Rotor fan

Abstract

The invention relates to a rotor fan (1) for an aircraft, comprising a number of rotor blades (2) arranged rotationally symmetrically about a rotor axis (3). Each rotor blade (2) comprises a blade body (4) made of a composite material comprising reinforcing fibers (5) embedded in a matrix material (6) and extending in a longitudinal direction (7) between a bottom (8) and a top (9) and in a transverse direction (10) between a leading edge (11) and a trailing edge (12). The rotor fan (1) further comprises a hub (13) having a hub body (14), the hub body (14) being at least partially made of a composite material comprising reinforcing fibers (15) embedded in a matrix material (16). The bottom (8) of each rotor blade (2) comprises a base (17) at least partially embedded in the composite material of the hub (13).

Description

Technical Field

[0001] The invention relates to a rotor fan made of a fiber-reinforced composite material and a method for producing such a rotor fan. Background Art

[0002] US201916181471, first published in May 2019 on behalf of Safran Aircraft Engines, relates to a rotor blade. The rotor blade comprises a blade body made of a composite material comprising a fiber reinforcement densified by a matrix. The blade body extends in a longitudinal direction between a root or bottom and a tip or top, and in a transverse direction between a leading edge and a trailing edge. The fiber reinforcement of the blade body comprises a first portion consisting of a plurality of yarn layers interconnected by a three-dimensional or multi-layer braid. A second portion forms all or part of at least one leading edge or at least one trailing edge of the blade. The second portion comprises a plurality of short fibers oriented in a random manner. The yarns of the plurality of yarn layers of the first portion and the short fibers of the second portion are embedded in a matrix.

[0003] US2018147797A1, first published in May 2018 on behalf of Safran Aircraft Engines, relates to a method for manufacturing an airfoil element from a composite material. The method comprises the following method steps: manufacturing a fiber preform impregnated with a resin. The resin is polymerized with a matrix to obtain an airfoil element made of a composite material, the composite material comprising a fiber reinforcement densified by the matrix. A metal reinforcement is fastened to the composite airfoil element, wherein the metal reinforcement is fastened to the airfoil element by rivets. The method further comprises: before impregnating the fiber preform with the resin, inserting a spacing element between the fibers of the fiber preform, and removing the spacing element after the resin has been polymerized, thereby forming at least one channel between the fibers of the fiber reinforcement of the composite airfoil element.

[0004] US2018128282A1, first published in May 2018 on behalf of Rolls Royce Nam Tech Inc., relates to a compound turbine comprising a hub made of fiber and resin and a plurality of blade assemblies. Each blade assembly comprises a blade, a base and a tang. The plurality of blade assemblies are arranged circumferentially around the hub, each blade assembly interlocking with an adjacent blade assembly and held in place by the hub and a band covering the corresponding tang of each blade assembly of the plurality of blade assemblies. Summary of the invention

[0005] Today's aviation industry requires rotor fans that need to meet conflicting requirements such as both integral design and ease of recycling. The advantage of manufacturing rotor fans from plastic materials is that the basic process generally allows mass production and at the same time provides a high degree of freedom regarding the geometry. For this reason, people have recently shown interest in replacing rotor parts made of metal materials with rotor parts made at least partially of lightweight composite materials. In addition to being lighter than metal parts, rotor parts made of fiber-reinforced composite materials can exhibit improved thermal properties and can have lower material costs and manufacturing costs than metal parts.

[0006] However, rotor components made of composite materials tend to have disadvantages such as lower load and stress tolerances. However, since components in the aerospace industry, especially rotor components, are subject to high loads, many load cycles and temperature fluctuations, high structural integrity is crucial. This creates the following dilemma: often difficult to recycle material combinations have to be used, or production processes have to be selected that are not suitable for mass production.

[0007] It is therefore an object of the present disclosure to provide a rotor fan and a method for producing such a rotor fan which allow efficient mass production and meet the needs for achieving high mechanical requirements.

[0008] In one aspect, the present disclosure relates to a rotor fan for an aircraft. The rotor fan typically comprises a plurality of rotor blades, which are arranged rotationally symmetrically around a rotor axis. Good results can be obtained when the rotor blades are at least partially made of a fiber reinforced composite material, which comprises reinforcing fibers embedded in a surrounding matrix material. Each rotor blade typically comprises a blade body, which extends in a longitudinal direction between a bottom and a top.

[0009] Due to the high mechanical stresses caused by high speeds, acceleration forces and potential influencing elements such as bird strikes, as well as heat and pressure-related fluctuations, the choice of suitable materials is very limited. In particular, with regard to materials that are suitable as matrix materials. Good results can be obtained when the blade body is made of a fiber-reinforced composite material, which specifically comprises continuous fibers in the direction in which the loads occur. The continuous fibers are to be understood as fibers that are significantly longer than their diameter. Good results can be obtained using fibers in the range of at least 20 mm or more in length. In a variant, the continuous fibers can be arranged in a directional manner. The fibers are preferably arranged essentially parallel to the longitudinal direction of the rotor blade.

[0010] Alternatively or additionally, the composite material of the blade body may comprise a plurality of fiber layers which are interconnected by three-dimensional or multilayer weaving. The fibers or fiber layers may be prepared by a prefabrication process. Thus, the fibers may be arranged by a customized fiber placement process. Alternatively or additionally, prefabricated fiber tapes may also be used. In order to ensure that the fiber layers remain in the desired arrangement, the fibers may be stitched together. In the transverse direction, the blade body extends between the leading edge and the trailing edge. The continuous fibers or fiber layers may have been impregnated with a suitable composite material. Good results may be obtained using prepregs, which are fiber fabrics that have been pre-impregnated with resin.

[0011] In principle, thermoplastic materials and / or thermosetting materials, for example in the form of resins, can be used as matrix materials. Depending on the geometry and the desired properties, the blade body can be made by a molding process, such as a resin transfer molding process (RTM) or a molding process in which the matrix material is plasticized (e.g. hot pressing) or injected (e.g. injection molding). In a variant, a hot pressing process can be used to manufacture the blade body, wherein the composite material of the blade body comprises continuous fibers embedded in the matrix material. Good results can be obtained when using thermoplastic materials from the polyaryletherketone (PAEK) family. For example, polyetheretherketone (PEEK), which is a colorless, organic thermoplastic polymer, has excellent mechanical and chemical resistance that can be maintained to high temperatures. Thermoplastic materials from the polyaryletherketone (PAEK) family are among the few plastic materials that are compatible with ultra-high vacuum applications, which makes them suitable for aerospace applications.

[0012] For an aerodynamically optimized design, the blade body can be spatially bent in the transverse direction between the leading edge and the trailing edge. Alternatively or additionally, the blade body can also be wound between the bottom and the top with respect to the longitudinal direction. In order to further increase stability and wear resistance, the blade body can include a reinforced leading edge. The reinforcement can be designed as an insert or applied on top of the fiber layer of the blade body or between the fiber layers. The insert can be made, for example, as an insert made of titanium and / or a bent metal sheet. When the fiber to matrix ratio is between 2:1 and 1:1, a good compromise can be obtained between the structural integrity and the flexibility of the rotor blade.

[0013] The rotor fan typically further includes a hub having a hub body, the hub body being at least partially made of a composite material including reinforcing fibers embedded in a matrix material. Good results can be obtained when the reinforcing fibers of the hub are short fibers having a length in the range of 0.5 mm to 10 mm and arranged in a non-directional manner (e.g., by an injection molding process). The hub body can be designed as an annular sleeve, which is made, for example, by an injection molding process or a resin transfer process or a combination thereof. The hub is typically designed to interconnect several rotor blades to the shaft of the engine. Therefore, the bottom of the corresponding blade body and / or the base interconnected therewith can be embedded in the matrix material of the hub body. The blade body between the corresponding bottom and the corresponding top of the rotor blade typically extends radially away from the hub.

[0014] Good results with regard to an aerodynamically advantageous design can be achieved when the hub body has a conical outer surface. The outer surface is to be understood as the outer shell surface of the hub body, which surrounds the rotor axis and faces away from the rotor axis. Depending on the design of the rotor shaft, the central opening of the hub can have a staggered design. In order to allow the hub body to be assembled onto the corresponding rotor shaft, the hub comprises a bushing. The bushing can allow that the hub body can be attached to the rotor shaft by a friction connection. Good results can be obtained when the hub body is shrink-fitted onto the rotor shaft.

[0015] In order to allow a fast and reliable production of the hub body, the bushing can be overmolded together with the base of the rotor blade in the same production step. The bushing and the base of the rotor blade are preferably at least partially embedded in the composite material of the hub. In order to allow a shrink fit and a transmission of forces between the hub body and the rotor shaft, the bushing can be made, for example, of one of the following materials or a combination thereof: titanium, aluminum, steel.

[0016] In order to allow rapid production and at the same time achieve a structurally rigid connection between the hub and the rotor blades, the bottom of each rotor blade typically includes a base that is at least partially embedded (enclosed) in the composite material of the hub. The base is typically attached to the hub body by an adhesive that can be provided by the matrix material of the hub body. In order to increase the mechanical load bearing capacity of the hub body, and therefore increase the mechanical load bearing capacity of the entire rotor fan, the hub body is typically made of a composite material including reinforcing fibers. When the reinforcing fibers are short fibers, a good compromise between efficient processing and desired mechanical stability can be achieved. The short fibers are typically in the range of 0.5 mm and 10 mm, preferably between 3 mm and 5 mm. This allows an injection molding process in which the fibers are mixed into the plasticized matrix material and injected into the mold together with the matrix material.

[0017] In order to ensure that the rotor blade remains attached to the hub body in such a way that no delamination occurs between the rotor blade and the hub body even under high loads or impacts of objects (e.g. bird strikes in midair), the base can be interconnected with the hub body by a form fit. Good results can be achieved when the aerodynamically designed rotor blade does include a base with a bottom cutout at its bottom. The base can be designed as a substantially rectangular block, which includes a bottom cutout in the form of a recess.

[0018] In a variant, the recess extends at least partially along the base in the transverse direction of the corresponding rotor blade. The recess can be designed as a substantially V-shaped or U-shaped channel. In a variant, the hub body has a conical outer surface. The base can be wedge-shaped to obtain a smooth transition between the top surface of the base and the surrounding outer surface of the hub body. The top surface of the base is to be understood as the surface facing the top of the rotor blade. In order to make the force flow smoothly from the hub body into the corresponding rotor blade, the rotor blade can be incorporated into a base with a transition area, which produces a smooth transition between the top surface of the blade body and the base.

[0019] The adhesive bond between the base and the hub is crucial because this connection is subject to dynamic loads, vibrations and bending loads that may lead to failure of the connection, and therefore the rotor blade may be delaminated from the hub body. In order to prevent such failures, it is desirable that the geometry of the base facilitates both the manufacturing process of the rotor blade and a stable connection with the hub body. Since the base is typically at least partially embedded in the hub body, a Y-shaped geometry has proven to be advantageous. The Y-shaped base includes two legs that extend away from the bottom in an angled manner relative to the longitudinal direction. This design allows that continuous fibers or fiber layers of the hub body can extend from the top all the way into the base. The fiber layers of the two legs of the base can be merged in the bottom and stacked and extend parallel from the bottom to the top in the blade body. The design allows that the reinforcing fibers can be well aligned in the mold during the manufacture of the rotor blade and can be embedded in the hub body in such a way that loads and bending loads can be well compensated and transferred from the blade body to the hub body via the two legs.

[0020] When the hub body is made of several parts, good results can be achieved with regard to positionally accurate mounting. The hub body may include at least one ring, which is at least partially embedded in a composite material. The ring can be attached to the base in a form-fitting connection before the base and the ring are at least partially embedded in the matrix material of the hub body. The ring can be produced in a first production step and consist of, for example, continuous fibers or metals or a combination thereof that are wound or interwoven with each other. Before the ring and the rotor blades attached thereto are overmolded, the base is typically inserted into corresponding grooves of the mold. The grooves allow an arrangement in which the rotor blades can be arranged in a precisely positioned manner in a rotationally symmetrical manner around the rotor axis before the base is at least partially embedded in the matrix material.

[0021] When the ring is interconnected with the base in a form-fitting manner, good results can be achieved with regard to a torsionally rigid design, for example, because the ring comprises several grooves facing away from the rotor axis, which grooves are configured to receive the base of at least one rotor blade. Arranging the base in corresponding grooves of the ring improves the stability of the rotor fan, because it further increases the resistance of the rotor blade to twisting relative to the rotor axis under load. Furthermore, arranging the base in corresponding grooves of the ring positions the rotor blade relative to the ring before embedding the ring (for example, by overmolding).

[0022] In order to additionally strengthen the connection between the rotor blade and the hub, the base may include a protrusion that engages with the groove of the ring. This form-fitting connection increases the connection between the rotor blade and the hub, even in the case of high pull-out forces. Each groove may include at least one lateral recess that can receive a protrusion of the base of one of the several rotor blades. In a variant, the protrusion may be spherical and protrude laterally away from the base between the leading edge and the trailing edge. The ring may be arranged on the inside and simultaneously act as a bushing to allow the rotor fan to be assembled to the corresponding rotor shaft, as described above and below. The blade body of the rotor blade may be bent between the corresponding leading edge and the trailing edge. In addition, the blade body may also be bent between the top and the bottom in the portion of the blade body embedded in the hub body, thereby forming a bottom cut between the corresponding blade body and the hub body. The bottom cut may increase the resistance of the blade body to being pulled out of the hub body under load.

[0023] In order to reduce the moment of inertia and thus reduce the torque required for the desired angular acceleration of the rotor fan, the hub body can be optimized with respect to geometry. In a variant, the hub body comprises an outer collar, an inner collar and a bridge connecting the two collars to each other. The outer collar can be designed as a base surrounding the blade body embedded therein. The inner collar can be connected to a bushing. The bridge can be designed as an annular bead attached to the inner collar and connected to the outer collar.

[0024] By embedding the reinforcing fibers into the matrix material in the first mold to produce a single blade body of the rotor blade, an efficient production process that allows large-scale production and thus high production can be achieved. In a variant, each blade body is produced in a single cavity of the mold. Before the second half mold is connected to the first half mold to form the cavity, the reinforcing fibers are preferably arranged in the first half mold of the mold together with the matrix material. The reinforcing fibers and the matrix material are typically connected to each other in the cavity by a hot pressing process. Alternatively, the reinforcing fibers are placed in the first mold and the plasticized matrix material is injected after the mold is closed to surround the reinforcing fibers. After curing the rotor blade, the blade can be removed from the mold and combined with a plurality of additional rotor blades to form the outer contour of the rotor fan. The blade body and the base interconnected therewith are typically made in an integral manner in the first mold in a common molding process. This has the advantage that the interface can be avoided, which avoids stress concentration at the transition area between the blade body and the base.

[0025] Known assembly processes for rotor fans with rotor blades made of metal material typically require that the rotor blades be inserted individually into corresponding slots in the hub and must be fixed along the rotor axis. In contrast to the proposed method, several rotor blades can be arranged in a second mold in a rotationally symmetrical manner with respect to the rotor axis, and the base of the rotor blades can be at least partially embedded in the composite material of the hub in one process step.

[0026] Preferably, the rotor fan is made by a combination of two molding processes as briefly described below:

[0027] - Manufacturing individual rotor blades in a first mold by placing continuous fibers and a matrix material in a cavity of the first mold and closing the cavity of the first mold to hot-press the continuous fibers and the matrix material so that the continuous fibers are surrounded by the matrix material.

[0028] If appropriate, at least one additional part can be arranged in the cavity of the first mould together with the continuous fibres. The at least one additional part subsequently forms part of the rotor blade and is for example a leading edge or a reinforcing device or a combination thereof.

[0029] After sufficient solidification of the matrix material, the rotor blade is removed from the first mould.

[0030] - Positioning the bottom of the previously manufactured rotor blade into a corresponding recess adjacent to a cavity of a second mould arranged in the open position, so that the rotor blade is arranged rotationally symmetrically about the (imaginary) rotor axis of the rotor fan to be produced. The cavity at least partially corresponds to the hub body of the rotor fan.

[0031] - Closing the second mould so that the bottom of the rotor blade is enclosed in the cavity of the second mould.

[0032] - Forcing the liquefied plastic material through the opening into the cavity of the second mould, thereby filling the empty space of the cavity and surrounding the bottom of the rotor blade arranged in the cavity. The liquefied plastic material generally comprises a matrix material and relatively short reinforcing fibres arranged therein.

[0033] - After curing of the plastic material, the second mould is opened and the assembled rotor fan is removed. After curing, the short reinforcing fibres in the hub body are usually arranged in a random manner based on the flow of the material as it is distributed in the cavity during injection.

[0034] If appropriate, at least one additional part can be arranged in the cavity of the second mold before the material is injected. The at least one additional part forming part of the rotor fan is, for example, a rim, or a bushing, or a ring, or a reinforcement, or a combination thereof. The additional part can be made of composite material (for example in the case of an at least partially embedded reinforcement ring), or of metal, or a combination thereof.

[0035] It should be understood that both the foregoing general description and the following detailed description present embodiments and are intended to provide an overview or framework for understanding the nature and character of the present disclosure. The accompanying drawings are included to provide a further understanding and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the disclosed concepts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The disclosure described herein will be more fully understood from the detailed description and accompanying drawings given below, which should not be considered as limiting the disclosure described in the appended claims. The accompanying drawings show:

[0037] Figure 1 is a perspective view from the front and above of the first variant of the rotor fan;

[0038] Figure 2 is based on Figure 1 A variation of the rotor fan is shown in a perspective view from the rear and above;

[0039] Figure 3 is based on Figure 1 A variant of the rotor fan is shown in exploded perspective from the front top;

[0040] Figure 4 is based on Figure 1 A variation of the rotor fan is shown in perspective from the front and above, with a portion cut away;

[0041] Figure 5 is a perspective view of a first variation of a rotor blade, the perspective view showing a first lateral side of the rotor blade;

[0042] Figure 6 is based on Figure 4 A perspective view of a variation of a rotor blade showing opposite lateral sides of the rotor blade with portions cut away;

[0043] Figure 7 is a perspective exploded view of a second variation of a rotor blade having stacked fiber layers;

[0044] Figure 8 is a perspective exploded view from the front top of a first mold in which reinforcing fibers are arranged;

[0045] Fig. 9 is a perspective exploded view from the front top of a first mold in which a finished rotor blade is arranged;

[0046] Fig.10 is a perspective view from the front and above of a second mold in which a rotor blade is arranged;

[0047] Fig.11 is a schematic cross-sectional view of a third variant of a rotor blade having a Y-shaped base;

[0048] FIG. 12 is a second variation of the rotor fan from the front and top ( Fig.12a ) and posterior superior ( Figure 12b ) perspective view;

[0049] Fig.13 is a front view of a rotor blade of a variation of the rotor fan of FIG. 12 ;

[0050] Fig.14 is a front view of a rotor blade of a variant of the rotor fan according to FIG. 12 , in which the base is arranged in a ring;

[0051] Fig.15 is a front view of a rotor blade of a variation of the rotor fan according to FIG. 12 , which is partially embedded in the hub body;

[0052] FIG. 16 is a side view of a fourth variation of a rotor blade ( Fig.16a ) and front view ( Fig.16b );

[0053] Fig.17 is a variant of the rotor blades according to FIG. 16 arranged in a ring;

[0054] Fig.18 is a perspective view from the front and above of a second variant of the rotor fan, which is partially cut away. DETAILED DESCRIPTION

[0055] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all, features are shown. Indeed, the embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, the same reference numerals will be used to refer to the same components or parts.

[0056] Figures 1 to 4 A first variant of a rotor fan 1 is shown. The variant of the rotor fan 1 shown is designed for an aircraft. The rotor fan 1 shown typically comprises a number of rotor blades 2, which are arranged rotationally symmetrically with respect to a rotor axis 3. The rotor blades 2 are made of a composite material comprising reinforcing fibers 5 embedded in a matrix material 6. The blade body 4 typically extends in a longitudinal direction 7 between a bottom 8 and a top 9. Good results can be achieved when the blade body 4 is made of a fiber-reinforced composite material.

[0057] from Figure 3 As can be seen, the illustrated variant of the rotor fan 1 comprises a hub 13 having a hub body 14, the hub body being at least partially made of a composite material comprising reinforcing fibers 5 embedded in a matrix material 6. The illustrated hub body 14 is designed as an annular sleeve, which is typically made by an injection molding process. The individual rotor blades 2 are typically interconnected with the hub 13 by a molding process. The base 17 of the previously manufactured rotor blade 2 is arranged in an open position in the mold so that the rotor blade 2 is rotationally symmetrically arranged around a central axis, which typically corresponds to the subsequent rotor axis 3 of the rotor fan 1 to be produced. In order to produce the hub body 14, liquefied plastic material is forced into the cavity of the mold through the opening 33, thereby filling the empty space of the cavity and surrounding the base 17 of the rotor blade 2 arranged in the cavity.

[0058] The liquefied plastic material generally comprises a matrix material 16 and relatively short reinforcing fibers 15 arranged therein. The rotor fan 1 shown comprises a bushing 22 having a castellation 26. This allows that the hub body 14 can be attached to the rotor shaft by a friction connection, and the castellation allows a firm interconnection, thereby preventing delamination in the circumferential direction between the bushing 22 and the matrix material 16 due to the torque transmitted. In order to ensure that the rotor blade 2 remains attached to the hub body 14 in such a way that delamination does not occur between the rotor blade 2 and the hub body 14 even under high loads or under the impact of an object (e.g., a bird strike in the air), the base 17 can be interconnected with the hub body 14 by form fit. When the rotor blade 2 does include a base 17 at its bottom, a good result regarding a stable interconnection between the blade body 4 and the hub body 14 can be achieved, the base 17 having a geometric shape including a bottom cutout 20. The base 17 can be designed as a substantially rectangular block, which includes a bottom cutout 20 in the form of a recess.

[0059] from Figure 4 It can be seen that good results with regard to an aerodynamically advantageous design can be achieved when the hub body 14 has a conical outer surface. The outer surface is understood to be the outer shell surface of the hub body 14, which surrounds the rotor axis 3 and faces away from the rotor axis 3. Depending on the design of the rotor shaft, the central opening 21 of the hub 13 can have a staggered design. In order to allow the hub body 14 to be assembled to a corresponding rotor shaft, the hub body 14 shown includes a bushing 22.

[0060] Good results can be obtained when the hub body 14 is shrink-fitted onto the rotor shaft. In order to allow fast and reliable production of the hub body 14, the bushing 22 is typically overmolded together with the base 17 of the rotor blade 2. The bushing 22 and the base 17 of the rotor blade 2 are at least partially embedded in the composite material of the hub 13. In order to allow shrink fit and force transmission between the hub body 14 and the rotor shaft, the hub body 14 is typically made of one of the following materials or a combination thereof: titanium, aluminum, steel. The reinforcing fibers 15 of the hub body 14 can be short fibers. The short fibers are typically in the range of between 1 mm and 10 mm, preferably between 3 mm and 5 mm. This allows the reinforcing fibers 15 to be mixed into the plasticized matrix material 16 and injected into the mold together with the matrix material 16.

[0061] In order to allow rapid production and at the same time achieve a structurally rigid connection between the hub 13 and the rotor blade 2, the bottom 8 of each rotor blade 2 typically includes a base 17, which is at least partially embedded in the composite material of the hub 13. The base 17 is typically attached to the hub body 14 by an adhesive, which can be provided by the matrix material 16 of the hub body 14. Typically, the hub body 14 is made by an injection molding process. In order to increase the mechanical load bearing capacity of the hub body 14, and therefore increase the mechanical load bearing capacity of the entire rotor fan 1, the hub body 14 is typically made of a composite material including reinforcing fibers 15.

[0062] Figures 5 and 6 A first variant of a rotor blade 2 is shown. The rotor blade 2 shown comprises a composite material in which continuous fibers 5 are embedded in a matrix material 6 made of polyetheretherketone (PEEK). Depending on the design of the rotor blade 2, the blade body 4 may comprise a continuous fiber material. Alternatively or additionally, the blade body 4 may also comprise a fiber fabric and / or a fiber mesh. In the transverse direction 10, the blade body 4 extends between a leading edge 11 and a trailing edge 12. In order to further increase stability and wear resistance, the blade body 4 may comprise a reinforced leading edge 11. The reinforcement of the leading edge 11 may be designed as a reinforcing element 24 in the form of an insert, which is applied to the top of the blade body 4 or between fiber layers of the blade body 4. The insert may be made as an insert or a bent metal plate made of titanium.

[0063] from Figure 7 It can be seen that the composite material of the blade body 4 comprises a plurality of fiber layers 25 which are interconnected by three-dimensional or multi-layer weaving or stacking. In the transverse direction 10, the blade body 4 shown extends between the leading edge 11 and the trailing edge 12. The blade body 4 shown comprises a reinforced leading edge. The reinforcement is designed as an insert. In a variant, the bottom cutout 20 of the base 17 can be designed as a recess extending in the transverse direction between the leading edge 11 and the trailing edge 12 of the respective rotor blade 2.

[0064] The recess can be designed as a substantially V-shaped channel. In a variant of the hub body 14 with a conical outer surface, the base 17 can be wedge-shaped to obtain a smooth transition between the top surface of the base 17 and the surrounding outer surface of the hub body 14. The top surface of the base is understood to be the surface facing the top 9 of the rotor blade 2. In order to make the force flow from the hub body 14 smoothly into the corresponding rotor blade 2, the rotor blade 2 can be incorporated into the base with a transition area, which forms a smooth transition between the blade body 4 and the top surface of the base 17.

[0065] Figure 8 and Fig. 9A first forming process is shown for producing rotor blades of a rotor fan 1. The rotor fan 1 is typically produced by two subsequent forming processes. Figure 8 It can be seen that the individual rotor blades 2 are manufactured in the first mold 27 by placing the continuous reinforcing fibers 5 in the cavity of the first mold 27 formed by the first half mold 28 and the second half mold 29. Alternatively, the blade body 4 is manufactured by placing the reinforcing fibers 5 together with the matrix material 6 in the first mold 27 and hot pressing the reinforcing fibers 5 and the matrix material 6, whereby the matrix material 6 is plasticized and surrounds the reinforcing fibers 5. Alternatively, after closing the cavity of the first mold 27, the continuous fibers 5 can be surrounded by the matrix material 6, which is forced into the closed cavity of the first mold 27 through the opening 33 in a plasticized state, for example by an injection molding process. From Fig. 9 As can be best seen, after sufficient solidification of the matrix material 6, the respective rotor blade 2 is removed from the first mold 27. If appropriate, at least one additional part may be arranged in the cavity of the first mold 27 together with the continuous reinforcement fibers 5. The at least one additional part then forms part of the rotor blade 2 and is, for example, the leading edge 11, or the reinforcement element 24, or a combination thereof.

[0066] Fig.10 The second molding process for producing the rotor fan 1 is shown. The base 17 of the previously manufactured rotor blade 2 is thus placed into a corresponding recess 34 adjacent to the cavity of the second mold 30. The recess 34 is arranged in the second mold 30 so that in the open position the rotor blade 2 is arranged rotationally symmetrically about a central axis, which corresponds to the rotor axis 3 of the rotor fan 1 to be produced.

[0067] The cavity corresponds at least partially to the hub body 14 of the rotor fan 1. After closing the cavity of the second mold 30, the base of the rotor blade is enclosed in the cavity of the second mold 30 between the first half mold 31 and the second half mold 32. The liquefied matrix material is forced into the cavity of the second mold 30 through the opening 33, thereby filling the empty space of the cavity and enclosing the base 17 of the rotor blade 2 arranged in the cavity. The matrix material 16 of the hub body 14 is usually made of a liquefied plastic material and usually includes relatively short reinforcing fibers 15 arranged therein.

[0068] After curing the matrix material 16, the second mold 30 is opened and the assembled rotor fan 1 is taken out. After curing, the short reinforcing fibers 16 in the hub body 14 are typically arranged in a random manner based on the flow of the material when distributed in the cavity during injection. If appropriate, at least one additional part may be arranged in the cavity of the second mold before injecting the material. The at least one additional part forming part of the rotor fan 1 may be a bushing 22 or a ring 18 or a reinforcing element 24 or a combination thereof. The additional part may be made of a composite material (for example, in the case of an at least partially embedded reinforcing ring 18) or of a metal or a combination thereof.

[0069] Fig.11 A variant of a rotor blade 2 with a Y-shaped base 17 is shown. The Y-shaped base 17 shown comprises two legs which extend away from the bottom 8 of the blade body 4 at an angle relative to the longitudinal direction 7. This design allows that the reinforcing fibers 5 of the blade body 4 in the form of continuous fibers or fiber layers 25 can extend from the top 9 into the base 17. The fiber layers of the two legs of the base 17 can be merged in the bottom 8 and stacked between the bottom 8 and the top 9. The reinforcing fibers 5 can extend parallel to each other from the bottom 8 to the top 9 within the blade body 4. The adhesive bond between the base 17 and the hub 13 of the rotor blade 2 is particularly critical, since the dynamic loads of the rotor blade 2 and the resulting vibration and bending loads can lead to failure of the connection and to the rotor blade 2 falling off the hub body 4. The Y-shaped geometry has proven to be advantageous, since this geometry allows that the reinforcing fibers 5 in the form of continuous fibers or, as shown, in the form of fiber layers 25 can be well aligned in the mold during the manufacturing process of the rotor blade 2. When embedded into the hub body 14 , the Y-shaped base facilitates the introduction of side loads and bending forces into the hub body 14 .

[0070] Figures 12 to 14 and Fig.18 A second variant of a rotor fan 1 is shown. Similar to the first variant, the second variant of the rotor fan 1 is also designed for an aircraft. The rotor fan 1 shown comprises a number of rotor blades 2, which are arranged rotationally symmetrically with respect to a rotor axis 3. The rotor blades 2 are made of a composite material, which comprises reinforcing fibers 5 embedded in a matrix material 6. The blade body 4 typically extends in a longitudinal direction 7 between a bottom 8 and a top 9, wherein the bottom 8 and a base 17 interconnected therewith are partially embedded in a hub body 14.

[0071] from Fig.13 As can be best seen, the bases 17 of the blade body 4 each include a protrusion 37 that projects laterally from the blade body 4 between the leading edge 11 and the trailing edge 12. During assembly, the bases 17 of the blade body 4 are arranged in the ring 18, as shown in FIG. Fig.14as can be best seen. The illustrated ring 18 includes a number of grooves 35 that face away from the rotor axis 3 and that are each configured to receive a base 17 of one of a number of rotor blades 2. Arranging the bases 17 within respective grooves 35 of the ring 18 improves the stability of the rotor fan 1 as it further increases the resistance of the rotor blades 2 to twisting relative to the rotor axis 3 under load. After the bases 17 of the rotor blades 2 are arranged in the ring 18 (which may be integrally formed with the bushings 22), the preassembled rotor fan 1 is placed in a mold and overmolded. From Fig.15 and Fig.18 As can best be seen in the partially cut-away view shown in , the base 8 , the seat 17 and the ring 18 are overmolded and at least partially embedded in the hub body 14 .

[0072] Figure 16 and Fig.17 A fourth variant of a rotor blade 2 is shown. In the mounted state, the shown variant of the rotor blade 2 is mounted in a ring 18. The shown ring 18 comprises a number of grooves 35 which face away from the rotor axis 3 and are each configured to receive a base 17 of one of the several rotor blades 2. The shown base 17 comprises a protrusion 37 which engages with a recess 36 of the ring 18. This form-fitting connection strengthens the connection of the rotor blade 2 and the hub 13, even in the case of high pull-out forces. Each groove 35 may comprise at least one transverse recess 36 which is configured to receive a protrusion 37 of the base 17 of one of the several rotor blades 2. In a variant, the protrusion 37 may be spherical and protrude laterally away from the base 17 between the leading edge 11 and the trailing edge 12.

[0073] Fig.18 A second variant of the rotor fan 1 is shown in a perspective view from the front and partially cut away. As can be best seen from the cutout, the rotor blade 2 shown is bent between the leading edge 11 and the trailing edge 12. In addition, the blade body 4 is also bent between the top 9 and the bottom 8 in the portion of the blade body 4 embedded in the hub body 14, thereby forming a bottom cutout between the blade body 4 and the hub body 14. The bottom cutout increases the resistance of the blade body 4 to being pulled out of the hub body 14 under load.

[0074] Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure.

[0075] Reference numerals list

[0076] 1 rotor fan 19 outer surface

[0077] 2 Rotor blade 20 bottom cutout (base)

[0078] 3 rotor axis 21 center opening (hub)

[0079] 4 blade body (rotor blade) 22 bushing

[0080] 5Reinforcement fiber (blade body) 23Shell surface

[0081] 6 Base material (blade body) 24 Reinforcement elements

[0082] 7 longitudinal direction (blade body) 25 fiber layers

[0083] 8 bottom 26 toothed parts

[0084] 9 Top 27 First Die 10 transverse direction (blade body) 28 first half mold (first mold) 11 front edge 29 second half mold (first mold) 12 trailing edge 30 second mold 13 hub 31 first half mold (second mold) 14 hub body 32 second half mold (second mold) 15 Reinforcement fiber (hub body) 33 Opening

[0085] 16 base material (hub body) 34 recess 17 base 35 groove (ring)

[0086] 18 ring (hub body) 36 recess (ring)

[0087] 37 protrusions

Claims

1. A rotor fan (1) for an aircraft, comprising: a. A plurality of rotor blades (2) arranged rotationally symmetrically about a rotor axis (3), wherein each rotor blade (2) comprises a blade body (4) made of a composite material, the composite material comprising reinforcing fibers (5) embedded in a matrix material (6), and the blade body extends in the following manner: i. extending along the longitudinal direction (7) between the bottom (8) and the top (9); as well as ii. extending in a transverse direction (10) between the leading edge (11) and the trailing edge (12); and b. A hub (13) comprising a hub body (14) at least partially made of a composite material comprising reinforcing fibers (15) embedded in a matrix material (16), wherein c. The bottom (8) of each rotor blade (2) comprises a base (17) at least partially embedded in the composite material of the hub (13).

2. The rotor fan (1) according to claim 1, wherein: The base (17) of the rotor blade (2) is attached to the hub body (14) by adhesive.

3. The rotor fan (1) according to claim 2, wherein: The adhesive is provided by a matrix material (16) of the hub body (14).

4. The rotor fan (1) according to any one of the preceding claims, wherein: The base (17) is interconnected with the hub body (14) by form fit.

5. The rotor fan (1) according to claim 4, wherein: The hub body (14) comprises at least one ring (18) which is at least partially embedded in the composite material of the hub body (14), and the base (17) is interconnected with the ring (18) by form fit.

6. The rotor fan (1) according to claim 5, wherein: The ring (18) comprises a plurality of grooves (35) facing away from the rotor axis (3), each of which receives a base of one of a plurality of rotor blades (2).

7. The rotor fan (1) according to claim 6, wherein: The grooves (35) each comprise at least one transverse recess (36) which receives at least one protrusion (37) of a base (17) of one of the several rotor blades (2).

8. The rotor fan (1) according to claim 7, wherein: The at least one protrusion (37) is spherical and projects laterally away from the base (17) between the leading edge (11) and the trailing edge (12).

9. The rotor fan (1) according to any one of the preceding claims, wherein: The blade body (4) comprises continuous fibers, which are arranged substantially parallel with respect to a longitudinal direction (7) of the blade body (4).

10. The rotor fan (1) according to any one of the preceding claims, wherein: The leading edge (11) of the blade body (4) comprises a reinforcing element (24).

11. The rotor fan (1) according to any one of the preceding claims, wherein: The composite material of the hub body (14) includes short fibers mixed into a matrix material (16).

12. The rotor fan (1) according to any one of the preceding claims, wherein: The hub body (14) has a conical outer surface (19).

13. The rotor fan (1) according to any one of the preceding claims, wherein: The central opening (21) of the hub (13) has a staggered design.

14. The rotor fan (1) according to any one of the preceding claims, wherein: The hub (13) comprises a bushing (22) having a toothed design on a shell surface (23).

15. The rotor fan (1) according to any one of the preceding claims, wherein: The hub (13) comprises a bushing (22) made of one or a combination of the following materials: titanium, aluminum, steel.

16. A method for producing a rotor fan (1) according to at least one of the preceding claims, comprising the following steps: a. positioning the base (17) of the previously manufactured rotor blade (2) into a corresponding recess (34) adjacent to the cavity of the second mold (30) arranged in the open position, so that the rotor blade (2) is arranged rotationally symmetrically around the rotor axis (3) of the rotor fan (2) to be produced; b. closing the second mold (30) so that the base (17) of the rotor blade (2) is enclosed in the cavity of the second mold (30); c. forcing the liquefied matrix material (16) through the opening (33) into the cavity of the second mold (30), thereby filling the empty space of the cavity and surrounding the base (17) of the rotor blade (2) arranged in the cavity; d. After the matrix material (16) is solidified, the second mold (30) is opened and the rotor fan (1) is taken out.

17. The method for producing a rotor fan (1) according to claim 16, wherein: An individual rotor blade (2) is manufactured in a first mold (27) by placing reinforcing fibers (5) and a matrix material (6) in a cavity of the first mold (27) and hot pressing the continuous fibers and the matrix material (6) so that the plasticized matrix material surrounds the reinforcing fibers (5).

18. The method for producing a rotor fan (1) according to claim 16, wherein: An individual rotor blade (2) is manufactured in a first mold (27) by placing reinforcement fibers (5) in a cavity of the first mold (27) and injecting a plasticized matrix material (6) into the mold surrounding the reinforcement fibers (5).

19. Method for producing a rotor fan (1) according to at least one of claims 16 to 18, wherein: At least one additional part is placed in the cavity of the second mold (30) prior to inserting the matrix material (16).

20. Method for producing a rotor fan (1) according to at least one of claims 16 to 19, wherein: The at least one additional part forming part of the rotor fan (1) is, for example, a bushing (22), or a ring (18), or a reinforcing element (24), or a combination thereof.

21. Method for producing a rotor fan (1) according to at least one of claims 16 to 20, wherein: The liquefied matrix material (16) of the hub (13) includes short reinforcing fibers (15) which are arranged in a random manner in the hub body (14) after solidification.

22. Method for producing a rotor fan (1) according to at least one of claims 16 to 21, wherein: The blade body (4) and the corresponding base (17) are produced in a first mould in an integral manner in a common moulding process.

23. Method for producing a rotor fan (1) according to at least one of claims 16 to 22, wherein: Prior to overmolding the composite material of the hub (13), the ring (18) and the base (17) interconnected therewith are placed in a second mould.

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