Method for improving surface quality of pre-preg at split pressure equalizing pad joint position

Abstract

The application discloses a method for improving the surface quality of pre-preg at the joint position of split pressure equalizing pads, which comprises the following steps: preparation of a protective pad, placement of a pressure equalizing pad, filling of the butt joint gap of the pressure equalizing pad and encapsulation and curing. The method needs to prepare a protective pad with certain rigidity, high-temperature resistance and soft edges in advance. After the pre-preg is laid, a wet strippable cloth is laid on the surface of the pre-preg at the joint position of the pressure equalizing pad, the protective pad is placed, the pressure equalizing pad is covered, a thermoplastic film filling material is filled in the joint of the pressure equalizing pad above the protective pad, the pre-preg honeycomb filled with the rubber supporting material is laid on a large-curvature preforming tool, and encapsulation and curing are carried out in a hot press tank.

Description

Technical Field

[0001] The invention relates to the technical field of composite material molding, 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 aerospace manufacturing. Given the extreme and demanding environments in which these parts operate, extremely stringent standards for surface quality are imposed to ensure uncompromising reliability and performance. Part surfaces must be extremely smooth and flat; even minor imperfections such as wrinkles, surface depressions, scratches, or other defects can negatively impact the overall performance of the part. Therefore, pressure pads are often used during manufacturing to ensure even pressure on the composite material during curing, resulting in a high-quality surface.

[0003] However, when dealing with situations where there are equalizing pressure 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 unevenness may cause some defects on the prepreg surface, thereby affecting the overall material properties and structural stability. If the gaps are not handled properly, it may cause defects on the prepreg surface, further exacerbating these problems. Improper gap handling will not only lead to unevenness on the prepreg surface, 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 where there are equalizing pressure 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 present invention aims to provide a method for improving the surface quality of prepreg at the seam of a split-flap pressure-equalizing pad. This method aims to address the problem of surface unevenness at the seam of the pressure-equalizing pad by finely treating the seam to improve the surface quality of the prepreg. This method not only effectively avoids surface defects that may occur in traditional processes, but is also simple to operate and low-cost, offering high practical value and potential for widespread adoption.

[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:

[0006] Step A: preparing a protective gasket;

[0007] Step A1: Place a metal sheet strip on a clean flat work surface, apply thermoplastic film along the length of the metal sheet strip along its edges, and secure with high-temperature resistant tape.

[0008] Step A2: After paving, use isolation film, breathable station, vacuum bag and sealing strip to package;

[0009] Step A3: After the package is completed, use a curing oven to cure it. After the curing is completed, the protective gasket is demoulded and cleaned;

[0010] Step B: Place the pressure equalizing pad;

[0011] Step B1: Lay the prepreg on the forming tooling and place a pressure equalizing pad on the surface of the prepreg. The butt gap of the pressure equalizing pad is 5mm to 10mm. After marking the position of the butt gap of the pressure equalizing pad, remove the pressure equalizing pad.

[0012] Step B2: Laying at least one layer of wet peelable fabric in the center of the prepreg surface at the marked position; overlapping multiple layers of wet peelable fabric to form a gradient edge;

[0013] 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;

[0014] Step B4: Align the edge of the pressure equalizing pad with the marked seam position again and fix it, and perform vacuum pre-compaction;

[0015] 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;

[0016] Step C: Encapsulation and curing: Use isolation film, breathable felt, vacuum bag, and sealing strips for encapsulation, and evacuate to maintain the seal; the encapsulated parts and molding tooling are sent to the autoclave for curing and molding; after taking out of the tank, demoulding is carried out to obtain high-quality parts.

[0017] 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.

[0018] Preferably, two layers of wet-peelable cloth are laid in the center of the prepreg surface at the marked position; the width of the first layer of wet-peelable cloth is 50mm-100mm, the width of the second layer of wet-peelable cloth is 30mm-80mm, and the two layers of wet-peelable cloth form a gradual edge.

[0019] Preferably, the pre-compacting vacuum in step B4 is not less than -60 KPa, and the time is not less than 5 minutes.

[0020] Preferably, the filling thickness of the thermoplastic film filler is 0.5mm to 1.5mm higher than that of the pressure equalizing pad; after filling, the thermoplastic film filler is fixed with a high-temperature resistant tape at intervals of 40mm to 80mm along the filling length direction.

[0021] Preferably, during the packaging process in step C, the vacuum is drawn to at least -80 KPa. After the vacuum value stabilizes, the vacuum is turned off, and the vacuum value in the bag does not drop by more than 5 KPa within 5 minutes.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention places a protective gasket with a certain degree of rigidity, high temperature resistance, and soft edges at the bottom of the pressure equalizing pad, and simultaneously fills the gaps in the pressure equalizing pad with a thermoplastic film filler, thereby avoiding quality problems such as surface step differences and wrinkles on parts caused by uneven pressure at the pressure equalizing pad seams. The advantages of this method are:

[0024] 1. Significantly enhances the smoothness of the prepreg surface and effectively prevents defects in the splicing area;

[0025] 2. This method is simple to operate and can be quickly applied on the production line, thus improving production efficiency;

[0026] 3. Improvements in prepreg surface quality directly enhance product performance and reliability;

[0027] 4. The method of the present invention has good versatility and is applicable to composite materials of various sizes and shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the protective gasket provided by the present invention;

[0029] Figure 2 It is a schematic diagram of the placement of the pressure equalizing pad provided by the present invention.

[0030] 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

[0031] The present invention is further described 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 greatly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0032] 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", etc., indicating the orientation or position relationship, are based on the orientation or position relationship 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 operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0034] In addition, the features, operations, and characteristics described in this specification may be combined in any appropriate manner to form various embodiments. Similarly, the steps or actions described in the method may be reordered in a manner readily apparent to those skilled in the art. Therefore, the various sequences in the specification and drawings are provided for clarity of description of a particular embodiment and are not mandatory unless otherwise specified. Example

[0035] 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:

[0036] Step A: Prepare the protective gasket 100, such as Figure 1 As shown;

[0037] Step A1: Lay the metal sheet strip 10 on a clean flat tooling, lay the thermoplastic film 20 along the lengthwise edges of the metal sheet strip 10, and secure it with a high-temperature resistant tape to prevent the thermoplastic film 20 from slipping;

[0038] Step A2: After paving, use isolation film, breathable station, vacuum bag and sealing strip to package;

[0039] Step A3: After the packaging 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;

[0040] Step B: Place the pressure equalizing pad, such as Figure 2 As shown;

[0041] Step B1: Lay the prepreg 1 on the forming tool 2, and place a pressure equalizing pad 3 on the surface of the prepreg 1. The butt gap of the pressure equalizing pad 3 is 5mm to 10mm. After marking the butt joint position of the pressure equalizing pad 3, remove the pressure equalizing pad 3;

[0042] Step B2: Laying at least one layer of wet peelable fabric 4 on the center of the surface of the prepreg 1 at the marked position; laying multiple layers of wet peelable fabric 4 in an overlapping manner to form a gradient edge;

[0043] 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;

[0044] Step B4: Align the edge of the pressure equalizing pad 3 with the marked seam position again and fix it, and perform vacuum pre-compaction, with the pre-compaction vacuum not less than -60KPa, and the time is not less than 5 minutes;

[0045] 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~1.5mm higher than the pressure equalizing pad; after filling is completed, use high-temperature resistant tape to fix the thermoplastic film filler 5 at intervals of 40mm~80mm along the filling length direction to prevent the material from scattering and displacement; 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.

[0046] Step C: Encapsulation and curing: Use isolation film, breathable felt, vacuum bag, and sealing strips for encapsulation, and evacuate to maintain the seal. During the encapsulation process, the vacuum should be 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 encapsulated parts and molding tooling are sent to the autoclave for curing and molding. After taking out of the can, demoulding is carried out to obtain high-quality parts.

[0047] 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 degree of rigidity and high temperature resistance. The thermoplastic film 20 must be usable at temperatures between 120°C and 200°C and have a certain degree of flexibility and adhesion at room temperature.

[0048] Specifically, two layers of wet peelable cloth 4 are laid in the center of the prepreg 1 surface 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 gradient edge.

[0049] This method employs a rigid, high-temperature-resistant, and soft-edged protective gasket placed at the bottom of the pressure-equalizing pad, while also filling the gaps between the pressure-equalizing pads with a thermoplastic film filler. This method avoids surface unevenness, wrinkles, and other quality issues caused by uneven pressure at the pad seams. Advantages of this method include: 1. It significantly enhances the prepreg surface flatness, effectively preventing defects at the joints; 2. It is simple to operate and can be quickly applied on the production line, improving production efficiency; 3. The improved prepreg surface quality directly enhances product performance and reliability; 4. The method is highly versatile and applicable to composite parts of various sizes and shapes.

[0050] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians 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 seam 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 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; Step B1: Lay the prepreg (1) on the forming tool (2), and place a pressure equalizing pad (3) on the surface of the prepreg (1), wherein the butt joint gap of the pressure equalizing pad (3) is 5 mm to 10 mm. After marking the butt joint position of the pressure equalizing pad (3), remove the pressure equalizing pad (3); Step B2: laying multiple layers of wet peelable fabric (4) in the center of the surface of the prepreg (1) at the marked position; the multiple layers of wet peelable fabric (4) are laid out 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 seam position again and fix it, and perform vacuum pre-compaction; Step B5: cutting thermoplastic film filler (5) to fill the butt joint gaps between adjacent pressure equalizing pads (3) according to the butt joint gap size of the pressure equalizing pads (3); Step C: Encapsulation and curing: Use isolation film, breathable felt, vacuum bag, and sealing strips for encapsulation, and evacuate to maintain the seal; the encapsulated parts and molding tooling are sent to the autoclave for curing and molding; after taking out of the tank, demoulding is carried out to obtain high-quality parts.

2. A method for improving the surface quality of prepreg at the seam of a split pressure equalizing pad according to 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. The method for improving the surface quality of prepreg at the seam position of a split pressure equalizing pad according to claim 1, characterized in that: Two layers of wet peelable cloth (4) are laid in the center of the surface of the prepreg (1) at the marked position; the width of the first layer of wet peelable cloth (4) is 50mm to 100mm, the width of the second layer of wet peelable cloth (4) is 30mm to 80mm, and the two layers of wet peelable cloth (4) form a gradient edge.

4. The method for improving the surface quality of prepreg at the seam of a split pressure equalizing pad according to 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. The method for improving the surface quality of prepreg at the seam position of a split pressure equalizing pad according to 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 adhesive tape at intervals of 40 mm to 80 mm along the filling length direction.

6. The method for improving the surface quality of prepreg at the seam of a split pressure equalizing pad according to 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.

Images