Method for manufacturing a turbomachine composite material part incorporating in-situ repair of a warp fiber

Abstract

Method for manufacturing a part made of composite material for a turbomachine incorporating in-situ repair of a warp fiber. The invention relates to a method for manufacturing a part made of composite material such as a blower blade with in-situ repair of a warp fiber which comprises the steps: 1) weaving of a fibrous blank; 2) shaping of the fibrous blank to obtain a fibrous preform; 3) densification of the fibrous preform with an organic matrix so as to obtain the part made of composite material; characterized in that during step 1): i) a break point is detected on a warp fiber (11), ii) a thermoplastic polymer (13) is applied to the warp fiber (11) at the detected break point, iii) the two free ends (11a, 11b) of the warp fiber (11) are welded together by polymerizing the thermoplastic polymer (13) so as to eliminate the break point. Figure for the summary: Fig. 3.

Description

Title of the invention: Method for manufacturing a turbomachine composite material part incorporating in-situ repair of a warp fiber

[0001] The invention relates to a method for manufacturing a turbomachine component made of composite material, comprising repairing at least one of the warp fibers during the weaving of the fiber blank of said component. The invention relates more particularly to the manufacture of fan blades and fan housings.

[0002] A turbomachine is designed to provide the thrust necessary for the propulsion of an aircraft. It classically comprises a compressor, a combustion chamber, and at least one turbine to drive the compressor in rotation. The turbomachine further comprises, upstream, considering the direction of an airflow admitted into the turbomachine, a fan to accelerate the airflow from upstream to downstream within the turbomachine.

[0003] A blower has a central disk rotating about an axis of rotation passing through its center. A plurality of blades are mounted on the central disk, distributed around its circumference. To this end, the disk has, at its periphery, a series of recesses, and each blade includes a corresponding foot. Thus, each blade can be fitted into a corresponding recess of the central disk and retained at its periphery by means of mechanisms known in the prior art.

[0004] Fan blades are large in size to generate a significant portion of the turbomachine's thrust. In addition to being subjected to mechanical stresses due to centrifugal force, they can be exposed to impacts from various objects (birds, gravel, ice blocks, sand, etc.), which can damage them. In summary, fan blades are subjected to significant mechanical and thermal stresses and must meet strict weight and size requirements.

[0005] Previously made of metallic material, blades are now more often manufactured from composite material. This makes it possible to obtain blades with a lower overall mass than the same parts made of metallic material while offering equivalent, or even superior, mechanical strength and heat resistance.

[0006] Furthermore, in an aircraft gas turbine engine, the fan casing fulfills several functions. It defines the air intake duct in the engine, possibly supports an abradable material opposite the fan blade tips and / or a sound wave absorption structure for acoustic treatment at engine inlet and incorporates or supports a retention shield.

[0007] For the same reasons as for the blower blades, the blower housings which were previously made of metallic material are now made of composite material.

[0008] Thus, the use of composite materials in the aeronautical industry is now commonplace, particularly because these materials offer interesting mechanical performance for relatively low masses, resulting in reduced manufacturing costs.

[0009] In the context of the present invention, the term "composite material part" means a part comprising a fibrous preform obtained by weaving fibers that have subsequently been densified by a matrix. The fibers provide mechanical reinforcement, and the matrix ensures the part's structural integrity. The matrix thus fills the porosity of the fibrous preform.

[0010] The process for manufacturing a turbomachine composite material part containing a fibrous preform densified by a matrix comprises the following steps: - the creation by weaving (preferably by three-dimensional weaving) of a fibrous blank; - shaping the fibrous blank to obtain a fibrous preform; - the densification of the fibrous preform by a matrix in order to obtain said part in composite material.

[0011] The fibrous blank is obtained by weaving, preferably by three-dimensional weaving (also known as "3D weaving" or "multilayer weaving") using a jacquard-type loom on which a bundle of warp fibers has been arranged, decomposing into a plurality of layers and extending in the longitudinal direction of the fibrous blank to be woven, the warp fibers being linked by weft fibers also arranged in a plurality of layers.

[0012] The matrix is ​​generally an organic matrix.

[0013] The densification of the fibrous preform is implemented with a process well known to those skilled in the art, which is the resin transfer molding process, also known as the "RTM process", RTM being the English acronym for "Resin Transfer Molding".

[0014] However, during weaving, particularly three-dimensional weaving, of the fibrous blank, one or more warp fibers may break. Indeed, during weaving, because the warp fibers are alternately pulled upwards or downwards to create the weave pattern, they are subjected to greater stress. mechanical stresses on the weft fibers; which can sometimes lead to the breakage of one of these warp fibers.

[0015] Since a loom is not configured to detect a possible break in one or more warp fibers, only an operator can visually identify this problem, which can have detrimental consequences on the mechanical properties of the final composite part. Therefore, it is essential, as soon as a warp fiber breaks, to stop weaving and repair the broken warp fiber.

[0016] The operator can detect a possible break in a warp fiber when the last row of weft fibers has been brought back by the reed against the fiber blank being woven. If such a break is detected, the operator stops the loom and carries out a repair.

[0017] The current repair solution available to the operator consists of pulling together the two free ends of the broken warp fiber to temporarily attach them to the end of the fiber blank opposite the end of the fiber blank that was being woven just before the loom stopped. This repair method is unsatisfactory because, when the operator pulls on the two free ends of the broken warp fiber, weft fibers adjacent to this broken warp fiber can be crushed.

[0018] A significant volume of the weave can therefore be disordered around the repaired weave area. It should be noted that this weave disorder has a greater impact when the warp fiber breakage occurs in a deeper layer of warp fibers. This results in anomalies in the weave area, which are referred to as "repaired broken warps," more commonly known by the English term "pull-through," and which have a significant impact on the material integrity of the composite part.

[0019] In the context of the present invention, "material health of the composite material part" means all the physico-chemical and microstructural characteristics of said composite material.

[0020] In other words, this disorganization of the weave in the repair zone can have very damaging consequences on the mechanical properties of the final part made of composite material.

[0021] Therefore, considering these drawbacks and the detrimental effects on the mechanical properties of the final composite part inherent in the current repair method, the inventors sought to develop a new method for repairing warp fibers broken during the weaving of a fibrous blank in the manufacture of a turbomachine composite part that does not result in disordering the weaving zone repaired. Moreover, unlike the known state-of-the-art repair method, this new repair method also has the advantage of having no impact whatsoever on the material health of the resulting composite part, regardless of the depth at which the warp fiber break occurred.

[0022] Thus, the invention relates to a method for manufacturing a part made of composite material for a turbomachine incorporating an in situ repair of at least one warp fiber, said manufacturing method includes at least the following steps: 1) a fibrous blank is produced by weaving with a loom; 2) the fibrous blank is shaped to obtain a fibrous preform; 3) The fibrous preform is densified by an organic matrix in order to obtain said part in turbomachine composite material, said densification being carried out at a densification temperature and with a liquid composition comprising a precursor of the organic matrix, said manufacturing process is characterized in that during step 1): (i) at least one break point is detected on at least one warp fiber, the at least one break point generating two free ends of warp fiber, (ii) at least one thermoplastic polymer is applied to the at least one warp fiber at the level of the at least one detected break point, said thermoplastic polymer being chosen so as to be in a viscous liquid form at the densification temperature of step 3), iii) the two free ends of at least one warp fiber are welded together by polymerizing said thermoplastic polymer so as to eliminate said at least one break point detected on said at least one warp fiber.

[0023] In the context of the present invention, "an in situ repair of at least one warp fiber" means that said repair is carried out during the manufacturing process of a part made of composite material of turbomachine according to the invention following the detection of at least one break point on at least one warp fiber.

[0024] In the context of the present invention, "the thermoplastic polymer is in a viscous liquid form" means that the thermoplastic polymer is liquid while being thick and flowing with difficulty. In other words, said thermoplastic polymer is liquid and exhibits a certain viscosity, for example, a viscosity between 10 and 10,000 mPa·s (milliPascal·seconds).

[0025] Following the welding step iii), the broken warp fiber is thus repaired. The weaving process (in particular three-dimensional weaving) can resume under perfectly normal conditions.

[0026] It should be noted that, unlike the prior art repair method of extracting the two free ends of the broken warp fiber and then attaching them together, this repair is performed by welding using a polymer thermoplastic does not create any disruption to the weave, particularly in the area of ​​the weave thus repaired.

[0027] In other words, the solution for repairing the broken warp fiber proposed by the present invention has the advantage of not disrupting the weaving process, allowing weaving to continue under completely normal conditions, and also of not disorganizing (for example, by crushing) the weft fibers adjacent to this repaired warp fiber, as is the case with the prior art repair method. These advantages mean that the three-dimensional weaving process is in no way disrupted by this repair solution according to the invention and can continue completely normally after the repair.

[0028] The warp fiber repair solution according to the invention has the additional advantages of being a reliable and easy-to-implement repair method. Indeed, the welding technique with a thermoplastic polymer (thus acting as a "bond" for the two free ends of the broken warp fiber to be welded together), which is described in more detail below, is a technique perfectly mastered by those skilled in the art, reliable, and allowing for meticulous repairs.

[0029] Because the thermoplastic polymer is in a viscous liquid form at the densification temperature, during densification step 3, the thermoplastic polymer that had polymerized through welding will revert to a liquid state (more precisely, a viscous liquid). This has the advantage, during this densification step 3, of preventing the formation of a mass of material around the former break point of the warp fiber, which could have negative consequences on the material integrity of the resulting composite part (for example, a reduction in its mechanical properties).

[0030] Thus, the warp fiber repair solution as proposed by the present invention has the advantage of having no impact on the material health of the resulting composite material part.

[0031] Preferably, the weaving is a three-dimensional weaving.

[0032] Preferably, the turbomachine part is a fan blade or a fan housing. More preferably, the turbomachine part is a fan blade.

[0033] Preferably, at least one breaking point is detected according to step i) when the last row of weft fibers has been brought back by a reed of the loom against the fiber blank being woven.

[0034] As explained above, the thermoplastic polymer is appropriately chosen to be in a viscous liquid form at the densification temperature of step 3). This means that after polymerizing in step iii), the thermoplastic polymer becomes viscous liquid again during densification step 3).

[0035] Indeed, a thermoplastic polymer has the property of softening (even becoming a viscous liquid) when heated and hardening again when cooled. This softened state allows for the mechanical deformation of the thermoplastic polymer. The deformation is stopped by cooling the thermoplastic polymer.

[0036] Advantageously, the glass transition temperature of the thermoplastic polymer is lower than the densification temperature of step 3) so that the thermoplastic polymer becomes liquid again (namely a viscous liquid) during this step 3). In the context of the present invention, "glass transition temperature" means the temperature range in which the thermoplastic polymer changes from a soft / rubbery state to a solid / glassy state, or vice versa.

[0037] The densification temperature of step 3) can advantageously be between 150°C and 180°C.

[0038] Advantageously, the thermoplastic polymer is chemically compatible with the precursor of the organic matrix. This ensures optimal implementation of densification step 3).

[0039] Advantageously, the thermoplastic polymer is appropriately chosen so that it does not cause the formation of phases within the organic matrix during densification step 3). This could indeed have a negative impact on the mechanical properties of the resulting composite part.

[0040] The thermoplastic polymer can, for example, be chosen from among styrenes, vinyls, polyesters, cellulosics, acrylics, polysulfones and imides, taken alone or in mixtures thereof. For example, it could be polystyrene, acrylonitrile butadiene styrene, polymethyl methacrylate, polyethylene terephthalate glycol, polycarbonate, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride or polyurethane.

[0041] The selection of a suitable thermoplastic polymer for implementing the present invention is perfectly within the capabilities of a person skilled in the art. If necessary, a person skilled in the art may carry out experimental tests to confirm their choice of thermoplastic polymer. For example, they may ensure that the chosen thermoplastic polymer is chemically compatible with the precursor of the organic matrix and that it does not lead to the formation of phases within the organic matrix during densification step 3).

[0042] Step iii) of welding can be carried out using any suitable technique for welding thermoplastic polymers. The implementation of step iii) is within the capabilities of a person skilled in the art. For example, it could be a laser welding technique, by ultrasound, by infrared, by microwave, by friction, or even by hot gas (for example by hot air).

[0043] To best illustrate the implementation of the invention, steps 1) to 3) of the manufacturing process for a turbomachine composite material part according to the invention are described in more detail below. The technical characteristics of these steps are conventional and thus perfectly within the grasp of a person skilled in the art.

[0044] Step 1) of weaving (in particular three-dimensional weaving) of a fibrous blank is carried out with fibers (or also called "strands" or "yarns") which can be chosen from carbon fibers, glass fibers, silica fibers, basalt fibers, silicon carbide fibers, alumina fibers, aramid fibers and polyamide fibers, taken alone or in mixtures thereof.

[0045] The fibrous blank is woven in one piece.

[0046] Step 2) of shaping the fiber blank may initially consist of a cutting step of the fiber blank, in particular a cutting of the non-woven fibers of the fiber blank and / or a cutting carried out in such a way that the fiber blank substantially has the shape of the composite part to be obtained. The cutting step may, for example, be carried out by laser or water jet, depending on the desired shape and dimensions of the composite part.

[0047] Step 2) of shaping the fiber blank can also consist of compacting the fiber blank. To do this, the fiber blank (possibly cut as explained above) can be placed in a compacting and forming tool. Compaction pressure is then applied to the fiber blank to obtain a fibrous preform of the composite part to be manufactured.

[0048] In other words, shaping step 2) can consist of a cutting step and / or a compacting step of the fibrous blank so as to obtain a fibrous preform.

[0049] The fibrous preform is then extracted from the compaction and forming tooling to be transported to a densification tooling for the fibrous preform.

[0050] In one embodiment of the invention, the densification step (3) may be an RTM process, and the precursor of the organic matrix may be a thermosetting resin. Thus, in this embodiment, in step 3), the liquid composition may comprise at least one thermosetting resin. It may further comprise other constituents, for example, a diluent (in particular, a diluent that reacts with said resin).

[0051] Thermosetting resins suitable for an RTM process are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of the resin's chemical nature is determined according to the thermomechanical stresses to which the part will be subjected. composite material. In the context of the present invention, "low viscosity thermosetting resin" means a thermosetting resin whose viscosity can be between 10 and 1000 mPa.s.

[0052] Preferably, the thermosetting resin is a resin selected from epoxy, bismaleimide, and polyimide resins. Preferably, the resin is an epoxy resin, such as, for example, the high-performance epoxy resin sold under the trade name PR 520 by CYTEC.

[0053] In a preferred embodiment of the invention, the precursor of the organic matrix is ​​an epoxy resin and the fibers are carbon and / or glass fibers.

[0054] Step 3) of densifying the fibrous preform can be carried out in the following manner in an injection mold: - the fibrous preform is placed in a sealed cavity of the injection tool, said cavity being shaped into an impression and the injection tool is closed; - optionally, the fibrous preform can be compacted; - a liquid composition containing the precursor of the organic matrix (for example a thermosetting resin) is injected, possibly under pressure, into said cavity to impregnate the entire fibrous preform; - the liquid composition is transformed into an organic matrix, for example the thermosetting resin is polymerized by heat treatment and by maintaining pressure within the cavity, in order to obtain the part in composite material.

[0055] During the injection of the liquid composition into the cavity, the fibrous preform is impregnated with the liquid composition. The fluidity of the liquid composition is chosen appropriately to ensure that it penetrates the fibers effectively, even when injected under reduced pressure. In the context of the present invention, the fluidity of the liquid composition refers to its ability to flow without resistance within the fibers. A pressure gradient can be established within the cavity between the injection point and the liquid's discharge ports to control and optimize the impregnation of the fibrous preform by the liquid composition. The liquid composition spreads within the preform and conforms to the shape of the cavity's impression.

[0056] Following the step of transforming the liquid composition into an organic matrix, the resulting composite material part is rigid and has a shape corresponding to that of the mold cavity. In this respect, when the composite material part is a blower blade, the mold cavity may have a twisted shape.

[0057] Following densification step 3), the resulting composite part is demolded. Optionally, the composite part is post-cured to improve its thermomechanical characteristics (namely a (increase in its glass transition temperature). Then, the part is trimmed from composite material to remove excess liquid composition and the chamfers are machined.

[0058] At the end of the manufacturing process according to the invention, no further machining is necessary, the part in composite material being molded, it meets the required dimensions.

[0059] The invention will be better understood with the aid of the detailed description set forth below with reference to the accompanying drawings representing, by way of non-limiting examples, a blower blade obtained according to the manufacturing process according to the invention, as well as diagrams of the warp fiber repair solution proposed by the present invention.

[0060] [Fig.1] Fig.1 is a schematic perspective view of a composite material fan blade of an aircraft turbomachine obtained according to the manufacturing process according to the invention.

[0061] [Fig.2] Fig.2 is a very schematic, cross-sectional, grid view of an area of weaving around a breaking point of a warp fiber.

[0062] [Fig.3] Fig.3 is a very schematic, cross-sectional view of the weaving area represented in [Fig.2] after implementation of step iii) of welding with a thermoplastic polymer of the manufacturing process according to the invention.

[0063] Fig. 1 schematically and in perspective represents a fan blade 1 made of composite material of an aircraft turbomachine obtained according to the manufacturing process of a part made of composite material according to the invention.

[0064] Dawn 1 spreads: - along a longitudinal direction L between a foot 2 and a free end 3, and - along a transverse direction T between a leading edge 4 and a trailing edge 5 (more precisely, a trailing edge of the gases flowing in the turbomachine, not shown).

[0065] The foot 2 has a dovetail shape and is shaped to engage in a recess of complementary shape in a turbine rotor disk (not shown), in order to retain the blade 1 on this disk. Between the foot 2 and the free end 3, the blade 1 comprises a strut 6 and a blade 7 located between the strut 6 and the free end 3. The blade 7 has a twisted aerodynamic profile. In addition, a metal shield 8 extending along the leading edge 4 is bonded to it after the manufacturing process according to the invention has been carried out. The metal shield 8 serves to reinforce the leading edge 4.

[0066] To explain the repair of a warp fiber according to the present invention, [Fig. 2] schematically represents, in cross-section, a weft area 14 of a fibrous blank comprising carbon weft fibers 9 and carbon warp fibers 10, 11. More specifically, in this weft area 14, the warp fiber 11 has a breaking point 12 such that said warp fiber 11 has a first free end 1a and a second free end 11b.

[0067] The warp fibers 10 are defect-free warp fibers and the warp fiber 11 is a broken warp fiber on which a repair according to the invention is implemented as shown very schematically in [Fig.3].

[0068] In [Fig. 3], reference numeral 13 designates a thermoplastic polymer which has been polymerized in such a way as to weld together the first free end 1 and the second free end 11b of the broken warp fiber 11 to eliminate the break point 12 visible in [Fig.2]. The weld performed is, for example, a laser weld here.

Claims

Demands

1. A method for manufacturing a turbomachine composite material part (1) incorporating an in-situ repair of at least one warp fiber (11), said manufacturing method comprising at least the following steps: 1) a fibrous blank is produced by weaving with a loom; 2) the fibrous blank is shaped to obtain a fibrous preform; 3) the fibrous preform is densified with an organic matrix to obtain said turbomachine composite material part, said densification being carried out at a densification temperature and with a liquid composition comprising a precursor of the organic matrix, characterized in that during step 1): i) at least one break point (12) is detected on at least one warp fiber (11), the at least one break point generating two free ends (1a, 11b) of warp fiber (11), ii) at least one warp fiber (11) is appliedat the level of at least one detected break point (12), at least one thermoplastic polymer (13), said thermoplastic polymer (13) being chosen so as to be in a viscous liquid form at the densification temperature of step 3), iii) the two free ends (lia, 11b) of the at least one warp fiber (11) are welded together by polymerizing said thermoplastic polymer (13) so as to eliminate said at least one detected break point (12) on said at least one warp fiber (11).

2. Method of manufacturing a part of a turbomachine (1) made of composite material according to claim 1, characterized in that said part made of composite material is a blower blade (1) or a blower housing.

3. Method of manufacturing a part of turbomachine composite material (1) according to claim 1 or 2, characterized in that the densification temperature of step 3) is between 150°C and 180°C.

4. A method for manufacturing a turbomachine composite material part (1) according to any one of claims 1 to 3, characterized in that the thermoplastic polymer (13) is chosen among styrenes, vinyls, polyesters, cellulosics, acrylics, polysulfones and imides, taken alone or in mixtures thereof.

5. Method of manufacturing a part of turbomachine (1) made of composite material according to any one of claims 1 to 4, characterized in that step iii) of welding is carried out with a welding technique selected from laser welding, ultrasonic welding, infrared welding, microwave welding, friction welding or hot gas welding.

6. Method of manufacturing a part of a turbomachine (1) made of composite material according to any one of claims 1 to 5, characterized in that step 1) of weaving a fibrous blank is carried out with fibers (9, 10, 11) which are selected from carbon fibers, glass fibers, silica fibers, basalt fibers, silicon carbide fibers, alumina fibers, aramid fibers and polyamide fibers, taken alone or in mixtures thereof.

7. Method of manufacturing a part of turbomachine (1) made of composite material according to any one of claims 1 to 6, characterized in that step 2) of shaping consists of a cutting step and / or a compacting step of the fibrous blank so as to obtain a fibrous preform.

8. A method for manufacturing a part of a turbomachine (1) made of composite material according to any one of claims 1 to 7, characterized in that the densification step 3) is a resin transfer molding process and the precursor of the organic matrix is ​​a thermosetting resin.

9. Method of manufacturing a part of turbomachine composite material (1) according to claim 8, characterized in that the thermosetting resin is selected from epoxy, bismaleimide and polyimide resins.

10. Method of manufacturing a part of composite material of turbomachine (1) according to claim 9, characterized in that the precursor of the organic matrix is ​​an epoxy resin and the fibers (9, 10, 11) are carbon and / or glass fibers.

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