PROCESS FOR MANUFACTURING A COMPOSITE BLADE FOR AN AIRCRAFT ENGINE

Abstract

A process for manufacturing a blade made of composite material for a turbomachine is provided. The blade includes an airfoil having a pressure side and a suction side which extend from a leading edge to a trailing edge of the airfoil. The blade further includes a metal sheath that extends along the leading edge of the airfoil. The process includes the steps of: a) placing a preform, made by three-dimensionally weaving fibers, in a mold, a polymerizable adhesive being inserted between the sheath and the edge of the preform; and b) injecting polymerizable resin into the mold to impregnate the preform so as to form the airfoil after solidifying, wherein the resin is injected within a time interval during which the adhesive reaches a freezing point.

Claims

1. A method for manufacturing a blade made of composite material for a turbomachine, said blade comprising a vane having a pressure side and a suction side which extend from a leading edge to a trailing edge of the vane, the blade further comprising a metal shield extending along the leading edge of the vane, the method comprising the steps of: a) disposing a preform made by three-dimensionally weaving fibers in a mould, the shield being positioned on an edge of the preform to form the leading edge of the vane, and a polymerizable adhesive being interposed between the shield and the edge of the preform, b) injecting polymerizable resin into the mould to impregnate the preform to form the vane after solidification, wherein the resin is injected within a time interval during which said adhesive reaches a gel point.

2. The method according to claim 1, wherein the adhesive is in the form of an adhesive film.

3. The method of claim 1, wherein the resin is injected within a time interval in the middle of which said adhesive reaches the gel point.

4. The method according to claim 2, wherein the time interval starts at least 5 minutes before the adhesive reaches the gel point, and ends at least 5 minutes after the adhesive reaches the gel point.

5. The method of claim 1, wherein the resin begins to be injected when the adhesive reaches the gel point.

6. The method according to claim 1, wherein the temperature of the mould is regulated so that it is kept constant during the time interval.

7. The method of claim 1, wherein the temperature of the mould is maintained at a temperature of at least 160° C. during the time interval.

8. The method of claim 1, wherein the resin is an epoxy resin.

9. The method of claim 1, wherein the adhesive is an epoxy adhesive.

10. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0035] Further features and advantages of the invention will become apparent from the detailed description that follows, for the understanding of which reference is made to the appended drawings in which:

[0036] FIG. 1 is a schematic perspective view of a composite aircraft turbomachine blade,

[0037] FIG. 2 is a block diagram showing the steps of a method according to the invention for manufacturing a blade such as that shown in FIG. 1,

[0038] FIG. 3 is a schematic perspective view of a mould in which a preform and a shield are intended to be arranged, and in which a resin is intended to be injected, and

[0039] FIG. 4 is a graph representing both the evolution of the viscosity of the resin and of an adhesive as a function of time, as well as the evolution of the temperature as a function of time, during the manufacturing method.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Reference is first made to FIG. 1, which illustrates a composite material blade 10 for a turbomachine, said blade 10 being, for example, a fan blade.

[0041] The blade 10 comprises a vane 12 connected by a support 14 to a root 16 which has, for example, a dovetail shape and is shaped to be engaged in a complementarily shaped recess of a rotor disk, in order to retain the blade on this disk.

[0042] The vane 12 includes a leading edge 12a and a trailing edge 12b for gases flowing into the turbomachine. The vane 12 has a curved or even twisted aerodynamic profile and comprises a pressure side 18 and a suction side 20 extending between the leading edge 12a and trailing edge 12b.

[0043] The vane 12 is made from a fibrous preform obtained by three-dimensional weaving of fibers, for example carbon.

[0044] The leading edge 12a of the vane is reinforced and protected by a metal shield 22 that is attached to this leading edge 12a. The shield 22 is, for example, made of a nickel and cobalt based alloy.

[0045] In the present invention, this attachment is achieved on the one hand by co-moulding the preform with the shield 22, and on the other hand by bonding the shield 22 by means of at least one adhesive 24, preferably in film form.

[0046] FIG. 2 is a flowchart illustrating steps in a method for manufacturing a composite blade 10 such as that shown in FIG. 1.

[0047] The method may include several steps, some of which are optional.

[0048] The first step a) of the method includes several sub-steps or operations. In a first operation a1) discussed above, a fibrous preform is made by weaving fibers. The resulting preform is raw and can undergo operations such as cutting or compression, for example.

[0049] In a further operation a2) of the method, one or more adhesive films 24 are prepared. This adhesive film 24 is intended to be interposed between the shield 22 and the preform, before injection of the resin into a mould 30 for manufacturing the blade, which is shown in FIG. 3.

[0050] This adhesive film 24 is, for example, a double-sided film, i.e., a film that is sticky on both sides. This film is thus coated or soaked on both sides with a glue, for example of the epoxy type. This is, for example, the adhesive marketed by the Solvay company under the reference FM® 309-1.

[0051] This adhesive film 24 has, for example, a thickness of between 0.1 mm and 0.2 mm. This film 24 can be in the form of a strip. It can thus have an elongated shape whose dimensions are a function of those of the shield 22.

[0052] The shield 22 is generally dihedral in shape and defines a V-shaped groove into which an edge of the preform is inserted.

[0053] The adhesive film 24 is preferably adhered to the shield 22 within the groove.

[0054] Another operation (a3)) of the method then consists in positioning the preform equipped with the film 24 and the shield 22 in the mould 30 (FIG. 3), which is then closed, for example, with a counter-mould.

[0055] The successive operations a1) to a3) represent a first step a) of the manufacturing method.

[0056] In a second step b) of the method, the resin is injected into the mould 30 and is intended to impregnate the preform and to come into contact with the film 24 and the shield 22. After polymerization and curing of the resin, the shield 22 is attached to the vane by means of the adhesive film 24 and the resin.

[0057] The blade 10 thus obtained, after polymerization of the resin, is advantageous in that its shield 22 is perfectly positioned and maintained on the vane 12.

[0058] FIG. 4 illustrates a feature of the invention relating to the time of injection of the resin into the mould.

[0059] FIG. 4 is a graph comprising three curves C1, C2 and C3.

[0060] The curve C1 represents the evolution of the viscosity of the resin over time. Curve C2 represents the evolution of the viscosity of the adhesive over time and curve C3 represents the evolution of the temperature of the mould 30 over time.

[0061] In practice, the curve C1 depends on the resin used. The resin is injected at a time T0 and undergoes a decrease in viscosity. The viscosity of the resin then increases due to polymerization and reaches a gel point G1 at T1. The resin is injected, for example, at a pressure of between 5 and 15 bars, and for a period of about 120 minutes.

[0062] The temperature of the mould 30 (curve C3) is regulated as a function of the resin so as to optimize its polymerization. The temperature increases progressively from a time T2 until it reaches a threshold at T3 at a temperature, here greater than or equal to 160° C., which corresponds to the polymerization temperature of the resin. This threshold is maintained until T4 and then the temperature is increased from T4 to T5 until a new threshold at a temperature greater than or equal to 180° C.

[0063] T3 occurs earlier than T0, i.e., the threshold at 160° C. is reached before the resin is injected into the mould. Furthermore, T4 and T5 occur before T1. The gel point G1 of the resin therefore occurs during the second temperature threshold.

[0064] The curve C2 depends on the adhesive used. The viscosity of the adhesive decreases from T2, i.e., from the beginning of the heating of the mould. The viscosity then increases from T6 onwards and continues to rise through a gel point G2 at T7. T7 is between T3 and T4. The vitrification V1 of the adhesive is reached at T8. T8 is here later than T5 and earlier than T1.

[0065] According to the invention, the resin is injected into the mould within a time interval ΔT around the gel point G2 of the adhesive. This time interval ΔT is represented in FIG. 4 by a rectangle delimited by a double line. It is thus understood that the resin is advantageously injected into the mould during this time lapse during which the viscosity of the adhesive is not too high. This ensures optimum co-bonding between the adhesive and the resin.

[0066] In the example shown, the times T0 and T7 coincide, i.e., the resin injection takes place or begins at the gel point G2 of the adhesive.