Composite material propeller blade structure and manufacturing method thereof

Abstract

The invention discloses a composite material propeller blade structure and a manufacturing method thereof. The composite material propeller blade structure comprises a supporting pipe; the girder layer comprises a middle girder, a front edge girder and a rear edge girder; the skin layer comprises a first skin, a second skin and a third skin; the threaded sleeve is arranged on the outer side of the first skin, and external threads are arranged on the outer side of the threaded sleeve; the cloth liner layer is arranged on the outer side of the first skin; and the metal pipe fitting is used for being connected with a propeller hub and is in threaded connection with the threaded sleeve. According to the invention, the blades made of the composite material are arranged and are cured to form a whole body, so that firm interface bonding is formed, loads are effectively transmitted, stress concentration is avoided, the propeller can be suitable for low-rotating-speed and large-load electric vertical take-off and landing aircrafts, and the structural weight is reduced and the reliability is improved while the connection reliability is ensured.

Description

Technical Field

[0001] This invention relates to the field of electric aircraft, and in particular to a composite material propeller blade structure and its manufacturing method. Background Technology

[0002] The propellers of electric vertical takeoff and landing (EVTOL) aircraft operate differently from traditional propellers and rotor structures. EVTOL propellers have lower rotational speeds, lower centrifugal forces, and simpler structures than traditional propellers, and are typically manufactured using conventional molding processes.

[0003] However, the propellers of traditional electric vertical takeoff and landing aircraft are much smaller than those of traditional rotors, making it impossible to use the root double-pin structure of traditional rotors.

[0004] Therefore, there is an urgent need to design a propeller structure suitable for low-speed, high-load electric vertical take-off and landing aircraft, which can reduce structural weight and improve reliability while ensuring connection reliability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a composite material propeller blade structure that is suitable for low-speed, high-load electric vertical take-off and landing aircraft, reducing structural weight and improving reliability while ensuring connection reliability.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a composite material propeller blade structure, comprising: The support tube includes an integrally formed root tube and a transition tube. The root tube is located at the root section of the blade, and the transition tube extends from the connection between the root section and the transition section of the blade to the middle of the transition section. The main beam layer includes a middle main beam, a leading edge main beam, and a trailing edge main beam. The middle main beam is located outside the support tube and extends from the root section of the blade through a transition section to the tip of the airfoil section. A first foam core is provided inside the middle main beam and is inserted into the transition tube. The leading edge main beam and the trailing edge main beam are distributed at the leading and trailing edges of the airfoil section of the blade. The skin layer includes a first skin, a second skin, and a third skin. The first skin is disposed on the outside of the intermediate spar and extends from the root end of the blade to the connection between the transition section and the airfoil section. The second skin is disposed between the first foam core and the intermediate spar and extends from the connection between the transition section and the airfoil section of the blade to the tip of the airfoil section. The third skin surrounds the outside of the intermediate spar and is bulging to form the blade shell. A second foam core is disposed between the inner side of the third skin and the outer side of the intermediate spar. The leading edge spar and the trailing edge spar are disposed on the inner side of the third skin. A threaded sleeve is disposed on the outer side of the first skin, and the outer side is provided with external threads; A padding layer is disposed on the outside of the first skin. The padding layer is narrow at both ends and wide in the middle, and extends from the inside of the threaded sleeve near its end to the connection between the transition section of the blade and the airfoil section. A metal tubular fitting for connecting a propeller hub, with an internal thread on the inner side for threaded connection with the threaded sleeve.

[0007] In a preferred embodiment, the present invention can be further configured such that the first third of the root tube is cylindrical and the last two-thirds is frustum-shaped with a gradually decreasing 2° inclination angle in the cross-section.

[0008] In a preferred embodiment, the present invention may be further configured such that: the first skin is made of carbon fiber fabric prepreg and glass fiber fabric prepreg laid at different angles, and the second skin and the third skin are both made of carbon fiber fabric prepreg.

[0009] In a preferred embodiment, the present invention may be further configured such that the opening at the junction of the root section and the transition section of the third skin near the blade is sealed with a layer of epoxy resin carbon fiber fabric composite material.

[0010] In a preferred embodiment, the present invention may be further configured such that the threaded sleeve includes a pair of sleeves, the sleeves being semi-circular and divided into two parts in the circumferential direction, which are engaged with each other, and the engagement position of the sleeves being toothed.

[0011] In a preferred embodiment, the present invention can be further configured such that: the threaded sleeve and the metal pipe are provided with interconnected positioning holes, and a positioning pin is threaded into the positioning hole.

[0012] Another objective of this invention is to provide a method for manufacturing a composite material propeller blade structure that can reduce structural weight and improve reliability while ensuring connection reliability.

[0013] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for manufacturing a composite material propeller blade structure, comprising the following steps: S1, a support tube of unidirectional carbon fiber composite material is prepared by molding process, and the first foam core is inserted into the support tube; S2, the second skin is laid on the outside of the first foam core; S3, lay the middle beam on the outside of the support tube and the second skin; S4, lay the first skin on the outside of the middle beam; S5, the padding layer is laid on the outside of the first skin; S6, the threaded sleeve is fitted onto the outside of the first skin; S7, attach the third skin to the inside of the mold; S8, lay the front edge beam and the rear edge beam on the inner side of the front edge and the rear edge of the third skin; S9, install the second foam core between the inner side of the third skin and the outer side of the intermediate beam; S10, snap the mold together and then perform thermosetting treatment; S11. Apply adhesive to the threaded sleeve, then thread the metal pipe fitting onto the threaded sleeve, and screw the locating pin into the corresponding locating hole.

[0014] In summary, the present invention has the following beneficial effects: 1. By setting composite material blades and forming them into a whole through curing, a strong interface bond is formed, which effectively transfers loads, avoids stress concentration, and is applicable to low-speed, high-load electric vertical take-off and landing aircraft. While ensuring connection reliability, it reduces structural weight and improves reliability. 2. By setting a support tube with a unique structural shape, the blades can be prevented from detaching from the threaded sleeve when they are subjected to large centrifugal forces during rotation, thus ensuring flight safety; 3. By installing a support pipe at the root of the blade, support force can be provided to the root of the main beam layer, preventing the main beam layer from being damaged due to internal pressure; 4. By laying carbon fiber fabric prepreg and glass fiber fabric prepreg at different angles to form a skin layer, it can bear loads in multiple directions and reduce the load on the main beam layer. 5. By using threaded sleeves and metal fittings together, the blades can be easily installed, and they will not bend due to external loads during rotation, which is beneficial for the blades to withstand greater loads. 6. The threaded sleeve is made of aluminum alloy, which makes the overall weight of the blade light, the moment of inertia of the blade small, the angular acceleration large, and the response speed fast. The threaded sleeve is divided into two parts in the circumferential direction, and the connection is a toothed structure that interlocks with each other. It can provide pressure during the blade molding process, so that the blade root has higher strength, which can ensure the accuracy of installation and prevent rotation, making the blade root structure more robust and reliable. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of Example 1; Figure 2 This is a schematic diagram of the connection relationship in Example 1; Figure 3 This is a schematic diagram of the support tube structure of Example 1; Figure 4 This is a schematic diagram of the internal structure of Example 1; Figure 5 This is a schematic diagram of the internal structure of the threaded sleeve and metal pipe fitting in Example 1; Figure 6 This is a schematic diagram of the threaded sleeve in Example 1; Figure 7 This is a schematic diagram of the metal pipe fitting in Example 1.

[0016] Reference numerals: 1. Support tube; 11. Root tube; 12. Transition tube; 2. Main beam layer; 21. Intermediate main beam; 22. Front edge main beam; 23. Rear edge main beam; 3. Skin layer; 31. First skin; 32. Second skin; 33. Third skin; 4. Threaded sleeve; 41. Sleeve; 5. Pad layer; 6. Metal fitting; 7. First foam core; 8. Second foam core; 9. Positioning hole. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings.

[0018] Example 1: like Figure 1 , Figure 2 As shown, a composite material propeller blade structure is divided into a root section, a transition section, and an airfoil section arranged sequentially from front to back. The blade structure includes a support tube 1, a main beam layer 2, a skin layer 3, a threaded sleeve 4, a padding layer 5, and a metal fitting 6.

[0019] like Figure 2 , Figure 3 As shown, the support tube 1 is pre-formed using unidirectional carbon fiber prepreg, including an integrally formed root tube 11 and transition tube 12. The root tube 11 is located at the root section of the blade, and the transition tube 12 extends from the connection between the root section and the transition section of the blade to the middle of the transition section.

[0020] like Figure 2 , Figure 3 As shown, the first third of the root tube 11 is cylindrical, while the latter two-thirds are frustum-shaped with a gradually decreasing 2° inclination angle in cross-section. This provides support to the main beam layer 2 during molding, preventing it from being damaged by internal pressure. The 2° inclination angle of the root tube 11 also prevents the blade from experiencing excessive centrifugal force during rotation, avoiding separation of the blade from the threaded sleeve 45 and ensuring flight safety.

[0021] like Figure 2 As shown, the main beam layer 2 is made of unidirectional carbon fiber composite material, which serves as the main load-bearing structure to withstand centrifugal force, waving, waving bending moment, lift, etc. on the propeller.

[0022] like Figure 2 , Figure 4As shown, the main spars 2 includes a central spars 21, a leading-edge spars 22, and a trailing-edge spars 23. The central spars 21 is located outside the support tube 1 and extends from the root end of the blade through a transition section to the tip of the airfoil section. A first foam core 7 is installed inside the central spars 21 and is inserted into the transition tube 12. The first foam core 7 is made of polymethacrylimide structural core material and provides support and protection for the main spars 2 of the blade section. The leading-edge spars 22 and trailing-edge spars 23 are located at the leading and trailing edges of the airfoil section of the blade.

[0023] like Figure 2 , Figure 4 As shown, the skin layer 3 is used to maintain the aerodynamic shape and bear part of the swinging moment and swaying moment. The skin layer 3 includes a first skin 31, a second skin 32 and a third skin 33. The first skin 31 is made of carbon fiber fabric prepreg and glass fiber fabric prepreg laid at different angles. The second skin 32 and the third skin 33 are both made of carbon fiber fabric prepreg, which can bear loads in multiple directions and reduce the load on the beam.

[0024] like Figure 2 , Figure 4 As shown, the first skin 31 is disposed on the outside of the intermediate beam 21, extending from the end of the root section of the blade to the connection between the transition section and the airfoil section. The second skin 32 is disposed between the first foam core 7 and the intermediate beam 21, extending from the connection between the transition section and the airfoil section of the blade to the tip of the airfoil section. The third skin 33 surrounds the outside of the intermediate beam 21 and is bulging in shape, forming the blade shell, while the leading edge beam 22 and the trailing edge beam 23 are disposed on the inside of the third skin 33.

[0025] like Figure 2 , Figure 4 As shown, a second foam core 8 is provided between the inner side of the third skin 33 and the outer side of the middle beam 21. The second foam core 8 is a polymethacrylimide structural core material, which is used to support the third skin 33 and prevent the structure of the third skin 33 from becoming unstable.

[0026] like Figure 2 , Figure 4 As shown, the opening at the junction of the root section and the transition section of the third skin 33 near the blade is sealed with a layer of epoxy resin carbon fiber woven fabric composite material to ensure the sealing of the inner cavity of the third skin 33, maintain the aerodynamic shape, and withstand part of the flapping moment and swaying moment.

[0027] like Figure 2 , Figure 5 , Figure 6 , Figure 7As shown, the threaded sleeve 4 is located on the outer side of the first skin 31, and has external threads on the outer side. The threaded sleeve 4 is made of aluminum alloy, which makes the overall weight of the blade light, the moment of inertia of the blade small, the angular acceleration large, and the response speed fast.

[0028] like Figure 5 , Figure 6 , Figure 7 As shown, the threaded sleeve 4 includes a pair of sleeve pieces 41. The sleeve pieces 41 are semi-circular and divided into two parts in the circumferential direction, which are interlocked with each other. The interlocking position of the sleeve pieces 41 is toothed, which can provide pressure to the internal beam layer 2 during blade molding, ensure the molding quality of the beam layer 2, and reduce manufacturing defects of the beam layer 2 at the blade root.

[0029] like Figure 2 As shown, the padding layer 5 is disposed on the outside of the first skin 31. The padding layer 5 is narrow at both ends and wide in the middle, and extends from the threaded sleeve 4 near its end to the connection between the transition section of the blade and the airfoil section. The padding layer 5 can prevent the threaded sleeve 4 from rubbing against the middle beam 21 during the rotation of the blade, and has a protective function for the beam layer 2.

[0030] like Figure 5 , Figure 6 , Figure 7 As shown, the metal tube 6 is used to connect the propeller hub. The metal tube 6 is integrally formed, made of titanium, and has internal threads on the inside. It is connected to the threaded sleeve 4 by threads and glue, which can prevent the beam layer 2 from bending under external loads during rotation, which is beneficial for the blade to withstand greater loads.

[0031] like Figure 5 , Figure 6 , Figure 7 As shown, the threaded sleeve 4 and the metal pipe fitting 6 are provided with interconnected positioning holes 9. The positioning holes 9 are internally threaded with positioning pins, which can ensure the accuracy of installation and prevent rotation, making the blade root structure more robust and reliable.

[0032] Example 2: A method for manufacturing a composite material propeller blade structure includes the following steps: S1, a support tube 1 of unidirectional carbon fiber composite material is prepared by molding process, and the first foam core 7 is inserted into the support tube 1.

[0033] S2, the second skin 32 is laid on the outside of the first foam core 7.

[0034] S3, lay the middle beam 21 on the outside of the support tube 1 and the second skin 32.

[0035] S4, the first skin 31 is laid on the outside of the middle beam 21.

[0036] S5, the padding layer 5 is laid on the outside of the first skin 31.

[0037] S6, the threaded sleeve 4 is fitted onto the outside of the first skin 31.

[0038] S7, the third skin 33 is laid and attached to the inside of the mold.

[0039] S8, the front edge beam 22 and the rear edge beam 23 are laid on the inner sides of the front and rear edges of the third skin 33.

[0040] S9, install the second foam core 8 between the inner side of the third skin 33 and the outer side of the intermediate beam 21.

[0041] S10, snap the mold together, and then perform heat curing treatment.

[0042] S11, apply adhesive to the threaded sleeve 4, then thread the metal pipe 6 onto the threaded sleeve 4, and screw the locating pin into the corresponding locating hole 9.

[0043] The specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A composite material propeller blade structure, characterized in that: include: The support tube (1) includes an integrally formed root tube (11) and a transition tube (12). The root tube (11) is located at the root section of the blade, and the transition tube (12) extends from the connection between the root section and the transition section of the blade to the middle of the transition section. The main beam layer (2) includes a middle main beam (21), a leading edge main beam (22) and a trailing edge main beam (23). The middle main beam (21) is located outside the support tube (1) and extends from the root section of the blade through a transition section to the tip of the airfoil section. A first foam core (7) is provided inside the middle main beam (21). The first foam core (7) is inserted into the transition tube (12). The leading edge main beam (22) and the trailing edge main beam (23) are distributed at the leading edge and trailing edge of the airfoil section of the blade. The skin layer (3) includes a first skin (31), a second skin (32) and a third skin (33). The first skin (31) is disposed on the outside of the intermediate beam (21). The first skin (31) extends from the end of the root section of the blade to the connection between the transition section and the airfoil section. The second skin (32) is disposed between the first foam core (7) and the intermediate beam (21). It extends from the connection between the transition section of the blade and the airfoil section to the tip of the airfoil section. The third skin (33) surrounds the outside of the intermediate beam (21) and is bulging, forming the blade shell. A second foam core (8) is disposed between the inner side of the third skin (33) and the outer side of the intermediate beam (21). The leading edge beam (22) and the trailing edge beam (23) are disposed on the inner side of the third skin (33). A threaded sleeve (4) is provided on the outside of the first skin (31), and the outside is provided with external threads; A padding layer (5) is provided on the outside of the first skin (31). The padding layer (5) is narrow at both ends and wide in the middle, and extends from the inside of the threaded sleeve (4) near its end to the connection between the transition section of the blade and the airfoil section. A metal tube (6) is used to connect the propeller hub and has an internal thread on its inner side, which is threaded to the threaded sleeve (4).

2. The composite material propeller blade structure according to claim 1, characterized in that: The first third of the root tube (11) is cylindrical, and the last two-thirds is frustum-shaped with a gradually decreasing 2° inclination angle in the cross-section.

3. The composite material propeller blade structure according to claim 1, characterized in that: The first skin (31) is made of carbon fiber fabric prepreg and glass fiber fabric prepreg laid at different angles, and the second skin (32) and the third skin (33) are both made of carbon fiber fabric prepreg.

4. The composite material propeller blade structure according to claim 1, characterized in that: The opening at the junction of the root section and the transition section of the third skin (33) near the blade is sealed with a layer of epoxy resin carbon fiber fabric composite material.

5. The composite material propeller blade structure according to claim 1, characterized in that: The threaded sleeve (4) includes a pair of sleeve pieces (41), which are semi-circular and divided into two parts in the circumferential direction and are interlocked with each other. The interlocking position of the sleeve pieces (41) is toothed.

6. The composite material propeller blade structure according to claim 5, characterized in that: The threaded sleeve (4) and the metal pipe (6) are provided with interconnected positioning holes (9), and positioning pins are threadedly connected to the positioning holes (9).

7. A method for manufacturing a composite material propeller blade structure, characterized in that: Includes the following steps: S1, a support tube (1) of unidirectional carbon fiber composite material is prepared by molding process, and the first foam core (7) is inserted into the support tube (1); S2, the second skin (32) is laid on the outside of the first foam core (7); S3, the middle beam (21) is laid on the outside of the support tube (1) and the second skin (32); S4, the first skin (31) is laid on the outside of the middle beam (21); S5, the padding layer (5) is laid on the outside of the first skin (31); S6, the threaded sleeve (4) is fitted onto the outside of the first skin (31); S7, the third skin (33) is laid and attached to the inside of the mold; S8, the front edge beam (22) and the rear edge beam (23) are laid on the inner side of the front and rear edges of the third skin (33); S9, install the second foam core (8) between the inner side of the third skin (33) and the outer side of the middle beam (21); S10, snap the mold together and then perform thermosetting treatment; S11, apply adhesive to the threaded sleeve (4), then thread the metal pipe (6) onto the threaded sleeve (4), and screw the locating pin into the corresponding locating hole (9).

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