Injection bonding of composite blades into the cavity

Abstract

A method for bonding a composite blade (1) to at least one support (2). The method comprises the following steps: positioning one end of the blade (1) within the support (2); causing adhesive to flow between the blade and the support from an inlet (3) to an outlet (4); and causing adhesive to flow in the opposite direction from the outlet (4) toward the inlet (3).

Description

Technical Field

[0001] The present invention particularly, but not exclusively, relates to a method of injection bonding a composite blade to a pocket or cavity of a support, the composite blade and support being used in a gas turbine engine. It will be appreciated from the disclosure herein that the present invention is also applicable to injection bonding in various applications other than gas turbine engines.

[0002] The invention also relates to a device for carrying out the method. Background Art

[0003] The current method of attaching blades to supports involves applying or coating the blade with adhesive before placing it into the support's cavity. Once the blade is placed into the holder, the adhesive is cured to secure it in place. This method is simple and economical, and can be performed without the need for expensive equipment or training.

[0004] While existing manufacturing techniques offer the advantages described above, the inventors have determined that defects may exist in components formed in this manner. Specifically, large voids may be created in the bond wires, which are problematic because they reduce the structural integrity of the joint and may lead to failure.

[0005] Alternative technologies for forming such components include injection molding, which requires complex and expensive manufacturing equipment. However, traditional injection molding techniques can still result in voids and discontinuities within the structure. This is often due to the formation of air pockets within the adhesive flow front. Furthermore, the complex geometry and positioning of the adhesive inlet and outlet can sometimes make the area or volume surrounding the inlet and outlet difficult to fill with adhesive. Air or gas can also be present in the adhesive during injection, further contributing to the formation of air pockets.

[0006] Furthermore, the adhesive injected into the joint takes the path of least resistance through the cavity. Consequently, the adhesive is often unevenly distributed within the cavity between the blade and the support. For example, the adhesive may migrate to the side of the blade closest to the injection point, resulting in uneven amounts of adhesive on both sides of the blade. Consequently, the blade is secured unevenly on both sides. This leads to uneven stress distribution within the blade. Consequently, the structural integrity of the joint remains suboptimal when using standard injection bonding methods.

[0007] The present inventors have devised an improved method for forming joined parts. Specifically, the inventors have devised a method that provides improvements to basic joining techniques and additionally overcomes the shortcomings of conventional injection-bonding at the connection point between the blade and the support. This method is a non-traditional approach to achieving a hermetic seal between the blade and the support.

[0008] It will be appreciated from the disclosure herein that the present invention is also applicable to other applications where it is desirable to join two components using injection bonding where it is desired to have no voids in the bond line. Summary of the Invention

[0009] Aspects of the invention are defined in the accompanying claims.

[0010] According to a first aspect, a method of bonding a composite blade to at least one support member is provided, the method comprising the steps of: (a) positioning one end of the blade within the support member; (b) flowing an adhesive between the blade and the support member from an inlet toward an outlet; and (c) flowing the adhesive in the opposite direction from the outlet toward the inlet.

[0011] In this way, a hermetic seal is achieved between the blade and the support. This is important in gas turbine engines, such as aircraft engines, where tight tolerances are required between parts. Voids often form in the adhesive due to air pockets forming in the flow front or due to the complex geometry of the gap between the blade and the support. Therefore, the reverse flow can fill any voids in the adhesive.

[0012] The term "support" is used to refer to a part that can be located at the inner diameter or outer diameter of a gas turbine engine bypass passage. The support has an interior space that is capable of receiving one end of a blade and securing the blade in place.

[0013] There may be a gap between the blade and the support, the gap defining a space for receiving the adhesive. The space enables the adhesive to flow on both sides of the blade within the support, thereby enabling the blade to be securely positioned in the support.

[0014] The term "space" is intended to refer to the space formed around the portion of the blade received by the support.

[0015] The temperature of the space can be increased before the adhesive is injected. This reduces the viscosity of the adhesive, thereby improving the flow of the adhesive through the space.

[0016] A pressure differential can be created between the inlet and the outlet to cause the adhesive to flow into and through the space. The pressure differential aids in the movement of the viscous adhesive through the space.

[0017] The pressure at the inlet can be increased to a suitable pressure. For example, the pressure can be increased to about 2 bar. The inventors have determined that this pressure optimizes the flow of adhesive through the space.

[0018] Before releasing or injecting the adhesive into the inlet, the pressure at the outlet can be reduced. This allows the adhesive to be drawn through the space, thereby aiding the flow of the viscous adhesive.

[0019] Before the adhesive is released or injected into the inlet, the pressure at the outlet may be reduced to below atmospheric pressure. The vacuum formed by this pressure reduction causes the adhesive to be drawn through the space.

[0020] The amount of adhesive can be monitored at the outlet. The adhesive can be allowed to flow between the blade and the support until a predetermined amount of adhesive has left the outlet. This ensures that the amount of adhesive required to fill the space has been injected through the inlet.

[0021] In one example, the predetermined amount of adhesive may be approximately 1.3e -6 m 3 and about 2.5e -6 m 3 between.

[0022] When a predetermined amount of adhesive has left the outlet and before adhesive reverses flow, the valve at the inlet may be closed.

[0023] This prevents resin from filling the space between the blades and the adhesive from flowing back into the inlet during reverse flow. Consequently, the reverse flow of adhesive compresses any air pockets that form between the blades and the support. This allows any complex geometry between the blades and the support to be reliably filled with adhesive.

[0024] Advantageously, the flow can be reversed from the outlet towards the inlet by increasing the pressure at the outlet. This enables adhesive that has left the space through the outlet to flow back into the space and fill any remaining voids.

[0025] After the reverse flow, the pressure at the inlet and outlet can be maintained at approximately the same pressure. This can prevent the adhesive that flowed into the space during the initial injection from flowing back through the inlet.

[0026] After the flow is reversed, the pressure at the inlet and outlet can advantageously be maintained at a pressure for a predetermined period of time. For example, the pressure can be maintained at a pressure between about 1 bar and 3 bar.

[0027] The adhesive flow can be caused to fluctuate between a first direction from the inlet to the outlet and a second direction from the outlet to the inlet. Utilizing this fluctuation in flow, it can be ensured that the adhesive completely fills the space and that no voids are left in the space.

[0028] The method may further include positioning an opposite end of the vane in a second support; flowing the adhesive between the vane and the support from the inlet toward the outlet; and flowing the adhesive in the opposite direction from the outlet toward the inlet.

[0029] Viewed from another aspect, an apparatus for performing the above method is provided, comprising: at least one support member including an inlet, an outlet, and a cavity; a blade positioned in the cavity; and a seal surrounding one end of the support member, wherein the seal is configured to prevent adhesive from exiting the end of the cavity and to form the adhesive into a rounded shape.

[0030] The term "cavity" is used to refer to a recess in a support that receives a blade.

[0031] The rounded shape of the seal improves the aerodynamics of the joint. Improved aerodynamics is important when this method is used to join blades and supports for gas turbine engines.

[0032] The apparatus may further comprise a fixture attached to the support.The fixture may comprise an inlet aperture and an outlet aperture for aligning with the inlet and outlet of the support.

[0033] The apparatus may further comprise a foam seal between the fixing member and the support member. The foam seal may comprise an inlet hole and an outlet hole for aligning with the inlet hole and the outlet hole of the fixing member and the inlet and outlet of the support member.

[0034] The at least one support may be made of any suitable material, such as titanium or another suitable alloy.

[0035] Viewed from another aspect, a method for joining two parts using injection bonding is provided, the method comprising injecting an adhesive into a cavity through an inlet until a predetermined amount of the adhesive flows through an outlet, and then reversing the flow of the adhesive such that at least a portion of the predetermined amount of adhesive flows back into the cavity.

[0036] Viewed from another aspect, there is provided an aerospace engine component manufactured by a method as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present teachings will now be described, by way of example only, with reference to the following drawings, in which like parts are indicated by like reference numerals:

[0038] Figure 1 shows a cross section of a gas turbine engine incorporating an air flow arrangement according to the invention described herein;

[0039] Figure 2 shows an isometric view of a blade secured to a support and attached to a fixture according to the invention;

[0040] Figure 3 Shown Figure 2 A cross-sectional view of the device in the XX direction;

[0041] Figure 4 Shown Figure 2 A cross-sectional view of the device in the YY direction; and

[0042] Figure 5 The blade is shown fixed to the support member after being removed from the fixing member.

[0043] While the present teachings are susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and described in detail herein. However, it should be understood that the drawings and detailed description are not intended to limit the scope to the particular forms disclosed, but rather, the scope is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.

[0044] The words "include", "comprising" and similar words used in this specification should not be interpreted in an exclusive or exhaustive sense. In other words, they mean "including but not limited to".

[0045] It will be appreciated that features of aspects of the invention described herein may be used conveniently and interchangeably in any appropriate combination. DETAILED DESCRIPTION

[0046] The present teachings relate to a method of bonding a composite blade to a support and an apparatus for performing the method.The composite blade may be used in a gas turbine engine, for example, in an aircraft.

[0047] Figure 1 There is shown a cross section of a gas turbine engine 21 which may incorporate blades according to the present invention, as described in detail below.

[0048] Those skilled in the art will understand the main components of a gas turbine engine and its operation. In general, the engine 21 includes an air intake 22 that allows air to flow into the engine to a fan 23 located at the upstream end of the engine. All components are housed in an engine nacelle 24.

[0049] The engine includes a bypass duct 20 downstream of the fan and a central engine core containing the compressor, combustor, and turbine. The engine's core is formed by a first low-pressure compressor (LPC) 25 and a second high-pressure compressor (HPC) 26. This multi-stage compressor arrangement brings air from ambient pressure and temperature to high temperature and pressure. The compressed air is then passed to a combustion chamber 27, where fuel is injected and combustion occurs.

[0050] The combustion gases exit the rear of the combustion chamber 27 and strike first a high-pressure turbine 29, then a second low-pressure turbine 30, before exiting the rear of the engine through a core nozzle 31. Thrust from the engine is generated by two airflows: the first from the fan nozzle 28 (which receives thrust from the fan), and the second from the exhaust of the core nozzle 31.

[0051] The blade 1 according to the invention may advantageously be formed from a composite material, for example carbon fibres in an epoxy resin matrix.The term composite material is intended to refer to carbon (or other) reinforced plastics.

[0052] The support is configured to connect the blade to the core of the engine and to the inner surface of a bypass passage 20 through which the blade extends. The support is connected to the blade at both ends.

[0053] Figure 2 An isometric view of an apparatus according to the present invention for bonding a composite blade 1 to a support 2 is shown. In this example, the support 2 is made of titanium. In other examples, the support 2 can be made of an aluminum alloy with galvanic protection, a short fiber composite material, or a different material. The support 2 has a cavity for receiving the blade.

[0054] The support 2 may have a base plate 6. When the composite blade and support are in use, the base plate 6 of the support 2 is configured to be attached to an aircraft engine. When the blade 1 is bonded to the support 2, the base plate 6 is attached to a fixture 9 via a seal 5 (e.g., elastomer or foam). The fixture 9 is adapted to conform to the outer surface of the base plate. The seal 5 is located between the fixture and the base plate.

[0055] Each of the fixing member 9 and the foam sealing member 5 is formed with two holes, an inlet hole and an outlet hole (not shown). In the example shown, a single inlet and a single outlet are used. Multiple inlets and multiple outlets can also be used.

[0056] The inlet tube 3 is held in place by an inlet connector 7, allowing fluid communication of adhesive through the connector as described below. The inlet tube 3 is connected to a source of adhesive.

[0057] The outlet pipe 4 is held in place by an outlet connection 8. The inlet connection 7 and the outlet connection 8 are connected to a fixing 9.

[0058] The foam seal 5 is replaced after each use, whereas the fixing 9, the inlet pipe 3, the outlet pipe 4, the inlet connection piece 7 and the outlet connection piece 8 can be reused for another blade.

[0059] The inlet tube 3 is connected to a source of adhesive. In this example, the inlet tube 3 is also connected to a pressure control device, and the outlet tube 4 is connected to a vacuum pump. Each of the inlet and outlet tubes includes a valve for switching between the use of the pressure control device and the vacuum pump. The outlet tube 4 of the present invention has an indicator line 13 that indicates when the desired amount of adhesive has flowed into the outlet tube 4. The outlet tube 4 is transparent so that the user can see when the adhesive has reached the indicator line 13. In other examples, the outlet tube may not be transparent, and a sensor may be used to indicate when the desired amount of adhesive has reached the desired volume in the outlet tube 4. For example, a proximity sensor may be used.

[0060] Figure 2 The adhesive 10 is shown having been formed into a radiused shape 12 .

[0061] Figure 3 Shown Figure 2 The equipment along Figure 2 A cross-sectional view taken along the XX direction is shown. This view also shows a seal 11. When the blade 1 is inserted into the support before the adhesive is injected, the seal 11 is positioned to surround the blade 1. The seal 11 prevents adhesive leakage and, due to its curved shape, allows the adhesive to be formed into a rounded corner or radius 12. In this example, the seal is made of silicon and formed by casting. In other examples, the seal may be made of other materials.

[0062] The seal can be adjusted to form a desired radius or fillet shape between the support and the blade. This can be a continuous profile along the blade or can be adapted to have a varying profile along the interface between the blade and the support.

[0063] Figure 4 Shown Figure 2 The equipment along Figure 2 A cross-sectional view in the direction YY is shown. This shows the inlet and outlet holes in each of the foam seal 5 and the fixing member 9.

[0064] Methods of using the device will now be discussed.

[0065] One end of blade 1 is inserted into a cavity in support 2. The blade may have geometric features (not shown) formed on its surface to center the blade within the cavity. These geometric features may be elongated protrusions extending from the surface of the blade in the longitudinal direction of the blade. Geometric features may also be designed to position the blade off-center in the cavity.

[0066] The blade 1 and support 2 are assembled with the foam seal 5 and the fixing 9, and the inlet pipe 3 and the outlet pipe are inserted into the corresponding holes in the foam seal and the fixing 9. The inlet connector 7 and the outlet connector 8 are connected to the fixing 9.

[0067] The other end of the blade can also be inserted into the cavity of the separate support at the same time. Alternatively, the other end of the blade can be fixed to the separate support after the first end is connected to the support 2.

[0068] The seal 11 is positioned at one end of the cavity into which the blade has been inserted. In one example, the seal is held in place by a clamp located on a fixture. The clamp can be made of metal. Next, a vacuum test is used to check the tightness of the connection.

[0069] Once the system is confirmed to be airtight, the fixture and part are heated, causing the temperature of the cavity to increase. For example, the part may be heated to a temperature between 60°C and 80°C. In other examples, the part may be heated to a temperature outside this range, above room temperature. The temperature to which the part is heated depends on the adhesive being used.

[0070] In this example, the temperature of the fixture and part is increased using a convection oven. This reduces the viscosity of the adhesive as it enters the cavity, thereby optimizing flow. It is also possible to heat the adhesive to reduce its viscosity before flowing it into the cavity.

[0071] The adhesive is caused to flow into the cavity through the inlet tube 3. This is achieved by applying a vacuum at the outlet before increasing the pressure in the inlet tube 3. The pressure in the inlet tube can be set between 0.5 bar and 2.5 bar. In this example, the pressure in the inlet tube is set to 2 bar. In other examples, different pressures can be used. For example, the pressure can be set to 1 bar.

[0072] The adhesive fills the cavity between the blade 1 and the support 2 and leaves through the outlet pipe 4 due to the vacuum. The adhesive is allowed to flow until the desired amount of adhesive has left the cavity through the outlet pipe. This is indicated by the arrival of the indicator line 13 (e.g. Figure 2 In this example, the adhesive is allowed to flow into the cavity until 1.3e -6 m 3 has left the cavity. In other examples, the desired amount may be more or less than this. For example, the desired amount may be approximately 1.3e -6 m 3 and 2.5e -6 m 3 between.

[0073] When the desired amount has left the cavity into the outlet tube 4, the flow of adhesive stops and the connection to the adhesive source from the inlet tube 3 is closed. This is done by closing the valve in the inlet tube.

[0074] As the adhesive passes through the interface between the blade and the inner surface of the support, irregular surface tension and imperfections in the surface can cause pockets or voids to form in the adhesive. These are detrimental to the strength of the connection between the support and the blade, and are also detrimental to the structural strength and integrity of the joint.

[0075] In order to prevent this discontinuity, a reverse flow of the adhesive is then performed as described below.

[0076] The pressure in the outlet pipe 4 is increased by a pressure control device. In this example, the pressure at the outlet is increased from vacuum to 2 bar. In other examples, the pressure can be increased to values ​​higher or lower than this. The pressure at the inlet can also be maintained at 2 bar, or, if another pressure is used at the outlet, the pressure at the inlet is maintained at a pressure substantially equal to the other pressure at the outlet. Due to the increased pressure in the outlet pipe, the adhesive is subsequently forced back into the cavity. This fills any voids in the cavity between the blade and the support. The pressure is maintained at a constant value for a predetermined period of time. This predetermined period of time is determined based on factors such as the type of adhesive used and the size of the cavity.

[0077] In this example, the temperature is also maintained at a constant value.

[0078] Once this has been carried out, the device is cured. After curing, the foam seal 5 and the fixing member 9 are removed from the blade 1 and the support 2.

[0079] Figure 5 The blade 1 is shown attached to the support 2 after being removed from the foam seal 5 and the fixing 9 .

[0080] The various embodiments described herein are intended only to assist in understanding and teaching the claimed features. These embodiments are provided only as representative examples of embodiments and are not exhaustive and / or exclusive. It should be understood that the advantages, embodiments, examples, functions, features, structures and / or other aspects described herein should not be considered as limitations on the scope of the invention as defined by the claims or limitations on the equivalents of the claims, and that other embodiments may be utilized and may be modified without departing from the scope of the claimed invention. In addition to those specifically described herein, the various embodiments of the present invention may appropriately include, consist of, or be substantially composed of appropriate combinations of disclosed elements, components, features, parts, steps, equipment, etc. In addition, the present disclosure may include other inventions that are not currently claimed but may be claimed in the future.

Claims

1. A method of bonding a composite blade to at least one support member, the support member comprising an inlet, an outlet and a cavity, the method comprising the following steps: (a) positioning one end of the blade within the cavity of the support, wherein a seal surrounds the one end of the support, wherein the seal is configured to prevent adhesive from exiting the one end of the cavity and is configured to form the adhesive into a rounded shape; (b) flowing the adhesive between the blade and the support from the inlet to the outlet; as well as (c) causing the adhesive to flow in the reverse direction from the outlet toward the inlet.

2. The method according to claim 1, wherein A gap between the blade and the support defines a space for receiving the adhesive.

3. The method according to claim 2, wherein: The temperature of the space is increased before injecting the adhesive.

4. The method according to claim 2 or 3, wherein: A pressure differential is created between the inlet and the outlet to cause the adhesive to flow into and through the space.

5. The method according to claim 4, wherein The pressure at the inlet was increased to 2 bar.

6. The method according to any one of claims 1 to 3, wherein: Prior to injecting the adhesive into the inlet, the pressure at the outlet is reduced.

7. The method according to claim 6, wherein: Prior to injecting the adhesive into the inlet, the pressure at the outlet is reduced to below atmospheric pressure.

8. The method according to claim 1, wherein monitoring the amount of the adhesive at the outlet, and wherein the adhesive is caused to flow between the blade and the support until a predetermined amount of adhesive has exited the outlet.

9. The method according to claim 8, wherein The predetermined amount of adhesive is between 1.3e -6 m 3 and 2.5e -6 m 3 between.

10. The method according to claim 8, wherein When the predetermined amount of adhesive has left the outlet and before the adhesive flows in the reverse direction, the valve at the inlet is closed.

11. The method according to any one of claims 1 to 3, wherein: By increasing the pressure at the outlet, the adhesive is caused to flow in the reverse direction from the outlet toward the inlet.

12. The method according to any one of claims 1 to 3, wherein: After the adhesive flow is reversed, the pressure at the inlet and the outlet is maintained between 1 bar and 3 bar for a predetermined period of time.

13. The method of any one of claims 1 to 3, further comprising fluctuating the flow of the adhesive between a first direction from the inlet to the outlet and a second direction from the outlet to the inlet.

14. The method according to any one of claims 1 to 3, wherein: The method further comprises: positioning an opposite end of the blade opposite the one end of the blade within a second support; flowing adhesive between the blade and the second support from an inlet of the second support to an outlet of the second support; and The adhesive is caused to flow in the reverse direction from the outlet of the second support member toward the inlet of the second support member.

15. A method of joining a composite blade and at least one support member using injection bonding, the support member comprising an inlet, an outlet, and a cavity, one end of the blade being positioned within the cavity of the support member, wherein a seal surrounds the one end of the support member, wherein the seal is configured to prevent adhesive from exiting the one end of the cavity and is configured to form the adhesive into a rounded shape, the method comprising: injecting adhesive between the blade and the support through the inlet, and The adhesive flow is reversed so that at least a portion of the predetermined amount of adhesive flows back between the blade and the support.

16. An aircraft engine component manufactured by the method according to any one of claims 1 to 14.

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