A method of maintaining a vacuum for composite blade layup

Abstract

The present application belongs to the field of composite material blade forming and tooling die, in particular to a method for maintaining the vacuum degree of composite material blade laying. The set of alternative movable blocks is installed on the blade forming die, which can meet the normal process of composite material blade skin laying, and at the same time meet the process requirements of vacuum extraction during skin laying. When the upper and lower forming dies of the composite material blade are pre-pressed, the process requirements of pre-pressing the required recess for the blade tip iron mounting on the surface of the blade body can be met. Then, after the upper and lower forming dies of the blade are pre-pressed, the set of alternative movable blocks is removed, the blade tip iron is placed in the recess pre-pressed on the blade body, and another set of iron forming movable blocks is installed, so that the bonding and curing of the blade tip iron can be completed. The bonding strength of the bonded blade tip iron meets the process requirements, and the knocking inspection is normal, which smoothly transitions with the blade body without steps.

Description

Technical Field

[0001] This invention belongs to the field of composite material blade molding and tooling molds, specifically a method for maintaining the vacuum degree of composite material blade laying. Background Technology

[0002] During the skin layup process of composite blades, vacuum bags need to be made on the blade forming mold to vacuum the prepreg layers and remove the air trapped between the layers. The purpose is to reduce the porosity of the blade skin, avoid delamination, and improve the surface quality of the blade.

[0003] The molding die for a certain type of helicopter composite rotor blade is equipped with a tip-mounted iron-cladding pre-compression / molding movable block. This movable block facilitates the pre-compression of the tip-mounted iron-cladding position and the replacement of the iron-cladding during mold closing. This movable block can be freely removed and installed using a hydraulic cylinder. However, a gap exists between this movable block and the rotor blade molding die. This causes air leakage at the gap between the tip-mounted iron-cladding pre-compression movable block and the die during vacuuming of the rotor blade skin layup, resulting in insufficient vacuum in the vacuum bag and failure to meet process requirements. This directly affects the surface quality of the composite rotor blade skin. Summary of the Invention

[0004] To address the problems described in the background above and to solve the problem of substandard vacuum caused by air leakage from the movable block, this invention provides a method for maintaining vacuum in composite blade laying. This method allows for the perfect fabrication of vacuum bags on the blade forming mold during the composite blade skin layup process, preventing air leakage and meeting the process requirements for vacuum.

[0005] Technical solution

[0006] A method for maintaining vacuum in composite blade installation includes the following steps:

[0007] Step 1: Using the pre-compression movable block of the ladle as a sample, a set of replacement movable blocks is replicated. This set of replacement movable blocks consists of an upper mold movable block and a lower mold movable block, which are installed in the upper and lower molds of the paddle forming process, respectively.

[0008] Step 2: Remove the lumps from the blade forming mold, use a cleaning agent to wipe the surface of the tooling cavity to remove oil stains, and after drying, use masking tape to isolate the place where the putty strip is placed. Apply three thin layers of release agent to the mold surface using a clean wiping method. Each layer should be applied in one direction. When applying the next layer of release agent, it should be applied in a direction perpendicular to the previous layer to ensure that the release agent can completely cover the previous layer.

[0009] Step 3: After applying release agent to the replacement lower mold block and upper mold block in the same manner, install them onto the paddle forming mold;

[0010] Step 4: Lay the prepreg according to the blade process instructions and layup book requirements. First, lay two layers of glass cloth prepreg on the iron-clad part of the mold as a backing cloth. Then, lay the first layer of carbon fiber prepreg according to the laser projection data line. After the first layer is laid, make a vacuum bag on the surface of the blade forming mold and vacuum and compact it.

[0011] Step 5: Remove the paper tape from the blade forming mold, stick putty strips to the protected area, cut the vacuum bag film according to the size of the blade forming mold, and stick the putty strips to the concave cavity of the blade forming mold at the position of the movable block, so that all the gaps (i.e. air leakage points) formed by the movable block are completely covered inside the vacuum bag. The vertical side of the movable block is 50mm away from the outer edge of the blade forming mold. After placing the putty strips, leave enough width and space to place the breathable felt and rubber pads to prevent the vacuum bag film from being punctured by the edge of the module when vacuuming.

[0012] Step 6: After every 3 layers of prepreg are laid, vacuum is applied once. After the skin layer is laid, the internal assembly of the blade is completed, and then the mold is closed and pre-pressed. After the pre-pressing is completed, the replacement lower mold block and upper mold block are removed, the blade tip iron is installed, the blade tip iron forming block is pushed in, and then the blade is heated and cured.

[0013] Step 7: After the blade is formed and cured, open the upper mold, take out the molded blade, grind and remove the glue nodules on the blade surface, and check the surface quality.

[0014] Furthermore, in step 1, the movable block is made of metal, and the upper and lower mold movable blocks are 50mm shorter than the original iron pre-pressed movable block in the chord direction of the blade, that is, the vertical side of the movable block is 50mm away from the outer edge of the blade forming mold.

[0015] Furthermore, the cleaning agent in step 2 is anhydrous ethanol or acetone.

[0016] Furthermore, in step 2, at least 15 minutes of drying time is required between the application of the two layers of release agent.

[0017] Furthermore, in step 4, the prepreg sheet is rolled out firmly with a rolling pin during the laying process to prevent wrinkles and bridging of the prepreg sheet.

[0018] Furthermore, the vacuuming time in step 6 shall not be less than 0.5 hours.

[0019] Furthermore, in step 6, the vacuum level is no greater than -0.085 MPa.

[0020] Furthermore, step 6, which involves completing the internal assembly of the blade, specifically involves installing the joint filler block, main beam, polyurethane foam, and counterweight box into place.

[0021] Technical effect

[0022] Installing this set of replacement movable blocks on the blade forming mold satisfies the normal process of composite blade skin layup, while also meeting the vacuuming requirements during skin layup. During the pre-pressing of the upper and lower forming molds of the composite blade, it also meets the process requirement of pre-pressing the recess required for the blade tip cladding onto the blade body surface. After the upper and lower forming molds are closed and pre-pressed, this set of replacement movable blocks is removed, the blade tip cladding is placed into the pre-pressed recess on the blade body, and then another set of cladding forming movable blocks is installed to complete the bonding and curing of the blade tip cladding. The bonded blade tip cladding exhibits bonding strength that meets process requirements, shows no abnormalities upon tapping, and smoothly transitions with the blade body without any step differences. Attached Figure Description

[0023] Figure 1 Schematic diagram of the installation of the propeller lower mold and movable block;

[0024] Figure 2 Schematic diagram of the installation of mold and movable block on the propeller blade;

[0025] Figure 3 This method is illustrated in the flowchart.

[0026] Figure 4 Diagram illustrating the process of making a vacuum bag;

[0027] Among them: 1-lower mold for blade forming, 2-lower mold block, 3-upper mold for blade forming, 4-upper mold block, 5-vacuum bag. Detailed Implementation

[0028] 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.

[0029] 1. Using the pre-pressed steel block as a sample, replicate a set of replacement blocks. This set of replacement block fixtures consists of upper and lower parts. The upper block is installed in the upper mold of the paddle forming, and the lower block is installed in the lower mold of the paddle forming. This set of blocks is made of steel, and the surface roughness of the block surface is required to be 0.8, with a surface accuracy of ±0.1mm. This set of blocks is inserted into the paddle forming mold, forming a complete paddle molding cavity with the mold. The vertical side of the block is 50mm from the outer edge of the paddle forming mold. The part of the block surface that forms the cavity has a boss of about 0.5mm, creating a step difference with the surrounding cavity surface. Figure 1 As shown;

[0030] 2. 15mm from the edge of the cavity, the upper surface of the movable block has a flow groove with a radius of R5 to guide the glue flowing out during the blade curing process, preventing it from filling gaps. The vertical side of the movable block has a recess ≥30mm high, ≥70mm wide, and ≥38mm deep for easy manual lifting. The vertical side of the movable block is 50mm from the outer edge of the blade forming mold. When making the vacuum bag on the blade forming mold, putty strips are adhered to the "concave" cavity formed by the blade forming mold at this movable block position, completely covering all gaps (i.e., leakage points) formed by the movable block inside the vacuum bag. Figure 4 As shown.

[0031] 3. Preparation of the blade forming mold. Remove any lumps from the blade forming mold. Clean the surface of the mold cavity with anhydrous ethanol or acetone to remove oil stains. After drying, use masking tape to isolate the area where the putty strip will be placed. Apply three thin layers of release agent to the mold surface using a clean cloth. Each layer should be applied in one direction, avoiding circular motions. Allow at least 15 minutes between each layer of release agent. When applying the next layer, apply it perpendicular to the previous layer to ensure complete coverage.

[0032] 4. Lay the prepreg according to the blade process instructions and layup book requirements, then vacuum and compact the prepreg. Remove the paper tape on the blade forming mold, paste putty strips on the protected areas, cut the vacuum bag film according to the size of the blade forming mold, and make a vacuum bag on the surface of the blade forming mold. At the position of the movable block, paste strips are attached to the "concave" cavity of the blade forming mold to cover all gaps (i.e., air leakage points) formed by the movable block inside the vacuum bag. The vertical side of the movable block is 50mm away from the outer edge of the blade forming mold. After placing the putty strips, sufficient width and space can be reserved to place the breathable felt and rubber pad. At the same time, the vacuum bag needs to be pleated several times at this point to reserve enough space for the vacuum bag and prevent the vacuum bag film from being punctured by the edge of the module when vacuuming.

[0033] 5. During vacuuming, place three vacuum nozzles inside the vacuum bag membrane, inserting one of them into a vacuum gauge to check the vacuum level inside the bag. The vacuuming time should be no less than 0.5 hours, and the vacuum level should not exceed -0.085 MPa. After the vacuum is removed, the vacuum level should not drop by more than 0.02 MPa within 10 minutes.

[0034] 6. After the coating is completed, the blade is closed and cured. After the blade is removed from the mold, the surface quality of the blade is inspected. If there are no white spots or air holes on the surface, it means that the air bubbles between the blade layers have been removed during the molding process and the vacuum degree meets the process requirements.

[0035] 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 for maintaining vacuum in composite blade bonding, characterized in that, Includes the following steps: Step 1: Using the pre-compression movable block of the ladle as a sample, a set of replacement movable blocks is replicated. This set of replacement movable blocks consists of an upper mold movable block and a lower mold movable block, which are installed in the upper and lower molds of the paddle forming process, respectively. Step 2: Remove the lumps from the blade forming mold, use a cleaning agent to wipe the surface of the tooling cavity to remove oil stains, and after drying, use masking tape to isolate the place where the putty strip is placed. Apply three thin layers of release agent to the mold surface using a clean wiping method. Each layer should be applied in one direction. When applying the next layer of release agent, it should be applied in a direction perpendicular to the previous layer to ensure that the release agent can completely cover the previous layer. Step 3: After applying release agent to the replacement lower mold block and upper mold block in the same manner, install them onto the paddle forming mold; Step 4: Lay the prepreg according to the blade process instructions and layup book requirements. First, lay two layers of glass cloth prepreg on the iron-clad part of the mold as a backing cloth. Then, lay the first layer of carbon fiber prepreg according to the laser projection data line. After the first layer is laid, make a vacuum bag on the surface of the blade forming mold and vacuum and compact it. Step 5: Remove the paper tape from the blade forming mold, stick putty strips to the protected area, cut the vacuum bag film according to the size of the blade forming mold, and stick the putty strips to the concave cavity of the blade forming mold at the position of the movable block, covering all the gaps formed by the movable block inside the vacuum bag. The vertical side of the movable block is 50mm away from the outer edge of the blade forming mold. After placing the putty strips, leave enough width and space to place the breathable felt and rubber pad to prevent the vacuum bag film from being punctured by the edge of the module when vacuuming. Step 6: After every 3 layers of prepreg are laid, vacuum is applied once. After the skin layer is laid, the internal assembly of the blade is completed, and then the mold is closed and pre-pressed. After the pre-pressing is completed, the replacement lower mold block and upper mold block are removed, the blade tip iron is installed, the blade tip iron forming block is pushed in, and then the blade is heated and cured. Step 7: After the blade is formed and cured, open the upper mold, take out the molded blade, grind and remove the glue nodules on the blade surface, and check the surface quality.

2. The method for maintaining vacuum in composite blade installation according to claim 1, characterized in that, In step 1, the movable block is made of metal. The upper and lower mold movable blocks are 50mm shorter than the original iron pre-pressed movable block in the chord direction of the blade, that is, the vertical side of the movable block is 50mm away from the outer edge of the blade forming mold.

3. The method for maintaining the vacuum degree of composite blade laying according to claim 2, characterized in that, The cleaning agent in step 2 is anhydrous ethanol or acetone.

4. The method for maintaining the vacuum degree of composite blade laying according to claim 3, characterized in that, In step 2, at least 15 minutes of drying time is required between the application of the two layers of release agent.

5. The method for maintaining the vacuum degree of composite blade laying according to claim 4, characterized in that, In step 4, the prepreg sheet is rolled out firmly with a rolling pin to prevent wrinkles and bridging.

6. The method for maintaining the vacuum degree of composite blade laying according to claim 5, characterized in that, The vacuuming time in step 6 shall not be less than 0.5 hours.

7. The method for maintaining the vacuum degree of composite blade laying according to claim 6, characterized in that, In step 6, the vacuum level shall not exceed -0.085 MPa.

8. The method for maintaining the vacuum degree of composite blade laying according to claim 7, characterized in that, Step 6, which involves completing the internal assembly of the blade, specifically involves installing the joint filler block, main beam, polyurethane foam, and counterweight box into place.

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