Method for manufacturing a part of cylindrical shape made from stiffened thermoplastic composite material

Abstract

The invention relates to a method for manufacturing a stiffened cylindrical part (1000), comprising: - positioning a precursor assembly of the part to be manufactured in tooling (30), the assembly being made of thermoplastic pre-impregnated fibrous material and comprising (i) a sectorized cylinder, and (ii) stiffening elements present on an inner surface of the cylinder, the tooling comprising an inner part (32) covered with a vacuum bag (34), situated facing the inner surface of the cylinder, and on which the assembly is positioned, and a molding outer part (60) of cylindrical shape, situated facing an outer surface (S2) of the cylinder, and - shaping the assembly on the molding outer part and securing the stiffening elements on the inner surface of the cylinder by co-consolidation by pulling a vacuum in the molding tooling, in order to obtain the part made from composite material to which the stiffening elements are secured.

Description

Description Title of the invention: Method for manufacturing a part made of stiffened thermoplastic composite material having a cylindrical shape Technical Field

[0001] The present disclosure relates to a method for manufacturing a part made of thermoplastic matrix composite material provided with stiffening elements welded by co-consolidation. The invention is of particular interest for the manufacture of cylindrical parts, called ferrules, intended to equip space launchers but is not, however, limited to this application. Prior art

[0002] Composite materials provide a weight saving compared to metallic materials, which is of particular interest in aerospace and aeronautical applications with a view to improving performance.

[0003] Known techniques for providing cylindrical thermoplastic composite parts with stiffening elements do not give entirely satisfactory results. Such parts can in particular form inter-stage shells of space launchers, among other possible applications, which are generally subject to high mechanical stresses and for which the use of stiffening elements is of particular importance.

[0004] Stiffeners made of thermoplastic composite material can be welded in processes where, at a minimum, the joining zone is heated so as to melt the resins present and then the assembly is fixed by cooling. However, in the particular case of parts and stiffening elements each having a cylindrical shape, the correct docking of these elements implies very tight requirements on the shape tolerances of the parts that must be in contact, and these tolerances can be difficult to obtain in the case of double-curved shapes. The complexity of the process can be further increased if a large part is desired. Known techniques can thus lead to clearances between the shell and the stiffening elements, due to a local welding defect, resulting in a significant reduction in the performance of the part, or even in production rejects.

[0005] In addition to this problem of air gap management, there is the problem of the design and cost of the tools to carry out this welding. The complex shapes implemented and the desire to position stiffening elements on an internal surface of the shell do not make this task easy, particularly to maintain the geometry of the parts despite the melting of the thermoplastics and to carry out disassembly at the end of the process. US2020298500 is known, which discloses a method and a system for the co-consolidation of parts made of thermoplastic composite material.

[0006] It is therefore desirable to have a method for manufacturing a stiffened composite material ferrule having a cylindrical shape which overcomes all or part of the aforementioned drawbacks. Statement of the invention

[0007] The present disclosure relates to a method of manufacturing a stiffened thermoplastic composite material part having a cylindrical shape, the method comprising: - the positioning of a precursor assembly of the part to be manufactured in a vacuum molding tool, the assembly being made of thermoplastic pre-impregnated fibrous material and comprising (i) a sectored cylinder formed by panels juxtaposed around an axis of the cylinder, and (ii) stiffening elements assembled on each of the panels and present on an internal surface of the cylinder, the tool comprising an internal part coated with a vacuum cover, located opposite the internal surface of the cylinder and the stiffening elements, on which the assembly is positioned, and an external molding part of cylindrical shape, located opposite an external surface of the cylinder, and - the conformation of the assembly on the external molding part and the formation of the part by co-consolidation of the stiffening elements and the cylinder, comprising: o the curing of the assembly during which a vacuum is drawn in the molding tool so that the vacuum tank applies pressure to press the stiffening elements onto the internal surface of the cylinder and conform the assembly on the external molding part, and during which the thermoplastic resin(s) present in the assembly are melted or softened, and o the cooling of the assembly, after said curing, during which the temperature is reduced to set the assembly thus shaped in shape and obtain the part made of composite material to which the stiffening elements are secured.

[0008] The positioning of the stiffening elements on each of the panels, which form cylinder sectors, is made easier compared to an assembly on a complete shell. The conformation step involving the plating of the elements by vacuum drawing coupled with a rise in temperature to fluidize them ensures the correct docking of the stiffening elements on the cylinder and therefore the good mechanical strength of the welded connection, as well as a robust weld between the neighboring panels. The composite material part is obtained by an operation called co-consolidation of the panels and the stiffening elements which produces a weld, after cooling, due to the interpenetration of the polymer chains having taken place during curing on either side of the welded interfaces.

[0009] Furthermore, the external positioning of the molding part makes it easier to disassemble relative to an internal molding surface. The internal part has in the invention only a positioning function and not a molding function, and therefore has a much simpler design and a more easily disassembled character. Furthermore, the external molding part has a relatively simple design compared to an internal molding surface which should take into account the shape complexity generated by the stiffening elements, and does not interfere with the latter which are located on the internal surface of the cylinder.

[0010] In an exemplary embodiment, the sectored cylinder is formed by the panels juxtaposed around the axis of the cylinder with overlap between the neighboring panels.

[0011] Such a feature makes it possible to further simplify the structure by allowing direct welding of the panels together without requiring the use of a third-party mechanical interface element. However, it does not depart from the scope of the invention if the panels are juxtaposed edge-to-edge with the addition of a mechanical interface element, such as a fishplate, for connecting each pair of neighboring panels.

[0012] In particular, neighboring panels may exhibit a thinning in thickness over their overlapping area towards their edges.

[0013] Such a feature helps to further minimize misalignments and stress concentrations in the resulting part.

[0014] In one exemplary embodiment, each panel comprises a plurality of circumferential frame sectors extending beyond said panel so as to form an extension, said extension being assembled with the frame sectors of a neighboring panel outside a junction zone between these two panels.

[0015] The assembly between the frame sectors introduces a rigidity that is preferable to move outside the junction zone in order to increase the flexibility of this zone and thus facilitating the welding between the panels during co-consolidation. In addition, the assembly between the frame sectors helps to correctly position the panels to form the cylinder.

[0016] In an exemplary embodiment, the method further comprises, prior to positioning the precursor assembly in the molding tooling, forming the panels by automatic fiber placement, the panels being draped over a form separate from the internal positioning portion.

[0017] This technique allows access to a wide variety of geometries, particularly in relation to winding, or to automatically drape excess thicknesses or local reinforcements. In addition, the draping tooling is separated from the vacuum molding tooling, which reduces the manufacturing cycle time.

[0018] In one exemplary embodiment, the stiffening panels and elements comprise carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers.

[0019] These fiber materials are particularly suitable for space launcher applications. Brief description of the drawings [Fig. 1] Figure 1 represents, schematically in perspective, an example of a panel usable within the framework of the invention. [Fig. 2] Figure 2 shows, schematically and partially, a cross-section, with respect to the X axis, of the panel of Figure 1. [Fig. 2A] Figure 2A shows, schematically and partially, the bevel angle of the panel of Figure 2. [Fig. 3] Figure 3 shows, schematically in perspective, the overlapping of two neighboring panels according to an exemplary implementation of the invention. [Fig. 3A] Figure 3A shows, schematically and partially, a detail of an example of assembly between frame sectors of two neighboring panels. [Fig. 4] Figure 4 represents, schematically and partially, a variant of a sectored cylinder. [Fig. 5] Figure 5 represents, schematically and partially, another variant of sectored cylinder. [Fig. 6] Figure 6 represents, schematically and partially, another variant of sectored cylinder. [Fig. 7] Figure 7 represents, schematically and partially, another variant of sectored cylinder. [Fig. 8] Figure 8 represents, schematically and partially, a precursor assembly of the part to be manufactured positioned in a vacuum molding tool as part of an example of implementation of the invention. [Fig. 9] Figure 9 schematically represents the vacuum cooking of the assembly illustrated in Figure 8. [Fig. 10] Figure 10 schematically represents the part obtained after cooling. Description of the embodiments

[0020] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0021] The sectored cylinder is obtained by juxtaposing thermoplastic pre-impregnated fiber panels. Generally, it can include at least two fiber panels, or even at least three fiber panels. The example described here concerns the case of a four-panel cylinder.

[0022] The panels are advantageously made by automatic fiber placement, which is a technique known per se. The panels 10 each comprise a fiber reinforcement pre-impregnated with a thermoplastic resin. The choice of the reinforcing material and the resin depends on the intended application. For example, the fiber reinforcement comprises carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers. For example, the resin is a PAEK (polyaryletherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), PES (polyethersulfone), PPS (polyphenylene sulfide) or PEI (polyetherimide) resin. The same resin is advantageously used in the different panels, or, failing that, compatible resins.

[0023] The panels 10 extend along an X axis, corresponding to the axis of the cylinder obtained after juxtaposition of the panels, and have a curved shape in cross-section relative to the X axis. The panels 10 may or may not have an elongated shape along the X axis, depending on the geometry desired for the part. The panels 10 define two edges 10a, 10b which are, in the illustrated example, intended to be superimposed with a neighboring panel, as will be described below. The edges 10a, 10b extend along the X axis, and may be collinear with the latter as illustrated. Figure 1 illustrates an example of a possible structure for the panels 10 which are draped in a tool female, the person skilled in the art will recognize that the panels may alternatively be draped over male tooling without departing from the scope of the present invention. The draping form is not an integral part of the vacuum molding tooling so as to allow parallel operation between draping and curing, and thus reduce the manufacturing cycle time.

[0024] The panels 10 are, in the example of Figure 1, provided with rectilinear stiffeners 12 made of thermoplastic composite. Each stiffener 12 is formed of a fibrous reinforcement impregnated with a thermoplastic resin identical to, or failing that compatible with, the resin(s) of the panels 10. These stiffeners 12 are formed by conventional means known to those skilled in the art, for example by manual or automated draping, draping in a shaped mold or press stamping of raw flat plates, production of dry preforms and injection of resin into a mold by a resin transfer molding technique (“Resin Transfer Molding”; “RTM”). The stiffeners 12 can have any cross-section, for example Omega, T, J, among other possible shapes. The stiffeners 12 may or may not have a local variation in shape or cross-section.As illustrated, the stiffeners 12 may be present on at least the majority (more than 50%), or even at least 80%, of the DX dimension of the panels measured along the X axis.

[0025] The illustrated panels 10 are also provided with circumferential frame sectors 14 made of thermoplastic composite which constitute stiffening elements. Each frame sector 14 is formed of a fibrous reinforcement impregnated with a thermoplastic resin identical to, or failing that compatible with, the resin(s) of the panels 10 and the stiffeners 12. As for the stiffeners 12, the frame sectors 14 are formed in a manner known per se. The frame sectors 14 may have any cross-section, for example Z-shaped, C-shaped, F-shaped, T-shaped, Omega-shaped or J-shaped. Each frame sector may have a groove at the ends (so as to be assembled by overlapping the other frame sectors in order to form the complete frame), or may be straight (to be assembled to the other frame sectors via a splice piece).The frame sectors 14 may have variations in shape at the level of the flanges which will be in contact with the panel 10 (to best adjust to the variations on the panel 10 side). The frame sectors 14 may have notches crossed by the stiffeners 12 and cooperating with the latter. These notches may have the same shape and substantially the same dimensions as the stiffeners 12 passing through them. The frame sectors 14 may be assembled to the stiffeners 12 by an interface part but it is not outside the scope of the invention if such a part is omitted.

[0026] The frame sectors 14 and the stiffeners 12 are assembled on an internal surface of the cylinder once the panels 10 are juxtaposed. Generally speaking, it will be noted that the panels 10 may include areas of excess thickness forming local reinforcements.

[0027] The stiffeners 12 and frame sectors 14 are assembled on the panels 10 by techniques known per se, such as spot welding, stapling, or the use of added fasteners. This assembly simply has the purpose of positioning the stiffeners 12 and frame sectors 14 on the panels 10, but not of producing a robust connection of the latter to the panels 10 which is obtained after the co-consolidation which will be described below.

[0028] In the illustrated example, the panels 10 also have a zone 19, located on the side of the edge 10b and extending over the entire dimension DX, which is devoid of any stiffening element (no stiffener 12, nor frame sector 14). It will also be noted that, in the illustrated example, the frame sectors 14 protrude from the panel 10 on the side opposite the zone 19 (on the side of the edge 10a), and form an extension 15 of the frame sectors 14. The presence of the zone 19 as well as the extension of the frame sectors 14 are the result of the arrangement envisaged for the juxtaposition between neighboring panels 10.

[0029] Figure 2 shows the evolution of the thickness elO of the panels 10 along the Y axis perpendicular to the X axis. The panels 10 have a middle zone 101 of their width where the thickness elO is substantially constant, and two lateral zones 103a and 103b each located on the side of a respective edge 10a, 10b which have an evolving thickness. The zone 101 is located between the zones 103a, 103b. The zone 103a connects the zone 101 to the edge 10a, and the zone 103b connects the zone 101 to the edge 10b. More precisely, the zones 103a, 103b have a thinning of thickness in the direction of the associated edge 10a, 10b. The thickness elO can be strictly decreasing in the direction of the edge 10a, 10b. The thickness elO is minimal on the edges 10a, 10b and maximal on the middle zone 101. The panels 10 have a bevel on their edges 10a, 10b. The panels 10 have, in cross-section relative to the X axis, a tapered shape towards their edges 10a, 10b. The zones 103a and 103b jointly occupy at least 5%, for example at least 50%, of the dimension DY of the panel 10. Unless otherwise stated, the dimension DY corresponds to the length of the arc of the curve connecting the edge 10a to the edge 10b. The thinning of thickness leads to a reduction in the thickness elO of at least 50%, for example at least 90%. This reduction in the thickness elO is for example between 50% and 95%, or even between 90% and 95%. Figure 2A schematically represents a thinning of the thickness of the panel 10 in the direction of an edge 10b linked to the presence of a decreasing quantity of superimposed plies PS in the direction of the edge 10b. The bevel angle a, corresponding to the angle taken locally on the edge 10b, can advantageously be less than or equal to 1.5°, so as to further improve the smoothing of the forces.

[0030] The following describes, in connection with figures 3 to 7, the juxtaposition of these panels 10 to form the sectored cylinder 100. The frame stiffeners 12 and sectors 14 have not been shown in figures 4 to 7.

[0031] Figure 3 illustrates the juxtaposition of two neighboring panels 10 around the X axis. The two illustrated panels 10 have the same structure and the same references are retained with respect to what has just been described. The panels 10 partially overlap here. The panels have a thinning of thickness on their overlap zone ZR10, that is to say that the zone 103b of the first panel 10 is covered by the zone 103a of the second neighboring panel 10. The edge 10b of the first panel 10 is superimposed with the second neighboring panel 10, and the edge 10a of the second panel 10 is superimposed with the first panel. The stiffeners 12 and frame sectors 14 of the second panel 10 cover the area 19 of the first panel 10. The extension 15 of the frame sectors 14 of the second panel 10 extends over the area 101 of the first panel and is positioned adjacent to and in line with the frame sectors 14 of the first panel.The extension 15 extends beyond the overlap zone ZR10, which here corresponds to the junction zone between the panels 10. The extension 15 is assembled with the frame sectors 14 of the first panel 10 by techniques known per se, for example by overlapping, joisting or splicing. This assembly can be carried out outside the zone ZR10. Figure 3A illustrates an example of such an assembly where a splice plate 14a, present outside the zone ZR10, connects the frame sectors 14 of the first and second panels 10. The splice plate 14a can also comprise a thermoplastic material so as to ensure its welding to the frame sectors 14 during co-consolidation.

[0032] The arrangement just described can be applied to each pair of neighboring panels 10 juxtaposed to form the sectored cylinder. Generally speaking, the overlapping areas between neighboring panels can occupy at least 5%, for example at least 30% of the perimeter of the sectored cylinder. Having spread overlapping areas makes it possible to further improve the mechanical properties of the resulting part. In particular when all the panels are assembled to form the sectored cylinder, the joining of the frame sectors 14 of each of the panels defines a plurality of 360° circumferential frames.

[0033] Figures 4 to 7 show different variants of juxtaposition of the panels 10 to form the sectored cylinder 100. The cylinder 100 is a cylinder with axis X with panels juxtaposed around this axis. The axis X corresponds to the axis of revolution of the cylinder.

[0034] In the variant of Figure 4, the cylinder 100 is formed by tiling all the panels 10, that is to say that each of the panels has a first edge 10b covering (above) a first neighboring panel, and a second edge 10a, opposite the first edge 10b, covered (below) by a second neighboring panel, opposite the first neighboring panel. In particular, the thinning of the thickness of the neighboring panels 10 over their overlapping zone ZR10 in the direction of their edges 10a, 10b is noted.

[0035] In the variant of figure 5, there is tiling except for panel 10 at the bottom right of the figure which covers its two neighboring panels.

[0036] The variants of Figures 6 and 7 show cases where there is no tiling which are also covered by the present invention.

[0037] The case of beveled panels 10, having a thinning of thickness on their overlap zone, has just been described. It will be noted that it is not outside the scope of the invention when the panels have straight sides, or having a groove (which will allow an assembly by overlap).

[0038] The following describes the positioning in the vacuum casting tool. A possible kinematic for the assembly of the vacuum casting tool 30 and the positioning of the precursor assembly will now be detailed in connection with Figure 8. In this figure, as well as in Figures 9 and 10, the relative thicknesses as well as the spacings between the different elements have not been strictly respected for reasons of readability.

[0039] A vacuum cover 34 is initially placed over a positioning portion 32. The portion 32 is of much simpler design than a molding surface in that it is simply used for positioning the elements. It is, therefore, more easily removable. The portion 32 is supported by a shaft 36 which extends along the X axis which corresponds to the X axis of the panels 10 and the cylinder 100, which has been described previously. The portion 32 may have an aerated structure, for example a lattice, or comprise a plurality of retractable positioning elements attached to the shaft. The portion 32 may, as illustrated, generally have the shape of the part to be obtained. The cover 34 covers the portion 32. The cover 34 may be made of elastomeric material, reinforced or not, and constitutes an element known per se.

[0040] Positioning rings 40 are then positioned at the ends 361, 363 of the shaft 36 which define a cylindrical positioning surface 42 intended to guide the external molding part 60 during its positioning.

[0041] The panels 10 are then positioned and juxtaposed, in the manner described above, so as to form the cylinder 100, precursor of the part to be obtained. The cylinder 100 is positioned around the part 32 (and the tarpaulin 34). In the example illustrated, each panel 10 carries a plurality of frame sectors 14 and a plurality of stiffeners 12. The part 32 may define housings, for example in the form of cavities opening onto the surface of the part 32, in which the stiffening elements 12, 14 are positioned. The stiffening elements 12, 14 may bear on a wall defining the cavities, or on a positioning element present in them, to assist in their placement in the tooling 30.

[0042] The cylinder 100 delimits an internal volume V of the part to be obtained. The cylinder 100 is made of thermoplastic pre-impregnated fibrous material. The stiffening elements 12, 14 are assembled on an internal surface SI of the cylinder 100. In the example illustrated, the stiffeners 12 carried by the cylinder 100 can be regularly spaced along a circumferential direction, around the axis X. Similarly, the frame sectors 14 carried by the cylinder 100 can be regularly spaced along the axis X. However, it does not depart from the scope of the invention when these spacings are not regular, the positioning of the stiffening elements being adjusted according to the part and the stresses it undergoes during operation.

[0043] In the example illustrated, the cylinder 100 has a diameter greater than its dimension along the X axis. However, the scope of the invention does not depart when the invention is applied to the formation of parts having an elongated shape along the X axis, for example at least ten meters long.

[0044] The external molding part 60 is then positioned, which is in the shape of the part to be obtained and which surrounds the cylinder 100. The cylinder 100 is located inside the part 60. The part 60 is located around the cylinder 100. As illustrated, the part 60 extends from one ring 40 to the other. It comes opposite the surface 42. An internal surface S1 of the cylinder 100 is located on the side of the cover 34 (and delimits the internal volume V), and an external surface S2 of the cylinder 100 is located on the side of the part 60. In the example illustrated, the shaft 36, as well as the tooling 30, are oriented vertically, but the person skilled in the art will recognize that the invention can be applied to a tooling 30 extending horizontally. In which case, it may prove useful to provide the molding part with stiffeners on its face. opposite to the assembly so that it retains its shape, particularly if the manufacture of a part of considerable length is envisaged.

[0045] The seals 52 between the tarpaulin 34 and the part 60 are then made.

[0046] The precursor assembly is thus positioned in the vacuum molding tool 30 for the purpose of forming the part by co-consolidation. In particular, the cylinder 100 is interposed between the tarpaulin 34 and the molding part 60. The part 32 is located inside the precursor assembly, that is to say is located inside the internal volume V of the part to be obtained. The part 60 is located outside this internal volume V and forms an external part of the assembly, intended for molding the part.

[0047] In the illustrated example, the panels 10 are juxtaposed around the X axis with overlap between the neighboring panels. The neighboring panels 10 may be in contact on their overlap zone ZR10. The stiffeners 12 and frame sectors 14 may be in contact with the panels 10, and therefore with the internal surface of the cylinder 100.

[0048] The tool 30 is vacuum-applied so that the cover 34 presses the stiffening elements 12, 14 onto the internal surface SI of the cylinder 100 and conforms the assembly to the desired shape against the part 60. In particular, the vacuum drawing leads to the panels 10 being pressed against their overlapping zone ZR10, as well as to the application of pressure to the stiffeners 12 and frame sectors 14 which are pressed against the internal surface SI. Pressure is also applied to any third-party assembly elements, useful for connecting the frame sectors 14 of neighboring panels 10, to press the assembly to be connected onto the surface SI.

[0049] The curing process then proceeds, maintaining the vacuum, which leads to melting or softening of the thermoplastic resin(s) present. The fluidification of the resin(s) promotes the conformation of the elements to be welded and produces interpenetration of the polymer chains at the interfaces between them. Thus, during curing: - for each pair of neighboring panels, the resin of a first panel penetrates into a second neighboring panel and the resin of the second panel penetrates into the first panel, - the resin(s) of the stiffening elements penetrate into the panel on which these elements are assembled and the resin of the panel in question penetrates into these stiffening elements, and - the resin of a first set of frame sectors 14 penetrates into a second set of frame sectors 14 adjacent to this first set.

[0050] Curing can be carried out in a heating chamber, such as an oven or an autoclave. The autoclave will provide additional pressure in addition to the vacuum. Alternatively or in combination, a molding tool equipped with heating elements (not shown) can be used to carry out this curing. The temperature imposed during curing depends on the resin(s) used and can, for example, be greater than or equal to 300°C, for example between 300°C and 400°C.

[0051] After curing, cooling is carried out to set the structure (in particular to solidify the thermoplastic resin(s) present) and obtain the part 1000 (figure 10). Generally speaking, the vacuum can be maintained during this cooling. Cooling makes it possible to obtain a welded junction between the different elements of the part due to the interpenetration of the polymer chains of the resin(s) present previously carried out during curing. The part 1000 is tubular in cylindrical shape, and forms a stiffened shell. It constitutes an integrated structure with assembly by co-consolidation of all the constituent elements of the structure.In particular, there is co-consolidation welding of the panels 10 together to form the shell, co-consolidation welding of the stiffeners 12 and frame sectors 14 on the internal surface of the part 1000, and co-consolidation welding of the frame sectors 14 together (by overlapping or splicing for example).

[0052] A tool 30 made of composite material may be used to reduce the phenomenon of differential expansion between the tool 30 and the part 1000. Alternatively, the tool 30 may be metallic, for example made of Invar, or steel. In the latter case, it may be advantageous to minimize stresses during cooling by providing a gap in the part 60.

[0053] The tooling 30 is then dismantled, which is facilitated by the positioning of the molding part 60 outside the part 1000 obtained, and by the simplified design of the internal part 32.

[0054] The part 1000 obtained can be integrated into a space launcher, for example as an inter-stage or inter-tank shell, or even form a tank after adding bottom elements. The field of the invention is however not limited to a part for integration into an aerospace launcher and the part can alternatively find an application in the aeronautical field or, more generally, in any application requiring a stiffened shell.

[0055] The expression "between ... and ..." must be understood as including the limits.

Claims

Claims

1. A method of manufacturing a part (1000) made of stiffened thermoplastic composite material having a cylindrical shape, the method comprising: - positioning a precursor assembly of the part to be manufactured in a vacuum molding tool (30), the assembly being made of thermoplastic pre-impregnated fibrous material and comprising (i) a sectored cylinder (100) formed by panels (10) juxtaposed around an axis (X) of the cylinder, and (ii) stiffening elements (12; 14) assembled on each of the panels and present on an internal surface (SI) of the cylinder, the tool comprising an internal part (32) coated with a vacuum cover (34), located opposite the internal surface of the cylinder and the stiffening elements, on which the assembly is positioned, and an external molding part (60) of cylindrical shape, located opposite an external surface (S2) of the cylinder, and - the conformation of the assembly on the external molding part and the formation of the part by co-consolidation of the stiffening elements and the cylinder, comprising: o the curing of the assembly during which a vacuum is drawn in the molding tool so that the vacuum tank applies pressure to press the stiffening elements onto the internal surface of the cylinder and conform the assembly on the external molding part, and during which the thermoplastic resin(s) present in the assembly are melted or softened, and o the cooling of the assembly, after said curing, during which the temperature is reduced to set the assembly thus shaped in shape and obtain the part made of composite material to which the stiffening elements are secured.

2. Method according to claim 1, in which the sectored cylinder (100) is formed by the panels (10) juxtaposed around the axis (X) of the cylinder with overlap between the neighboring panels.

3. Method according to claim 2, in which the neighboring panels (10) have a thinning of thickness on their overlapping zone (ZR10) in the direction of their edges (10a; 10b).

4. A method according to any one of claims 1 to 3, wherein each panel (10) comprises a plurality of circumferential frame sectors (14). extending beyond said panel so as to form an extension (15), said extension being assembled with the frame sectors of a neighboring panel outside a junction zone (ZR10) between these two panels.

5. A method according to any one of claims 1 to 4, the method further comprises, before positioning the precursor assembly in the molding tooling (30), forming the panels (10) by automatic fiber placement, the panels being draped over a form distinct from the internal positioning part.

6. A method according to any one of claims 1 to 5, wherein the panels (10) and stiffening elements (12; 14) comprise carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers.

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