A method for improving the uniformity of the pressure in a bag during autoclave molding of a composite article

Abstract

This invention discloses a method for improving the pressure uniformity within a vacuum bag during the autoclave molding process of composite material parts, belonging to the technical field of autoclave molding of composite material parts. The method includes the following steps: after sequentially laying a release cloth, a release film, and a breathable felt on the surface of the preform inside the mold, a glass fiber material is placed on the surface of the breathable felt and in the remaining area around the mold; subsequently, a vacuum nozzle is positioned and brought into contact with the glass fiber material. By placing the glass fiber material at specific locations, the pressure within the vacuum bag can be effectively improved. Even under high temperature and high pressure, the pressure within the vacuum bag at different distances from the vacuum nozzle can remain consistent, preventing false vacuum phenomena during the curing process. This ensures that the pressure experienced by the part is controllable and consistent throughout the curing process, thereby ensuring good product quality. Furthermore, the glass fiber material can be reused, which helps save manufacturing costs.

Description

Technical Field

[0001] This invention relates to the field of autoclave molding technology for composite material parts, and more specifically, to a method for improving the uniformity of pressure inside the bag during the autoclave molding process of composite material parts. Background Technology

[0002] Composite materials possess high specific strength, high specific modulus, fatigue resistance, and ablation resistance, and are relatively lightweight, leading to their widespread application in aerospace, transportation, automotive, and sports and leisure fields. With advancements in production technology, composite material parts are becoming increasingly larger and more complex, resulting in a growing number of problems. One particularly prominent issue is the uneven pressure within the autoclave during the curing process of large parts formed in autoclaves, which creates a false vacuum.

[0003] During the curing process of the molded parts, high temperatures and pressures are usually required. Under these conditions, the air-conducting material is easily compressed, resulting in a significant decrease in its air-conducting performance, or even the loss of its air-conducting function. Traditional solutions to this problem typically involve changing the specifications of the breathable felt, such as using a more breathable felt, or increasing the number of layers of breathable felt. However, all of these methods significantly increase manufacturing costs.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the uniformity of pressure inside the bag during the autoclave molding process of composite material parts, so as to solve or improve the above-mentioned technical problems.

[0006] This application can be implemented as follows:

[0007] This application provides a method for improving the uniformity of pressure inside a bag during the autoclave molding process of composite material parts, comprising the following steps: after sequentially laying a release cloth, a release film and a breathable felt on the surface of the preform inside the mold, a glass fiber material is placed on the surface of the breathable felt and in the remaining area around the mold; then a vacuum nozzle is arranged and brought into contact with the glass fiber material.

[0008] In an optional embodiment, the glass fiber material includes glass fiber fabric or glass fiber mesh.

[0009] In an optional embodiment, the glass fiber material is arranged in multiple layers.

[0010] In an optional embodiment, the width of the glass fiber material is 5-10 cm.

[0011] In an optional embodiment, glass fiber material is arranged at intervals of 1-1.5m along the width and / or length of the breathable felt.

[0012] In an optional embodiment, the glass fiber material is distributed in a grid pattern on the surface of the breathable felt.

[0013] In an optional embodiment, the glass fiber material on the surface of the breathable felt is arranged in an overlapping manner at the intersections of the grid.

[0014] In an optional embodiment, the preparation of the preform includes: cutting the material according to the preset layup angle and number of layers of the preform, then laying it layer by layer on a mold, pre-extracting it, and forming the preform;

[0015] The material used for feeding is prepreg.

[0016] In an optional implementation, after arranging the vacuum nozzle, a sealing strip is placed in a preset position, a bag is made, and then cured.

[0017] In an optional embodiment, the curing temperature is 120-180℃ and the curing pressure is ≥3 bar.

[0018] The beneficial effects of this application include:

[0019] By incorporating fiberglass materials on the surface of the breathable felt and in the allowance area around the mold, the pressure of the vacuum bag can be effectively improved. Even under high temperature and high pressure, the pressure inside the vacuum bag at different distances from the vacuum nozzle can be kept consistent, preventing false vacuum phenomena during the curing process. This ensures that the pressure on the part is controllable and consistent throughout the curing process, thereby ensuring good product quality. Furthermore, the fiberglass materials can be reused, which helps save manufacturing costs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure of the process components provided in this application;

[0022] Figure 2 This is a schematic diagram of one method of laying glass fiber materials in this application.

[0023] Icons: 1-Mold; 2-Preform; 3-Sealing strip; 4-Release cloth; 5-Isolation film; 6-Breathable felt; 7-Fiberglass material; 8-Vacuum bag film. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] The method for improving the uniformity of pressure inside the bag during the autoclave molding process of composite parts provided in this application will be described in detail below.

[0026] Reference Figure 1 This application proposes a method for improving the uniformity of pressure inside a bag during the hot autoclave molding process of composite parts, comprising the following steps: after sequentially laying a release cloth 4, a release film 5 and a breathable felt 6 on the surface of the preform 2 inside the mold 1, a glass fiber material 7 is placed on the surface of the breathable felt 6 and the remaining area around the mold 1; then a vacuum nozzle is arranged and made to contact the glass fiber material 7.

[0027] The preparation of the preform 2 may include: cutting the material according to the preset layup angle and number of layers of the preform 2, then laying it layer by layer on the mold 1, pre-extracting it, and forming the preform 2.

[0028] The material used in this application is a prepreg. A prepreg is an assembly made by impregnating a resin matrix with continuous fibers or fabric under strictly controlled conditions. The prepreg used in this application can be any prepreg commonly used in the art, and will not be further limited or listed here.

[0029] Pre-evacuation conditions are set according to the prepreg used, and pre-evacuation can make the multiple layers of prepreg adhere firmly to each other. In some embodiments, pre-evacuation can control the vacuum degree inside the bag at 600-850 mbar, and the pre-evacuation time can be 5-15 minutes.

[0030] In this application, the release cloth 4, the release film 5, and the breathable felt 6 can all be selected and set with reference to the prior art.

[0031] For reference, the composite material parts in this application may be composite materials of conventional dimensions in the art. Alternatively, they may be large-sized composite material parts, for example, the dimensions of a composite material part may be 5m (length) × 3m (width).

[0032] It is important to emphasize that ensuring uniform pressure within the vacuum bag during hot pressing is more challenging for large-sized composite parts compared to those of conventional sizes. This application creatively incorporates glass fiber material 7 on the surface of the breathable felt 6 and in the allowance area around the mold 1. Glass fiber material 7 possesses excellent air conductivity, effectively improving the pressure within the vacuum bag. Even under high temperature and pressure, it maintains consistent pressure within the vacuum bag at different distances from the vacuum nozzle, preventing false vacuum during curing. This ensures controllable and consistent pressure on the part throughout the curing process, preventing the air-conducting material from being compacted and losing its air-conducting function under high temperature and pressure, thus ensuring good product quality. Furthermore, the glass fiber material 7 used in this application can be reused, which helps save manufacturing costs.

[0033] During autoclave curing, the loose, breathable felt plays a crucial role in ensuring uniform pressure within the bag. In high-temperature, high-pressure molding, pressure and temperature can cause the loose, breathable felt to become compacted and dense, even losing its air-permeable properties. Therefore, several times more or better air-permeable felt is typically used than usual during high-temperature, high-pressure molding to ensure the entire curing process proceeds smoothly, increasing the cost of auxiliary materials and operations in the manufacturing process. Compared to breathable felt, fiberglass fabrics or mesh fabrics offer excellent air permeability and, being less loose and easily compacted, exhibit even better air permeability under high temperature and pressure.

[0034] For reference, the aforementioned glass fiber material 7 may, by way of example but not limitation, include glass fiber fabric or glass fiber mesh, etc.

[0035] In this application, the glass fiber material 7 can be arranged in one layer or multiple layers. In some preferred embodiments, the glass fiber material 7 is arranged in multiple layers.

[0036] For example, the number of layers of the glass fiber material 7 can be 2 to 5, such as 2, 3, 4, or 5 layers. In addition, other numbers of layers, such as 5 or more, can be arranged according to actual needs.

[0037] In some embodiments, the width of the glass fiber material 7 can be 5-10cm, such as 5cm, 5.5cm, 6cm, 6.5cm, 7cm, 7.5cm, 8cm, 8.5cm, 9cm, 9.5cm or 10cm, or any other value within the range of 5-10cm.

[0038] In some embodiments, glass fiber material 7 is arranged at regular intervals along the width direction of the breathable felt 6. In some embodiments, glass fiber material 7 is arranged at regular intervals along the length direction of the breathable felt 6. In some embodiments, glass fiber material 7 is arranged at regular intervals along both the length and width directions of the breathable felt 6.

[0039] For example, the spacing between the glass fiber materials 7 can be 1-1.5m, such as 1m, 1.1m, 1.2m, 1.3m, 1.4m or 1.5m.

[0040] In addition, it is not ruled out that, depending on the actual situation, glass fiber material 7 may be applied to the surface of the breathable felt 6 in other forms.

[0041] In some preferred embodiments, the glass fiber material 7 is distributed in a mesh pattern on the surface of the breathable felt 6 (e.g., Figure 2 Furthermore, the glass fiber material 7 on the surface of the breathable felt 6 is arranged in an overlapping manner at the intersections of the grid. By adopting an overlapping arrangement to form a parallel structure, it is more conducive to the uniformity of pressure throughout the bag.

[0042] After the glass fiber material 7 is arranged, the vacuum nozzle is set. In this application, by setting the glass fiber material 7 on the surface of the breathable felt 6 and in the allowance area around the mold 1, and by making the vacuum nozzle contact and conduct with the glass fiber material 7, the glass fiber material 7 can guide air in a timely and effective manner when the vacuum nozzle is working, maintaining the pressure in the vacuum bag at different distances from the vacuum nozzle to be consistent, so that the workpiece is subjected to uniform pressure in the bag during the hot pressing process.

[0043] Furthermore, after arranging the vacuum nozzles, the sealing strips 3 are placed in the preset positions to form a bag, so that the vacuum bag is sealed with the mold 1, and then cured.

[0044] After bag making, such as Figure 1 The entire process assembly includes: a mold 1 and, from bottom to top, a preform 2, a release cloth 4, a release film 5, a breathable felt 6, and a glass fiber material 7 (preferably multiple layers) arranged on the mold 1. The allowance area around the mold 1 is also provided with glass fiber material 7 (preferably multiple layers). A sealing strip 3 is placed between the vacuum bag film 8 and the mold 1 to seal the entire process assembly. The vacuum nozzle can be placed anywhere in the non-part-forming area, provided that it meets the specifications, as long as it ensures that the vacuum nozzle is in contact with the glass fiber material 7 and can conduct gas.

[0045] It should be noted that the specific process conditions used for curing are related to the prepreg used, and this part can be set with reference to existing technology.

[0046] In some alternative implementations, the curing temperature can be 120-180℃, such as 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, or 180℃. The curing pressure is ≥3 bar, such as 3 bar, 3.5 bar, 4 bar, 4.5 bar, 5 bar, 5.5 bar, 6 bar, 6.5 bar, or 7 bar.

[0047] In some typical implementations, the curing conditions can be as follows: pressurize to 6.0 bar at a rate of 0.5 bar / min, and simultaneously heat to 120-130°C at a rate of 2°C / min, hold for 130-150 min; then heat to 180°C and hold for 180-200 min.

[0048] Once curing is complete, demolding, testing, and warehousing can be carried out.

[0049] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0050] The following is some product information used in the examples and comparative examples:

[0051] Release cloth 4: Commercially available R60S.

[0052] Separator 5: Commercially available WL5200B.

[0053] Breathable felt 6: Commercially available WF330.

[0054] Fiberglass mesh: Commercially available, 2 mm thick.

[0055] Fiberglass fabric: Commercially available EWR400.

[0056] Example 1

[0057] This embodiment provides a method for improving the pressure uniformity inside the bag during the autoclave molding process of large (5m×3m) parts, including the following steps:

[0058] Step (1): Cut the material according to the preset layup angle and number of layers of the precast body 2.

[0059] The ply angles are set as follows: [45 / 0-45 / 90] 3S It has 24 floors.

[0060] The material used for cutting is prepreg, which is commercially available, carbon fiber reinforced epoxy resin prepreg.

[0061] Step (2): Lay the mold layer by layer according to the preset number of layers, and perform pre-extraction every 6 layers. The pre-extraction conditions include: vacuum degree inside the bag of 850 mbar and pre-extraction time of 10 min.

[0062] Step (3): After the paving is completed, release cloth 4, release film 5 and breathable felt 6 are laid on the precast body 2 in sequence.

[0063] Step (4): Place two layers of 10cm wide fiberglass mesh in the margin area around mold 1.

[0064] Step (5): On the surface of the breathable felt 6, place two layers of 10cm wide fiberglass mesh every 1.5m along its length and width directions. The fiberglass mesh placed in the length and width directions overlap at their intersections without separating.

[0065] Step (6): In the margin area of ​​mold 1, a vacuum nozzle is arranged every 2m. The vacuum nozzle is placed on top of the glass fiber mesh and can conduct gas.

[0066] Step (7): Place sealing strip 3 to make bags, and test the vacuum degree inside the bag. It is qualified if it reaches more than 900mbar and drops no more than 20mbar within 10 minutes.

[0067] Step (8): According to the characteristics of the prepreg used above, cure according to the following curing parameters: pressurize to 6.0 bar at a rate of 0.5 bar / min; heat to 120°C at a rate of 2°C / min and hold for 130 min; then heat to 180°C and hold for 180 min.

[0068] Step (9): Demold, inspect and put into storage the cured parts.

[0069] Example 2

[0070] This embodiment provides a method for improving the pressure uniformity inside the bag during the autoclave molding process of large (5m×3m) parts, including the following steps:

[0071] Step (1): Cut the material according to the preset layup angle and number of layers of the precast body 2.

[0072] The ply angles are set as follows: [45 / 0-45 / 90] 3S It has 24 floors.

[0073] The material used for cutting is prepreg, which is commercially available, carbon fiber reinforced epoxy resin prepreg.

[0074] Step (2): Lay the mold layer by layer according to the preset number of layers, and perform pre-extraction every 6 layers. The pre-extraction conditions include: vacuum degree inside the bag of 850 mbar and pre-extraction time of 10 min.

[0075] Step (3): After the paving is completed, release cloth 4, release film 5 and breathable felt 6 are laid on the precast body 2 in sequence.

[0076] Step (4): Place 5 layers of 5cm wide fiberglass mesh in the margin area around mold 1.

[0077] Step (5): On the surface of the breathable felt 6, place 5 layers of 5cm wide fiberglass mesh every 1m along its length and width. The fiberglass mesh placed in the length and width directions overlap at the intersections and are not separated.

[0078] Step (6): In the margin area of ​​mold 1, a vacuum nozzle is arranged every 2m. The vacuum nozzle is placed on top of the glass fiber mesh and can conduct gas.

[0079] Step (7): Place sealing strip 3 to make bags, and test the vacuum degree inside the bag. It is qualified if it reaches more than 900mbar and drops no more than 20mbar within 10 minutes.

[0080] Step (8): According to the characteristics of the prepreg used above, cure according to the following curing parameters: pressurize to 5.0 bar at a rate of 0.5 bar / min; simultaneously heat to 130°C at a rate of 2°C / min and hold for 150 min; then heat to 180°C and hold for 200 min.

[0081] Step (9): Demold, inspect and put into storage the cured parts.

[0082] Example 3

[0083] This embodiment provides a method for improving the pressure uniformity inside the bag during the autoclave molding process of large (5m×3m) parts, including the following steps:

[0084] Step (1): Cut the material according to the preset layup angle and number of layers of the precast body 2.

[0085] The ply angles are set as follows: [45 / 0-45 / 90] 3S It has 24 floors.

[0086] The material used for cutting is prepreg, which is commercially available, carbon fiber reinforced epoxy resin prepreg.

[0087] Step (2): Lay the mold layer by layer according to the preset number of layers, and perform pre-extraction every 6 layers. The pre-extraction conditions include: vacuum degree inside the bag of 850 mbar and pre-extraction time of 10 min.

[0088] Step (3): After the paving is completed, release cloth 4, release film 5 and breathable felt 6 are laid on the precast body 2 in sequence.

[0089] Step (4): Place four layers of glass fiber fabric, each 7.5 cm wide, in the margin area around mold 1.

[0090] Step (5): On the surface of the breathable felt 6, place 4 layers of glass fiber fabric with a width of 7.5cm every 1.2m along its length and width directions. The glass fiber fabrics placed in the length and width directions overlap at the intersection and are not separated.

[0091] Step (6): In the margin area of ​​mold 1, a vacuum nozzle is arranged every 2m. The vacuum nozzle is placed on the glass fiber fabric and can conduct gas.

[0092] Step (7): Place sealing strip 3 to make bags, and test the vacuum degree inside the bag. It is qualified if it reaches more than 900mbar and drops no more than 20mbar within 10 minutes.

[0093] Step (8): According to the characteristics of the prepreg used above, cure according to the following curing parameters: pressurize to 7.0 bar at a rate of 0.5 bar / min; simultaneously heat to 125°C at a rate of 2°C / min and hold for 140 min; then heat to 180°C and hold for 190 min.

[0094] Step (9): Demold, inspect and put into storage the cured parts.

[0095] Comparative Example 1

[0096] This comparative example provides a method for improving the pressure uniformity inside the bag during the autoclave molding process of large (5m×3m) parts, including the following steps:

[0097] Step (1): Cut the material according to the preset layup angle and number of layers of the precast body 2.

[0098] The ply angles are set as follows: [45 / 0-45 / 90] 3S It has 24 floors.

[0099] The material used for cutting is prepreg, which is commercially available, carbon fiber reinforced epoxy resin prepreg.

[0100] Step (2): Lay the mold layer by layer according to the preset number of layers, and perform pre-extraction every 6 layers. The pre-extraction conditions include: vacuum degree inside the bag of 850 mbar and pre-extraction time of 10 min.

[0101] Step (3): After the paving is completed, release cloth 4, release film 5 and breathable felt 6 are laid on the precast body 2 in sequence.

[0102] Step (4): In the margin area of ​​mold 1, a vacuum nozzle is arranged every 2m. The vacuum nozzle is placed on top of the glass fiber mesh and can conduct gas.

[0103] Step (5): Place sealing strip 3 to make bags, and test the vacuum degree inside the bag. It is qualified if it reaches more than 900mbar and drops no more than 20mbar within 10 minutes.

[0104] Step (6): According to the characteristics of the prepreg used above, cure according to the following curing parameters: pressurize to 6.0 bar at a rate of 0.5 bar / min; simultaneously heat to 120°C at a rate of 2°C / min and hold for 130 min; then heat to 180°C and hold for 180 min.

[0105] Step (7): Demold, inspect and put into storage the cured parts.

[0106] That is, the difference between this comparative example and Example 1 is that steps (4) and (5) in Example 1 are not included, that is, glass fiber mesh is not provided in the allowance area around the mold 1 and on the surface of the breathable felt 6.

[0107] Test case

[0108] Testing of the pressure inside the bag during the curing process of the parts in Example 1 revealed that the pressure tended to decrease after the temperature exceeded 150°C, but remained around -600 mbar throughout the curing process. Pressure testing of the parts in Examples 2-4 during curing also showed that after pressurization, the pressure inside the bag decreased after the temperature exceeded 150°C, but remained between -400 mbar and -850 mbar throughout the curing process. However, when treated using the method in Comparative Example 1, the pressure inside the bag decreased more rapidly after the temperature exceeded 140°C, and reached a positive value of approximately 200 mbar when the temperature reached around 180°C. This indicates that the method provided in this application can effectively improve the uniformity of pressure inside the bag during the autoclave molding of large parts.

[0109] In summary, by providing glass fiber material 7 on the surface of the breathable felt 6 and in the allowance area around the mold 1, this application can effectively improve the pressure of the vacuum bag. Even under high temperature and high pressure, the pressure inside the vacuum bag at different distances from the vacuum nozzle can be kept consistent, preventing the phenomenon of false vacuum during the curing process. This ensures that the pressure on the part is controllable and consistent throughout the curing process, thereby ensuring that the part has good product quality. Furthermore, the glass fiber material 7 can be reused, which helps to save manufacturing costs.

[0110] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 improving the uniformity of the pressure in a bag during autoclave molding of a composite article, characterized in that, Includes the following steps: After laying the release cloth, release film and breathable felt in sequence on the surface of the preform inside the mold, glass fiber material is set on the surface of the breathable felt and in the remaining area around the mold. Then, a vacuum nozzle is positioned and brought into contact with the glass fiber material; the glass fiber material is distributed in a grid pattern on the surface of the breathable felt; the glass fiber material on the surface of the breathable felt is placed in an overlapping manner at the intersections of the grid pattern.

2. The method according to claim 1, characterized in that, The glass fiber materials include glass fiber fabrics or glass fiber mesh.

3. The method according to claim 1, characterized in that, The glass fiber material is arranged in multiple layers.

4. The method according to claim 1, characterized in that, The width of the glass fiber material is 5-10 cm.

5. The method according to claim 4, characterized in that, The glass fiber material is arranged at intervals of 1-1.5m along the width and / or length of the breathable felt.

6. The method according to claim 1, characterized in that, The preparation of the preform includes: cutting the material according to the preset layup angle and number of layers of the preform, then laying it layer by layer on the mold, pre-extracting it, and forming the preform; The material used for feeding is prepreg.

7. The method according to claim 1, characterized in that, After arranging the vacuum nozzle, place the sealing strip in the preset position, make the bag, and then cure it.

8. The method according to claim 7, characterized in that, Curing pressure ≥ 3 bar.

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