Method for manufacturing a multicellular panel via conductive welding or radiative welding

Abstract

The invention relates to a method for manufacturing a multicellular panel (500) comprising a cellular structure (300) and a first skin (100) made of a thermoplastic composite material, the cellular structure (300) comprising a plurality of walls (330) extending in a first direction (X) between a first face (310) and a second face (320) of the cellular structure (300), the method comprising welding the first skin (100) to the first face (310) of the cellular structure (300), the welding process comprising a step of heating the first skin via a radiative source (600) or a resistive source (700), followed by a step of bringing the first skin (100) thus heated into contact with the first face (310) of the cellular structure (300), and then a step of pressing the cellular structure (300) against the first skin (100).

Description

Description Title of the invention: Method for manufacturing a multicellular panel by conductive welding or by radiative welding Technical Field

[0001] The present invention relates to the general field of structures based on composite materials and thermoplastic polymers. More particularly, it relates to multicellular panels comprising composite materials and at least one thermoplastic polymer. Previous technique

[0002] Climate change is a major concern for numerous legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by different countries. In particular, an ambitious standard applies to both new types of aircraft and those already in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively contributing to the fight against climate change for several years now.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0004] The Applicant works in research and development on the weight reduction of devices, particularly through the materials used.

[0005] Multicellular panels made from thermoplastic composite materials are increasingly used in the aviation industry because they allow for parts with a lower overall mass than these The same parts, when made of metallic material, offer at least equivalent, if not superior, mechanical strength. Multicellular panels can be used, for example, in acoustic panels for engine nacelles, in inter-blade platforms, or in engine casings, etc.

[0006] In some prior art methods, multicellular panels are made by bonding or co-firing a honeycomb structure between two skins of a composite material. The honeycomb structure typically includes a honeycomb (NIDA) or cone-shaped structure.

[0007] Manufacturing by bonding or co-baking has the disadvantage of generating several defects in the multicellular panel.

[0008] During bonding, the adhesive can flow along the walls of the honeycomb structure, generating bubbles or forming menisci at the joints. Furthermore, the adhesive can seal openings in the honeycomb structure, which is particularly problematic when multicellular panels are used as acoustic panels.

[0009] Co-curing can cause marking of composite material skins. This phenomenon is known as "telegraphing." This manufacturing method can also lead to deformation of the honeycomb structure under the pressure of co-curing. Furthermore, co-curing involves heat treatment lasting several hours, making the process slow.

[0010] All these defects significantly reduce the mechanical and / or acoustic performance of multicellular panels.

[0011] Other manufacturing methods for multicellular panels include assembling the honeycomb structure to the skins by induction, resistance, or ultrasonic welding. However, these methods are not suitable for manufacturing such panels.

[0012] Induction welding and resistance welding involve the introduction of a metallic element at the interface between the honeycomb structure and the skins. This generates a significant increase in the final mass of the multicellular panel. Furthermore, the presence of the metallic element degrades the adhesion between the skins and the honeycomb structure.

[0013] Ultrasonic welding involves applying high forces to the assembly by the sonotrode and generally results in deformation of the cellular component. Description of the invention

[0014] The main purpose of the present invention is therefore to propose a solution for the manufacture of a multicellular panel which does not present the aforementioned disadvantages.

[0015] To this end, the invention proposes a method for manufacturing a multicellular panel comprising a honeycomb structure and a first skin made of a thermoplastic composite material. The honeycomb structure has a plurality of walls extending in a first direction between a first face and a second face of the honeycomb structure. The method comprises welding the first skin to the first face of the honeycomb structure. The method is characterized in that said welding comprises a step of heating the first skin via a radiative or resistive source, followed by a step of bringing the heated first skin into contact with the first face of the honeycomb structure, and then a step of pressing the honeycomb structure against the first skin.

[0016] This manufacturing process ensures a robust weld between the first skin and the honeycomb structure without increasing the overall size of the multicellular panel. Unlike resistance welding and induction welding, it eliminates the need for an element at the interface between the honeycomb structure and the skin. The presence of such an element makes the panel bulkier and can compromise the bond between the honeycomb structure and the first skin.

[0017] Thus, it is possible to obtain a multicellular panel with good mechanical properties, in particular thanks to the robustness of the bond between the first skin and the alveolar structure.

[0018] According to a particular feature, the process may further include, prior to welding, the placement of a thermoplastic film between the first skin and the alveolar structure.

[0019] The presence of such a film helps to improve adhesion between the first skin and the alveolar structure.

[0020] According to a particular feature, the process may further include an additional welding of a second skin of a thermoplastic composite material to the second face of the honeycomb structure, the second skin being heated via a radiative or resistive source.

[0021] This results in a multicellular panel with a sandwich structure in which the honeycomb structure is positioned between the first and second skins. Such a panel exhibits good mechanical properties due to the robust bonds between the skins and the honeycomb structure.

[0022] According to a particular characteristic, the first skin and / or the second skin can be heated via a radiative source, and the thermoplastic composite material of the first skin and / or the second skin can comprise a thermoplastic polymer loaded with carbon fibers or carbon black and selected from polyetherketoneketones, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, polyetherimides or a mixture thereof.

[0023] This type of material absorbs the waves emitted by the radiative source, thus maximizing heat absorption. This facilitates heating the first and / or second skin during the implementation of the process.

[0024] According to a particular feature, the process may further include, prior to additional welding, the placement of an additional thermoplastic film between the second skin and the alveolar structure.

[0025] The presence of such a film helps to improve adhesion between the second skin and the alveolar structure.

[0026] According to a particular feature, during additional welding, the second skin can be heated via a radiant source including an infrared lamp or a laser source.

[0027] Infrared lamps can simultaneously heat large areas up to 1 m² 2 Laser sources allow for localized heating of a surface and possess a high power density. The heating rate with a laser source is very high.

[0028] The choice between laser and infrared lamp will depend on the total surface area of ​​the room to be heated.

[0029] Depending on one particular feature, the first-layer heating stage can be carried out using a radiant source, such as an infrared lamp or a laser. Infrared lamps allow for the simultaneous heating of large areas up to 1 m². 2 Laser sources allow for localized heating of a surface and possess a high power density. The heating rate with a laser source is very high.

[0030] The choice between laser and infrared lamp will depend on the total surface area of ​​the room to be heated. Brief description of the drawings

[0031] [Fig. 1] Figure 1 illustrates the flowchart of the steps of a first embodiment of a process according to the invention,

[0032] [Fig. 2] Figure 2 schematically represents the process of Figure 1,

[0033] [Fig. 3] Figure 3 illustrates the flowchart of the steps of a second embodiment of a process according to the invention,

[0034] [Fig. 4] Figure 4 schematically represents the process of Figure 3. Description of the implementation methods

[0035] The invention applies generally to multicellular panels, in particular but not exclusively to multicellular panels having a sandwich structure.

[0036] Figures 1 and 2 illustrate a first example of an embodiment of the process according to the invention. The process comprises a first Cyl cycle, a second Cy2 cycle, and a 600 radiative source is used.

[0037] The 500 multicellular panel manufactured in this example comprises a first skin 100 of a thermoplastic composite material, a second skin 200 of a thermoplastic composite material and a honeycomb structure 300.

[0038] The first skin 100 comprises a first face 110 and a second face 120. The second skin 200 comprises a first face 210 and a second face 220.

[0039] The 500 multicellular panel also includes a first thermoplastic film 430 and a second thermoplastic film 460. The first thermoplastic film 430 has a first face 410 and a second face 420. The second thermoplastic film 460 has a first face 440 and a second face 450.

[0040] The alveolar structure 300 comprises a first face 310, a second face 320, a plurality of walls 330 and a plurality of orifices 340. The walls 330 extend along a first direction X between the first face 310 of the alveolar structure 300 and the second face 320 of the alveolar structure 300. The first and second faces 110, 120 of the first skin 100 extend perpendicularly to the first direction X.

[0041] According to one variant, the 300 alveolar structure may include a cone structure.

[0042] The honeycomb structure can be made with any type of material, including aluminum, thermoplastics, or Nomex® honeycomb from Hexcel®. The first and second faces 210, 220 of the second skin 200 extend perpendicularly to the first X direction.

[0043] In one embodiment, the first skin 100 or the second skin 200 can be perforated.

[0044] The first and second faces 410 and 420 of the first thermoplastic film 430 extend perpendicularly to the first direction X. The first and second faces 440 and 450 of the second thermoplastic film 460 extend perpendicularly to the first direction X.

[0045] We now describe an example of the implementation of the first cycle Cyl of the manufacturing process for a multicellular panel. In a first step El, the first face 410 of the first thermoplastic film 430 is placed on the first face 110 of the first skin 100.

[0046] The arrangement of the first thermoplastic film 430 improves the adhesion between the first face 310 of the alveolar structure 300 and the first skin 100.

[0047] The presence of the first thermoplastic film 430 does not limit the invention in any way. Nor is the presence of the step of disposing of the first thermoplastic film 430 limiting the invention.

[0048] In one embodiment, the multicellular panel 500 is devoid of the first thermoplastic film 430. In this case, the process is devoid of step El. In another embodiment, the first face 110 of the first skin 100 is covered with the first thermoplastic film 430 before the process is implemented.

[0049] According to a particular characteristic, the first thermoplastic film 430 comprises a material selected from polyetherketoneketones, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, polyetherimides or a mixture thereof.

[0050] Next the process is followed by a first conductive welding step E2. During the first conductive welding, a resistive source 700 is placed in contact with the second face 420 of the first thermoplastic film 430, as illustrated in figure 2a.

[0051] The resistive source 700 extends along the Z-axis between a first edge and a second edge. The resistive source 700 comprises fourteen resistors 730, seven of which are fixed to the first edge and seven to the second edge. Figure 2 shows the seven resistors 730 fixed to the first edge. During the first conductive welding, an electric current flows through the resistors 730, generating heat. This heats the resistive source 700. The number of resistors is not limited.

[0052] The hot resistive source 700 heats the first thermoplastic film 430 and the first skin 100. During heating, the first face 110 of the first skin 100 and the first thermoplastic film 430 melt. The second face 120 of the first skin 100 and the remainder of the first skin 100 do not melt.

[0053] During the first conductive E2 weld, the first skin 100 is heated to a temperature between 280°C and 400°C. This depends on the material or materials that make up the first skin.

[0054] Next, the process is followed by a withdrawal step E3 of the resistive source 700. This is followed by a first pressing step E4, during which the first face 310 of the honeycomb structure 300 is pressed against the second face 420 of the first thermoplastic film 430, as illustrated in Figure 2b. For this purpose, a contact pressure P is applied to the second face 320 of the honeycomb structure 300. This pressure is applied along the first direction X but in the opposite direction. The panel, having a first skin 100 and a honeycomb structure 300, is obtained at the end of the pressing step E4, as illustrated in Figure 2c.

[0055] The first pressing stage E4 is carried out at a predetermined temperature and continuously controlled to ensure controlled cooling of the first skin 100 and the honeycomb structure 300. In this case, the contact pressure is maintained until the complete cooling of the resulting panel.

[0056] When the multicellular panel 500 is devoid of the first thermoplastic film 430, the first face 310 of the honeycomb structure 300 is pressed against the first face 110 of the first skin 100 during the first pressing step E4.

[0057] The contact pressure P applied during the first pressing step E4 is between 0.05 MPa and 0.5 MPa. The choice of the contact pressure value depends on the density and constituents of the alveolar structure 300.

[0058] Steps E1 to E4 correspond to the first Cyl cycle of the process illustrated in figures 1 and 2.

[0059] We now describe an example of the implementation of the manufacturing process of a multicellular panel comprising a second Cy2 cycle in addition to the first Cyl cycle.

[0060] The process comprises the steps described above followed by the following steps. A step E5 involves placing a second thermoplastic film 460 onto the second face 320 of the honeycomb structure 300. The placement of a second thermoplastic film 460 improves the adhesion between the second face 320 of the honeycomb structure 300 and the second skin 200.

[0061] The presence of the second thermoplastic film 460 and the presence of step E5 are in no way limiting.

[0062] In another embodiment, the multicellular panel 500 is devoid of the second thermoplastic film 460. In this case, the process omits step E5. In yet another embodiment, the first face 210 of the second skin 200 is covered with the second thermoplastic film 460 before the implementation of the process according to the invention.

[0063] Next, the process is followed by a second conductive weld E6 during which the resistive source 700 is placed in contact with the first face 210 of the second skin 200, as illustrated in Figure 2d. During the second conductive weld, an electric current passes through the resistors 730, causing heat to be generated. Thus, the resistive source 700 is heated. The number of resistors is not limited.

[0064] The hot resistive source 700 heats the second skin 200. During heating, the first face 210 of the second skin 200 melts. The second face 220 of the second skin 200 and the rest of the second skin 200 do not melt.

[0065] The resistive source 700 used for the first conductive weld E2 can be used for the second conductive weld E6, as illustrated in Figure 2d. Using the same radiative source for both the first and second conductive welds is not a limitation. In one embodiment, the first conductive weld can be performed with a first resistive source and the second conductive weld with a second resistive source.

[0066] During the second conductive welding E6, the second skin 200 is heated to a temperature between 280°C and 400°C.

[0067] Next, the process is followed by a withdrawal step E7 of the resistive source 700. The process is followed by a second pressing step E8 during which the first face 210 of the second skin 200 is pressed against the second face 450 of the second thermoplastic film 460, as illustrated in Figure 2e. For this, a contact pressure P is applied to the second face 220 of the second skin 200. This pressure is applied along the first direction X but in the opposite direction.

[0068] The second pressing stage E8 can be carried out at a predetermined temperature and continuously controlled to ensure controlled cooling of the second skin 200 and the honeycomb structure 300. In this case, the contact pressure is maintained until the complete cooling of the resulting panel.

[0069] The contact pressure P applied during the second pressing stage E8 is between 0.05 MPa and 0.5 MPa.

[0070] Steps E5 to E8 correspond to the second cycle Cy2 of the process illustrated in figures 1 and 2. The 500 multicellular panel obtained in the second example is illustrated in figure 2f.

[0071] When the multicellular panel 500 is devoid of the second thermoplastic film 460, the first face 210 of the second skin 200 is pressed against the second face 320 of the alveolar structure 300 during the second pressing step E8.

[0072] The presence of the second cycle does not limit the invention. In one embodiment, the process may comprise only the first cycle. Such a process makes it possible to obtain a multicellular panel comprising a first skin and a honeycomb structure.

[0073] Figures 3 and 4 illustrate a second example of a method according to the invention. In this case, a radiative source 600 is used.

[0074] In the example illustrated in Figures 3 and 4, the process comprises the same steps E1, E4, E5, E8 as the process illustrated in Figures 1 and 2. In place of step E2, the process includes a step E20 during which the first weld is carried out via a radiative source 600. The radiative source 600 is arranged opposite the second face 420 of the first thermoplastic film 430, as illustrated in Figure 4a.

[0075] The radiative source 600 emits radiation 640 of a predefined wavelength. The first skin 100 comprises a thermoplastic composite material capable of absorbing the radiation emitted by the radiative source 600. This ensures optimal heating of the first face 110 of the first skin 100.

[0076] The first skin thermoplastic composite material 100 may comprise a thermoplastic polymer loaded with carbon fibers or carbon black and selected from polyetherketoneketones, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, polyetherimides or a mixture thereof.

[0077] When the first skin 100 is heated, the first face 110 of the first skin 100 and the first thermoplastic film 430 melt. The second face 120 of the first skin 100 and the rest of the first skin 100 do not melt.

[0078] In the example shown in Figure 4a, the radiative source 600 comprises four infrared lamps. The number of infrared lamps is in no way limiting. In one embodiment, the radiative source 600 may comprise a number of infrared lamps other than four.

[0079] The presence of infrared lamps is not limiting. In one embodiment, the radiative source 600 may comprise a laser source or a plurality of laser sources.

[0080] During the first E20 radiative welding, the first skin 100 is heated to a temperature between 280°C and 400°C.

[0081] Next, a removal step E30 of the radiative source 600 follows, followed by the first pressing step E4 described previously, as illustrated in Figure 4b. The panel having a first skin 100 and a honeycomb structure 300 obtained at the end of the pressing step E4 is illustrated in Figure 4c.

[0082] Steps E1, E20, E30 and E4 correspond to the first CylO cycle of the process illustrated in figures 3 and 4.

[0083] We now describe an example of the implementation of the manufacturing process of a multicellular panel comprising a second Cy20 cycle in addition to the first CylO cycle.

[0084] The process comprises the steps described above followed by the following steps. The pressing step E4 is followed by the laying step E5 of the second thermoplastic film 460 described above.

[0085] Next, the E5 positioning step is followed by a second radiative welding step E60, during which the radiative source 600 is positioned opposite the first face 210 of the second skin 200, as illustrated in Figure 4d. The radiative source 600 emits radiation 640 of a predefined wavelength, which heats the second skin 200. The wavelength of the radiation 640 can be between 0.7 pm and 25 pm.

[0086] The second skin 200 comprises a thermoplastic composite material capable of absorbing the radiation emitted by the radiative source 600. This ensures optimal heating of the first face 210 of the second skin 200.

[0087] According to a particular characteristic, the thermoplastic composite material of the second skin 200 may comprise a thermoplastic polymer loaded with carbon fibers or carbon black and selected from polyetherketoneketones, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, polyetherimides or a mixture thereof.

[0088] When the second skin 200 is heated, the first face 210 of the second skin 200 melts. The second face 220 of the second skin 200 and the rest of the second skin 200 do not melt.

[0089] The 600 radiant source used for the first radiant weld E20 can be used for the second radiant weld E60, as illustrated in Figure 4d. Using the same radiant source for both the first and second radiant welds E20 is not a limitation. In one embodiment, the first radiant weld E20 can be performed with one radiant source and the second radiant weld E60 with a second radiant source.

[0090] The radiant source 600 used for the second radiant weld E60 can include an infrared lamp or a laser source. In the example shown in Figure 4d, the second weld E60 is performed using a radiant source 600 comprising four infrared lamps 610. The number of infrared lamps is not limited.

[0091] During the second E60 radiative welding, the second skin 200 is heated to a temperature between 280°C and 400°C.

[0092] Next, the second radiative welding step E60 is followed by a removal step E70 of the radiative source 600, and then by a second pressing step E8 described previously.

[0093] Steps E5, E60, E70 and E8 correspond to the second Cy20 cycle of the process illustrated in figures 3 and 4. The 500 multicellular panel obtained in the second example is illustrated in figure 4f.

[0094] The presence of the second cycle does not limit the invention. In one embodiment, the process may comprise only the execution of the first cycle. Such a process makes it possible to obtain a multicellular panel comprising a first skin and an alveolar structure.

Claims

Demands

1. A method for manufacturing a multicellular panel (500) comprising a honeycomb structure (300) and a first skin (100) of a thermoplastic composite material, the first and second faces (110), (120) of which extend perpendicularly to the first direction X, the honeycomb structure (300) having a plurality of walls (330) extending along a first direction (X) between a first face (310) and a second face (320) of the honeycomb structure (300), the method comprising welding the first skin (100) to the first face (310) of the honeycomb structure (300), the method being characterized in that said welding comprises a step of heating the first skin via a radiative source (600) or a resistive source (700), followed by a step of bringing the first skin (100) thus heated into contact with the first face (310) of the alveolar structure (300),followed by a pressing step of the alveolar structure (300) against the first skin (100).

2. Method according to claim 1, further comprising, prior to welding, the disposition of a thermoplastic film (430) between the first skin (100) and the alveolar structure (300).

3. A method according to claim 1 or 2, further comprising additional welding of a second skin (200) of a thermoplastic composite material to the second face (320) of the honeycomb structure (300), the second skin (200) being heated via a radiative source (600) or a resistive source (700).

4. A method according to claim 3, wherein the first skin (100) and / or the second skin (200) is heated via a radiative source (600), and wherein the thermoplastic composite material of the first skin (100) and / or the second skin (200) comprises a thermoplastic polymer loaded with carbon fibers or carbon black and selected from polyetherketoneketones, polyetheretherketones, polyaryletherketones, polyphenylene sulfides, polyetherimides or a mixture thereof.

5. Method according to claim 3 or 4, further comprising, prior to additional welding, the disposition of an additional thermoplastic film (460) between the second skin (200) and the alveolar structure (300).

6. A method according to any one of claims 3 to 5, wherein during additional welding, the second skin (200) is heated via a radiative source (600) comprising an infrared lamp (610) or a laser source.

7. A method according to any one of claims 1 to 6, wherein the heating step of the first skin (100) is carried out via a radiative source (600) comprising an infrared lamp (610) or a laser source.

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