A method for assembling and positioning a core mold of a three-dimensional woven prepreg blade

Abstract

The present application belongs to composite material forming assembly technology, and relates to a blade three-dimensional braiding preform core mold assembly positioning method. The method is used for manufacturing a composite material blade of a tail rotor of a high-speed helicopter. A positioning pin mode is adopted to assemble the blade root inner sleeve and the foam, so that accurate positioning between the blade root inner sleeve and the foam can be ensured. A positioning key is designed to assemble the end face positioning groove of the blade root inner sleeve and the tool positioning plate, so that accurate positioning of the blade root inner sleeve and the mold can be ensured, and the assembly positioning problem of the blade root inner sleeve and the foam can be accurately ensured. The blade root inner sleeve bonding surface is coated with anticorrosive primer and adhesive film and is wound with two layers of root winding cloth, so that the corrosion resistance and the bonding strength between the blade root inner sleeve and the foam can be improved. The core mold rigidity is improved, and the foam debris is prevented from entering the preform fiber, so that the blade quality can be obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding and assembly technology, and relates to a method for assembling and positioning a three-dimensional braided preform core mold for propeller blades. Background Technology

[0002] Three-dimensional braided products offer advantages such as strong design flexibility, resistance to delamination, and high fatigue resistance. The development of a new tail thrust rotor blade utilizes three-dimensional braided carbon fiber skin and spars, along with RTM molding technology. The three-dimensional braided prefabricated tail thrust rotor blade is fabricated using a three-dimensional braiding machine on a prefabricated core mold, where the carbon fiber skin and spars are woven. The prefabricated core mold is obtained by assembling the blade root inner sleeve with foam. However, due to the elliptical shape of the inner sleeve, positioning difficulties arise during its assembly with the foam; the blade foam is designed with a large twist angle and other special structures, making it prone to deformation; furthermore, foam debris easily enters the prefabricated body during the weaving process. These factors directly affect the weaving quality of the prefabricated body, and consequently, the subsequent blade assembly and molding quality. Summary of the Invention

[0003] This invention proposes a three-dimensional woven preform core mold assembly method for manufacturing composite material blades for high-speed helicopter tail rotors.

[0004] Technical solution

[0005] The technical solution of this invention is a method for assembling and positioning a three-dimensional woven preform core mold for propeller blades. The specific tooling installation method and molding steps are as follows:

[0006] 8) Assembly of the propeller root inner sleeve and locating pin: First, the propeller root inner sleeve (1) and locating pin 1 (2) are assembled using the temperature difference assembly method, such as... Figure 1 As shown.

[0007] 9) Assembly of the inner sleeve (1) and foam (3) of the propeller root: Assemble the inner sleeve (1) of the propeller root after the positioning pin 1 (2) is assembled with the foam (3), and after the assembly is completed, wrap two turns of propeller root wrapping cloth (4). Figure 2 This is a partial sectional view of the assembly of the inner sleeve and foam at the paddle root. A groove is provided at the leading edge of the foam (3), and a leading edge counterweight (5) is placed in the groove. The leading edge counterweight (5) needs to be coated with anti-corrosion primer and wrapped with a film, a leading edge counterweight cover (6), a counterweight barrier block (7), and a foam leading edge cover (8). Figure 3 This is a schematic diagram of the assembly of the inner sleeve and foam at the propeller root.

[0008] 10) Blade wrapping assembly: wrap the entire surface of the foam (3) with prepreg glass cloth. After wrapping, vacuum compaction is performed. Using foam wrapping can improve the core mold rigidity after curing and also prevent foam debris from entering the preform fiber during the blade preform weaving process, thus preventing it from being contaminated.

[0009] 11) Preparation of precast core mold assembly molding die, such as... Figure 4 As shown. After cleaning the assembly mold with acetone and letting it dry, apply a release agent to the surface of the mold.

[0010] 12) Install the positioning plate (10) at the blade root position of the lower mold body (9) of the blade preform core mold tooling, and insert the ball head pin (11) for initial fixation. Place the core mold parts after the blade root inner sleeve and foam assembly are completed on the surface of the lower mold (9), install and adjust the blade root inner sleeve (1) into place, insert the positioning key (12), so that the positioning plate (10) and the positioning groove on the end face of the blade root inner sleeve (1) are assembled in place, ensuring the radial positioning of the blade root part of the core mold. After assembly, tighten the internal hexagon screw (13) on the positioning block (10) to ensure the blade spanwise positioning. Figure 5 A partial isometric view of the blade preform core mold assembly at the blade root region. After completing the blade root positioning, the assembled blade preform core mold is fitted to the outer shape of the lower model surface.

[0011] 13) Assemble the guide plate (14) and locating pin 2 (15) on the lower mold surface in sequence, as follows: Figure 6 As shown.

[0012] The upper mold (17) and the lower mold (9) are assembled together using lifting rings (16). The guide plate (14) provides rough positioning and guidance, while the positioning pin (15) provides precise positioning, ensuring that the upper and lower molds fit together properly. Finally, hexagonal screws (18) are inserted into the upper mold (17) and tightened with a torque wrench until there is no gap between the upper and lower molds. Figure 7 A schematic diagram of the assembly of the propeller preform core mold.

[0013] 14) Place the tooling for assembling the blade preform core mold into an autoclave for curing. Curing parameters: vacuum 0.08~0.1MPa, heating rate not exceeding 1.5℃ / min, first heat to 80℃ and apply 0.5MPa external pressure, when the pressure reaches 0.5MPa, hold at the temperature and pressure for 0~35min; then continue heating to 180℃.

[0014] ±5℃, hold at pressure for 180min ±3min; finally, cool down to below 60℃ at a rate not exceeding 3℃ / min and release pressure. When the pressure drops to 0.08~0.15MPa, open the vacuum and maintain for at least 10min until the product is removed from the can. After curing, remove any lumps to obtain the preformed core mold part, as shown below. Figure 8 The diagram shown is a schematic of the core mold part of the paddle weaving prefabrication.

[0015] Furthermore, 2) the bonding surface between the inner sleeve of the paddle root and the foam needs to be coated with anti-corrosion primer and wrapped with adhesive film to ensure the bonding strength between the inner sleeve and the foam after curing.

[0016] Furthermore, the anti-corrosion primer is specifically J-117, and the adhesive film is specifically J-271B.

[0017] Furthermore, in 2), the winding cloth (4) and the heavy wrapping cloth (6) are specifically two layers of winding.

[0018] Furthermore, 2) the materials for the root winding cloth, the leading edge counterweight wrapping cloth, the counterweight blocking block, and the leading edge wrapping cloth are all pre-impregnated carbon cloth 5224 / CF3052 / 39.

[0019] Furthermore, the prepreg glass cloth is specifically 5224 / EW110C / 44.

[0020] Furthermore, the foam wrapping method in 3) allows for cutting and splicing.

[0021] Furthermore, the release agent in 4) is RAM-225.

[0022] Technical effect

[0023] 1. Using a locating pin to assemble the inner sleeve of the propeller root with the foam can ensure precise positioning between them.

[0024] 2. Design a positioning key to assemble the positioning groove on the end face of the inner sleeve of the propeller root with the tooling positioning plate, so as to accurately position it with the mold. With the addition of the mold cavity, the positioning of the inner sleeve of the propeller root and the foam assembly can be accurately guaranteed.

[0025] 3. Apply anti-corrosion primer, apply adhesive film, and wrap two layers of root wrapping cloth to the bonding surface of the inner sleeve of the propeller root. This can ensure improved corrosion resistance and bonding strength between the inner sleeve of the propeller root and the foam.

[0026] Because foam undergoes significant deformation during heating and easily sheds foam debris, which can contaminate the precast structure, wrapping it with a layer of pre-impregnated glass cloth and curing it within the tooling cavity helps prevent deformation of the precast mandrel, increases mandrel rigidity, and prevents foam debris from entering the precast fibers, thus significantly improving blade quality. Attached Figure Description

[0027] Figure 1 Isometric view of the assembly of the inner sleeve and locating pin at the propeller root.

[0028] Figure 2 Partial sectional view of the inner sleeve and foam assembly of the propeller root

[0029] Figure 3 Schematic diagram of the assembly of the inner sleeve and foam of the propeller root

[0030] Figure 4 Schematic diagram of the lower mold body of the propeller preform core mold assembly mold

[0031] Figure 5Enlarged isometric view of the blade preform core mold assembly at the blade root area.

[0032] Figure 6 Schematic diagram of the precast core mold assembly process

[0033] Figure 7 Schematic diagram of blade preform core mold assembly

[0034] Figure 8 Schematic diagram of paddle-woven prefabricated core mold parts Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] 1) Assembly of the propeller root inner sleeve and the locating pin: First, the propeller root inner sleeve (1) and the locating pin 1 (2) are assembled using the temperature difference assembly method, such as... Figure 1 As shown.

[0037] 2) Assembly of the inner sleeve (1) and foam (3) of the propeller root: Assemble the inner sleeve (1) of the propeller root after the positioning pin 1 (2) is assembled with the foam (3), and after the assembly is completed, wrap two turns of propeller root wrapping cloth (4). Figure 2 This is a partial sectional view of the assembly of the inner sleeve and foam at the paddle root. A groove is provided at the leading edge of the foam (3), and a leading edge counterweight (5) is placed in the groove. The leading edge counterweight (5) needs to be coated with anti-corrosion primer and wrapped with a film, a leading edge counterweight cover (6), a counterweight barrier block (7), and a foam leading edge cover (8). Figure 3 This is a schematic diagram of the assembly of the inner sleeve and foam at the propeller root.

[0038] 3) Blade wrapping assembly: wrap the entire surface of the foam (3) with prepreg glass cloth. After wrapping, vacuum compaction is performed. Using foam wrapping can improve the core mold rigidity after curing and also prevent foam debris from entering the preform fiber during the blade preform weaving process, thus preventing it from being contaminated.

[0039] 4) Preparation of precast core mold assembly molding mold, such as... Figure 4 As shown. After cleaning the assembly mold with acetone and letting it dry, apply 3 to 5 coats of release agent RAM-225 to the mold surface.

[0040] 5) Install the positioning plate (10) at the blade root position of the lower mold body (9) of the blade preform core mold tooling, and insert the ball head pin (11) for initial fixation. Place the core mold parts after the blade root inner sleeve and foam assembly are completed on the surface of the lower mold (9), install and adjust the blade root inner sleeve (1) into place, insert the positioning key (12), so that the positioning plate (10) and the positioning groove on the end face of the blade root inner sleeve (1) are assembled in place, ensuring the radial positioning of the blade root part of the core mold. After assembly, tighten the internal hexagon screw (13) on the positioning block (10) to ensure the blade spanwise positioning. Figure 5 A partial isometric view of the blade preform core mold assembly at the blade root region. After completing the blade root positioning, the assembled blade preform core mold is fitted to the outer shape of the lower model surface.

[0041] 6) Assemble the guide plate (14) and locating pin 2 (15) on the lower mold surface in sequence, as follows: Figure 6 As shown.

[0042] The upper mold (17) and lower mold (9) are assembled together using lifting rings (16). The guide plate provides rough positioning and guidance, while the locating pin provides precise positioning, ensuring that the upper and lower molds are properly fitted. Finally, hexagonal screws (18) are inserted into the upper mold (17) plate and tightened with a torque wrench until there is no gap between the upper and lower molds. Figure 7 A schematic diagram of the assembly of the propeller preform core mold.

[0043] 7) Place the tooling for assembling the blade preform core mold into an autoclave for curing. Curing parameters: vacuum 0.08~0.1MPa, heating rate not exceeding 1.5℃ / min, first heat to 80℃ and apply an external pressure of 0.5MPa, when the pressure reaches 0.5MPa, hold at the temperature and pressure for 0~35min; then continue heating to 180℃.

[0044] ±5℃, hold at pressure for 180min ±3min; finally, cool down to below 60℃ at a rate not exceeding 3℃ / min and release pressure. When the pressure drops to 0.08~0.15MPa, open the vacuum and maintain for at least 10min until the product is removed from the can. After curing, remove any lumps to obtain the preformed core mold part, as shown below. Figure 8 The diagram shown is a schematic of the core mold part of the paddle weaving prefabrication.

[0045] Furthermore, 2) the bonding surface between the inner sleeve of the paddle root and the foam needs to be coated with anti-corrosion primer and wrapped with adhesive film to ensure the bonding strength between the inner sleeve and the foam after curing.

[0046] Furthermore, the anti-corrosion primer is specifically J-117, and the adhesive film is specifically J-271B.

[0047] Furthermore, in 2), the winding cloth (4) and the heavy wrapping cloth (6) are specifically two layers of winding.

[0048] Furthermore, 2) the materials for the root winding cloth, the leading edge counterweight wrapping cloth, the counterweight blocking block, and the leading edge wrapping cloth are all pre-impregnated carbon cloth 5224 / EW110C / 44.

[0049] Furthermore, the prepreg glass cloth is specifically 5224 / EW110C / 44.

[0050] Furthermore, the foam wrapping method in 3) allows for cutting and splicing.

[0051] During the trial molding process, it was found that the propeller preform assembly could not be placed into the mold, leading to difficulties in mold closing. The main influencing factors included: 1. Excessive width at the trailing edge of the preform; 2. Misalignment between the inner sleeve and foam at the propeller root, resulting in positioning difficulties.

[0052] Phenomenon 1:

[0053] When the preform was placed into the mold, its trailing edge interfered with the edge of the mold. On-site inspection revealed that the chord length of the interference area of ​​the blade preform was wider than the chord length of the mold at that location. Upon touch inspection, it was found that the trailing edge of the foam inside the preform extended beyond the edge of the mold. Measurement with a long ruler showed that the interference area was located near the starting position of the edge filling.

[0054] Analysis: The blade shape was determined before mold design, and the outermost layer of the injection-molded blade is wrapped with fiberglass cloth during injection molding. Therefore, the mold size should be larger than the outline of the preform. If the mold size is normal, it indicates: 1. The foam manufacturing inside the preform is out of tolerance. Subsequent processing requires checking whether the shape and dimensions meet design requirements. 2. The thickness of the preform is out of tolerance. Based on on-site inspection, this fault is primarily due to excessive foam tolerance.

[0055] This measure:

[0056] a) Create a standard foam piece according to the injection molding paddle model, place it in the mold for comparison, and check whether there are any problems with the mold;

[0057] b) To ensure that this part can assist in the testing of the RTM system, it is tentatively decided to punch or cut open the woven skin at the out-of-tolerance position of the rear edge of the preform, and then grind the out-of-tolerance area of ​​the rear edge foam to ensure normal mold insertion.

[0058] Expert opinion:

[0059] 1. Nanbo Institute conducted process exploration to confirm the compatibility between the woven body and the foam during the weaving process, and checked the deviation of the perimeter and thickness of the precast body cross-section after weaving from the design dimensions.

[0060] 2. Factory 372 inspected the foam deviation of this piece;

[0061] 3. The foam size was modified, and the starting position of the trailing edge strip was moved towards the root of the blade, with a full length of 315mm.

[0062] Phenomenon 2:

[0063] The blade twist angle exceeds the surface of the mold groove, making it impossible to fit the mold. Upon inspection, it was found that the installation angle of the inner sleeve of the blade root and the foam is inconsistent. When the outer sleeve is positioned according to the positioning groove of the inner sleeve of the blade root, the twist angle of the blade preform deviates from the design state, resulting in the blade's twist angle deviating significantly from the mold along the spanwise direction.

[0064] Analysis: During the pre-curing of the foam core, inner sleeve, and foam covering, the corresponding pre-compression fixture was not made. Vacuum bag pressure curing was used instead, and positioning fixtures were lacking, resulting in poor molding quality.

[0065] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of positioning a core mold for a blade three-dimensional woven preform, characterized by, The steps are as follows: 1) The inner sleeve of the root (1) is assembled with the first positioning pin: first, the inner sleeve of the root (1) is assembled with the first positioning pin (2) by using the temperature difference assembly method; 2) The inner sleeve of the root (1) is assembled with the foam (3): the inner sleeve of the root (1) assembled with the first positioning pin (2) is assembled with the foam (3), after the assembly is completed, two turns of the root winding cloth (4) are wound, a groove is formed at the front edge position of the foam (3), the front edge counterweight (5) is arranged in the groove, the front edge counterweight (5) is coated with anticorrosive primer, and is wrapped with a film and a front edge counterweight wrapping cloth (6), a counterweight blocking block (7) and a foam front edge wrapping cloth (8); 3) The blade wrapping cloth is assembled, the entire surface of the foam (3) is wrapped with a pre-impregnated glass cloth, after the wrapping cloth is completed, vacuum extraction and compaction curing are performed; 4) The preform core mold assembly is assembled and the mold is prepared, the assembled mold is cleaned with acetone and dried, then the mold surface is coated with a release agent; 5) The positioning plate (10) is installed at the root position of the lower mold body (9) under the blade preform core mold tool, the ball head pin (11) is inserted for preliminary fixation; the core mold part assembled with the inner sleeve of the root and the foam (3) is placed on the profile of the lower mold body (9), the inner sleeve of the root (1) is installed and adjusted to the position, the positioning key (12) is inserted, the positioning plate (10) is assembled to the position with the end face positioning groove of the inner sleeve of the root (1), and the radial positioning of the core mold root part is ensured; after the assembly is completed, the first inner hexagonal screw (13) on the positioning plate (10) is tightened to ensure the blade edgewise positioning, after the root positioning is completed, the assembled blade preform core mold is attached to the profile of the lower mold; 6) The guide plate (14) and the second positioning pin (15) are assembled on the lower mold profile in sequence, the upper mold (17) is assembled with the lower mold body (9) by using the lifting ring (16), the guide plate (14) plays a coarse positioning guide role, the second positioning pin (15) plays a precise positioning role, the upper and lower molds are ensured to be fitted to the position, finally the second inner hexagonal screw (18) is inserted into the upper mold (17) plate and is tightened by using a torque wrench until there is no gap between the upper and lower molds; 7) The tooling of the blade preform core mold assembly is placed in a hot press tank for curing, the curing parameters are as follows: vacuum 0.08-0.1 MPa, temperature rising rate not greater than 1.5 ℃ / min, first rising to 80 ℃ with 0.5 MPa external pressure, when the pressure reaches 0.5 MPa, pressure maintaining and heat preservation for 0-35 min; then continuously rising to 180±5 ℃, pressure maintaining and heat preservation for 180 min±3 min; finally, the temperature is reduced to below 60 ℃ at a rate not greater than 3 ℃ / min, the pressure is released, when the pressure is reduced to 0.08-0.15 MPa, the vacuum is opened, and the pressure is maintained for more than 10 min until the tank is opened; after the curing is completed, the gum tumor is removed, and the preform core mold part is obtained.

2. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 1, wherein 2) The inner sleeve of the middle root (1) and the foam (3) bonding surface need to be coated with anticorrosive primer and wrapped with a film to ensure the bonding strength of the inner sleeve and the foam (3) after curing.

3. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 2, wherein The anticorrosive primer is J-117, and the film is J-271B.

4. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 3, wherein 2) The root winding cloth (4) and the front edge counterweight wrapping cloth (6) are two layers of winding.

5. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 4, wherein 2) The middle root winding cloth (4), the front edge counterweight cloth (6), the counterweight barrier block (7), and the foam front edge cloth (8) are all made of pre-impregnated carbon cloth 5224 / CF3052 / 39.

6. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 5, wherein The pre-impregnated glass cloth is specifically 5224 / EW110C / 44.

7. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 6, wherein The 3) middle foam cloth allows for cutting and splicing.

8. A method of positioning a core mold for a blade three-dimensional woven preform according to claim 7, wherein The 4) release agent is RAM-225.

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