METHOD FOR MANUFACTURING AN ACOUSTIC SKIN MADE OF CERAMIC MATRIX COMPOSITE MATERIAL AND ROBOTIC SYSTEM FOR IMPLEMENTING SUCH A METHOD

Abstract

The invention relates to a method (100) for manufacturing a perforated acoustic skin made of ceramic matrix composite material, the method (100) comprising the following steps: - providing (110) a fibrous preform (10) comprising a stack (11) of plies (12) extending along a stacking axis (X) and made of fibers, - providing (120) a hollow rod (20), an insert (30) for the rod, and an insert guide device (40), the rod having a bore (21) for housing the insert and in which the insert can slide, - inserting (130) the rod into the fibrous preform along a stacking axis direction and, if necessary, inserting (136, 136') the insert into the rod, - extracting (140a) the insert from the rod and positioning (140b) the insert in the preform fibrous by means of the rod and the guiding device, - consolidate (150) the fibrous preform,and - eliminate (160) the insert from the consolidated fibrous preform so as to form at least one acoustic hole (15) in said consolidated fibrous preform. Figure for the abbreviation: Figure 3c,

Description

Title of the invention: METHOD FOR MANUFACTURED AN ACOUSTIC SKIN MADE OF CERAMIC MATRIX COMPOSITE MATERIAL AND ROBOTIC SYSTEM FOR IMPLEMENTING SUCH A METHOD Technical field of the invention

[0001] The invention relates to the technical field of manufacturing processes for acoustic skins made of ceramic matrix composite (CMC) material, particularly oxide-oxide ceramic matrix composite material. "Manufacturing" means any operation or series of operations aimed at producing, creating, or assembling such a skin made of ceramic matrix composite material.

[0002] The invention further relates to a robotic system for implementing such a manufacturing process. The robotic system makes it possible to implement the process according to the invention in an automated manner, even though the process according to the invention could be implemented, at least in part, manually. Technical background

[0003] The manufacture of an acoustic skin made of perforated ceramic matrix composite material traditionally involves a first step of supplying a fibrous preform comprising a stack of plies extending along a ply stacking axis, a second step of consolidating the fibrous preform, and a third step of mechanically drilling the consolidated fibrous preform to create holes in said consolidated fibrous preform. Although this method is very common for producing acoustic skins with holes ranging from 1 mm to several millimeters in diameter, with a surface openness percentage ranging from 5% to 25%, it requires the use of particularly expensive tooling, especially drill bits.

[0004] Another method for manufacturing an acoustic skin made of CMC material known in the prior art comprises a first step of supplying a fibrous preform comprising a stack of plies extending along a ply stacking axis, a second step of mechanically drilling the fibrous preform so as to form holes in said fibrous preform, and a third step of consolidating the fibrous preform. This method therefore differs from the preceding one in that the drilling is carried out before consolidation of the fibrous preform. In this configuration, the fibers constituting the fibrous preform are able to separate upon the insertion of a protruding solid element intended to form Holes are created in the acoustic skin. This protruding element can be a nail, a Z-pin, a spike, or even a fakir's mat. Other protruding elements can also be used for this purpose. Regardless of the solution chosen, in a fourth step, and therefore after the third step of consolidating the fibrous preform, the protruding element is removed from the consolidated fibrous preform, resulting in a perforated acoustic skin.

[0005] According to another technique also known from the prior art, in a first step at least one protruding element is positioned on a surface or a surface comprising at least one protruding element is provided. Then, in a second step, a plurality of fibrous material ribbons are draped over the surface comprising the protruding element(s) so that the fibers surround the protruding element(s) and the skin is directly formed with holes. The consolidation of the skin is then carried out in a subsequent step.

[0006] Document WO2017 / 017367 discloses the fabrication of a single-layer or double-layer acoustic attenuation panel made of CMC material. The acoustic panel has a double skin, the gap between which is formed by using a sacrificial material insert sandwiched between the two skins during panel fabrication. Each of the skins located on either side of the sacrificial material insert can be perforated by means of protruding elements formed in said insert. However, this document is silent on the manufacturing process of the skins.

[0007] The aforementioned prior art techniques require either the use of expensive tooling or lengthy material deposition steps, making them economically inefficient. Furthermore, some of the aforementioned techniques do not allow for the perforation of skins with rotationally symmetrical shapes, as is the case with techniques requiring a surface with protrusions. In this case, either the process is complicated by the implementation of several steps to create holes according to a predetermined spacing and distribution, or it is necessary to precisely adapt the shape of the surface and the arrangement of the protrusions to the skin to be produced. This implementation is also very costly since it requires adapting the surface and the position of the protruding elements to each acoustic skin configuration envisaged.

[0008] The invention aims to provide a method for manufacturing an acoustic skin made of CMC material that is simple to implement and requires inexpensive equipment. The invention also aims to provide a robotic system that overcomes the aforementioned shortcomings of the prior art, particularly with regard to the production of perforated acoustic skins of revolution. Summary of the invention

[0009] The invention proposes for this purpose a method for manufacturing a perforated acoustic skin made of ceramic matrix composite material, in particular for an aircraft turbomachine, the method comprising the following steps:

[0010] - provide a fibrous preform comprising a stack of plies extending along a stacking axis and made of fibers,

[0011] - provide at least one hollow rod, at least one insert for each rod and at least a guide device for the insert or each insert, the rod or rods having a bore to house the insert and in which the insert can slide,

[0012] - insert the rod or each rod into the fibrous preform along an axis direction stacking, and, when the insert is supplied separately from the stem, insert the insert into the stem,

[0013] - extract the insert or each insert from the corresponding rod and position the insert or each insert into the fibrous preform by means of the corresponding rod and guide device,

[0014] - consolidate the fibrous preform, and

[0015] - eliminate the insert or each insert from the consolidated fibrous preform so as to form at minus an acoustic hole in said consolidated fibrous preform.

[0016] The manufacturing process according to the invention overcomes the aforementioned drawbacks of the prior art. In fact, the perforation of the fibrous preform is carried out by means of at least one rod which, with the help of a guiding device, houses and positions at least one insert within the fibrous preform before its consolidation. Once the insert(s) have been placed in the fibrous preform, the preform is consolidated, which fixes its shape and thus stiffens the skin around the insert(s). The insert(s) are then removed after consolidation of the fibrous preform, leaving one or more perforations in said fibrous preform. The acoustic skin is therefore manufactured without drilling, and thus without the use of a drill bit. Furthermore, the manufacturing of the acoustic skin is simple because it does not require precise draping over a surface with protruding elements.On the contrary, the acoustic skin can be manufactured using a conventional process and then perforated by inserting at least one insert through the folds. In this respect, the process according to the invention is both simpler and less expensive than known processes.

[0017] According to various features of the invention which may be considered together or separately: - during the supply stage, a plurality of hollow rods connected to each other or supported by the same support are supplied; the rod or each rod includes a first end by which the rod or each rod is able to be inserted into the fibrous preform during the insertion step of the rod or each rod, the bore being cylindrical in shape and including, at the first end of the rod, a first end of cylindrical shape, beveled or flared; the insert(s) consists of a wire with a diameter between 0.3 mm and 1.8 mm, the insert(s) is stored in the form of a spool; each insert being made up of a plurality of segments; the insert or each insert is solid and capable of passing from a solid state to a liquid or gaseous state, in particular during the step of removing the insert or each insert from the fibrous preform; the step of removing the insert or each insert is implemented by melting, dissolving or sublimation; the insert is made of a material chosen from materials with a melting point between 80°C and 650°C such as metals or alloys based on zinc, tin, lead, magnesium, aluminium, or thermosetting or water-soluble polymers such as polyvinyl acetate (PVA), polypropylene (PP), acrylonitrile butadiene styrene (ABS); the process includes, prior to the step of inserting the rod or each rod into the fibrous preform, a step consisting of inserting an insert into the bore of the rod or each rod; the process includes, between the step of supplying the rod or each rod and the step of inserting the rod or each rod into the fibrous preform, a step consisting of inserting an insert into the bore of the rod or each rod; the process includes, during the step of inserting the rod or each rod into the fibrous preform, a substep consisting of inserting an insert into the bore of the rod or each rod; the insert or each insert is liquid, viscous or gelatinous, the process further comprising, between the step of inserting the rod or each rod into the fibrous preform and the step of extracting the insert or each insert, a step consisting of injecting the insert or each insert into the bore; the rod is heated, the insert being kept in a liquid or viscous state by the rod, the process comprising, concurrently with the step of extraction and positioning of the insert or each insert, a step consisting of allowing the insert or each insert to cool; The insert(s) is made of a thermoplastic material, for example chosen from polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), or a material gelatinous selected from silicone, filled silicone, a silica-filled thermosetting resin and a thixotropic thermosetting resin; - where each rod is made of steel; - the fibrous preform is made of ceramic fibers, and furthermore pre impregnated with a ceramic matrix, the fibers and the matrix being, for example, based on aluminum oxide; - the rod has a dimension, along the stacking X axis, which is between 5 mm and 100 mm; - the insert has a dimension, along the stacking X axis, which is between 0.5 mm and 10 mm; - the skin has a thickness between 0.5 mm and 5 mm; - the fiber plies are impregnated between the extraction stage of the insert or each insert of the associated stem and the consolidation stage of the fibrous preform; - the fibre plies are impregnated before the insert extraction stage; - the insert guide device or each insert guide device comprises two rollers capable of rotating, the two rollers being capable, by rotating, of generating a force in the opposite direction to the direction of movement of the rod or each rod during the extraction step; - the insert guide device or each insert guide device includes two pads capable of pinching the insert or each insert laterally; - the insert guide device or each insert guide device consists of a guide rod capable of guiding the insert or each insert along a stacking axis direction in the opposite direction to that of rod extraction during the rod extraction step concerned.

[0018] The invention further relates to a robotic system for implementing the process as described above, the robotic system comprising:

[0019] - a body comprising an upper portion capable of rotating around an axis longitudinal,

[0020] - an articulated arm having a first end connected to the upper portion of the a body capable of rotating around a joint axis, and a second end,

[0021] - a tool holder comprising at least one compartment capable of housing at least one rod, the tool holder being connected to the second end of the articulated arm,

[0022] - a feed conduit intended to fill the rod or each rod of an insert, said feed conduit having a first end connected to the tool holder and a second end connected to at least one insert holder.

[0023] The robotic system according to the invention makes it possible to implement the process of manufacturing a perforated CMC material skin in an automated manner. The upper portion of the body allows the articulated arm to move around the longitudinal axis A, and the articulated arm is simultaneously capable of rotating around a pivot axis. The articulated arm allows the tool holder and the distributor to move simultaneously, enabling it to perform vertical movements as well as movements in the plane perpendicular to the longitudinal axis A. Incidentally, this allows it to perform the perforation of acoustic skin exhibiting rotational symmetries. Since the distributor is connected to the tool holder, it allows the continuous feeding of an insert from the insert holder to the tool holder rod(s).

[0024] According to an advantageous embodiment, the inserts are in the form of coils.

[0025] According to another advantageous embodiment, the robotic system further comprises a device for guiding the insert or each insert.

[0026] Preferably, the tool holder includes at least one second compartment suitable for housing the or each guiding device. Brief description of the figures

[0027] Other objects, features and advantages of the invention will become more apparent in the following description, made with reference to the accompanying figures, in which:

[0028] - Fig. 1 schematically illustrates a process for manufacturing a skin acoustics in CMC material according to a general embodiment of the present invention;

[0029] - Figure 2 schematically illustrates a process for manufacturing a skin acoustics in CMC material according to particular implementations of the process according to the present invention;

[0030] - Figure [Fig. 3a] schematically illustrates the positioning of a rod relative to a fibrous preform according to a first variant of the embodiment of the process according to the invention;

[0031] - Figure 3b schematically illustrates the positioning of a rod relative to a fibrous preform according to a first variant of the embodiment of the process according to the invention;

[0032] - Figure 3c schematically illustrates the positioning of a rod relative to a fibrous preform according to a first variant of the embodiment of the process according to the invention;

[0033] - Figure 3d schematically illustrates the positioning of a rod relative to a fibrous preform according to a first variant of the embodiment of the process according to the invention;

[0034] - Figure 4a schematically illustrates the positioning of a rod relative to a fibrous preform according to a second embodiment of the process according to the invention;

[0035] - Figure 4b schematically illustrates the positioning of a rod relative to a fibrous preform according to a second embodiment of the process according to the invention;

[0036] - Figure 4c schematically illustrates the positioning of a rod relative to a fibrous preform according to a second embodiment of the process according to the invention;

[0037] - Figure 4d schematically illustrates the positioning of a rod relative to a fibrous preform according to a second embodiment of the process according to the invention;

[0038] - Figure 5 schematically illustrates the extraction step according to a first variant of the process according to the invention;

[0039] - Figure 6 schematically illustrates the extraction step according to a second variant of the process according to the invention;

[0040] - Figure 7 schematically illustrates the extraction step according to a third variant of the process according to the invention;

[0041] - Figure 8 schematically illustrates two particular implementations of the step extraction illustrated in [Fig.7];

[0042] - Figure 9 schematically illustrates the first extremities according to different configurations in the implementation of the rod used in the process according to the invention;

[0043] - Figure 10 schematically illustrates an example of a robotic system for the installation implementation of the process according to the invention.

[0044] In the figures illustrated, optional steps are indicated by rectangles in dotted lines. Detailed description of the invention

[0045] With reference to figures 1 and 2, the invention relates to a method 100 for manufacturing an acoustic skin made of ceramic matrix composite (CMC) material, in particular for an aircraft turbomachine.

[0046] As indicated in the introduction to this description, although the invention applies to all CMC materials, it is particularly suited to oxide-oxide CMC materials, commonly known by the abbreviation COX. COX materials are a specific type of ceramic matrix composite material. The materials COX typically comprises a fiber fabric or fiber ply impregnated with a matrix, also oxide-based, used in conjunction with a solution, in which the matrix and solution together form what is known as the impregnation material. The fiber fabric or, as the case may be, the fiber ply, conventionally forms what is called the reinforcement of the composite material.

[0047] Reducing the weight of turbomachinery is a constant research topic for aeronautical professionals because it reduces aircraft fuel consumption. In the context of this invention, the manufactured acoustic skin is more particularly an acoustic skin for aircraft turbomachinery. Acoustic skins made with COX materials differ from skins made with CMC materials in their increased lightness, good temperature resistance at high operating temperatures, and low cost.

[0048] With reference to [Fig.1] and Figures 3a to 3d, the method 100 for manufacturing an acoustic skin according to the invention includes a first step 110 of supplying a fibrous preform 10 comprising a stack 11 of plies 12 extending along a stacking X axis and made up of fibers.

[0049] The fibrous preform 10 intended to form the acoustic skin to be manufactured is conventionally produced by cutting so as to have the shape of this acoustic skin. Its shape and dimensions are therefore likely to change slightly during the subsequent stages of the manufacturing process 100, in particular before it is consolidated.

[0050] According to a particular embodiment, the fiber plies 12 forming the stack are pre-impregnated with a ceramic matrix; that is, the impregnation of the fibers constituting the plies 12 is carried out prior to the step 110 of supplying the fibrous preform 10. The impregnation of the fibers constituting the plies 12 can be carried out after the step 110 of supplying the fibrous preform. We will return to this point later in the description. In the case of a fibrous preform 10 made of COX material, the fibers and the ceramic matrix can be based on aluminum oxide (Al₂O₃). Aluminum oxide fibers are not only electrically insulating but also very chemically stable, which gives them excellent corrosion resistance. Aluminosilicate fibers are also excellent candidates for producing fiber plies 12.

[0051] According to one embodiment, the fiber plies 12 forming the stack 11 are not impregnated with a ceramic matrix. The fiber plies 12 are therefore dry, as opposed to the case where they are pre-impregnated with a ceramic matrix. According to another embodiment, the fiber plies 12 are pre-impregnated with a temporary binder, that is, a binder capable of decomposing almost completely into Other components may be affected under certain conditions, such as temperature and / or pressure. It is also possible to combine these embodiments, namely when the 12 fiber plies are bare and pre-impregnated with the temporary binder.

[0052] In either case, i.e. whether the fiber plies 12 are dry and / or pre-impregnated with a ceramic matrix or temporary binder, it should be emphasized that the fiber plies 12 can be in the form of a woven (2D, single layer, 3D multi-layered interlocking) or even a braided, as well as in the form of a non-woven (unidirectional sheets, multi-axial sheets, non-wovens - veils or mats) or a combination of all or part of these forms.

[0053] As previously stated, the stack 11 extends along the stack X axis. This means that the thickness of the stack, namely its smallest dimension, is defined along the stack X axis, the latter extending orthogonally to a transverse axis Y and an extension axis Z.

[0054] The method 100 for manufacturing an acoustic skin according to the invention comprises a step 120 of supplying at least one hollow rod 20, at least one insert 30 for each rod 20, and a guide device 40 for the insert or each insert 30. This step 120 of supplying the rod 20, the insert 30, and the guide device 40 for the insert(s) can be carried out before, after, or concurrently with step 110 of supplying the fibrous preform 10. In the embodiments illustrated in the figures, the rod 20 has a generally cylindrical shape. However, the rod 20 can have a different general shape with regard to the manufacturing method 100 according to the present invention. With regard to the insert 30, in general, it should be noted that the shape of the insert 30 corresponds to the shape of the acoustic hole 15 that we wish to make in the fibrous preform 10.

[0055] As can be seen more clearly in the cross-sectional view of Figures 3a, 3b, 3c, and 3d, and in particular [Fig. 3c], the rod 20 has a bore 21 to accommodate the insert 30. In the illustrated embodiment, the bore 21 has a cylindrical shape fitted to the shape and dimensions of the insert 30, which is itself cylindrical. The insert 30 is able to slide along the bore 21. In this respect, the rod 20 may include a first end 22 and a second end 23 in which openings are formed, the edges of which form guides for the insert 30, the first end 22 being the first end of the rod 20 through which it is inserted into the fibrous preform 10.

[0056] By way of non-limiting examples, the first end 22 of the rod 20 may be frustoconical or bevelled. Like the first end 22 of the rod 20, the bore 21 may include a first end 21a, located at the first end 22 of the rod, which has a completely different shape than that illustrated. on figures 3a-3d (as well as figures 4a-4d which will be described later). The shape of the bore 21, including its end, depends on the shape of the insert 30 which is intended to be housed in it.

[0057] Figure 9 illustrates, on the left, a rod 20 in which the first end 22 of the rod and the first end 21a of the bore are beveled. In this configuration, the rod 21 is therefore pointed at the first end 22. Figure 9 illustrates, in the center, a rod 20 in which the first end 22 of the rod is frustoconical and the first end 21a of the bore is cylindrical. Figure 9 illustrates, on the right, a rod 20 in which the first end 22 of the rod is cylindrical and the first end 21a of the bore is flared. Other combinations of shapes can be envisaged for the first end 21a of the bore 21 and the first end 22 of the rod 20 by a person skilled in the art in compliance with the inventive concept underlying the present invention.

[0058] According to a particular embodiment, the rod 20 has a dimension, along the stacking X axis, which is between 5 mm and 100 mm while the insert has a dimension, along the stacking X axis, which is between 0.5 mm and 10 mm.

[0059] The manufacturing process 100 further includes an insertion step 130 of the rod(s) 20 into the fibrous preform 10 along a stacking X-axis direction. Thus, the rod(s) 20 move in a direction orthogonal to the "large" faces of the fibrous preform 10, that is, the faces extending orthogonally to the stacking X-axis. It is advantageous for the rod(s) 20 to be made of steel. Indeed, a steel rod 20 is better able to pass through the stack 11, even when the stack thickness 11 becomes high, namely up to 5 mm. Furthermore, it is possible to use a material with properties that facilitate the removal of the rod(s) 20 after the consolidation of the fibrous preform 10, either by temperature, by dissolution (water and / or solvent), or by sublimation. Materials meeting this criterion are described in the description relating to step 130.

[0060] In this regard, the thickness of the fibrous preform 10 is advantageously between 0.5 pm and 5 mm, which makes it possible to obtain an acoustic skin of substantially identical thickness.

[0061] This step 130 of inserting the rod(s) 20 into the fibrous preform 10 may advantageously include an approach substep 132, as illustrated in [Fig. 3a], during which the rod 20 is positioned opposite the predetermined location where an acoustic hole 15 is to be made, and a second substep 134, as illustrated in [Fig. 3b], during which the rod(s) 20 are inserted into the fibrous preform 10 along a stacking X-axis direction. The approach substep 132 allows for alignment of the rod(s) 20 with the preform 10. each location where an acoustic hole is to be made 15. This sub-step 132 is particularly useful when precise positioning of the acoustic hole is required, however it is not mandatory.

[0062] According to a particular embodiment, during step 120 of supplying the hollow rod(s) 20 and the insert(s) 30, the rod(s) 20 may be provided with an integrated insert 30, i.e., the rod(s) 20 and the associated insert(s) 30 are in the form of an assembly. The insert(s) 30 may be inserted into the corresponding rod(s) 20 during a step 115 of inserting an insert 30 into the bore 21 of the rod(s) 20. This particular embodiment is especially suitable when the insert 30 is in solid form.

[0063] The insert or each solid insert 30 is advantageously made of a material selected from materials with a melting point between 80°C and 650°C, such as metals or alloys based on zinc, tin, lead, magnesium, aluminum, or thermosetting or water-soluble polymers such as polyvinyl acetate (PVA), polypropylene (PP), or acrylonitrile butadiene styrene (ABS). A PVA insert 30 is a thermoplastic insert that is both solid at room temperature and water-soluble, i.e., capable of dissolving in water. A PP or ABS insert 30 is a thermoplastic insert that is both solid at room temperature and capable of melting when subjected to a temperature equal to or greater than its melting point. These inserts 30 all have the advantage of being fusible under the conditions stated above.Other insert materials capable of transitioning from a solid to a gaseous state may be considered within the scope of the present invention, in accordance with the inventive concept underlying the invention.

[0064] According to another embodiment, the insert or each solid insert 30 can be supplied separately from the or each associated rod 20. In this case, according to a first embodiment, between the supply step 120 of the rod(s) 20 and the insertion step 130 of the rod(s) 20 into the fibrous preform 10, the solid insert 30 is inserted into the rod(s) 20. According to a second embodiment, during a substep of the insertion step 130 of the rod(s) 20 into the fibrous preform 10, the solid insert 30 is inserted into the rod(s) 20. This substep of inserting the solid insert 30 into the rod(s) 20 is advantageously carried out after the rod(s) 20 have been inserted into the fibrous preform 10 along a stacking X-axis direction. These different embodiments are illustrated in [Fig. 2].

[0065] According to another particular embodiment, the insert 30 is in gelatinous, viscous or liquid form. During a substep of the insertion step 130 of the rod 20 into the fibrous preform 10, the gelatinous, viscous insert 30 is inserted 136' or liquid in the rod(s) 20. This substep 136' of inserting the insert 30 into the rod(s) 20 is advantageously implemented after insertion 130, 134 of the rod(s) 20 into the fibrous preform 10 along a stacking X-axis direction. This allows control of any potential flow of the insert 30 out of the bore(s) 21 and allows the insert 30 to potentially stiffen. Indeed, in a particular embodiment, the rod(s) 20 is a heated rod 20 capable of maintaining the insert 30 in a viscous or liquid state. This is described in more detail later.

[0066] In this particular embodiment, the insert or inserts 30 may advantageously be made of a thermoplastic material, selected from polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polyvinyl chloride (PVC), or of a gelatinous material selected from silicone, filled silicone, a silica-filled thermosetting resin, and a thixotropic thermosetting resin. As previously stated, a PP insert 30 is a thermoplastic insert that is solid at room temperature. However, according to a particular embodiment in which the rod or rods 20 are heated, the insert 30 becomes liquid or viscous in the rod or rods 20 and is then able to solidify once it has cooled, in particular outside the rod or rods 20. The same applies to a PE insert 30.A 30 insert made of silicone or filled silicone, of silica-filled thermosetting resin or of thixotropic thermosetting resin becomes gelatinous when heated, then is able to solidify once it has cooled, particularly outside of the or each rod 20.

[0067] With reference to [Fig. 1], the manufacturing process 100 further comprises a step 140a of extracting the insert or each insert 30 from the corresponding rod 20, and of positioning 140b of the insert or each insert 30 in the fibrous preform 10 by means of the corresponding rod 20 and guide device 40, i.e., associated with this / these insert(s). In other words, the extraction 140a of the insert or each insert 30 from the associated rod 20 is carried out by positioning the insert or each insert 30 in the fibrous preform 10 by means of the corresponding rod 20 and guide device 40. The extraction 140a of the insert or each insert 30 from the associated rod 20 is therefore concomitant with the positioning 140b of the insert or each insert 30 in the fibrous preform 10 by means of the or each rod 20. An example of the implementation of this extraction step 140a and positioning 140b is illustrated in [Fig.3c].During extraction 140a, while the insert or each insert 30 is positioned in the fibrous preform 10, the rod or rods 20 undergo a movement opposite to that which occurred during the insertion step 130 in the fibrous preform 10. Thus, the rod or rods 20 are withdrawn from the fibrous preform 10 in a direction substantially parallel to the stacking X-axis direction. The extraction step 140a of the rod 20 and the concomitant positioning step. 140b of the insert 30 is only completed when the rod or rods 20 are completely disengaged from the associated insert 30.

[0068] Depending on the material of which the insert or each insert 30 is made, the extraction 140a produces different consequences on the rigidity of the insert or each insert 30. When the insert or each insert 30 is already in a solid state in the rod 20 without heating the rod 20, the insert or each insert 30 retains its initial rigidity. When the insert or each insert 30 is liquid or viscous due to heating the rod 20, the insert changes from a liquid or viscous state to a solid state as the insert or each insert 30 is extracted from the associated rod 20. In practice, when the insert or each insert 30 has been kept in a liquid or viscous state by the rod 20 in the steps preceding the extraction step 140a, the process 100 includes, concurrently with the extraction step 140a and positioning 140b of the insert or each insert 30, a step consisting of allowing the insert or each insert 30 to cool 145 ([Fig.2]).Cooling occurs naturally when the insert or each insert 30 is no longer in the associated rod 20. Cooling 145 can be accelerated by various means known to those skilled in the art.

[0069] As previously stated, the supply step 120 also aims to provide a guide device 40 for the insert or each insert 30. The guide device 40 allows the insert or each insert 30 to be extracted from the rod 20, while allowing the insert or each insert 30 to remain in the fibrous preform 10. In this respect, the guide device 40 may advantageously guide the insert or each insert 30 along a stacking X-axis direction in the opposite direction to that of the extraction of the rod 20. The guide device 40 may also only exert pressure on the insert or each insert 30 to hold it in a fixed position, so that when the rod or each rod 20 is extracted 140a and the insert or each insert 30 is positioned 140b, the latter remains immobilized in the preform fibrous 10. The guidance device 40 can be supplied with the robotic system 200 which will be described in detail later or separately.We'll come back to that.

[0070] Figures 5 to 8 schematically illustrate the extraction step 140a of the rod(s) 20 and the positioning 140b of the insert(s) 30 by means of various guiding devices 40. It should be noted that while only one rod 20 and one insert 30 are shown, there may be several rods 20 and an insert 30 associated with each rod 20. This is also the case for Figures 3a to 3d, 4a to 4d, and 6 to 8. There may also be one guiding device 40 for each insert 30.

[0071] In the example illustrated in [Fig. 5], the guide device or each guide device 40 comprises two rotatable rollers which, by rotating, generate a force in the opposite direction to the direction of movement of the rod or each rod 20 when the latter (these) are in extraction course 140a. This allows the insert or each insert 30 to be kept in the fibrous preform 10 even if the rod or each rod 20 follows an opposite movement.

[0072] In the example illustrated in [Fig. 6], the guiding device or devices 40 comprise two pads adapted to grip the insert or each insert 30. Each pad exerts pressure on the associated insert 30 to hold it in a fixed position, and thus immobilize it in the fibrous preform 10 during the extraction 140a of the relevant rod 20. The pressure exerted by the pads on the insert 30 is preferably applied to two diametrically opposite points on the insert 30, which stabilizes the insert 30 during the gripping. Thus, in practice, the pressure is exerted laterally, i.e., along a transverse axis Y and / or an extension axis Z.

[0073] In the example illustrated in [Fig. 7], the guiding device or devices 40 consists of a guide rod whose function is to guide the insert or each insert 30 along a stacking X-axis direction in the opposite direction to the extraction direction of the rod 20 during the extraction 140a of the relevant rod 20. As in other embodiments, the guide rod makes it possible to maintain the insert or each insert 30 in the fibrous preform 10 even if the rod or each rod 20 follows a reverse movement. This embodiment differs somewhat from the two previous ones, because the guide rod can perform a translation along the stacking X-axis. This embodiment is particularly advantageous when the insert or each insert 30 is initially in liquid or gelatinous form.In this regard, the guide device or each 40 can then consist of a device for pressurizing the insert or each insert 30 in the rod 20, this pressurizing device being activated during the extraction 140a of the rod 20.

[0074] With further reference to [Fig. 1], the manufacturing process 100 includes a consolidation step 150 of the fibrous preform 10. Consolidation hardens the fibrous preform 10, improves its strength, and thus makes it easier to handle. This consolidation step 150 can be carried out in a suitable curing device, for example, an oven or an autoclave. If a temporary binder has been used in the fiber plies 12, it can be dissolved during this curing by using a curing temperature higher than the degradation temperature of said temporary binder. However, the temporary binder can be degraded by other means, for example, using water if it is water-soluble.

[0075] Alternatively, consolidation 150 can, for example, be achieved by hardening the binder, for example in the case of a temporary binder from the thermosetting polymer family. Alternatively still, consolidation can be achieved by dehydrating the temporary binder, in the case of a binder that is partially or totally water-soluble, for example in the case of a temporary binder of polyvinyl acetate or polyvinyl alcohol fibers. Any other method for making solid the fibrous preform 10 and its connection with the inserts 30, provided that it does not destroy the inserts 30 to the point of modifying the fiber spacing achieved by the inserts 30. At the end of the consolidation step 150, a consolidated fibrous preform is obtained.

[0076] At this stage, it should be noted that the impregnation of the fiber plies 12 can only be carried out between step 140a of extracting the insert or each insert 30 from the associated stem 20 and step 150 of consolidating the fibrous preform 10. This particular implementation allows for better distribution of the ceramic matrix, or where applicable, the temporary binder, to the geometry of the fibrous preform 10. In this respect, it is advantageous for the fibrous preform 10 to contain a sufficient quantity of binder so that the fibrous preform 10 holds together and is able to retain the insert(s) 30 when they are positioned 140b. The impregnation can also be carried out in a subsequent step, for example, in the form of grains diluted in an aqueous liquid and containing dehydrating agents.It can also be implemented between the insertion step 130 of the rod 20 into the fibrous preform and the extraction step 140a of the insert or each insert 30 from the associated rod 20.

[0077] Furthermore, the manufacturing process 100 includes a step 160 of removing the insert 30 or each insert 30 from the fibrous preform so as to form at least one acoustic hole 15 in said consolidated fibrous preform. The insert or each insert 30 is therefore sacrificial. Indeed, the insert or each insert 30 is intended to be removed at the end of the manufacturing process 100 for the acoustic skin. Thus, the insert or each insert 30 is suitable for removal. It can be removed by melting or sublimation (thermal method) or by dissolution (liquid method). Since an insert 30 can only be used for the manufacture of a single acoustic skin, it is therefore for single use only.

[0078] Following the removal step 160 of the insert or each insert 30, a perforated acoustic skin is obtained without drilling, as illustrated in [Fig. 3d]. The perforation of the fibrous preform 10 is carried out by means of the rod or each rod 20, the latter serving to house and deposit the insert or each insert 30 into the fibrous preform 10 before consolidation of said fibrous preform 10. Once the insert or each insert 30 has been deposited into the fibrous preform 10, the latter is consolidated, which fixes its shape and thus stiffens the acoustic skin around the insert or each insert. The insert(s) is / are then removed after consolidation 150 of the fibrous preform, which creates one or more acoustic holes 15 in said consolidated fibrous preform.

[0079] The manufacturing of the acoustic skin is therefore carried out without drilling, and thus without the use of a drill bit. Furthermore, the manufacturing of the acoustic skin is simple because it does not require precise draping over a surface with protruding element(s). On the contrary, the acoustic skin can be manufactured using a process conventional then perforated by inserting at least one insert 30 through the plies 12 of fibers. In this respect, the manufacturing process 100 according to the invention is both simpler and less expensive than known processes.

[0080] That being said, the insert or each insert 30 can be made of a recyclable thermoplastic material. Indeed, when an insert 30 is made of such a thermoplastic material, it can be thermally dissolved, and thus melted, and then used to manufacture a new acoustic skin. This melting and recycling process can be repeated many times, making the use of a thermoplastic insert 30 inexpensive.

[0081] Thus, the use of a more efficient process according to this particular embodiment of the invention is also advantageous for reducing the applicant's environmental footprint. Indeed, it makes it possible to increase and optimize manufacturing, production, and / or repair capacity and, consequently, to significantly reduce associated greenhouse gas emissions. This optimization also makes it possible to decrease raw material consumption. It makes it possible to significantly decrease the number of discarded inserts that may be difficult to recycle. Furthermore, the solution also has the advantage of reducing its energy input (water, electricity, etc.) and / or the use of any chemicals that contravene environmental standards and regulations in force. In the embodiment illustrated in Figures 4a, 4b, 4c, and 4d, the acoustic skin comprises a plurality of acoustic holes.

[0082] The process is similar to that described previously, except for the number of rods 20 and inserts 30 used. In this case, during step 120, a plurality of hollow rods 20 are provided, connected to one another or supported by the same support. Each rod 20 advantageously includes an insert 30. The spacing between the rods 20 depends on the desired perforation rate. Indeed, the spacing between the rods 30 influences the spacing between the inserts 30, and subsequently, in the acoustic skin produced, the spacing between the acoustic holes.

[0083] According to a preferred embodiment, the insert or inserts 30 consist of a wire having a diameter between 0.3 mm and 1.8 mm, the insert or inserts 30 being stored in the form of a spool. This allows, when the insert or inserts 30 are in wire form, for faster supply of the insert or inserts 30. The wire can be of any geometric shape, i.e., round, oval, square, etc.

[0084] According to this preferred embodiment, the insert or each insert 30 can be continuous. In this case, the wire is cut at each extraction step 140a of the rod or each rod 20 by a cutting device (not illustrated) which cuts the insert or each insert 30 between the top of the fibrous preform 10 and the end of the rod 20 emerging from the fibrous preform 10, namely the first end 22 of the rod. This alternative design allows for flexibility in the desired dimensions for the insert or each insert 30.

[0085] Alternatively, the insert or inserts 30 are discontinuous within the rod or rods 20. This embodiment is shown, for example, in Figures 5, 6, and 7, as well as in [Fig. 8] (right). The insert or inserts 30 are then cut before or after insertion into the rod 20. It is advantageous to cut the insert or inserts 30 before insertion into the associated rod 20 because this simplifies the implantation of the inserts by avoiding the need for a cutting device near the first end 22 of the rod 20—the end through which the rod 20 is first inserted into the fibrous preform 10 and through which the associated insert 30 is extracted during the extraction step 140a. Preferably, the insert or inserts 30 are then cut to the same length, preferably greater than or equal to the thickness of the fibrous preform 10.Alternatively, the insert or each insert 30 is cut to a length less than the maximum thickness of the preform, or less than or equal to the minimum thickness. The insert or each insert 30 then consists of a plurality of segments. In this configuration, a plurality of inserts 30 can be stacked along the stacking X-axis in the rod 20, allowing them to be extracted as needed. This embodiment reduces the manufacturing process time 100. The length of each insert 30 depends on the thickness of the stack 11 in which the acoustic hole(s) are to be made.

[0086] In this regard, the invention further relates to a robotic system 200 for the implementation of the process as previously described.

[0087] With reference to [Fig. 10], the robotic system 200 comprises a body 210 having an upper portion 211 capable of rotating around a longitudinal axis A. The body 210 is, in contrast to the articulated arm which will be introduced later, advantageously fixed.

[0088] The robotic system 200 further comprises an articulated arm 215 having a first end 216 connected to the upper portion 211 of the body and capable of rotating about a pivot axis B, and a second end 217. The articulated arm 215 is preferably equipped with its own motor, enabling it to generate forces. The end of the articulated arm connected to the body 210, namely the first end 216, can rotate about the pivot axis B because the body 210 is fixed. The other end of the articulated arm 215, namely the second end 217, is connected to a tool holder 220.

[0089] The robotic system 200 includes the tool holder 220. The latter is equipped with at least one compartment 221 capable of holding at least one rod 20. The rod 20 is fed with an insert 30 by means of a feed conduit 230 designed to fill the rod(s) 20 with an insert 30. The feed conduit 230 has a first end 231 connected to the tool holder 220 and a second end 232 connected to at least one insert holder 240. In practice, the insert holder 240 is in the form of a coil as described in the preceding description.

[0090] At this stage, it should be specified that the robotic system 200 may also include the insert guide device 40, or guide device for each insert 30 mentioned previously. It may include a guide device 40 associated with each insert 30 and therefore have as many guide devices 40 as there are inserts 30 to be introduced into the fibrous preform 10.

[0091] In this respect, the tool holder 220 may further include a second (non-visible) compartment suitable for housing the guide device(s) 40. The second compartment then has dimensions and a shape adapted to receive the guide device(s) 40. It should be noted that the guide device 40 could also be housed in the compartment 221 containing the rod(s) 20.

[0092] According to another embodiment, the guidance device(s) 40 can, although belonging to the robotic system 200, be offset from the tool holder 220.

[0093] According to yet another embodiment, the guidance device(s) 40 can be supplied separately from the robotic system 200, i.e. they do not belong to the robotic system 200, and can therefore be sold separately.

[0094] This robotic system 200 is therefore particularly suited to the implementation of the process 100 of manufacturing an acoustic skin when the insert or each insert 30 consists of a wire and is stored in the form of a reel.

[0095] The configurations shown in the cited figures are only possible examples, by no means limiting, of the invention which on the contrary encompasses the variants of designs within the reach of the person skilled in the art.

Claims

Demands

1. A method (100) for manufacturing a perforated acoustic skin of ceramic matrix composite material, particularly for an aircraft turbomachine, the method (100) comprising the following steps: - providing (110) a fibrous preform (10) comprising a stack (11) of plies (12) extending along a stacking axis (X) and made of fibers, - providing (120) at least one hollow rod (20), at least one insert (30) for each rod (20) and at least one insert guide device (40) for each insert (30), the rod or each rod (20) having a bore (21) for housing the insert (30) and in which the insert (30) can slide, - inserting (130) the rod or each rod (20) into the fibrous preform (10) along a stacking axis (X) direction and, when The insert (30) is supplied separately from the rod (20), insert (136, 136') the insert (30) into the rod (20),- extract (140a) the insert(s) (30) from the corresponding rod (20) and position (140b) the insert(s) (30) in the fibrous preform (10) by means of the corresponding rod (20) and guide device (40), - consolidate (150) the fibrous preform (10), and - remove (160) the insert(s) (30) from the consolidated fibrous preform so as to form at least one acoustic hole (15) in said consolidated fibrous preform.

2. A manufacturing method (100) according to claim 1, wherein, in step (120), a plurality of hollow rods (20) connected to each other or carried by the same support are provided.

3. A method (100) of manufacturing according to any one of claims 1 or 2, wherein the rod or each rod (20) comprises a first end (22) by which the rod or each rod (20) is able to be inserted into the fibrous preform (10) during the step (130) of inserting the rod or each rod (20), the bore (21) being cylindrical in shape and comprising, at the first end (22) of the rod, a first end (21a) of cylindrical, beveled or flared shape.

4. A method (100) of manufacturing according to any one of claims 1 to 3, wherein the insert or each insert (30) consists of a wire having a diameter between 0.3 mm and 1.8 mm, the insert or each insert (30) being stored in the form of a spool.

5. Method (100) of manufacturing according to any one of claims 1 to 4, wherein the insert or each insert (30) is made up of a plurality of segments.

6. A manufacturing method (100) according to any one of claims 1 to 5, wherein the insert or each insert (30) is solid and capable of passing from a solid state to a liquid or gaseous state, in particular during the step (160) of removing the insert or each insert (30) from the fibrous preform (10).

7. Method (100) according to claim 6, wherein the step (160) of removing the insert or each insert (30) is carried out by melting, dissolving or sublimation.

8. A method (100) of manufacturing according to any one of claims 1 to 7, wherein the insert (30) is made of a material selected from materials with a melting point between 80°C and 650°C such as metals or alloys based on zinc, tin, lead, magnesium, aluminum, or thermosetting or water-soluble polymers such as polyvinyl acetate (PVA), polypropylene (PP), acrylonitrile butadiene styrene (ABS).

9. A method (100) of manufacturing according to any one of claims 7 to 8, comprising: - prior to the step of supplying (120) the rod(s) (20), a step of inserting (115) an insert (30) into the bore (21) of the rod(s) (20), or - between the step of supplying (120) the rod(s) (20) and the step of inserting (130) the rod(s) (30) into the fibrous preform (10), a step of inserting (125) an insert (30) into the bore (21) of the rod(s) (30), or - during the step of inserting (130) the rod(s) (20) into the fibrous preform (10), a substep of inserting (136) an insert (30) into the bore (21) of the rod(s) (20).

10. A method (100) of manufacturing according to any one of claims 1 to 5, wherein the insert or each insert (30) is liquid, viscous, or gelatinous, the method (100) further comprising, during step (130) of inserting the rod or each rod (20) into the fibrous preform (10), a substep consisting of injecting (136) the insert or each insert (30) into the bore (21).

11. A method (100) of manufacturing according to claim 10, wherein the rod (20) is heated, the insert (30) being maintained in a liquid or viscous state by the rod (20), the method (100) comprising, concurrently with the step (140a) of extraction and positioning (140b) of the insert or each insert (30), a step consisting of allowing the insert or each insert (30) to cool (145).

12. A method (100) of manufacture according to claim 10, wherein the insert or each insert (30) is made of a thermoplastic material, for example selected from polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polyvinyl chloride (PVC), or a gelatinous material selected from silicone, filled silicone, a silica-filled thermosetting resin and a thixotropic thermosetting resin.

13. Method (100) of manufacturing according to any one of the preceding claims, wherein the rod or each rod (20) is made of steel.

14. A method (100) according to any one of the preceding claims, wherein the fibrous preform (10) is made of ceramic fibers, and further pre-impregnated with a ceramic matrix, the fibers and the matrix being, for example, based on aluminum oxide.

15. A method (100) of manufacturing according to any one of the preceding claims, wherein the or each device (40) for guiding the insert or each insert (30) comprises two rollers capable of rotating, the two rollers being capable, by rotating, of generating a force in the opposite direction to the direction of movement of the or each rod (20) during the extraction step (140a).

16. Method (100) of manufacturing according to any one of claims 1 to 14, wherein the or each device (40) for guiding the insert or each insert (30) comprises two pads capable of pinching the insert or each insert (30) laterally.

17. A method (100) of manufacturing according to any one of claims 1 to 14, wherein the insert guide device (40) or each insert guide device (30) consists of a guide rod capable of guiding the insert or each insert (30) along a stacking axis (X) direction in the opposite direction to that extraction of the stem (20) during the extraction step (140a) of the stem (20) concerned.

18. A robotic system (200) for carrying out the method according to any one of the preceding claims, the robotic system comprising: - a body (210) having an upper portion (211) capable of rotating about a longitudinal axis (A), - an articulated arm (215) having a first end (216) connected to the upper portion (211) of the body and capable of rotating about a pivot axis (B), and a second end (217), - a tool holder (220) having at least one compartment (221) capable of housing at least one rod (20), the tool holder (220) being connected to the second end (217) of the articulated arm (215), - a feed conduit (230) for filling the rod(s) (20) with an insert (30), said feed conduit (230) having a first end (231) connected to the tool holder (220) and a second end (232) connected to at least one insert support (240).

19. Robotic system (200) according to claim 18 when it depends on claims 15 to 17, further comprising a device (40) for guiding the insert or each insert (30).

20. Robotic system (200) according to claim 19, wherein the tool holder (220) has at least one second compartment suitable for housing the or each of the guiding devices (40).

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