Method of manufacturing an aeronautical frame made of composite material for an aircraft fuselage

Abstract

A method for manufacturing an aeronautical frame comprising steps of forming a blank part (1P) extending rectilinearly along a neutral axis (Xn), the blank part (1P) comprising a plurality of plies superimposed along a stacking axis (Ze), each ply comprising a plurality of rectilinear reinforcing fibers impregnated with a resin, the blank part (1P) comprising plies at 0° (Pa) oriented at 0° relative to the neutral axis (Xn), at least one ply at 0° (Pa) comprising discontinuous longitudinal fibers, inclined plies (Pc) oriented between [a1, a2] relative to the neutral axis (Xn), a1 being between [-70°; -50°], a2 being between [50°; 70°], bend the rough part (1P) according to a bending radius and then consolidate the curved rough part (1P) to obtain the aeronautical frame. Abstract figure: Figure 8

Description

Title of the invention: Method for manufacturing an aeronautical frame made of composite material for an aircraft fuselage Technical field

[0001] The present invention relates to the field of manufacturing aeronautical frames for forming a fuselage of an aircraft.

[0002] In a known manner, with reference to [Fig. 1], an aircraft comprises a fuselage 200 on which the wings are mounted in particular. The fuselage 200 extends longitudinally along a fuselage axis Xf and comprises an outer skin 300 which is stiffened by a plurality of aeronautical frames 101 extending orthogonally to the fuselage axis Xf and by a plurality of stringers 102 extending parallel to the fuselage axis Xf. In a known manner, a fuselage 200 has a circular or ovoid section. Also, with reference to [Fig. 2], an aeronautical frame 101 has a curved overall shape. An aeronautical frame 101 comprises a core 110, also called a “web”, and a sole 120, which is angled relative to the core 110, also called an “outer flange”, and configured to be attached to an inner surface of the outer skin 300 of the fuselage 200.In this example, the aeronautical frame 101 also comprises a heel 121, which is bent relative to the core 10, also called an “inner flange”. Preferably, the sole 120 and the heel 121 extend in opposite directions relative to the core 110 as illustrated in [Fig.2]. An aeronautical frame 101 thus has a complex shape.

[0003] In practice, as illustrated in [Fig.2], an aeronautical frame 101 has a radius of curvature R, an angular opening a, a height H of the core 110 and a height S of the sole 120. An aeronautical frame 101 is traditionally made of metallic material. In order to reduce the mass of the fuselage 200, it has been proposed to make an aeronautical frame 101 of composite material.

[0004] To form an aeronautical part made of composite material, it is known to use plies comprising rectilinear reinforcing fibers impregnated with thermosetting resin. In order for the aeronautical part to have optimal mechanical characteristics, it is important that the number of reinforcing fibers is substantially constant in the aeronautical part.

[0005] A difficulty exists for an aeronautical frame 101 due to its overall curved shape. An ideal solution would be to position curved plies, i.e. with reinforcing fibers arranged in a curved manner, to form the core 110 but also the sole 120. Such a manufacturing method has a very low yield and does not guarantee the manufacture of aeronautical frames 101 with homogeneous characteristics.

[0006] To eliminate this drawback, with reference to [Fig. 3], it has been proposed in the prior art to implement a manufacturing method comprising steps consisting of forming a rough part 10IP extending rectilinearly along a neutral axis Xn.

[0007] It is known that the blank part 101P comprises a core 110P and a sole 120P bent relative to the core 110P, the blank part 101P comprising a plurality of plies, each ply comprising a plurality of rectilinear reinforcing fibers impregnated with a thermosetting or thermoplastic resin. In order to obtain significant mechanical strength, the blank part 10IP comprises: • 0° folds PA which are oriented at 0° relative to the neutral axis Xn, also called neutral folds, • 90° folds PB which are oriented at 90° relative to the neutral axis Xn, also called perpendicular folds, • inclined folds Pc which are oriented between [-45°; +45°] relative to the neutral axis Xn.

[0008] The plies PA, PB, Pc are stacked along a stacking axis Ze. The manufacturing method comprises a step consisting of bending the blank part 10IP according to a bending radius R (corresponding to the desired radius of curvature R of the aeronautical frame 101) then consolidating the bent blank part 10IP to obtain the aeronautical frame 101.

[0009] In practice, the bending step modifies the orientation of the reinforcing fibers, which affects its mechanical strength. This is particularly the case for 0° PA folds which are heavily stressed during bending. To eliminate this drawback, it has been proposed in the prior art to remove them.

[0010] Furthermore, not all aeronautical frames 101 have the same radius of curvature depending on their position in the fuselage, in particular, if they are located in a wide or narrow section. When the radius of curvature R is small, in particular when the ratio of the radius of curvature R to the height of the core H is less than 17 (R / H<17), it has been observed that the 90° folds PB have unwanted undulations. To eliminate this drawback, one solution would be to remove them, but it is then complex to manufacture an aeronautical frame 101 having sufficient mechanical strength.

[0011] The invention thus aims to eliminate at least some of these drawbacks by proposing a new method for manufacturing aeronautical frames made of composite material which is particularly suitable when the radius of curvature R over the height of the core H is less than 17 (R / H<17). PRESENTATION OF THE INVENTION

[0012] The invention relates to a method for manufacturing an aeronautical frame made of composite material for an aircraft fuselage, the frame comprising a core and a sole configured to be fixed to an outer skin of the aircraft fuselage, the manufacturing method comprising steps consisting of: • Forming a blank part extending rectilinearly along a neutral axis, the blank part comprising a plurality of plies superimposed along a stacking axis, each ply comprising a plurality of rectilinear reinforcing fibers impregnated with a resin, the blank part comprising: • 0° folds oriented at 0° relative to the neutral axis, at least one 0° fold comprising discontinuous longitudinal fibers, • inclined folds oriented between [al, a2] relative to the neutral axis, al being between [-70°; -50°], a2 being between [50°; 70°], • Bend the rough part according to a bending radius then • Consolidate the curved rough part to obtain the aeronautical frame.

[0013] Thanks to the invention, discontinuous longitudinal fibers at 0° are advantageously provided in a rough part to absorb mechanical stresses. This makes it possible to avoid degradation of said fibers during bending. The presence of inclined folds makes it possible to reinforce the aeronautical frame while making it possible to omit 90° folds which would be liable to be damaged depending on the desired radius of curvature.

[0014] According to one aspect, the folds of the rough part are made up, for the part forming the core: • 0° folds oriented at 0° relative to the neutral axis, at least one 0° fold comprising discontinuous longitudinal fibers, and • inclined folds oriented between [al, a2] relative to the neutral axis, al being between [-70°; -50°], a2 being between [50°; 70°].

[0015] According to one aspect, the plies of the blank part are made of carbon.

[0016] According to a particular aspect, the rough part is covered at its ends by glass folds. This improves galvanic isolation.

[0017] According to one aspect, the folds of the rough part are made up of: • 0° folds oriented at 0° relative to the neutral axis, at least one 0° fold comprising discontinuous longitudinal fibers, and • inclined folds oriented between [al, a2] relative to the neutral axis, al being between [-70°; -50°], a2 being between [50°; 70°].

[0018] According to one aspect, the rough part comprises: • At least one first 0° fold comprising discontinuous longitudinal fibers defining cuts spaced apart according to a first pattern, • At least one second 0° ply comprising discontinuous longitudinal fibers defining cuts spaced apart according to a second pattern, the second 0° ply being superimposed on the first 0° ply in the rough part, the first pattern and the second pattern being offset in projection according to the stacking axis.

[0019] The offset of the patterns, that is to say the offset of the cuts, makes it possible to avoid creating weak zones in the thickness of the rough part.

[0020] According to one aspect, the rough part further comprises at least one third 0° fold comprising discontinuous longitudinal fibers defining cutouts spaced apart according to a third pattern, the first pattern, the second pattern and the third pattern being offset in projection according to the stacking axis.

[0021] According to one aspect, the rough part further comprises at least a fourth 0° fold comprising discontinuous longitudinal fibers defining cutouts spaced apart according to a fourth pattern, the first pattern, the second pattern, the third pattern and the fourth pattern being offset in projection according to the stacking axis.

[0022] According to one aspect, all of the 0° plies forming the core of the frame comprise discontinuous longitudinal fibers.

[0023] According to one aspect, all of the 0° plies of the frame comprise discontinuous longitudinal fibers. In other words, the core, the sole and possibly a heel comprise only 0° plies comprising discontinuous longitudinal fibers.

[0024] According to one aspect, the aeronautical frame having a radius of curvature and a height H of the web, the ratio of the radius of curvature to the height of the web is less than 17.

[0025] According to one aspect, the blank part does not comprise folds oriented between [80°; 100°], preferably folds at 90°.

[0026] According to one aspect, a1 is between [-65°; -55°] and a2 is between [55°; 65°].

[0027] According to one aspect, the blank part comprises at least one pair of adjacent plies inclined having opposite orientations, in particular, a first fold inclined at +al° and a second fold inclined at -al°.

[0028] According to one aspect, the blank part comprises at least three pairs of adjacent inclined folds having opposite orientations.

[0029] In one aspect, the 0° fold comprising discontinuous longitudinal fibers, each discontinuous longitudinal fiber comprising continuous segments having a maximum length of 175mm, preferably 150mm. In one aspect, each discontinuous longitudinal fiber comprising continuous segments having a minimum length of 100mm.

[0030] According to one aspect, the cutouts are distributed substantially uniformly in their 0° fold in order to avoid superposition or juxtaposition of cutouts. Preferably, the cutouts are spaced substantially the same distance apart, here, in a plane. The cutouts are spaced evenly.

[0031] According to one aspect, the cutouts are distributed substantially uniformly in the thickness of the rough part. Preferably, it is understood that the cutouts are spaced substantially the same distance apart, here, in a three-dimensional manner. PRESENTATION OF THE FIGURES

[0032] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0033] [Fig.l] is a schematic representation of an aircraft fuselage comprising an outer skin, stringers and aeronautical frames according to the prior art.

[0034] [Fig.2] is a schematic representation of an aeronautical frame according to the prior art after its manufacture.

[0035] [Fig. 3] is a schematic representation of a manufacturing method according to the prior art.

[0036] [Fig.4] is a schematic representation of an aircraft fuselage comprising an outer skin, stringers and aeronautical frames according to the invention.

[0037] [Fig.5] is a schematic representation of an aeronautical frame according to the invention after its manufacture.

[0038] [Fig.6] is a schematic representation of the steps of a method of manufacturing an aeronautical frame according to the invention.

[0039] [Fig.7] is a schematic representation of a step in forming a rough part.

[0040] [Fig.8] is a schematic representation of a superposition of plies to form the core of the rough part.

[0041] [Fig.9] is a schematic representation from above of a first fold at 0° with cuts distributed according to a first pattern.

[0042] [Fig. 10] is a schematic representation from above of a second 0° fold with cuts distributed according to a second pattern.

[0043] [Fig. 11] is a schematic representation of the superimposed cutouts of the first fold and the second fold.

[0044] [Fig. 12] is a schematic representation of the rough part after bending, in particular, of the first bend at 0°.

[0045] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0046] The invention will be presented for the production of an aeronautical frame to form the fuselage of an aircraft.

[0047] In a known manner, with reference to [Fig. 4], an aircraft comprises a fuselage 200 on which the wings are mounted in particular. The fuselage 200 extends longitudinally along a fuselage axis Xf and comprises an outer skin 300 which is stiffened by a plurality of aeronautical frames 1 extending orthogonally to the fuselage axis and by a plurality of stringers 102 extending parallel to the fuselage axis Xf.

[0048] In a known manner, a fuselage 200 has a circular or ovoid section. Also, with reference to [Fig. 5], an aeronautical frame 1 has a curved overall shape. An aeronautical frame 1 comprises a core 10, also called a “web”, and a sole 20, which is bent relative to the core 10, also called an “outer flange”, and configured to be fixed to an inner surface of the outer skin 300 of the fuselage 200. In this example, the aeronautical frame 1 also comprises a heel 21, which is bent relative to the core 10, also called an “inner flange”. Preferably, the sole 20 and the heel 21 extend in opposite directions relative to the core 10 as illustrated in [Fig. 5]. An aeronautical frame 1 thus has a complex shape.

[0049] The invention is presented for an aeronautical frame having an L-shaped section but it applies to any type of section, in particular, having a Z-shaped or C-shaped section.

[0050] In practice, as illustrated in [Fig.5], an aeronautical frame 1 has a radius of curvature R, an angular opening a, a height H of the web 10 and a height S of the sole 20. According to a preferred aspect, the radius of curvature R is between 1000 and 2500. According to a preferred aspect, the height H of the web 10 is between 60mm and 150mm. According to a preferred aspect, the height S of the sole 20 is between 15mm and 40mm.

[0051] Preferably, the ratio of the radius of curvature R to the height H of the core 10 is between 14 and 17. The invention thus applies when the ratio of the radius of curvature R to the height of the core H is less than 17 (R / H<17).

[0052] An example of implementation of a method for manufacturing an aeronautical frame made of composite material for an aircraft fuselage will now be presented with reference to [Fig.6].

[0053] Generally speaking, the manufacturing method comprises steps consisting of: • Forming SI a rough part IP extending rectilinearly along a neutral axis Xn, then • Bend S2 the rough part IP according to a bending radius R then • Consolidate S3 the curved IP rough part to obtain the aeronautical frame 1.

[0054] Form (SI) a rough part IP

[0055] With reference to [Fig.7], the method comprises a step SI consisting of forming a rough part IP extending rectilinearly along a neutral axis Xn. The rough part IP is flat and will be bent subsequently so as to form the core 10 and the sole 20 and, in general, the heel 21. The formation of the part of the rough part IP intended to form the core 10 will be presented below.

[0056] With reference to [Fig.8], the blank part IP comprises a plurality of plies superimposed along a stacking axis Ze (perpendicular to the neutral axis Xn). Preferably, the number of superimposed plies is between 10 and 20. In this example, a superposition of 14 plies is shown.

[0057] Each ply comprising a plurality of rectilinear reinforcing fibers impregnated with a resin. The reinforcing fibers may be of different natures, in particular, glass or carbon. Similarly, the resin may be of different natures, in particular, a thermoplastic or thermosetting resin.

[0058] The rough part IP comprises 0° folds PA oriented at 0° relative to the neutral axis Xn.

[0059] The blank part IP further comprises inclined folds Pc which are oriented between [al, a2] relative to the neutral axis Xn. Preferably, al is between [-70°; -50°], preferably between [-65°; -55°]. According to a preferred aspect, al is equal to -60°. a2 is between [50°; 70°], preferably between [55°; 65°]. According to a preferred aspect, a2 is equal to 60°. Such a high inclination is particularly advantageous when the blank part IP does not comprise 90° folds. Indeed, as presented previously, such 90° folds have unwanted undulations when the ratio of the radius of curvature R to the height of the core H is less than 17 (R / H<17).

[0060] The portion of the blank part IP intended to form the heel or the sole comprises 0° folds PA and inclined folds Pc. Preferably, all the 0° folds PA comprise discontinuous longitudinal fibers. The formation of the portion of the blank part IP intended to form the core 10 comprising only 0° folds PA and inclined folds Pc will be presented in detail. In other words, the blank part IP does not comprise 90° folds.

[0061] Preferably, with reference to [Fig. 8], the blank part IP comprises at least one pair PR1, PR2, PR3, PR4 of adjacent inclined plies Pc having opposite orientations, in particular, a first ply inclined at +al° and a second ply inclined at -al°. Preferably, the blank part IP comprises at least three pairs PR1, PR2, PR3 of adjacent inclined plies Pc having opposite orientations, plies at 0° PA are interposed between the first pair PR1 and the second pair but also between the second pair PR2 and the third pair PR3 as illustrated in [Fig. 8]. In this example, the blank part IP comprises four pairs PR1, PR2, PR3, PR4 of adjacent inclined folds Pc having opposite orientations.

[0062] According to the invention, at least one 0° fold PA comprises discontinuous longitudinal fibers. Thus, a discontinuous longitudinal fiber comprises an alternation of continuous segments S as illustrated in [Fig.9]. Preferably, a discontinuous longitudinal fiber is obtained by cutting a continuous longitudinal fiber into continuous segments S. Preferably, a 0° fold PA preferably comprises continuous segments S having a maximum length of 175mm, preferably 150mm. Preferably, the continuous segments S have a minimum length of 20mm, preferably 25mm.

[0063] Preferably, the blank part IP comprises at least 4 plies at 0° PA comprising discontinuous longitudinal fibers, preferably at least 6 as illustrated in [Fig.8].

[0064] Subsequently, a pattern is defined for each 0° PA ply comprising discontinuous longitudinal fibers. A pattern corresponds to the distribution of the cuts in said 0° PA ply as illustrated in [Fig.9].

[0065] With reference to [Fig. 9], there is shown along the stacking axis Ze a first ply at 0° Pa(M1) comprising a plurality of longitudinal fibers which each comprise at least one first cut D1. The first cuts DI together define a first pattern M1. Similarly, with reference to [Fig. 10], there is shown along the stacking axis Ze a second ply at 0° PA(M2) comprising a plurality of longitudinal fibers which each comprise at least one second cut D2. The second cuts D2 together define a second pattern M2.

[0066] Preferably, the cutouts D1, D2 are distributed substantially uniformly in their 0° fold PA(M1), PA(M2). Preferably, it is understood that the cutouts are spaced substantially the same distance apart in a three-dimensional manner. This makes it possible to avoid concentrating areas of weakness in a 0° fold.

[0067] Preferably, the blank part IP comprises several 0° PA plies comprising discontinuous longitudinal fibers, preferably at least 6 0° P plies A as illustrated in [Fig.8]. Preferably, all the 0° PA plies comprise discontinuous longitudinal fibers. The blank part IP does not comprise any 0° PA plies comprising continuous longitudinal fibers.

[0068] In the example of [Fig.8], the rough part IP comprises: • a first pair PR1 of adjacent inclined folds Pc, • a first ply at 0° PA(M1) comprising discontinuous longitudinal fibers defining cutouts spaced apart according to a first pattern Ml, • a second 0° PA(M2) ply comprising discontinuous longitudinal fibers defining spaced cuts according to a second pattern M2, • a second pair PR2 of adjacent inclined folds Pc, • a third 0° PA(M3) ply comprising discontinuous longitudinal fibers defining spaced cuts according to a third pattern M3, • a fourth 0° PA(M4) ply comprising discontinuous longitudinal fibers defining spaced cuts according to a fourth M4 pattern, • a third pair PR3 of adjacent inclined folds Pc, • a fifth 0° PA(M5) ply comprising discontinuous longitudinal fibers defining spaced cuts according to a fifth M5 pattern, • a sixth 0° PA(M6) ply comprising discontinuous longitudinal fibers defining spaced cuts according to a sixth M6 pattern and • a fourth pair PR4 of adjacent inclined folds Pc.

[0069] The 0° folds PA(M1), PA(M2), PA(M3), PA(M4), PA(M5), PA(M6) are superimposed in the rough part IP along the stacking axis Ze. The patterns M1, M2, M3, M4, M5, M6 are offset in projection along the stacking axis Ze. The cutouts are advantageously offset in the thickness so as to avoid the appearance of weak zones.

[0070] As an example, with reference to [Fig.l 1], the projection of the first pattern Ml of the first ply at 0° PA(M1) and of the second pattern M2 of the second ply at 0° PA(M2) is shown. The cuts Dl, D2 are offset from each other. Thus, there is no weak zone in the thickness which is linked to the alignment of cuts.

[0071] Preferably, the 0° fold cuts PA(M1), PA(M2), PA(M3), PA(M4), PA(M5), Pa(M6) are distributed in a substantially uniform manner in the rough part IP, i.e., in a three-dimensional manner. This makes it possible to avoid concentrating weak areas.

[0072] Bend (S2) the rough part

[0073] With reference to [Fig. 12], the blank part IP is positioned in a bending machine so that the blank part IP has the desired radius of curvature R. The bending step S2 ([Fig.6]) does not damage the blank part IP since it remains flexible due to the presence of unconsolidated resin between the reinforcing fibers.

[0074] The presence of the cutouts D1, D2 in the 0° folds PA advantageously makes it possible to avoid the formation of mechanical tensions on the reinforcing fibers of the 0° folds. With reference to [Fig. 12], following bending, the segments S of the first 0° fold PA are spaced apart by a first spacing E1 without weakening the reinforcing fibers. In practice, during the bending step, the further the segments are located outside the bending axis, the more they are spaced apart due to the bending forces. In practice, the spacing after bending between two adjacent segments S is less than 1 mm.

[0075] As the patterns M1, M2, M3, M4, M5, M6 are offset in projection along the axis Ze stacking, the cuts remain spaced apart after bending and there are no weak points in the bent IP blank part due to a very low density of reinforcing fibers.

[0076] Preferably, following the step S1 of forming the rough part IP, the method comprises a step of bending the rough part IP to form the heel 21. After the bending step S2, the method comprises a step of bending the rough part IP to form the sole 20.

[0077] Consolidate (S3) the rough part

[0078] With reference to [Fig.6], the curved IP blank part is then consolidated S3 by a method adapted to the nature of the resin. Thus, for a thermosetting resin, it is preferably heated and put under pressure, for example, with or without an autoclave. A step of consolidating an IP blank part is known to those skilled in the art and will not be presented in more detail. For a thermoplastic resin, consolidation is carried out simply by cooling.

[0079] After consolidation, an aeronautical frame 1 is obtained in composite material which can be mounted in a practical manner on an outer skin in order to form an aeronautical fuselage.

[0080] Thanks to the invention, an aeronautical frame having an overall curved shape which is free from weak zones is advantageously obtained. The invention is particularly advantageous for an aeronautical frame having an R / H ratio <17 since it makes it possible to avoid the use of 90° folds and introduce 0° folds comprising discontinuous fibers.

Claims

1.

2. Claims Method for manufacturing an aeronautical frame (1) made of composite material for an aircraft fuselage (200), the frame comprising a core (10) and a sole (20) configured to be fixed to an outer skin of the aircraft fuselage (200), the manufacturing method comprising steps consisting of: • Forming (SI) a rough part (IP) extending rectilinearly along a neutral axis (Xn), the rough part (IP) comprising a plurality of plies superimposed along a stacking axis (Ze), each ply comprising a plurality of rectilinear reinforcing fibers impregnated with a resin, the rough part (IP) comprising: • 0° folds (PA) oriented at 0° relative to the neutral axis (Xn), and at least one 0° fold (PA) comprising discontinuous longitudinal fibers, • inclined folds (Pc) oriented between [al, a2] relative to the neutral axis (Xn), al being between [-70°; -50°], a2 being between [50°; 70°], • Bend (S2) the rough part (IP) according to a bending radius (R) then • Consolidate (S3) the curved rough part (IP) to obtain the aeronautical frame (1). Manufacturing method according to claim 1, in which the rough part (IP) comprises: • At least one first 0° fold (PA(M1)) comprising discontinuous longitudinal fibers defining cuts spaced apart according to a first pattern (Ml), • At least one second 0° ply (PA(M2)) comprising discontinuous longitudinal fibers defining cuts spaced apart according to a second pattern (M2), the second 0° ply (Pa(M2)) being superimposed on the first 0° ply (PA(M1)) in the rough part (IP), the first pattern (M1) and the second pattern (M2) being offset in projection according to the stacking axis (Ze).

3. Manufacturing method according to claim 2, in which the rough part (IP) further comprises: • at least one third 0° fold (PA(M3)) comprising discontinuous longitudinal fibers defining cutouts spaced apart according to a third pattern (M3), the first pattern (M1), the second pattern (M2) and the third pattern (M3) being offset in projection according to the stacking axis (Ze).

4. Manufacturing method according to claim 3, in which the rough part (IP) further comprises: • at least one fourth 0° fold (PA(M4)) comprising discontinuous longitudinal fibers defining cutouts spaced apart according to a fourth pattern (M4), the first pattern (M1), the second pattern (M2), the third pattern (M3) and the fourth pattern (M4) being offset in projection according to the stacking axis (Ze).

5. Manufacturing method according to one of claims 1 to 4, in which all the 0° plies (PA) comprise discontinuous longitudinal fibers.

6. Manufacturing method according to one of claims 1 to 5, in which, the aeronautical frame (1) having a radius of curvature (R) and a height H of the core (10), the ratio of the radius of curvature (R) to the height of the core (H) is less than 17.

7. Manufacturing method according to one of claims 1 to 6, in which, a1 is between [-65°; -55°] and a2 is between [55°; 65°].

8. Manufacturing method according to one of claims 1 to 6, in which the blank part (IP) does not have 90° folds.

9. Manufacturing method according to one of claims 1 to 8, wherein the blank part (IP) comprises at least one pair (PR1, PR2, PR3, PR4) of adjacent inclined folds (Pc) having opposite orientations, in particular, a first inclined fold (Pc) at +al° and a second inclined fold (Pc) at -al°.

10. Manufacturing method according to claim 9, wherein the blank part (IP) comprises at least three pairs (PR1, PR2, PR3, PR4) of adjacent inclined plies (Pc) having opposite orientations.

11. Manufacturing method according to one of claims 1 to 10, in which the 0° fold (PA) comprising discontinuous longitudinal fibers, each discontinuous longitudinal fiber comprising continuous segments (S) having a maximum length of 175mm, preferably 150mm.

12. Manufacturing method according to one of claims 2 to 11, in which the cutouts (D1, D2) are distributed substantially uniformly in their fold at 0° PA(M1), PA(M2).

13. Manufacturing method according to one of claims 2 to 12, in which the cutouts (D1, D2) are distributed substantially uniformly in the thickness of the rough part (IP).

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