention also enables the creation of a database for improving the design of aircraft seat furniture and recording events, as well as optimizing numerical simulation models.

[0006] According to one embodiment of the invention, the composite wall comprises at least one composite skin comprising at least two plies made of a pre-impregnated material, the optical fiber being disposed between the two plies of pre-impregnated composite material.

[0007] According to one embodiment of the invention, the composite wall comprises: - a central core made of a honeycomb material, and - two composite skins arranged on either side of the central core, - the optical fiber being arranged between two prepreg layers of one of the two composite skins.

[0008] According to one embodiment of the invention, the optical fiber is covered by an external layer of a heat-resistant protective coating.

[0009] According to one embodiment of the invention, the optical fiber is fixed on an external face of a skin of the composite wall.

[0010] According to one embodiment of the invention, the optical fiber has a serpentine-shaped configuration.

[0011] According to one embodiment of the invention, the optical fiber has a straight-line shape configuration.

[0012] According to one embodiment of the invention, the optical fiber has a spiral-shaped configuration.

[0013] According to one embodiment of the invention, the electronic processing unit is capable of generating a two-dimensional map of relative displacements of the optical fiber representative of stresses applied on the composite wall.

[0014] According to one embodiment of the invention, the electronic processing unit comprises: - an output signal shaping module associated with an analog-to-digital converter, - a Fourier transform module to transform a time-domain signal into a frequency-domain signal, - a frequency signal windowing module, - an inverse Fourier transform module to transform the windowed frequency signal into a time-domain matched signal, and - a suitable time signal filtering and centering module.

[0015] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0016] [Fig.1] Fig.1 is a perspective view of an aircraft seat unit comprising a side console integrating a structural monitoring system according to the invention;

[0017] [Fig.2] Fig.2 is a perspective view showing optical fibers of a structural monitoring system integrated into the walls of a seat console;

[0018] [Fig. 3] Fig. 3 is an exploded perspective view of a composite wall of a seat console or privacy shell used for the implementation of the invention;

[0019] [Fig.4] Fig.4 is a cross-sectional view illustrating a positioning of an optical fiber between two folds of a composite wall according to the invention;

[0020] [Fig. 5a] [Fig. 5b] [Fig. 5c] Figures 5a, 5b and 5c are representations schematics illustrating different possible configurations of an optical fiber used with the structural monitoring system according to the invention;

[0021] [Fig.6] Fig.6 is a schematic representation of the different modules of a electronic processing unit capable of determining a mechanical stress as a function of an optical signal detected at the output of an optical fiber;

[0022] [Fig.7] Fig.7 shows a test device applying a mechanical force to a composite wall equipped with a structural monitoring system according to the invention;

[0023] [Fig.8] The [Fig.8] is a schematic top view representation of the test device of the [Fig.7] used with an optical fiber having a serpentine configuration;

[0024] [Fig.9a] [Fig.9b] Figures 9a and 9b are 2D displacement maps relative to the optical fiber representative of stresses applied on the composite wall obtained for an optical fiber oriented respectively along the warp direction and the weft direction of the fibers of a prepreg material.

[0025] It should be noted that, in the figures, structural and / or functional elements common to the different embodiments may have the same reference numerals. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0026] Fig. 1 shows a seating unit 10 comprising a seat 11 convertible into a bed including a frame 12 on which are mounted a seat 13 and a backrest 15.

[0027] Seat 11 is associated with a side console 16 extending along one side of seat 11. The side console 16 may include a table surface 17 on which a passenger can place personal items or their meal tray, among other things. The side console 16 may also include a vertical storage space 20 comprising one or more items such as a bookcase, a bottle holder, or a minibar. The choice of storage options is configurable according to the airline's requirements.

[0028] In addition, a privacy shell 18 extends at least partially around the seat 11 so as to delimit a semi-enclosed space around the passenger. Such a configuration ensures the privacy of the passenger seated in seat 11.

[0029] The seat 11 is advantageously equipped with a kinematic mechanism allowing it to move between a "seated" position, in which the seat 11 is configured to define a passenger's seated position, particularly during taxiing, takeoff, and landing phases of an aircraft, and a "bed" position, in which the seat 11 is configured to define a substantially horizontal sleeping surface for the passenger. To this end, the backrest 15 is capable of pivoting around a horizontal axis perpendicular to an extension axis of the seat 11. The backrest 15 is thus movable between a raised position and a lowered position in which the backrest 15 extends in the same plane as the seat 13 to form, together with the seat 13, the sleeping surface.In order to ensure the movement of the various elements of the seat 11 from the sitting position to the bed position, the seat 11 includes one or more actuators ensuring a movement of the backrest 15 backwards and, where applicable, of the seat 13 forwards.

[0030] A housing 19 in which a footrest is arranged is provided in the side console 16. The housing 19 is open towards the rear seat 11, so that the passenger seated in the rear seat 11 can place his feet on the footrest, in particular when the rear seat 11 is in the bed position.

[0031] A structural monitoring system 21 visible in [Fig.2] includes at least one optical fiber 23 disposed on an external face or within a composite wall 26 of the side console 16.

[0032] The monitoring system 21 also includes a laser emitter 27 located at one end of the optical fiber 23, capable of generating an input optical signal, and a laser receiver 28 located at the other end of the optical fiber 23, capable of receiving an output optical signal. An electronic processing unit 30 is capable of detecting, based on the output optical signal, a displacement and / or deformation of the optical fiber 23 representative of a mechanical stress applied to the composite wall 26. To facilitate understanding of the figure, only one optical fiber 23 has been associated with a laser emitter 27 and a laser receiver 28, but it is evident that all optical fibers 23 are associated with a laser emitter 27 and a laser receiver 28, which may nevertheless be common to several optical fibers 23.

[0033] In this case, an optical fiber 23 is arranged on an external face or within a vertical composite wall 26.1 of the end into which an end of the housing 19 opens towards a rear seat.

[0034] An optical fiber 23 is disposed on an external face or within a first lateral composite wall 26.2 extending vertically and perpendicularly to the composite wall 26.1.

[0035] An optical fiber 23 is disposed on an external face or within a second lateral composite wall 26.3 extending vertically and perpendicularly to the composite wall 26.1.

[0036] An optical fiber 23 is disposed on an external face or within an upper composite wall 26.4 delimiting at least part of the footrest housing 19. The upper wall 26.4 extends along a horizontal plane.

[0037] An optical fiber 23 is disposed on an external face or within at least one lateral composite wall 26.5 delimiting the footrest housing 19. The lateral wall 26.5 extends along a vertical plane perpendicular to the wall 26.4.

[0038] Of course, it is possible to modify the number and arrangement of the optical fibers 23. Some of the aforementioned walls may be devoid of optical fibers 23. One or more optical fibers 23 may also be integrated into the privacy shell 18 made of a composite material. One or more optical fibers 23 may be integrated into any other furniture element associated with the seat 11 or an aircraft cabin.

[0039] As illustrated in [Fig. 3], a composite wall 26 comprises a central core 35 made of a honeycomb material. The central core 35 is a central layer of the composite wall 26. In addition, two composite skins 31 are arranged on either side of the central core 35.

[0040] Each composite skin 31 is made of a monolithic laminated composite material. Each composite skin 31 comprises at least two plies 32 made of a prepreg material.

[0041] Preferably, as shown in [Fig. 4], the optical fiber 23 is arranged between two plies 32 of prepreg composite material of one of the two composite skins 31. A ply 32 of material corresponds to a thin sheet of composite material. A prepreg is a semi-finished composite product consisting of a thermosetting resin (also called a matrix) or a partially polymerized thermoplastic polymer impregnating fibers. Alternatively, the fibers of the prepreg composite material are carbon fibers or any other type of fiber suitable for the application.

[0042] The optical fiber 23 is preferably arranged between two layers 32 pressed together before the composite wall 26 is cured. Thus, during the manufacture of the composite wall 26, the optical fiber 23 is arranged between the two layers 32 during a draping operation consisting of cutting layers 32 of prepreg and manually draping them in a mold that will give the composite wall 26 its shape. A smearing operation is also performed on the layers 32 of prepreg. The "skin 31-core 35-skin 31" assembly is then heated to complete the polymerization of the resin in the prepreg material. The curing of the composite wall 26 can be carried out under vacuum or in an autoclave.

[0043] To prevent damage to the optical fiber 23 during the heating step, the optical fiber 23 can be covered by an outer layer 24 of a heat-resistant protective coating. The protective coating is, for example, made of polyimide capable of withstanding temperatures up to 350°C or any other material resistant to heat exceeding the curing temperature of the composite material.

[0044] Alternatively, the composite wall 26 is devoid of a central core 35 and consists only of several layers 32 of prepreg stacked one on top of the other.

[0045] Alternatively, the optical fiber 23 is fixed to an external face of a skin of the composite wall 26. The fixing of the optical fiber 23 to the external face of a skin is preferably carried out by gluing.

[0046] As illustrated in Figures 2, 4, and 5a, the optical fiber 23 has a serpentine configuration. According to this configuration, the optical fiber 23 comprises a plurality of basic segments 23.1 and a plurality of link segments 23.2, each providing a link between two successive basic segments 23.1. There is an alternation between the basic segments 23.1 and the link segments 23.2. The basic segments 23.1 can be straight and parallel to each other with respect to the others, as shown in the figures. Alternatively, the basic sections 23.1 can be slightly curved.

[0047] Two end base segments 23.1 are distinguished, each located at one end of the optical fiber 23, and one or more intermediate base segments 23.1 are arranged between the two end base segments 23.1.

[0048] On a given intermediate base section 23.1, the connecting sections 23.2 located at both ends are oriented in two directions opposite to each other. An end base section 23.1 is connected only to a connecting section 23.2. An end base section 23.1 is associated with the laser emitter 27 or the laser receiver 28.

[0049] Such a serpentine configuration allows the optical fiber 23 to maximize the coverage of the surface of the composite wall 26.

[0050] According to the embodiment of [Fig.5b], the optical fiber 23 has a straight-line shape configuration.

[0051] According to the embodiment of [Fig. 5c], the optical fiber 23 has a spiral-shaped configuration. In order to integrate a spiral-shaped optical fiber 23, several factors must be taken into account, including the radius of curvature and the complexity associated with integrating this fiber 23. Advantageously, this type of spiral-shaped fiber 23 is integrated on the composite wall 26 and not between the plies 32.

[0052] As illustrated in [Fig.6], the electronic processing unit 30 includes a module 30.1 for shaping the output optical signal 34 associated with an analog / digital converter.

[0053] A Fourier transform module 30.2 is capable of transforming a time signal into a frequency signal.

[0054] A module 30.3 is capable of performing a windowing of the frequency signal allowing the frequency signal to be isolated on one or more frequency ranges.

[0055] An inverse Fourier transform module 30.4 is capable of transforming the windowed frequency signal into a suitable time signal.

[0056] A filtering and centering module 30.5 is suitable for filtering and centering the adapted time signal.

[0057] Advantageously, the output laser signal 34 transmitted to an optical fiber 23 has a wavelength between 1538 nm and 1558 nm. An optical fiber 23 may include a Bragg grating. For this purpose, the optical fiber 23 has a core with a variable refractive index (alternating between a high and a low refractive index) along its length. It is also possible to implement a distributed detection system using a simple single-mode or multimode optical fiber 23. Such a distributed detection system is based on the Rayleigh principle.

[0058] A displacement of the optical fiber 23 due to the application of a mechanical stress on the composite wall 26 modifies a wavelength of the optical signal passing through the optical fiber 23. The electronic processing unit 30 is therefore able to detect, as a function of the output optical signal, in particular as a function of a variation in wavelength of the output optical signal, a displacement and / or a deformation of the optical fiber 23 representative of a mechanical stress applied to the composite wall 26.

[0059] Fig. 7 shows a test device 38 comprising two fixed supports 39 on which a composite wall 26 incorporating an optical fiber 23 rests. A block 42 disposed between the two fixed supports applies a mechanical force F normal to the composite wall 26. The composite wall 26 extends in the XY plane while the mechanical force F is applied along the Z axis.

[0060] As illustrated in [Fig. 8], the optical fiber 23 is arranged in the XY plane in a serpentine configuration. The distances dx and dy are predetermined and are, for example, 5 cm each. The various points correspond to nodes where a displacement dz of the optical fiber 23 is to be measured along the Z-axis, representing a stress applied to the composite wall 26. The displacement dz of the optical fiber 23 is thus measured in a direction normal to the plane in which the optical fiber 23 extends.

[0061] The electronic processing unit 30 is capable of generating a two-dimensional map of relative displacements dz of the optical fiber 23 representative of stresses applied to the composite wall 26, as shown in Figures 9a and 9b. Figure 9a was obtained for a serpentine optical fiber 23 having base sections 23.1 oriented along the warp direction of the prepreg material fibers (in the X-axis). Figure 9b was obtained for a serpentine optical fiber 23 having base sections 23.1 oriented along the weft direction of the prepreg material fibers (in the Y-axis).

[0062] From these test results obtained for limit forces observable during the life phase of composite walls 26, it is possible, by improving the numerical simulation models, to optimize the design of these composite walls 26 in order to improve their mechanical strength.

[0063] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0064] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the framework of the present invention and in particular all combinations of the different modes of operation described above, which can be taken separately or in association.

Claims

Demands

1. Assembly characterized in that it comprises: - a furniture element (16) comprising at least one composite wall (26), and - a structural monitoring system (21) comprising: - at least one optical fiber (23) fixed on an external face or disposed within the composite wall (26), - a laser emitter (27) disposed at a first end of the optical fiber (23) capable of generating an input optical signal, - a laser receiver (28) disposed at a second end of the optical fiber (23) capable of receiving an output optical signal, and - an electronic processing unit (30) capable of detecting, as a function of the output optical signal, a displacement and / or deformation of the optical fiber (23) representative of a mechanical stress applied to the composite wall (26).

2. Assembly according to claim 1, characterized in that the composite wall (26) comprises at least one composite skin (31) comprising at least two plies (32) made of a pre-impregnated material, the optical fiber (23) being disposed between the two plies (32) of pre-impregnated composite material.

3. Assembly according to claim 2, characterized in that the composite wall (26) comprises: - a central core (35) made of a honeycomb material, and - two composite skins (31) arranged on either side of the central core (35), - the optical fiber (23) being arranged between two plies (32) of prepreg of one of the two composite skins (31).

4. Assembly according to any one of claims 1 to 3, characterized in that the optical fiber (23) is covered by an outer layer (24) of a heat-resistant protective coating.

5. Assembly according to claim 1, characterized in that the optical fiber (23) is fixed on an external face of a skin of the composite wall (26).

6. Assembly according to any one of claims 1 to 5, characterized in that the optical fiber (23) has a serpentine configuration.

7. Assembly according to any one of claims 1 to 5, characterized in that the optical fiber (23) has a straight-form configuration.

8. Assembly according to any one of claims 1 to 5, characterized in that the optical fiber (23) has a spiral-shaped configuration.

9. Assembly according to any one of claims 1 to 8, characterized in that the electronic processing unit (30) is capable of generating a two-dimensional map of relative displacements of the optical fiber (23) representative of stresses applied on the composite wall (26).

10. Assembly according to any one of claims 1 to 9, characterized in that the electronic processing unit (30) comprises: - an output signal shaping module (30.1) associated with an analog / digital converter, - a Fourier transform module (30.2) for transforming a time signal into a frequency signal, - a frequency signal windowing module (30.3), - an inverse Fourier transform module (30.4) for transforming the windowed frequency signal into a matched time signal, and - a matched time signal filtering and centering module (30.5).

Images