Method for connecting composite material and metal framework based on die cavities with different thicknesses

Abstract

The invention provides a connecting method for a composite material and a metal framework based on an unequal-thickness mold cavity. The connecting method comprises the steps that a mold is manufactured according to the linear shape of a composite material shell plate; manufacturing a laminated plate prefabricated body of the connecting area; manufacturing a connecting area prefabricated body; the metal framework is filled with a polyurethane core mold; laying a lower panel fiber material on the metal framework and the polyurethane core mold, and laying an upper panel fiber material on the mold; flexible fabrics are laid on the lower panel fiber material and the upper panel fiber material, the mold, the upper panel fiber material and the flexible fabrics form a first structural body, and the metal framework, the polyurethane core mold, the lower panel fiber material and the flexible fabrics form a pre-structural body; a second structural body is formed after a connecting area prefabricated body and a first core material are installed on the pre-structural body; and the second structural body is buckled on the first structural body to be integrally formed. According to the connecting method disclosed by the invention, non-uniform flow velocity of the resin during vacuum infusion can be avoided, so that the forming quality and the structural strength can be improved.

Description

Technical Field

[0001] The invention relates to the field of composite material molding, and in particular to a method for connecting a composite material and a metal skeleton based on a mold cavity of unequal thickness. Background Art

[0002] Fiber-reinforced resin-based composite materials are high-performance materials with excellent stiffness, mechanical properties, shock absorption and weight reduction effects. They are widely used in the shipbuilding field such as yachts and luxury cruise ships. In the molding process of thick composite materials, most of them involve the connection between the composite material and the metal frame structure. The connection structure and molding quality of the two directly affect the safety and stability of the overall structure.

[0003] At present, most thick composite materials containing metal frames are formed by vacuum-assisted processes. The connection area between the composite material and the metal frame is mainly formed by pre-forming a preform, and then integrated forming. The patent application number CN202210668419.9 in the prior art discloses a method for connecting an integrated composite skin and a skeleton, including the following steps: (1) processing the mold according to the structure of the skeleton; (2) laying reinforcing materials on the surface of the mold, sealing the mold, and curing and forming a U-shaped connector according to the process requirements; (3) demolding the U-shaped connector; (4) gluing and wrapping the inner cavity of the U-shaped connector on the skeleton; (5) integrally forming the outer side of the U-shaped connector with the composite skin. The method for connecting the composite skin and the skeleton mentioned in the patent is to pre-form a composite preform and then integrate the composite skin. The molding accuracy of this type of molding method is mainly controlled by the mold closing technology. When the resin is poured, the composite material is located between the metal skeleton and the mold. In addition to the pressure of the vacuum, the composite material under the metal frame is also subjected to the pressure caused by the deadweight of the metal frame. Although the gap between the composite material and the mold can be accurately controlled in the early stage of mold closing, the slight difference in the mold closing gap will cause uneven force on the composite material under the metal frame. The gaps between some composite material layers with large force are smaller, while the gaps between some composite material layers with small force are larger. The unevenness of the gap makes the mold cavity between the metal skeleton and the mold unequal in thickness, which makes the resin flow rate different during vacuum infusion. The resin is difficult to penetrate completely at the location with small gap, that is, the location with greater pressure from the metal frame, which greatly affects the molding quality and structural strength of the connection area between the composite material and the metal frame.

[0004] How to design a composite material connection area forming method based on unequal thickness mold cavities to improve the forming quality of the connection structure between composite materials and metal structures in large thickness unequal thickness mold cavities is a key issue that needs to be urgently solved in this field.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to propose a method for connecting a composite material and a metal frame based on unequal thickness mold cavities, so as to solve the problem of unequal thickness of the mold cavities between the metal frame and the mold in the prior art, which makes the resin flow rate different during vacuum infusion, and the resin is difficult to penetrate completely at the position with greater pressure from the metal frame, which greatly affects the molding quality and structural strength of the connection area between the composite material and the metal frame.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness, the method comprising the following steps:

[0009] S1. Making corresponding molds according to the composite shell plate line shape;

[0010] S2, making a laminate preform in the connection area;

[0011] S3, bonding the core material of the transition area to the laminate preform to produce a connection area preform, and reducing the thickness of the connection area preform;

[0012] S4, filling the polyurethane core mold in the metal skeleton frame;

[0013] S5. Laying the lower panel fiber material on the metal frame and the polyurethane core mold, and laying the upper panel fiber material on the mold;

[0014] S6, laying flexible fabrics on both the lower panel fiber material and the upper panel fiber material, the mold, the upper panel fiber material and the flexible fabric form a first structure, and the metal skeleton, the polyurethane core mold, the lower panel fiber material and the flexible fabric form a pre-structure;

[0015] S7, installing the connection area preform and the first core material on the preform to form a second structure;

[0016] S8, buckling the second structure onto the first structure for integrated molding;

[0017] The warp and weft weaving density of the flexible fabric is reduced by 50% to 80% compared with the upper panel fiber material and the lower panel fiber material, and the gram weight of the flexible fabric is increased by 20% to 50% compared with the upper panel fiber material and the lower panel fiber material.

[0018] Furthermore, the laying thickness of the flexible fabric is 1 to 5 mm.

[0019] Furthermore, the flexible fabric, the upper panel fiber material, and the lower panel fiber material are the same material system.

[0020] Furthermore, the flexible fabric includes a first fabric and a second fabric, the first fabric is laid on the upper panel fiber material, and the second fabric is laid on the lower panel fiber material.

[0021] Furthermore, the material of the transition region core material and the first core material is at least one of polyurethane foam, polymethacrylimide foam, polyetherimide foam, polystyrene foam, polyvinyl chloride foam, polyethylene foam and acrylonitrile-styrene foam.

[0022] Furthermore, the flexible fabric, the upper panel fiber material, and the lower panel fiber material are at least one of glass fiber, carbon fiber and aramid fiber material systems.

[0023] Furthermore, the material of the metal skeleton is at least one of steel, aluminum alloy, magnesium alloy, copper alloy and titanium alloy.

[0024] Furthermore, the mold material is at least one of metal, wood and composite material.

[0025] Furthermore, the matrix resin of the composite material or laminate preform is at least one of unsaturated polyester resin, vinyl resin, phenolic resin, epoxy resin and bismaleimide resin.

[0026] Furthermore, the molding process of the composite material or laminate preform is one of a liquid molding process, a prepreg molding process, and a hand lay-up molding process.

[0027] The present invention proposes a method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness. Compared with the prior art, the method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness according to the present invention has the following beneficial effects:

[0028] (1) The method for connecting a composite material and a metal skeleton based on a mold cavity of unequal thickness described in the present invention reduces the thickness of the preform in the connection area. On the one hand, it avoids the problem that the thickness of the preform in the connection area is too large, making it difficult for the resin to penetrate the fabric below, thereby avoiding molding defects. On the other hand, it provides a laying space for laying flexible fabrics.

[0029] (2) The present invention describes a method for connecting a composite material and a metal skeleton based on a mold cavity of unequal thickness. Flexible fabrics are laid on the lower panel fiber material and the upper panel fiber material. The flexible fabrics are easy to extend and can effectively avoid uneven gaps between the preform in the connection area and the lower panel fiber material and the upper panel fiber material, thereby avoiding uneven resin flow rate during vacuum infusion.

[0030] (3) The method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness described in the present invention is simple in method and the material is readily available, and can effectively improve the molding quality of the connection structure between the composite material and the metal structure in a mold cavity of large thickness and unequal thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic cross-sectional view of laying a composite material and a metal skeleton connection method based on unequal thickness mold cavities according to an embodiment of the present invention on a mold;

[0032] Figure 2 A schematic cross-sectional view of laying a composite material and a metal frame based on a unequal thickness mold cavity according to an embodiment of the present invention on a metal frame;

[0033] Figure 3 It is a schematic diagram of an inverted cross-section of a method for connecting a composite material and a metal skeleton based on a mold cavity of unequal thickness according to an embodiment of the present invention.

[0034] Description of reference numerals:

[0035] 1. Mold; 2. Upper panel fiber material; 3. Flexible fabric; 31. First fabric; 32. Second fabric; 4. Transition region core material; 5. Laminate preform; 6. Lower panel fiber material; 7. Polyurethane core mold; 8. Metal skeleton; 9. First core material. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The descriptions of "first", "second", etc. mentioned in the embodiments of the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0038] In the prior art, when the connection area between the composite material and the metal skeleton 8 is formed, the thickness of the mold cavity between the metal skeleton 8 and the mold 1 is not equal, which makes the resin flow rate different during vacuum infusion. The position with greater pressure from the metal skeleton 8 is difficult for the resin to penetrate completely, which greatly affects the molding quality and structural strength of the connection area between the composite material and the metal skeleton 8.

[0039] In order to solve the above technical problems, the present invention proposes a method for connecting a composite material and a metal skeleton based on a mold cavity of unequal thickness, such as Figures 1 to 3 As shown, the thickness of the preform in the connection area is thinned, and the flexible fabric 3 is laid on the lower panel fiber material 6 and the upper panel fiber material 2. The good flexibility and ductility of the flexible fabric 3 can adjust the gap between the preform in the connection area and the lower panel fiber material 6 and the upper panel fiber material 2, which can effectively improve the molding quality of the connection structure between the composite material and the metal structure in the mold cavity with large thickness and unequal thickness.

[0040] Specifically, the method for connecting the composite material and the metal skeleton based on the unequal thickness mold cavity comprises the following steps:

[0041] S1, making a corresponding mold 1 according to the composite shell plate line shape;

[0042] S2, making a connection region laminate preform 5 as a connection part between the composite material and the metal skeleton 8, which can improve the molding quality and structural strength of the connection structure between the composite material and the metal skeleton 8;

[0043] S3, bonding the transition area core material 4 to the laminate preform 5 to make a connection area preform, and reducing the thickness of the connection area preform by 1 to 5 mm. On the one hand, it avoids the connection area preform being too thick so that the resin is difficult to penetrate the fabric below and avoids molding defects; on the other hand, it provides a laying space for laying the flexible fabric 3;

[0044] S4, filling the polyurethane core mold 7 in the metal skeleton 8 frame to prepare for the formation of the connection structure between the composite material and the metal skeleton 8;

[0045] S5, laying the lower panel fiber material 6 on the metal skeleton 8 and the polyurethane core mold 7, and laying the upper panel fiber material 2 on the mold 1;

[0046] S6, laying flexible fabric 3 on both the lower panel fiber material 6 and the upper panel fiber material 2, the mold 1, the upper panel fiber material 2 and the flexible fabric 3 form a first structure, and the metal skeleton 8, the polyurethane core mold 7, the lower panel fiber material 6 and the flexible fabric 3 form a pre-structure;

[0047] During the molding process, due to the presence of the flexible fabric 3, the resin can more easily penetrate into every corner of the connection area, thereby effectively improving the molding quality and structural strength of the connection structure between the composite material and the metal skeleton 8;

[0048] S7, after installing the connection area preform and the first core material 9 on the preform, a second structure is formed to prepare for the subsequent molding process;

[0049] S8, buckling the second structure onto the first structure for integrated molding;

[0050] Among them, the warp and weft weaving density of the flexible fabric 3 is reduced by 50% to 80% compared with the upper panel fiber material 2 and the lower panel fiber material 6, and the gram weight of the flexible fabric 3 is increased by 20% to 50% compared with the upper panel fiber material 2 and the lower panel fiber material 6. This design makes the flexible fabric 3 have good flexibility and ductility, and can adjust the gap between the connection area preform and the upper panel fiber material 2 and the lower panel fiber material 6.

[0051] The method for connecting a composite material and a metal skeleton based on unequal thickness mold cavities described in the present invention, steps S1 to S8 are interrelated and inseparable, and play multiple roles: First, it can effectively avoid the unevenness of the gap between the preform in the connection area and the lower panel fiber material 6 and the upper panel fiber material 2, thereby avoiding the problem of uneven resin flow rate during vacuum infusion, and then avoiding the occurrence of molding defects. There is no lack of glue, bubbles and white spots with a diameter greater than 4 mm inside the upper and lower panel composite materials at the laminate preform 5; second, the resin can more easily penetrate into every corner of the connection area, effectively improving the molding quality and structural strength of the connection structure between the composite material and the metal skeleton 8; third, the connection method is simple, the material is easy to obtain, and the cost is low.

[0052] Specifically, the laying thickness of the flexible fabric 3 is 1-5 mm, which can reduce the production cost and ensure that it can effectively adjust the gap and improve the molding quality and structural strength of the connection structure between the composite material and the metal skeleton 8.

[0053] Specifically, the flexible fabric 3, the upper panel fiber material 2, and the lower panel fiber material 6 are of the same material system, which can ensure their compatibility and bonding strength, thereby further improving the molding quality and structural strength of the connection structure between the composite material and the metal skeleton 8.

[0054] Specifically, Figure 1 and Figure 2 As shown, the flexible fabric 3 includes a first fabric 31 and a second fabric 32 , wherein the first fabric 31 is laid on the upper panel fiber material 2 , and the second fabric 32 is laid on the lower panel fiber material 6 .

[0055] More specifically, in step S6, a flexible fabric 3 is laid at the corresponding position of the preform in the connection area of ​​the lower panel fiber material 6 and the upper panel fiber material 2, which can reduce the production cost while ensuring that it can effectively adjust the gap and improve the molding quality and structural strength of the connection structure between the composite material and the metal frame 8.

[0056] Specifically, the composite material has a thickness of 1 to 10 mm.

[0057] Specifically, the flexible fabric 3, the upper panel fiber material 2, and the lower panel fiber material 6 are at least one of glass fiber, carbon fiber and aramid fiber material systems.

[0058] Specifically, the metal skeleton 8 is made of at least one of steel, aluminum alloy, magnesium alloy, copper alloy and titanium alloy.

[0059] Specifically, the mold 1 is made of at least one of metal, wood and composite materials.

[0060] Specifically, the matrix resin of the composite material or laminate preform 5 is at least one of unsaturated polyester resin, vinyl resin, phenolic resin, epoxy resin and bismaleimide resin.

[0061] Specifically, the molding process of the composite material and the laminate preform 5 is one of a liquid molding process, a prepreg molding process, and a hand lay-up molding process.

[0062] Specifically, the material of the transition region core material 4 and the first core material 9 is at least one of polyurethane foam, polymethacrylimide foam, polyetherimide foam, polystyrene foam, polyvinyl chloride foam, polyethylene foam and acrylonitrile-styrene foam.

[0063] Specifically, an adhesive is used to bond the transition region core material 4 on both sides of the laminate preform 5, and the adhesive is at least one of epoxy, polyurethane, acrylic and vinyl adhesives.

[0064] More specifically, the upper panel fiber material 2 and the lower panel fiber material 6 are at least one of fiber fabric and fiber chopped strand mat.

[0065] Example 1

[0066] This embodiment proposes a method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness.

[0067] The metal frame 8 is made of steel, and the grade of the steel is Q355D. Figure 2 and Figure 3 As shown, the frame section of the metal skeleton 8 is an I-steel structure, the composite shell plate is a glass fiber foam sandwich composite material, and the thickness of the first core material 9 is 50 mm;

[0068] The connection method includes the following steps:

[0069] Specifically, the method for connecting the composite material and the metal skeleton based on the unequal thickness mold cavity comprises the following steps:

[0070] S1, according to the composite shell line shape, the corresponding mold 1 is manufactured, and the mold 1 line shape is offset outward according to the skeleton line shape to process the composite shell thickness;

[0071] S2, making a connection area laminate preform 5;

[0072] S3, bonding the transition region core material 4 to the laminate preform 5 to make a connection region preform, and reducing the thickness of the connection region preform by 1 mm;

[0073] S4, filling the polyurethane core mold 7 in the metal skeleton 8 frame;

[0074] S5, laying the lower panel fiber material 6 on the metal skeleton 8 and the polyurethane core mold 7, and laying the upper panel fiber material 2 on the mold 1;

[0075] S6, laying flexible fabric 3 on both the lower panel fiber material 6 and the upper panel fiber material 2, the mold 1, the upper panel fiber material 2 and the flexible fabric 3 form a first structure, and laying the lower panel fiber material 6 and the flexible fabric 3 on the metal skeleton 8 and the polyurethane core mold 7 to form a pre-structure;

[0076] S7, after installing the connection area preform and the first core material 9 on the preform, a second structure is formed;

[0077] S8, buckling the second structure onto the first structure for vacuum-assisted integrated molding, and demoulding after curing at room temperature for 48 hours.

[0078] Among them, the warp and weft weaving density of the flexible fabric is reduced by 65% ​​compared with the upper panel fiber material 2 and the lower panel fiber material 6, and the weaving weight of the flexible fabric is increased by 35% compared with the upper panel fiber material 2 and the lower panel fiber material 6.

[0079] Specifically, the laying thickness of the flexible fabric 3 is 1 mm.

[0080] Specifically, the flexible fabric 3, the upper panel fiber material 2, and the lower panel fiber material 6 are of the same material system; the flexible fabric 3, the upper panel fiber material 2, and the lower panel fiber material 6 are all glass fiber fabrics.

[0081] Specifically, the flexible fabric 3 includes a first fabric 31 and a second fabric 32 , wherein the first fabric 31 is laid on the upper panel fiber material 2 , and the second fabric 32 is laid on the lower panel fiber material 6 .

[0082] Step S2 is specifically as follows: when making the laminate preform 5, 55 layers of high-strength glass fiber fabric are laid, vacuum sealing is performed after the laying is completed, and vacuum infusion is performed using a matrix resin, and demoulding is performed after curing at room temperature for 24 hours to obtain a laminate preform 5 with a thickness of 11 mm;

[0083] Specifically, step S3 includes the following steps:

[0084] S31, using adhesive to bond the trapezoidal transition region core material 4 with a length of 120 mm on both sides of the laminate preform 5 to produce a connection region preform;

[0085] S32, reducing the thickness of the preform in the connection area by 1 mm.

[0086] Specifically, the adhesive is a vinyl adhesive.

[0087] Step S5 is specifically as follows: laying the lower panel fiber material 6 on the metal skeleton 8 and the polyurethane core mold 7, and laying the upper panel fiber material 2 on the mold 1, wherein the upper panel fiber material 2 and the lower panel fiber material 6 are high-strength glass fiber fabrics with 25 layers, and the thickness of the upper panel fiber material 2 and the lower panel fiber material 6 is 5 mm.

[0088] Step S6 specifically includes: laying flexible fabric 3 on both the lower panel fiber material 6 and the upper panel fiber material 2, wherein the flexible fabric 3 is a high-strength glass fiber fabric having three layers, and the thickness of the flexible fabric 3 is 1 mm.

[0089] More specifically, in step S6, a flexible fabric 3 is laid at the corresponding position of the preform in the connection area of ​​the lower panel fiber material 6 and the upper panel fiber material 2, which can reduce the production cost while ensuring that it can effectively adjust the gap and improve the molding quality and structural strength of the connection structure between the composite material and the metal frame 8.

[0090] Specifically, the transition region core material 4 and the first core material 9 are made of polyurethane foam.

[0091] Specifically, the mold 1 is made of wood.

[0092] Specifically, the matrix resin of the composite material or laminate preform 5 is vinyl resin.

[0093] Specifically, the molding process of the composite material and laminate preform 5 is a liquid molding process.

[0094] More specifically, in this embodiment, the molding process of the composite material and laminate preform 5 is vacuum-assisted molding of a liquid molding process.

[0095] Example 2

[0096] In this embodiment, different from the embodiment 1,

[0097] In step S2, the thickness of the preform in the connection area is reduced by 5 mm.

[0098] In step S6, the laying thickness of the flexible fabric 3 is 5 mm.

[0099] The warp and weft weaving density of the flexible fabric 3 is reduced by 50% compared with the upper panel fiber material 2 and the lower panel fiber material 6, and the weaving weight of the flexible fabric 3 is increased by 50% compared with the upper panel fiber material 2 and the lower panel fiber material 6.

[0100] Example 3

[0101] In this embodiment, different from the embodiment 1,

[0102] In step S2, the thickness of the preform in the connection area is reduced by 3 mm.

[0103] In step S6, the laying thickness of the flexible fabric 3 is 3 mm.

[0104] The warp and weft weaving density of the flexible fabric 3 is reduced by 80% compared with the upper panel fiber material 2 and the lower panel fiber material 6, and the weaving weight of the flexible fabric 3 is increased by 20% compared with the upper panel fiber material 2 and the lower panel fiber material 6.

[0105] Comparative Example 1

[0106] In this comparative example, unlike Example 1, no flexible fabric 3 is laid on the lower panel fiber material 6 and the upper panel fiber material 2.

[0107] Performance Testing

[0108] The composite material and metal structure connection structure prepared by the connection method of the composite material and the metal skeleton based on the unequal thickness mold cavity of Examples 1 to 3 and Comparative Example 1 was tested under the same conditions, and the pull-off loads between the composite material and the metal skeleton of Examples 1 to 3 and Comparative Example 1 are shown in Table 1.

[0109] Table 1 Pull-off load between the composite material and the metal skeleton of Examples 1 to 3 and Comparative Example 1

[0110]

[0111] It can be seen from Table 1 that the pull-off load of the composite material and metal structure connection structure prepared by the connection method of the composite material and the metal skeleton based on the unequal thickness mold cavity according to Examples 1 to 3 of the present invention is significantly improved compared with that of Comparative Example 1, which is improved by about 35%.

[0112] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for connecting a composite material and a metal frame based on a mold cavity of unequal thickness, characterized in that: The method for connecting a composite material and a metal skeleton based on a cavity of unequal thickness comprises the following steps: S1. Making a corresponding mold (1) according to the composite shell plate line shape; S2, making a laminate preform (5) in the connection area; S3, bonding the transition region core material (4) to the laminate preform (5) to produce a connection region preform, and reducing the thickness of the connection region preform; S4, filling the polyurethane core mold (7) in the metal skeleton (8) frame; S5, laying the lower panel fiber material (6) on the metal frame (8) and the polyurethane core mold (7), and laying the upper panel fiber material (2) on the mold (1); S6, laying a flexible fabric (3) on the lower panel fiber material (6) and the upper panel fiber material (2), the mold (1), the upper panel fiber material (2) and the flexible fabric (3) form a first structure, and the metal skeleton (8), the polyurethane core mold (7), the lower panel fiber material (6) and the flexible fabric (3) form a pre-structure; S7, installing the connection area preform and the first core material (9) on the preform to form a second structure; S8, buckling the second structure onto the first structure for integrated molding; The warp and weft weaving density of the flexible fabric (3) is reduced by 50% to 80% compared with the upper panel fiber material (2) and the lower panel fiber material (6), and the gram weight of the flexible fabric (3) is increased by 20% to 50% compared with the upper panel fiber material (2) and the lower panel fiber material (6).

2. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The laying thickness of the flexible fabric (3) is 1 to 5 mm.

3. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The flexible fabric (3), the upper panel fiber material (2), and the lower panel fiber material (6) are of the same material system.

4. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The flexible fabric (3) comprises a first fabric (31) and a second fabric (32), wherein the first fabric (31) is laid on the upper panel fiber material (2), and the second fabric (32) is laid on the lower panel fiber material (6).

5. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The material of the transition region core material (4) and the first core material (9) is at least one of polyurethane foam, polymethacrylimide foam, polyetherimide foam, polystyrene foam, polyvinyl chloride foam, polyethylene foam and acrylonitrile-styrene foam.

6. The method for connecting a composite material and a metal frame based on unequal thickness mold cavities according to claim 1, characterized in that: The flexible fabric (3), the upper panel fiber material (2), and the lower panel fiber material (6) are at least one of glass fiber, carbon fiber and aramid fiber material systems.

7. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The material of the metal skeleton (8) is at least one of steel, aluminum alloy, magnesium alloy, copper alloy and titanium alloy.

8. The method for connecting a composite material and a metal frame based on a cavity of unequal thickness according to claim 1, characterized in that: The mold (1) is made of at least one of metal, wood and composite materials.

9. The method for connecting a composite material and a metal frame based on unequal thickness mold cavities according to claim 1, characterized in that: The matrix resin of the composite material and the laminate preform (5) is at least one of unsaturated polyester resin, vinyl resin, phenolic resin, epoxy resin and bismaleimide resin.

10. The method for connecting a composite material and a metal frame based on unequal thickness mold cavities according to claim 1, characterized in that: The molding process of the composite material and laminate preform (5) is one of a liquid molding process, a prepreg molding process and a hand lay-up molding process.

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