Method of laying up a full composite propeller hub torque augmenting structure

Abstract

The application provides a full-composite propeller hub torsion-increasing structure layering method, which adopts mutual insertion layering at the propeller hub part, and the vertical layering effectively enhances the torsion resistance of the propeller hub part; the propeller blade and the propeller hub side wall are alternately laid along the propeller hub radial direction, which can reduce the wrinkles at the blade root during the laying, the profile error of the propeller blade caused by the wrinkles, and thus the propeller blade profile is accurate, the compliance stress transmission of the transition area of the propeller blade and the propeller hub is realized, and thus the stress concentration problem of the transition area is solved. The insertion type expansion mechanism used in the middle of the propeller hub solves the internal circumferential and development direction thermal pressure, and enhances the blade profile accuracy.

Description

Technical Field

[0001] This invention relates to the field of composite material propeller manufacturing technology, and in particular to a method for laying up a torsion-enhancing structure for a fully composite propeller hub. Background Technology

[0002] Composite material propellers have seen rapid development in design and manufacturing due to their superior properties compared to traditional metal propellers, including lightweight, high strength, design flexibility, fatigue resistance, corrosion resistance, and high damping. Current composite propeller manufacturing methods are mostly modular or integral. Modular propellers involve separately fabricating the blades and hub, then assembling them using mortise and tenon joints and other connection methods, with secondary processing at the root region. The blade root is a critical area where stress is concentrated. Modular propellers have a secondary interface during assembly, making them prone to vibration fatigue during operation. Furthermore, modular propellers suffer from discontinuous fibers at the blade root and stress concentration at joints, severely impacting performance. Therefore, integral composite propellers offer unparalleled advantages. The layup method of integral propellers is crucial to the molding quality and geometry. Traditional layup designs often use a single blade and hub, but this often results in numerous wrinkles at the blade root and hub connection, leading to increased geometric errors and compromised blade profile. The hub section often uses horizontal fiber laminations, which results in insufficient torsional resistance of the propeller hub. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for laying up a torsion-enhancing structure for a fully composite propeller hub. This method ensures smoother and more uniform fibers at the connection between the propeller blades and the hub, thereby reducing wrinkles at the blade root during the laying process, achieving precise blade profile, enhancing the hub's torsional resistance, and reducing stress concentration. The resulting propeller exhibits lower manufacturing process errors and higher quality. The technical solution provided by this invention is as follows:

[0004] A method for layup a fully composite propeller hub torsion-enhancing structure, comprising:

[0005] The design of blade ply and hub ply involves breaking down the complete propeller into several layered structures composed of blades and hubs, connecting the odd-numbered layers in the blade ply and hub ply into a whole ply, and forming an interlocking structure with the even-numbered layers in the hub ply.

[0006] The device is vertically inserted and installed according to the designed blade and hub ply layers.

[0007] During hot pressing and curing, an expansion mechanism is placed in the middle of the paddle hub. After the hot pressing is completed, the expansion mechanism is removed.

[0008] In this invention, the rotor hub layer is laid out differently from the traditional horizontal stacking, but with vertical interlocking. The odd-numbered layers of the blade and hub layers are connected into a single, integral layer, forming an interlocking structure with the even-numbered layers. During hot-press curing, an expansion mechanism is placed in the center of the hub to convert the axial force into radial force, making the vertical layers of the hub more compact. This reduces interlayer delamination failure and improves the bonding between the hub and blade. The layup consists of the rotor hub layer (including the blade portion), the hub sidewall layer, and the expansion mechanism. The rotor hub layer (including the blade portion) and the hub sidewall layer each include a water-facing surface and a backwater surface. The expansion mechanism consists of two equal-sized frustums and a C-ring (with a height equal to the two frustums and a diameter equal to the diameter of the base circle of the frustums).

[0009] Furthermore, the design of blade ply and hub ply specifically includes the following steps:

[0010] Step 1, Design of blade-in-hub ply: Divide the blade hub into multiple parts that match the number of blades. Each part is a blade-in-hub sidewall. Multiple blade-in-hub sidewalls form a complete blade-in-hub ply.

[0011] Step 2, Design of the propeller hub sidewall layup: The outer surface of the propeller hub is gradually reduced towards the central axis along the radial direction of the hub according to the thickness d of the prepreg. Then, the outer surface of each reduced hub is extracted and flattened to obtain the propeller hub layup.

[0012] Step 3: The hub portion of the blade-hub ply is the odd-numbered layer in the obtained hub ply, and the hub sidewall portion is the even-numbered layer in the obtained hub ply. They are laid radially alternately to form an interlocking structure.

[0013] Step 4: After the odd-numbered and even-numbered layers are laid, fill in the empty spaces inside.

[0014] Furthermore, during hot pressing and curing, the expansion mechanism placed in the middle of the paddle hub specifically includes two frustums and a C-ring. The two frustums are respectively located at both ends of the C-ring. The upper surface of the upper frustum is the large end, and the lower surface of the lower frustum is the large end. The small ends of the upper and lower frustums match the inner diameter of the C-ring. The C-ring is a circular ring structure with open ends, and it has an opening along the length direction in its circumference. The expansion mechanism constitutes part of the hot pressing mold and is used to provide internal radial force for the vertically inserted layup during hot pressing.

[0015] Furthermore, the thickness of the C ring is 0.2–0.5 mm.

[0016] Furthermore, in the blade and hub ply, for the blade part, starting from the first ply, every 4 ply are grouped together and laid layer by layer according to the ply angle of [0 / 45 / 90 / -45]. Each ply consists of four separate blade ply.

[0017] Compared with existing technologies, the advantages of the all-composite propeller laid using the full-composite hub torsion-enhancing structure layup method described in this invention are as follows: The alternating layup of blades and hub sidewalls along the radial direction of the hub reduces wrinkles during layup, thereby improving the layup quality of the blades and achieving precise blade profile. It also reduces stress concentration between the hub and blades. Furthermore, the interlocking layup method of the hub allows axial fibers to enhance its torsional resistance. During hot pressing, an insert-type expansion mechanism is used in the middle of the hub to convert axial force into radial force, resulting in a more compact structure, reducing deformation under load, minimizing process errors, and optimizing the overall composite propeller manufacturing method. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the outer surface structure of the propeller of the present invention;

[0020] Figure 2 This is a schematic diagram of the blade layup and expansion mechanism of the present invention;

[0021] Figure 3 This is a schematic diagram showing the shrinkage direction of the propeller hub and the dimensions of each layer in this invention;

[0022] In the diagram: 1. Water-slapping surface; 2. Backwater surface; 3. Blade and quarter-hull sidewall ply; 4. Hub sidewall ply; 5. C-ring; 6. Frustum; 7. Hub shrinkage direction. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figures 1-3As shown in the figure, an embodiment of the present invention discloses a layup method for a full composite propeller hub torsion enhancement structure, comprising the following steps:

[0025] S1. Taking a four-bladed propeller as an example, based on the propeller's shape data, a solid model of the propeller is constructed using a shape table in 3D modeling software. All outer surfaces of the propeller model are removed, the upper and lower circular surfaces of the hub are cut off, and the resulting outer surface model of the propeller is divided into a splashing surface and a back surface. Taking the splashing surface as an example, it is divided into four equal parts based on the hub's central axis. Each part consists of one blade along with a quarter of the hub sidewall. The four blades along with the quarter of the hub sidewall form a complete blade and part of the hub layup.

[0026] In the design of the blade portion within the rotor hub ply, a geometric mid-surface 4.77mm from both the upper and lower surfaces of the blade is selected as the reference plane for blade design. The upper half of the mid-surface is designated as the water-skimming surface, and the lower half as the backwater surface. Taking the water-skimming surface as an example, it is offset upwards from the mid-surface by a ply thickness of 0.14mm. The thickness d of each layer of carbon fiber composite prepreg is 0.14mm to 0.2mm. The mid-surface is considered as the dividing plane, and the portion below the mid-surface caused by the upward offset is removed. The outer surface of the water-skimming surface of the resulting blade model is then removed to obtain the first ply of the blade portion, and this process is repeated layer by layer upwards. The backwater surface is designed in the same way but in the opposite direction.

[0027] S2. The design of the propeller hub involves gradually reducing the thickness of the prepreg layer by layer towards the central axis along the radial direction of the outer surface of the propeller hub, based on a prepreg thickness of 0.14 mm. The outer surface of each reduced-size hub is then extracted and flattened to obtain the hub's ply. When the propeller rotates at high speed underwater, the hub experiences resistance and torsional force in the opposite direction of rotation. Previously, the ply of integral composite propeller hubs used horizontal stacking, which, given the circumferential force on the propeller, easily leads to radial misalignment between the hub plies, and in severe cases, torsional deformation. Therefore, the all-composite hub torsion-enhancing ply method uses two radially alternating plies: the blade-integrated hub ply and the hub sidewall ply, forming an interlocking structure. The blade-integrated hub ply consists of odd-numbered layers, while the even-numbered layers are the hub sidewall ply. These two components constitute the propeller hub ply. At this point, the propeller hub changes from horizontal to vertical layup, and the fibers that make up the hub also change from horizontal to vertical. When subjected to the centrifugal force generated by the high-speed rotation of the propeller, the vertically laid hub has a tighter interlayer bond and can withstand greater torsional forces. This effectively enhances the hub's torsional resistance.

[0028] S3. The blade-hub ply and hub sidewall ply obtained from the above method, wherein the blade-hub ply consists of the blade portion and the hub portion. For the blade portion, starting with the first ply, every four ply layers are grouped together and laid layer by layer according to the ply angle [0 / 45 / 90 / -45]. Each ply layer consists of four separate blade ply layers.

[0029] S4. Regarding the hub section, during the composite propeller layup process, the blade root section, where the transition from the blade to the hub occurs, is prone to problems such as wrinkles, fiber tearing, and loose bonding due to the almost perpendicular layup angle and the pulling effect from adjacent blades and the hub. As the layup continues to stack, the wrinkles at the blade root will bulge, damaging the blade profile. In the design process, the blades are laid up separately, and the number of hubs is divided into equal parts equal to the number of blades, forming a blade-hulled hub. This reduces the pulling effect from the overall hub and other blades at the blade root, ensuring a smoother and more uniform layup at the connection between the propeller blades and the hub. This achieves the goals of reducing wrinkles during layup, achieving precise blade profile, minimizing manufacturing process errors, and improving quality. Since it is an integral part of the blade, the layup angle follows the layup angle of the blade. This section describes the intercalation part of a composite propeller ply configuration where the blade and hub layers are interlocked. The quarter-hub portion is used as an odd-numbered layer in the hub ply. Each odd-numbered hub ply consists of four quarter-hub layers. The blade and hub layers are interlocked and laid radially alternately.

[0030] S5. Because the blade thickness is much smaller than the hub diameter, after the blade and part of the hub ply and hub sidewall ply are completed, there is still a gap in the propeller hub. At this time, the hub ply is continued to shrink radially along the hub by one layer of prepreg thickness of 0.14mm, and the outer surface is extracted to supplement the intermediate hub. The number of ply layers is calculated by subtracting twice the number of blade ply layers (10.73mm) from the hub radius of 36.145mm, and then subtracting the expansion mechanism's opening radius of 12mm to obtain a ply thickness of 13.415mm. Dividing the ply thickness of 13.415mm by the thickness of one layer of prepreg (0.145mm) gives the number of ply layers. This propeller has a total of 93 ply layers.

[0031] S6. Due to the aforementioned layup method, the force experienced by the hub during hot pressing should be radial, while the force during hot pressing is axial. Therefore, to ensure a tighter layup and better mechanical properties in the hub during the overall hot pressing process, an expansion mechanism is designed and embedded. The expansion mechanism consists of two frustums and a C-ring, forming part of the hot pressing mold. During hot pressing, it provides internal radial force to the vertically inserted layup. After hot pressing, the expansion mechanism is removed. The height of the C-ring and the height of the two frustums are equal to the hub height, which is 36.14 mm. The C-ring thickness is 0.3 mm, and the radius of the C-ring when closed is equal to the radius of the smaller circle of the frustum, which is 10 mm. The radius of the larger circle of the frustum, 12 mm, is equal to the hub radius of 36.145 mm minus the radial layup thickness radius of the hub, which is 24.145 mm. When this expansion mechanism is in use, the upper and lower truncated cones are placed at the center of the composite material propeller's water-facing mold and back-facing mold hub. The closed C-ring stands between the two truncated cones. When the truncated cones are subjected to axial pressure, they are gradually squeezed into the C-ring. The C-ring begins to expand and converts the axial force into a radial force, making the sidewall layup of the propeller hub more compact.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for layup a fully composite propeller hub torsion-enhancing structure, characterized in that, include: The design of blade ply and hub ply involves breaking down the complete propeller into several layered structures composed of blades and hubs, connecting the odd-numbered layers in the blade ply and hub ply into a whole ply, and forming an interlocking structure with the even-numbered layers in the hub ply. The device is vertically inserted and installed according to the designed blade and hub ply layers. During hot pressing and curing, an expansion mechanism is placed in the middle of the paddle hub. After the hot pressing is completed, the expansion mechanism is removed. The design of blade ply and hub ply specifically includes the following steps: Step 1, Design of blade-in-hub ply: Divide the blade hub into multiple parts that match the number of blades. Each part is a blade-in-hub sidewall. Multiple blade-in-hub sidewalls form a complete blade-in-hub ply. Step 2, Design of the propeller hub sidewall layup: The outer surface of the propeller hub is gradually reduced towards the central axis along the radial direction of the hub according to the thickness d of the prepreg. Then, the outer surface of each reduced hub is extracted and flattened to obtain the propeller hub layup. Step 3: The hub portion of the blade-hub ply is the odd-numbered layer in the obtained hub ply, and the hub sidewall portion is the even-numbered layer in the obtained hub ply. They are laid radially alternately to form an interlocking structure. Step 4: After the odd-numbered and even-numbered layers are laid, fill in the empty spaces inside.

2. The layup method for a full composite propeller hub torsion-enhancing structure according to claim 1, characterized in that, Step 4 specifically includes the following steps: Continue to reduce the thickness of one layer of prepreg along the radial direction of the propeller hub by the propeller hub layup, and extract the outer surface to supplement the intermediate propeller hub. The number of layup layers is obtained by subtracting twice the product of the number of propeller blade layup layers and the thickness of a single layer of prepreg by the radius of the propeller hub D, and then subtracting the expansion radius R of the expansion mechanism to obtain the thickness of the supplementary layer A. The thickness of the supplementary layer A is divided by the thickness of one layer of prepreg to obtain the number of supplementary layers.

3. The layup method for a full composite propeller hub torsion-enhancing structure according to claim 1, characterized in that, During hot pressing and curing, the expansion mechanism placed in the middle of the paddle hub specifically includes two frustums and a C-ring. The two frustums are respectively set at both ends of the C-ring. The upper surface of the upper frustum is the large end, and the lower surface of the lower frustum is the large end. The small ends of the upper and lower frustums match the inner diameter of the C-ring. The C-ring is a circular ring structure with open ends and has an opening along its length in the circumferential direction. The expansion mechanism constitutes part of the hot pressing mold and is used to provide internal radial force for the vertically inserted layup during hot pressing.

4. The layup method for the all-composite propeller hub torsion enhancement structure according to claim 3, characterized in that, The thickness of the C-ring is 0.2~0.5mm.

5. The layup method for a fully composite propeller hub torsion-enhancing structure according to claim 1, characterized in that, In the blade and hub ply, for the blade part, starting from the first ply, every 4 ply are grouped together and laid layer by layer according to the ply angle of [0 / 45 / 90 / -45]. Each ply consists of four separate blade ply.

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