Hollow blade with woven insert and expanding foam filling

Abstract

This concerns a manufacturing process for a molded part and the part itself, molded in three dimensions, comprising a composite material including a fabric and a resin, the part having a cavity (230'') filled with a honeycomb material (50). The honeycomb material comprises an expanded cellular polymer material. Figure 16

Description

Title of the invention: Hollow blade WITH woven insert AND expanding foam filling. Technical field

[0001] The present invention relates to the field of aircraft parts, such as propeller blades or vanes, which may be found on turboprop engines or on aeronautical turbomachinery, including those with unfaired propellers. Aeronautical turbomachinery housings are also specifically covered.

[0002] Hereafter the term “blade” covers both blades as such and propeller blades, aeronautical.

[0003] Often, such aircraft parts are made of metallic material. While they then offer good mechanical resistance, they nevertheless present the problem of a relatively large mass.

[0004] In order to obtain lighter parts, it is known to make them out of composite material, that is to say as structural parts with fiber reinforcement and resin matrix. Previous technique

[0005] EP3511240 thus presents a solution for a fibrous structure for blade reinforcement (or of (Propeller blade) Aeronautical composite material. This structure is woven in a single piece, incorporating an airfoil, a spar section, and a flared section. The fibrous structure has a bonding zone that creates a recess within the fiber structure into which a portion of a reinforcing insert is inserted. In this case, the spar extends inside the airfoil at the bonding zone, while another portion extends outside the airfoil at the root edge. The flared section extends beyond the airfoil as a continuation of the spar section. At the bonding zone, the airfoil has skins that are separate from each other and enclose the spar section.The skins define two recesses within the airfoil, one on each side of the spar section, opening at the base edge of the airfoil. The final blade is a part with a cavity into which inserts of a traditional, rigid, solid foam have been inserted.

[0006] In the field of aeronautical turbomachinery with propellers or shrouded blades, there are also many turbomachines known that are traversed by multiple gas flows, in particular with primary flow and secondary flow, or double flow. Technical problem

[0007] For several years, at least on aeronautical twin-flow turbomachinery, increasing the bypass ratio (ratio between the primary flow rate and the secondary flow rate) has been a preferred solution for engine manufacturers in order to improve engine performance and reduce their specific fuel consumption.

[0008] This translates into an increase in the diameter of the blades at iso-thrust of the turbomachines, in particular concerning the first blade, that of air inlet into the turbomachine: fan blade - or propeller, and its associated straightener (OGV or Outlet Guide Vane, in English).

[0009] This increase is even more significant for non-faired architectures.

[0010] However, increasing these dimensions has the particular disadvantage of leading to an increase in the mass of the blades and / or casings, which is detrimental to the performance of the turbomachine.

[0011] Until now, one solution to limit this mass impact has been to manufacture the blades and / or the casings in solid composite materials (3D woven composite material by RTM process for example - Resin Transfer Moulding or resin injection molding - ), instead of metallic materials (for example titanium).

[0012] However, given the foreseeable dimensions of the blades to come, such as for example on an unfaired turbomachine architecture, it seems necessary to be able to increase this reduction in mass.

[0013] One of the possible solutions to overcome this problem is to design and / or manufacture hollow aeronautical parts (called hollow parts).

[0014] However, during the operation of an aeronautical turbomachine, if hollow parts, particularly blades, are used, these are subjected to significant pressure from the airflow displaced by the turbomachine to provide thrust. This pressure can deform the part where it is hollow, crushing the cavity and thus, for example on a fan blade, risk significantly reducing its efficiency due to the deformation of the part's aerodynamic profiles.

[0015] A honeycomb material such as high-density foam can be used to fill the cavity, which makes it possible to meet the need for lightening the part and to limit or even completely eliminate the crushing of the skins.

[0016] However, during the operation of the turbomachine, the parts (particularly the blades) are subjected to mechanical stress, primarily or mainly in bending, under the influence of the airflow. To limit the impact of this stress, it is known—as in EP3511240—to add one or more inserts forming a stiffener. In the case where the stiffener is, or includes, a spar, and the composite part is a blade, the spar can also be used as the attachment point of the blade to the disk. of the turbomachine and thus allows to create a link between the aerodynamic skins of the blade, the honeycomb material in the cavity and the rest of the turbomachine.

[0017] Manufacturing hollow parts composed of numerous sub-components is also always difficult because handling them before they are consolidated with resin is delicate. The assembly of the various sub-components must be very precise and repeatable to ensure that the parts conform to specifications without a high rate of manufacturing rejects.

[0018] Supplying a part with a traditional, rigid foam in solid form and with precise geometric dimensions also represents a significant logistical and financial effort for a filling insert whose mechanical properties are weak, or even negligible with regard to the general behavior of the finished part.

[0019] Any stiffeners, which can therefore be stringers, are also generally designed as separate parts, subject to the same disadvantages as rigid foam (sensitivity to assembly, logistical complexity...).

[0020] All of this therefore poses problems which the invention seeks to take into account. Description of the invention

[0021] In view of the prior art, the present application proposes both a molded composite part and a method for manufacturing a composite part.

[0022] More specifically, the present invention relates in particular to a three-dimensional molded part comprising a composite material including a fabric and a resin, the part having a cavity filled with a honeycomb material (also called alveolar) hereinafter, this honeycomb material comprising a honeycomb polymer material, which is an expanded polymer foam.

[0023] Among the advantages, a simplification of the manufacturing process can be noted. Other advantages are noted below.

[0024] In the molded part, the expanded cellular polymer material may, in particular, be polyurethane. Advantage: widely available material, well understood, inexpensive, very effective for filling volume / space.

[0025] In terms of a manufacturing process for a part (which may be as above) comprising a three-dimensional weave, the process of the invention at least partially addresses the problem stated above and is thus presented as steps (which may be nested): - a three-dimensional weaving of the piece, incorporating a cavity, - the placement of the part in the first section of an injection mold, - the application of an expanding paste into the cavity, the expanding paste being applied: — either in a suitable quantity and in such a way as to occupy at least the majority of the empty volume of the cavity, once expanded in the form of alveolar material, — either in such a way as to occupy a peripheral space of the cavity, around a solid foam insert previously placed in the cavity, - a wait of a few moments, for a minimum time greater than 1 second, for the paste to react to form, in the cavity, a partially honeycombed material, then closure of the mold, by means of at least a second part of the mold, and finalization of the expansion of the honeycombed material, - an injection of resin into said (pre)form in order to densify it and form a composite material, and - removing the piece from the mold.

[0026] The waiting time of a few moments can be defined according to the precise reference of the expansive product used, the manufacturer's recommendations, and production experience allowing adaptation to the geometry and volume to be filled. Generally, the delay varies from a few seconds to less than 5 minutes. The waiting time will therefore last for a period tmin greater than one second. In one embodiment, tmin is between 1 second and 5 minutes.

[0027] It will be advantageous that the expansion reaction of the paste is not complete before closing the mold, allowing the shape of the foam to be adapted at the time of closing the injection mold, this also allowing the foam to create a non-zero pressure in the woven cavity.

[0028] “Solid foam” means: a rigid foam machined directly to the shape final, such as the products used in the State of the Art, the expanding foam used here allows, on the contrary, to 'catch up' any deviations from the geometric tolerances.

[0029] The term "fabric" refers to a surface obtained by assembling yarns or fibers that may be arranged in two crossed rows. The term therefore includes a fibrous preform or a woven preform. It can refer to any material, whether woven or non-woven, and thus to a fabric proper.

[0030] The "fabric" or fibrous structure, and therefore the part resulting from it, may be formed of any type of weave: two dimensions (2D), three dimensions (3D), in particular.

[0031] By "two-dimensional weaving" or "2D weaving", we mean here a classic weaving method in which each warp yarn passes from one side to the other of yarns in a single layer of weft.

[0032] By "three-dimensional weaving" or "3D weaving" we mean here a weaving method in which at least some of the warp yarns bind weft yarns over several weft layers.

[0033] The term "part" covers any type of part. It may be an unfinished part, such as a semi-finished part. It may be a preform; the preform of a finished part.

[0034] To promote the strengthening of the woven composite part in three dimensions, by carrying this out at a suitable point in the process in terms of ease of implementation, it is also proposed that the process defined herein further include, between the weaving of the part incorporating the cavity and the step where the expanding paste is contained in the cavity: - the weaving of a three-dimensional woven insert, which can be adapted to define a stiffener (also defined as an optional stringer below) for the part presenting the cavity, - the insertion of the stiffener into the cavity of the part.

[0035] This solution, however, requires the woven insert to be manufactured independently of the part with the integrated cavity. To avoid this and create an insert within this cavity by locally modifying the weave structure, it is also proposed that the weaving of the three-dimensional woven part incorporating the cavity include the weaving of such a (pre)form, which will thus be co-woven with the insert, which it will then integrate as a single unit.

[0036] Provide furthermore that weaving of the three-dimensional woven piece incorporating the cavity includes a debonding will facilitate the formation of the cavity, or housing, inside the fibrous structure to form said woven composite piece.

[0037] For the placement of the expanding paste in the cavity, a suitable solution involves placing a flexible membrane or hollow flexible bladder in the cavity, the expanding paste being contained within the flexible membrane or bladder, which is held in place in the mold at least until the resin is injected into the part, and preferably permanently. This facilitates the handling of the expanding paste and reduces the risk of leaks.

[0038] A useful point may also provide that the said waiting "of a few moments so that the paste reacts" corresponds to a duration such that a partial expansion reaction of the expansive paste in the first part of the injection mold is carried out, before the closing of the mold.

[0039] Such partial expansion of the paste prior to mold closure (i.e., without complete expansion before mold closure) allows the paste to expand to a volume or dimensions slightly greater than the final size(s) of the part. The additional (final) expansion of the paste, with the mold closed, then ensures a certain compaction of the composite before complete densification, and increases the density of the cellular material produced from said paste.

[0040] Besides simplicity of implementation and the possibility of manufacturing in fairly large series, the advantages are those of the part, already presented.

[0041] For the advantages already mentioned, the following is proposed as embodiments which can be implemented optionally, independently or in combination, in whole or in part, as the case may be: - an inflatable bladder, which is inflated in the cavity, or a pre-formed piece, reusable or not, made of silicone or polyurethane elastomer, is used as a flexible membrane. - the cavity has a bottom and an opening; the application of the expanding paste involves introducing it to the bottom of the cavity so that the expanding paste expands from the bottom towards the opening. - Expanding paste is placed in the cavity, using a previously selected expandable polymer whose gaseous release during a poly-addition reaction will form the said honeycomb material, which will then be dense in the cavity (a well-controlled and reproducible process in series). - Polyurethane is selected as the expandable polymer, the release of CO2 during the polyaddition reaction of which forms the said dense cellular material (a well-controlled process reproducible in series and with an initial paste without difficulty). supply).

[0042] “Dense” means: a sufficient density (for an alveolar foam) in order to to ensure a role in maintaining the aerodynamic profiles of the part during operation.

[0043] A density greater than 50 kg / mA3, or even 100 to 300 kg / mA3, may be advantageously targeted for aeronautical parts such as those considered here, to guarantee this function and limit the mass of the part.

[0044] As will be understood, the process presented, with all or part of its characteristics, will make it possible to manufacture, in particular, a preform of a blade for an aeronautical turbomachine. Brief description of the drawings

[0045] Other features, details and advantages of the invention will become apparent from the following detailed description of non-limiting embodiments and from the analysis of the accompanying drawings, in which: [Fig. 1] is a schematic view of a blade according to one embodiment of the invention, [Fig.2] is a cross-section of the blade of [Fig.1] according to the cutting plane A of [Fig.1]; [Fig.3] is a cross-section of the blade of [Fig.l] according to the cutting plane B of [Fig.l]; [Fig.4] is a cross-section of the blade of [Fig.1] along the cutting plane C of the [Fig.l]; [Fig.5] is a longitudinal section of the blade of [Fig.1] along the section plane D of [Fig.1]; [Fig.6] is a longitudinal section of the blade of [Fig.l] along the section plane E of [Fig.l]; [Fig.7] is a longitudinal section of the blade of [Fig.l] along the section plane F of [Fig.l]; [Fig.8] is a variant of the dawn of [Fig.1]; [Fig.9] is a cross-section of the blade of [Fig.8], along the cutting plane G; [Fig. 10] is a schematic perspective view of the rough fibrous structure after cutting of the outer floating fibers; [Fig.l 1] is a schematic perspective view of the rough fibrous structure after cutting the floating threads present on the spar portion of the rough; [Fig. 12] is a schematic perspective view of the resulting fibrous structure, as well as its shaping with conforming pieces. [Fig. 13] schematically represents a variant of the dawn of [Fig.1], in a state prior to that of [Fig.8]; [Fig.14] is a cross-section of the blade of [Fig.13], according to the cutting plane H; [Fig. 15] schematizes the dawn variant of [Fig.8] or 13, in a state later than that of [Fig. 13]; [Fig. 16] schematically represents the dawn variant of [Fig. 8] or 13, in a state later than that of [Fig. 15]; and [Fig.17] schematically shows, in cross-section, a variant of the blade of [Fig.1],8,13,15 or 16, according to the cutting plane G or H; [Fig. 18] schematically shows, in cross-section and according to the cutting plane G or H, a variant of the blade of the [Fig.1],8,13, 15 or 16, during manufacturing, in an injection mold. Description of method(s) of implementation

[0046] The drawings and description below contain elements that can not only serve to better understand the present invention, but also contribute to its definition, if necessary.

[0047] The invention applies generally to the manufacture of various parts, in particular propeller blades or vanes used in aircraft engines. A blade according to the invention may, in particular, constitute a shrouded wheel blade such as a fan blade or an unshrouded wheel blade as in so-called "open rotor" aircraft engines.

[0048] Fig. 1 represents a blade 10 intended to be fixed on an aeronautical turbomachine.

[0049] Like any aeronautical blade (or propeller blade) concerned here, the blade 10 has a free edge, or end 1 Id and, opposite, a foot 12 by which the blade is fixed to a rotor disk 101 of the turbomachine.

[0050] More specifically, the blade 10 comprises an aerodynamic profile 11 intended to form the aerodynamic part of the blade and a foot 12 formed by a thicker portion, for example with a bulbous cross-section. A strut 13 may be interposed between the foot 12 and the aerodynamic profile 11. The structure with the aerodynamic profile 11 has, in cross-section, a curved profile of variable thickness between its leading edge 1la and its trailing edge 11b along a direction DT transverse to the longitudinal, or elongation, direction DL of the blade. Along the longitudinal direction DL, the aerodynamic profile 11 extends, between a root edge 11c (or attachment edge to the rotor disc 101) and a free edge (or top edge) 1 Id. The root 12 extends along the transverse direction DT over a length less than the length of the root edge 1 of the aerodynamic profile 11.

[0051] As shown in Figures 1 to 7, the blade 10 comprises a fibrous reinforcement, designated 20 in some figures and densified by a matrix. The fibrous reinforcement 20 comprises, in a single piece: - an aerodynamic profile structure 21 intended to form the aerodynamic profile of the blade 10, - a portion of the longeron 22 extending inside the aerodynamic profile structure 21, - a swollen portion 24 forming the blade foot 12 extending in line with the longeron portion 22 outside the aerodynamic profile structure 21.

[0052] The portion of the longitudinal member 22 may be in one piece: - a part 22a extending inside the aerodynamic profile structure 21, and - a part 22b located outside the aerodynamic profile structure 21 and forming both the bulging portion 24 and, if it exists, Péchasse 13 of the blade 10.

[0053] The fibrous reinforcement 20 mainly comprises first and second parts 25 and 26 separated from each other by an intermediate zone 27. The first part 25 delimits a debonding zone Zd inside the airfoil structure 21, the debonding zone extending between the intermediate zone 27 and the foot edge 21c of the airfoil structure 21 corresponding to the foot edge 1 le of the airfoil 11 along the longitudinal direction DL and between the front and rear edges 21a and 21b of the airfoil structure 21 corresponding respectively to the leading edge 1 la and the trailing edge 11b of the airfoil 11 along the transverse direction DT. The first part 25 comprises first and second skins 28 and 29 detached from each other and detached from the spar portion 22, the first and second skins 28 and 29 extending between the front and rear edges 21a and 21b of the airfoil structure 21 along the transverse direction and between the intermediate zone 27 and the foot edge 21c of the airfoil structure 21 along the longitudinal direction, the skins 28 and 29 enclosing the spar portion 22. The first and second skins 28 and 29 delimit within the airfoil structure 21 the first and second recesses 30 and 31 present respectively on one side and the other of the spar portion 22 along the transverse direction, the first and second recesses 30 and 31 opening at the foot edge 21c of the airfoil structure 21. A first conforming element 40 is present in the first recess 30. Similarly, a second conforming element 41 is present in the second recess 31.

[0054] In order to conform the fibrous reinforcement 20 without significantly increasing the overall mass of the structure to the aerodynamic profile of the blade, the conforming elements 40 and 41 are at least partly made of honeycomb material 50, i.e. a honeycomb material with a low density such as a foam.

[0055] As an alternative to the portion of the spar 22, an insert 300 (which can be defined as a reinforcement insert or stiffener) could extend inside an aerodynamic profile structure 11', according to an embodiment which would conform to the schematic example [Fig.8],9.

[0056] Part 22a and the swollen portion 24, or part 22b, could be presented as such an insert, corresponding to insert 300.

[0057] In this solution: - dawn 10 becomes dawn or pale 10', - the 20 fibrous reinforcement in 3D woven composite material remains; it just changes reference point: 20', - the portion of the longeron 22 is therefore replaced by at least one insert or stiffener or reinforcement, such as that 300, 3D woven, made of the same composite material (resin + fibers) as the fibrous structure 200', or even co-woven with it, - the first and second housings 30, 31 can be maintained or replaced by a single housing defined below by the cavity 230' which extends inside the aerodynamic profile 11'.

[0058] Applicable in particular in these two cases and as illustrated in the example of figures 10 to 13, the manufacturing process of an aeronautical part according to the invention, includes the production of a fibrous structure, such as the fibrous structure blank 100 intended to form the fibrous preform of the part to be produced.

[0059] The fiber structure blank 100 is obtained by three-dimensional (3D) weaving carried out in a known manner using a loom, which may be of the jacquard type, on which a bundle of warp yarns or strands is arranged in a plurality of layers of several hundred yarns each, the warp yarns being linked by yarns of weft. The fiber structure blank 100 is woven in one piece. The blank comprises, in the example, an aerodynamic profile blank 111, a spar portion blank 122 and a bulge portion blank 112, the spar portion blank 122 extending inside the fiber structure blank 100 set back from the front and rear edges 100a and 100b along the transverse direction DT and, along the longitudinal direction DL, between an intermediate zone 103 located between the foot and free (or top) parts 100c and 100d of the fiber structure blank, the bulge portion blank 112 extending in the continuation of the spar portion blank 122.

[0060] In the illustrated example, the 3D weave is an "interlock" weave. By "interlock" weave, we mean here a weave structure in which each layer of weft yarns connects several layers of warp yarns with all the yarns in the same weft column having the same movement in the plane of the weave.

[0061] Other known types of three-dimensional weaving may be used, such as those described in WO 2006 / 136755. This document describes in particular the production by weaving in one piece of fibrous reinforcement structures for parts such as blades having a first type of core armor and a second type of skin armor which make it possible to confer both the mechanical and aerodynamic properties expected for this type of part.

[0062] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0063] As the fibrous blank, whose thickness and width can vary, is woven, as in the example, a certain number of warp yarns may therefore not be woven, which makes it possible to define the desired contour and thickness, continuously variable, of the blank 100.

[0064] In addition, during the weaving of the fibrous blank, a debinding 110 can be made inside the fibrous blank between successive layers of warp yarns and on a debinding zone Zd.

[0065] In the DL direction, a bond zone ZI in the fibrous blank extends the unbond zone Zd, so that, if H11 is the length of the aerodynamic profile 11, H11 = ZI + Zd.

[0066] More specifically, in the example (see [Fig. 10]), the debond 110 extends between an intermediate zone 103 and the foot edge 100c of the fiber structure blank 100 along the longitudinal direction DL and between the front and rear edges 100a and 100b of the fiber structure blank 100 along the transverse direction DT. The debond 110 separates the first and second portions present on either side of the spar portion blank 122 so as to form first and second skin blanks 104 and 105 debonded from each other. The first and second blanks Skins 104 and 105 extend between the front and rear edges 100a and 100b of the fiber structure blank 100 along the transverse direction DT and between the intermediate zone 103 and the foot edge 100c of the fiber structure blank along the longitudinal direction. The skin blanks 104 and 105 enclose the spar section blank 122 and the bulge section blank 112. The first and second skin blanks define, within the fiber structure blank 100, the first and second recesses 130 and 131 located respectively on one side and the other of the spar section blank 122 along the transverse direction DT.

[0067] Once the fiber structure blank 100 has been woven, the floating yarns present outside the woven mass are cut, for example by water jet, so as to define the outer contour of a fiber structure as illustrated in [Fig. 10], by way of example. Floating yarns present on the skin blanks 104 and 105 are also cut at the lower part of the fiber structure blank so as to expose the bulbous portion blank 112 as well as part of the spar portion blank 122 intended to subsequently form a blade strut. The floating threads present around the spar blank 122 and the bulge blank 112 are also cut by lifting the skin blanks 104 and 105 as shown in [Fig. 11], by way of example. For this purpose, first and second slots 107 and 108 are formed between the skin blanks 104 and 105.

[0068] As illustrated in [Fig. 12] by way of example, a one-piece woven fibrous structure 200 is then obtained, having, in this example, an airfoil 211, a spar portion 222 and a flared portion 212, the airfoil 211 extending in the longitudinal direction DL between a lower end 21le and an upper end 21Id and in the transverse direction DT between a leading edge 21la and a trailing edge 211b. The fibrous structure 200 includes a debonding zone Zd extending between the leading and trailing edges 21la and 211b of the airfoil 211 along the transverse direction DL and between an intermediate portion 203 and the root edge 21le of the airfoil 211 along the longitudinal direction.The spar portion 222 extends inside the airfoil 211 at the decoupling zone Zd, set back from the leading and trailing edges 21la and 211b along the transverse direction DT and, along the longitudinal direction DL, between an intermediate portion 203 located between the lower and upper edges 21le and 21Id of the airfoil 211 and the root edge 211c of said airfoil at which the spar portion 222 emerges. The flared portion 212 extends in line with the spar portion 222 outside the airfoil 211, the flared portion 212 extending along the transverse direction DT over a length L212 less than the . length L211 of the foot edge 21 of the airfoil. The bulged portion 212 is intended to subsequently form the blade foot 12. The airfoil 211 comprises at the debonding zone Zd the first and second skins 228 and 229 debonded from each other, the first and second skins extending between the leading and trailing edges 21la and 211b of the airfoil along the transverse direction DT and between the intermediate part 203 and the foot edge 21le of the airfoil along the longitudinal direction DL, the skins 228 and 229 enclosing the spar portion 222.

[0069] The first and second skins 228 and 229 define, within the airfoil, at least one cavity 230 which, in the example, is defined by first and second recesses 231a and 231b located respectively on one side and the other of the longeron portion 222 along the transverse direction. The cavity 230, and therefore the first and second recesses 231a and 231b in the example, open to the outside. The opening is, in the example, located at the lower end of the airfoil 211.

[0070] Two other examples of parts, each defining a woven fibrous structure, respectively 200' and 200”, incorporating a said cavity 230' or 230”, have been schematically shown in figures 13 to 17 and relate to the aforementioned example in figures 8,9. These may be the same parts as the woven fibrous structure 200, possibly obtained in the same way, except for the shape and, possibly, the realizations of the swollen portion 212 and the part 222, the latter being able to be presented as the insert 300.

[0071] Thus, in each situation of weaving a three-dimensional part made of resin + fiber composite material, as in particular in the woven fibrous structure blank 100 and in the woven fibrous structure 200, a cavity 230, 230' or 230'' has been integrated in a single piece into the woven structure.

[0072] Furthermore, with these examples of a possible integrated longeron extended by a foot 12, or of a possible reinforcing insert 300 forming a stiffener or possible longeron, it was possible to: - reinforce the woven piece at the location of its cavity 230, 230' or 230”, - add or integrate a paddle foot 12, if necessary, - and this with a 300 insert which can be one piece with the woven fibrous structure, or added in its cavity, such as 230' or 230" in the examples.

[0073] In other words, insert 300: - either will be woven separately in three dimensions so as to define a stiffener, with or without foot 12, for the piece presenting the cavity, such as 230' or 230” in the examples, then inserted into this cavity, after the desired preform, 200' or 200” in the examples, has been woven, - either it will have been integrated in one piece with the said preform, the weaving of the three-dimensional woven piece (200' or 200" in the examples) incorporating the cavity including therefore a co-weaving of such a stiffener.

[0074] In the second case, the co-weaving of the reinforcing insert 300 with the woven fibrous structure can be carried out in the same way as that of the fiber structure blank 100, similarly in the second case for the independent weaving of the reinforcing insert 300, but without the cavity.

[0075] The spar or stiffener, if it is woven three-dimensionally, may use a weave pattern that is locally distinct from that of the rest of the part. This applies to both possibilities described here.

[0076] The conformation of the fibrous structure 200 (allowing the aforementioned blade preform to be obtained, in the example) will then continue: - by introducing at least one conformational element into the aforementioned cavity or cavities, - and by placing the part, namely the woven fibrous structure 200, 200' or 200" in the example, in a first part 301 of an injection mold 310 of the part concerned (see [Fig. 18] according to an example).

[0077] Different types of conformation element(s) can be provided containing, or made at least in part by, an expansive paste 50 which will expand, in the aforementioned cavity (whether it is called so or "housing").

[0078] It can be noted that the expansion reaction is, for the majority of foams of the type concerned, linked to the production of gas during the polymerization reaction of the paste. The two phenomena (polymerization and expansion) are therefore simultaneous.

[0079] Using an expansive paste 50 is an essential aspect of the invention.

[0080] More precisely, it actually involves filling at least part of the cavity with a honeycomb material: - that is not initially a solid block, typically not a rigid foam element made by molding or machining from a block of material, - but an expanded cellular material, such as an expanded polymer foam.

[0081] Regarding the conformation element(s) that can be provided, it may first be the conformation elements 40 and 41 from the expansive paste 50, and which have therefore expanded respectively in the housings 231a and 231b, which therefore correspond respectively to the housings 30 and 31 of the blade 10.

[0082] It may also be at least one flexible membrane or hollow flexible bladder 43: - placement in the cavity concerned, such as the aforementioned 230' ', of the woven fibrous structure, and - which will have been partially filled with 50 expansive paste, which will then have expanded in the cavity.

[0083] It may also be at least one insert, such as 45 and / or 47 (see the example in [Fig. 17]), made of solid foam: - previously placed in the cavity concerned, such as the aforementioned 230' ' of the woven fibrous structure, the (each) insert leaving a free space 235 around it, between it and the internal surface 237 of the cavity concerned; - after which, around this or each insert, the remaining space 235 of the cavity will have been filled with the expanding paste 50, which will then have expanded within the cavity.

[0084] Thus, before injecting resin 60 into the mold 310 (see the example of the [Fig. 18]) and in order to densify the preform(s) and form the expected composite material, the expansive paste 50 will have been introduced: - either, in an appropriate quantity and in such a way that it occupies at least the majority of the empty volume of the cavity, once expanded into an alveolar form, like a foam, - either, so that it occupies a peripheral space of the cavity, around a solid foam insert previously placed in the cavity.

[0085] Regarding the anticipated expansion of the expanding paste 50 in the cavity, it will a priori be advantageous: - before closing the mold 310 by means of at least a second mold part 303, wait a few moments for the dough 50 to react by beginning to expand in the cavity, - then, with the 310 mold closed, inject the resin into the preform in order to densify it and form the composite material.

[0086] We will return to these different methods in more detail below:

[0087] The first scenario could be the following: - weaving of a first 3D woven preform, such as the fibrous structure 200, 200' or 200”, therefore provided with a cavity, such as 230, 230' or 230”; - weaving (if this part is necessary) of at least one second 3D woven preform, such as the one marked 300, to develop the insert(s), stiffener(s) and / or possible stringer(s); - placement of the first preform in said first part 301 of the mold 310, - insertion, if it exists, of the (each) second woven preform in the cavity 230, 230' or 230'' of the first preform; - addition of a small quantity of expansive paste 50 into a flexible membrane, such as a flexible bladder, such as 43, inserted into said cavity of the first preform, or into each of said cavities if there are several such cavities distinct or which are not in fluidic contact with each other; - wait a few moments, mold 310 open, for the dough 50 to react (partially) to swell / expand into an alveolar shape, then close the mold, bringing together the first part 301 and second part 303; - injection of resin 60 into the closed mold 310, so that the resin 60 penetrates in the preform in order to densify it and form the composite material (woven fibrous structure(s) + resin); - demolding.

[0088] This partial reaction of paste 50 is related to the fact that: - the expansion reaction can be lengthy in the core of the foam while the outer surfaces begin to stiffen, and - This can be an intermediate check to verify on a partially expanded foam that the preforms are still correctly positioned, even if it means making an adjustment before closing the injection mold.

[0089] The flexible membrane, or flexible bladder, such as 43, will surround the insert 300 or the conforming elements 40, 41, which may thus be entirely surrounded for their part located in their receiving cavity or housing.

[0090] An opening 44 through its wall will allow the flexible membrane, or flexible bladder, to be filled, especially if it is a bladder.

[0091] The orifice 44 could judiciously (from a mechanical, aerodynamic and manufacturing point of view, in particular) be positioned outside the aerodynamic zone of the part, rather at the lower end (1 le) of the blade, opposite the position of the opening 51.

[0092] The molded part can then be deburred, its conformity checked (composite material check, dimensional checks...).

[0093] The use of an expansive paste 50 instead of a solid foam during the shaping step of the fibrous structure(s) placed in the cavity of the preform makes it possible to remove a constraint on known manufacturing processes in which, in order to be able to insert a solid foam into the cavity of the preform, and if the part contained stiffener(s) or stringer(s), these had to be woven separately, so as not to create stress on the assembly.

[0094] By removing this constraint, we will be able to consider a further optimization of the process, thanks to the possibility of co-weaving: - the (every) second preform (and therefore the possible stiffener(s) and / or stringer(s)), - with the first preform, such as the fibrous structure 100.

[0095] The 3D weaving of the first preform, as well as the unbundling (Zd zone mentioned above) and a local adaptation of the weave structure, make it possible to form said cavity, such as 230, 230' or 230”. It is thus possible to create one or more stringers or stiffeners in this cavity by a local modification of the weave structure. The expansive nature of the cellular material 50 allows it to adapt naturally to all the geometries of the cavity in the first preform, conforming to the shapes of the first preform, at the ends of the cavity as well as around the stiffener(s) and / or stringer(s), if they exist. Figures 13, 15, 16 illustrate a cavity geometry that it would be impossible to fill with a solid foam block if the 300 insert is not made separately from the first preform.

[0096] By integrating this co-weaving optimization, the manufacturing process of the expected composite part can be carried out according to the following second scenario: - weaving by unbinding a first 3D woven preform, such as the fibrous structure 200, 200' or 200”, therefore provided with a cavity, such as 230, 230' or 230”, and co-weaving with at least one 3D woven insert 300, such as the aforementioned stiffener and / or spar; - placement of the first preform in said first part 301 of the mold 310, - addition of a small quantity of expansive paste 50 into a flexible membrane -like a flexible bladder-, such as 43, inserted into the cavity of the first preform, or into each of said cavities if there are several such cavities distinct or which are not in fluidic contact with each other; - wait a few moments, mold 310 open, for the dough 50 to react and expand (partially) into an alveolar shape, then close the mold, bringing together the first part 301 and second part 303; - injection of resin 60 into the closed mold 310, so that the resin 60 penetrates the preform in order to densify it and form the composite material (woven fibrous structure(s) + resin); - demolding.

[0097] Note that the use of a flexible membrane, such as a flexible bladder, such as 43, partially filled with the expanding paste 50, may be considered optionally.

[0098] Indeed, the function targeted here is: - to shape the first preform or woven fibrous structure, such as that 20 or 200, without significantly increasing the overall mass of this part, - to maintain, via the expansion of the alveolar material, the integrity of the cavity(ies) where the expansive paste 50 is placed.

[0099] The flexible bladder, such as 43, is designed to contain the expanding paste 50 and then the resulting expanded cellular polymer, thus facilitating processing. However, not using a bladder would have the advantage of more direct contact between the cellular material, the fibers, and the resin of the composite material, provided they are compatible. If they are only slightly compatible, it will be preferable to isolate the different components and therefore to maintain the use of a flexible bladder, such as 43.

[0100] The choice between these two options may also be dictated by the mechanical strength of the interface created between the expanded cellular material 50 and the fiber / resin composite. It may be desirable to ensure that the interface is indeed resistant to stress and has a long service life to be durable. A solution without a flexible bladder seems more favorable. for this aspect, because it allows direct physico-chemical contact between the expanded alveolar material and the resin of the composite material.

[0101] A third scenario may arise, as in the schematic embodiment example illustrated [Fig. 17].

[0102] According to this third alternative case, the hollow part is co-injected with a solid foam of simplified geometry, supplemented by an expanding foam allowing the geometry of the cavity to be completed without leaving a void.

[0103] The manufacturing process would then be as follows: - weaving of a first 3D woven preform, such as the fibrous structure 200, 200' or 200”, therefore provided with a cavity, such as 230, 230' or 230”; - weaving (if this part is necessary) of at least one second 3D woven preform, such as the one marked 300, to develop the insert(s), stiffeners and / or possible stringer(s); - placement of the first preform in said first part 301 of the mold 310, - insertion(s) into cavity 230, 230' or 230'' of the first preform, and also — of the solid foam piece(s), such as pieces 45, 47, leaving a space 235 between them and the internal surface 237 of said cavity in question, and — if there exist, insert(s) and / or stiffener(s) and / or possible spar(s) 22a, 24, 300, as second woven preform(s); - adjustment, in the said first part 301 of the injection mold 310, of the assembly first preform + solid foam part(s), such as parts 45, 47 + if they exist, second woven preform(s); - adding an appropriate quantity of expanding paste 50 into said (each) cavity, between the solid foam part(s), such as parts 45, 47, and the internal surface 237 of said cavity in question, as well as, if necessary, the other sub-components of the assembly; - wait a few moments for the expansive paste 50 to react and begin to expand, then close the mold 310, bringing together the first part 301 and second part 303; - injection of resin 60 into the closed mold 310, so that the resin 60 penetrates the preform in order to densify it and form the composite material (woven fibrous structure(s) + resin); - demolding.

[0104] Thus, in particular, the expanded alveolar material 50 will occupy volume at the periphery of the cavity concerned, such as that 230” mentioned above, of the woven fibrous structure, around the other sub-components of the assembly which will have been placed there, in serving as a filler material.

[0105] This third alternative scenario has the following advantages: - to reduce the supply costs of solid foam blocks, which can have simplified geometry, - to be able to imagine a cavity geometry, such as 230, 230' or 230”, which cannot be demolded, because it is completed by the expanded alveolar material 50, - to reduce the amount of expanded cellular material required in the first preform (which limits outgassing and may reduce the supply costs of this material), - to simplify the numerical simulations of expansion during the design of the part.

[0106] On the other hand, a disadvantage is the creation of a new material interface between the solid foam block(s) (such as 45 and / or 47) and the expanded alveolar material 50.

[0107] The fact that, in these various manufacturing options using an expandable cellular material 50, the expansion reaction of this material is carried out (partially) before the mold 310 is closed will allow the material to expand considerably to dimensions slightly larger than the final dimensions of the part (here, the cavity where the paste 50 has been placed). Closing the mold will then ensure, before the injection of the resin 60, a slight compaction of the expanded material 50, making it possible to ensure complete and homogeneous filling of said cavity, as well as a better interface between the fiber / resin composite 60 and the expanded material 50. It will also be possible to create compaction pressure on the first preform or woven fibrous structure, such as 20 or 200, thus guaranteeing the mechanical properties of the composite.However, it is not a question of waiting for the complete expansion of material 50 before closing the mold, because the additional or final expansion, with mold 310 closed, allows: . - to promote densification during the application of resin 60, and / or - to ensure a slight compaction of the woven skins before their densification.

[0108] This also makes it possible to simply increase the density of the expanded material 50, which might not be achieved if the closure is completed after the expansion of the material 50 has ended.

[0109] As noted above, it may in particular be provided that the (each) cavity, such as 230, 230' or 230”, has a bottom 49 and an opening 51, and that the placement of the expanding paste 50 includes its introduction into the bottom 49 of the cavity so that the expanding paste 50 expands from the bottom 49 towards the opening 51.

[0110] Indeed, another advantage of using an expansive material 50 compared to using a solid foam is that the opening 51 of the cavity, such as 230, 230' or 230”, can then be greatly reduced. Instead of having to pass at least one complete solid part through the opening of what may be the joint, and therefore having a large opening in the part, a small space will suffice: the opening 51 must allow: - the insertion of the flexible bladder 43 into said cavity, if such a bladder is provided, - the addition of the expanding paste 50 to the bottom 49 of this cavity; the addition of the expanding paste 50 will preferably be carried out towards the bottom 49 of the cavity so that the expanding paste 50 progresses by expanding from the bottom of the cavity towards its opening 51, without creating a vacuum pocket, during its expansion.

[0111] An opening 51 of as small a size as possible will also favorably limit the mechanical impact of the opening on the part.

[0112] The opening 51 may be less than 5cm in size and less than 1.5cm in width, depending on the dimensions of the part produced.

[0113] As an expansive material, the well-known expandable polymer polyurethane may be used, the release of CO2 from which during the poly-addition reaction forms a cellular material, such as a dense foam, commonly used in industry.

[0114] In the case of the present invention, the parameters to be considered when selecting the material 50, an expansive polymer, will favorably be: - the mechanical properties of the material 50 after expansion (density, compressive strength, etc.), in order to guarantee the functionality of the invention; - the implementation parameters (expansion time, expansion temperature) in order not to complicate the assembly; - the specific characteristics of the polymer: compatibility with the materials of the bladder (if provided for in the implementation), with the materials constituting the fiber and the resin of the composite material (if a bladder is not used), possibly, the materials of the blower disc if it is a blade,... etc.

[0115] Regarding the injection of resin 60 into the closed mold 310, and therefore the densification of the fibrous preform considered, if slits 107 and 108 are present on the front and rear edges 21a and 211b, they will preferably be closed by stitching before densification

[0116] Such densification consists of filling the porosity of the preform, in all or part of its volume, with the material constituting the matrix.

[0117] The matrix of the composite material can be obtained in a manner known per se by the liquid process. The liquid process consists of impregnating the preform with a liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer, such as resin, as mentioned above (the term "organic precursor") (may replace) possibly diluted in a solvent. The mold 310 in which the preform is placed can be sealed airtight, thus creating an internal cavity shaped like the desired final molded part.

[0118] With the 310 mold closed, the liquid matrix precursor (for example, a resin) can be injected into the entire cavity to impregnate the entire fibrous part of the preform.

[0119] The transformation of the precursor into an organic matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after removal of any solvent and crosslinking of the polymer, the preform still being held in the mold. The organic matrix can be obtained in particular from epoxy resins, such as the high-performance epoxy resin sold under the reference PR 520 by CYTEC or "2896" resin from 3M, or from liquid precursors of carbon or ceramic matrices.

[0120] In the case of forming a carbon or ceramic matrix, the heat treatment consists of pyrolyzing the organic precursor to transform the organic matrix into a carbon or ceramic matrix, depending on the precursor used and the pyrolysis conditions. Several consecutive cycles, from impregnation to heat treatment, can be carried out to achieve the desired degree of densification.

[0121] If, instead of a three-dimensional part, a two-dimensional (2D) part is desired, this will be possible, in particular, if the 2D fabric is draped over each part of the mold, or, for a blade, if the upper surface of the blade is draped over the expanding clay 50 and the mold is then closed. Thus, if a 2D weave is planned, it is proposed to weave the upper surface separately from the lower surface and produce them either by co-firing (with a resin interface between the two parts) or by sewing before shaping.

[0122] Furthermore, the densification of the fibrous preform can be achieved by the well-known transfer molding process, also known as RTM, in which a thermosetting resin is injected into the available internal space of the mold. A pressure gradient is generally established in this internal space between the point where the resin is injected and the resin discharge ports in order to control and optimize the impregnation of the preform by the resin.

Claims

Demands

1. A three-dimensional part comprising a composite material including a fabric formed of a three-dimensional weave and a resin, the part having a cavity (230, 230', 230”, 30, 31) filled with a honeycomb material (40, 41, 50), characterized in that the honeycomb material comprises an expanded cellular polymer material.

2. Part according to claim 1, wherein the expanded cellular polymer material (50) is polyurethane.

3. Method of manufacturing a part comprising a three-dimensional weaving, the method having steps; - weaving a first preform of the three-dimensional part, incorporating a cavity (230, 230', 230”, 30, 31), - placing the part in a first part (301) of an injection mold (310), - placing an expanding paste in the cavity, the expanding paste being placed: — either in an appropriate quantity and so as to occupy at least most of the empty volume of the cavity, once expanded into a honeycomb material (40, 41, 50), — or so as to occupy a peripheral space of the cavity, around a solid foam insert (45, 47) previously placed in the cavity, - waiting, for a minimum time greater than 1 second, for the paste to react to form, in the cavity, a partially honeycomb material, then closing the mold, by means of at least a second part (303) of the mold,and finalization of the expansion of the honeycomb material (40, 41, 50), - injection of resin into the first preform of the part in order to densify it and form a composite material, and - demolding of the part.

4. Method according to claim 3 further comprising, between weaving the part incorporating the cavity (230, 230', 230”, 30, 31) and the step where the expanding paste is contained in the cavity: - weaving a three-dimensional woven insert (300) for the part having the cavity, the insert being adapted to define a stiffener, - inserting the stiffener into the cavity of the part.

5. A method according to claim 3, wherein the weaving of the woven piece in three dimensions integrating the cavity includes the weaving of such a first preform of the piece co-woven with a three-dimensional woven insert (22, 300) which it then integrates, as a single piece with it.

6. A method according to any one of claims 3 to 5, wherein the placement of the expanding paste in the cavity comprises placing a flexible membrane or hollow flexible bladder (43) in the cavity (230, 230', 230", 30, 31), the expanding paste being contained in the flexible membrane or flexible bladder, the flexible bladder or flexible membrane (43) being held in place in the mold (310) at least until the resin is injected into the part, and preferably permanently.

7. A method according to any one of claims 3 to 5, wherein the weaving of the three-dimensional woven piece incorporating the cavity includes a debonding (110) made inside the piece.

8. A method according to any one of claims 3 to 7, wherein said waiting, for a minimum time greater than 1 second, for the paste to react corresponds to a duration such that a partial expansion reaction of the expansive paste in the first part of the injection mold is achieved, before the mold is closed (310).

9. A method according to any one of claims 3 to 8 wherein, the cavity having a bottom (49) and an opening (51), the placement of the expanding paste includes its introduction at the bottom of the cavity so that the expanding paste expands from the bottom towards the opening.

10. A method according to any one of claims 3 to 9, wherein the placement of the expansive paste in the cavity (230, 230', 230”, 30, 31) comprises the prior selection of an expandable polymer, the gaseous release of which during a polyaddition reaction forms said honeycomb material, which is dense in the cavity.

11. A method according to claim 10, wherein the selection of the expandable polymer includes the selection of polyurethane, the release of CO2 from which during the polyaddition reaction forms said dense (40, 41, 50) cellular material

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