Manufacture of a part made of composite material by superposing thermoformed fibrous preforms

Abstract

The invention relates to a method for manufacturing a part (5) made of composite material, said method comprising: - producing a first fibrous blank (510) by draping over a first draping surface (S100), - producing a first fibrous sub-preform (51) by thermoforming the first fibrous blank (510) on a first thermoforming surface (S10), - producing at least a second fibrous blank (520) by draping over a second draping surface (S200), - producing at least a second fibrous sub-preform (52) by thermoforming the second fibrous blank (520) on a second thermoforming surface (S20), - stacking the sub-preforms (51, 52, 53) so as to obtain a fibrous preform (50) having the shape of the part (5) to be obtained, - consolidating the fibrous preform (50) so as to obtain the part (5).

Description

Description Title of the invention: Manufacture of a part in composite material by superimposing thermoformed fiber preforms Technical Field

[0001] The present invention relates to the manufacture of composite material parts by draping and thermoforming. In particular, but not exclusively, the invention relates to the manufacture of aeronautical engine parts, nacelles or fuselages. Prior art

[0002] The use of composite materials for the manufacture of aeronautical parts, for example for aeronautical engine casings, makes it possible to obtain resistant parts with mechanical performance equivalent to or even superior to those made of metal, while having a much lower mass. Thus, their use contributes to optimizing the performance of turbomachines or turbomachine equipment, thereby reducing fuel consumption and harmful emissions such as carbon monoxide, carbon dioxide or nitrogen oxides of the "NOx" type.

[0003] It is known to produce composite material parts by draping them on a surface of fibrous plies pre-impregnated with resin. For reasons of production costs and repeatability, draping can be carried out automatically, using the automatic fiber placement technique known as "AFP" in English, for "automated fiber placement". An example of a method for manufacturing a composite material part using the "AFP" method is for example described in document FR3062336B1.

[0004] The draping of the fibrous plies makes it possible to obtain a fibrous blank pre-impregnated with a resin, which will then be shaped to obtain a fibrous preform of the part to be obtained. Indeed, the geometry of the desired fibrous preform is not always directly achievable by draping, in particular when said geometry has hollows or angles at the bottom which the draping head cannot access. Said fiber preform is then consolidated in a well-known manner to form a matrix, in order to obtain the desired composite material part.

[0005] The shaping of the fiber blank into a fiber preform is conventionally carried out by thermoforming. This thermoforming step involves raising the temperature of the fiber blank in order to reduce the viscosity of the resin that impregnates it, and thus to be able to proceed with the deformation of said blank.

[0006] However, it has been found that such a process can lead to non-homogeneous deformations and unwanted stress concentrations, particularly in the structural areas of the part. The final composite material obtained may therefore have defects and poorly controlled material quality, for example fiber undulations in the areas where forming generates the most significant inter-ply slippage. Statement of the invention

[0007] It has been found that the aforementioned defects are particularly marked when producing relatively thick parts comprising numerous plies, in particular more than 20 plies, and in particular when said parts have relatively complex geometries, thus generating significant inter-ply slippage during the forming phases. Indeed, when the fiber blanks are made up of a large number of pre-impregnated plies, these can slide relative to each other in an uncontrolled manner during the thermoforming step, and induce defects such as undulations or creases in the fiber blank obtained.

[0008] To counter this phenomenon, the invention proposes to reduce the thickness of the fiber blanks to be thermoformed, by producing the final preform by stacking several separately thermoformed sub-preforms.

[0009] To this end, the invention proposes a method for manufacturing a part made of composite material comprising the following steps:

[0010] - the production of a first fiber blank by draping one or more first pre-impregnated plies on a first draping surface,

[0011] - the production of a first fibrous sub-preform by thermoforming the first fibrous blank on a first thermoforming surface,

[0012] - the production of at least one second fiber blank by draping one or more second pre-impregnated plies on a second draping surface different from the first draping surface,

[0013] - the production of at least one second fibrous sub-preform by thermoforming the second fibrous blank on a second thermoforming surface different from the first thermoforming surface,

[0014] - stacking the fiber sub-preforms so as to obtain a fiber preform having the shape of the part to be obtained,

[0015] - consolidation of the fiber preform so as to form a matrix to obtain the composite material part.

[0016] Thus, by breaking down the fiber preform into several fiber sub-preforms of reduced thickness, the thickness of the fiber blanks to be thermoformed is reduced. Consequently, the number of pre-impregnated plies to be thermoformed in a single operation is also reduced, which limits the occurrence of defects due to thermoforming.

[0017] According to a particular embodiment of the invention, the drapings are carried out by an automated draping method.

[0018] For example, layups can be performed by automatic fiber placement, known as “AFP”. Layups can also be performed by automatic ribbon deposition, known as “ATL”, or by “pick and place” type deposition.

[0019] Indeed, compared to manual draping, automated draping saves time and reduces production costs while ensuring better draping repeatability.

[0020] According to another particular embodiment of the invention, the fibrous blanks are pre-impregnated with a resin.

[0021] According to another particular embodiment of the invention, the draping surfaces are convex and the thermoforming surfaces are concave.

[0022] This improves the control of the material quality obtained for each fiber sub-preform in the thermoformed areas which are most often critical from a mechanical point of view.

[0023] According to another particular embodiment of the invention, the first thermoforming surface is formed by the second fibrous preform arranged on the second thermoforming surface.

[0024] As a result, the tooling required to implement the method of the invention is reduced. In fact, a single thermoforming mold can be used for all thermoforming operations, the previously thermoformed fiber sub-preform being used as a thermoforming surface for the next fiber sub-preform.

[0025] According to another particular embodiment of the invention, the draping surfaces comprise at least one end zone having undulations, so that the part of the fibrous blanks formed on said end part having undulations is deformed during thermoforming so as to produce at least one fibrous sub-preform sub-flange, the stacking of the fibrous sub-preform sub-flanges producing at least one fibrous preform flange intended to form at least one flange on the final part.

[0026] According to another particular embodiment of the invention, the method further comprises a preliminary step of determining the number of fiber sub-preforms to be produced, according to which the minimum number of stacked fiber sub-preforms to be produced is determined so that the probability of the appearance of a forming defect during the thermoforming of a fiber sub-preform is less than a determined probability value.

[0027] According to another particular embodiment of the invention, the determined probability value is W 9 . Brief description of the drawings

[0028] [Fig. 1] Figure 1 is a schematic perspective view of a composite material part obtained by the method of the invention.

[0029] [Fig. 2] Figure 2 is a schematic exploded perspective view of a fiber preform of the part of Figure 1 composed of a plurality of fiber sub-preforms.

[0030] [Fig. 3] Figure 3 is a flowchart illustrating a manufacturing method according to the invention.

[0031] [Fig. 4] Figure 4 is a schematic perspective view of the thermoforming of a first fiber blank into a first fiber sub-preform.

[0032] [Fig. 5] Figure 5 is a schematic perspective view of the thermoforming of a second fiber blank into a second fiber sub-preform.

[0033] [Fig. 6] Figure 6 is a schematic perspective view of the thermoforming of a third fiber blank into a third fiber sub-preform.

[0034] [Fig. 7] Figure 7 is a schematic perspective view of a thermoforming mold.

[0035] [Fig. 8] Figure 8 is a schematic perspective view of the thermoforming mold of Figure 6 on which the third fiber blank was thermoformed to obtain the third fiber sub-preform.

[0036] [Fig. 9] Figure 9 is a schematic perspective view of the thermoforming mold of Figure 6 on which the second fiber blank was thermoformed to obtain the second fiber sub-preform.

[0037] [Fig. 10] Figure 10 is a schematic perspective view of the thermoforming mold of Figure 6 on which the first fiber blank was thermoformed to obtain the first fiber sub-preform.

[0038] [Fig. 11] Figure 11 is a schematic perspective view of a draping mold for draping the first fiber blank.

[0039] [Fig. 12] Figure 12 is a schematic perspective view of a draping mold for draping the second fiber blank.

[0040] [Fig. 13] Figure 13 is a schematic perspective view of a draping mold for draping the third fiber blank.

[0041] [Fig. 14] Figure 14 is a schematic and partial view of a fiber blank draped by automatic fiber placement. Description of the embodiments

[0042] The present invention relates to the manufacture of a part made of composite material by draping. In particular, the present invention is particularly advantageous for the production of thick parts and / or parts having a complex geometry. The present invention is particularly advantageous for the production of a part formed by at least 20 pre-impregnated plies deposited by draping, and even more advantageous for the production of a part formed by at least 40 pre-impregnated plies deposited by draping.

[0043] Figure 1 illustrates an example of a part 5 made of composite material which can be produced by the method of the invention.

[0044] The part 5 made of composite material to be obtained may comprise a shell-shaped body extending around an axis, for example a body 5a in the form of a half-shell extending around an axis A as in the example illustrated in FIG. 1. The body 5a may have a cylindrical or truncated partial revolution shape, or any partial revolution shape.

[0045] The part 5 made of composite material to be obtained may comprise at least one flange 5b at one of its ends, as in the example illustrated in FIG. 1. The flange(s) 5b are located in the extension of the body 5a of the part 5 to be obtained. The part 5 further comprises an internal face 5i and an external face 5e, defined relative to the axis A.

[0046] In accordance with the method of the invention, the part 5 to be obtained will be produced by densification of a pre-impregnated fiber preform 50, said fiber preform 50 being obtained by stacking a plurality of fiber sub-preforms 51, 52, 53 obtained by draping and thermoforming, as illustrated in Figure 2. fibrous sub-preforms 51, 52, 53 are stacked so as to overlap radially. Thus, the fibrous sub-preforms 51, 52, 53 overlap in the thickness of the fibrous preform 50.

[0047] The fibrous sub-preforms 51, 52, 53 comprise an inner face 51i, 52i, 53i and an outer face 51e, 52e, 53e. The fiber sub-preforms 51, 52, 53 are stacked so that the inner face 52i, 53i of an outer fiber sub-preform 52, 53 is in contact with the outer face 51e, 52e of an inner fiber sub-preform 51, 52. The inner face 5 li of the fiber sub-preform 51 arranged furthest to the inside of the fiber preform 50 will be intended to form the inner face 5i of the part 5. The outer face 53e of the fiber sub-preform 53 arranged furthest to the outside of the fiber preform 50 will be intended to form the outer face 5e of the part 5.

[0048] Each fiber sub-preform 51, 52, 53 may comprise a sub-body 51a, 52a, 53a, intended to form a portion of the thickness of the body 5a of the final part 5, and at least one sub-flange 51b, 52b, 53b, intended to form a portion of the thickness of the flange 5b of the final part 5.

[0049] We will now describe a first optional preliminary step Ei of designing the method of the invention, in relation to figure 3.

[0050] Following a first sub-step En of this first optional preliminary step Ei, we first determine the total number P to of pre-impregnated plies to be draped to obtain the fibrous preform 50 of the part 5. The present invention is particularly interesting in the case where the total number P to tai of pre-impregnated plies to be draped to obtain the fiber preform 50 of the part 5 is greater than 20. The total number Ptotai of pre-impregnated plies to be draped is determined according to the thickness of the part 5 to be obtained and according to the material(s) constituting the pre-impregnated plies to be draped to obtain the part 5.

[0051] Following a second sub-step E i2from this first optional preliminary step Ei, we determine the maximum number of superimposed folds P ma x for which the probability Pdefect of a forming defect occurring during thermoforming is low. The probability Pdefect of a forming defect occurring during thermoforming is determined according to the material(s) constituting the pre-impregnated plies to be draped and according to the geometry of the part 5 to be obtained. This probability Pdefect of the appearance of a forming defect during thermoforming can be obtained by carrying out tests. In particular, the maximum number of superimposed plies P is determined ma x for which the probability Pdefect of the appearance of a forming defect during thermoforming is less than or equal to a determined probability value p r ef. Preferably, the determined value p r ef is equal to 10' 9 .

[0052] Generally, the maximum number of overlapping folds P ma x is preferably less than or equal to 20 for 90° forming.

[0053] The first and second sub-steps of this optional preliminary step can be carried out simultaneously.

[0054] Following a third sub-step E i3 from this first optional preliminary step E we determine the number N of fiber sub-preforms 51, 52, 53 to be produced to obtain the fiber preform 50 of the part. For this purpose, we determine the minimum number N mini of fiber sub-preforms 51, 52, 53 to be produced to obtain the fiber preform 50 of the part 5. The minimum number N m The number of fiber sub-preforms 51, 52, 53 to be produced is determined by dividing the total number Ptotai of pre-impregnated plies to be draped to obtain the fiber preform 50 of the part 5 by the maximum number of superimposed plies P max- If the ratio of the total number Ptotai of pre-impregnated plies to be draped by the maximum number of superimposed plies P ma x is an integer, then the minimum number N mini of fiber sub-preforms 51, 52, 53 to be produced is equal to this integer. If the ratio of the total number P to number of pre-impregnated plies to be draped by the maximum number of superimposed plies P ma x is not an integer, then the minimum number Nmini of fiber sub-preforms 51, 52, 53 to be produced corresponds to the rounding up of this quotient.

[0055] For example, if the total number Ptotai of pre-impregnated plies to be draped is 30 and the maximum number of overlapping plies P ma x is 7, the minimum number Nmini of fiber sub-preforms 51, 52, 53 to be produced will be 5.

[0056] The number N of fiber sub-preforms 51, 52, 53 to be produced to obtain the fiber preform 50 of the part 5 is preferably chosen to be equal to the number minimum N m number of fiber sub-preforms 51, 52, 53 to be produced to obtain the fiber preform 50 of the part 5. The number N of fiber sub-preforms 51, 52, 53 to be produced to obtain the fiber preform 50 of the part 5 must be greater than or equal to the minimum number N mini of fibrous sub-preforms 51, 52, 53 to be produced to obtain the fibrous preform 50 of the part 5.

[0057] Following a fourth sub-step E M of the first optional preliminary step Ei, the distribution of the number of plies in each fiber sub-preform 51, 52, 53 to be produced to obtain the fiber preform 50 of the part 5 is determined. The distribution of the plies per fiber sub-preform 51, 52, 53 is carried out so that the number of plies present in each fiber sub-preform 51, 52, 53 is less than or equal to the maximum number of superimposed plies P max- Preferably, each fiber sub-preform 51, 52, 53 comprises a similar number of plies, or even comprises the same number of plies.

[0058] The characteristics of each fiber sub-preform 51, 52, 53 to be produced are thus obtained. A fiber sub-preform 51, 52, 53 is obtained by thermoforming a fiber blank 510, 520, 530, as illustrated in FIGS. 4 to 6.

[0059] Following a fifth sub-step E i5 of the first optional preliminary step E the characteristics of the thermoforming surfaces Si0, S20, S30 of the thermoforming mold(s) 10, 20, 30 intended to allow the thermoforming of the fiber blanks 510, 520, 530 into fiber sub-preforms 51, 52, 53, as illustrated in Figures 7 to 10, are determined. These characteristics can easily be determined from the characteristics of each fiber sub-preform 51, 52, 53 to be produced determined previously.

[0060] In the example shown, the thermoforming surfaces S10, S2o, S 30 of the thermoforming mold(s) 10, 20, 30 each comprise a sub-body area 10a, 20a, 30a intended to allow the thermoforming of the sub-body 51a, 52a, 53a of the fibrous sub-preform 51, 52, 53. The thermoforming surfaces S10, S20, S 30 of the thermoforming mold(s) 10, 20, 30 also each comprise a sub-flange zone 10b, 20b, 30b intended to allow the thermoforming the sub-flange 51b, 52b, 53b of the fiber sub-preform 51, 52, 53.

[0061] Following a sixth sub-step EI6 of the first optional preliminary step E, the characteristics of each fiber blank 510, 520, 530 intended to form a fiber sub-preform 51, 52, 53 after thermoforming on the thermoforming surfaces Si0, S2o, S are determined. 30 .

[0062] The fiber blank 510, 520, 530 comprises the same number of pre-impregnated plies as the fiber sub-preform 51, 52, 53 that said fiber blank 510, 520, 530 is intended to form. The shape of the fiber blank 510, 520, 530 to be draped is easily determined by a person skilled in the art from the shape of the fiber sub-preform 51, 52, 53 that said fiber blank 510, 520, 530 is intended to become. Indeed, the fiber sub-preform 51, 52, 53 to be produced has a geometry that cannot be produced directly by draping, for example because it has hollows or angles whose bottom cannot be reached by the laying head of a draping device.

[0063] In the case where the fibrous sub-preforms 51, 52, 53 to be produced have a sub-flange 51b, 52b, 53b at at least one of their ends, the associated fibrous blanks 510, 520, 530 will have, in a well-known manner, a corrugated end portion 510b, 520b, 530b called “flange portion of the fibrous blank” intended to be thermoformed into a sub-flange.

[0064] Determining the geometry of a draped fiber blank 510, 520, 530 to be thermoformed into a desired shape is well known to those skilled in the art, in particular for producing a part comprising at least one flange. An example of such determination is described in particular in document WO2012 / 046020.

[0065] The fiber blanks 510, 520, 530 comprise an inner face 510i, 520i, 530i and an outer face 510e, 520e, 530e, as illustrated in FIGS. 4 to 6. The inner face 510i, 520i, 530i of each fiber blank 510, 520, 530 is intended to form the inner face 511, 52i, 53i of a fiber sub-preform 51, 52, 53. The outer face 510e, 520e, 530e of each fiber blank 510, 520, 530 is intended to form the external face 51e, 52e, 53e of a fibrous sub-preform 51, 52, 53.

[0066] Following a seventh sub-step E i7 from the first optional preliminary step E we determine the characteristics of the draping surfaces Si 00 , S 2O o, S300 of the draping molds 100, 200, 300 intended to allow the draping of the fiber blanks 510, 520, 530. These characteristics can easily be determined from the characteristics of each fiber blank 510, 520, 530 determined previously.

[0067] All the sub-steps presented above are optional, and it is of course not outside the scope of the invention if none or only part of these sub-steps are carried out.

[0068] We will now describe the manufacture of the plurality of fiber sub-preforms 51, 52, 53, according to a second step E2, as illustrated in FIG. 3.

[0069] The plurality of fiber blanks 510, 520, 530 are produced by draping.

[0070] The first fiber blank 510 is produced by draping on a first draping surface Si 00 . As illustrated in Figure 11, the first layup surface S100 belongs to a first layup mold 100. In the illustrated example, the first layup surface Si 00comprises at least one main zone 100a and a corrugated end zone 100b located in the extension of the main zone 100a. The main zone 100a of the first layup surface Si 00 presents the geometry of the body portion 510a of the first fiber blank 510 to be obtained. Thus, the pre-impregnated plies draped over the main area 100a of the first draping surface S100 are intended to form the body portion 510a of the first fiber blank 510 to be obtained. The corrugated end area 100b of the first draping surface S100 presents the geometry of the flange portion 510b of the first fiber blank 510 to be obtained. Thus, the pre-impregnated ply(ies) draped over the corrugated end area 100b of the first draping surface S100 are intended to form the flange portion 510b of the first fiber blank 510 to be obtained.

[0071] The second fiber blank 520 is produced by draping on a second draping surface S 2Oo- As illustrated in Figure 12, the second draping surface S200 belongs to a second draping mold 200. In the illustrated example, the second draping surface S200 comprises at least one main zone 200a and a corrugated end zone 200b located in the extension of the main zone 200a. The main zone 200a of the second draping surface S200 has the geometry of the body portion 520a of the second fiber blank 520 to be obtained. Thus, the pre-impregnated plies draped on the main zone 200a of the second draping surface S200 are intended to form the body portion 520a of the second fiber blank 520 to be obtained. The corrugated end zone 200b of the second draping surface S200 has the geometry of the flange portion 520b of the second fiber blank 520 to be obtained.Thus, the pre-impregnated ply(ies) draped over the corrugated end zone 200b of the second draping surface S200 are intended to form the flange portion 520b of the second fiber blank 520 to be obtained.

[0072] The third fiber blank 530 is produced by draping on a third draping surface S 300 . As illustrated in Figure 13, the third draping surface S300 belongs to a third draping mold 300. In the illustrated example, the third draping surface S 300comprises at least one main zone 300a and a corrugated end zone 300b located in the extension of the main zone 300a. The main zone 300a of the third lay-up surface S300 has the geometry of the body portion 530a of the third fiber blank 530 to be obtained. Thus, the pre-impregnated plies draped on the main zone 300a of the third lay-up surface S300 are intended to form the body portion 530a of the third fiber blank 530 to be obtained. The corrugated end zone 300b of the third lay-up surface S300 has the geometry of the flange portion 530b of the third fiber blank 530 to be obtained. Thus, the pre-impregnated ply(ies) draped on the corrugated end zone 300b of the third lay-up surface S300 has the geometry of the flange portion 530b of the third fiber blank 530 to be obtained. Thus, the pre-impregnated ply(ies) draped on the corrugated end zone 300b of the third lay-up surface S300 has the geometry of the flange portion 530b of the third fiber blank 530 to be obtained. 300 are intended to form the flange portion 530b of the third fiber blank 530 to be obtained.

[0073] The second draping surface S200 is different from the first draping surface Si 00 . Preferably, the second draping surface S200 has an overall shape similar to the overall shape of the first draping surface Swo- The second draping surface S200 may have dimensions proportionally larger than the dimensions of the first draping surface Si 00 . The first draping surface Si 00 belongs to a first draping mold 100 different from the second draping mold 200 comprising the second draping surface S 200 . The first draping mold 100 is not included in the second draping mold 200.

[0074] More generally, the draping surfaces Si 00 , S 200 , S 300are all different from each other. Preferably, the draping surfaces S100, S200, S300 have a similar overall shape. The dimensions of the draping surfaces Si 00 , S 200 , S 300 are preferably proportional to each other.

[0075] The production of the fiber blanks 510, 520, 530 is preferably carried out by automatic placement of fibers, according to the so-called “AFP” method.

[0076] Figure 14 schematically illustrates the structure of a deposition head 80 of a device for implementing an AFP technique. The structure of the deposition head 80 is well known. The deposition head 80 is fed by a fibrous strip or wick 500.

[0077] The fibrous strip or wick 500 may be impregnated with a resin according to a particularly advantageous embodiment of the invention. In particular, the fibrous strip or wick 500 may be impregnated with a thermosetting polymer or be impregnated with a thermoplastic polymer. The fibrous strip or wick 500 may also be impregnated with an aqueous suspension comprising matrix precursor particles.

[0078] The fibrous strip or roving 500 may be conveyed by a conveying element 81 to a pressure application element 82 located on the side of the draping surface Si 00 , S 200 , S 300 The conveying element 81 is here in the form of a pair of counter-rotating rollers 81a and 81b between which the belt or the wick 500 is present. The conveying element 81 allows the strip or wick 500 to be advanced to the pressure application element 82. The pressure application element 82 applies pressure to the strip or wick 500 in order to produce a deposit on the lay-up surface Swo, S 2O bone 300 The pressure application element 82 is here in the form of a roller.

[0079] The deposition head 80 may, furthermore, comprise a heating element 83 located in the vicinity of the pressure application element 82. This heating element 83 makes it possible, in the case of a strip or wick 500 impregnated with a thermoplastic or thermosetting polymer, to heat the impregnated strip or wick 500 during its deposition in order to fluidify the polymer and thus to confer the desired adhesive power to the strip or wick 500 deposited.

[0080] During deposition, the deposition head 80 is movable in order to apply the strip or wick 500 to a first determined area, the draping surface Swo, S 2O o, S3oo- Once the application has been carried out on this first zone, a cutting element 84 of the depositing head 80 cuts the strip or the wick 500. After this cutting, the deposit of a first fibrous structure is thus obtained, formed by a first section of the strip or the wick 500, on the draping surface Swo, S 200 , S 300 .

[0081] The formation of the fiber blank 510, 520, 530 is then continued by advancing the strip or roving 500 in the deposition head 80 to the pressure application element 82 by actuation of the conveying element 81. The deposition head 80 can be moved in order to deposit the roving or strip 500 on a second zone, the draping surface Swo, S 2O bone 300. The deposition of a second fibrous structure, formed by a second section of the strip 500, on the second zone of the draping surface Swo, S2oo, S 300 is then obtained in a manner similar to that described previously.

[0082] The production of the fiber blank 510, 520, 530 is then continued by depositing several other fiber structures in the same manner as described previously. One or more pre-impregnated plies are thus produced on the draping surface Swo, S 2O bone 3O o- The plies are preferably pre-impregnated with a resin, as described above, for example with a thermosetting polymer or with a thermoplastic polymer.

[0083] We then obtain the fiber blanks 510, 520, 530 produced by draping as illustrated in figures 4 to 6.

[0084] A plurality of fiber sub-preforms 51, 52, 53 are produced by thermoforming the fiber blanks 510, 520, 530.

[0085] All the fiber blanks 510, 520, 530 can be produced and then, when all the fiber blanks have been produced, they can be thermoformed to obtain the fiber sub-preforms 51, 52, 53. It is also possible to thermoform one or more fiber blanks into fiber sub-preforms before all the fiber blanks have been produced.

[0086] The first fiber sub-preform 51 is produced by thermoforming the first fiber blank 510 on a first thermoforming surface Sio. The first thermoforming surface Sw may comprise a sub-body area 10a and a sub-flange area 10b inclined relative to the sub-body area 10a. The sub-body area 10a of the first thermoforming surface Sio has the geometry of the sub-body 51a of the first sub-preform 51 to be obtained. Thus, the body portion 510a of the first fiber blank 510 is intended to be thermoformed against the sub-body area 10a of the first thermoforming surface Sio to form the sub-body 51a of the first sub-preform 51. The sub-flange area 10b of the first thermoforming surface Sio has the geometry of the sub-flange 51b of the first sub-preform 51 to be obtained.The flange portion 510b of the first fiber blank 510 is intended to be thermoformed against the sub-flange area 10b of the first thermoforming surface Sio to form the sub-flange 51b of the first sub-preform 51. Thus, the thermoforming of the first fiber blank 510 is carried out by placing the external face 510e of said first fiber blank 510 against the first thermoforming surface Sio.

[0087] The second fiber sub-preform 52 is made by thermoforming the second fiber blank 520 on a second thermoforming surface S2o. The second thermoforming surface S2o may comprise a sub-body area 20a and a sub-flange area 20b inclined relative to the sub-body area 20a. The sub-body area 20a of the second thermoforming surface S20 presents the geometry of the sub-body 52a of the second sub-preform 52 to be obtained. Thus, the body portion 520a of the second fiber blank 520 is intended to be thermoformed against the sub-body area 20a of the second thermoforming surface S2o to form the sub-body 52a of the second sub-preform 52. The sub-flange area 20b of the second thermoforming surface S2o presents the geometry of the sub-flange 52b of the second sub-preform 52 to be obtained. The flange portion 520b of the second fiber blank 520 is intended to be thermoformed against the sub-flange area 20b of the second thermoforming surface S20 to form the sub-flange 52b of the second sub-preform 52. Thus, the thermoforming of the second fiber blank 520 is carried out by placing the external face 520e of said second fiber blank 520 against the second thermoforming surface S2o-

[0088] The third fiber sub-preform 53 is produced by thermoforming the third fiber blank 530 on a third thermoforming surface S30. The third thermoforming surface S 30 may comprise a sub-body area 30a and a sub-flange area 30b inclined relative to the sub-body area 30a. The sub-body area 30a of the third thermoforming surface S 30 presents the geometry of the sub-body 53a of the third sub-preform 53 to be obtained. Thus, the body portion 530a of the third fiber blank 530 is intended to be thermoformed against the sub-body area 30a of the third thermoforming surface S 30to form the sub-body 53a of the third sub-preform 53. The sub-flange area 30b of the third thermoforming surface S3o has the geometry of the sub-flange 53b of the third sub-preform 53 to be obtained. The flange portion 530b of the third fiber blank 530 is intended to be thermoformed against the sub-flange area 30b of the third thermoforming surface S3o to form the sub-flange 53b of the third sub-preform 53. Thus, the thermoforming of the third fiber blank 530 is carried out by placing the external face 530e of said third fiber blank 530 against the third thermoforming surface S3Q.

[0089] Preferably, the draping surfaces Sw, S20, S30 are convex while the thermoforming surfaces Si 00 , S 2O bone 300 are concave, in order to improve the final material health obtained for the fibrous sub-preforms 51, 52, 53.

[0090] Thermoforming surfaces S10, S2o, S 30 may each belong to a separate thermoforming mold. However, according to a particular embodiment of the invention and as in the example illustrated in FIGS. 7 to 10, the thermoforming of the fibrous blanks 510, 520 and 530 may be carried out on a single thermoforming mold 30.

[0091] In this embodiment, as illustrated in Figure 8, a fiber blank - here the third fiber blank 530 - is thermoformed directly on the thermoforming mold 30. The third thermoforming surface S3o therefore belongs to the thermoforming mold 30. Then, the other fiber blanks - here the second blank 520 then the first blank 510 - are thermoformed on the previously obtained fiber sub-preform 53, 52 still arranged on the thermoforming mold 30, as illustrated in Figures 9 and 10. Thus, the second thermoforming surface S2o is formed by the internal face 53i of the third fiber sub-preform 53 still arranged on the thermoforming mold 30, and the first thermoforming surface S10 is formed by the internal face 52i of the second fiber sub-preform 52 still arranged on the thermoforming mold 30.

[0092] Thermoforming parameters such as temperature, kinematics and speed are determined in a manner well known to those skilled in the art depending on the type of pre-impregnated plies used.

[0093] According to a third step E3, the stacking of the fiber sub-preforms 51, 52, 53 is carried out.

[0094] In the preferred embodiment as illustrated in Figures 8 to 10, the stacking of the fiber sub-preforms 51, 52, 53 is actually carried out on the thermoforming mold 30.

[0095] Otherwise, the stacking of the fiber sub-preforms 51, 52, 53 is carried out after thermoforming, as described previously. The stacking can be carried out by an automated effector, for example by an automated “pick and place” type effector.

[0096] The stacking of the fiber sub-preforms 51, 52, 53 forms the fiber preform 50 of the part 5 to be obtained.

[0097] The fibrous preform 50 thus obtained is then polymerized in a well-known manner so as to consolidate said preform 50 to obtain the part 5 made of composite material according to a fourth step E4. The invention is particularly interesting when the part 5 to be obtained is a part made of composite material with an organic matrix.

Claims

Claims

1. Method for manufacturing a part (5) made of composite material comprising the following steps: - the production of a first fiber blank (510) by draping one or more first pre-impregnated plies on a first draping surface (Si 00 ), - producing a first fibrous sub-preform (51) by thermoforming the first fibrous blank (510) on a first thermoforming surface (Sio), - producing at least one second fiber blank (520) by draping one or more second pre-impregnated plies on a second draping surface (S200) different from the first draping surface (S100), - producing at least one second fibrous sub-preform (52) by thermoforming the second fibrous blank (520) on a second thermoforming surface (S 20 ) different from the first thermoforming surface (S 20 ), - stacking the fibrous sub-preforms (51, 52, 53) so as to obtain a fibrous preform (50) having the shape of the part (5) to be obtained, - consolidation of the fibrous preform (50) so as to form a matrix so as to obtain the part (5) made of composite material.

2. A manufacturing method according to claim 1, wherein the layups are performed by an automated layup process.

3. A manufacturing method according to claim 1 or 2, wherein the fibrous blanks (510, 520, 530) are pre-impregnated with a resin.

4. A manufacturing method according to any one of claims 1 to 3, wherein the draping surfaces (S100, S200, S300) are convex and the thermoforming surfaces are concave (S10, S 20 , S 30 ).

5. A manufacturing method according to any one of claims 1 to 4, wherein the first thermoforming surface (Sio) is formed by the second fibrous preform (52) disposed on the second thermoforming surface (S 20 ).

6. A manufacturing method according to any one of claims 1 to 5, wherein the layup surfaces (Si 00 , S2oo, S 300) comprise at least one end zone having undulations (100b, 200b, 300b), such that the portion of the fibrous blanks (510, 520, 530) formed on said end portion having undulations (100b, 200b, 300b) is deformed during thermoforming so as to produce at least one sub-flange (51b, 52b, 53b) of fibrous sub-preform (51, 52, 53), the stacking of the sub-flanges of fibrous sub-preform (51, 52, 52) producing at least one fibrous preform flange (50) intended to form at least one flange (5b) on the final part (5).

7. Manufacturing method according to any one of claims 1 to 6, further comprising a preliminary step (Ei) of determining the number (N) of fiber sub-preforms (51, 52, 53) to be produced, according to which the minimum number (N mini) stacked fibrous sub-preforms (51, 52, 53) to be produced so that the probability of a forming defect occurring during the thermoforming of a fibrous sub-preform (51, 52, 53) is less than a determined probability value (p r ef).

8. A manufacturing method according to claim 7, wherein the probability value (p r ef) determined is 1CT 9 .

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