Unmanned aerial vehicle paddle structure and manufacturing method thereof

Abstract

The invention relates to an unmanned aerial vehicle paddle structure and a manufacturing method thereof.A paddle root, a paddle upper skin and a paddle lower skin of the unmanned aerial vehicle paddle structure are all made of the same first fiber reinforced thermoplastic composite material, and a paddle supporting piece is made of a second fiber reinforced thermoplastic composite material; the melting temperature of the second fiber-reinforced thermoplastic composite material is higher than that of the first fiber-reinforced thermoplastic composite material, and when the paddle supporting piece is subjected to injection molding, fusion at the interface of the two materials is promoted through the difference of the melting temperatures of the two resins, so that rapid integrated molding of the unmanned aerial vehicle paddle structure is realized; and the manufacturing cost is reduced while the structural strength of the paddle is improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials and low-altitude aircraft engineering, and in particular to a UAV blade structure and a manufacturing method thereof. Background Art

[0002] With the rapid development of low-altitude aircraft technology, the demand for high-performance materials in the field of low-altitude aircraft is growing. In low-altitude aircraft such as drones, helicopters, and fixed-wing aircraft, the blades are key components that withstand high-cycle fatigue and impact, so they need to have good impact resistance, fatigue resistance, and long-term service capabilities.

[0003] The use of thermosetting composite materials to form the UAV blade structure can reduce the overall weight of the UAV, but it is limited by the long molding and manufacturing cycle. Therefore, the manufacturing cost is greatly increased, and a material and process that can be automatically and quickly molded is urgently needed. Compared with thermosetting materials, thermoplastic composites have significant advantages such as low water absorption, excellent corrosion resistance, fatigue resistance, impact resistance and rapid repairability. They can better adapt to harsh environmental conditions such as wet / hot, dry / cold, dust / rain and seawater. Therefore, thermoplastic composites have great potential in UAV applications. However, thermoplastic composites also have problems such as low interfacial adhesion and high material cost. Therefore, it is necessary to propose a low-cost method for manufacturing UAV blades to reduce the manufacturing cycle and manufacturing cost of the blades while ensuring that the aerodynamic shape of the blades remains unchanged. Summary of the invention

[0004] The purpose of the present invention is to provide a UAV blade structure with low manufacturing cost.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A UAV blade structure comprises a blade root, a blade upper skin, a blade lower skin and a blade support member, wherein the blade root is fixedly connected to the root of the blade support member, the blade upper skin covers the upper surface of the blade root and the blade support member, the blade lower skin covers the lower surface of the blade root and the blade support member, the blade root, the blade upper skin and the blade lower skin are all made of the same first fiber reinforced thermoplastic composite material, and the blade support member is made of a second fiber reinforced thermoplastic composite material, and the melting temperature of the second fiber reinforced thermoplastic composite material is higher than the melting temperature of the first fiber reinforced thermoplastic composite material.

[0007] In one embodiment, the blade root, the blade upper skin and the blade lower skin are all made of continuous fiber reinforced thermoplastic composite materials, and the blade support is made of chopped fiber reinforced thermoplastic composite materials.

[0008] In one embodiment, the difference between the melting temperatures of the second fiber-reinforced thermoplastic composite material and the first fiber-reinforced thermoplastic composite material is greater than 40 degrees.

[0009] Another object of the present invention is to provide a method for manufacturing a drone blade structure with low manufacturing cost, comprising the following steps:

[0010] S1. Selecting a continuous fiber reinforced thermoplastic resin composite prepreg tape with a set volume fraction;

[0011] S2, press-molding the continuous fiber reinforced thermoplastic resin composite material prepreg tape into a skin blank and a blade root blank according to a set layering method;

[0012] S3, stamping the molded continuous fiber reinforced thermoplastic resin composite skin blank laminate into a UAV blade skin;

[0013] S4, performing hole making, cutting and machining on the continuous fiber reinforced thermoplastic resin composite material blade root blank laminate after molding according to the design size requirements;

[0014] S5. Place the UAV blade skin and blade root inside the injection mold, and use short fiber reinforced thermoplastic composite materials for injection molding to form the UAV blade.

[0015] In one embodiment, in step S2: firstly, the continuous fiber reinforced thermoplastic prepreg tape is formed into a preform by ultrasonic welding; and then the preform is placed in a flat mold for compression molding into a continuous fiber reinforced thermoplastic resin composite laminate.

[0016] In one embodiment, in step S2: the laying method is calculated according to the structural load-bearing requirements of the blade.

[0017] In one embodiment, in step S2, the compression molding process is: pre-pressing temperature: 100-300°C, pre-pressing time: 10-30 min, pre-pressing pressure 0.2-0.5 MPa; boosting temperature: 100-400°C, boosting time: 30-60 min, boosting pressure: 1-8 MPa.

[0018] In one embodiment, in step S3: the continuous fiber reinforced thermoplastic resin composite laminate is transferred to a stamping machine for stamping and forming after being infrared heated.

[0019] In one embodiment, in step S3: the temperature of infrared heating is 100-400°C.

[0020] In one embodiment, in step S3: the stamping process is: stamping die temperature: 20-200° C., stamping rate: 1-200 mm / s, stamping pressure: 1-8 MPa.

[0021] In one embodiment, the shape of the skin structure after stamping is trimmed.

[0022] In one embodiment, in step S5: the injection molding process is: injection temperature: 100-400°C, injection pressure: 30-140 bar, injection time: 1-10 s, mold temperature: 25-200°C, holding time: 3-30 s, holding pressure: 30-140 bar, post-cooling time: 3-120 s.

[0023] In one embodiment, the continuous fibers in the continuous fiber reinforced thermoplastic prepreg tape are one or more of carbon fibers, glass fibers, and aramid fibers, and the chopped fibers in the chopped fiber reinforced thermoplastic composite material are one or more of carbon fibers, glass fibers, and aramid fibers.

[0024] In one embodiment, the mass fraction of resin in the continuous fiber reinforced thermoplastic prepreg tape is 30% to 50%.

[0025] In one embodiment, the mass fraction of the resin in the chopped fiber reinforced thermoplastic composite material is 60-90%.

[0026] In one embodiment, the chopped fiber reinforced thermoplastic composite material is one of polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyaryletherketone, and polyimide.

[0027] The present invention adopts the above technical solution, which has the beneficial effects of:

[0028] 1. The UAV blade structure provided by the present invention is formed by thermoplastic composite materials with different melting temperatures, which can improve the fatigue resistance and impact resistance of the blade, improve the manufacturing efficiency of the UAV blade structure, and extend the service life of the blade.

[0029] 2. The present invention adopts the method of in-mold injection molding, combining the molding process of continuous fiber reinforced thermoplastic composite materials with the injection molding process of short fiber reinforced thermoplastic composite materials, and improves the fatigue resistance and load-bearing performance of the UAV blades by molding the skin and the blade root with continuous fiber reinforced thermoplastic composite materials. The blade support material is molded by short fiber reinforced thermoplastic composite materials to ensure the aerodynamic shape of the product. This process can effectively improve the manufacturing efficiency of UAVs and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the UAV blade structure is shown. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0032] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other cases, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0033] Unless the context requires otherwise, throughout the specification and claims, the word "comprise" and variations such as "include" and "have" should be construed in an open, inclusive sense, ie, should be interpreted as "including, but not limited to."

[0034] References throughout the specification to "one embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0035] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0036] In the following description, in order to clearly show the structure and working mode of the present invention, many directional words will be used for description, but the words "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", "down", etc. should be understood as convenient terms and should not be understood as restrictive terms.

[0037] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0039] like Figure 1 As shown, the present invention provides a UAV blade structure, including a blade root 1, a blade upper skin 2, a blade lower skin 3 and a blade support 4, wherein the blade root 1 is fixedly connected to the root of the blade support 4, the blade upper skin 2 covers the upper surface of the blade root 1 and the blade support 4, and the blade lower skin 3 covers the lower surface of the blade root 1 and the blade support 4.

[0040] The propeller root 1, the blade upper skin 2 and the blade lower skin 3 are all made of continuous fiber reinforced thermoplastic composite materials, such as continuous carbon fiber reinforced polyaryletherketone (CCF / PAEK) materials. The propeller root 1, the blade upper skin 2 and the blade lower skin 3 can select the corresponding resin mass fraction according to the load-bearing requirements and fatigue performance requirements.

[0041] The blade support member 4 is made of a chopped fiber reinforced thermoplastic composite material, for example, it is made of a chopped carbon fiber reinforced polyetheretherketone (SCF / PEEK) material. The thermoplastic composite material used in the blade support member 4 has a different resin melting temperature from the thermoplastic composite material used in the blade root 1, the blade upper skin 2, and the blade lower skin 3, and the melting temperature of the thermoplastic composite material used in the blade support member 4 is higher than the melting temperature of the thermoplastic composite material used in the blade root 1, the blade upper skin 2, and the blade lower skin 3. When the blade support member 4 is injection molded, the difference in the melting temperatures of the two resins is used to promote the fusion of the two materials at the interface, thereby improving the integrity of the UAV blade structure. Compared with the traditional thermosetting composite hand lay-up molding, the UAV blade structure of the present invention can improve its fatigue resistance and extend its service life.

[0042] The present invention also provides a manufacturing method for manufacturing the above-mentioned unmanned aerial vehicle blade structure, wherein the blade root 1, the blade upper skin 2 and the blade lower skin 3 are formed by a molding process, and the blade upper skin 2 and the blade lower skin 3 are then formed into a skin structure with curvature by a stamping process. The blade support 4 is formed by injection molding, and the blade upper skin 2, the blade lower skin 3 and the blade root 1 formed into a skin structure with curvature by a stamping process are placed in the injection mold of the blade support 4. When the blade support 4 is injection molded, the blade upper skin 2, the blade lower skin 3 and the blade root 1 are fixed to the blade support 4 as a whole, so as to realize high-efficiency and low-cost manufacturing of unmanned aerial vehicle blades.

[0043] Specifically, a continuous fiber reinforced thermoplastic composite prepreg and a short fiber reinforced thermoplastic composite are first prepared. The fibers include but are not limited to carbon fibers, glass fibers, organic fibers or other mixed fibers. This type of fiber material has high strength, corrosion resistance and fatigue resistance. Thermoplastic resins include but are not limited to PEEK, PAEK, PPS, PES, PEI, PA6T, PA6, PA66, PA11, PA12, PP, PE and other thermoplastic resins. In this embodiment, two similar resins with different melting temperatures are used as examples for illustration.

[0044] The UAV blade structure is formed from the outside to the inside, and the blade root is formed by a molding process. Specifically, a continuous fiber reinforced thermoplastic prepreg tape with a certain resin mass fraction is ultrasonically welded according to the specified layer to form a preform, and then molded into a blade root blank by a molding process. After mechanical processing, punching and repairing the shape, the blade root 1 is formed.

[0045] The skin structure adopts a molding process combined with a stamping process. Specifically, a continuous fiber reinforced thermoplastic prepreg tape with a certain resin mass fraction is ultrasonically welded according to the specified layup to form a preform, and a skin blank is formed by a molding process. The skin blank is machined, punched, and fixed in a clamping device, and then a stamping process is used to form a skin structure with a certain curvature. During the stamping process, the transfer and stamping molds must be quickly transferred and closed to ensure that there are no pores inside the blank and it is tightly combined. After machining, punching and repairing the shape, the upper skin 2 of the blade and the lower skin 3 of the blade are formed respectively.

[0046] The blade support structure inside the blade is made by injection molding. Specifically, the upper and lower skins and the blade root are placed in the mold in advance, and then the chopped fiber reinforced thermoplastic composite particles with a certain resin mass fraction are injected into the mold. The mold itself has a heating function during injection molding. The injection molding process relies on injection pressure to achieve a close combination of the short fiber reinforced thermoplastic composite material and the continuous fiber reinforced thermoplastic composite material layer. Among them, the presence of short fibers is conducive to the formation of a "pinning effect" at the interface, further enhancing the interface bonding between the two.

[0047] After the injection molding process is completed, the ejection mechanism inside the mold can remove the drone blade structure from the mold, and the end face is machined and trimmed to the required precise size, and finally a rapidly formed drone blade structure is obtained. The manufacturing method provided by the present invention combines the molding process, the stamping process and the injection molding process, and rapidly forms the drone blade structure through in-mold injection molding, thereby achieving efficient and low-cost manufacturing, significantly reducing the porosity, and optimizing the interlayer bonding quality. The process effectively improves the structural integrity and mechanical properties of the drone blade, thereby significantly enhancing the fatigue resistance of the blade structure and extending the service life.

[0048] In addition, in the molding process of the thermoplastic composite drone blade structure, the two resins in the continuous fiber reinforced thermoplastic composite and the short fiber reinforced thermoplastic composite are preferably two resins with similar structures with large differences in melting temperatures, and the difference in melting temperatures of the two resins is preferably greater than or equal to 40 degrees. For example, continuous fiber reinforced polyaryletherketone resin-based composite materials and short fiber reinforced polyetheretherketone resin-based composite materials. The melting temperature of polyetheretherketone resin is 343°C, and the melting temperature of polyaryletherketone resin is 305°C. In view of the fact that the temperature of short fiber reinforced polyetheretherketone resin-based composite materials needs to be increased during the injection molding process to increase the fluidity of the melt, its melt temperature often reaches above 360°C, which is much higher than the melting temperature of 305°C of continuous fiber reinforced polyaryletherketone resin-based composite materials, and therefore, it is conducive to the melt bonding of the two materials. The whole process involves the coupling of multiple physical fields such as temperature field, force field and resin flow. These actions are completed efficiently in a short time, thereby greatly improving the molding efficiency and realizing rapid manufacturing and high-precision molding of materials.

[0049] Example 1

[0050] This embodiment uses the above manufacturing method to manufacture a thermoplastic composite UAV blade structure to achieve rapid and low-cost molding of a thermoplastic composite UAV blade structure. The blade root is molded, the blade upper skin and blade lower skin are molded by a molding process combined with a stamping process, and the blade support is molded by an injection molding process to achieve rapid and low-cost manufacturing of the UAV blade structure.

[0051] Specifically, CF / PAEK prepreg tape with a resin mass fraction of 34%, a width of 100mm and a thickness of 0.15mm is used to ensure uniform material specifications.

[0052] The blade root is formed by molding. A metal mold with a diameter of 50mm and a thickness of 19.2mm is selected. The mold surface is mechanically polished to a finish of Ra 0.8. A release agent is evenly coated on the mold surface to ensure that a uniform release protective film is formed on the mold surface. CCF / PAEK prepreg is placed at [+45° / 0° / -45° / 90°]16s The preform is formed by cutting, welding and paving in a layered manner. The preform is placed in a metal mold coated with a release agent and transferred to a molding machine. The molding process is as follows: pre-pressing temperature: 300℃, pre-pressing time: 30min, pre-pressing pressure: 0.5MPa; boosting temperature: 360℃, boosting time: 60min, boosting pressure: 8MPa. After the molding process is completed, the temperature starts to drop and demoulding starts when it drops to about 80℃. After demoulding, the blade root blank is obtained. The blade root blank is processed and shaped according to the drawing to obtain the blade root.

[0053] The upper and lower skins are formed by a combination of molding and stamping. A metal mold of 800*100*2.4mm is selected. The mold surface is mechanically polished to a finish of Ra 0.8. A release agent is evenly applied to the mold surface to ensure that a uniform release protective film is formed on the mold surface. CCF / PAEK prepreg is placed at [±45°] 4s The preform is formed by cutting, welding and paving in a layering manner. The preform is placed in a metal mold coated with a release agent and transferred to a molding machine. The molding process is as follows: pre-pressing temperature: 300℃, pre-pressing time: 30min, pre-pressing pressure: 0.5MPa; boosting temperature: 360℃, boosting time: 60min, boosting pressure: 2MPa. After the molding process is completed, the temperature begins to drop, and demolding begins when it drops to about 80℃. After demolding, the skin blank is obtained. The blank is punched and fixed to the clamping device, and stamping begins. The temperature of infrared heating is 400℃, the temperature of the stamping die is room temperature, the stamping rate is 50mm / s, and the stamping pressure is 5MPa. After stamping, a skin blank with curvature is obtained, which is processed according to the drawing and shaped to obtain the upper and lower skins.

[0054] The internal blade support adopts the injection molding process. The upper and lower skins and the blade root are placed in the injection mold respectively. The short carbon fiber reinforced polyetheretherketone thermoplastic composite material particles with a resin mass fraction of 70% are used for injection molding. The injection molding process is: injection temperature: 400℃, injection pressure: 140bar, injection time: 8s, mold temperature: 200℃, holding time: 30s, holding pressure: 140bar, post-cooling time: 120s. After the injection molding is completed, trimming is carried out and the blade structure is formed.

[0055] The preferred embodiments of the present invention have been described in detail above, but it should be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A UAV blade structure, comprising a blade root, a blade upper skin, a blade lower skin and a blade support, wherein the blade root is fixedly connected to the root of the blade support, the blade upper skin covers the upper surface of the blade root and the blade support, and the blade lower skin covers the lower surface of the blade root and the blade support, characterized in that: The blade root, blade upper skin and blade lower skin are all made of the same first fiber reinforced thermoplastic composite material, and the blade support is made of a second fiber reinforced thermoplastic composite material, and the melting temperature of the second fiber reinforced thermoplastic composite material is higher than the melting temperature of the first fiber reinforced thermoplastic composite material.

2. The UAV blade structure according to claim 1, characterized in that: The blade root, the blade upper skin and the blade lower skin are all made of continuous fiber reinforced thermoplastic composite materials, and the blade support is made of chopped fiber reinforced thermoplastic composite materials.

3. The UAV blade structure according to claim 1, characterized in that: The difference in melting temperature between the second fiber-reinforced thermoplastic composite material and the first fiber-reinforced thermoplastic composite material is greater than 40 degrees.

4. A method for manufacturing a drone blade structure, characterized in that: The following steps are involved: S1. Selecting a continuous fiber reinforced thermoplastic resin composite prepreg tape with a set volume fraction; S2, press-molding the continuous fiber reinforced thermoplastic resin composite material prepreg tape into a skin blank and a blade root blank according to a set layering method; S3, stamping the molded continuous fiber reinforced thermoplastic resin composite skin blank laminate into a UAV blade skin; S4, performing hole making, cutting and machining on the continuous fiber reinforced thermoplastic resin composite material blade root blank laminate after molding according to the design size requirements; S5. Place the UAV blade skin and blade root inside the injection mold, and use short fiber reinforced thermoplastic composite materials for injection molding to form the UAV blade.

5. The manufacturing method according to claim 4, characterized in that: In step S2: firstly, the continuous fiber reinforced thermoplastic prepreg tape is formed into a preform by ultrasonic welding; and then the preform is placed in a flat mold for compression molding into a continuous fiber reinforced thermoplastic resin composite laminate.

6. The manufacturing method according to claim 4, characterized in that: In step S2, the compression molding process is: pre-pressing temperature: 100-300°C, pre-pressing time: 10-30min, pre-pressing pressure 0.2-0.5MPa; boosting temperature: 100-400°C, boosting time: 30-60min, boosting pressure: 1-8MPa.

7. The manufacturing method according to claim 4, characterized in that: In step S3: the stamping process is: stamping die temperature: 20-200°C, stamping rate: 1-200 mm / s, stamping pressure: 1-8 MPa.

8. The manufacturing method according to claim 4, characterized in that: In step S5: the injection molding process is: injection temperature: 100-400°C, injection pressure: 30-140 bar, injection time: 1-10 s, mold temperature: 25-200°C, holding time: 3-30 s, holding pressure: 30-140 bar, post-cooling time: 3-120 s.

9. The manufacturing method according to claim 4, characterized in that: The mass fraction of the resin in the continuous fiber reinforced thermoplastic prepreg is 30% to 50%, and the mass fraction of the resin in the chopped fiber reinforced thermoplastic composite material is 60% to 90%.

10. The manufacturing method according to claim 4, characterized in that: The continuous fibers in the continuous fiber reinforced thermoplastic prepreg tape are one or more of carbon fibers, glass fibers, and aramid fibers; the chopped fibers in the chopped fiber reinforced thermoplastic composite material are one or more of carbon fibers, glass fibers, and aramid fibers; the thermoplastic resin in the continuous fiber reinforced thermoplastic prepreg tape is one of polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyaryletherketone, and polyimide; the chopped fiber reinforced thermoplastic composite material is one of polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyaryletherketone, and polyimide.

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