Method for manufacturing a hollow blade / vane or a hollow propeller blade made of an organic matrix composite material

Abstract

The invention relates to a method for manufacturing a blade or vane made of composite material, comprising: - obtaining (E10) an insert, comprising the production of a fibrous stack having a predetermined fibrous orientation by an automatic fiber placement technique, the composite insert comprising said fibrous stack impregnated with a thermosetting polymer, - obtaining (E12) a porous fibrous reinforcement obtained by three-dimensional weaving and having a disconnection defining two disconnected fibrous portions, - obtaining (E20) a fibrous assembly by introducing the insert inside the porous fibrous reinforcement, the insert thus introduced giving its shape to the reinforcement, - introducing (E30) a thermosetting resin into the porous fibrous reinforcement after the fibrous assembly has been obtained, and - co-curing (E40) the thermosetting resin thus introduced with the thermosetting polymer.

Description

Description Title of the invention: Method for manufacturing a hollow blade or a hollow propeller blade from an organic matrix composite material Technical Field

[0001] This presentation concerns a manufacturing process for a hollow blade or hollow propeller blade made of organic matrix composite material which allows the mechanical and vibrational performance of the part to be adapted according to the intended application, without penalizing its mass. Previous technique

[0002] The use of composite materials allows for the production of lighter turbomachine blades or propeller blades compared to those made from metal. Their use contributes to optimizing turbomachine performance, particularly by reducing the overall mass of the turbomachine, thereby lowering fuel consumption, which in turn leads to a reduction in harmful emissions (CO, CO2, NO). X ...).

[0003] Increasing the size of propeller blades or vanes can be a goal in order to improve engine performance, making the control of the mass of the components involved all the more important. One solution to achieve this is to use hollow parts made of composite material.

[0004] Reducing the mass of these parts requires optimizing the structure of the material(s) according to the stress conditions and the main stress paths encountered in the application. It is desirable to have new manufacturing processes for blades and propellers that allow for the best possible adaptation of the mechanical and vibrational performance of the part to the intended application, without compromising its mass. EP2516263, which describes an aircraft propeller blade, and US2009008836, which describes a manufacturing process for fibrous composite elements, are known. Description of the invention

[0005] This presentation relates to a process for manufacturing a hollow blade or a hollow propeller blade from an organic matrix composite material, comprising: - obtaining a composite insert, comprising the production, by automated fiber placement technique, of a fiber stack having a predetermined fiber orientation, the composite insert comprising said fiber stack impregnated by a thermosetting polymer in its raw or partially cured state, - obtaining a porous fibrous reinforcement produced by three-dimensional weaving and having a debonding defining two debonded fibrous portions that can be separated from each other, - obtaining a fibrous assembly by introducing the composite insert inside the porous fibrous reinforcement by separating the debonded fibrous portions at the debonding point, the composite insert thus introduced giving its shape to the reinforcement, - the introduction of a thermosetting resin into the porous fibrous reinforcement after obtaining the fibrous assembly, and - the co-curing of the thermosetting resin thus introduced with the thermosetting polymer.

[0006] The present invention proposes a method for manufacturing a hollow blade or a hollow propeller blade having a hybrid fibrous reinforcement comprising, on the one hand, a three-dimensional fabric in the outer part defining the aerodynamic profile and, on the other hand, a fibrous stack with a specific fiber orientation in the inner part of the blade or propeller blade. The invention further proposes to produce the stack forming the reinforcement of the insert using an automated fiber placement (AFP) technique, which makes it possible to parameterize the fibrous orientation of the stack according to the expected stresses for the intended application in order to give the part the desired mechanical performance, particularly in terms of bending and torsion, and vibration.The invention significantly improves the performance of the component compared to cases where the reinforcement is solely composed of three-dimensional fabric, without increasing its mass, by actually reducing it. Co-curing allows the thermosetting resin, introduced into the reinforcement, to polymerize with the thermosetting polymer impregnating the fiber stack. This creates covalent bonds between the polymer chains present, resulting in the bonding of the insert and the reinforcement.

[0007] In one embodiment, the fiber stack is formed by several layers of unidirectional fibers oriented at an angle between -10° and +10°, for example between -5° and +5°, with respect to a radial direction of the blade or propeller blade.

[0008] Such a characteristic advantageously allows obtaining a part whose mechanical performance in bending is optimized.

[0009] Alternatively, the fiber stack comprises at least (a) a first layer of unidirectional fibers oriented at a first angle between -55° and -35° by (b) a second layer of unidirectional fibers oriented at a second angle between +35° and +55° with respect to the radial direction.

[0010] Such a characteristic advantageously improves the performance of the part in torsion compared to the case where the reinforcement is solely formed by the three-dimensional fabric.

[0011] Specifically, the first angle can be between -50° and -40° with respect to the radial direction, and the second angle can be between +40° and +50° with respect to the radial direction. More specifically, the first angle can be between -46° and -44° with respect to the radial direction, and the second angle can be between +44° and +46° with respect to the radial direction.

[0012] In particular, fibrous packing can be quasi-isotropic. A quasi-isotropic packing corresponds to a packing with an orientation [0 o +45° / 90 o / -45 o ] n with respect to the radial direction, with n an integer greater than or equal to 1.

[0013] Such a characteristic makes it possible to further improve the performance of the part, in particular its compression and tensile properties as well as its properties in the thickness direction (between the intrados and extrados).

[0014] In particular, the stacking may include, in succession in this order along the thickness of the composite insert: - a plurality of first layers of unidirectional fibers oriented with the first angle between -55° and -35°, for example between -50° and -40° or between -46° and -44°, with respect to the radial direction, - one or more interlayers of unidirectional fibers oriented at an angle between 80° and 100°, for example between 85° and 95° or between 89° and 91°, with respect to the radial direction, - a plurality of second layers of unidirectional fibers oriented at a second angle between +35° and +55°, for example between +40° and +50° or between +44° and +46°, with respect to the radial direction, and - one or more additional layers of unidirectional fibers oriented at an angle between -10° and +10°, for example between -5° and +5° or between -1° and +1°, with respect to the radial direction.

[0015] Such a characteristic advantageously makes it possible to obtain a part whose desired performance ratio between bending and torsional behavior is optimized for the intended application.

[0016] In one example, thermosetting resin is introduced into the porous fiber reinforcement by resin transfer molding. This technique is known as RTM (Resin Transfer Molding). Those skilled in the art will recognize that other techniques can be used to introduce the resin.

[0017] In one embodiment, the fibrous stack impregnated by the thermosetting polymer is present on a support form, and the obtaining of the composite insert further includes a consolidation of the fibrous stack by partial baking of the thermosetting polymer, as well as a removal or elimination of the support form, after consolidation, in order to obtain a hollow and consolidated composite insert, said hollow and consolidated composite insert being introduced inside the porous fibrous reinforcement to obtain the fibrous assembly.

[0018] In this case, the hollow insert is introduced in a consolidated state inside the fibrous reinforcement, meaning that it can be manipulated while retaining its shape without the assistance of a holding tool and that it is rigid enough to shape the reinforcement and that its shape is not affected during the subsequent introduction of the resin.

[0019] The consolidated state is achieved by partial curing of the polymer, meaning the polymer is incompletely polymerized. It can have a degree of polymerization greater than or equal to 80%, for example, between 80% and 90%. For a given polymer, the degree of polymerization can be determined by Differential Scanning Calorimetry (DSC). The degree of polymerization of the polymer is sufficient for the insert to have the desired stiffness. However, the polymerization is not complete enough to allow co-curing and thus achieve bonding of the insert to the inner surface of the reinforcement. This co-curing allows the thermosetting resin, introduced into the reinforcement, to polymerize with the incompletely polymerized polymer. This creates covalent bonds between the polymer chains present, resulting in the bonding of the insert and the reinforcement.The raw state exhibits a less advanced degree of polymerization than a consolidated state, this degree of advancement possibly being zero.

[0020] Alternatively, the fiber stacking is carried out by automatic fiber placement technique on a support form, and the composite insert is introduced inside the porous fiber reinforcement with the support form.

[0021] This situation may correspond to the case where the thermosetting polymer is in its raw state, for which the insert is unable to maintain its shape without the assistance of the support form. The support form can then be removed or discarded after co-firing, or alternatively remain in the resulting piece if it has a hollow shape.

[0022] This presentation also concerns a manufacturing process for an unfaired fan intended for mounting on an aircraft, comprising: - the manufacture of a plurality of propeller blades by implementing a process as described above, and - the mounting of said plurality of propeller blades thus manufactured on the fixing parts of a hub.

[0023] This presentation also concerns a manufacturing process for a ducted fan intended for mounting on an aircraft, comprising: - the manufacture of a plurality of blades by implementing a process as described above, and - the mounting of said plurality of blades thus manufactured on fixing parts of a hub. Brief description of the drawings [Fig. 1] Figure 1 represents a succession of steps of an example of a manufacturing process for a hollow blade or a hollow propeller blade according to the invention. [Fig. 2] Figure 2 represents, schematically and partially, the realization of a fiber stack having a predetermined fiber orientation by automatic fiber placement technique within the framework of the invention. [Fig. 3] Figure 3 schematically represents an example of a hollow blade or hollow propeller blade obtained within the framework of the invention. [Fig. 4] Figure 4 represents a view of the part of figure 3 according to IV-IV. [Fig. 5] Figure 5 represents, schematically and partially, an example of a fibrous stack that can be implemented within the framework of the invention. [Fig. 6] Figure 6 represents, schematically and partially, another example of fibrous stacking that can be implemented within the framework of the invention. [Fig. 7] Figure 7 represents, schematically and partially, another example of fibrous stacking that can be implemented within the framework of the invention. [Fig. 8] Figure 8 represents, schematically and partially, another example of fibrous stacking that can be implemented within the framework of the invention. [Fig. 9] Figure 9 represents a succession of steps of a variant of a manufacturing process for a hollow blade or a hollow propeller blade according to the invention. [Fig. 10] Figure 10 represents, schematically and partially, an example of unfaired blower that can be obtained within the framework of the invention. [Fig. 11] Figure 11 represents, schematically and partially, an example of a shrouded blower that can be obtained within the framework of the invention. Description of the implementation methods

[0024] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0025] Figure 1 illustrates a sequence of steps in an example of a manufacturing process for a hollow blade or a hollow propeller blade made of an organic matrix composite material. For the sake of brevity, the term "part" is used hereafter to refer interchangeably to the hollow blade or the hollow propeller blade. Hereafter, the term "AFP technique" refers to the automated fiber placement technique.

[0026] Step E10, relating to the example in Figure 1, concerns the fabrication of a hollow composite insert intended to be introduced in its consolidated state into the 3D woven porous fibrous reinforcement. The invention is not limited to this embodiment, since the composite insert can alternatively be introduced in its raw state, as will be explained later in connection with the variant shown in Figure 9.

[0027] Step E10 involves the fabrication, using AFP technology, of a fiber stack with a predetermined fiber orientation. The fiber stack is deposited onto a support mold. Generally, the fiber stack may already be impregnated with a thermosetting polymer at the time of its AFP deposition onto the support mold. In one variation, the fiber stack can first be deposited onto the support mold using the AFP technique, and then the thermosetting polymer can be introduced. This introduction can employ a technique known as resin transfer molding. Generally, the fiber reinforcement of the composite insert can consist of, or be primarily composed of, the fiber stack. Typically, the fiber stack is formed by a superposition of at least two layers of unidirectional fibers, which may or may not have different orientations. The fibers belonging to a unidirectional layer extend in essentially the same direction.

[0028] Figure 2 schematically illustrates the dispensing head 1 of a device for implementing an AFP technique that can be used to perform fiber stacking. The structure of the illustrated dispensing head 1 is known per se. The dispensing head 1 is fed by a fibrous strip 3, here impregnated with the thermosetting polymer. The Fiber strip 3 is a strip of unidirectional fibers that is intended to form the superimposed layers of the fiber stack.

[0029] The pre-impregnation of the fibrous strip 3 with the thermosetting polymer can be carried out using any conventional technique, for example, by dipping, roller application of the polymer, or spraying. The strip 3 can be impregnated with the thermosetting polymer before the AFP technique is implemented and then stored until this process is carried out. Alternatively, the strip is impregnated in-line with the dispensing head 1 upstream of the latter and then directly conveyed to the dispensing head 1 for stack formation by the AFP technique.

[0030] The stack is formed on the surface S by a support shape 10. The dispensing head 1 is fed by the fibrous strip 3 impregnated with the thermosetting polymer. The impregnated strip 3 is conveyed by a conveying element 5 to a pressure application element 7 located on the side of the surface S. The conveying element 5 is in the form of a pair of counter-rotating rollers 5a and 5b between which the strip 3 is positioned. The conveying element 5 advances the impregnated strip 3 to the pressure application element 7 in the direction indicated by the arrow Fl.

[0031] The pressure application element 7 applies pressure to the impregnated strip 3 to deposit it onto the surface S. The pressure application element 7 is in this case a roller. The dispensing head 1 may also include a heating element 9 located near the pressure application element 7. This heating element 9 allows, if necessary, for slight heating of the impregnated strip 3 during its deposition in order to liquefy the thermosetting polymer and thus impart the desired adhesion to the deposited strip.

[0032] During deposition, the deposition head 1 is mobile in order to apply the impregnated strip 3 to a defined area of ​​the surface S (arrow F2). Once the strip has been applied to the area, the cutting element 11 of the deposition head 1 cuts the impregnated strip 3 to obtain a first layer of unidirectional fibers with a predefined orientation. The stack formation then continues by advancing the impregnated strip 3 through the deposition head 1 to the pressure application element 7 by actuating the conveyor element 5. The deposition head 1 can be moved to deposit the strip 3 onto the first layer previously deposited to obtain a second layer of unidirectional fibers, superimposed on this first layer, with a second predefined orientation that may be identical or different from the first. orientation. The stacking is then carried out by depositing one or more other layers of unidirectional fibers with predefined orientation, in the same way as just described.

[0033] In the example considered in Figure 1, step E10 includes, after the deposition of the stack on the support form, a consolidation step during which the thermosetting polymer is partially baked so as to obtain a rigid composite insert, i.e., one capable of retaining its shape in the absence of the support form.

[0034] Generally, the thermosetting polymer can be an epoxy or a bismaleimide (BMI). Partial curing involves controlled temperature and duration, depending on the polymer used, to achieve the desired degree of polymerization. As a non-limiting example, the impregnated stack of the thermosetting polymer can undergo partial curing at a temperature between 140°C and 200°C for a duration of 30 minutes to 2 hours. It should be noted that, generally, the impregnated stack can be placed in a mold to be shaped as desired during partial curing. Partial curing can be carried out with the application of compaction pressure, for example, by placing it in an autoclave or by vacuum injection. In one variation, no compaction pressure is applied to the stack.

[0035] After the partial curing step, the support mold on which the stack was formed in step E10 is, in the example of Figure 1, removed or eliminated using techniques known per se, such as dissolution with a suitable solvent. This yields the hollow, consolidated insert comprising the stack densified by the partially cured thermosetting polymer. The stack layers can generally be superimposed along the thickness of the composite insert. The hollow insert thus defines a shape corresponding to the internal volume V of the part 1 to be obtained, as illustrated in Figure 4, which will be described later.

[0036] The process also includes the formation (step E12) of a porous fibrous reinforcement obtained by three-dimensional weaving and having a debonding that defines two debonded fibrous portions that can be separated from each other. Step E12 can take place either before or after step E10. This reinforcement is obtained by initially forming a fibrous blank by three-dimensional weaving of first yarns with second yarns, for example, using a Jacquard loom on which a bundle of weft yarns has been arranged in a plurality of layers, the weft yarns being joined by warp yarns. "Three-dimensional weaving" or "3D weaving" refers to a fabric in which at least some of the warp yarns join weft yarns over several weft layers. It should be noted, however, that within the framework of the invention, the first yarns can be warp yarns and the second yarns weft yarns, or vice versa, the roles of the warp and weft yarns being interchangeable. The weave structure of this reinforcement can, for example, be an interlock weave, although other weaves are possible. An interlock weave is defined as a weave structure in which each layer of warp yarns interlocks several layers of weft yarns with all the yarns in the same warp column having the same movement within the plane of the weave. During the weaving of the fiber blank, an unbinding is performed between two successive layers of second yarns in an unbinding zone. This unbinding allows for the definition of two unbound, unwoven fiber portions in the unbinding zone, which can be separated from one another.Specifically, in the unlinking zone, no layer of yarn from a first fiber portion is woven with a layer of yarn from a second fiber portion. In the unlinking zone, no yarn simultaneously weaves together a layer of yarn from a first portion with a layer of yarn from a second portion. The unlinked fiber portions are each obtained by three-dimensional weaving.

[0037] The next step is E20, in which the hollow, consolidated composite insert is introduced into the unbonded zone of the porous fiber reinforcement. This creates an assembly where the composite insert is inserted within the internal cavity defined by the 3D woven porous fiber reinforcement, shaping it. The composite insert is placed between the unbonded fiber portions of the porous fiber reinforcement. Generally, the fiber stack can be made of the same or a different material as the porous fiber reinforcement. Both the stack and the porous fiber reinforcement can be made of carbon fibers, glass fibers, or a mixture of such fibers.

[0038] The process continues with the densification of the porous fibrous reinforcement and the bonding of the insert to the matrix, densifying the porous fibrous reinforcement.

[0039] During step E30, the previously obtained assembly can be positioned in an injection mold that defines a molding cavity with the external shape of the part to be produced, and in which the assembly is held. Compaction pressure may or may not be applied to the assembly within the molding cavity. A thermosetting resin can then be injected to impregnate the porous fibrous reinforcement. This case corresponds to the introduction of the thermosetting resin using a resin transfer molding technique.

[0040] A final curing is then carried out by holding the assembly in the molding cavity, which, in this example, allows for the co-curing of the thermosetting resin with the partially cured thermosetting polymer. This results in the The part comprises the baked composite insert and the profile section, bonded together by covalent bonds between the polymer and the thermosetting resin (step E40). A person skilled in the art will select a thermosetting resin compatible with the polymer, either identical to it or distinct, and in the latter case, with a curing temperature range compatible with that of the polymer and chemical compatibility allowing the formation of covalent bonds during co-curing. The polymer and resin can be fully polymerized after the final curing. A spar attached to and extending from the base section can be inserted into the internal volume before placement in the molding cavity and bonded with an adhesive during the final curing.

[0041] After implementation of step E40, we obtain a part 100 of the type illustrated in figures 3 and 4.

[0042] Part 100 is made of an organic matrix composite material. It consists of two parts, 30 and 50 respectively, each also made of an organic matrix composite material, which were bonded together during co-curing. Generally, part 100 is intended for mounting on an aircraft engine.

[0043] The first part 30 defines the external portion of the part 100. The fibrous reinforcement of the first part 30 corresponds to the porous fibrous reinforcement obtained by three-dimensional weaving described above. It is densified by a first organic matrix obtained from the thermosetting resin. The first part 30 has a surface SE30 that defines an aerodynamic profile, specifically a leading edge 32 and a trailing edge 34. The first part 30 extends along a radial DR direction of the part 100 between an internal radial end 31 and an external radial end 33.

[0044] The second part 50 is distinct from the first part 30 and has a hollow shape that defines an internal volume V of the part 100. The second part 50 is located inside the first part 30. The second part 50 includes a second fibrous reinforcement comprising the fiber stack produced by the AFP technique described above. The stack is densified by a second organic matrix obtained from the thermosetting polymer. The second organic matrix may be identical or different from the first organic matrix. The second part 50 has an internal SI50 surface that defines the volume V and an external SE50 surface that is in contact with an internal SI30 surface of the first part 30. The bonding between the first 30 and the second 50 parts occurs at the interface between the SE50 and SI30 surfaces and can be ensured by covalent bonds between the first and second matrices.The second part 50, obtained after co-firing, remains in part 100 which is mounted on the aircraft engine. The layers of the stack follow one another along a stacking direction which is. transverse, for example perpendicular, to the DR direction. The stacking direction can correspond to the thickness direction of the composite insert.

[0045] The following describes, in connection with figures 5 to 8, various examples of fibrous stacks that can generally be implemented within the framework of the invention (not only in connection with the example of a process just described in connection with figure 1).

[0046] Figure 5 shows a first example of an El stack comprising several layers 51 of unidirectional fibers, each oriented at an angle of 0° with respect to the DR direction. The layers 51 are superimposed and in contact with each other. In the El stack, the layers 51 all have the same orientation with respect to the DR direction.

[0047] Figure 6 shows a second example of an E2 stacking which comprises a first layer 151 of unidirectional fibers oriented at an angle cii here equal to -45° with respect to the DR direction, and a second layer 251 of unidirectional fibers, superimposed on layer 151, oriented at an angle 02 here equal to +45° with respect to the DR direction. The second layer 251 is in contact with the first layer 151.

[0048] Figure 7 shows a third example of an E3 stacking, comprising first and second layers 151 and 251 similar to those in Figure 6, supplemented by an intercalated layer 351 of unidirectional fibers and an additional layer 51 of unidirectional fibers. The intercalated layer 351 is oriented at an angle θ3, here equal to +90°, with respect to the DR direction and is located between layers 151 and 251. Layer 351 is in contact with layers 151 and 251. The additional layer 51 is oriented at an angle θ4, here equal to 0°, with respect to the DR direction. Layer 251 is located between layer 351 and layer 51. Layer 251 is in contact with layers 351 and 51. The example in Figure 7 corresponds to a so-called quasi-isotropic fiber stacking. Along the stacking direction or in the direction of the thickness of the composite insert, we encounter, in succession in this order, layer 151, layer 351, layer 251 and layer 51.

[0049] Figure 8 shows a fourth stacking E4 which comprises, in this order in the direction of the thickness of the composite insert or along the stacking direction, a plurality of first layers 151 (here 5 layers 151), an intercalary layer 351, a plurality of second layers 251 (here 5 layers 251), and an additional layer 51. This pattern may optionally be repeated.

[0050] Figure 9 illustrates a sequence of steps in a variant of the manufacturing process for a part according to the invention. Steps E12, E20, E30, and E40 are similar to those described above. Unlike the previously described process, the composite insert obtained in step E1 comprises the raw stack still positioned on the mold. support on which the AFP deposition took place. During step E20, the composite insert is introduced into the porous fiber reinforcement along with the support form. The process may include an optional step E50 of removing or eliminating the support form after co-curing E40; step E50 is optional if the support form is hollow.

[0051] Figures 10 and 11, which will now be described, illustrate two possible applications for the parts obtained within the framework of the invention.

[0052] Thus, Figure 10 represents an open-rotor engine 1000. The engine 1000 comprises a nacelle for attachment to an aircraft fuselage and an open-rotor fan 111. The fan rotor 111 comprises a hub mounted for rotation relative to the nacelle and hollow propeller blades 101, produced by the method described above, which are attached to the hub. These blades can be mounted within a variable pitch mechanism provided in the hub. The invention is also applicable to turboprop architectures.

[0053] The variant illustrated in Figure 11 relates to a shrouded aircraft engine fan 2000 which comprises a plurality of blades 102 obtained by implementing the process described above which are located opposite a fan casing 112. An application of the part as a moving part, mounted on a shrouded or unshrouded fan rotor, has been described. However, it does not depart from the scope of the invention if the part is a static turbomachine component such as an outlet guide vane; "OGV").

[0054] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A method for manufacturing a hollow blade (102) or a hollow propeller blade (101) made of an organic matrix composite material, comprising: - obtaining (E10; Eli) a composite insert, comprising the production by automatic fiber placement technique of a fibrous stack (El; E2; E3; E4) having a predetermined fibrous orientation, the composite insert comprising said fibrous stack impregnated by a thermosetting polymer in the raw or partially cured state, - obtaining (E12) a porous fibrous reinforcement obtained by three-dimensional weaving and having a debonding defining two debonded fibrous portions that can be separated from each other, - obtaining a fibrous assembly (E20) by introducing the composite insert inside the porous fibrous reinforcement by separating the debonded fibrous portions at the debonding point, the composite insert thus introduced giving its shape to the reinforcement, - the introduction (E30) of a thermosetting resin into the porous fibrous reinforcement after obtaining the fibrous assembly, and - the co-cooking (E40) of the thermosetting resin thus introduced with the thermosetting polymer.

2. A method according to claim 1, wherein the fibrous stack (El) is formed by several layers (51) of unidirectional fibers oriented at an angle between -10° and +10° with respect to a radial direction (DR) of the blade or propeller blade.

3. A method according to claim 1, wherein the fibrous stack (E2; E3; E4) comprises at least (a) a first layer (151) of unidirectional fibers oriented with a first angle (ai) between -55° and -35° with respect to the radial direction (DR), and (b) a second layer (251) of unidirectional fibers oriented with a second angle (a?) between +35° and +55° with respect to the radial direction.

4. A method according to claim 3, wherein the fibrous stack (E3) is quasi-isotropic.

5. A method according to claim 3, wherein the stacking (E4) comprises, in succession in this order along the thickness direction of the composite insert: - a plurality of first layers (151) of unidirectional fibers oriented with the first angle between -55° and -35° with respect to the radial direction (DR), - one or more interlayered layers (351) of unidirectional fibers oriented at an angle between 80° and 100° with respect to the radial direction, - a plurality of second layers (251) of unidirectional fibers oriented at a second angle between +35° and +55° with respect to the radial direction, and - one or more additional layers (51) of unidirectional fibers oriented at an angle between -10° and +10° with respect to the radial direction.

6. A method according to any one of claims 1 to 5, wherein the thermosetting resin is introduced into the porous fibrous reinforcement by resin transfer molding.

7. A method according to any one of claims 1 to 6, wherein the fibrous stack (E1; E2; E3; E4) impregnated by the thermosetting polymer is present on a support form (10), and wherein the obtaining of the composite insert further comprises a consolidation of the fibrous stack by partial baking of the thermosetting polymer, as well as a removal or elimination of the support form, after consolidation, in order to obtain a hollow and consolidated composite insert, said hollow and consolidated composite insert being introduced inside the porous fibrous reinforcement to obtain the fibrous assembly.

8. A method according to any one of claims 1 to 6, wherein the fibrous stack (E1; E2; E3; E4) is carried out by automatic fiber placement technique on a support form (10), and wherein the composite insert is introduced inside the porous fibrous reinforcement with the support form (10).

9. A method for manufacturing an unfaired fan (111) for mounting on an aircraft, comprising: - the manufacture of a plurality of propeller blades (101) by implementing a process according to any one of claims 1 to 8, and - the mounting of said plurality of propeller blades thus manufactured on the fixing parts of a hub.

10. A method for manufacturing a ducted fan (112) for mounting on an aircraft, comprising: - the manufacture of a plurality of blades (102) by implementing a process according to any one of claims 1 to 8, and - the mounting of said plurality of blades thus manufactured on fixing parts of a hub.

Images