A method of injection molding a carbon fiber / silicone resin composite

Abstract

The patent relates to a kind of carbon fiber / silicone resin composite injection molding method, comprising the following steps: using vacuum pump to carry out multiple bubble removal treatment to glue;Maintain the vacuum environment in mould, glue is injected into mould, and injection pressure is 0.12-0.18MPa;When the amount of injection reaches 40-70% of the capacity of mould, remove the vacuum condition;When the glue outlet of mould has glue overflow, corresponding valve is closed, until all glue outlets overflow;After closing all glue outlet valves, keep injection pressure, open one of the glue outlet valves to discharge bubble, close the ball valve without bubble discharge;The same operation is carried out to adjacent glue outlet valve, until all the ball valves of glue outlet are discharged, and pressure maintaining treatment is carried out after closing all the glue outlet valves.Compared with maintaining vacuum condition all the time, partial vacuum condition can more effectively reduce the generation of pore defect, and the apparent quality of test piece after molding is obviously improved, and the internal quality of test piece is also significantly improved.

Description

Technical Field

[0001] This patent relates to the field of resin composite materials technology, specifically to an injection molding method for carbon fiber / silicone resin composite materials. Background Technology

[0002] In recent years, the aerospace field has developed at an increasingly rapid pace, and the upgrade cycle of solid rocket engines has become shorter and shorter. However, the insulation materials used have not been updated accordingly with the upgrade of solid rocket engines.

[0003] The high-temperature ablation resistance of the insulation materials in solid rocket motors is extremely important, as it directly affects the success of the launch. The end cap constitutes a large proportion of the insulation material, resulting in high cost and stringent requirements for resistance to high-temperature erosion. To improve the ablation resistance of the end cap, composite material reinforcement is employed.

[0004] Composite materials are a new type of material characterized by high specific strength, specific modulus, low density, and customizable design, and are widely used in aerospace, automotive manufacturing, medical devices, and other fields. Composite materials mainly consist of a matrix material and a reinforcement. Matrix materials are classified into resin matrices, metal matrices, and ceramic matrices. Currently, resin-matrix composite materials are widely used in the aerospace field.

[0005] Silicone resin as the continuous phase and carbon fiber as the reinforcing material have been applied in the aerospace field as special materials resistant to high-temperature ablation. However, the molding of silicone resin / carbon fiber composites often results in defects such as insufficient bonding and porosity, which significantly reduces mechanical properties, ablation resistance, and stability. How to reduce porosity and insufficient bonding in silicone resin / carbon fiber composites remains a pressing problem to be solved. Summary of the Invention

[0006] This invention provides a method for preparing silicone resin / carbon fiber composite materials by partially introducing vacuum conditions during the injection process, thereby reducing the generation of pores in the composite material.

[0007] The technical solution adopted in this invention is: an injection molding method for carbon fiber / silicone resin composite materials, comprising the following steps:

[0008] S1. Use a vacuum pump to perform multiple defoaming treatments on the adhesive compound;

[0009] S2. Maintain a vacuum environment inside the mold and inject glue into the mold at an injection pressure of 0.12-0.18MPa. Remove the vacuum condition when the amount of glue injected reaches 40-70% of the mold capacity. The mold outlet is equipped with a valve. When glue overflows from the mold outlet, close the corresponding valve until glue overflows from all outlets.

[0010] S3. After closing all the glue outlet valves, maintain the glue injection pressure, then open one of the glue outlet valves to purge bubbles until no more bubbles are discharged, and close the ball valve where no bubbles are discharged; perform the same operation on the adjacent glue outlet valves until all the glue outlet ball valves have purged bubbles, and then close all the glue outlet valves to maintain pressure.

[0011] Furthermore, in step S3, after closing all dispensing valves, the dispensing pressure is maintained for 10-20 minutes.

[0012] Furthermore, the holding time for step S3 is 10-20 minutes.

[0013] Furthermore, step S4 is included: curing at 130-170℃ for 2-5 hours, followed by demolding.

[0014] Furthermore, the valve at the dispensing port is a ball valve, which is threadedly connected to the dispensing port.

[0015] Furthermore, in step S2, the vacuum level inside the mold is maintained at -0.50 to -0.90 bar.

[0016] Furthermore, the adhesive comprises phenyl vinyl silicone resin and a platinum catalyst.

[0017] The present invention also provides a carbon fiber / silicone resin composite material, which is prepared by the above-described preparation method.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] Vacuum assistance during conventional injection molding can improve the problem of insufficient glue and porosity in samples. However, this invention has found that full vacuum assistance during the injection process cannot completely solve the problem of insufficient glue and porosity. Compared with maintaining vacuum conditions throughout the process, partially maintaining vacuum conditions can more effectively reduce the generation of porosity and insufficient glue defects. That is, maintaining vacuum in the first half of the injection process and removing vacuum conditions in the second half significantly improves the appearance quality of the molded specimen and also significantly enhances the internal quality of the specimen.

[0020] This invention releases the glue outlets sequentially during the degassing operation, which is more effective than opening all the glue outlets at once, resulting in specimens without defects inside or out. Attached Figure Description

[0021] Figure 1 This is a flowchart of the injection molding process of the present invention;

[0022] Figure 2 The diagram shows the apparent quality and internal quality of Example 1;

[0023] Figure 3The diagram shows the apparent quality and internal quality of Example 2;

[0024] Figure 4 The diagram shows the apparent quality and internal quality of Comparative Example 1.

[0025] Figure 5 The diagram shows the apparent quality and internal quality of Comparative Example 2.

[0026] Figure 6 The diagram shows the apparent quality and internal quality of Comparative Example 3.

[0027] Symbol explanation: 1-sample, 2-mold, 3-sealing ring, 4-handle. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0029] Example 1

[0030] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0031] The specific steps are as follows:

[0032] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0033] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0034] Injection: Injection tests were conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level was maintained at -0.50 bar, and the injection pressure was adjusted to 0.15 MPa for injection. The vacuum was removed when the injection volume reached 40% (400g) of the mold capacity. Ball valves were installed at the mold's outlets; when material overflowed from the outlets, the corresponding ball valves were closed until all outlets overflowed.

[0035] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 10 minutes. Then, open one outlet ball valve to degas until no more bubbles are discharged. Close the ball valve that no more bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been degassed. After degassing, close all outlet ball valves and hold the pressure for 20 minutes.

[0036] Curing: The curing temperature is 150℃ and the curing time is 4 hours.

[0037] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0038] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0039] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0040] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0041] Example 2

[0042] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0043] The specific steps are as follows:

[0044] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0045] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0046] Injection: Injection tests were conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level was maintained at -0.90 bar, and the injection pressure was adjusted to 0.16 MPa for injection. The vacuum was removed when the injection volume reached 70% (700g) of the mold capacity. Ball valves were installed at the mold's outlets; when material overflowed from the outlets, the corresponding ball valves were closed until all outlets overflowed.

[0047] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 20 minutes. Then, open one outlet ball valve to degas until no more bubbles are discharged. Close the ball valve from which no bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been degassed. After degassing, close all outlet ball valves and hold the pressure for 10 minutes.

[0048] Curing: The curing temperature is 150℃ and the curing time is 4 hours.

[0049] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0050] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0051] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0052] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0053] Example 3

[0054] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0055] The specific steps are as follows:

[0056] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0057] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0058] Injection: Injection tests were conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level was maintained at -0.80 bar, and the injection pressure was adjusted to 0.17 MPa for injection. The vacuum was removed when the injection volume reached 60% (600g) of the mold capacity. Ball valves were installed at the mold's outlets; when material overflowed from the outlets, the corresponding ball valves were closed until all outlets overflowed.

[0059] Pressure holding and bubble removal: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 15 minutes. Then, open one outlet ball valve to remove bubbles until no more bubbles are discharged. Close the ball valve from which no bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been de-bubbled. After de-bubbling, close all outlet ball valves and hold the pressure for 15 minutes.

[0060] Curing: The curing temperature is 160℃ and the curing time is 3 hours.

[0061] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0062] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0063] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0064] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0065] Example 4

[0066] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0067] The specific steps are as follows:

[0068] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0069] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0070] Injection: Injection tests were conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level was maintained at -0.70 bar, and the injection pressure was adjusted to 0.15 MPa for injection. The vacuum was removed when the injection volume reached 50% (500g) of the mold capacity. Ball valves were installed at the mold's outlets; when material overflowed from the outlets, the corresponding ball valves were closed until all outlets overflowed.

[0071] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 18 minutes. Then, open one outlet ball valve to degas until no more bubbles are discharged. Close the ball valve that no more bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been degassed. After degassing, close all outlet ball valves and hold the pressure for 12 minutes.

[0072] Curing: The curing temperature is 140℃ and the curing time is 5 hours.

[0073] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0074] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0075] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0076] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0077] Comparative Example 1

[0078] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0079] The specific steps are as follows:

[0080] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0081] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0082] Injection: An injection test was conducted using a pressure tank at a pressure of 0.15 MPa. When glue overflowed from the mold outlet, the corresponding ball valve was closed until glue overflowed from all outlets.

[0083] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 18 minutes. Then, open one outlet ball valve to degas until no more bubbles are discharged. Close the ball valve that no more bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been degassed. After degassing, close all outlet ball valves and hold the pressure for 12 minutes.

[0084] Curing: The curing temperature is 150℃ and the curing time is 4 hours.

[0085] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0086] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0087] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0088] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0089] Comparative Example 2

[0090] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0091] The specific steps are as follows:

[0092] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0093] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0094] Injection: Injection tests are conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level is maintained at -0.50 bar, and the injection pressure is adjusted to 0.15 MPa for injection. When glue overflows from the mold outlet, the vacuum auxiliary conditions are removed, and the corresponding ball valve is closed until glue overflows from all outlets.

[0095] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 18 minutes. Then, open one outlet ball valve to degas until no more bubbles are discharged. Close the ball valve that no more bubbles are discharged. Repeat the same operation for adjacent outlet ball valves until all outlet ball valves have been degassed. After degassing, close all outlet ball valves and hold the pressure for 12 minutes.

[0096] Curing: The curing temperature is 150℃ and the curing time is 4 hours.

[0097] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0098] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0099] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0100] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0101] Comparative Example 3

[0102] Silicone resin formulation: Component A (99 wt% phenyl vinyl silicone resin) + Component B (1 wt% platinum catalyst)

[0103] The specific steps are as follows:

[0104] Ingredients: Ingredients are prepared according to the silicone resin formulation requirements, and the mixture is stirred using a disperser to ensure uniform mixing.

[0105] Defoaming: The resin is defoamed using an oil-free vacuum pump. Defoaming is performed in multiple stages. The next round of defoaming can be carried out when no more bubbles are generated on the surface of the resin.

[0106] Injection: Injection tests were conducted using a pressure tank, with an oil-free vacuum pump providing a vacuum environment. The vacuum level was maintained at -0.70 bar, and the injection pressure was adjusted to 0.15 MPa for injection. The vacuum was removed when the injection volume reached 50% (500g) of the mold capacity. Ball valves were installed at the mold's outlets; when material overflowed from the outlets, the corresponding ball valves were closed until all outlets overflowed.

[0107] Pressure holding and degassing: When glue overflows from all outlets, close all outlet ball valves and maintain the injection pressure for 18 minutes. Then, open all outlet ball valves to degas until no more bubbles are discharged. After degassing, close all outlet ball valves and hold the pressure for 12 minutes.

[0108] Curing: The curing temperature is 150℃ and the curing time is 4 hours.

[0109] Demolding: Remove the connecting bolts on the mold and demold using the anti-top screw holes.

[0110] Apparent data acquisition: The apparent quality of the samples is acquired using a digital camera.

[0111] Machining: Using CNC machine tools to mill the design allowance of the sample.

[0112] Internal data acquisition: Use a digital camera to capture the internal quality of the sample after machining.

[0113] The embodiments and comparative examples of the present invention employ the following methods: Figure 2-6 The mold shown is equipped with a sealing ring and a handle. After the rubber material is formed in the mold, it is demolded to obtain a sample.

[0114] The apparent quality and internal quality of the samples prepared in Examples 1 and 2 are as follows: Figure 2 , Figure 3 As shown, there are no pores or missing adhesive on the sample surface, nor are there any missing adhesive inside. This indicates that vacuum-assisted application does not result in missing adhesive inside or outside the sample during certain periods.

[0115] The apparent quality and internal quality of the sample prepared in Comparative Example 1 are as follows: Figure 4 As shown, the sample surface exhibits pores and insufficient adhesive, and the interior also shows insufficient adhesive. This indicates that insufficient adhesive is prone to occur without vacuum assistance.

[0116] The apparent quality and internal quality of the sample prepared in Comparative Example 2 are as follows: Figure 5 As shown, the sample surface exhibits pores and insufficient adhesive, and the interior also shows insufficient adhesive. This indicates that using vacuum assistance throughout the process easily leads to insufficient adhesive.

[0117] The apparent quality and internal quality of the sample prepared in Comparative Example 3 are as follows: Figure 6 As shown, a small amount of preform lacks adhesive on the sample surface, but there is no adhesive deficiency inside. This indicates that opening all dispensing ports at once during the degassing process can easily lead to surface adhesive deficiency.

[0118] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included.

Claims

1. A method for injection molding carbon fiber / silicone resin composite materials, characterized in that, Including the following steps: S1. Use a vacuum pump to perform multiple defoaming treatments on the adhesive compound; S2. Maintain a vacuum environment inside the mold and inject glue into the mold; remove the vacuum condition when the amount of glue injected reaches 40-70% of the mold capacity; the mold outlet is equipped with a valve, and when glue overflows from the mold outlet, close the corresponding valve until glue overflows from all outlets. S3. After closing all the glue outlet valves, maintain the glue injection pressure, then open one of the glue outlet valves to purge bubbles until no more bubbles are discharged, and close the ball valve where no bubbles are discharged; perform the same operation on the adjacent glue outlet valves until all the glue outlet ball valves have purged bubbles, and then close all the glue outlet valves to maintain pressure.

2. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, In step S3, after closing all dispensing valves, maintain the dispensing pressure for 10-20 minutes.

3. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, The pressure holding time in step S3 is 10-20 minutes.

4. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, It also includes step S4: curing at 130-170℃ for 2-5 hours, and then demolding.

5. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, The valve at the dispensing port is a ball valve, which is threadedly connected to the dispensing port.

6. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, In step S2, the vacuum level inside the mold is maintained at -0.50 to -0.90 bar.

7. The injection molding method for a carbon fiber / silicone resin composite material according to claim 1, characterized in that, The adhesive comprises phenyl vinyl silicone resin and a platinum catalyst.

8. A carbon fiber / silicone resin composite material, characterized in that, It is produced by the injection molding method described in claim 4.

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