Method for manufacturing a composite part for a turbomachine

Abstract

Method for manufacturing a part made of composite material for a turbomachine, in particular of an aircraft, comprising the following steps: b) placing a preform (10) made of fibers in a mold (12), c) injecting a polymerizable resin into the mold (12), d) machining the part, e) visually inspecting the part, characterized in that, before step b), there is a step a) in which at least one conformity coating (50) is deposited in the mold (12), the coating (50) having a calibrated thickness (X) and at least one visual appearance identifiable by the operator, said coating (50) being intended to cover at least one zone of the preform at the end of step c) and to be fixed to said at least one zone by said resin, and step e) comprises a verification by the operator of the presence of the appearance in this zone.

Description

TECHNICAL FIELD

[0001] The application relates to a method for manufacturing a part made of composite material for a turbomachine, in particular an aircraft turbomachine. BACKGROUND

[0002] The prior art notably includes documents FR-A1-2 956 057, FR-A1-3 029 134, FR-A1-3 051 386, WO-A1-2020 / 043980 and FR-A1-2 914 877.

[0003] In particular, the use of composite materials is advantageous in the aeronautical industry, since they have interesting mechanical properties at a relatively low mass.

[0004] A method for manufacturing a composite part for the aeronautical industry, known to the person skilled in the art, is the Resin Transfer Molding (RTM) molding method.

[0005] This is a method for manufacturing a part made of composite material based on resin-impregnated fibers. This method is used, for example, to manufacture fan blades and comprises a plurality of successive steps illustrated in Figure 1 .

[0006] First, fibers are woven together to obtain a three-dimensional preform, which is then cut to obtain a preform 10 having approximately the same shape as the blade to be obtained. This preform is then arranged in a closed injection mold 12. The resin is then injected in liquid state by maintaining pressure on the injected resin, while the resin is polymerized by heating.

[0007] The resin used is a very flowable resin that is able to well penetrate the fibers of the preform even when injected at a reduced pressure. During polymerization, under the action of heating, the injected resin successively passes from a liquid state to a gel state and finally to a solid state.

[0008] The composite material of the blade is relatively fragile and in particular sensitive to impacts, and it is known to protect the blade by a metal sheath 14 that is fitted and attached to the leading edge of the blade.

[0009] The sheath can be attached to the blade by arranging the sheath on the preform 10 in the mold 12 so that the sheath is fixed to the blade by the resin. The injected resin impregnates the preform and comes into contact with the sheath to ensure that the sheath is attached to the blade after polymerization and solidification.

[0010] After leaving the mould, the vane 16 is subjected to several finishing operations. The vane 16 is stripped and deburred and is subjected to a first machining operation by sandblasting S1 to adapt the surface condition of the vane to the following operations, namely the gluing step. A strip of anti-abrasion fabric and a polyurethane film (or even the sheath 14 if the sheath has not yet been glued) are glued to the vane 16. The vane 16 is subjected to a second machining operation by sandblasting S2 to adapt the surface condition of the vane to the following operations. The vane 16 is coated with an adhesive primer 18 and then with an anti-erosion paint 20 before being subjected to a final machining step S3 by belt grinding or finishing.

[0011] In order not to damage the vane, and in particular to guarantee the mechanical properties of the vane, in particular on the moulded soffit and the moulded intrados of the vane, the thickness of the material removed by machining cannot exceed a maximum thickness E 最大 . This thickness is relatively small, for example less than or equal to 200 pm.

[0012] By virtue of the prior art, it is difficult to control the thickness of the material removed during the machining operations. One solution is to weigh the vane before and after each machining operation in order to calculate the mass of material removed and to extrapolate the thickness of the material removed on the basis of the cumulative surface area of the machined regions of the vane. However, this solution is not ideal because it assumes that the machining of the regions is uniform and that the thickness of the material removed in the regions is constant, which is not necessarily the case and is difficult to check.

[0013] Furthermore, the mass of the vane is much greater than the mass of the material removed by machining (approximately less than 0.01% of the mass of the vane). This solution is therefore not sufficiently precise and it is necessary to obtain a safety margin by limiting the number of machining operations, in particular the number of sandblasting operations performed on each vane. If we consider that a sandblasting operation generally removes a material thickness E and that the safety margin Ms to be adopted should be 50%, the maximum number N 最大 of machining operations performed on each vane will be:

[0014] N 最大 = Ms · E 最大 / E = 50% · E 最大 / E

[0015] For example, if E 最大 is 40 pm and E is 10 pm, the number N 最大 of machining operations performed on each vane is 2.

[0016] The possible solutions of the present technique are therefore not optimal for controlling the thickness of the material removed during the machining operations, and the present invention proposes a simple, effective and economic solution to this problem. SUMMARY

[0017] The present invention proposes a method for manufacturing a composite material part for a turbomachine, in particular a turbomachine of an aircraft, comprising the following steps:

[0018] b) arranging a preform made of three-dimensional woven fibers in a mold,

[0019] c) injecting a polymerizable resin into the mold to impregnate the preform, forming the part after curing,

[0020] d) machining the part,

[0021] e) visually inspecting the part by an operator to verify at least one conformity criterion,

[0022] characterized in that there is a step a) before step b), during which at least one conformity coating is deposited in the mold, the coating having a calibrated thickness and at least one visual appearance identifiable by the operator, the coating being intended to cover at least one area of the preform at the end of step c) and to be fixed to the at least one area by the resin,

[0023] and step e) comprises verifying by the operator the presence of said appearance in said area to verify said conformity criterion.

[0024] Thus, the method according to the invention comprises 5 steps, in particular an initial step intended to facilitate and optimize the last step of controlling and checking the conformity of the part.

[0025] The conformity coating is an additional layer intended to be applied to the part, dedicated to controlling the conformity of the part. To this end, the coating is deposited in the manufacturing mold for the part, before depositing the preform in the mold and injecting the resin into the mold. The resin will then impregnate the preform and ensure curing the part and bonding the coating to the part.

[0026] The coating is located on one or more areas of the part, in particular on one or more areas intended to be subjected to one or more machining operations. One of the particularities of the coating is that it has a calibrated, i.e. predetermined, and constant thickness. Another particularity of the coating is that it has at least one appearance visible to the operator in the control step e).

[0027] Therefore, it should be understood that, during the control step e), if the operator identifies by sight, on the whole of the machining area / s, the outer appearance of the coating, this means that the machining operation / s on this / these area / s has / have not caused a thickness of material removed greater than the calibrated thickness of the coating. It should also be understood that this calibrated thickness is equal to the maximum thickness of material on the vane that must be removed by machining, therefore, in this case, the vane meets this compliance criterion since it has not been negatively affected by the machining operation.

[0028] If, during step e), the operator identifies by sight, on the whole of the machining area / s, a gap (absence) in the appearance of the coating, this means that the machining operation / s on this / these area / s has / have caused a thickness of material removed greater than the calibrated thickness of the coating, therefore greater than the maximum thickness of material on the vane that must be removed by machining. Therefore, the vane does not meet the compliance criterion and, since the mechanical properties of the vane can have changed, it should be discarded.

[0029] The method according to the application can comprise one or more of the following features taken individually or in combination with each other:

[0030] - the coating has a constant thickness, this constant thickness being comprised between 10 pm and 100 pm,

[0031] preferably between 20 pm and 60 pm, more preferably 40 pm;

[0032] - the visual appearance is a color or the visual appearance comprises a repetition of the same surface pattern;

[0033] - the coating is deposited in the mold by spreading or spraying.

[0034] - the coating is chosen from a pigmented paint, a pigmented resin, a film of glue, a cloth or a combination of the above;

[0035] - the cloth is made of glass fibers or carbon fibers, the cloth is preferably woven and the cloth is preferably impregnated with a polymerizable resin;

[0036] - the coating comprises at least one polymerizable compound, the polymerization of which begins before step b);

[0037] - the coating is deposited on the bottom of the mold;

[0038] - the machining is performed by sandblasting;

[0039] - the method comprises, before step a), a step i) of arranging wedges in the mould, the wedges each having a thickness equal to said calibrated thickness, and the wedges serving to define, between the wedges, a space for depositing said coating, and the method comprises, between steps a) and b), a step ii) of removing the wedges from the mould;

[0040] - the method comprises, between steps a) and b), a step iii) of at least partially polymerizing said coating;

[0041] - the method comprises, between steps a) and b), a step iv) of checking the thickness of said coating, for example by Foucault currents;

[0042] - the part is a blade or a casing. BRIEF DESCRIPTION OF DRAWINGS

[0043] Other characteristics and advantages of the application will become apparent on reading the following detailed description and for the purposes of understanding it, with reference to the attached drawings in which:

[0044] [ Figure 1 ] Figure 1 is a schematic perspective view of a composite aircraft turbomachine blade, which has undergone several operations during a manufacturing method according to the prior art,

[0045] [ Figure 2 ] Figure 2 is a schematic perspective view of a composite aircraft turbomachine blade,

[0046] [ Figure 3 ] Figure 3 is a block diagram showing the steps of a method for manufacturing a turbomachine part according to the application,

[0047] [ Figure 4 ] Figure 4 is a schematic perspective view of a mould for manufacturing Figure 2 a blade,

[0048] [ Figure 5 ] Figure 5 comprises highly schematic cross-sectional views of a blade during some of the operations shown in Figure 1 ,

[0049] [ Figures 6a-6b ] Figure 6a and Figure 6b are respectively a schematic perspective view and a cross-sectional view of a mould of the type shown in Figure 4 , in which a conformal coating in the sense of the application is deposited,

[0050] [ Figures 7a-7b] Figure 7a and Figure 7b are schematic cross-sectional views of a mold in which a coating of resin is deposited, according to two alternative embodiments of the application,

[0051] [ Figures 8a-8b ] Figure 8a and Figure 8b are schematic cross-sectional views of a mold in which a coating of resin is deposited, according to two alternative embodiments of the application,

[0052] [ Figures 9a-9b ] Figure 9a and Figure 9b are schematic cross-sectional views of a mold in which a coating of resin is deposited, according to two alternative embodiments of the application,

[0053] [ Figures 10a-10b ] Figure 10a and Figure 10b are schematic cross-sectional views of a mold in which a coating of resin is deposited, according to two alternative embodiments of the application, and

[0054] [ Figure 11 ] Figure 11 is a schematic perspective view of a composite aircraft turbine casing. DETAILED DESCRIPTION

[0055] The above has been described Figure 1 .

[0056] With reference to Figure 2 , Figure 2 a composite material blade 16 for a turbine is shown, which is for example a fan blade or a straightener blade of the secondary flow in the case of a turbofan engine.

[0057] The blade 16 comprises a blade 22 connected to a root 26 by a strut 24, the root having for example a dovetail shape and being formed to engage in a cell of the rotor disc having a complementary shape, to retain the blade on the disc.

[0058] The blade 22 comprises a leading edge 16a and a trailing edge 16b for the gas flowing through the turbine. The blade 22 has a curved or twisted aerodynamic profile and comprises a camber 28 and a deck 30 extending between the leading edge 16a and the trailing edge 16b.

[0059] The blade 22 is made of a fibrous preform 10 (see Figure 1 ) obtained by three-dimensional weaving of fibers, for example carbon fibers.

[0060] The leading edge 16a of the blade is reinforced and protected by a metal sheath 14 attached to the leading edge 16a. The sheath 14 is for example made of a nickel, cobalt and / or titanium-based alloy.

[0061] This attachment can be carried out on the one hand by co-moulding the preform 10 with the sheath 14, and on the other hand by gluing the sheath 14 with the glue 34.

[0062] Figure 3 is a flowchart showing the steps in a method for manufacturing a composite vane 16, such as the composite vane shown in Figure 2 .

[0063] Steps b) to e) enclosed by the dashed box represent a manufacturing method according to the prior art.

[0064] The first step b) of the method according to the prior art consists in manufacturing a fibrous preform 10 by weaving (preferably three-dimensional weaving) of fibres using a weaving machine, such as a jacquard weaving machine. The resulting preform 10 is raw and can be subjected to operations such as cutting or compression.

[0065] The preform 10 is then arranged in a mould 12 Figure 4 .

[0066] The mould 12 is then closed, for example by means of a counter-mould not shown, and is heated according to a predetermined heating cycle to a temperature preferably between 160 and 200°C, for example 180°C.

[0067] The method comprises a subsequent step c) of injecting a polymerisable resin into the mould 12.

[0068] The resin injected into the mould 12 is intended to impregnate the preform 10.

[0069] The resin is for example an epoxy-based thermosetting resin.

[0070] Figure 5 The image on the left in shows the surface state of the vane 16 as it leaves the mould 12.

[0071] The method then comprises a step d) of machining the vane 16, preferably by sandblasting. This corresponds to the first sandblasting operation S1 mentioned above as shown in Figure 1 . In the example shown in Figure 5 , the second image on the left shows the vane 16 with both faces, i.e. the intrados 16a and the extrados 16b, machined. A certain thickness of material is removed, which exposes some of the fibres 38 of the vane.

[0072] The method then comprises a step e) of checking the part by an operator. In the context of the application, this check is visual and makes it possible to verify at least one conformité criterion according to which the thickness of material removed during the initial machining step d) does not exceed a certain threshold value which is vital to the health of the blade.

[0073] The sheath 14 can then be assembled and attached to the edge of the preform 10 by gluing. The sheath 14 is generally dihedral in shape and defines a groove with a V-shaped cross section into which the edge of the preform is inserted. Glue can be deposited in the groove of the sheath and / or on the edge of the preform 10.

[0074] The polyurethane film 40 is then deposited on the blade 16 (on the convex side in the example shown), and the blade is then subjected to the second machining operation S2 described above to modify the surface condition of the blade, in particular of the region of the blade covered by the film 40. The adhesive primer 18 and the anti-erosion paint 20 are then deposited into each of the faces of the blade, and the blade is then subjected to a machining operation S3 comprising finishing and grinding by belt grinding.

[0075] Figure 3 Additional steps are shown before the manufacturing method according to the application, some of which are optional.

[0076] There is therefore a step a) before step b), in which at least one conformité coating 50 is deposited in the mould 12. This coating 50 serves to cover at least one region of the preform 10 at the end of step c) and to fix to this region by resin.

[0077] This coating 50 has a calibrated thickness and at least one visual appearance that can be identified by the operator.

[0078] It will therefore be understood that, in step e), the operator must check for the presence of this particular appearance in this region in order to verify the conformité of the blade. If this appearance is not visible, it means that the region covered by the coating 50 has been over-machined and the blade should be discarded.

[0079] The coating 50 therefore has a calibrated (i.e. controlled) thickness. This means that this thickness is known and constant over the entire length of the coating. This thickness is for example between 10 pm and 100 pm, preferably between 20 pm and 60 pm, more preferentially 40 pm.

[0080] In the present application, the "visual appearance" means a visible distinction by the naked eye that makes it possible to easily identify the region of the blade coated with this coating from the region that is not coated.

[0081] In a particular embodiment of the application, the visual appearance is a color, for example black, blue, yellow, etc., which is naturally different from the color of the other parts or other layers of the runner.

[0082] In a variant of the embodiment, the visual appearance comprises a repetition of the same surface pattern. For example, the coating can comprise a chevron pattern which is repeated throughout. The pattern can be obtained by, for example, a cloth material, and in particular by a specific weaving pattern of the cloth material in the case of a woven cloth material. Alternatively, the pattern can be achieved by a printed or marked cloth material, which is not necessarily woven.

[0083] As can be seen in Figure 6a and Figure 6b , the coating 50 is intended to be deposited in the mold, for example on the bottom of the mold, by spreading or spraying. Figure 6b A calibrated thickness X of the coating 50 is shown.

[0084] The calibration can be achieved, for example, by steps i) and ii) shown in Figure 3 .

[0085] Before step a), the method comprises a step i) Figure 6b ) of arranging wedges 52 in the mold 12. The respective thickness of the wedges 52 is equal to the calibrated thickness and serves to define, between the wedges, a space for depositing the coating 50.

[0086] Between step a) and step b), the method further comprises a step ii) of removing the wedges 52 from the mold 12.

[0087] Depending on the nature of the coating and as will be discussed in more detail below in connection with more specific examples of embodiments, the coating can comprise at least one polymerizable compound. In this case, in order to limit the displacement and deformation of the coating 50 during steps b) and c), the compound and the coating can be at least partially polymerized before step b).

[0088] Thus, the method in Figure 3 shows, between step a) and step b), a step iii) of at least partial polymerization of the coating 50. The polymerization can be performed by heating or baking the coating. The heating or the baking can be performed before or even after the coating is deposited in the mold 12. In the case where the heating or the baking is performed after the coating is deposited in the mold, the mold serves as a support for the coating for the polymerization.

[0089] In Figure 3The method in

[0090] Figures 7a to 10b Variations of the embodiment of the manufacturing method are shown.

[0091] In Figure 7a and Figure 7b The coating 50 is a paint 54 having a predetermined color, which can be reinforced with a cloth material 56 composed of woven or non-woven fibers. The visual appearance, which will be checked by the operator on the final blade obtained, is the color of the paint.

[0092] In Figure 8a and Figure 8b The coating 50 is a resin 58, which can or can not be colored, and which can be reinforced with a woven or non-woven cloth material. The visual appearance is for example the color of the resin and / or the specific weaving pattern of the cloth material.

[0093] In Figure 9a and Figure 9b The coating 50 is a cloth material 62, which can be pre-impregnated with a resin, reinforced with additional fabric. The visual appearance is for example the color of the cloth material 62 or the resin and / or the specific pattern of the fabric.

[0094] In Figure 10a and Figure 10b The coating 50 is a glue 66, which can be reinforced with a cloth material and / or fabric 68. The visual appearance is for example the color of the glue and / or the specific pattern of the fabric 68.

[0095] Finally, Figure 11 The manufacturing method according to the application is shown not only to be applicable to a blade, but also to other composite parts of a turbomachine, for example a casing 72, when the casing, in particular the outer cylindrical surface of the casing, is subjected to a machining operation.

Claims

1. A method for manufacturing a part (16, 72) made of composite material for a turbomachine, said method comprising the steps of: b) arranging a preform (10) made of three-dimensional woven fibers in a mold (12), c) injecting a polymerizable resin into the mold to impregnate the preform, forming the part after curing, d) machining the part, e) visually inspecting the part by an operator to verify at least one compliance criterion, characterized in that, before step b), there is a step a) during which at least one compliance coating (50) is deposited in the mold, having a calibrated thickness (X) and at least one visual appearance identifiable by an operator, for covering at least one zone of the preform at the end of step c) and being fixed to said at least one zone by the polymerizable resin, and step e) comprises verifying by the operator the presence of the visual appearance in the at least one zone to verify the compliance criterion, wherein the compliance coating (50) comprises at least one polymerizable compound, the polymerization of which begins before step b).

2. The method of claim 1, wherein, The compliance coating (50) has a constant thickness (X) comprised between 10 pm and 100 pm.

3. The method of claim 1 or 2, wherein, The visual appearance is a color or comprises a repetition of the same surface pattern.

4. The method of claim 1 or 2, wherein, The compliance coating (50) is deposited in the mold (12) by spreading or spraying.

5. The method of claim 1 or 2, wherein, The compliance coating (50) is chosen from among a pigmented paint, a pigmented resin, a film of glue, a cloth or a combination of the above.

6. The method of claim 5, wherein, The cloth is made of glass fibers or carbon fibers.

7. The method of claim 1 or 2, wherein, The compliance coating (50) is deposited on the bottom of the mold (12).

8. The method of claim 1 or 2, wherein, The machining is performed by sandblasting.

9. The method of claim 1 or 2, wherein, The method comprises, before step a), a step i) of arranging wedges (52) in the mold (12), each having a thickness equal to the calibrated thickness, and serving to define, between them, a space for depositing the compliance coating (50), and comprises, between steps a) and b), a step ii) of removing the wedges from the mold.

10. The method of claim 9, wherein, The method comprises, between steps a) and b), a step iii) of at least partially polymerizing the compliance coating (50).

11. The method of claim 1 or 2, wherein, The method comprises, between steps a) and b), a step iv) of checking the thickness (X) of the compliance coating (50).

12. The method of claim 1 or 2, wherein, The part is a blade (16) or a casing (72).

13. The method of claim 1, wherein, The turbomachine is a turbomachine of an aircraft.

14. The method of claim 2, wherein, The constant thickness is comprised between 20 pm and 60 pm.

15. The method of claim 2, wherein, The constant thickness is 40 pm.

16. The method of claim 6, wherein, The cloth is woven; and / or, The cloth is impregnated with a polymerizable resin.

17. The method of claim 11, wherein, In step iv), the thickness (X) of the compliance coating (50) is checked by eddy currents.

18. A method for manufacturing a part made of composite material for a turbomachine, the method comprising the steps of: b) arranging a preform made of three-dimensional woven fibers in a mold, c) injecting a polymerizable resin into the mold to impregnate the preform, forming the part after curing, d) machining the part, e) visually inspecting the part by an operator to verify at least one compliance criterion, characterized in that, before step b), there is a step a) during which at least one compliance coating is deposited in the mold, the compliance coating having a calibrated thickness (X) and at least one visual appearance identifiable by an operator, the compliance coating being intended to cover at least one zone of the preform at the end of step c) and to be fixed to the at least one zone by the polymerizable resin, and step e) comprises verifying by the operator the presence of the visual appearance in the at least one zone to verify the compliance criterion, the method comprising, before step a), a step i) of arranging wedges in the mold, the wedges each having a thickness equal to the calibrated thickness, and the wedges being intended to define, between the wedges, a space for depositing the compliance coating, and the method comprising, between step a) and step b), a step ii) of removing the wedges from the mold.

19. The method of claim 18, wherein, the method comprising, between step a) and step b), a step iii) of at least partially polymerizing the compliance coating.

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