Method for carrying out hot-pressing post-treatment on automatically-laid workpiece by using silicone rubber vacuum bag

Abstract

The invention relates to a method for carrying out hot-pressing post-treatment on an automatic laying workpiece by using a silicone rubber vacuum bag, and belongs to the technical field of composite material forming preparation. According to the method, an automatic laying technology is utilized, carbon fiber reinforced resin matrix composite prepreg is laid on a mold layer by layer, and an automatic laying workpiece is prepared; taking out the workpiece, sequentially wrapping the workpiece with demolding cloth and a breathable film, uniformly coating and packaging the surfaces of the workpiece and the vacuum nozzle with liquid silicone rubber, and curing the silicone rubber to obtain a silicone rubber vacuum bag; and placing the part packaged by the silicone rubber vacuum bag in an autoclave, and removing the silicone rubber and auxiliary materials to obtain the automatic laying part after hot pressing post-treatment. All-around wrapping and packaging of the inner surface and the outer surface of a complex geometric structure workpiece can be achieved, the mechanical strength of the automatically-laid workpiece is improved after hot pressing treatment, and meanwhile the surface quality and smoothness of the product can be guaranteed.

Description

Technical Field

[0001] The present invention relates to a method for hot pressing and post - treating an automatically placed part using a silicone rubber vacuum bag, belonging to the technical field of composite material forming and preparation. Background Art

[0002] The automatic placement forming technology can achieve high - consistency placement quality, ensure the accuracy and stability of the formed parts, is suitable for the forming of complex geometric shapes, control the material consumption, improve the material utilization rate, and can meet the application requirements of structural parts such as wings and fuselages. Therefore, it has attracted much attention in the field of aerospace materials. However, there are still some problems with this technology. Compared with hot - pressed formed parts, the mechanical properties and strength of the parts prepared by the automatic placement forming technology are often insufficient and cannot meet the application requirements. Heat pressing post - treatment is required to improve the relevant properties before they can be used.

[0003] In the hot pressing post - treatment process, high - temperature films are usually used as vacuum bags to wrap the parts. However, the high - temperature films are brittle themselves, not easy to be laid on the inner and outer surfaces of parts with complex shapes, and are prone to cracking. During the process of laying such products, the vacuum bag often needs to be spliced, and the surface quality and finish of the parts are easily damaged during the vacuum - pumping hot pressing post - treatment process. At the same time, the vacuum bag made of high - temperature film is a consumable and cannot be recycled.

[0004] The silicone rubber vacuum bag is a liquid silicone rubber before curing, which can completely coat the inner and outer surfaces of the parts, is not restricted by the complex geometric structure and shape of the parts themselves, has a controllable thickness during the coating process, is easy to operate, and can wrap the parts to form a complete closed cavity. After curing, the silicone rubber has good toughness and certain strength and will not easily break during the subsequent vacuum - pumping process; the silicone rubber itself has poor tear - resistance and can be easily torn, which is convenient for removal after hot pressing post - treatment, can be recycled, and can be reused in the hot pressing post - treatment process of parts of the same size next time, saving costs. Therefore, the silicone rubber vacuum bag can be used to optimize the process of hot pressing post - treating automatically placed parts. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method for hot pressing and post - treating an automatically placed part using a silicone rubber vacuum bag. The method has a simple operation process, low manufacturing cost, and the obtained silicone rubber vacuum bag can be recycled.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] The present invention uses liquid silicone rubber to replace the traditional film - type vacuum bag. The liquid silicone rubber can completely cover the entire surface of the part. By coating different masses of silicone rubber on the surface of the part, the thickness of each position of the vacuum bag can be controlled, and a silicone rubber vacuum bag with a certain strength can be formed after curing.

[0008] Technical solution: A method for post-heat pressing treatment of an automatically laid part using a silicone rubber vacuum bag, comprising the following steps:

[0009] Step 1: Use an automatic laying device to lay a carbon fiber reinforced resin matrix composite prepreg on the upper layer of the mold of the automatically laid part to prepare the automatically laid part;

[0010] Step 2: Wrap the automatically laid part with a release cloth and a breather film that have been treated with a release agent in sequence, and evenly coat the automatically laid part and the vacuum nozzle with liquid silicone rubber on the outermost layer;

[0011] Step 3: Connect the vacuum pipeline to the vacuum nozzle, perform post-treatment using an autoclave after vacuuming, and finally remove the silicone rubber and auxiliary materials on the surface of the part to obtain the heat-pressed and post-treated automatically laid part.

[0012] The liquid silicone rubber is HY-E640 silicone rubber, which is a two-component liquid silicone material.

[0013] The two-component liquid silicone material is cured by mixing equal masses of component A and component B colloidal solutions, where component A contains a platinum catalyst and component B contains a curing agent.

[0014] Preparation method of liquid silicone rubber: Weigh and mix the A and B two-component rubber materials in a ratio of 1:1, stir evenly with a glass rod, then place the mixed colloidal solution in a vacuum dryer for degassing treatment, and pour the bubble-free colloidal solution onto the surface of the part wrapped with auxiliary materials by guiding with a glass rod, and cure at room temperature for 24 hours or cure at 60-70°C for 2-3 hours to realize the forming preparation of the silicone rubber vacuum bag.

[0015] Method for removing the silicone rubber and auxiliary materials on the surface of the part: Use a wallpaper knife to cut a gap between the surface of the mold and the vacuum bag, and then tear off the entire silicone rubber vacuum bag by hand. The auxiliary materials can be directly torn off by hand.

[0016] The structure and size of the automatically laid part are prepared according to a preset program.

[0017] The geometric structure of the automatically laid part is a complex curved surface or a special-shaped structure, and its laying path and size are controlled by a preset program.

[0018] The prepreg is a carbon fiber / epoxy resin or glass fiber / epoxy resin system.

[0019] The process parameters of the post-heat pressing treatment are: vacuum degree ≤ 100 Pa, heat pressing temperature 120-180°C, pressure 0.5-1.5 MPa, heat preservation and pressure holding time 1-4 hours.

[0020] The beneficial effects of the present invention are as follows:

[0021] In the present invention, the liquid silicone rubber can completely coat the inner and outer surfaces of the entire workpiece, meet the application requirements of workpieces with complex structures and shapes, and does not require splicing and pasting of the vacuum bag, ensuring high quality of the workpiece surface while being simple to operate and greatly reducing costs.

[0022] In the present invention, the cured silicone rubber vacuum bag has high strength, will not break during vacuum pumping, and has poor tear resistance. After hot pressing and post-treatment, the silicone rubber vacuum bag can be easily removed. At the same time, the silicone rubber vacuum bag in the present invention can be recycled and reused to meet the hot pressing and post-treatment operations of the same workpiece. Description of the Drawings

[0023] Figure 1 is a schematic diagram of the operation of hot pressing and post-treating an automatically placed workpiece using a silicone rubber vacuum bag.

[0024] Figure 2 is Figure 1 a schematic view observed in the a direction in

[0025] Wherein: 1 - Automatically placed workpiece, 2 - Release cloth, 3 - Breathable film, 4 - Flat mold, 5 - Silicone rubber vacuum bag, 6 - Vacuum nozzle. Detailed Embodiment

[0026] The technical solutions in the present invention will be described in detail below with reference to the drawings in the present invention:

[0027] A method for hot pressing and post-treating an automatically placed workpiece using a silicone rubber vacuum bag includes the following steps:

[0028] Step 1: Use an automatic placement device to lay a carbon fiber reinforced resin matrix composite prepreg on the upper layer of the mold of the automatically placed workpiece to prepare the automatically placed workpiece.

[0029] Step 2: Wrap the automatically placed workpiece sequentially with a release cloth and a breathable film treated with a release agent to facilitate subsequent demolding operations. The outermost layer is evenly coated with liquid silicone rubber on the automatically placed workpiece and the vacuum nozzle.

[0030] Step 3: Connect the vacuum pipeline to the vacuum nozzle, perform post-treatment using a autoclave after vacuum pumping, and finally remove the silicone rubber and auxiliary materials on the surface of the workpiece to obtain the hot-pressed and post-treated automatically placed workpiece.

[0031] The liquid silicone rubber is HY-E640 silicone rubber, which is a two-component liquid silicone material with low viscosity, good fluidity, and easy to operate.

[0032] The two-component liquid silicone material is cured by mixing equal masses of component A and component B colloidal solutions. Component A contains a platinum catalyst and component B contains a curing agent.

[0033] Preparation method of liquid silicone rubber: Weigh and mix the A and B two-component rubber materials in a ratio of 1:1, stir evenly with a glass rod, then place the mixed rubber solution in a vacuum dryer for degassing treatment, and pour the bubble-free rubber solution onto the surface of the workpiece wrapped with auxiliary materials by guiding with a glass rod. Cure at room temperature for 24 hours or cure at 60-70 °C for 2-3 hours to realize the forming preparation of the silicone rubber vacuum bag.

[0034] Method for removing the silicone rubber and auxiliary materials on the surface of the workpiece: Use a wallpaper knife to cut a gap between the surface of the mold and the vacuum bag, and then tear off the entire silicone rubber vacuum bag by hand. The auxiliary materials can be directly torn off by hand.

[0035] The structure and size of the automatically laid workpiece are prepared according to a preset program.

[0036] The geometric structure of the automatically laid workpiece is a complex curved surface or a special-shaped structure, and its laying path and size are controlled by a preset program.

[0037] The prepreg is a carbon fiber / epoxy resin or glass fiber / epoxy resin system.

[0038] The process parameters of the post heat pressing treatment are: vacuum degree ≤ 100 Pa, heat pressing temperature 120-180 °C, pressure 0.5-1.5 MPa, heat preservation and pressure holding time 1-4 hours.

[0039] Example 1:

[0040] Please refer to Figures 1 - 2 , in Example 1, in a method for post heat pressing treatment of an automatically laid workpiece using a silicone rubber vacuum bag, a release cloth 2 and a breather membrane 3 are sequentially wrapped on the surface of the automatically laid workpiece 1 and then placed on a flat mold 4. A silicone rubber vacuum bag 5 is formed by curing the liquid silicone rubber, and the workpiece 1 and the vacuum nozzle 6 are wrapped together to form a whole, which is convenient for subsequent vacuum heat pressing post-treatment operations.

[0041] The specific implementation steps of using this method are as follows:

[0042] Use an automatic laying device to prepare a glass fiber-reinforced epoxy resin automatically laid workpiece on the mold. Treat the release cloth with a release agent and then wrap it on the surface of the workpiece, and then wrap it with a breather membrane. Place the workpiece on a flat mold and reserve the position of the vacuum nozzle for subsequent vacuuming operations.

[0043] Prepare a liquid silicone rubber solution. Take 100 g of E640A glue and place it in a beaker. Use a high-speed stirrer to stir it at a speed of 1000 rpm. Slowly add 100 g of E640B glue during the stirring process. After the B glue is completely added, continue stirring for 20 minutes to ensure that the A and B glue solutions are fully mixed evenly. It can be observed that there are a large number of bubbles in the mixed glue solution. Place the beaker in a 4°C refrigerator and let it stand for 12 hours to extend the curing time of the silicone rubber while performing degassing treatment. When there are no obvious bubbles in the mixed solution, evenly coat the mixed glue solution on the automatic placement molding part wrapped with auxiliary materials and the surface of the vacuum nozzle. Place it in a room-temperature environment for curing. After 24 hours, the liquid silicone rubber is completely cured and formed, and a completely sealed silicone rubber cavity is formed outside the part and the vacuum nozzle. Connect the vacuum pipeline to the silicone rubber vacuum bag through the vacuum nozzle connection. Then place it in a autoclave, evacuate and use the autoclave for post-treatment. Finally, remove the silicone rubber and auxiliary materials on the surface of the part to obtain the automatically placed part after hot pressing post-treatment.

[0044] Example 2

[0045] Use an automatic placement device to prepare a carbon fiber reinforced epoxy resin automatically placed part on a mold. After treating the release cloth with a release agent, wrap it around the surface of the part and then use a breathable film to wrap it. Place the part on a flat mold and reserve the position of the vacuum nozzle for subsequent vacuum pumping operations.

[0046] Prepare a liquid silicone rubber solution. Take 100 g of E640A glue and place it in a beaker. Use a high-speed stirrer to stir it at a speed of 1000 rpm. Slowly add 100 g of E640B glue during the stirring process. After the B glue is completely added, continue stirring for 20 minutes to ensure that the A and B glue solutions are fully mixed evenly. Place the beaker in a 4°C refrigerator and let it stand for 12 hours to extend the curing time of the silicone rubber while performing degassing treatment. When there are no obvious bubbles in the mixed solution, evenly coat the mixed glue solution on the automatic placement molding part wrapped with auxiliary materials and the surface of the vacuum nozzle. Place it in a room-temperature environment for curing. After 24 hours, the liquid silicone rubber is completely cured and formed, and a completely sealed silicone rubber cavity is formed outside the part and the vacuum nozzle. Connect the vacuum pipeline to the silicone rubber vacuum bag through the vacuum nozzle connection. Then place it in a autoclave, evacuate and use the autoclave for post-treatment. Finally, remove the silicone rubber and auxiliary materials on the surface of the part to obtain the automatically placed part after hot pressing post-treatment.

[0047] Comparative Example 1

[0048] The automatic placement part described above has the same preparation process as that in Example 1. The post-treatment operation of hot pressing the glass fiber-reinforced epoxy resin sheet is carried out using a traditional medium-temperature vacuum bag. The specific operation is to wrap the part with a release cloth and a breather membrane in sequence, then use a medium-temperature vacuum bag for encapsulation, leaving the position of the vacuum nozzle reserved. Then it is placed in a autoclave, and after vacuum pumping, the autoclave is used for post-treatment. Finally, the vacuum bag and auxiliary materials on the surface of the part are removed to obtain the automatically placed part after hot pressing post-treatment.

[0049] Comparative Example 2

[0050] The automatic placement part described above has the same preparation process as that in Example 2. The post-treatment operation of hot pressing the carbon fiber-reinforced epoxy resin sheet is carried out using a traditional medium-temperature vacuum bag. The specific operation is to wrap the part with a release cloth and a breather membrane in sequence, then use a medium-temperature vacuum bag for encapsulation, leaving the position of the vacuum nozzle reserved. Then it is placed in a autoclave, and after vacuum pumping, the autoclave is used for post-treatment. Finally, the vacuum bag and auxiliary materials on the surface of the part are removed to obtain the automatically placed part after hot pressing post-treatment.

[0051] Effect verification

[0052] The automatically placed parts after hot pressing post-treatment prepared in the above Examples 1 and 2 and Comparative Examples 1 and 2 are used as test samples, and their bending properties and interlaminar shear properties are measured to evaluate their mechanical properties. The test results are the average values of six tests, as shown in Table 1.

[0053] Table 1

[0054] Test sample Flexural strength / MPa Flexural modulus / GPa Interlaminar shear strength / MPa Example 1 377 24.2 81.1 Comparative Example 1 378 24.3 82.3 Example 2 889 62.1 84.3 Comparative Example 2 838 62.7 83.8

[0055] Table 2

[0056]

[0057]

[0058] It can be seen from the test results in Table 1 and Table 2 that compared with the properties of the parts after hot pressing post-treatment using a traditional vacuum bag, the glass transition temperature of the parts after hot pressing post-treatment using a silicone rubber vacuum bag is similar, and the test results of the mechanical properties are equivalent, proving that this post-treatment process can prepare composite material components with good quality.

[0059] In summary, the silicone rubber vacuum bag prepared by using liquid silicone rubber in the present invention is used for hot pressing post-treatment of an automatic placement part, thereby improving the internal quality and performance of the part itself. The fluidity of the liquid silicone rubber ensures that it can completely cover the inner and outer surfaces of a part with a complex geometric shape, and forms a sealed cavity after curing, which is convenient for subsequent vacuum pumping operations. Based on the characteristics of high strength and poor tear resistance of silicone rubber, the vacuum bag prepared by using silicone rubber is not easily broken during the vacuum pumping process, and is easy to tear off and remove after the hot pressing post-treatment, can be recycled and reused, is simple to operate, reduces the production and manufacturing cost while improving the efficiency, and can be applied to the hot pressing post-treatment of automatic placement parts.

Claims

1. A method for post - heat - pressing treatment of an automatic placement part using a silicone rubber vacuum bag, characterized in that, It includes the following steps: Step 1: Use an automatic placement device to lay carbon fiber reinforced resin matrix composite prepreg on the upper layer of the mold of the automatically placed part to prepare the automatically placed part; Step 2: Wrap the automatically placed part successively with a release cloth and a breather membrane treated with a release agent, and evenly coat the automatically placed part and the vacuum nozzle with liquid silicone rubber on the outermost layer; Step 3: Connect the vacuum pipeline to the vacuum nozzle, perform post-treatment with a autoclave after vacuuming, and finally remove the silicone rubber and auxiliary materials on the surface of the part to obtain the automatically placed part after hot pressing post-treatment.

2. The method for post-heat pressing treatment of an automatically laid part using a silicone rubber vacuum bag according to claim 1, wherein The liquid silicone rubber is HY-E640 silicone rubber, which is a two-component liquid silicone material.

3. The method for post-heat pressing treatment of an automatically laid part using a silicone rubber vacuum bag according to claim 1, characterized in that, The two-component liquid silicone material is cured by mixing equal masses of component A and component B glue solutions, where component A contains a platinum catalyst and component B contains a curing agent.

4. The method for post-heat pressing treatment of an automatic placement part using a silicone rubber vacuum bag according to claim 1, characterized in that, Preparation method of liquid silicone rubber: Weigh and mix the A and B two-component rubber materials in a ratio of 1:1, stir evenly with a glass rod, then place the mixed glue solution in a vacuum dryer for degassing treatment, pour the bubble-free glue solution onto the surface of the part wrapped with auxiliary materials by guiding with a glass rod, and cure at room temperature for 24 hours or cure at 60-70 °C for 2-3 hours to realize the forming preparation of the silicone rubber vacuum bag.

5. The method for post - heat - pressing treatment of an automatically laid - up part using a silicone rubber vacuum bag according to claim 1, wherein, Method for removing the silicone rubber and auxiliary materials on the surface of the part: Use a utility knife to cut a gap between the mold surface and the vacuum bag, and then tear off the whole silicone rubber vacuum bag by hand. The auxiliary materials can be directly torn off by hand.

6. The method for post - heat - pressing treatment of an automatically laid - up part using a silicone rubber vacuum bag according to claim 1, wherein The structure and dimensions of the automatically placed part are prepared according to a preset program.

7. The method for post - heat - pressing treatment of an automatically laid - up part using a silicone rubber vacuum bag according to claim 1, wherein, The geometric structure of the automatically placed part is a complex curved surface or a special-shaped structure, and its placement path and dimensions are controlled by a preset program.

8. The method for post - heat - pressing treatment of an automatically laid - up part using a silicone rubber vacuum bag according to claim 1, characterized in that, The prepreg is a carbon fiber / epoxy resin or glass fiber / epoxy resin system.

9. The method for post-heat pressing treatment of an automatically laid part using a silicone rubber vacuum bag according to claim 1, characterized in that, The process parameters of the hot pressing post-treatment are: vacuum degree ≤ 100 Pa, hot pressing temperature 120-180 °C, pressure 0.5-1.5 MPa, heat preservation and pressure holding time 1-4 hours.

Images