Method for manufacturing fan blade made of fiber-reinforced composite material

Abstract

Provided is a method that makes it possible to manufacture a fan blade made of a fiber-reinforced composite material having a complicated three-dimensional shape while ensuring the necessary tensile strength is provided without producing defects.　In this manufacturing method: a fan blade is regarded as a laminated article, and a laminated article is formed by performing repetitions of a step in which the layers constituting the laminated article are approximated as an article in which a plurality of strips that assume the form of a developable surface and that have a constant width over their entire longitudinal-direction length are arranged in a direction transverse to the longitudinal direction, a strip-form UD prepreg composed of a fiber-reinforced composite material is molded into a planar shape obtained by developing each of the developable surfaces, and the individual layers are formed by laminating the strip-form UD prepreg on a die. Having been so formed, the laminated article is molded.

Description

Manufacturing method for fiber-reinforced composite fan blades

[0001] The present disclosure relates to a method for manufacturing fiber-reinforced composite fan blades for turbofan engines.

[0002] A turbofan engine, which is a propulsion system for aircraft, is composed of a fan and a core engine that is arranged coaxially behind the fan and has a turbine for driving the fan.

[0003] The fan includes a generally cylindrical fan case, a generally cylindrical fan disk configured to rotate within the fan case, and a plurality of fan blades attached to the outer periphery of the fan disk, and is driven to rotate by a turbine connected via a shaft.

[0004] During operation of a turbofan engine, the fan blades rotate together with the fan disk, drawing air into the fan. Some of the pressurized air flows into the core engine, generating high-temperature, high-pressure gas to drive the turbine, while the remainder bypasses the core engine and is exhausted from the rear, contributing to the generation of most of the thrust.

[0005] To reduce weight, fan blades for turbofan engines are often manufactured from fiber-reinforced composite materials, such as carbon fiber reinforced plastic (CFRP). During operation of a turbofan engine, centrifugal force acts on the fan blades in the span direction (from the hub to the tip of the blade). Therefore, in fan blades made of fiber-reinforced composite materials, the reinforcing fibers are oriented mostly in the span direction to increase tensile strength against centrifugal force. However, to provide resistance to localized impacts such as bird strikes, fan blades are often manufactured by combining multiple reinforcing fibers oriented in a direction other than the span direction.

[0006] As mentioned above, fiber-reinforced composite fan blades are typically manufactured by laminating unidirectional (UD) prepregs. UD prepregs are made of reinforcing fibers oriented in one direction and impregnated with a matrix resin. Fiber-reinforced composite fan blades can be manufactured by preparing UD prepregs of an appropriate shape and laminating them on a mold.

[0007] The fan blades of modern turbofan engines are constructed to have complex three-dimensional shapes in order to improve aerodynamic performance and reduce noise. Conventional methods for manufacturing such fan blades using UD prepreg, a fiber-reinforced composite material, include the following.

[0008] The first method involves approximating the three-dimensional shape of the fan blade to a polyhedron, then stacking UD prepregs cut to the shape of each face of the polyhedron on a mold and molding the blade. However, the polyhedron typically has a region where multiple faces are aligned in the span direction of the fan blade. Therefore, fan blades manufactured using this method include regions where multiple UD prepregs are aligned in the span direction. In these regions, the reinforcing fibers are not continuous throughout the span direction, which creates the problem of not being able to achieve the required tensile strength. Another problem is that manufacturing costs increase because a large number of UD prepregs, each with a different shape, must be prepared and managed in relation to their stacking positions on the mold.

[0009] The second method involves regarding the three-dimensional shape of a fan blade as a laminate, approximating each layer of the laminate as a collection of developable surfaces, and stacking UD prepregs cut to the shape of each developable surface on a mold to form the blade. Here, a developable surface refers to a curved surface that can be developed into a flat surface without stretching. Unlike the first method, this method requires only one UD prepreg per layer, thereby avoiding the problem of increased manufacturing costs. However, the UD prepreg typically has multiple cuts. Therefore, the reinforcing fibers are cut at the cuts, and the reinforcing fibers are oriented in different directions in each section separated by the cuts. Therefore, in fan blades manufactured using this method, the reinforcing fibers are cut at the cuts in the UD prepreg, resulting in a discontinuous change in their orientation, making it difficult to obtain the required tensile strength.

[0010] The third method involves stacking tape-shaped UD prepregs (UD prepreg tapes) on a mold using the AFP (Automated Fiber Placement) method so that each layer extends in a predetermined direction, and then molding the resulting product. This method allows for gaps to form between two adjacent UD prepreg tapes during stacking, but stacks the UD prepreg tapes with as little steering (in-plane bending) as possible to prevent overlaps between the two UD prepreg tapes. The resulting gaps are then filled by stacking additional UD prepreg tapes cut to fit the shape of the tape. However, even when gaps are filled with additionally stacked UD prepreg tapes, it is difficult to completely eliminate gaps and / or overlaps between the UD prepreg tapes. If these remain, defects such as voids may occur after molding. Furthermore, the reinforcing fibers contained in the UD prepreg tapes stacked to fill the gaps are often short, which is undesirable from the perspective of ensuring the required tensile strength.

[0011] The fourth method, similar to the third method, involves stacking UD prepreg tapes on a mold using the AFP method so that each layer extends in a predetermined direction, and then molding. However, in this method, the UD prepreg tapes are stacked while steering as necessary to prevent gaps or overlaps between adjacent UD prepreg tapes during stacking. However, bending a UD prepreg tape in the in-plane direction causes in-plane or out-of-plane undulations of the reinforcing fibers, resulting in defects after molding due to the undulations. Using a narrow (i.e., thin) UD prepreg tape can reduce the difference in circumferential length between the inner and outer peripheries of the steering portion and minimize undulations of the reinforcing fibers, but this increases the number of UD prepreg tapes required, and there is a possibility of defects due to the undulations, although these are negligible in practice.

[0012] As described above, it has been difficult using conventional methods to manufacture fan blades made of fiber-reinforced composite material having complex three-dimensional shapes without defects while ensuring the necessary tensile strength.

[0013] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a method for manufacturing fan blades made of fiber-reinforced composite material having complex three-dimensional shapes without generating defects while ensuring the necessary tensile strength.

[0014] To solve the above problems, in the method of manufacturing a fan blade made of fiber-reinforced composite material disclosed herein, the fan blade is regarded as a laminate, and each layer constituting the laminate is approximated as a plurality of strips in the shape of developable surfaces, each of which has a constant width over its entire longitudinal length, arranged in a direction transverse to the longitudinal direction. UD prepreg strips made of the fiber-reinforced composite material are molded into a planar shape obtained by unfolding each of the developable surfaces, and the laminate is formed by repeating the process of forming each of the layers by stacking the UD prepreg strips on a mold, and the formed laminate is then molded.

[0015] According to the present disclosure, it is possible to manufacture a fan blade made of a fiber-reinforced composite material having a complex three-dimensional shape without defects while ensuring the necessary tensile strength.

[0016] 1A is a schematic explanatory diagram showing a state in which the three-dimensional shape of a fan blade is considered to be a laminate, and each layer constituting the laminate is approximated as a plurality of strips in the form of a developable surface, each having a constant width over the entire longitudinal length, arranged in a direction transverse to the span direction. 1B is a schematic explanatory diagram showing the shape of a curved UD prepreg tape obtained by developing onto a plane the developable surface shapes of the plurality of strips of FIG. 1A, a UD prepreg tape having reinforcing fibers oriented in the longitudinal direction. 1C is a schematic explanatory diagram showing a state in which the curved UD prepreg tape of FIG. 1B is laminated on a mold. 1D is a schematic explanatory diagram showing a state in which an additional curved UD prepreg tape is laminated on a layer already formed on a mold when the matrix resin of the fiber reinforced composite material constituting the curved UD prepreg tape is thermosetting. 1E is a schematic explanatory diagram showing a state in which an additional curved UD prepreg tape is laminated on a layer already formed on a mold when the matrix resin of the fiber reinforced composite material constituting the curved UD prepreg tape is thermoplastic.

[0017] Hereinafter, an embodiment of the manufacturing method of the present disclosure will be described in detail with reference to the drawings.

[0018] The manufacturing method disclosed herein regards the fan blade as a laminate, and approximates each layer that makes up the laminate as a plurality of strips in the shape of developable surfaces, each with a constant width over the entire longitudinal length, arranged in a direction transverse to the longitudinal direction. Strip-shaped UD prepregs made of fiber-reinforced composite material are molded into the planar shape obtained by unfolding each of the developable surfaces, and the process of forming each layer by stacking the strip-shaped UD prepregs on a mold is repeated to form a laminate, and finally the laminate is molded.

[0019] The fiber-reinforced composite material constituting the UD prepreg can contain, for example, carbon fibers as reinforcing fibers, and either thermosetting or thermoplastic matrix resins can be used to impregnate the reinforcing fibers. The reinforcing fibers are oriented in one direction within the UD prepreg.

[0020] 1A and 1B are schematic explanatory views showing steps in the above-mentioned manufacturing method up to obtaining curved UD prepreg tapes to be laminated.

[0021] In this step, the three-dimensional shape of the fan blade is first considered to be a laminate, and each layer constituting the laminate is then approximated by a computer (e.g., using 3D CAD software) as an arrangement of multiple strips B each having a developable surface shape with a constant width over the entire longitudinal length, as shown in Figure 1A. Note that a developable surface is a curved surface that can be developed into a flat surface without expanding or contracting. The width of each strip B is selected so that the approximation error described above falls within an acceptable range.

[0022] Next, a computer is used to determine the shape of a plane obtained by developing the developable surface shapes of each of the above-mentioned multiple strips B. Then, a UD prepreg tape having the same width as each of the above-mentioned multiple strips B and with reinforcing fibers oriented in the longitudinal direction is molded into the obtained shape of the plane, for example, by using an AFP method involving steering (in-plane bending).

[0023] In this way, a plurality of curved UD prepreg tapes CT are obtained, each of which is planar and has a curved portion in a direction transverse to its longitudinal direction (see FIG. 1B).

[0024] Next, the step of laminating a plurality of curved UD prepreg tapes obtained in FIGS. 1A and 1B on a mold will be described below with reference to FIGS. 2A to 2C.

[0025] 2A to 2C are schematic explanatory views showing the steps of the above-mentioned manufacturing method in which a plurality of curved UD prepreg tapes are stacked on a mold.

[0026] FIG. 2A shows a state in which one of the curved UD prepreg tapes CT is being laminated onto the mold M to form a first layer L1 of UD prepreg on the mold M.

[0027] Whether the matrix resin of the fiber-reinforced composite material that constitutes the UD prepreg is thermosetting or thermoplastic, simply placing the curved UD prepreg tape CT on a mold M (usually made of metal or composite material) will not allow the curved UD prepreg tape CT to be fixed to the mold M. Therefore, the curved UD prepreg tape CT that forms the first layer L1 of the UD prepreg is layered on the mold M using a vacuum suction method.

[0028] In this way, the curved UD prepreg tapes CT are sequentially stacked on the mold M in a direction transverse to the longitudinal direction thereof, and finally, the first layer L1 of the UD prepreg is formed.

[0029] FIG. 2B shows a curved UD prepreg tape CT to form a second layer of the UD prepreg when the matrix resin of the fiber reinforced composite material constituting the UD prepreg is thermosetting. Ｓ 1 shows a state in which one of the layers is laminated on the first layer L1 of the UD prepreg.

[0030] Since the thermosetting resin has tackiness (stickiness) even at room temperature, the curved UD prepreg tape CT is applied to the surface of the first layer L1 of the UD prepreg. Ｓ To do this, for example, as shown in the figure, a curved UD prepreg tape CT Ｓ A roller R that rolls on the roller along the longitudinal direction can be used.

[0031] FIG. 2C shows a curved UD prepreg tape CT to form a second layer of UD prepreg on a mold M when the matrix resin of the fiber reinforced composite material constituting the UD prepreg is thermoplastic. Ｐ 1 shows a state in which one of the layers is laminated on the first layer L1 of the UD prepreg.

[0032] Since the thermoplastic resin does not have tackiness at room temperature, as shown in the figure, the curved UD prepreg tape CT placed on the first layer L1 of the UD prepreg Ｐ By pinpoint heating using, for example, a heater H at multiple locations along the longitudinal direction of the UD prepreg (the locations indicated by black dots in the figure), the two upper and lower layers of UD prepreg can be spot-welded and fixed together.

[0033] By the method described with reference to FIGS. 2B and 2C, a curved UD prepreg tape (CT Ｓ or CT Ｐ ) are sequentially stacked on the first layer L1 of the UD prepreg in a direction transverse to the longitudinal direction thereof, to finally form the second layer of the UD prepreg.

[0034] Further, in the same manner, third and subsequent layers of curved UD prepreg tape are laminated until the UD prepreg laminate takes on the desired shape (i.e., the shape of a fan blade). The UD prepreg laminate in the desired shape is then molded under high temperature and pressure, for example, using an autoclave, to complete the fan blade.

[0035] In the UD prepreg laminate, which is an intermediate product when manufacturing a fan blade using the method described above, the curved UD prepreg tapes that make up each layer are arranged without gaps or overlaps in the direction transverse to the longitudinal direction, so the fan blade obtained by molding the laminate is free of defects.

[0036] Furthermore, in the above laminate, the curved UD prepreg tapes constituting each layer contain reinforcing fibers oriented in the longitudinal direction, and the reinforcing fibers are continuous throughout the entire length. As a result, the fan blade obtained by molding the laminate has the necessary strength to withstand localized impacts such as centrifugal force and bird strikes.

[0037] (Aspects of the present disclosure) In a method for manufacturing a fan blade made of fiber-reinforced composite material according to a first aspect of the present disclosure, the fan blade is regarded as a laminate, and each layer constituting the laminate is approximated as a plurality of strips in the shape of developable surfaces, each having a constant width over the entire longitudinal length, arranged in a direction transverse to the longitudinal direction. The laminate is formed by repeating the steps of molding strip-shaped UD prepregs made of the fiber-reinforced composite material into a planar shape obtained by unfolding each of the developable surfaces, and stacking the strip-shaped UD prepregs on a mold to form each of the layers, and then molding the formed laminate.

[0038] In the method for manufacturing a fan blade made of fiber-reinforced composite material according to the second aspect of the present disclosure, a vacuum suction method is used to initially laminate the strip-shaped UD prepreg onto the mold.

[0039] In the method for manufacturing a fan blade made of fiber-reinforced composite material according to the third aspect of the present disclosure, the resin contained in the fiber-reinforced composite material is thermosetting, and when the strip-shaped UD prepreg is laminated on top of an already formed layer on the mold to form the next layer, the strip-shaped UD prepreg is fixed by being pressed against the already formed layer.

[0040] In the method for manufacturing a fan blade made of fiber-reinforced composite material according to the fourth aspect of the present disclosure, the resin contained in the fiber-reinforced composite material is thermoplastic, and when the strip-shaped UD prepreg is laminated on top of an already formed layer on the mold to form the next layer, the strip-shaped UD prepreg and the already formed layer are fixed to each other by spot welding.

[0041] B Strip C Chord direction CT Curved UD prepreg tape CT Ｐ　 Curved UD prepreg tape (matrix resin: thermoplastic) CT Ｓ　 Curved UD prepreg tape (matrix resin: thermosetting) H Heater L1 First layer of UD prepreg M Mold R Roller S Span direction

Claims

1. A method for manufacturing a fan blade made of fiber-reinforced composite material, comprising the steps of: regarding the fan blade as a laminate; approximating each layer of the laminate as a plurality of strips in the shape of developable surfaces, each of which has a constant width over its entire longitudinal length, arranged in a direction transverse to the longitudinal direction; molding strip-shaped UD prepreg made of the fiber-reinforced composite material into a planar shape obtained by unfolding each of the developable surfaces; forming the laminate by repeating the process of forming each of the layers by stacking the strip-shaped UD prepreg on a mold; and molding the formed laminate.

2. The method according to claim 1, wherein a vacuum suction method is applied to initially stack the strip of UD prepreg on the mold.

3. The method according to claim 2, wherein the resin contained in the fiber-reinforced composite material is thermosetting, and when the strip-shaped UD prepreg is laminated on an already formed layer on the mold to form the next layer, the strip-shaped UD prepreg is fixed by being pressed against the already formed layer.

4. The method according to claim 2, wherein the resin contained in the fiber-reinforced composite material is thermoplastic, and when the strip-shaped UD prepreg is laminated on an already formed layer on the mold to form the next layer, the strip-shaped UD prepreg and the already formed layer are fixed to each other by spot welding.

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