Method for improving surface quality of prepreg at abutted seam position of sectioning pressure equalizing pad

Abstract

The invention discloses a method for improving the surface quality of prepreg at the abutted seam position of a split pressure-equalizing pad. The method comprises the steps of preparation of a protective gasket, placement of the pressure-equalizing pad, filling of a butt joint gap of the pressure-equalizing pad and packaging and curing. According to the method, a protective gasket with certain rigidity, high temperature resistance and soft edges needs to be prepared in advance, after prepreg laying is completed, wet strippable cloth is laid on the surface of the prepreg at the splicing seam position of the pressure equalizing pad, then the protective gasket is placed, finally, the pressure equalizing pad is covered, the splicing seam of the pressure equalizing pad above the protective gasket is filled with thermoplastic film filler, and the pressure equalizing pad is formed. And finally, paving the pre-impregnated honeycomb filled with the rubber support material on a large-curvature pre-forming tool, packaging, and feeding into an autoclave for curing.

Description

Technical Field

[0001] The invention relates to the technical field of composite material molding, and in particular to a method for improving the surface quality of prepreg at a seam position of a split pressure equalizing pad. Background Art

[0002] Composite molded parts play a vital role in the field of aviation manufacturing. Considering the application environment of these parts under extreme and harsh conditions, extremely strict standards are imposed on their surface quality to ensure that their reliability and performance are not affected. The surface of the parts must achieve extreme smoothness and flatness. Any minor flaws, such as wrinkles, surface depressions, scratches or other defects, may have a negative impact on the overall performance of the part. Therefore, during the manufacturing process, pressure pads are often used to ensure that the composite materials are evenly compressed during the curing process to obtain a high-quality surface.

[0003] However, when dealing with situations with equalizing pads for splicing, traditional technical methods usually encounter some challenges that are difficult to overcome. These challenges are mainly reflected in the unevenness of the prepreg surface at the splicing. Since it is difficult to ensure completely consistent pressure and material distribution during the splicing process, some uneven marks often appear on the prepreg surface. This uneven phenomenon may cause some defects on the prepreg surface, thereby affecting the overall material properties and structural stability. If the gap is not handled properly, it may cause defects on the prepreg surface, further aggravating these problems. Improper gap handling will not only cause the surface of the prepreg to be uneven, but may also form stress concentration points at the splicing, increasing the risk of fatigue or fracture of the material during use. Therefore, when dealing with situations with equalizing pads for splicing, more sophisticated and advanced technical methods must be adopted to ensure the uniformity of the prepreg surface and the reliability of the overall structure. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the surface quality of prepreg at the joint position of the split pressure equalizing pad, aiming to solve the problem of surface unevenness at the joint position of the pressure equalizing pad, and finely process the joint position of the pressure equalizing pad to improve the surface quality of the prepreg. This method can not only effectively avoid surface defects that may occur in traditional processes, but also is easy to operate, low cost, and has high practical value and promotion prospects.

[0005] In order to solve the above technical problems, the present invention provides a method for improving the surface quality of prepreg at the seam position of a split pressure equalizing pad, comprising the following steps: Step A: preparing a protective gasket; Step A1: Lay a metal sheet strip on a clean flat tooling, butt-jointly lay a thermoplastic film along the lengthwise edge of the metal sheet strip, and fix it with a high-temperature resistant tape; Step A2: After paving, use isolation film, breathable station, vacuum bag and sealing strip to package; Step A3: After the encapsulation is completed, use a curing oven to cure it. After the curing is completed, demould and clean the protective gasket; Step B: placing a pressure equalizing pad; Step B1: Lay the prepreg on the molding tool, and place a pressure equalizing pad on the surface of the prepreg, the butt gap of the pressure equalizing pad is 5mm-10mm, mark the butt joint position of the pressure equalizing pad, and remove the pressure equalizing pad; Step B2: Laying at least one layer of wet peelable fabric in the center of the prepreg surface at the marked position; laying multiple layers of wet peelable fabric in an overlapping manner to form a gradient edge; Step B3: Take out the pre-prepared protective gasket, apply a release agent on the surface, and place it centrally on the wet peelable cloth; Step B4: Align the edge of the pressure equalizing pad with the marked joint position again and fix it, and perform vacuum pre-compaction; Step B5: cutting thermoplastic film filler to fill the butt joint gaps between adjacent pressure equalizing pads according to the butt joint gap size of the pressure equalizing pads; Step C: Packaging and curing: use isolation film, breathable felt, vacuum bag, sealing strip for packaging, and evacuate to keep the seal; the packaged parts and molding tools are sent to the autoclave for curing and molding; after taking out of the can, demoulding is carried out to obtain high-quality parts.

[0006] Preferably, the metal foil strip has a width of 15 mm to 30 mm and a thickness of 0.1 mm to 0.25 mm.

[0007] Preferably, two layers of wet peelable cloth are laid centrally on the prepreg surface at the marked position; the first layer of wet peelable cloth is 50mm-100mm wide, the second layer of wet peelable cloth is 30mm-80mm wide, and the two layers of wet peelable cloth form a gradual edge transition.

[0008] Preferably, the pre-compacting vacuum in step B4 is not less than -60 KPa, and the time is not less than 5 minutes.

[0009] Preferably, the filling thickness of the thermoplastic film filler is 0.5 mm to 1.5 mm higher than that of the pressure equalizing pad; after the filling is completed, the thermoplastic film filler is fixed with a high temperature resistant tape at intervals of 40 mm to 80 mm along the filling length direction.

[0010] Preferably, during the packaging process in step C, the vacuum is drawn to at least -80 KPa, and after the vacuum value is stabilized, the vacuum is turned off, and the vacuum value in the bag does not drop by more than 5 KPa within 5 minutes.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention places a protective gasket with certain rigidity, high temperature resistance and soft edges at the bottom of the pressure equalizing pad, and fills the gap of the pressure equalizing pad with a thermoplastic film filler, thereby avoiding quality problems such as surface step difference and wrinkles of parts caused by uneven pressure at the joint of the pressure equalizing pad. The advantages of this method are: 1. Significantly enhance the flatness of the prepreg surface and effectively prevent defects in the splicing area; 2. This method is simple to operate and can be quickly applied on the production line, thus improving production efficiency; 3. The improvement of prepreg surface quality directly improves product performance and reliability; 4. The method of the present invention has good versatility and is applicable to composite material parts of various sizes and shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the protective gasket provided by the present invention; Figure 2 It is a schematic diagram of placing the pressure equalizing pad provided by the present invention.

[0013] In the figure: 100, protective gasket; 10, metal foil strip; 20, thermoplastic film; 1, prepreg; 2, molding tool; 3, pressure equalizing pad; 4, wet-peelable cloth; 5, thermoplastic film filler. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0015] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0016] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0017] In addition, the features, operations, and characteristics described in the specification can be combined in any appropriate manner to form various embodiments. Similarly, the steps or actions described in the method can also be adjusted in order in a manner that can be easily seen by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for the purpose of describing a certain embodiment, and are not necessarily such sequences, unless otherwise stated that a certain sequence must be followed. Example

[0018] The present invention provides a method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad, comprising the following steps: Step A: Prepare the protective gasket 100, such as Figure 1 As shown; Step A1: Lay the metal sheet strip 10 on a clean flat tooling, butt-jointly lay the thermoplastic film 20 along the lengthwise edge of the metal sheet strip 10, and fix it with a high temperature resistant tape to prevent the thermoplastic film 20 from slipping; Step A2: After paving, use isolation film, breathable station, vacuum bag and sealing strip to package; Step A3: After the encapsulation is completed, the protective gasket 100 is cured in a curing oven. After the curing is completed, the protective gasket 100 is demoulded and cleaned; Step B: Place the pressure equalizing pad, such as Figure 2 As shown; Step B1: Lay the prepreg 1 on the molding tool 2, and place a pressure equalizing pad 3 on the surface of the prepreg 1, wherein the butt gap of the pressure equalizing pad 3 is 5 mm to 10 mm, and remove the pressure equalizing pad 3 after marking the butt joint position of the pressure equalizing pad 3; Step B2: laying at least one layer of wet peelable cloth 4 in the center of the surface of the prepreg 1 at the marked position; laying multiple layers of wet peelable cloth 4 in an overlapping manner to form a gradual edge change; Step B3: Take out the pre-prepared protective gasket 100, apply a release agent on the surface, and place it centrally on the wet peelable cloth 4; Step B4: Align the edge of the pressure equalizing pad 3 with the marked joint position again and fix it, and perform vacuum pre-compaction, the pre-compaction vacuum is not less than -60Kpa, and the time is not less than 5 minutes; Step B5: According to the size of the butt joint gap of the pressure equalizing pad 3, cut the thermoplastic film filler 5 to fill the butt joint gap of the adjacent pressure equalizing pads 3; the filling thickness of the thermoplastic film filler 5 is 0.5mm to 1.5mm higher than that of the pressure equalizing pad; after the filling is completed, use high-temperature resistant tape to fix the thermoplastic film filler 5 at intervals of 40mm to 80mm along the filling length direction to prevent the material from being scattered and displaced; when using the thermoplastic film filler 5 to fill the butt joint gap of the pressure equalizing pad 3, it is necessary to ensure that the surface of the thermoplastic film filler 5 is flat and free of filling defects such as wrinkles and protrusions.

[0019] Step C: Package and solidify. Use isolation film, breathable felt, vacuum bag and sealing strip for packaging, and evacuate to keep the seal. During the packaging process, evacuate to at least -80Kpa. After the vacuum value stabilizes, turn off the vacuum. The vacuum value in the bag should not drop by more than 5Kpa within 5 minutes. The packaged parts and molding tooling are sent to the autoclave for curing and molding. After being taken out of the can, demoulding is carried out to obtain high-quality parts.

[0020] Specifically, the metal sheet strip 10 has a width of 15 mm to 30 mm and a thickness of 0.1 mm to 0.25 mm. The metal sheet strip 10 has a certain rigidity and high temperature resistance; the thermoplastic film 20 needs to be used at a temperature of 120°C to 200°C and has a certain flexibility and adhesion at room temperature.

[0021] Specifically, two layers of wet peelable cloth 4 are laid in the center of the surface of the prepreg 1 at the marked position; the first layer of wet peelable cloth 4 is 50mm-100mm wide, the second layer of wet peelable cloth 4 is 30mm-80mm wide, and the two layers of wet peelable cloth 4 form a gradual edge.

[0022] The present invention places a protective gasket with certain rigidity, high temperature resistance and soft edges at the bottom of the pressure equalizing pad, and fills the gap of the pressure equalizing pad with a thermoplastic film filler, thereby avoiding quality problems such as surface step difference and wrinkles of parts caused by uneven pressure at the joint of the pressure equalizing pad. The advantages of this method are: 1. The flatness of the prepreg surface is significantly enhanced, and defects at the joint are effectively prevented; 2. The method is simple to operate and easy to quickly apply on the production line, thereby improving production efficiency; 3. The improvement of the surface quality of the prepreg directly improves the performance and reliability of the product; 4. The method of the present invention has good versatility and is suitable for composite parts of various sizes and shapes.

[0023] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad, characterized in that: The steps include: Step A: preparing a protective gasket (100); Step A1: Lay the metal sheet strip (10) on a clean flat tooling, butt-jointly lay the thermoplastic film (20) along the lengthwise edge of the metal sheet strip (10), and fix it with a high-temperature resistant tape; Step A2: After paving, use isolation film, breathable station, vacuum bag and sealing strip to package; Step A3: After the encapsulation is completed, the encapsulation is performed using a curing furnace, and after the curing is completed, the protective gasket (100) is demoulded and cleaned; Step B: placing a pressure equalizing pad; Step B1: Lay the prepreg (1) on the molding tool (2), and place a pressure equalizing pad (3) on the surface of the prepreg (1), wherein the butt gap of the pressure equalizing pad (3) is 5 mm to 10 mm, and after marking the butt joint position of the pressure equalizing pad (3), remove the pressure equalizing pad (3); Step B2: laying at least one layer of wet peelable cloth (4) in the center of the surface of the prepreg (1) at the marked position; laying multiple layers of wet peelable cloth (4) in an overlapping manner to form a gradient edge; Step B3: Take out the pre-prepared protective gasket (100), apply a release agent on the surface, and place it centrally on the wet peelable cloth (4); Step B4: Align the edge of the pressure equalizing pad (3) with the marked joint position again and fix it, and perform vacuum pre-compaction; Step B5: cutting thermoplastic film filler (5) to fill the butt joint gaps of adjacent pressure equalizing pads (3) according to the butt joint gap size of the pressure equalizing pads (3); Step C: Packaging and curing: use isolation film, breathable felt, vacuum bag, sealing strip for packaging, and evacuate to keep the seal; the packaged parts and molding tools are sent to the autoclave for curing and molding; after taking out of the can, demoulding is carried out to obtain high-quality parts.

2. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad as claimed in claim 1, characterized in that: The metal sheet strip (10) has a width of 15 mm to 30 mm and a thickness of 0.1 mm to 0.25 mm.

3. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad as claimed in claim 1, characterized in that: Two layers of wet peelable cloth (4) are laid centrally on the surface of the prepreg (1) at the marked position; the first layer of wet peelable cloth (4) has a width of 50 mm to 100 mm, the second layer of wet peelable cloth (4) has a width of 30 mm to 80 mm, and the two layers of wet peelable cloth (4) form a gradient edge.

4. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad as claimed in claim 1, characterized in that: The pre-compaction vacuum in step B4 is not less than -60 KPa and the time is not less than 5 minutes.

5. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad as claimed in claim 1, characterized in that: The filling thickness of the thermoplastic film filler (5) is 0.5 mm to 1.5 mm higher than that of the pressure equalizing pad; after the filling is completed, the thermoplastic film filler (5) is fixed with a high temperature resistant tape at intervals of 40 mm to 80 mm along the filling length direction.

6. A method for improving the surface quality of prepreg at the joint position of a split pressure equalizing pad as claimed in claim 1, characterized in that: During the packaging process in step C, the vacuum is drawn to at least -80Kpa. After the vacuum value stabilizes, the vacuum is turned off. The vacuum value in the bag does not drop by more than 5Kpa within 5 minutes.

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