Fabric and resin composite material part

Abstract

The invention relates to a method for producing a moulded part and to the three-dimensionally moulded part itself, comprising a composite material including a fibrous preform and a resin, the part having a cavity (230') filled with a cellular material (50). The cellular material comprises an expanded cellular polymeric material.

Description

Description TITLE: Part made of composite material, fabric and resin 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 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 strength, 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 presents a fiber structure solution for reinforcing aeronautical blades (or propeller blades) made of composite material. This structure is woven in a single piece, integrating an airfoil, a spar section, and a flared section. The fiber structure includes 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 the other 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 unbound from one another and enclose the spar section.The skins delimit within the aerodynamic profile respectively two housings present on one side and the other of the portion of the spar and opening at the level of the foot edge. of the aerodynamic profile. The final blade is a piece with a cavity into which inserts of a traditional, rigid, solid foam have been introduced.

[0006] In the field of aeronautical turbomachinery with propellers or shrouded blades, we also know of many turbomachines through which multiple gas flows pass, in particular with primary flow and secondary flow, or double flow. Technical problem

[0007] For several years, at least on twin-flow aeronautical turbomachinery, increasing the bypass ratio (ratio between the primary flow rate and the secondary flow rate) has been a preferred solution for engine manufacturers 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 intake into the turbomachine: fan blade - or propeller, and its associated straightener (OGV or Outlet Guide Vane).

[0009] This increase is even more significant for unfaired architectures.

[0010] However, increasing these dimensions has the 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 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 on an unfaired architecture of aeronautical turbomachine of the type ('Open FAN', 'Unducted Single FAN' or 'Propfan') unfaired blower in French, it seems necessary to be able to increase this reduction in mass.

[0013] One possible solution to overcome this problem is to design and / or manufacture hollow aeronautical parts (known as 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 generate thrust. This pressure can deform the part where it is hollow, crushing the cavity and thus, for example on a fan blade, potentially reducing its efficiency considerably 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 helps to meet the need for weight reduction and improve the mechanical properties of the part and limit or even completely eliminate skin crushing.

[0016] However, during turbomachine operation, the components (particularly the blades) are subjected to mechanical stresses, primarily bending, under the influence of the airflow. To mitigate this stress, it is known—as in EP3511240—to add one or more inserts that act as stiffeners. If the stiffener is, or includes, a spar, and the composite component is a blade, the spar can also serve as the blade's attachment point to the turbomachine's disk, thus creating a connection between the blade's aerodynamic skins, the honeycomb material within the cavity, and the rest of the turbomachine.

[0017] Manufacturing hollow parts composed of numerous sub-components is always challenging because handling them before they are bonded 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] Sourcing a part from 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 overall 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] There is a need to improve the compactness and reduce the mass, the number of weaving layers and the manufacturing cost of such a part. Description of the invention

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

[0022] More specifically, the present invention relates in particular to a part (which can be in three dimensions) 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 a foam (derived from a) polymer, expanded.

[0023] This document also relates to the part having at least one cavity as defined above, for example a single cavity or several cavities.

[0024] The cavity may have a bottom and one or more openings. The positioning of the opening(s) is adapted to improve the mechanical properties of the part and / or to facilitate the introduction of the expanded cellular polymer material into the bottom of the cavity. For example, the opening(s) may be positioned opposite the bottom of the cavity.

[0025] The term "fabric" refers to a surface obtained by assembling threads or fibers that may be arranged in two crossed layers. The term therefore includes a fibrous preform or a woven preform. It can refer to any material, woven or non-woven, and thus to a fabric in the true sense of the word.

[0026] The "fabric" or fibrous structure, and therefore the piece that comes from it, can be formed of any type of weave: two dimensions (2D), three dimensions (3D), in particular.

[0027] By "two-dimensional weaving" or "2D weaving", we mean here a classic weaving method in which each warp thread passes from one side to the other of threads in a single layer of weft.

[0028] By "three-dimensional weaving" or "3D weaving" we mean here a method of weaving in which at least some of the warp yarns bind weft yarns over several layers of weft.

[0029] The term "part" covers any type of part. It can be an unfinished part, such as a semi-finished part. It can be a preform; the preform of a finished part.

[0030] The term "foam," in the expression "expanding foam," means: A medium resulting from the expansion of an expandable paste capable of expanding to form a foam (a continuous solid phase in which a molecule is dispersed in the form of cells). gaseous phase). The emulsion and the creation of the gaseous phase that generates the foam result from the expansion reaction of a paste that previously existed in a liquid phase. Thus, unlike a traditional foam supplied in solid form (referred to as solid foam hereafter) and therefore having a fixed shape before its use in the production process, this "foam made from an expanded polymer" will be supplied in liquid form (the polymer paste) but becomes solid during the expansion reaction and only has a fixed shape once it has solidified and expanded within the cavity of the part.

[0031] "Solid foam" means: a rigid foam machined directly to the final shape, such as the products used in the State of the Art, the expanding foam used here allowing, on the contrary, to "catch up" with any deviations from the geometric tolerances.

[0032] Among the advantages, a simplification of the manufacturing process can be noted. Other advantages are listed below.

[0033] In this room, the expanded cellular polymer material could be polyurethane. Advantages: a widely available, well-understood, inexpensive material that is very effective for filling volume / space.

[0034] Advantageously, the cavity is delimited by the composite material. More precisely, a wall of the composite material delimits the cavity.

[0035] Advantageously, the component includes at least one insert, in particular a woven one, for example, a three-dimensionally woven one. The insert can be adapted to define a stiffener (also defined below as a possible stringer). The insert is specifically fitted into the cavity.

[0036] In some cases, it is possible to add access to the cavity by disconnecting the leading edge or trailing edge of the part in order to have better access.

[0037] In terms of a manufacturing process for a part (which may be as above) comprising a weave, the process of the invention addresses at least partially the problem stated previously and is thus presented as steps (which may be nested, i.e., carried out at least partially together): - a weaving of the piece, incorporating one or more cavities, - the placement of the part in the first section of an injection mold, - the placement, within the cavity, of a soluble core or a removable, demoldable core, or a flexible membrane, the soluble core or the membrane (including its space internal) occupying the volume of said cavity, - a closure of the injection mold, by means of at least one second part of the injection mold, - an injection of resin into the weave of the part, in order to form a woven part made of composite material, - Demolding the part, outside the injection mold, - depending on the case, dissolution of the soluble core or withdrawal, from the cavity, of the removable core or the flexible membrane, - the application within the cavity of an expansive paste adapted to form a honeycomb material, - waiting for the paste to react and form (preferably completely) the said honeycomb material in the cavity, - removal of any excess alveolar material that may have overflowed from the cavity, if applicable.

[0038] The waiting time will be more than one second (tmin). This waiting time will depend on the specific expanding product used, the manufacturer's recommendations, and production experience, allowing for adaptation to the geometry and volume to be filled. Generally, the delay varies from a few seconds to less than 5 minutes.

[0039] Removing any excess foam material may involve final machining of the part, resulting in a finished part (with the exact desired shape) or a semi-finished part (for example, the addition of certain reinforcements or a surface treatment may still be required). It may also involve deburring and conformity checks (composite material testing, dimensional checks). All of this can be defined as finishing the part. If any excess material is removed, the cavity is already rigid. The foam only needs to fill the cavity. Therefore, if excess expanding foam is removed, it is generally advantageous to wait until the reaction is complete to avoid having to remove this excess in several stages.

[0040] Thus, after waiting for the paste to react and become (preferably completely) the said honeycomb material, one can usefully: - remove any excess expanded material overflowing from the cavity, if applicable, and - check the conformity of the part (composite material check, dimensional checks, etc.), then - to oversee the completion of the piece.

[0041] In the above process, the cellular material will usefully include, as noted above, an expanded cellular polymer material which may therefore be an expanding or expanded foam.

[0042] The use of an expansive polymer material, whose expansion reaction takes place during the densification of the woven preform by the resin, can lead to high porosity rates (gas bubbles in the material due to the gas release produced by the foam expansion reaction) negatively impacting the mechanical properties of the part.

[0043] Using such an expansive material instead of a solid, finished-dimension foam can lead to irregularities in the shape of the part's internal cavity. While these irregularities are less critical than deviations on the external surface (in the aerodynamic flow), they must nevertheless be kept under control.

[0044] All of this therefore raises problems that the present solution seeks to address.

[0045] The weaving of the part (rough or preform) can be three-dimensional, which will facilitate the production of a high-performance industrial part, such as a blade. To best ensure the aforementioned "flexible membrane" function (if it is adopted) on an industrial scale, it is proposed to use: - an inflatable bladder, which will be inflated in the cavity, or - a pre-formed part (reusable or not) made of silicone or polyurethane elastomer.

[0046] Thus, the advantage of an adapted deformation of the flexible membrane, necessary for its placement in the cavity, or even for its removal, will be associated with that of a mechanical resistance adapted to the injection pressure and to the preservation of the required volume of the cavity.

[0047] To promote the strengthening of the woven composite part, 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 here 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 an insert (which can therefore be three-dimensional), which can be adapted to define a stiffener (also defined as a possible spar below), for the part containing the cavity, - the insertion of the woven insert into the cavity of the part.

[0048] However, this solution requires the woven insert to be manufactured independently of the said part with integrated cavity.

[0049] To avoid this and create an insert within this cavity through a local modification of the weave structure, it is also proposed that the weave of the piece include a co-weave with a woven insert (which can therefore be three-dimensional) that the piece will then incorporate. In other words, the weave of the piece (incorporating the cavity) will include a co-weave with a woven insert (which can therefore be three-dimensional) that the piece will then integrate as a single unit.

[0050] In general, and depending on the type of core (soluble or removable) chosen for the formation of the cavity, the geometry of the cavity, and the need for stiffeners or stringers, it will be possible to carry out the densification of these at the same time as that of the preform of the part to be produced, instead of producing these sub-components during separate prior injections.

[0051] Typically, all woven textiles will include an interlacing of threads divided into two categories: "warp threads", which are threads parallel to the selvedges of the fabric, and "weft threads", which are threads perpendicular to the warp threads and interlaced with them, according to a pattern called "weave", the simplest weave consisting of an alternation in which each weft thread passes successively over and under a warp thread, with an offset from one weft to the other (solution called "plain weave").

[0052] Furthermore, providing that the weaving of the part incorporating the cavity includes a debonding will facilitate the formation of the cavity, or housing, inside the fibrous structure that is to form said woven composite part.

[0053] There are two possibilities for applying the expanding paste to the cavity: - either by introducing the paste directly into the cavity, in contact with the wall that borders the cavity, - either the placement of another flexible membrane or hollow flexible bladder in the cavity, the expanding paste being contained (after being introduced) in this other flexible membrane or flexible bladder, said other flexible membrane or flexible bladder forming an interface between the composite part and the paste, then the expanded foam, and being held permanently in place in the mold. This would facilitate the handling of the expanding paste and limit the risk of leaks.

[0054] Besides ease of implementation and the possibility of fairly large-scale production, the advantages of the various aspects of the process just presented are those of the part itself, already presented.

[0055] For the advantages already mentioned, the following is proposed as optional embodiments that can be implemented independently or in combination, in whole or in part, as appropriate: - the cavity has a bottom and one or more openings, and the application 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, - Expanding paste is placed in the cavity, after selecting as the expanding paste an expandable polymer whose gas release during a polyaddition reaction will form 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 forms the said dense cellular material (a well-controlled process reproducible in series and with an initial paste without supply difficulties).

[0056] "Dense" means uniformly and completely filling the cavity with a sufficiently high density to ensure good mechanical performance of the foam in relation to its functions detailed previously. This density, however, remains significantly lower than that of the other constituent materials of the blade, and preferably greater than 50 kg / m³. 3, or even between 100 kg / m 3 and 300 kg / m 3

[0057] 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

[0058] 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 figure 1 along the cutting plane A of figure 1; [Fig. 3] is a cross-section of the blade of figure 1 along the cutting plane B of figure 1; [Fig. 4] is a cross-section of the blade of figure 1 along the cutting plane C of figure 1; [Fig. 5] is a longitudinal section of the blade of figure 1 along the section plane D of figure 1; [Fig. 6] is a longitudinal section of the blade of figure 1 along the section plane E of figure 1; [Fig. 7] is a longitudinal section of the blade of figure 1 along the section plane F of figure 1; [Fig. 8] is a schematic perspective view of the rough fibrous structure after cutting of the outer floating fibers; [Fig. 9] is a schematic perspective view of the rough fibrous structure after cutting the floating threads present on the spar portion of the rough; [Fig. 10] is a schematic perspective view of the resulting fibrous structure, as well as its shaping with conforming pieces. [Fig. 11] schematically represents a variant of the blade in Figure 1, in a state where the part is still only fibrous, in the preform state; [Fig. 12] is a cross-section of the blade of figure 11, along the cutting plane H; [Fig. 13], [Fig. 14], [Fig. 15], [Fig. 16] and [Fig. 17] schematically illustrate successive manufacturing stages, in an injection mold, of a hollow fibrous part, these stages consisting of a densification which may be that of the preform in figure 11, [Fig. 18] schematically represents, according to the same section, the state of the part in figure 11 after said densification and the addition, in the preserved cavity of said hollow part, of an expanding foam; [Fig. 19] schematically represents, according to the same cross-section, a preparatory state for the contribution of the said expanding foam in the cavity, according to one variant, and [Fig. 20] schematically represents, according to the same section, the state of the part in Figure 19 after the expanding foam has been added to the bladder placed in the cavity in the step shown in Figure 19. Description of the embodiments

[0059] The drawings and description below contain elements that can not only help to better understand the present invention, but also contribute to its definition, if necessary.

[0060] The invention applies generally to the manufacture of various parts, particularly 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.

[0061] Figure 1 represents a blade 10 intended to be fixed on an aeronautical turbomachine.

[0062] Like any aeronautical blade (or propeller blade) concerned here, the blade 10 has a free edge, or end, 11 d and, opposite, a foot 12 by which the blade is fixed to a rotor disc 101 of the turbomachine.

[0063] More specifically, the blade 10 comprises an airfoil 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 airfoil 11. The airfoil structure 11 has, in cross-section, a curved profile of variable thickness between its leading edge 11a 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 airfoil 11 extends between a foot edge 11c (or attachment edge to the rotor disk 101) and a free edge (or apex edge) 11d. The foot 12 extends along the transverse direction DT over a length less than the length of the foot edge 11c of the aerodynamic profile 11.

[0064] As shown in Figures 1 to 7, the blade 10 includes a fibrous reinforcement, labeled 20 in some figures, and densified by a resin 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.

[0065] The portion of the longitudinal member 22 may be in one piece: - a part 22a extending inside the aerodynamically profiled 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.

[0066] 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(s) 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 11c 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 11a 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 from the longeron portion 22. The first and second skins 28 and 29 extend between the front and rear edges 21a and 21b of the airfoil structure 21 in the transverse direction and between the intermediate zone 27 and the foot edge 21c of the airfoil structure 21 in the longitudinal direction. The skins 28 and 29 enclose the longeron portion 22. The first and second skins 28 and 29 define, within the airfoil structure 21, first and second recesses 30 and 31 located respectively on one side and the other of the longeron portion 22 in the transverse direction. The first and second recesses 30 and 31 open at the foot edge 21c of the structure. aerodynamic profile 21. A first conformation element 40 is present in the first housing 30.Similarly, a second conformational element 41 is present in the second housing 31.

[0067] Often, conformational elements, such as 40,41, are referred to as "nuclei" in the technique; see below.

[0068] The conforming elements, such as 40, 41, or the cores, can typically each be formed from a solid block, typically a rigid foam element produced by molding or machining from a block of material. Each is either soluble in the cavity or removable (detachable from the cavity).

[0069] As an alternative to the spar portion 22, an insert 300 (which can be defined as a reinforcement insert or stiffener) could extend inside an aerodynamic profile structure where it would then be temporarily surrounded by a conforming element or a pressure membrane occupying the remaining volume of the cavity 230', around the insert 300, according to an embodiment which would for example conform to the schematic illustrations figures 11 to 17.

[0070] Part 22a and the bulging portion 24, or part 22b, could appear as such an insert, corresponding to insert 300.

[0071] In this solution: - dawn 10 becomes dawn or pale 10', - the 20 fibrous reinforcement in 3D woven material remains; it just changes reference point: 20', - the portion of the longeron 22 is therefore replaced by at least one insert or stiffener, such as that 300, 3D woven and ultimately made of the same composite material (resin + fibers) as the fibrous structure 200' if it is not (which is possible) metallic, 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'.

[0072] Applicable in particular in these two cases and as illustrated in the example of figures 8 to 10, the manufacturing process of an aeronautical part according to the invention includes the production of a fibrous structure, not yet impregnated with resin, such as the fibrous structure blank 100 intended to form the fibrous preform of the part to be produced.

[0073] 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 weft yarns. The fiber structure blank 100 is woven in a single piece. The blank comprises, in this example, an aerodynamic profile blank 111, a spar section blank 122, and a flared section blank 112. extending within 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 respective foot and free (or top) parts 100c and 100d of the fiber structure blank, the bulging portion blank 112 extending in the continuation of the spar portion blank 122.

[0074] In the illustrated example, the 3D weave is an "interlock" weave. By "interlock" weave, we mean a weave structure in which each layer of weft yarns connects several layers of warp yarns, with all yarns in the same weft column having the same movement in the plane of the weave.

[0075] Other known types of weaving, including three-dimensional weaving, may be used, such as those described in document 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 reinforcement and a second type of skin reinforcement which make it possible to confer both the mechanical and aerodynamic properties expected for this type of part.

[0076] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0077] As the fibrous blank, whose thickness and width can vary, is woven, as in the example, a certain number of warp threads may therefore not be woven, which makes it possible to define the desired contour and thickness, continuously variable, of the blank 100.

[0078] In addition, during the weaving of the fibrous rough, a debinding 110 can be made within the fibrous rough between successive layers of warp yarns and on a debinding zone(s) Zd.

[0079] In the DL direction, a bond zone ZI in the fibrous rough extends the unbond zone(s) Zd, so that, if H11 is the length of the aerodynamic profile 11, H11 = ZI + Zd.

[0080] More specifically, in the example (see Figure 8), 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 rough spar portion 122 so as to form first and second rough skins 104 and 105 separated from each other. The first and second rough 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.

[0081] Once the fiber structure blank 100 is woven, the floating fibers outside the woven mass are cut, for example by water jet, to define the outer contour of a fibrous structure as illustrated in Figure 8, by way of example. Floating fibers present on the skin blanks 104 and 105 is cut at the lower part of the unfinished fibrous structure to expose the unfinished bulging portion 112 and part of the unfinished spar portion 122, which will later form a blade strut. The floating fibers around the unfinished spar portion 122 and the unfinished bulging portion 112 are also cut by lifting the unfinished skins 104 and 105, as shown in Figure 9, by way of example. For this purpose, first and second slots 107 and 108 are formed between the unfinished skins 104 and 105.

[0082] We then obtain, as illustrated in Figure 10 by way of example, a fibrous structure 200 woven in one piece and having, in this example, an aerodynamic profile 211, a spar portion 222 and a flared portion 212, the aerodynamic profile 211 extending in the longitudinal direction DL between a lower end 211c and an upper end 211d and in the transverse direction DT between a leading edge 211a and a trailing edge 211b. The fibrous structure 200 has a debonding zone(s) Zd extending between the leading and trailing edges 211a and 211b of the aerodynamic profile 211 along the transverse direction DT and between an intermediate part 203 and the root edge 211c of the aerodynamic profile 211 along the longitudinal direction DL.The longeron portion 222 extends inside the aerodynamic profile 211 at the level of the debonding zone(s) Zd set back from the leading and trailing edges 211 a and 211 b along the transverse direction DT and, along the longitudinal direction DL, between an intermediate part 203. located between the lower and upper edges 211c and 211d of the airfoil 211 and the root edge 211c of said airfoil at which the spar portion 222 terminates. 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 root edge 211c of the airfoil. The flared portion 212 is intended to subsequently form the blade root 12.The aerodynamic profile 211 comprises at the level of the debonding zone(s) Zd of the first and second skins 228 and 229 debonded from each other, the first and second skins extending between the leading and trailing edges 211a and 211b of the aerodynamic profile along the transverse direction DT and between the intermediate part 203 and the root edge 211c of the aerodynamic profile along the longitudinal direction DL, the skins 228 and 229 enclosing the portion of spar 222.

[0083] The first and second skins 228 and 229 define, within the airfoil, at least one cavity 230 which, in this 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 this example, open to the outside. In this example, the opening is located at the lower end of the airfoil 211.

[0084] In the alternative combining an insert 300 which can therefore be metallic, as in the example of part in figures 11, 12, it is therefore the insert 300 which replaces the bulging portion 212 and the part 222.

[0085] Thus, in each situation of weaving of part made, at the end of the manufacturing process, in composite material (resin + fibers), as in particular in the rough woven fibrous structure 100 and in the woven fibrous structure 200, at the end of the process, a cavity 230 or 230' will have been integrated in a single piece into the woven structure.

[0086] Furthermore, with these examples of a possible integrated longeron extended by a 12mm foot, or a possible 300mm reinforcement insert forming a stiffener or potential longeron, we were able to: - reinforce the woven piece, at the location of its cavity 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' in the example.

[0087] In other words, insert 300: - either will have been manufactured separately (in a suitable material, such as a metal, or woven, and in two or three dimensions) so as to define a stiffener, with or without foot 12, for the part presenting the cavity, such as 230' in the example, then inserted into this cavity, after the desired preform, 200' in the example, has been woven, - either it will have been integrated in one piece with the said preform, the weaving of the piece (200' in the example) integrating the cavity thus including a co-weaving of such a stiffener; the insert marked 300' figure 15 simulates and schematizes this hypothesis of a dry woven preform allowing the formation of a stiffener after injection of the resin into the mold (see below).

[0088] In the second case, the co-weaving of the reinforcing insert, such as 300', with the woven fibrous structure can be carried out like that of the fibrous structure blank 100, similarly in the second case for the independent weaving of the reinforcing insert 300, but without the cavity.

[0089] 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 or 200' in the example, in a first part 301 of an injection mold 310 of the part concerned (see figures 13, 14 according to an example).

[0090] The hollow impression part of the part concerned in the first part 301 of the injection mold 310 is identified as 330 figure 13.

[0091] As an example, figures 13 to 17 are intended to help understand the part of the process relating to molding the part by injecting resin 60 into the core of the fibers of the fibrous structure, such as 200' in the example.

[0092] Thus, it is first in the part of the impression 330 that the fibrous structure is placed, such as 200' in the example; see example figure 14.

[0093] We can then insert into the cavity, such as that 230' in the example, the core(s) and / or flexible membrane and / or insert(s) and / or stiffener(s) and / or possible spar(s) 300 which are suitable.

[0094] Figure 15 shows the presence of a previously manufactured composite or metallic stiffener 300, or, alternatively, a dry woven preform allowing the formation of a stiffener after injection of resin 60, this woven preform dry which may therefore have been co-woven with the rest of the woven fibrous structure (reference 300').

[0095] In addition, there is the insertion into the cavity or each of the aforementioned, such as 230' in the example, of at least one soluble core or removable core (see references 40,41 figure 10) or of a flexible membrane 430' pressurized, in the cavity, via a pressurized gas inlet 432, as is the case in the example of figure 15.

[0096] In the example in Figure 15, we have even included: - at the bottom of the figure, the case where cavity 230' contains a removable inflatable membrane 430' and, - at the top, an alternative in which, in the cavity 230', a solid core 430” of the same nature as the conformation elements 40,41 would be inserted (arrow 434), around an insert or stiffener 300 or 300'.

[0097] The core 430” incorporates a central volume 436 in the shape of (the part of) the insert or stiffener 300 or 300' located in the cavity 230' which can thus be engaged there.

[0098] Thus, in one way or another, the volume of the aforementioned cavity or cavities, such as 230' in the example, will then be occupied by a core or equivalent and will resist the injection pressure of the resin 60 which can now take place: - within the fibers of the fibrous structure, such as 200' in the example, including the insert or stiffener if it is a woven part, such as the dry woven preform 300'), - but not in said cavity.

[0099] For this, another part 303 of the mold 310, with an adapted imprint, will close the mold, as shown schematically in figure 16, and resin 60 will be injected under pressure (it can be at room temperature) into the two parts of the imprint; arrow 438, within the preform in order to densify it and form the composite material.

[0100] When the mold is reopened (as in the example in Figure 17), the resin 60 has infiltrated both parts of the mold cavity, but not the cavity, such as 230' in the example, thus densifying the fibrous structure and forming the aforementioned composite material.

[0101] The resulting rough part can then be removed from the mold and deburred.

[0102] If cavity 230, 230' contains at least one 430' core, then it is dissolved if it is soluble, or removed if it is a removable core or a removable 430' membrane.

[0103] With cavity 230, 230' becoming accessible, it is now that we can add a quantity of expanding paste 50 adapted to occupy all the available volume.

[0104] We then wait for the paste 50 to react to form a foam, the expanded paste being suitable to fill the cavity and to ensure the maintenance of the shape, in operation, of the final part obtained.

[0105] Any excess foam overflowing from the cavity can then be removed, if necessary, and then the conformity checks of the part can be carried out (composite material check, dimensional checks) and the resulting composite part can be finished.

[0106] The advantage of only adding the 50 expansive paste after molding, and therefore after densification of (each) woven piece, is precise control of the cavity geometry, in addition to control of the external geometry of the piece.

[0107] As already mentioned, this limits the risks: - a high porosity rate (gas bubbles in the material due to gas release produced by the foam expansion reaction) negatively impacting the mechanical properties of the part, and - irregularities in the shape of the internal cavity of the part.

[0108] Furthermore, such a cavity solution filled with expanded foam has the advantage of reducing the cost of the part compared to a solid foam, because the soluble or removable core generally has a low cost per part.

[0109] Another advantage may be the guarantee that the gas release producing the expansion of the foam 50 will not contaminate the resin 60 of the composite densification, which could have been the case with a chronology as follows: supply of expansive paste 50 - waiting - closing of the mold - densification by injection of the resin 60, said pollution being able to result in porosity (gas bubbles) in the matrix of the composite material, with the consequence of a reduction in the mechanical properties of the material.

[0110] The use of an expansive paste 50 instead of a solid foam, if the (one) said cavity of the part is to contain an insert 300, also makes it easier to avoid a typically made invitation - see above - to weave the first and second 3D woven preforms mentioned above separately, in order not to create a constraint on the assembly.

[0111] By removing this constraint, we will then be able to more easily consider the aforementioned possibility of co-weaving: - the (every) second preform (and therefore any stiffener(s) and / or stringer(s)), - with the first preform, such as the fibrous structure 100, - this always before molding in the mold 310 then placing the expanding / foaming paste 50.

[0112] The 3D weaving of the first preform, as well as the unbundling (Zd zone mentioned above) and a local adaptation of the weave structure, will then allow the formation of said cavity, such as 230 or 230'. It will thus be possible to create one or more stringers or stiffeners in this cavity by a local modification of the weave structure.

[0113] The expansive nature of the alveolar material 50 will allow it to adapt naturally to all the geometries of the cavity in the densified part, conforming to the shapes at the ends of the cavity as well as around the stiffener(s) and / or stringer(s), if they exist.

[0114] Regarding the application of the 50 expanding paste, the following may be particularly relevant: - that each cavity, such as 230 or 230', has a bottom 49 and an opening 51, and - that this installation includes the introduction of the expanding paste at the bottom 49 of the cavity, so that the expanding paste 50 expands from the bottom 49 towards the opening 51, thus limiting the risks of excessive overflow outside the cavity.

[0115] If the expansive paste 50 can be used directly in contact with the fiber + resin composite, the use of a flexible membrane, such as a flexible (hollow) bladder, such as 431 in the example of figures 19,20, filled with the expansive paste 50 may be considered, optionally.

[0116] Such a flexible membrane, hereafter referred to as a "flexible bladder" to avoid confusion with the possible 430' membrane, will a priori be thinner than the 430' membrane, since the injection of the 60 resin has already taken place and therefore the integrity of the cavity is already ensured.

[0117] If present, a flexible bladder, such as 431, is designed to contain the expanding paste 50 and then the resulting expanded cellular polymer, thus facilitating processing. However, omitting 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 is preferable to isolate the different components and therefore maintain the use of a flexible bladder.

[0118] The choice between these two options may also be dictated by the mechanical strength of the interface created between the expanded cellular material 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. A solution without a flexible bladder seems more favorable in this respect, as it allows for direct physicochemical contact between the expanded cellular material and the resin of the composite material.

[0119] With a flexible bladder, opening 51 must allow: - the insertion of the flexible bladder 431 into said cavity; - the addition of the expansive paste 50 to the bottom 49 of this cavity, in the bladder, so that the expansive paste 50 progresses by expanding from the bottom of the cavity towards its opening 51, without creating a vacuum pocket, during its evolution into a foam, by pressing the bladder against the wall 237 of the cavity (see figure 20, for example).

[0120] As an alternative to a flexible bladder 431 open on the side of the opening 51, as in the example of figure 20, a closed bladder, provided only with an inlet 433, could be provided, the inlet 433 being adapted to the supply of the expansive paste 50 into the bladder (see figure 19, for example).

[0121] In any case, once in place in the cavity, the soft bladder will remain there permanently.

[0122] As an expansive material, the well-known expandable polymer polyurethane can be used, the release of CO2 from which during the polyaddition reaction forms a cellular material, like a dense foam, commonly used in industry.

[0123] 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 necessary and of the disc if it is a blade, etc.

[0124] Regarding the injection of resin 60 into the closed mold 310, and therefore the densification of the fibrous preform under consideration, if slots 107 and 108 are present on the leading and trailing edges 211a and 211b, they will preferably be closed by stitching before densification, such densification consisting of filling the porosity of the preform, in all or part of its volume, with the constituent material of the matrix.

[0125] The matrix of the composite material can be obtained using a method known per se via 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 (which the term "organic precursor" can replace), possibly diluted in a solvent. The mold 310 in which the preform will be placed can be sealed, thus providing an internal cavity in the shape of the desired final molded part.

[0126] 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.

[0127] The transformation of the precursor into an organic matrix, namely its polymerization, is, as is known, carried out (by heat treatment or otherwise) after the removal of any solvent and crosslinking of the polymer, with the preform still 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 Resin "2896" from 3M, or from liquid precursors of carbon or ceramic matrices.

[0128] In the case of carbon or ceramic matrix formation, 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.

[0129] If, instead of a three-dimensional part, a two-dimensional (2D) part is desired, this can be achieved by draping the 2D fabric over each section of the mold, or, for a blade, by draping the upper surface of the blade over the expanding clay and then closing the mold. Therefore, if a 2D weave is planned, it is suggested 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.

[0130] Furthermore, the densification of the fibrous preform can be achieved using 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 within this internal space between the point of resin injection and the resin's discharge ports in order to control and optimize the impregnation of the preform by the resin.

[0131] In relation to the installation of any insert, such as 300, in the cavity which receives it, any means of support necessary for an appropriate positioning of the insert in the cavity will be used if necessary (centering arm, etc...).

Claims

Claims

1. A three-dimensional part comprising a composite material including a fabric and a resin, the part having at least one cavity (230,230') filled with a honeycomb material (50), each cavity having a bottom (49) and one or more openings (51), characterized in that the fabric is formed by three-dimensional weaving and in that the honeycomb material comprises an expanded honeycomb polymer material.

2. Part according to the preceding claim, in which the cavity is delimited by the composite material.

3. Part according to one of the preceding claims, comprising at least one insert adapted to define at least one stiffener.

4. Part according to the preceding claim, in which the insert is arranged in the cavity.

5. A method of manufacturing a composite part, the method having steps of: - weaving the part, by integrating at least one cavity (230,230') having a bottom (49) and an opening (51) or several openings, - placing the part in a first part (301) of an injection mold (310), - placement, in the cavity (230,230'), and which occupies its volume, of a soluble or removable, demouldable core (40,41,430”), or of a flexible membrane (430'), - closing the injection mold, by means of at least a second part (303) of the injection mold, - injection of resin (60) into the weaving, in order to form a woven piece of composite material, - demolding of the part, out of the injection mold, - depending on the case, dissolution of the soluble core or removal, from the cavity, of the removable core or the flexible membrane, - placing in the cavity an expansive paste (50) suitable for forming a honeycomb material, - waiting for the paste to react to form said honeycomb material, in the cavity, - removal of excess honeycomb material that has overflowed from the cavity, if applicable.

6. The method of claim 5, wherein the weaving comprises weaving the piece in three dimensions.

7. Method according to claim 5 or 6, in which an inflatable bladder, which is inflated in the cavity, or a preformed part made of silicone or polyurethane elastomer is used as the flexible membrane.

8. A method according to claim 5, 6 or 7 further comprising, between the weaving of the part incorporating the cavity (230,230') and the step where the expansive paste is contained in the cavity: - weaving an insert (300') for the part presenting the cavity, - inserting the woven insert into the cavity (230,230') of the part.

9. A method according to claim 5, 6 or 7, wherein the weaving of the part incorporating the cavity comprises co-weaving with a woven insert (22) which said part then incorporates, in one piece with it.

10. Method according to one of claims 5 to 9, in which weaving of the part integrating the cavity comprises a delinking (110) carried out inside the part.

11. Method according to one of claims 4 to 9 wherein the placement of the expansive paste (50) comprises its introduction at the bottom of the cavity (230,230') so that the expansive paste expands from the bottom towards the opening.

12. Method according to one of claims 5 to 11, in which the placing of the expansive paste (50) in the cavity (230,230') comprises the prior selection of an expandable polymer whose gas release during a polyaddition reaction forms said cellular material, which is dense in the cavity.

13. The method of claim 12, wherein the selection of the expandable polymer comprises the selection of polyurethane, the release of CO2 from which during the polyaddition reaction forms said dense cellular material (50).

14. A method according to one of claims 5 to 11, wherein the foamed material comprises an expanded foamed polymer material.

15. Method according to one of claims 5 to 14, in which, for placing the expansive paste in the cavity: - either paste (50) is introduced directly into the cavity, in contact with the wall (237) which limits the cavity, - either another flexible membrane or flexible bladder (431) is placed in the cavity, the expansive paste being introduced into this other flexible membrane or flexible bladder, said flexible membrane or flexible bladder (431) thus forming an interface between the part composite and the paste (50), then the expanded foam, and being held in place in the cavity (230,230'), permanently.

Images