Curved pipe for large unmanned aerial vehicles and method for manufacturing the same

Abstract

To provide a bent tube for a large unmanned aerial vehicle, which satisfies a condition that a strength of a braided structure is not easily biased between an inside and outside of a bent shape.SOLUTION: A bent tube 1 used as a component of a large unmanned aerial vehicle is formed by combining a braided thread 71 and an axial thread 72, and has a braided structure with a circular cross section. In an inner circumference of a bent part 11 of the bent tube 1, a value of an inner cover factor cf3 (in), which indicates a ratio of a surface area of the braided structure occupied by the braided thread 71 and the axial thread 72, is 100% or less and 80% or more. In an outer circumference of the bent part 11 of the bent tube 1, a value of an outer cover factor cf3(out), which indicates a ratio of a surface area of the braided structure occupied by the braided thread 71 and the axial thread 72, is 100% or less and 80% or more. An axial thread ratio Rm satisfies a condition Rm≥0.50.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a braided bent pipe for large unmanned aerial vehicles, a method for manufacturing the same, and a method for calculating and controlling a cover factor value.

Background Art

[0002] Next-generation mobility such as large drones (large unmanned aerial vehicles) and flying cars are composed of components such as main body frames, propellers, propeller guards, arms, and skids (legs) (for example, Patent Document 5). Carbon fiber reinforced plastics are often used for these components to reduce weight (for example, Patent Documents 1 to 4). Also, bent pipes are used in many components.

[0003] Bent pipes formed of carbon fiber reinforced plastic are usually formed by sheet winding methods or filament winding methods, but it is difficult to form large bent pipes, and manufacturing by hand lay-up methods is mainstream.

[0004] However, since the hand lay-up method is a manual process, mass production is difficult. In this regard, the braiding method using braiding technology can achieve stable quality because there are no seams on the surface, and is easily applicable to the bent shape of bent pipes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0006] When forming a curved tube using this type of braiding technique, the braided threads must be braided in a curved shape. However, compared to braiding the yarn in a straight line, the yarn shrinks on the inner circumference of the curved shape, while it stretches on the outer circumference. This causes an unevenness (difference in strength) in the braided structure of the curved tube, making it difficult to achieve uniformity. Various factors influence the process, making it difficult to optimize the conditions.

[0007] Therefore, the object of the present invention is to provide a curved pipe for large unmanned aerial vehicles that satisfies the condition that unevenness in the strength of the braided structure is less likely to occur between the inside and outside of the curved shape. [Means for solving the problem]

[0008] The present invention relates to a curved pipe used as a component of a large unmanned aerial vehicle, The curved tube is formed by combining braided threads and shaft threads, and has a braided structure with a circular cross-section. The braided structure is such that the axial threads are incorporated along the central axis direction of the curved tube. The width of the aforementioned braided yarn is b f [mm] The number of the aforementioned braided threads is n [threads] The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis of the curved tube is θ[°] The width of each cell in the braided structure of the curved pipe is f [mm]. The width of the aforementioned axial thread is b m [mm] The number of the aforementioned axial threads is n m [Book] The fineness of the braided yarn is f b [dtex] The fineness of the aforementioned axial yarn is f m [dtex] The tensile modulus of the braided yarn is Eb [GPa] where E is the tensile modulus of elasticity of the axial yarn m [GPa] when determined by the following (Formula 1), the value of the inner cover factor cf3(in), which indicates the proportion of the braiding yarns and the axial yarns occupying the surface area of said braided structure corresponding to the inner circumference of the bent portion of the bent pipe, is not less than 80% and not more than 100%, and the value of the outer cover factor cf3(out), which indicates the proportion of the braiding yarns and the axial yarns occupying the surface area of said braided structure corresponding to the outer circumference of the bent portion of the bent pipe, determined by the following (Formula 1), is not less than 80% and not more than 100%, further, the axial yarn ratio R defined by the following (Formula 2) m satisfies m ≧ 0.50.

Math

Math

[0009] As in the above configuration, in a bent pipe formed by combining braiding yarns and axial yarns and having a circular cross-section braided structure, the value of the inner cover factor cf3(in) at the inner circumference of the bent portion of the bent pipe and the value of the outer cover factor cf3(out) at the outer circumference of the bent portion of the bent pipe satisfy the above conditions, and further, when the axial yarn ratio R m m ≧ 0.50 is satisfied, it is possible to obtain a configuration in which deviation in strength (difference in strength) of the braided structure between the inner side and the outer side of the bent pipe is less likely to occur. In addition, it enables the design of a bent structure in which deviation in strength of the braided structure between the inner side and the outer side of the bent pipe is less likely to occur, and weight reduction can be achieved by reducing the number of joints of structural components of a large unmanned aerial vehicle (for a large drone, such as main body frame, propeller, propeller guard, arm, skid, etc.) and thus reducing the number of parts. ​Furthermore, it becomes possible to change the components of large unmanned aerial vehicles from the commonly used aluminum to carbon fiber reinforced plastic, resulting in weight reduction, increased rigidity, and superior vibration damping.

[0010] Furthermore, the present invention may also be characterized in that, in the curved tube for a large unmanned aerial vehicle having a braided structure formed by combining braided threads, the braided threads have a rectangular cross-section in the shape of a tape.

[0011] According to the above configuration, the value of the inner cover factor on the inner circumference of the bent portion of the curved pipe and the value of the outer cover factor on the outer circumference of the bent portion of the curved pipe can be increased, making it possible to create a configuration in which unevenness (difference in strength) in the strength of the braided structure is less likely to occur between the inside and outside of the curved pipe.

[0012] Furthermore, the present invention relates to a method for manufacturing a curved tube used as a component of a large unmanned aerial vehicle, which has a braided structure with a circular cross-section formed by combining braided threads and shaft threads. The curved pipe in question is, The width of the aforementioned braided yarn is b f [mm] The number of the aforementioned braided threads is n [threads] The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis of the curved tube is θ[°] The width of each cell in the braided structure of the curved pipe is f [mm]. The width of the aforementioned axial thread is b m [mm] The number of the aforementioned axial threads is n m [Book] The fineness of the braided yarn is f b [dtex] The fineness of the aforementioned axial yarn is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the aforementioned axial thread is E m[GPa] In this case, the value of the inner cover factor cf3(in), which indicates the ratio of the braided yarn and the shaft yarn to the surface area of ​​the braided structure corresponding to the inner circumference of the bent portion of the bent tube, as calculated by the following (Equation 3), is 100% or less and 80% or more, and the value of the outer cover factor cf3(out), which indicates the ratio of the braided yarn and the shaft yarn to the surface area of ​​the braided structure corresponding to the outer circumference of the bent portion of the bent tube, as calculated by the following (Equation 3), is 100% or less and 80% or more, Furthermore, the axial filament ratio R is defined below (Equation 4). m However, R m The structure is characterized by arranging the axial threads along the central axis direction of the curved tube on the outer circumference of the mandrel so as to satisfy the condition ≥ 0.50, and by combining the braided threads and the axial threads.

number

number

[0013] In a curved tube formed by combining braided yarns and axle yarns, having a braided structure with a circular cross-section, the value of the inner cover factor cf3(in) of the inner circumference of the bent portion of the curved tube and the value of the outer cover factor cf3(out) of the outer circumference of the bent portion of the curved tube satisfy the above conditions, and furthermore, the axle yarn ratio R m R m If the condition of ≥0.50 is met, it is possible to manufacture a bent pipe with a braided structure that is less likely to have a bias (difference in strength) in terms of the strength of the braided structure between the inside and outside of the bent pipe.

[0014] Furthermore, the present invention relates to a method for calculating and controlling the cover factor cf3 of a curved tube for a large unmanned aerial vehicle, which is formed by combining braided yarn and axial yarn arranged along the central axis direction of the curved tube, and has a braided structure with a circular cross-section, and is used as a component of a large unmanned aerial vehicle, the proportion that the braided yarn and axial yarn occupy to the surface area of ​​the braided structure, (1A) Width b of the braided yarn f [mm], n [number of strands] of the braided threads, D [mm] of the braided structure, θ [°] of the orientation angle of the braided threads with respect to the central axis of the bent tube, f [mm] of the width per cell of the braided structure of the bent tube, and b [mm] of the axis thread. m [mm], the number of the aforementioned axial threads is n m Steps to store [the book] in a memory device, (1B) The width b of the braided yarn stored in step (1A) is given in the following equation (5). f [mm], n [number of strands] of the braided threads, D [mm] of the braided structure, θ [°] of the orientation angle of the braided threads with respect to the central axis of the bent tube, f [mm] of the width per cell of the braided structure of the bent tube, and b [mm] of the axis thread. m [mm], the number of the aforementioned axial threads n m Substitute [Book] and calculate the value of the cover factor cf3, (1C) A step to output the value of the cover factor cf3 calculated in step (1B) above, This is executed by the control device.

number

[0015] According to the above method, in a three-dimensional curved tube formed by combining braided yarn and shaft yarn, and having a braided structure with a circular cross-section, the values ​​of the inner cover factor cf3(in) of the inner circumference of the curved portion of the curved tube and the outer cover factor cf3(out) of the outer circumference of the curved portion of the curved tube are used as indicators to create a structure that is less likely to have uneven strength (difference in strength) in the braided structure between the inside and outside of the curved tube, and the width of the braided yarn b f[mm], n [number of strands] of braided yarn, D [mm] inner diameter of braided structure, θ [°] orientation angle of the braided yarn with respect to the central axis of the curved tube, f [mm] width of one cell of the braided structure of the curved tube, b width of the axis yarn m [mm] and the number of axial threads n m Based on 2D data such as [books], it is possible to calculate a value that approximates the calculated value obtained based on 3D data. [Effects of the Invention]

[0016] We can provide curved pipes for large unmanned aerial vehicles that satisfy the conditions for minimizing unevenness in the strength of the braided structure between the inside and outside of the curved shape. [Brief explanation of the drawing]

[0017] [Figure 1] This is an explanatory diagram of a curved pipe according to this embodiment. [Figure 2] This is an explanatory diagram of the manufacturing method for a curved pipe according to this embodiment. [Figure 3] This is an explanatory diagram of the braided structure (1 cell) of the curved pipe according to this embodiment. [Figure 4] This is an explanatory diagram of the orientation angle of the curved pipe according to this embodiment. [Figure 5] This is a diagram illustrating a mandrel. [Figure 6] This is an explanatory diagram of the bent section of a curved pipe. [Figure 7] This is a schematic diagram illustrating the shape of the braided yarn and the core yarn. [Figure 8] This is an explanatory diagram comparing the two-dimensional area of ​​a braided structure of a curved pipe with the three-dimensional torus shape area. [Figure 9] This is an explanatory diagram comparing the two-dimensional area of ​​a braided structure of a curved pipe with the three-dimensional torus shape area. [Figure 10] This is an explanatory diagram of a large drone using a curved pipe according to this embodiment. [Figure 11] This graph shows the relationship between the orientation angle and the cover factor value in Example A. [Figure 12]This graph shows the relationship between the orientation angle and the cover factor value in Example B. [Figure 13] This graph shows the relationship between the orientation angle and the cover factor value in Example C. [Figure 14] This is an explanatory diagram of the mandrel used in the manufacture of the curved pipe in Example 1. [Figure 15] (A) This is an explanatory diagram for the manufacturing method of the curved pipe (straight section) according to the examples and comparative examples. (B) This is an explanatory diagram for the manufacturing method of the curved pipe (bent section) according to the examples and comparative examples. [Figure 16] This is an explanatory diagram of the inner and outer sides of the central portion of the bent section of the curved pipe according to the examples and comparative examples. [Figure 17] This is an explanatory diagram of the destructive test of a curved pipe according to the examples and comparative examples. [Modes for carrying out the invention]

[0018] (Embodiment) Embodiments of the present invention will be described below with reference to the drawings. The curved pipe 1 of this embodiment is used as a component of a large drone 100 (equivalent to a large unmanned aerial vehicle) that transports cargo unmanned, as shown in Figure 10. For example, the curved pipe 1 is used in the main frame 101 (which forms the space for storing the cargo to be transported), propeller 102, propeller guard 103, arm 104, and skid 105 (legs) that make up the large drone 100. The main frame 101, propeller 102, propeller guard 103, arm 104, and skid 105 that make up the large drone 100 have bent portions in their shape and are required to be lightweight, highly rigid, and have excellent vibration damping properties.

[0019] In this embodiment, a large drone 100 is used as an example to describe a large unmanned aerial vehicle, but a large unmanned aerial vehicle is assumed to be one in which the distance between the axes of the propellers 102 is 1000 mm or more.

[0020] (Bent pipe 1) The curved tube 1 is a tube made of fiber-reinforced plastic (FRP) constructed by a braided structure using braided threads (such as carbon fiber material) and resin molding. As shown in Figure 1, the curved tube 1 has a circular cross-section and is bent at a certain bending angle. For example, when the curved tube 1 of this embodiment is used in the propeller guard 103 or skid 105 (legs) of a large drone 100, it has a bent shape at a certain bending angle, as shown in Figure 1.

[0021] As shown in Figure 3, the braided structure of the curved tube 1 is formed by combining multiple braided threads 71 ​​and axle threads 72 with each other. As shown in Figure 3, the braided threads 71 ​​intersect with the central axis direction of the curved tube 1 at a predetermined orientation angle θ[°]. Furthermore, the axle threads 72 are incorporated into the multiple braided threads 71 ​​so as to be parallel to the central axis direction of the curved tube 1, for the purpose of improving the strength in the central axis direction of the curved tube 1.

[0022] The braided yarn 71 and the shaft yarn 72 serve as reinforcing members for the curved tube 1, and therefore high-strength materials are used. Specifically, examples include carbon fiber, aramid fiber, glass fiber, basalt fiber, boron fiber, and silicon carbide (SiC) fiber, and are not particularly limited as long as they are known to be high-strength fibers. Furthermore, from the viewpoint of maintaining the shape of the braided curved tube 1, nylon, polypropylene, polyethylene terephthalate, polylactic acid, etc. may be used for some of the fibers.

[0023] Any known thermosetting resin can be used as the resin material for resin molding of the braided structure of the curved pipe 1, such as phenolic resin, epoxy resin, and thermosetting polyimide resin.

[0024] (Braided structure of the bent portion of curved pipe 1) When forming a braided curved tube 1, as shown in Figure 1, the braided threads 71 ​​and shaft threads 72 of the curved portion 11 must be braided in a curved shape. However, compared to braiding the braided threads 71 ​​and shaft threads 72 in a straight line, the braided threads 71 ​​and shaft threads 72 contract on the inner circumference side 11A of the curved portion 11, while the braided threads 71 ​​and shaft threads 72 stretch on the outer circumference side 11B of the curved portion 11, which can cause an imbalance (difference in strength) in the braided structure of the curved tube 1. If such an imbalance occurs in the braided structure of the curved tube 1, the rigidity, vibration damping performance, and impact resistance of the curved tube 1 will decrease.

[0025] Therefore, the braided structure of the bent portion of the bent pipe 1 is formed using an index (value) called cover factor cf (Equations 6, 7, and 9), which is an indicator of the strength aspect of the bent pipe 1 having a braided structure with a circular cross-section, and which represents the ratio that the braided yarn 71 (and axis yarn 72) occupies to the surface area of ​​the braided structure of the bent pipe 1. Here, as shown in Figures 1 and 3, the width f [mm] per cell (one section surrounded by the braided yarn 71: see Figure 3(B)) of the braided structure is the same on the inner circumference 11A and outer circumference 11B of the bent portion 11 of the bent tube 1, but the orientation angle θ [°] with respect to the central axis of the bent tube 1 is different. Therefore, it is necessary to calculate the inner cover factor cf(in) of the inner circumference 11A of the bent portion 11 of the bent tube 1, and the outer cover factor cf(out) of the outer circumference 11B of the bent portion 11 of the bent tube 1. Furthermore, in calculating the cover factor cf, it is necessary to consider separately the case where the cells of the braided structure of the curved tube 1 are composed only of braided yarn 71 (cf1) and the case where the cells of the braided structure of the curved tube 1 include both braided yarn 71 and shaft yarn 72 (cf2).

[0026] Specifically, as shown in Figure 3(A), if the cells of the braided structure of the curved tube 1 are composed only of braided yarn 71, then the width b of the braided yarn 71 is... fBased on two-dimensional data such as the diameter [mm], the number of braided threads 71 ​​n [threads], the inner diameter D [mm] of the bent tube 1 (braided structure), and the orientation angle θ [°] of the braided threads 71 ​​with respect to the central axis of the bent tube 1, the value of the inner cover factor cf1(in) of the inner circumference side 11A of the bent portion 11 of the bent tube 1, and the value of the outer cover factor cf1(out) of the outer circumference side 11B of the bent portion 11 of the bent tube 1, calculated by the following (Equation 6), are calculated.

[0027]

number

[0028] On the other hand, as shown in Figure 3(B), if the cells of the braided structure of the curved tube 1 include braided yarn 71 and shaft yarn 72, the width b of the braided yarn 71 f [mm], n [number of braided threads], D [mm] inner diameter of the bent tube 1 (braided structure), and θ [°] orientation angle of the braided threads 71 ​​with respect to the central axis of the bent tube 1, in addition, f [mm] width per cell (one section surrounded by braided threads 71: see Figure 3(B)) of the braided structure of the bent tube 1, and b width of the axis thread 72. m [mm], and the number of axial threads 72 n m Based on values ​​derived from two-dimensional data such as [books], the value of the inner cover factor cf2(in) of the inner circumference side 11A of the bent portion 11 of the bent pipe 1, and the value of the outer cover factor cf2(out) of the outer circumference side 11B of the bent portion 11 of the bent pipe 1 are calculated using the following (Equation 7).

[0029]

number

[0030] Here, it is thought that a configuration that is less likely to result in unevenness (differences in strength) in the braided structure between the inside and outside of the curved tube is made possible when the cells of the braided structure of the curved tube 1 include not only the braided yarn 71 but also the axial yarn 72. If the cells of the braided structure of the curved tube 1 include not only the braided yarn 71 but also the axis yarn 72, then the number of braided yarns 71 is n, and the number of axis yarns 72 is n. m [Book], the fineness of braided yarn 71 f b [dtex], core yarn 72 fineness f m [dtex], Tensile modulus of elasticity of braided yarn 71 E b [GPa], Tensile modulus of axial yarn 72 E m Based on values ​​derived from 2D data such as [GPa], the axial fiber ratio R is defined by the following (Equation 8). m However, R m It is preferable that the condition ≥ 0.50 is satisfied.

[0031]

number

[0032] Based on the above, when the braided structure of the curved tube 1 includes braided yarn 71 and axle yarn 72 (see the braided structure of the curved tube 1 in Figure 3), the value of the cover factor cf3 is calculated by considering the cover factor cf1 in a cell where the braided structure of the curved tube 1 is composed only of braided yarn 71, as shown in Figure 3(A), and the cover factor cf2 in a cell where the braided structure of the curved tube 1 is composed of braided yarn 71 and axle yarn 72, as shown in Figure 3(B). The conditions that satisfy the following are met: the value of the inner cover factor cf3(in) calculated by the following equation (9) is within the range of 80% or less and the value of the outer cover factor cf3(out) calculated by the following equation (9) is within the range of 80% or less and the value of the outer cover factor cf3(out) calculated by the following equation (9) are within the range of 80% or less and furthermore, the axle yarn ratio R defined in the above equation (8) m However, R mBy satisfying the condition ≥0.50, the braided structure of the bent portion 11 of the bent pipe 1 is formed in which there is no bias (difference in strength) in terms of the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent pipe 1 (see [Verification based on Examples 1-5 and Comparative Examples 1-5] described later in the examples).

[0033]

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[0034] As described above, the value of the inner cover factor cf(in) is kept within the range of 80% or less and the value of the outer cover factor cf(out) is kept within the range of 80% or less and the value of 100% or less. This is because if the value of the inner cover factor cf(in) or the outer cover factor cf(out) exceeds 100%, it will exceed the surface area of ​​the bent tube 1 formed by the braided structure of the braided yarn 71 (braided yarn 71 and shaft yarn 72), causing a portion of the braided yarn 71 (braided yarn 71 and shaft yarn 72) to float away from the surface of the bent tube 1. This can cause loads to be placed on the floating portion or its surroundings, potentially reducing the rigidity, vibration damping performance, and impact resistance of the bent tube 1. Furthermore, if the value of the inner cover factor cf(in) is less than 80% or the value of the outer cover factor cf(out) is less than 80%, an imbalance (difference in strength) in the braided structure will occur between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent tube 1, potentially reducing the rigidity, vibration damping performance, and impact resistance of the bent tube 1.

[0035] (Shape of the braided yarn 71 and the core yarn 72) Furthermore, when carbon fiber materials (6k, 12k) are used for the braided yarn 71 and the core yarn 72, the fibers are bundles of thin threads, making it unlikely that the cross-section will be a perfect circle (see Figure 7) when forming the braided structure of the curved tube 1. Therefore, it is preferable to make the shape of the fibers of the braided yarn 71 and the core yarn 72 a rectangular tape shape (see Figure 7). This makes it possible to increase the value of the inner cover factor cf(in) on the inner circumference of the bent portion 11 of the curved tube 1, and the value of the outer cover factor cf(out) on the outer circumference of the bent portion 11 of the curved tube 1, thereby making it less likely for there to be a bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved tube.

[0036] (Method for calculating and controlling the cover factor of a curved tube made solely of braided yarn) Prior to fabricating the braided structure of the curved tube 1, the calculation process (calculation control method) for the value of the inner cover factor cf1(in) on the inner circumference side 11A of the bent portion 11 of the curved tube 1, and the value of the outer cover factor cf1(out) on the outer circumference side 11B of the bent portion 11 of the curved tube 1 will be explained, when the braided structure of the curved tube 1 is composed only of braided yarn 71 (when the braided structure of the curved tube 1 does not include the axis yarn 72).

[0037] First, the user inputs the width b of the braided yarn 71, which is assumed by the user, using the input section of the information processing device (a control device such as a personal computer). f The values ​​of various parameters such as the diameter [mm], the number of braided threads 71 ​​n [threads], the inner diameter D [mm] of the bent tube 1, and the orientation angle θ [°] of the braided threads 71 ​​with respect to the central axis direction of the bent tube 1 (the orientation angle θ [°] of the inner circumference side 11A of the bent portion 11 of the bent tube 1, and the orientation angle θ [°] of the outer circumference side 11B of the bent portion 11 of the bent tube 1) are input and stored in the memory unit of the information processing device ((1A) step).

[0038] Next, the user adds the width b of the braided yarn 71, which was stored in the storage unit in step (1A), to the above (Equation 6) stored as a program in the storage device of the information processing device. fSubstitute the values ​​of various parameters such as [mm], n [strands] of the braided threads 71, D [mm] of the bent tube 1, and θ [°] of the braided threads 71 ​​with respect to the central axis direction of the bent tube 1 (θ [°] of the orientation angle of the inner circumference side 11A of the bent portion 11 of the bent tube 1, and θ [°] of the orientation angle of the outer circumference side 11B of the bent portion 11 of the bent tube 1), and calculate the value of the inner cover factor cf1(in) of the inner circumference side 11A of the bent portion 11 of the bent tube 1, and the value of the outer cover factor cf1(out) of the outer circumference side 11B of the bent portion 11 of the bent tube 1 ((1B) step).

[0039] Then, the values ​​of the inner cover factor cf1(in) and the outer cover factor cf1(out) calculated in step (1B) above are displayed on a display connected to the information processing device (step (1C)).

[0040] Thus, if the value of the inner cover factor cf1(in) displayed on the screen satisfies the condition of being between 100% and 80%, and the value of the outer cover factor cf1(out) satisfies the condition of being between 100% and 80%, then the various parameters assumed by the user are estimated to be values ​​that do not result in a bias (difference in strength) in terms of the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent pipe 1, and these are set as the design values ​​(specifications) for the braided structure of the bent pipe 1. On the other hand, if the value of the inner cover factor cf1(in) does not satisfy the condition of being between 80% and 100%, or if the value of the outer cover factor cf1(out) does not satisfy the condition of being between 80% and 100%, then the various parameters assumed by the user are estimated to be values ​​that cause a bias (difference in strength) in the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent pipe 1. The values ​​of the various parameters are then changed, and the process of steps (1A) to (1C) above is executed again.

[0041] According to the above method, in a curved tube 1 formed by combining braided yarns 71 and having a braided structure with a circular cross-section, the values ​​of the inner cover factor cf1(in) of the inner circumference 11A of the bent portion 11 of the curved tube 1 and the outer cover factor cf1(out) of the outer circumference 11B of the bent portion 11 of the curved tube 1 are used as indicators to ensure that there is little bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved tube 1, and the width b of the braided yarns 71. f Based on two-dimensional data such as [mm], the number of braided threads 71 ​​n [threads], the inner diameter D of the braided structure D [mm], and the orientation angle θ [°] of the braided threads 71 ​​with respect to the central axis of the curved tube 1, a value can be calculated that approximates the calculated value obtained based on three-dimensional data.

[0042] (Method for calculating and controlling the cover factor of a curved tube including braided yarn and shaft yarn) Next, we will explain the calculation process (calculation control method) for the value of the inner cover factor cf3(in) on the inner circumference side 11A of the bent portion 1, and the value of the outer cover factor cf3(out) on the outer circumference side 11B of the bent portion 11 of the bent portion 11 of the bent portion 1 of the bent portion 1 of the bent portion 1, when the braided structure of the bent tube 1 includes braided yarn 71 and shaft yarn 72 (see braided structure of the bent tube 1 in Figure 3).

[0043] First, the user inputs the width b of the braided yarn 71, which is assumed by the user, using the input section of the information processing device (a control device such as a personal computer). f [mm], n [number of strands] of braided yarn 71, D [mm] inner diameter of bent tube 1, θ [°] orientation angle of braided yarn 71 with respect to the central axis direction of bent tube 1 (θ [°] orientation angle of the inner circumference side 11A of the bent portion 11 of bent tube 1, and θ [°] orientation angle of the outer circumference side 11B of the bent portion 11 of bent tube 1), f [mm] width per cell of the braided structure of bent tube 1, b width of axis yarn 72 m [mm], and the number of axial threads 72 n m The values ​​of various parameters of [Book] are entered and stored in the memory unit of the information processing device (Step (2A)).

[0044] Next, the user adds the width b of the braided yarn 71, which was stored in the storage unit in step (2A), to the above (Equation 9) stored as a program in the storage device of the information processing device. f [mm], n [number of strands] of braided yarn 71, D [mm] inner diameter of bent tube 1, θ [°] orientation angle of braided yarn 71 with respect to the central axis direction of bent tube 1 (θ [°] orientation angle of the inner circumference side 11A of the bent portion 11 of bent tube 1, and θ [°] orientation angle of the outer circumference side 11B of the bent portion 11 of bent tube 1), f [mm] width per cell of the braided structure of bent tube 1, b width of axis yarn 72 m [mm], and the number of axial threads 72 n m Substitute the values ​​of the various parameters in [Book] to calculate the value of the inner cover factor cf3(in) of the inner circumference side 11A of the bent portion 11 of the bent pipe 1, and the value of the outer cover factor cf3(out) of the outer circumference side 11B of the bent portion 11 of the bent pipe 1 ((2B) step).

[0045] Then, the values ​​of the inner cover factor cf3(in) and the outer cover factor cf3(out) calculated in step (2B) above are displayed on a display connected to the information processing device (step (2C)).

[0046] Thus, if the value of the inner cover factor cf3(in) displayed on the screen satisfies the condition of being between 100% and 80%, and the value of the outer cover factor cf3(out) satisfies the condition of being between 100% and 80%, then the various parameters assumed by the user are estimated to be values ​​that do not result in an imbalance (difference in strength) in terms of the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent pipe 1, and these are set as the design values ​​(specifications) for the braided structure of the bent pipe 1. On the other hand, if the value of the inner cover factor cf3(in) does not satisfy the condition of being between 100% and 80%, or if the value of the outer cover factor cf3(out) does not satisfy the condition of being between 100% and 80%, then the various parameters assumed by the user are estimated to be values ​​that cause a bias (difference in strength) in terms of the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent pipe 1. The values ​​of the various parameters are then changed, and the processing of steps (2A) to (2C) above is executed again.

[0047] According to the above method, in a three-dimensional curved tube 1 formed by combining braided yarn 71 and shaft yarn 72, which has a circular cross-section, the values ​​of the inner cover factor cf3(in) of the inner circumference 11A of the bent portion 11 of the curved tube 1 and the outer cover factor cf3(out) of the outer circumference 11B of the bent portion 11 of the curved tube 1 are used as indicators to ensure that there is little bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved tube 1, and the width b of the braided yarn 71 f [mm], n [number of strands] of braided yarn 71, D [mm] inner diameter of braided structure, θ [°] orientation angle of braided yarn 71 with respect to the central axis of the bent tube 1, f [mm] width per cell of the braided structure of the bent tube 1, b width of axis yarn 72 m [mm], and the number of axial threads 72 n m Based on 2D data such as [books], it is possible to calculate a value that approximates the calculated value obtained based on 3D data.

[0048] (Manufacturing method for curved pipe 1: Braiding process) Next, we will explain the manufacturing method of the curved pipe 1. As shown in Figure 2(A), the braided structure of the curved tube 1 is manufactured using a circular braider 20 (braiding machine). The axial thread 72 is supplied from the bottom of the circular braider 20 through a fixed cylinder 22, and the braided thread 71 is wound around a spindle 21. Furthermore, as shown in Figure 5, a cylindrical mandrel 30 is installed at the center of the circular braider 20, having a bent portion 31 that forms the bent portion 11 of the curved tube 1 to be manufactured, and straight portions 32 and 33 at both ends of the bent portion 31. The braided yarn 71 and shaft yarn 72 are combined on the outer circumference of the upper part of the mandrel 30 to form the braided structure of the curved tube 1. Specifically, as shown in Figure 2(B), the spindle 21 moves along the track 23 while the mandrel 30 is controlled to be pulled out by a robotic arm (not shown) so that the inner surface of the curved tube 1 to be braided on the surface of the mandrel 30 and the circular braider 20 are kept parallel. As a result, the braided yarn 71 and the shaft yarn 72 are combined, and the braided structure of the curved tube 1 is formed on the surface of the mandrel 30. The diameter of the cylindrical mandrel 30 is the same as the inner diameter D of the bent pipe 1 to be braided.

[0049] Here, if the braided structure of the curved tube 1 consists only of braided yarn 71 (i.e., the braided structure of the curved tube 1 does not include the axis yarn 72), the width b of the braided yarn 71. f The values ​​of various parameters such as the diameter [mm], the number of braided threads 71 ​​n [threads], the inner diameter D [mm] of the bent tube 1 (braided structure), and the orientation angle θ [°] of the braided threads 71 ​​with respect to the central axis direction of the bent tube 1 must satisfy the following conditions: the values ​​must not result in a bias (difference in strength) in the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 11 of the bent tube 1, and must be within the range of the inner cover factor cf1(in) of the inner circumference 11A of the bent portion 11 of the bent tube 1 calculated by (Equation 6) above (100% or less and 80% or more), and the values ​​must be within the range of the outer cover factor cf1(out) of the outer circumference 11B of the bent portion 11 of the bent tube 1 calculated by (Equation 6) above (100% or less and 80% or more). In other words, the above parameters must satisfy the condition that the value of the inner cover factor cf1(in), calculated by the above "Method for calculating and controlling the cover factor of a curved tube including braided yarn," is between 100% and 80%, and the value of the outer cover factor cf1(out) is between 100% and 80%.

[0050] Thus, in a curved tube 1 formed by combining braided yarns 71 and having a braided structure with a circular cross-section, if the value of the inner cover factor cf1(in) on the inner circumference side 11A of the bent portion 11 of the curved tube 1 and the value of the outer cover factor cf1(out) on the outer circumference side 11B of the bent portion 11 of the curved tube 1 satisfy the above conditions, then a curved tube 1 can be manufactured that has a braided structure in which unevenness (difference in strength) in terms of the strength of the braided structure is less likely to occur between the inside and outside of the curved tube 1.

[0051] Furthermore, if the braided structure of the curved tube 1 includes braided yarn 71 and shaft yarn 72 (see braided structure of curved tube 1 in Figure 3), the width b of the braided yarn 71. f [mm], n [number of braided threads], D [mm] inner diameter of the bent tube 1 (braided structure), and θ [°] orientation angle of the braided threads 71 ​​with respect to the central axis of the bent tube 1, in addition, f [mm] width per cell (one section surrounded by braided threads 71: see Figure 3(B)) of the braided structure of the bent tube 1, and b width of the axis thread 72. m [mm], and the number of axial threads 72 n m [This] must satisfy the following conditions: there must be no bias (difference in strength) in the strength of the braided structure between the inner circumference 11A and the outer circumference 11B of the bent portion 1 In other words, the above parameters must satisfy the condition that the value of the inner cover factor cf3(in), calculated by the above-mentioned "Method for calculating and controlling the cover factor of a curved tube including braided yarn and shaft yarn," is between 100% and 80%, and the value of the outer cover factor cf3(out) is between 100% and 80%.

[0052] Thus, in a curved tube 1 formed by combining braided yarn 71 and shaft yarn 72, and having a braided structure with a circular cross-section, if the value of the inner cover factor cf3(in) on the inner circumference side 11A of the bent portion 11 of the curved tube 1 and the value of the outer cover factor cf3(out) on the outer circumference side 11B of the bent portion 11 of the curved tube 1 satisfy the above conditions, then a curved tube 1 can be manufactured that has a braided structure in which unevenness (difference in strength) in terms of the strength of the braided structure is less likely to occur between the inside and outside of the curved tube 1.

[0053] The orientation angle θ[°] is calculated as two-dimensional data using the following equation (Equation 10), given the orbital angular velocity ω[rad / s] of the spindle 21, the diameter D[mm] of the mandrel 30, and the take-up speed v[mm / s] of the mandrel 30, as shown in Figure 4.

[0054]

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[0055] Furthermore, as shown in Figure 6, if the radius of the bent pipe 1 is R, the radius of the inner circumference of the bent portion 11 of the bent pipe 1 is R1, the radius of the outer circumference of the bent portion 11 of the bent pipe 1 is R2, the length of the inner arc of the bent portion 11 of the bent pipe 1 is L1, the length of the outer arc of the bent portion 11 of the bent pipe 1 is L2, and the outer diameter of the bent pipe 1 is 2a, then the relationship between the radius and the circumference is given by the following (Equation 11).

[0056]

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[0057]

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[0058]

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[0059] (Manufacturing method for curved pipe 1: Resin molding process) Furthermore, after forming the braided structure of the curved tube 1 on the surface of the mandrel 30, a resin molding treatment is applied to fill the gaps in the braided structure and to enhance rigidity, vibration damping performance, and impact resistance. Examples of such resin molding treatments for the braided structure of the curved tube 1 include impregnating the braided structure of the curved tube 1 with resin components such as phenolic resin, epoxy resin, and thermosetting polyimide resin by heat treatment and curing, or forming the braided structure of the curved tube 1 with braided yarn 71 (and shaft yarn 72) made from fibers (prepreg) that have been previously impregnated with resin components such as phenolic resin, epoxy resin, and thermosetting polyimide resin, and then curing it by heat treatment. Furthermore, the resin molding process is not particularly limited, and known methods can be employed. Examples include RTM (Resin Transfer Molding), VaRTM (Vacuum-Assisted Resin Transfer Molding), autoclave molding, press molding, internal pressure molding, and shrink tape (heat-shrinkable film) molding. Through the above process, a curved pipe 1 made of fiber-reinforced plastic (FRP) is manufactured, consisting of a braided structure and resin molding.

[0060] (Regarding the validity of the cover factor value) In this invention, the braided structure of the bent portion 11 of the bent pipe 1 is formed using a value called the cover factor cf (see Equations 6, 7, and 9), which is an indicator of the strength surface of the bent pipe 1 having a braided structure with a circular cross-section. In the above embodiment, the braided structure of the bent portion 11 of the curved pipe 1 has been formed based on the cell area and cover factor cf in two dimensions. However, in reality, the curved pipe 1 is braided into a three-dimensional torus shape, so it is necessary to consider the cell area and cover factor cf in three dimensions. Therefore, in order to demonstrate that the cover factor cf values ​​calculated using the above (Equations 6), (7), and (9) are valid, we defined the quadrilateral inscribed by each vertex of the cell shown in Figure 8 (the region e × f in Figure 8) as an extended cell, and compared the 2D extended cell area S' with the extended area S on the 3D torus surface when the number of braided threads is n, to investigate how much error occurs.

[0061] As shown in Figure 8, if the width of one cell (one section surrounded by braided yarn 71) of the braided structure on the outer circumference 11B of the bent portion 11 of the curved tube 1 is f, the length is e, and the number of braided yarns is n, then the width f is calculated by the following equation (Equation 14) and the length e is calculated by the following equation (Equation 15), and the two-dimensional expanded area S' is calculated by the following equation (Equation 16).

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[0062] On the other hand, the expanded area S (infinite area) on the three-dimensional torus surface of the curved pipe 1 can be determined from the length of the circumference in the torus direction (rotational direction around the z axis) and the length of the circumference of the torus cross-section (φ direction), as shown in Figure 9. In other words, the infinitesimal area dS (infinite interval) is, Rotation direction around the z-axis: 2π(R+a cosφ)dz Length of the circumference (in the φ direction) of the torus cross-section: adφ (see Figure 9) Therefore, it is calculated by the following (Equation 17).

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[0063] The integration interval (see Figure 9) is as follows: Rotation direction around the z-axis: (-β / 2) → (β / 2) φ direction: (-2π / n)→(2π / n) However, β shown in (Equation 18) represents the ratio of the vertical width of the extended cell to the entire circumference of the torus. Therefore, the expanded area S on the three-dimensional torus surface is calculated by the following equation (Equation 19).

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[0064] The relationship (ratio) between the two-dimensional expanded cell area S' obtained from (Equation 16) above and the three-dimensional expanded area S on the torus surface obtained from (Equation 19) above is S' / S = 1.002, and the error is within 1% when the conditions for the bent tube 1 are, for example, the orientation angle θ2 = 51.4° with respect to the central axis of the bent tube 1, the radius R = 100 mm of the bent tube 1, the radius a = 16 mm of the bent tube 1, and the number of braided threads n = 24. Therefore, the cover factor of a 3D torus shape can be approximated to a 2D shape by considering it to be the same as a linear braid at the moment of braiding.

[0065] As described above, it becomes possible to design a curved structure in which unevenness in the strength of the braided structure is less likely to occur between the inside and outside of the curved pipe 1, and it becomes possible to reduce the weight by reducing the number of joints in the components of a large unmanned aerial vehicle (for a large drone 100, this would be the main frame 101, propeller 102, propeller guard 103, arm 104, skid 105, etc.) and thus reducing the number of parts. Furthermore, it becomes possible to change the components of the large drone 100 from the commonly used aluminum to carbon fiber reinforced plastic, resulting in weight reduction, increased rigidity, and superior vibration damping.

[0066] (Other embodiments) In the above embodiment, we described the case in which the curved pipe 1 is used in the main frame 101, propeller 102, propeller guard 103, arm 104, and skid 105 that constitute a large drone 100, which is a large unmanned aerial vehicle. However, the curved pipe 1 may also be used in a manned aircraft (for example, a large drone-type flying taxi).

[0067] Furthermore, the process for calculating the cover factor performed in the above embodiment may be installed and executed as software (program, data) on an information processing device such as a smartphone or other portable information device, a portable computer or laptop computer, a notebook computer, a tablet PC, a handheld PC, or a PDA (Personal Data Assistant). In this case, the software may be downloaded from a server or the like via communication means and stored in a storage device (flash memory, etc.) within the portable information device. The communication means may be a bidirectional transmission path such as the internet or cable television, or it may be broadcasting that transmits information in only one direction.

[0068] Furthermore, the software that performs the process of calculating the cover factor may be stored on a storage medium such as a CD-ROM, DVD-ROM, MO (magneto-optical disk), hard disk, or flash memory, and may be read from the storage medium as needed and installed in the storage unit of the information processing device.

[0069] Furthermore, the details described in the above embodiment may be implemented as a service performed between an information terminal such as a smartphone or PC (for inputting various parameters) and an information processing device (for calculating the cover factor) via the Internet (communication line).

[0070] Furthermore, the processing performed in the above embodiment may be a program installed on a smartphone or PC. The program may also be stored on a storage medium (MEDIUM).

[0071] Furthermore, the processing performed in the above embodiment may be implemented as a calculation control device that uses an information processing device to calculate the cover factor.

[0072] Although embodiments of the present invention have been described above, these are merely illustrative examples and do not particularly limit the present invention. The specific configurations of each means, etc., can be modified as appropriate. Furthermore, the effects described in the embodiments of the present invention are merely a list of the most preferred effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments. [Examples]

[0073] (Example of calculating the cover factor for a curved pipe) Examples of calculating the cover factor of a curved pipe are shown as Examples A to C.

[0074] (Example A) In Example A, as shown in the graph in Figure 11, the width b of the braided yarn f Assuming [mm] is 2mm, the inner diameter of the bent tube (outer diameter of the mandrel) D[mm] is 26mm, the number of braided threads n[strands] is 32, and the number of axis threads is 0, the radius R of the bent tube was varied to 60mm, 90mm, or 120mm, and the orientation angle θ1[°] on the inner circumference side of the bent portion of the bent tube was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. Note that the orientation angle θ2[°] on the outer circumference of the bent portion of the curved pipe can be calculated using the above (Equations 11) to (Equations 13), and therefore is omitted from Figure 11.

[0075] In Example A, the number of braided threads n is 32, which is fewer than in Examples B (48 threads) and C (64 threads) described later. Therefore, even if the orientation angles θ1 and θ2 are made relatively large, the conditions that the inner cover factor cf(in) is between 100% and 80% and the outer cover factor cf(out) is between 100% and 80% can be met.

[0076] Furthermore, in Example A, when the radius R of the bent pipe is changed to 60 mm, 90 mm, or 120 mm, the larger the radius R of the bent pipe, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out). This shows that the range of orientation angle θ1 and orientation angle θ2 can be set (designed) to be wide enough that the inner cover factor cf(in) satisfies the condition of being between 100% and 80%, and the outer cover factor cf(out) satisfies the condition of being between 100% and 80%.

[0077] (Example B) In Example B, as shown in the graph in Figure 12, the width of the braided yarn b f Assuming [mm] is 2mm, the inner diameter of the bent tube (outer diameter of the mandrel) D[mm] is 26mm, the number of braided threads n[strands] is 48, and the number of axis threads is 0, the radius R of the bent tube was varied to 60mm, 90mm, or 120mm, and the orientation angle θ1[°] on the inner circumference side of the bent portion of the bent tube was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. Note that the orientation angle θ2[°] on the outer circumference of the bent portion of the curved pipe can be calculated using the above (Equations 11) to (Equations 13), and therefore is omitted from Figure 12.

[0078] In Example B, the number of braided threads n is 48, which is fewer than in Example C (64 threads) described later. Therefore, even if the orientation angles θ1 and θ2 are made larger than in Example C, the conditions that the inner cover factor cf(in) is between 100% and 80% and the outer cover factor cf(out) is between 100% and 80% can be met.

[0079] Furthermore, in Example B, when the radius R of the bent pipe is changed to 60 mm, 90 mm, or 120 mm, the larger the radius R of the bent pipe, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out). This shows that the range of orientation angle θ1 and orientation angle θ2 can be set (designed) to be wide enough that the inner cover factor cf(in) satisfies the condition of being between 100% and 80%, and the outer cover factor cf(out) satisfies the condition of being between 100% and 80%.

[0080] (Example C) In Example C, as shown in the graph in Figure 13, the width of the braided yarn b f Assuming a diameter of 2 mm, an inner diameter of the bent tube (outer diameter of the mandrel) D [mm] of 26 mm, a number of braided threads n [strands] of 64, and zero axis threads, the radius R of the bent tube was varied to 60 mm, 90 mm, or 120 mm, and the orientation angle θ1 [°] on the inner circumference side of the bent portion of the bent tube was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. Note that the orientation angle θ2[°] on the outer circumference of the bent portion of the curved pipe can be calculated using the above equations (11) to (13), and therefore is omitted from Figure 13.

[0081] In Example C, the number of braided threads n is 64, which is more than in Examples A (32 threads) and B (48 threads) mentioned above. Therefore, unless the orientation angles θ1 and θ2 are made smaller than in Example A or B, it is not possible to satisfy the condition that the value of the inner cover factor cf(in) is between 100% and 80% and the value of the outer cover factor cf(out) is between 100% and 80%.

[0082] Furthermore, in Example C, when the radius R of the bent pipe is changed to 60 mm, 90 mm, or 120 mm, the larger the radius R of the bent pipe, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out). This shows that the range of orientation angle θ1 and orientation angle θ2 can be set (designed) to be wide enough that the inner cover factor cf(in) satisfies the condition of being between 100% and 80%, and the outer cover factor cf(out) satisfies the condition of being between 100% and 80%.

[0083] [Verification based on Examples 1-5 and Comparative Examples 1-5] In this invention, in a curved tube formed by combining braided yarn and axle yarn, the value of the inner cover factor cf3(in) of the inner circumference of the bent portion of the curved tube is 100% or less and 80% or more, and the value of the outer cover factor cf3(out) of the outer circumference of the bent portion of the curved tube is 100% or less and 80% or more, and the axle yarn ratio R m However, R m By satisfying the condition of ≥0.50, the structure is designed to minimize unevenness (differences in strength) in the braided structure between the inside and outside of the curved pipe.

[0084] Therefore, in this embodiment, curved pipes according to Examples 1 to 5 and Comparative Examples 1 to 5 were manufactured, and the V of the curved pipe was measured. f We conducted measurements of the fiber volume content, the tensile modulus of the bent pipe, and fracture tests on the bent pipe, and then performed comparative verification. The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0085] (Structure of a curved pipe made of fiber-reinforced plastic (FRP)) <Braiding yarn and shaft yarn used in the braided structure of curved tubes> Table 1 lists the carbon fibers 1-3 that make up the braided yarn and shaft yarn used in the braided structure of the curved tube. [Table 1] <Resin composition for use in curved pipes> • Thermosetting resin: Vinyl ester resin (Brand name CBZ500LM-AS, viscosity 200-350 mPa·s, manufactured by Nippon Yupika) • Accelerator: Brand PR-CBZ01 (manufactured by Nippon Yupika) • Hardener: 328E (manufactured by Kayaku Nurion)

[0086] (Manufacturing method for curved pipes) The manufacturing methods for the curved tubes in Examples 1-5 and Comparative Examples 1-5 involved forming the braided structures described in Examples 1-5 and Comparative Examples 1-5 so that they had the axial filament ratio (Rm) and cover factor (cf3) shown in Table 2, and then resin-molding these structures to produce curved tubes made of fiber-reinforced plastic (FRP).

[0087] [Table 2]

[0088] The manufacturing method for curved pipes is described below. 1) A mandrel was fabricated using a 3D printer (Creator3, manufactured by FLASHFORGE) and polylactic acid filament for 3D printers (PLA-F35, manufactured by FLASHFORGE). Mandrels were fabricated by setting the diameter D and radius of curvature R as described in Examples 1-5 and Comparative Examples 1-5 in Table 2, setting the bending angle to 60°, and fixing the length of the straight sections (chuck sections) at both ends to 100 mm. The mandrel of Example 1 is shown in Figure 14.

[0089] 2) Prepare the required number of bobbins for both the braiding threads and the core threads. The carbon fibers to be used as braided yarn and core yarn were wound onto bobbins for the braiding machine using a single-spindle semi-automatic bobbin winder (KUW-100, manufactured by Kokubun Limited).

[0090] 3) The bobbins described above were attached to the braiding carrier (spindle) and the spindle carrier (spindle) of the braiding machine (40Z032C, manufactured by Kokubun Limited).

[0091] 4) The mandrel was attached to the NACHI robot arm (MZ10LF, Fujitsu).

[0092] 5) The braided yarn and shaft yarn were pulled out from the bobbin attached to the carrier and fixed to the starting point of the lamination on the mandrel.

[0093] 6) The straight section of the mandrel was drawn up and braided at the draw speed γ1 calculated using the following formula (Equation 20). During this process, the mandrel (straight section) was held so that its axis in the draw direction was perpendicular to the braiding machine (Figure 15(A)).

[0094]

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[0095] 7) The bent portion of the mandrel was drawn up and braided at the draw speed γ1 calculated using (Equation 20) above. At this time, the braided structure of the bent tube was formed by adjusting the angle with the robot arm so that the axis in the direction of drawing out the mandrel (bent portion) was perpendicular to the axis of the braiding machine (Figure 15(B)). The angle control of the robot arm was performed using the angular velocity ω calculated using (Equation 21) below. r I used it.

[0096]

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[0097] 8) A mandrel with a braided structure formed on its surface was placed in a mold adjusted to a vacuum (-0.1 MPa), and a resin component (vinyl ester resin composition) was pressure-injected using the RTM method. The mandrel was then left to cure at room temperature for 3 hours and then in an 80°C atmosphere for 2 hours to form a curved pipe made of FRP. After demolding from the mold, the FRP curved pipe was heated to 200°C to melt and remove the mandrel, obtaining a hollow curved pipe. As an example, Figure 16 shows a diagram of the curved pipe obtained in Example 1 of Table 2.

[0098] (Test method) <V of a curved pipe> f (Measurement of fiber volume content) Following the method in accordance with JIS K7075 (1991), the mass of the test specimen was measured by the combustion method, and after measuring the density of the test specimen, the obtained value was applied to the following (Equation 22) to determine the fiber volume content V. f The result was calculated.

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[0099] <Measurement of the tensile modulus of a curved pipe> From the central part of the bent section of the curved pipe prepared using the method described above, test specimens with dimensions of L50mm × W5mm × 1.5tmm were taken from one location each on the inside and outside using the water jet method (see Figure 16). Then, tensile tests were performed on test specimens taken from the inside and outside of the central part of the bent section of the curved pipe, in accordance with JIS K7164 (2005), under conditions of 23±2°C and 50±10% humidity, at a speed of 1 mm / min. The tensile modulus E was calculated from the obtained stress-strain curves using the following formula (Equation 23).

[0100]

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[0101] In this test, the region where the slope is a straight line is used as the strain reading range. σ1: Tensile stress (MPa) measured at strain ε1 = 0.0025 σ²: Tensile stress (MPa) measured at strain ε² = 0.0050 The tensile modulus E is calculated using the above (Equation 23). Then, the tensile modulus of the specimen taken from the inside of the central part of the bent section of the bent pipe was defined as E(in) (see Figure 16), and the tensile modulus of the specimen taken from the outside of the central part of the bent section of the bent pipe was defined as E(out) (see Figure 16).

[0102] <Destructive testing of curved pipes> For the curved pipes prepared using the method described above, the chuck portion shown in Figure 17 was gripped with a chuck, and the tensile stress (test force: F) until the test piece broke was measured using a method similar to the tensile test method used in "Measurement of Tensile Modulus of Curved Pipes" described above. The test speed was set to 6 mm / min, and the breaking strength was calculated using the following formula (Equation 24) (each test was performed 3 times). <Method for testing the destructive properties of curved pipes> ·Equipment Autograph: Amsler Strain Gauge: KFGS-2-120-C1-11LIM3R, manufactured by Kyowa Electric Industry Co., Ltd. Strain gauge adhesive: CC-33A Kyowa Electric Industry • Condition adjustment Temperature 23±2℃, humidity 50±10%, 16 hours or more • Test conditions Test environment: Temperature 23±2℃, Humidity 50±10% Load cell capacity: 100kN Test speed: 6 mm / min Number of attempts: 3 Chuck section: Core metal inserted to prevent crushing by the chuck.

[0103]

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[0104] (Regarding the test results) <Determination of pass / fail criteria for curved pipes> Since FRP (fiber-reinforced plastic) bent pipes are often used as substitutes for metal parts (e.g., aluminum alloys), they were deemed acceptable if they maintained strength characteristics (elastic modulus) equivalent to those of aluminum alloys, from the perspective of being a substitute for aluminum alloys. As a strength characteristic, the tensile modulus of the central part of the bent section of the bent pipe, calculated in the tensile test described above, was used as the indicator value.

[0105] Furthermore, in curved pipes, it is preferable that the strength characteristics are uniform across all sections. However, in the bent portion of a curved pipe, differences in strength characteristics tend to occur between the inside and outside due to the condition of the fiber members. Therefore, it is preferable to form a braided structure in such a way that the difference in strength properties between the inside and outside of the bent portion of the curved pipe is minimized as much as possible. If there is a large difference in strength and material properties between the inside and outside of the bend in a curved pipe, the side with the higher modulus of elasticity may break when a load is applied to the curved pipe and stress concentrates at the bend. Therefore, the more uniform the strength and material properties are between the inside and outside of the bend in a curved pipe, the less likely it is to break even when stress concentrates at the bend. From the above perspective, the pass / fail judgment for the strength characteristics of the bent pipe was based on measuring the tensile modulus E(in) of a test specimen taken from the inside of the central part of the bent portion of the bent pipe, and the tensile modulus E(out) of a test specimen taken from the outside of the central part of the bent portion of the bent pipe, and whether the ratio E(in) / E(out) was close to 1 (i.e., whether the strength properties of the inside and outside of the bent portion of the bent pipe were uniform). The state in which E(in) / E(out) was close to 1 was considered a preferred state, and the acceptable range of E(in) / E(out) was set based on the results of the fracture test of the bent pipe. Specifically, destructive tests were conducted on the curved pipes of Example 2 [E(in) / E(out)=1.05], Example 3 [E(in) / E(out)=0.90], Example 5 [E(in) / E(out)=1.00], Comparative Example 1 [E(in) / E(out)=0.82], and Comparative Example 5 [E(in) / E(out)=1.73], which have different E(in) / E(out) measurement results, from Examples 1 to 5 and Comparative Examples 1 to 5 listed in Table 2. The results are shown in Table 3. In Comparative Example 1, where E(out) was larger than E(in), stress concentration caused the outer surface of the bent portion of the curved pipe to break at 341 MPa. In Comparative Example 5, where E(in) was larger than E(out), stress concentration caused the inside of the bent portion of the curved pipe to fracture at 720 MPa. In contrast, in Examples 2, 3, and 5, where E(in) and E(out) were equivalent, the bent portion of the curved pipe did not break even when the pressure exceeded 1,000 MPa, and ultimately broke near the chuck portion, not at the bent portion of the curved pipe. Based on the above results, bent pipes with a fracture strength of 1,000 MPa or more were judged to be at an acceptable level, maintaining strength characteristics (elastic modulus) equivalent to that of aluminum alloy. From the E(in) / E(out) ratio of Examples 2, 3, and 5, in which the fracture strength was obtained, the acceptable range of E(in) / E(out) was set to 0.85 to 1.05. Based on these criteria, for each of the Examples 1-5 and Comparative Examples 1-5 shown in Table 2, bent pipes with an E(in) / E(out) ratio between 0.85 and 1.05 were classified as A rank (pass), while bent pipes that did not fall within this range were classified as B rank (fail).

[0106] [Table 3]

[0107] <Test results for curved pipes> [Comparative Example 1: An example that does not satisfy any of the following conditions: cf3(in) = 80-100%, cf3(out) = 80-100%, and Rm ≥ 0.50] Comparative Example 1 is an example using a braided structure with cf3(in) of 78.7%, cf3(out) of 77.9%, and an axol ratio Rm of 0 (no axol ratio used). However, the E(in) / E(out) of the curved tube was 0.82, indicating that the strength was not uniform between the inside and outside of the curved tube, resulting in a B rank (failure).

[0108] [Comparative Example 2: An example where Rm≧0.50 is satisfied, but cf3(in)=80~100% and cf3(out)=80~100% are not satisfied] Comparative Example 2 is an example using a braided structure with cf3(in) of 73.4%, cf3(out) of 62.0%, and an axis yarn ratio Rm of 0.50. However, the E(in) / E(out) of the curved tube was 0.83, indicating that the strength was not uniform between the inside and outside of the curved tube, resulting in a B rank (failure).

[0109] [Comparative Example 3: An example where cf3(in) = 80-100% and cf3(out) = 80-100% are satisfied, but Rm ≥ 0.50 is not satisfied] Comparative Example 3 is an example using a braided structure with cf3(in) at 95.8%, cf3(out) at 87.9%, and an axyl thread ratio Rm of 0.40. However, the E(in) / E(out) of the curved tube was 0.80, indicating that the strength was not uniform between the inside and outside of the curved tube, resulting in a B rank (failure).

[0110] [Comparative Example 4: An example where cf3(in) = 80-100% is satisfied, but cf3(out) = 80-100% and Rm ≥ 0.50 are not satisfied] Comparative Example 4 is an example using a braided structure with cf3(in) at 99.8%, cf3(out) at 77.5%, and an axol ratio Rm of 0. However, the E(in) / E(out) of the curved tube was 0.24, indicating that the strength was not uniform between the inside and outside of the curved tube, resulting in a B rank (failure).

[0111] [Comparative Example 5: An example where cf3(in) = 80-100% and Rm ≥ 0.50 are satisfied, but cf3(out) = 80-100% is not satisfied] Comparative Example 5 is an example using a braided structure with cf3(in) at 99.5%, cf3(out) at 48.0%, and an axial yarn ratio Rm of 0.50. However, the E(in) / E(out) of the curved tube was 1.73, indicating that the strength was not uniform between the inside and outside of the curved tube, resulting in a B rank (failure).

[0112] [Example 1] Example 1 uses a braided structure with cf3(in) at 82.2%, cf3(out) at 81.5%, and an axial yarn ratio Rm of 0.50. The E(in) / E(out) of the curved tube was 0.99, resulting in an A-rank (pass) rating with equal strength on the inside and outside of the curved tube.

[0113] [Example 2] Example 2 uses a braided structure with cf3(in) at 90.1%, cf3(out) at 89.4%, and an axis yarn ratio Rm of 0.50. The E(in) / E(out) of the curved tube was 1.04, and the strength was uniform on the inside and outside of the curved tube, resulting in an A rank (pass).

[0114] [Example 3] Example 3 uses a braided structure with cf3(in) at 99.9%, cf3(out) at 99.6%, and an axis yarn ratio Rm of 0.50. The E(in) / E(out) of the curved tube was 0.86, resulting in an A rank (pass) with uniform strength on the inside and outside of the curved tube.

[0115] [Example 4] Example 4 uses a braided structure with cf3(in) at 100%, cf3(out) at 95.0%, and an axis yarn ratio Rm of 0.67. The E(in) / E(out) of the curved tube was 0.91, and the strength was uniform on the inside and outside of the curved tube, resulting in an A rank (pass).

[0116] [Example 5] Example 5 uses a braided structure with cf3(in) at 100%, cf3(out) at 99.1%, and an axis yarn ratio Rm of 0.67. The E(in) / E(out) of the curved tube was 1.00, and the strength was uniform on the inside and outside of the curved tube, resulting in an A rank (pass).

[0117] Regarding the upper limit of cf3, the cases where cf3(in) exceeds 100%, where cf3(out) exceeds 100%, and where both cf3(in) and cf3(out) are at 100% have not been verified because they are practically impossible to manufacture.

[0118] From the above results, it was confirmed that a bent pipe using a braided structure that satisfies all of the following conditions: cf3(in) = 80~100%, cf3(out) = 80~100%, and Rm ≥ 0.50, has uniform strength properties on the inside and outside of the bent portion (E(in) / E(out) in the range of 0.85~1.05), and can maintain strength characteristics (elastic modulus) equivalent to that of an aluminum alloy. [Explanation of Symbols]

[0119] 1. Bent pipe 11 Bent part 11A Inner circumference of the bent portion 11B Outer circumference of the bent portion 20 Circular Braid 21 spindles 22 tubes 30 Mandrels 71 Braided thread 72 Axle yarn 100 Large Drones 101 Main frame 102 Propeller 103 Propeller Guard 104 Arm 105 Skid

Claims

1. A curved pipe used as a component of a large unmanned aerial vehicle, The curved tube is made of FRP, constructed by combining braided threads and shaft threads and resin molding, and has a circular cross-section. The braided structure is such that the axial threads are incorporated along the central axis direction of the curved tube. The width of the braided thread is b f [mm] The number of the aforementioned braided threads is n [threads]. The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis of the curved tube is θ [°] The width of each cell in the braided structure of the curved pipe is f [mm]. The width of the aforementioned shaft thread is b m [mm] The number of the aforementioned axial threads is n m [Book] The fineness of the braided yarn is f b [dtex] The fineness of the aforementioned axial yarn is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the aforementioned axial thread is E m [GPa] an inner cover factor cf indicating a ratio of the area occupied by the braiding yarns and the axial yarns to the surface area of the braided structure, which corresponds to the inner circumference of the bent portion of the bent pipe and is obtained by the following (Formula 1) in this case 3 (in) has a value of 80% or more and 100% or less, and an outer cover factor cf indicating a ratio of the area occupied by the braiding yarns and the axial yarns to the surface area of the braided structure, which corresponds to the outer circumference of the bent portion of the bent pipe and is obtained by the following (Formula 1) 3 (out) has a value of 80% or more and 100% or less, and Furthermore, the axial filament ratio R is defined below (Equation 2). m However, R m A curved pipe for large unmanned aerial vehicles, characterized by satisfying the condition ≥ 0.

50. [Math 1] ...(Formula 1) [Math 2] ...(Formula 2)

2. The curved tube for a large unmanned aerial vehicle according to claim 1, characterized in that the braided thread has a rectangular cross-section in the shape of a tape.

3. The curved tube for a large unmanned aerial vehicle according to claim 1, characterized in that the braided thread and the shaft thread have a rectangular cross-section in the shape of a tape.

4. A method for manufacturing a curved tube made of FRP, having a circular cross-section, which is used as a component of a large unmanned aerial vehicle, and is constructed by combining braided threads and shaft threads to form a braided structure and resin molding, The curved pipe in question is, The width of the braided thread is b f [mm] The number of the aforementioned braided threads is n [threads]. The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis of the curved tube is θ [°] The width of each cell in the braided structure of the curved pipe is f [mm]. The width of the aforementioned shaft thread is b m [mm] The number of the aforementioned axial threads is n m [Book] The fineness of the braided yarn is f b [dtex] The fineness of the aforementioned axial yarn is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the aforementioned axial thread is E m [GPa] In this case, the inner cover factor cf, which is calculated by the following (Equation 3), represents the ratio of the braided yarn and the shaft yarn to the surface area of ​​the braided structure, corresponding to the inner circumference of the bent portion of the curved tube. 3 The value of (in) is 80% or less and less, and the outer cover factor cf, which indicates the ratio of the braided yarn and the shaft yarn to the surface area of ​​the braided structure corresponding to the outer circumference of the bent portion of the curved tube, is determined by the following (Equation 3). 3 The value of (out) is between 80% and 100%, Furthermore, the axial filament ratio R is defined below (Equation 4). m However, R m A method for manufacturing a curved tube for a large unmanned aerial vehicle, characterized in that the axial thread is arranged on the outer circumference of a mandrel along the central axis direction of the curved tube so as to satisfy the condition ≥ 0.50, and the braided thread and the axial thread are combined to form the curved tube. [Math 3] ...(Formula 3) [Math 4] ...(Formula 4)

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