Skin structure manufacturing method, skin structure and unmanned aerial vehicle

Abstract

The invention belongs to the technical field of unmanned aerial vehicle design and manufacturing, and discloses a skin structure manufacturing method, a skin structure and an unmanned aerial vehicle. The skin structure manufacturing method comprises the following steps that the thickness of a skin and the equivalent height of a reinforcing rib are determined according to the preset shear stress of the skin structure; carrying out pultrusion on the reinforcing ribs; determining the size and the distribution position of the reinforcing ribs according to the preset buckling stress of the skin structure, and laying the reinforcing ribs in a mold for positioning; the dry fibers forming the skin are laid on the surfaces of the reinforcing ribs; the mold is closed; injecting epoxy resin; curing the mold in a drying oven; burrs are removed; the skin structure is manufactured by adopting the skin structure manufacturing method; the unmanned aerial vehicle adopts the skin structure manufactured by the manufacturing method of the lifting skin structure, so that the rigidity is improved, the manufacturing period is shortened, and the unmanned aerial vehicle is suitable for batch production.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) design and manufacturing technology, and in particular to a method for manufacturing a skin structure, the skin structure, and the UAV. Background Technology

[0002] As an important part of the low-altitude economy, drones are developing faster and faster, and their application scenarios are becoming wider and wider, from emergency rescue and disaster relief to agricultural and forestry plant protection and marine salvage. In order to achieve the above functions, drones are generally equipped with various payload devices, requiring drones to be lighter and have higher structural strength.

[0003] Currently, drone skins use foam or honeycomb sandwich structures. These skins have poor design flexibility, low structural rigidity, and long manufacturing cycles, making them unsuitable for mass production of drones. Summary of the Invention

[0004] The purpose of this invention is to provide a method for manufacturing a skin structure, a skin structure, and an unmanned aerial vehicle (UAV), which improves the designability and rigidity of the skin structure, shortens the manufacturing cycle, and is suitable for mass production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] One aspect provides a method for manufacturing a skin structure, the skin structure comprising a skin and reinforcing ribs, the reinforcing ribs being arranged in a crisscross pattern, the skin covering the reinforcing ribs, and the method for manufacturing the skin structure comprising the following steps:

[0007] The thickness of the skin and the equivalent height of the reinforcing ribs are determined based on the preset shear stress of the skin structure.

[0008] The size and distribution of the reinforcing ribs are determined based on the pre-set buckling stress of the skin structure;

[0009] The reinforcing ribs are formed by pultrusion.

[0010] Cut the reinforcing ribs and place them in the mold for positioning;

[0011] The dry fibers forming the skin are laid onto the surface of the reinforcing ribs;

[0012] The mold is closed;

[0013] Inject epoxy resin;

[0014] The mold is placed in an oven for curing;

[0015] Remove burrs.

[0016] In some embodiments, the thickness of the skin, the equivalent height of the reinforcing ribs, the distribution spacing L of the reinforcing ribs, and the cross-sectional dimensions of the reinforcing ribs are determined through iterative optimization.

[0017] In some embodiments, according to The thickness δ of the skin and the equivalent height H of the reinforcing rib are determined through iterative processes, wherein... Q is the preset shear stress; Q is the shear force.

[0018] according to The distribution spacing L of the stiffeners and the cross-sectional dimensions of the stiffeners are determined iteratively, where σ is the buckling stress; c is the boundary condition coefficient; E is the elastic modulus; J is the moment of inertia; A is the equivalent area after the stiffeners are laid in the skin structure; and π is a constant.

[0019] In some embodiments, during the pultrusion molding of the reinforcing rib, the slit prepreg yarn is pultruded according to the equivalent height of the reinforcing rib at [0]. N The layers are laid up and shaped using a pultrusion die;

[0020] And / or, the reinforcing rib is made of carbon fiber unidirectional tape.

[0021] In some embodiments, the reinforcing ribs are positioned in the mold by their own adhesiveness.

[0022] In some embodiments, the dry fibers are laid up according to the thickness of the skin, and the shear load of the skin is... ,in, , This is the allowable shear strength value of the dry fiber;

[0023] And / or the skin is provided with an opening, which is reserved during the laying of the dry fibers of the skin.

[0024] In some embodiments, the epoxy resin content in the skin structure is 36% ± 2%.

[0025] In some embodiments, when the mold is placed in the oven for curing, the curing temperature is 115℃~125℃ and the curing time is 1.5h~2.5h;

[0026] And / or, when the mold is closed, the closing pressure is 4MPa to 6MPa.

[0027] On the other hand, a skin structure is also provided, which is manufactured according to the skin structure manufacturing method described above.

[0028] Another aspect is the provision of a drone, which employs the skin structure described above.

[0029] The beneficial effects of this invention are:

[0030] By adopting the above manufacturing steps, the thickness of the skin and the equivalent height of the reinforcing ribs are first determined by the preset shear stress, and the structure of the skin and reinforcing ribs is optimized. Then, the mesh layout of the reinforcing ribs is optimized by the preset buckling stress of the skin structure, which improves the overall structural designability, makes the distribution of the reinforcing ribs more reasonable, reduces the structural weight to the maximum extent, and improves the overall structural efficiency. Moreover, the above manufacturing steps adopt one-piece curing molding, which significantly shortens the manufacturing cycle and reduces the production cost, making it very suitable for the mass production of UAVs. Attached Figure Description

[0031] Figure 1 This is a flowchart of the skin structure manufacturing method described in the embodiments of the present invention;

[0032] Figure 2 This is a schematic diagram of the skin structure described in an embodiment of the present invention.

[0033] In the picture:

[0034] 1. Skin; 2. Reinforcing ribs; 3. Openings. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, the present invention provides a method for manufacturing a skin structure, used to produce such a... Figure 2 The illustrated UAV wing skin structure or other skin structure includes a skin 1 and reinforcing ribs 2. The reinforcing ribs 2 include transverse ribs and longitudinal ribs, which are arranged in a crisscross pattern. The skin 1 covers the reinforcing ribs 2, and an opening 3 is provided in the skin 1. The manufacturing method of the skin structure includes the following steps:

[0040] The thickness of skin 1 and the equivalent height of reinforcing rib 2 are determined based on the pre-set shear stress of the skin structure.

[0041] The size and distribution of the stiffener 2 are determined based on the pre-set buckling stress of the skin structure;

[0042] Pultruded reinforcing rib 2;

[0043] Cut the reinforcing rib 2 and place it in the mold for positioning;

[0044] The dry fibers forming the skin 1 are laid onto the surface of the reinforcing rib 2;

[0045] Mold closing;

[0046] Inject epoxy resin;

[0047] The mold is placed in an oven to cure.

[0048] Remove burrs.

[0049] By adopting the above manufacturing steps, the thickness of the skin 1 and the equivalent height of the reinforcing rib 2 are first determined by the preset shear stress, the structure of the skin 1 and the reinforcing rib 2 are optimized, and the mesh layout of the reinforcing rib 2 is optimized by the preset buckling stress of the skin structure, thereby improving the overall structural designability, making the distribution of the reinforcing rib 2 more reasonable, minimizing the weight of the skin structure, and improving the overall structural efficiency. Furthermore, the above manufacturing steps adopt one-piece curing molding, which significantly shortens the manufacturing cycle and reduces production costs, making it very suitable for the mass production of UAVs.

[0050] It should be noted that the preset shear stress and preset buckling stress of the skin structure are effective load data given by aerodynamic experiments. These are data that can be obtained by those skilled in the art, and will not be elaborated further.

[0051] The thickness of the skin 1, the equivalent height of the reinforcing rib 2, the distribution spacing L of the reinforcing rib 2, and the cross-sectional dimensions of the reinforcing rib 2 are determined through iterative optimization.

[0052] Specifically, when determining the thickness of the skin 1 and the equivalent height of the reinforcing rib 2, it can be based on... The thickness δ of skin 1 and the equivalent height H of reinforcing rib 2 are determined iteratively, where, denoted as σ1, where σ1 is the shear stress; Q is the shear force.

[0053] Based on determining the equivalent height H of stiffener 2, it can be determined according to... The distribution spacing L and cross-sectional dimensions of stiffener 2 are determined iteratively. In the above formula, σ is the buckling stress; c is the boundary condition coefficient; E is the elastic modulus; J is the moment of inertia; π is a constant; and A is the equivalent area of ​​stiffener 2 after iterative application in the skin structure. This ultimately determines the distribution and dimensions of stiffener 2. Adjusting the cross-sectional dimensions of stiffener 2 directly changes the moment of inertia J and the equivalent area A of stiffener 2 after iterative application in the skin structure. By adjusting these dimensions and distribution positions, the buckling critical stress σ is determined to meet the stability requirements. It is understandable that since the main function of the transverse stiffeners is to provide support points for the longitudinal stiffeners and significantly reduce the effective width of the compression surface of the skin 1, thus directly determining the buckling critical stress, the distribution spacing L of stiffener 2 refers to the spacing of the transverse stiffeners.

[0054] The specific iterative operations described above can be performed in software such as finite element software, and will not be elaborated on in detail.

[0055] In the pultrusion molding and reinforcing rib 2 cutting steps, the slit prepreg yarn is cut according to the equivalent height of the reinforcing rib 2 at [0]. NThe process involves layering, forming and shearing using a pultrusion die, thereby converting the equivalent height into the number of ply layers (N). The plying is then strictly controlled in the 0° direction through the pultrusion process, resulting in a reinforcing rib 2 with predictable performance and precise dimensions. In this embodiment, the reinforcing rib 2 is manufactured using unidirectional carbon fiber tape. This leverages the stable properties of unidirectional materials, facilitating the calculation of the equivalent height H and achieving the desired stiffness with minimal material usage.

[0056] After determining the position of the reinforcing rib 2, the reinforcing rib 2 formed by the pultrusion die can be cut, then laid in the positioning groove of the die for positioning, and compacted with a pressure plate.

[0057] It should be noted that before placing the reinforcing rib 2, a release agent needs to be applied to the surface of the mold to facilitate subsequent demolding.

[0058] In some embodiments, the reinforcing rib 2 is positioned in the mold by its own adhesiveness, meaning that the positioning of the reinforcing rib 2 does not depend on external tools. This positioning process is efficient and low-cost, and it also reduces positioning time and shortens the manufacturing cycle, making it suitable for mass production. It should be noted that the adhesiveness of the reinforcing rib 2 originates from the prepreg yarn.

[0059] After determining the thickness δ of skin 1, dry fibers are laid up onto the surface of reinforcing rib 2 according to the thickness of skin 1, and the shear load of skin 1 is... ,in, , The allowable shear strength value of the dry fibers is used to ensure that the actual shear stress borne by the skin 1 is less than or equal to the maximum allowable shear stress of its molding material, thus meeting the safety requirements of the structure and preventing shear failure. In the current embodiment, the bonding between each layer of dry fibers is positioned using a setting agent, and the setting agent is not specifically limited.

[0060] In some embodiments, the opening 3 on the skin 1 can be reserved during the dry fiber layup, thus eliminating the need for a subsequent step of setting the opening 3.

[0061] After completing the above layup, the mold is closed, and epoxy resin is injected into the mold under pressure. The epoxy resin content in the skin structure is 36% ± 2%, for example, 35%, 36%, or 37%. Too high an epoxy resin content will lead to a decrease in the stiffness and strength of the skin structure, while too low a content will cause delamination and damage to the skin structure.

[0062] After the epoxy resin is injected, maintain the mold closing pressure and place the mold in an oven for curing. The curing temperature is 115℃~125℃ and the curing time is 1.5h~2.5h. The specific parameters can be adjusted according to the specific situation and are not subject to specific restrictions.

[0063] Once cured, remove it from the mold and remove the burrs. The process of removing burrs will not be described in detail here.

[0064] The following is a brief example:

[0065] Taking the wing as an example, the skin 1 is made of high-strength T700 carbon fiber fabric with a surface density of 200g / m2, the reinforcing rib 2 is made of T700 carbon fiber unidirectional tape with a single layer thickness of 0.15mm, and the opening 3 has dimensions of 330×300mm, 280×250mm, 250×180mm, and 500×360mm.

[0066] according to The thickness δ of skin 1 was determined to be 0.8 mm, and the height of reinforcing rib 2 was determined to be 8 mm, based on the iteration. The width of reinforcing rib 2 is determined to be 10mm, the spacing between transverse ribs is 200-300mm, there are 2 main longitudinal ribs and 6 main transverse ribs, and other auxiliary reinforcing ribs are arranged to meet the spacing requirements of the transverse ribs.

[0067] When using T700 carbon fiber unidirectional tape to make reinforcing rib 2, the prepreg is cut into 10mm wide prepreg yarns using a slitting machine, with a quantity of 14 rolls and a length of 200m per roll.

[0068] The slit prepreg yarns, with a single layer thickness of 0.15 mm, were ply-laid into 14 rolls using a pultrusion die. [0] 14 The pultrusion speed is controlled at 0.5 m / min, the temperature is controlled at 50-60℃, and the dimensions of reinforcing rib 2 are controlled within the range of height 7.8±0.2 mm and width 9.8±0.2 mm. The length is cut according to the structural length of reinforcing rib 2, for example, cut into 2000 mm, 1000 mm, 500 mm, and 300 mm respectively;

[0069] Apply a release agent to the mold surface;

[0070] The reinforcing rib 2 is positioned in the mold groove by the adhesiveness of its own resin and compacted with a pressure plate. Then, the dry fiber material forming the skin 1 is laid on the reinforcing rib 2 according to the requirements of [(±45)(0 / 90)(0 / 90)(±45)]. The bonding between the dry fibers is positioned by a setting agent.

[0071] After the layup is completed, the mold is closed, and 0.46 kg of epoxy resin is injected into the mold under a pressure of 2 MPa, with the epoxy resin content controlled at 36% ± 2%.

[0072] After the epoxy resin is injected, keep the mold locked and maintain a constant pressure of 5MPa. Place the mold in an oven and cure at 120℃ for 2 hours.

[0073] After curing, remove the burrs.

[0074] This application also provides a skin structure manufactured using the above-described skin structure manufacturing method, which improves the designability and rigidity of the skin structure, shortens the manufacturing cycle, and is suitable for mass production.

[0075] This application also provides a drone whose skin structure is manufactured using the above-described lifting skin structure manufacturing method, which increases rigidity, shortens the manufacturing cycle, and is suitable for mass production.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a skin structure, characterized in that, The skin structure includes a skin (1) and reinforcing ribs (2), the reinforcing ribs (2) are arranged in a crisscross pattern, the skin (1) covers the reinforcing ribs (2), and the manufacturing method of the skin structure includes the following steps: The thickness of the skin (1) and the equivalent height of the reinforcing rib (2) are determined according to the pre-set shear stress of the skin structure. The size and distribution of the reinforcing ribs (2) are determined according to the pre-set buckling stress of the skin structure; The reinforcing rib (2) is formed by pultrusion. Cut the reinforcing rib (2) and place it in the mold for positioning; The dry fibers forming the skin (1) are laid on the surface of the reinforcing rib (2); The mold is closed; Inject epoxy resin; The mold is placed in an oven for curing; Remove burrs.

2. The method for manufacturing a skin structure according to claim 1, characterized in that, The thickness of the skin (1), the equivalent height of the reinforcing rib (2), the distribution spacing L of the reinforcing rib (2), and the cross-sectional dimensions of the reinforcing rib (2) are determined through iterative optimization.

3. The method for manufacturing a skin structure according to claim 1, characterized in that, according to The thickness δ of the skin (1) and the equivalent height H of the reinforcing rib (2) are determined iteratively, wherein Q is the preset shear stress; Q is the shear force. according to The distribution spacing L of the stiffener (2) and the cross-sectional dimensions of the stiffener (2) are determined iteratively, where σ is the buckling stress; c is the boundary condition coefficient; E is the elastic modulus; J is the moment of inertia; A is the equivalent area of ​​the stiffener (2) after being laid in the skin structure; and π is a constant.

4. The method for manufacturing a skin structure according to claim 1, characterized in that, In the step of pultruding the reinforcing rib (2), the slit prepreg yarn is pultruded according to the equivalent height of the reinforcing rib (2) at [0]. N The layers are laid up and shaped using a pultrusion die; And / or, the reinforcing rib (2) is made of carbon fiber unidirectional tape.

5. The method for manufacturing a skin structure according to claim 3, characterized in that, The reinforcing rib (2) is positioned in the mold by its own adhesiveness.

6. The method for manufacturing a skin structure according to claim 1, characterized in that, The dry fibers are laid up according to the thickness of the skin (1), and the shear load of the skin (1) is ,in, ; This is the allowable shear strength value of the dry fiber; And / or the skin (1) is provided with an opening (3), which is reserved when the dry fibers of the skin (1) are laid.

7. The method for manufacturing a skin structure according to claim 1, characterized in that, The epoxy resin content in the skin structure is 36% ± 2%.

8. The method for manufacturing a skin structure according to claim 1, characterized in that, When the mold is placed in the oven for curing, the curing temperature is 115℃~125℃ and the curing time is 1.5h~2.5h. And / or, when the mold is closed, the closing pressure is 4MPa to 6MPa.

9. A skin structure, characterized in that, The skin structure is manufactured according to the skin structure manufacturing method as described in any one of claims 1-8.

10. An unmanned aerial vehicle (UAV), characterized in that, The drone employs the skin structure as described in claim 9.

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