Manufacture of a blade reinforcing element, with pre-compaction

Abstract

The invention relates to a method for manufacturing a fibrous preform (10) of a reinforcing element for a turbine engine blade, which comprises: - producing a fibrous blank (100) by three-dimensional weaving between a plurality of warp yarns (1001) and a plurality of weft yarns (1002), - pre-compacting the fibrous blank (100) in a pre-compaction tool (5), - removing a raw surface (103) of the fibrous blank (100) by water-jet cutting while the fibrous blank (100) is being pre-compacted in the pre-compaction tool (5), - removing the pre-compacted fibrous blank (100') from the pre-compaction tool (5), and - compacting the pre-compacted fibrous blank (100') in order to obtain the fibrous preform (10) of the reinforcing element.

Description

Description Title of the invention: MANUFACTURE OF A REINFORCING ELEMENT FOR A BLADE WITH PRE-COMPACTION Technical Field

[0001] The present invention relates to a reinforcing element for a composite blade of a turbomachine or propeller engine. The composite blade may, for example, be a fan blade, known as a "fan blade", or an outlet guide vane, known as an "OGV" for "outlet guide vane". Prior art

[0002] In order to obtain lightweight turbomachine blades with excellent thermomechanical properties, the blades are made in a well-known manner from a composite material, i.e. from a material comprising a fibrous reinforcement densified by a matrix, for example an organic matrix. In addition, the non-structural parts of the blades can be hollow in order to further reduce mass.

[0003] Document FR 3 063 514 A1 describes an example of a rectifier blade of a shrouded turbomachine extending radially between an internal platform, by which the blade is fixed to an internal casing of the turbomachine, and an external platform, by which the blade is fixed to an external casing of the turbomachine. The fiber reinforcement of the blade body of the blade has an end portion comprising two segments separated from each other up to a free end. The blade further comprises an added insert, called a "gap filler" or "roving" in English, making it possible to fill the empty space at the junction between the two separated segments. Such an insert can in particular be manufactured using a shaped braid.

[0004] Such turbomachine blades may belong, for example, to a dual-flow turbomachine, in which the air mass drawn in by the fan is divided in a well-known manner between a primary flow and a secondary flow. The bypass ratio of a turbomachine corresponds to the ratio between the flow rate of the primary flow and the flow rate of the secondary flow. In order to improve the performance of the turbomachine and reduce its fuel consumption, it is beneficial to increase this bypass ratio. However, such an increase in the bypass ratio requires increasing the height of the blades, in particular the fan blades and the associated rectifier blades, to maintain a similar engine thrust. This increase in height is even more significant for unducted turbomachines, in which the blades are already large and in which the rotational speeds are lower.

[0005] Thus, the insert as described above must meet the new geometric and structural constraints of these new blades. The insert must therefore have a more elongated and flared shape, and a more abrupt variation in thickness to adapt to the new blade geometries. However, such a shape is not achievable using known techniques, including with inserts made from a braid.

[0006] Furthermore, in unducted turbomachines, fixing the blade, in particular a guide vane, to a casing of the turbomachine only by its internal radial end located at the blade root results in all the forces being transmitted to the blade root area, which results in high levels of stress in the composite parts of the blade root. Known inserts do not allow the blade root area to be sufficiently reinforced locally, and thus do not sufficiently limit the opening and stresses at the level of the loose segments of the fiber reinforcement under tensile, compressive and bending stresses. Furthermore, known inserts made from a braid have too low a stiffness and therefore do not allow the overall stiffness of the blade to be sufficiently increased, which leads to an increased risk of buckling and a deterioration in the frequency placement of the guide vane. Statement of the invention

[0007] In order to overcome the aforementioned drawbacks, the invention proposes the manufacture of a reinforcing element making it possible to fulfill on the one hand the function of the reported insert known from the prior art and on the other hand to fulfill a function of spar, even when said reinforcing element has a very flared geometry.

[0008] To this end, the invention proposes a method for manufacturing a fiber preform of a reinforcing element for a blade, for example of a turbomachine, comprising the following steps:

[0009] - the production of a fiber blank by three-dimensional weaving between a plurality of warp threads extending in a first direction and a plurality of weft threads extending in a second intersecting direction, for example perpendicular, to the first direction, the fiber blank extending in the first direction between a reference surface and a raw surface, and extending in a third intersecting direction, for example perpendicular, to the first and second directions between two surfaces to be profiled,

[0010] - removal of the rough surface of the fiber blank by water jet cutting so as to produce a clean surface,

[0011] - the arrangement of the fiber blank comprising the net surface in a compacting tool in order to obtain a fiber preform having the shape of the reinforcing element to be obtained and having a determined volumetric fiber content;

[0012] the method being characterized in that it further comprises:

[0013] - arranging the fibrous blank in a pre-compaction tool before removing the rough surface of said blank, the pre-compaction tool comprising a housing delimited by a base and two jaws extending from said base, the spacing between the two jaws being adjustable, the fibrous blank being arranged in the housing of the pre-compaction tool so that the reference surface of said blank is arranged in contact with the base, then

[0014] - adjusting the jaws of the pre-compaction tool so that the housing of the pre-compaction tool has the shape of the fiber preform of the reinforcing element to be obtained in order to pre-compact the fiber blank, the surfaces to be profiled of the blank being arranged in contact with the jaws and the raw surface of the fiber blank being free;

[0015] the step of removing the rough surface being carried out while the fiber blank is pre-compacted in the pre-compaction tool, and the fiber blank pre-compacted being removed from the pre-compaction tooling after the rough surface removal step before being placed in the compaction tooling.

[0016] Thus, the preform of the reinforcing element is produced by three-dimensional weaving of fibers, which makes it possible to obtain a reinforcing element with excellent rigidity, in particular in the radial direction relative to the engine axis of the turbomachine. In addition, the interface between the three-dimensional weaving of the reinforcing element and the three-dimensional weaving of the rest of the blade is more robust.

[0017] By cutting the fiber blank of the reinforcing element while it is pre-compacted, the precision of the cutting is greatly increased, which makes it possible to produce more complex reinforcing element shapes that are more adaptable to new generation blades. Indeed, if the cutting were carried out in a conventional manner without pre-compaction, this step would cause a deformation of the fiber blank during cutting, and the net surface thus obtained would itself be deformed and far from the desired geometry.

[0018] The fiber blank may be pre-compacted so as to obtain a flared shape at the net surface. The fiber preform of the reinforcing element may have a flared shape. The thickness of the fiber preform of the reinforcing element along the third direction D3 may increase by at least 200% over a distance of less than 50% along the first direction Di of the length of said reinforcing element preform.

[0019] According to a particular embodiment of the invention, the fibrous blank is obtained by water jet cutting in a fibrous strip produced by three-dimensional weaving at the outlet of a loom.

[0020] According to another particular embodiment of the invention, the reference surface and the raw surface of the fiber blank comprise the same number of warp threads.

[0021] Thus, the fiber blank is produced without the warp threads coming out: it is therefore simpler and quicker to produce, and limits the risk of a defect appearing in said blank after cutting the coming out threads.

[0022] According to another particular embodiment of the invention, the fibrous blank comprises a first portion extending from the reference surface having a compacting capacity greater than the compacting capacity of a second portion of the blank extending from the raw surface.

[0023] According to another particular embodiment of the invention, the average diameter of the weft threads of the second portion of the blank is larger than the average diameter of the weft threads of the first portion of said blank.

[0024] According to another particular embodiment of the invention, the water jet cutting for removing the raw surface follows a non-rectilinear profile.

[0025] According to another particular embodiment of the invention, the fiber blank is arranged in the pre-compaction tool so that two raw lateral surfaces of the fiber blank opposite in the second direction are free, the two raw lateral surfaces being removed by water jet cutting while the fiber blank is pre-compacted in the pre-compaction tool.

[0026] Thus, it is also possible to cut two rough side surfaces in the same step as cutting the rough surface. This makes it possible to better control the shape of the side surfaces of the preform.

[0027] The invention further relates to a method of manufacturing a blade made of composite material comprising the following steps:

[0028] - the manufacture of a fiber preform of a reinforcing element as described previously,

[0029] - the manufacture of a fiber blade preform comprising at least two skins connected to each other at one end and delimiting between them a cavity opening into an opening,

[0030] - the insertion of all or part of the fiber preform of the reinforcing element into the cavity of the fiber blade blank so as to fill the opening of said cavity,

[0031] - densification by a matrix of the assembly formed by the fiber preform of the reinforcing element arranged in the fiber blade preform, so as to obtain a blade made of composite material comprising a reinforcing element.

[0032] According to a particular embodiment of the invention, a filling element is inserted at the bottom of the cavity of the fiber blade preform before the fiber preform of the reinforcing element is inserted into said cavity.

[0033] The filler element preferably has a density lower than the density of the reinforcing element and blade preforms, which makes it possible to reduce the mass of the final blade.

[0034] According to a particular embodiment of the invention, the blade is a stator blade. The blade may also be a rotor blade or a propeller blade.

[0035] Indeed, such a blade configuration is particularly suitable for a fixed blade.

[0036] The invention also relates to a blade obtained by the manufacturing method described above, the thickness of the reinforcing element of the blade obtained increasing by at least 200% over a distance less than 50% of the height of said reinforcing element.

[0037] The invention finally relates to a turbomachine comprising at least one blade as described previously. Brief description of the drawings [Fig. 1] Figure 1 is a partial schematic perspective view of a fibrous web made by three-dimensional weaving. [Fig. 2] Figure 2 is a schematic perspective view of a fiber blank of a reinforcing element. [Fig. 3] Figure 3 is a schematic perspective view of a pre-compaction tool. [Fig. 4] Figure 4 is a schematic sectional view of the fiber blank of Figure 2 arranged in the pre-compaction tooling of Figure 3. [Fig. 5] Figure 5 is a schematic top view of the fiber blank of Figure 2 arranged in the pre-compaction tooling of Figure 3. [Fig. 6] Figure 6 is a schematic perspective view of the fiber blank of Figure 2 pre-compacted with the tooling of Figure 3. [Fig. 7] Figure 7 is a schematic top view of a fiber blank placed in a pre-compaction tool according to a variant of the invention. [Fig. 8] Figure 8 is a schematic perspective view of the pre-compacted fiber blank of Figure 7. [Fig. 9] Figure 9 is an exploded schematic view of the arrangement of the pre-compacted fiber blank of Figure 6 in a compaction tool. [Fig. 10] Figure 10 is a schematic sectional view of a reinforcing element fiber preform inserted into a blade fiber preform. Description of the embodiments

[0038] The invention applies generally to the production of a turbomachine blade or vane made of composite material, which comprises a reinforcing element.

[0039] The invention finds an advantageous application for stator blades, called fixed blades, for example for rectifier blades. The blade obtained by the method of the invention can be an OGV type distributor blade, for "outlet guide vane" in English, in the case of a ducted engine. The blade obtained by the method of the invention can also be a stator blade of an unducted engine. The blade obtained by the method of the invention can thus be a blade of a UDF type turboprop comprising two unducted and counter-rotating fans, or of a USF type turboprop comprising a single unducted fan and a rectifier.

[0040] The manufacturing method according to the invention comprises producing a fiber blank of the reinforcing element. The fiber blank of the reinforcing element is intended to be shaped to obtain a fiber preform of the reinforcing element. The fiber preform of the reinforcing element is intended to form the fiber reinforcement of the reinforcing element.

[0041] According to a particular embodiment of the invention, the fibrous blank is obtained by trimming in a fibrous strip. The trimming of the fibrous blank in the fibrous strip can be carried out by water jet cutting.

[0042] Figure 1 illustrates an example of a fibrous strip 1000 allowing a fibrous blank 100 of a reinforcing element to be obtained.

[0043] The fibrous web 1000 is produced by three-dimensional weaving between a plurality of warp threads and a plurality of weft threads. The fibrous web 1000 can be produced in a well-known manner using a Jacquard type loom. By "three-dimensional weaving" is meant here a weaving method by which at least some of the warp threads bind weft threads over several weft layers. It is considered that a fibrous web or a fibrous blank produced by three-dimensional weaving can comprise another type of weaving on its surface, for example two-dimensional weaving, in order to improve its surface condition. The fibrous web or the fibrous blank can for example have a three-dimensional weaving weave of the interlock or multi-satin type. Different three-dimensional weaving methods that can be used are described in document WO 2006 / 136755.

[0044] The warp threads of the fibrous strip 1000 extend generally in a first direction Di and the weft threads of the fibrous strip 1000 extend generally in a second direction D2 perpendicular to the first direction Di. Thus, the fibrous strip 1000 extends longitudinally in the first direction Di and transversely in the second direction D2. The fibrous strip 1000 extends in thickness in a third direction D3 perpendicular to the first direction Di and to the second direction D2.

[0045] The cutting of the fiber blank 100 inside the fiber strip 1000 can be carried out in a well-known manner by water jet cutting. The fiber blank 100 is cut out in the fiber strip 1000 along a determined cutting path T. Preferably, to facilitate cutting in the fiber strip 1000, the path T has a rectangular shape as illustrated in FIG. 1. In order to obtain an advantageous orientation of the fibers in the fiber blank 1000 of the reinforcing element, the path T can be made up of straight lines Ti, T2, T3 and T4 directed along the first direction Di or along the second direction D2, that is to say directed along the warp and weft directions. In the example illustrated in FIG. 1, the longitudinal straight lines T2 and T4 of the path T extend along the first direction Di and the transverse lines Ti and T3 of the line T extend along the second direction D2.

[0046] Several fiber blanks of reinforcement element can be cut from the same fiber strip.

[0047] The fibrous blank 100 thus cut out is illustrated schematically in Figure 2. The fibrous blank 100 extends in the first direction Di between a reference surface 101 and a raw surface 103. In the example illustrated in Figures 1 and 2, the reference surface 101 was obtained by cutting the fibrous strip 1000 along a transverse straight line Ti of the line T, and the raw surface 103 was obtained by cutting the fibrous strip 1000 along a transverse straight line T3 of the line T. The fibrous blank 100 extends in the second direction D2 between a first lateral surface 102 and a second lateral surface 104. In the example illustrated in Figures 1 and 2, the first lateral surface 102 was obtained by cutting the fibrous strip 1000 along a longitudinal straight line T2 of the line T, and the second lateral surface 104 was obtained by cutting the fibrous strip 1000 along a longitudinal line T4 of the line T.The fiber blank 100 extends along the third direction D3 between a first surface to be profiled 105 and a second surface to be profiled 106. The surfaces to be profiled 105 and 106 of the fiber blank 100 are preferably planar in order to facilitate their manufacture, that is to say they extend in a plane along the first and second directions Di and D2.

[0048] The blank is thus produced by three-dimensional weaving between a plurality of warp threads 1001 and a plurality of weft threads 1002. The fibrous blank 100 may comprise a plurality of threads or filaments of various types, in particular ceramic or carbon threads or a mixture of such threads. Preferably, the fibrous blank may be produced from silicon carbide fibers. Generally, the fibrous blank may also be produced from fibers made of the following materials: alumina, mullite, silica, an aluminosilicate, a borosilicate, carbon, or a mixture of several of these materials.

[0049] The fiber blank 100 is preferably produced without the exit of layers of warp threads 1001 in order to facilitate its production, that is to say that all the warp threads 1001 of the fiber blank 100 extend from the reference surface 101 to the raw surface 103, without exit of warp threads through the surfaces to be profiled 105 and 106.

[0050] The fiber blank 100 comprises a first portion 110 extending from the reference surface 101 along the first direction Di, and extending over the entire length of the fiber blank 100 between the two lateral surfaces 102 and 104. Thus, the first portion 110 comprises the reference surface 101 and a portion of the two lateral surfaces 102 and 104. The first portion 110 does not include the raw surface 103. The fiber blank 100 further comprises a second portion 120 extending from the raw surface 103 along the first direction Di, and extending over the entire length of the fiber blank 100 between the two lateral surfaces 102 and 104. Thus, the second portion 120 comprises the raw surface 103 and a portion of the two lateral surfaces 102 and 104. The second portion 120 does not include the reference surface 101.

[0051] Preferably, the first portion 110 of the fiber blank 100 has a greater compacting capacity than the compacting capacity of the second portion 120 of the fiber blank 100. The first portion 110 may have a greater expansion than the second portion 120. The difference in compacting capacity between the first portion 110 and the second portion 120 may be achieved in various ways known to those skilled in the art. For example, the variation in compacting capacity may be achieved by using weft yarns of different diameters. Thus, the weft yarns of the first portion 110 of the fiber blank 100 may have a smaller average diameter than the average diameter of the weft yarns of the second portion 120.Preferably, in order to achieve the desired particular shape of the reinforcing element, the fiber blank 100 has an average diameter of the weft threads gradually increasing along the first direction Di from the reference surface 101 towards the raw surface 103. Each column of weft threads of. the fiber blank 100 may have the same number of weft threads, the columns of weft threads each extending in the third direction D3.

[0052] The fiber blank 100 may be formed by a plurality of first weft yarns 1002a having a first diameter and by a plurality of second weft yarns 1002b having a second diameter, the second diameter being greater than the first diameter. Thus, the weft yarns of the first portion 110 of the fiber blank 100 may be only first weft yarns 1002a, while the second portion 120 of the fiber blank 100 may comprise second weft yarns 1002b. In this configuration, if it is desired to progressively increase the average diameter of the weft yarns along the first direction Di from the reference surface 101 towards the raw surface 103, it is possible to progressively increase the proportion of second weft yarns 1002b in each column of weft yarns. It is of course not departing from the scope of the invention if the fiber blank is formed by weft yarns having more than two different diameters.

[0053] The fiber blank 100 is then placed in a pre-compaction tool 5. An example of such a pre-compaction tool is illustrated in FIG. 3.

[0054] The pre-compaction tool 5 comprises a first jaw 51 and a second jaw 52 arranged opposite each other. In particular, the first jaw 51 comprises a contact surface 51a arranged opposite a contact surface 52a of the second jaw 52. The jaws 51 and 52 may be made of metal, for example steel. The jaws 51 and 52 extend generally in a first direction D5I and in a second direction D 52 perpendicular to the first direction D5I. The contact surfaces 51a and 52a of the two jaws 51 and 52 may have an identical geometry, that is to say they are symmetrical. The contact surfaces 51a and 52a of the two jaws 51 and 52 may have a different geometry.

[0055] The pre-compaction tool 5 further comprises a base 53. The base 53 extends in the second direction D 52 and following a third direction D 53 perpendicular to the first and second directions D5I and D52. The two jaws 51 and 52 extend from the bottom 53 along the first direction D51.

[0056] The jaws 51 and 52 are spaced from each other in the third direction D 53 The spacing between the two jaws 51 and 52 along the third direction D53 is adjustable. Thus, the two jaws 51 and 52 are movable in translation relative to each other along the third direction D 53 The volume delimited by the bottom 53 and the jaws 51 and 52 defines a pre-compaction housing.

[0057] The fiber blank 100 can be arranged in the pre-compaction tool 5 so that the first, second and third directions D bD2 and D3 of the fiber blank 100 coincide respectively with the first, second and third directions D5I, D 52 and D 53 of the pre-compaction tool 5, as in the example illustrated in Figures 4 and 5.

[0058] The fiber blank 100 is arranged in the pre-compaction tool 5 so that the reference surface 101 of said fiber blank 100 is in contact with the bottom 53 of the pre-compaction tool 5. The reference surface 101 is thus present between the two jaws 51 and 52 of the pre-compaction tool 5. However, the reference surface 101 may have one or more portions which protrude from the jaws 51 and 52 in the second direction D2, D 52when the fiber blank 100 is arranged in the pre-compaction tool 5, as in the example illustrated in FIG. 5. The reference surface 101 can also be entirely present between the two jaws 51 and 52 when the fiber blank 100 is arranged in the pre-compaction tool 5.

[0059] The spacing between the jaws 51 and 52 is adjusted so that the jaws 51 and 52 are in contact with the surfaces to be profiled 105 and 106. When the fiber blank 100 is arranged in the pre-compaction tool 5, the raw surface 103 is free, that is to say it is not present between the jaws 51 and 52. The lateral surfaces 102 and 104 each have at least one portion which protrudes from the jaws 51 and 52 in the first direction Di, D5I when the fiber blank 100 is arranged in the pre-compaction tool 5, as illustrated in FIGS. 4 and 5. The lateral surfaces 102 and 104 of the fiber blank 100 may be present between the jaws 51 and 52 when the fiber blank 100 is arranged in the pre-compaction tool 5. The lateral surfaces 102 and 104 may also each have at least one portion which protrudes from the jaws 51 and 52 in the second direction D2, D 52 when the fiber blank 100 is arranged in the pre-compaction tool 5, as illustrated in FIG. 5. In this configuration, at least one of the side surfaces 102 or 104 may be free. Both side surfaces 102 and 104 may be free when the fiber blank 100 is arranged in the pre-compaction tool 5. In this configuration, the side surfaces 102 and 104 are called raw side surfaces.

[0060] The spacing between the jaws 51 and 52 is adjusted so that the jaws 51 and 52 compress the fiber blank 100 in order to obtain a pre-compacted blank 100'. The spacing between the jaws 51 and 52 is thus adjusted so that the pre-compacting housing, defined between the bottom 53 and the jaws 51 and 52, has the shape of the reinforcing element to be obtained. The compression of the fiber blank 100 can be made possible in particular by the different compacting capacities along the fiber blank 100 along the first direction Di. Thus, the thickness of the first portion 110 of the fiber blank 100 along the third direction D3 decreases more than the thickness of the second portion 120 of the fiber blank 100 along the third direction D3.

[0061] Preferably, the geometry and spacing of the jaws 51 and 52 during the are configured so as to produce a pre-compacted fibrous blank 100' having a flared shape.

[0062] The pressure applied by the jaws 51 and 52 to the fiber blank 100 makes it possible to shape the surfaces to be profiled 105 and 106 so as to obtain profiled surfaces 105' and 106' of the pre-compacted fiber blank 100' in the desired shape. The pressure applied by the jaws 51 and 52 to the fiber blank 100 makes it possible to reduce the area of ​​the reference surface 101 so as to obtain a pre-compacted reference surface 101' of the pre-compacted fiber blank 100' in the desired shape. The pressure applied by the jaws 51 and 52 to the fiber blank 100 makes it possible to shape the lateral surfaces 102 and 104 so as to obtaining pre-compacted lateral surfaces 102' and 104' of the pre-compacted fibrous blank 100' in the desired shape.

[0063] The pre-compacted blank 100' is then cut while still pre-compacted in the pre-compacting tool 5. The pre-compacted blank 100' is preferably cut by water jet cutting. The pre-compacted blank 100' is cut along a cutting path T d . The cutting path T d includes at least one portion T d 3 allowing the removal of the raw surface 103 of the fibrous blank 100. Indeed, the raw surface 103 is removed while the fibrous blank is pre-compacted in the pre-compacting tool 5. Cutting the fibrous blank 100 by removing the raw surface 103 makes it possible to obtain a net surface 103' having the desired shape.

[0064] The cutting is preferably carried out along the free edges of the jaws 51 and 52. The trajectory of the water jet is preferably oriented in the third direction D3, D 53The water jet can have a feed speed between 150 mm per minute and 250 mm per minute. The water jet can follow a straight path T d3 following the second direction D2, D 52 to remove the raw surface 103, as illustrated in FIG. 5. However, it does not depart from the scope of the invention if the cutting path for removing the raw surface 103 is non-rectilinear. For example, the cutting path for removing the raw surface 103 may have portions extending along the first direction Di, D5I. The net surface 103' obtained by cutting the fiber blank 100 may therefore have particular geometries adapted to the desired shape of the insert.

[0065] The cutting path T d may also include at least one portion T d2 or T d4allowing the removal of the raw lateral surface 102 or 104 of the fibrous blank 100. Indeed, the raw lateral surface(s) 102 or 104 can be removed while the fibrous blank is pre-compacted in the pre-compacting tool 5. Cutting the fibrous blank 100 by removing the raw lateral surfaces 102 and 104 makes it possible to obtain net lateral surfaces 102' and 104' having the desired shape.

[0066] Performing the cutting while the blank is pre-compacted makes it possible to achieve a flared pre-compacted blank geometry with a sudden variation in thickness, and with great precision.

[0067] The pre-compacted and cut fiber blank 100' is then removed from the pre-compacting tool 5, as illustrated in Figure 6.

[0068] Figures 7 and 8 illustrate a variant in which the raw surface 203 of the pre-compacted fiber blank 200' is cut along a cutting path T db is non-rectilinear in the plane comprising the first and second directions, to obtain a net surface 203' with a complex geometry. The shape of the pre-compaction tool 5', in particular the shape of the jaws 51', is obviously adapted to allow cutting.

[0069] The pre-compacted and cut fiber blank 100' is then placed in a compacting tool 6, as illustrated in Figure 9. Indeed, when the pre-compacted fiber blank 100' is extracted from the pre-compacting tool 5, it may re-expand and does not have the desired fiber volume ratio.

[0070] The compacting tool 6 is preferably composed of several blocks 60 configured to compact the pre-compacted and cut fiber blank 100'. The compacting tool 6 is configured to compact the pre-compacted fiber blank 100' to the desired fiber volume ratio. The compacting tool 6 is configured to compact the pre-compacted fiber blank 100' so as to obtain a fiber volume ratio of between 50% and 70%. The compacting tool 6 is configured to compact the pre-compacted fiber blank 100' into a fiber preform 10 of a reinforcing element. The fiber preform 10 of the reinforcing element is intended to form the fiber reinforcement of the reinforcing element which will be densified by a matrix.

[0071] The compacting tool 6 can also perform a drying function. Thus, the fiber preform 10 present in the compacting tool 10 can be subjected to one or more drying cycles. Thus, the step of compacting the pre-compacted fiber blank 100' into a fiber preform 10 and the drying step can be carried out simultaneously. Then, the fiber preform 10 placed in the compacting tool is cooled and then cold demolded. Thus, the fiber preform 10 is solidified and rigid, even in the thinnest portions. The fiber preform 10 obtained may have a flared shape with a sudden variation in thickness.

[0072] The fiber preform 10 thus comprises a first end surface 11 having a small area, corresponding to the reference surface 101' of the pre-compacted fiber blank 100', and a second end surface 13, opposite the first end surface 11, having a large area, corresponding to the net surface 103' of the pre-compacted fiber blank 100'. The fiber preform 10 also comprises two profiled surfaces 15 and 16 corresponding to the profiled surfaces 105' and 106' of the pre-compacted fiber blank 100'.

[0073] The fiber preform 10 of the reinforcing element is intended to be co-densified with at least one fiber blade preform to obtain a blade made of composite material.

[0074] For this purpose, a fiber blade preform 20 is produced in a well-known manner by weaving, comprising at least two skins 21 and 22 connected to each other at least at one end, for example by means of a delinking in the weaving separating said two skins 21 and 22. The two skins 21 and 22 of the blade preform 20 delimit between them a cavity opening onto an opening. The fiber blade preform 20 can be produced entirely by three-dimensional weaving. The free end of the skins 21 and 22 of the blade preform 20 can be intended to form one or more platforms of the blade to be obtained. Preferably, the first skin 21 is intended to be located at the intrados in the final blade and the second skin 22 is intended to be located at the extrados of the final blade.

[0075] As illustrated in Figure 10, at least a portion of the reinforcing element fiber preform 10 is inserted into the cavity of the blade fiber preform 20, such that the reinforcing element fiber preform 10 fills the opening of said cavity. In particular, the first end surface 11 of the fiber preform 10 is present in the cavity, while the second end surface end 13 is present at the opening of the cavity of the blade preform 20.

[0076] The reinforcing element fiber preform 10 may be inserted entirely into the cavity of the blade preform 20. The reinforcing element fiber preform 10 may comprise a portion present outside the cavity of the blade preform 20.

[0077] According to a particular embodiment of the invention, before inserting the reinforcing element fiber preform 10, at least one filling element 30 is inserted into the bottom of the cavity of the blade fiber preform 20. In this configuration, the first end surface 11 of the fiber preform 10 may be in contact with the filling element 30. The filling element has a lower density than the fiber preforms 10, 20 and 30. The filling element 30 may be made of foam, for example a foam of organic origin (polyethacrylimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyetherimide (PEI), polyvinyl, carbon, polyisocyanurate, polyurethane, etc.). The filling element 30 may have a honeycomb structure.

[0078] According to a particular embodiment of the invention, compatible with the previous embodiment, a fibrous plate preform 40 can be arranged in contact with the second end surface 13 of the preform of the reinforcing element 10 and in contact with the two skins 21 and 22 of the blade preform, as illustrated in FIG. 10.

[0079] A set of fiber preforms is thus obtained comprising the preform of the reinforcing element 10, the blade preform 20 and possibly the filling element(s) 30.

[0080] The height of the fiber preform of the reinforcing element 10 may be greater than 3% of the total height of the set of preforms. In particular, the height of the fiber preform of the reinforcing element 10 may be greater than 5% of the total height of the set of preforms, for example greater than 10% of the total height of the set of preforms. By "height of the preform fibrous preform of the reinforcing element”, the distance between the first end surface 11 and the portion of the second end surface 13 furthest from the first end surface 11 is designated. The height of the fibrous preform of the reinforcing element 10 may be less than 50% of the total height of the set of preforms. In particular, the height of the fibrous preform of the reinforcing element 10 may be less than 10% of the total height of the set of preforms. The height of the fibrous preform of the reinforcing element 10 may be between 5% and 15% of the total height of the set of preforms. Thus, the fibrous reinforcement will extend into the final blade over a sufficient distance to increase the stiffness of the root, but not too great in order to limit the mass of the blade to be obtained.

[0081] The set of fiber preforms formed at least by the fiber preform of the reinforcing element 10 and the fiber blade preform 20 is then densified. The set of fiber preforms can be placed in an injection mold having a molding cavity whose dimensions correspond substantially to the dimensions of the final blade to be produced.

[0082] The well-known injection or transfer molding process known as "RTM" (for "Resin Transfer Molding") can be used. According to this process, a resin, for example a thermosetting resin, is injected via one or more injection ports into the molding cavity occupied by the set of preforms. The resin used can be, for example, an epoxy resin with a temperature class of 180 °C. Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of the temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the blade must be subjected. Once the resin has been injected into the entire set of preforms, it is polymerized by heat treatment in accordance with the RTM process. After injection and polymerization, the blade is demolded.It may optionally undergo a post-baking cycle to improve its thermomechanical characteristics, for example to increase its glass transition temperature. Finally, the blade is trimmed to remove the excess. of resin. Passages and counterbores can be machined, particularly at the base of the blade.

[0083] Optionally, a leading edge can be inserted. An outer layer forming the leading edge is then placed over the assembly to achieve the leading edge mating. Then, the leading edge is autoclaved to be bonded to the assembly.

[0084] A blade made of composite material is thus obtained, comprising a reinforcing element made of composite material, the fiber reinforcement of which is formed by the fiber preform of the reinforcing element 10. The blade obtained is preferably made of organic matrix composite material. Indeed, organic matrix composite materials have good mechanical characteristics for a reduced mass. It is of course not outside the scope of the invention if the blade is densified in a well-known manner by a ceramic matrix, for example by means of a slip.

Claims

Claims

1. A method of manufacturing a fiber preform (10) of a reinforcing element for a blade, comprising the following steps: - producing a fiber blank (100) by three-dimensional weaving between a plurality of warp threads (1001) extending in a first direction (D and a plurality of weft threads (1002) extending in a second direction (D2) intersecting the first direction (DJ, the fiber blank (100) extending in the first direction (DJ between a reference surface (101) and a raw surface (103), and extending in a third direction (D3) intersecting the first and second directions (Di, D2) between two surfaces to be profiled (105, 106), - removing the rough surface (103) from the fibrous blank (100) by water jet cutting so as to produce a clean surface (103'), - the arrangement of the fibrous blank (100') comprising the net surface (1039) in a compacting tool (6) in order to obtain a fibrous preform (10) having the shape of the reinforcing element to be obtained and having a determined volumetric fiber content; the method being characterized in that it further comprises: - arranging the fibrous blank (100) in a pre-compaction tool (5) before removing the rough surface (103) of said blank (100), the pre-compaction tool (100) comprising a housing delimited by a bottom (53) and two jaws (51, 52) extending from said bottom (53), the spacing between the two jaws (51, 52) being adjustable, the fibrous blank (100) being arranged in the housing of the pre-compaction tool (5) so that the reference surface (101) of said blank (100) is arranged in contact with the bottom (53), then - adjusting the jaws (51, 52) of the pre-compaction tool (5) so that the housing of the pre-compaction tool (5) has the shape of the fiber preform (10) of the reinforcing element to be obtained in order to pre-compact the fiber blank (100), the surfaces to be profiled (105, 106) of the blank (100) being arranged in contact with the jaws (51, 52) and the raw surface (103) of the fiber blank (100) being free, the step of removing the rough surface (103) being carried out while the fibrous blank (100) is pre-compacted in the pre-compacting tool (5), and the pre-compacted fibrous blank (100') being removed from the pre-compacting tool (5) after the step of removing the rough surface (103) before being placed in the compacting tool (6).

2. Manufacturing method according to claim 1, in which the fibrous blank (100) is obtained by water jet cutting in a fibrous strip (1000) produced by three-dimensional weaving at the outlet of a loom.

3. Manufacturing method according to claim 1 or 2, wherein the reference surface (101) and the raw surface (103) of the fiber blank (100) comprise the same number of warp threads (1001).

4. A manufacturing method according to any one of claims 1 to 3, wherein the fibrous blank (100) comprises a first portion (110) extending from the reference surface (101) having a compacting capacity greater than the compacting capacity of a second portion (120) of the blank extending from the raw surface (103).

5. Manufacturing method according to claim 4, wherein the average diameter of the weft threads (1002a, 1002b) of the second portion (120) of the blank (100) is larger than the average diameter of the weft threads (1002a) of the first portion (110) of said blank (100).

6. A manufacturing method according to any one of claims 1 to 5, wherein the water jet cutting for removing the raw surface (103) follows a non-rectilinear profile.

7. A manufacturing method according to any one of claims 1 to 6, wherein the fibrous blank (100) is arranged in the pre-compaction tool (5) such that two raw lateral surfaces (102, 104) of the fibrous blank (100) opposite in the second direction (D2) are free, the two raw lateral surfaces (102, 104) being removed by water jet cutting while the fibrous blank (100) is pre-compacted in the pre-compaction tool (5).

8. A method of manufacturing a blade made of composite material comprising the following steps: - the manufacture of a fibrous preform of a reinforcing element (10) according to any one of claims 1 to 7, - the manufacture of a fiber blade preform (20) comprising at least two skins (21, 22) connected to each other at one end and delimiting between them a cavity opening into an opening, - inserting all or part of the fiber preform of the reinforcing element (10) into the cavity of the fiber blade blank (20) so as to fill the opening of said cavity, - densification by a matrix of the assembly formed by the fibrous preform of the reinforcing element (10) arranged in the fibrous blade preform (20), so as to obtain a blade made of composite material comprising a reinforcing element.

9. A manufacturing method according to claim 8, wherein a filling element (30) is inserted at the bottom of the cavity of the blade fiber preform (20) before the fiber preform of the reinforcing element (10) is inserted into said cavity.

10. A manufacturing method according to claim 8 or 9, wherein the blade is a stator blade, a rotor blade or a propeller blade.

11. Blade obtained by the manufacturing method according to any one of claims 8 to 10, the thickness of the reinforcing element of the blade obtained increasing by at least 200% over a distance less than 50% of the height of said reinforcing element.

12. Turbomachine comprising at least one blade according to claim 11.

Images