A pre-embedded metal joint composite wing surface structure and laying method

Abstract

The present application relates to the field of composite materials, and relates to a pre-embedded metal joint composite wing surface structure and a laying method. The pre-embedded metal joint composite wing surface structure comprises a composite skin, foam, a main beam, a main joint and carbon filaments. The metal joint is completely covered inside the composite skin except for a mechanical interface, which greatly increases the bonding area between the metal joint and the composite skin and improves the integrity of the wing surface structure. The metal joint does not have redundant structures required for maintaining the aerodynamic shape, which reduces the design and manufacturing difficulty of the joint, effectively reduces the manufacturing cost and the structure weight. Moreover, the recess at the joint between the metal joint and the composite main beam is filled with carbon filaments, which effectively improves the connection strength between the metal joint and the composite main beam and reduces the risk of peeling failure between the metal joint and the composite main beam under impact load.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of composite materials, and relates to a composite wing structure with pre-embedded metal joints and a laying method. BACKGROUND

[0002] Composite materials have high specific strength, high specific modulus, strong performance designability and other advantages, and are widely used in the field of aerospace. Among them, the composite wing structure mainly includes joints, composite main beams, composite skins, PMI foams and other structures. During the use of the wing structure, multiple mechanical movements such as folding and unfolding and lock pin locking need to be met. Local stress concentration may occur at the connection between the wing root skin and the joint. All dynamic loads and static loads of the wing surface need to be transmitted to the joint through this place. Therefore, the joint is usually made of high-strength aluminum alloy or titanium alloy and other metal materials by machining. There are various connection modes between the metal joint and the composite main beam and the composite skin. The simple adhesive connection mode is prone to peeling failure between the metal joint and the composite main beam and the composite skin under impact load. The simple mechanical connection mode is prone to stress concentration near the screw. Therefore, the composite wing structure usually adopts a mixed connection mode of adhesive connection and mechanical connection. This connection mode needs to be performed after the adhesive assembly of the wing structure is completed, and the joint between the metal joint and the composite main beam and the composite skin is connected by pulling out the screw or reinforcing the screw. This connection mode involves many process flows, has low production and assembly efficiency, and does not fully play the advantage of weight reduction of composite materials as the number of screws increases.

[0003] In addition, the metal joint needs to meet the consistency of the connection between the wing structure in the folded and unfolded states and the aerodynamic shape of the fuselage. Therefore, the structure of the metal joint is often relatively complex and redundant in material, and needs to be processed at multiple complex curved surfaces and lightening grooves, which is contrary to the design concept of weight reduction and cost reduction. Therefore, under the constraint of the aerodynamic shape, in order to meet the overall strength and rigidity of the composite wing structure, it is necessary to develop a composite wing structure with pre-embedded metal joints as a design goal of low cost and light weight. SUMMARY

[0004] OBJECTIVE

[0005] In order to solve the above-mentioned technical problems, the present application provides a composite wing structure with pre-embedded metal joints. The wing structure is mainly formed by pure adhesive co-curing of the metal joint and the composite main beam and the composite skin. The wing cross-sectional structure is shown in Figure 1 .

[0006] TECHNICAL SCHEME

[0007] A pre-embedded metal joint composite wing surface structure, comprising a composite skin, foam, main beam, main joint, carbon wire; the main joint is an integrally formed machined part, the main joint comprises a skin covering area and a main beam covering area, a mechanical interface is provided on the skin covering area; a plurality of grooves are provided on the main beam covering area, the carbon wire is wound in the grooves to form a carbon wire filling area;

[0008] The skin covering area of the main joint is entirely covered inside the composite skin except the mechanical interface area, the main beam covering area of the main joint is inserted into the main beam, and the gap between the main beam and the composite skin is filled with foam.

[0009] Further, the foam is specifically poly (methyl methacrylimide) (PMI) foam.

[0010] Further, the main joint is made of metal material.

[0011] Further, the metal material is specifically aluminum alloy.

[0012] Further, a lightening groove is provided on the sidewall of the skin covering area.

[0013] Further, a lightening hole is provided on the end face of the carbon wire filling area.

[0014] Further, a boss is provided on the mechanical interface, when the wing surface rotates, the locking pin contacts the boss and slides on the boss, avoiding the contact between the metal locking pin and the composite material, causing scratches on the surface of the composite material.

[0015] A laying method of a pre-embedded metal joint composite wing surface structure,

[0016] First, the main beam is laid with the internal foam and the metal joint sleeve part as the main beam laying mold to complete the positioning relationship between the main joint and the main beam; then, the main joint is constrained by the positioning pin of the wing surface forming mold to determine the position of the main joint and the composite main beam assembly in the wing surface forming mold; the gap between the wing surface forming mold and the main joint and the main beam is filled with multiple sections of foam to complete the assembly of the composite skin male mold (main joint, main beam, and external foam of the main beam); the pre-impregnated material is laid according to the designed layering table on the surface of the male mold, and multiple vacuum pre-compaction is required during the layering process to ensure that the pre-impregnated material layering assembly completely matches the male mold assembly as much as possible; the female mold is combined.

[0017] The wing surface structure is formed, cured, and demolded according to the process flow, and deburring and post-processing are completed; finally, non-destructive testing is performed on the main joint and the skin bonding surface, the main joint and the main beam bonding surface, and the main beam and the skin bonding surface area.

[0018] Further, the mold closing is specifically: heating to 80℃±5℃ at a heating rate of ≤3℃ / min, holding for 30min±5min, then pressurizing to mold closing, then heating to 125℃±5℃ at a heating rate of ≤3℃ / min, holding for 90min-120min under pressure. Finally, under pressure, cooling to below 60℃ at a cooling rate of ≤2℃ / min or naturally.

[0019] Further, the metal and the composite material, the composite material and the foam, and the bonding surface between different materials and the splicing section of the foam need to be coated with a corresponding amount of adhesive film according to the actual situation to ensure the bonding interface strength. The application has the beneficial effects of:

[0020] The metal joint is completely covered inside the composite skin except for the mechanical interface, which greatly increases the bonding area between the metal joint and the composite skin and improves the integrity of the wing surface structure; the metal joint does not have redundant structures required to maintain the aerodynamic shape, which reduces the design and manufacturing difficulty of the joint and effectively reduces the manufacturing cost and structural weight; and the groove at the joint between the metal joint and the composite main beam is filled with carbon filaments, which effectively improves the connection strength between the metal joint and the composite main beam and reduces the risk of peeling failure between the metal joint and the composite main beam under impact load; the composite main beam and the composite skin are co-cured, which reduces the process flow compared to co-bonding and effectively improves the bonding strength between the main beam and the skin; the composite skin and the metal joint and the composite main beam are filled with PMI foam, which effectively improves the overall strength and stiffness of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Schematic diagram of the cross section of the wing surface structure joint section;

[0022] Figure 2 Schematic diagram of the metal joint structure;

[0023] Wherein: 1 composite skin, 2 PMI foam, 3 main beam, 4 metal main joint, 5 carbon filament filling, 6 mechanical interface, 7 skin covering area, 8 main beam covering area, 9 carbon filament filling area, 10 lightening groove, 11 lightening hole. DETAILED DESCRIPTION

[0024] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the embodiments of the present application. In the examples, the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below.

[0025] Embodiment

[0026] The embedded metal joint composite wing surface structure comprises a composite skin 1, a foam 2, a main beam 3, a main joint 4, and carbon filaments 5. The main joint 4 is an integrally formed machining part, and the main joint 4 comprises a skin covering area 7 and a main beam covering area 8. The mechanical interface 6 is arranged on the skin covering area 7. A plurality of grooves are arranged on the main beam covering area 8, and the carbon filaments 5 are wound in the grooves to form a carbon filament filling area.

[0027] The skin covering area 7 of the main joint 4 is covered in the composite skin 1 except for the mechanical interface area. The main beam covering area 8 of the main joint 4 is inserted into the main beam 3. The gap between the main beam 3 and the composite skin 1 is filled with the foam 2.

[0028] In an embodiment of the present application, the foam 2 is specifically a polymethacrylimide (PMI) foam.

[0029] In an embodiment of the present application, the main joint 4 is made of a metal material.

[0030] In an embodiment of the present application, the metal material is specifically an aluminum alloy.

[0031] In an embodiment of the present application, the main joint 4 is provided with

[0032] In an embodiment of the present application, the main joint 4 is provided with

[0033] In an embodiment of the present application, the main joint 4 is provided with

[0034] In an embodiment of the present application, the mechanical interface 6 is provided with a boss. When the wing surface rotates, the locking pin contacts the boss and slides on the boss, so as to avoid the contact between the metal locking pin and the composite material and cause the scratch on the surface of the composite material.

[0035] A method for laying a metal joint composite wing surface structure,

[0036] First, the main beam is laid with its internal foam and metal joint sleeve portion in the main beam laying mold, and the positioning relationship between the main joint and the main beam is completed; then, the main joint is constrained by the positioning pin of the wing forming mold to determine the position of the main joint and the composite main beam assembly in the wing forming mold; the gap between the wing forming mold and the main joint and the main beam is filled with multi-section foam to complete the assembly of the composite skin male mold (main joint, main beam, external foam of main beam); the designed layer table is laid on the surface of the male mold; multiple vacuum pre-compaction is required during the laying process to ensure that the pre-impregnated layer assembly completely adheres to the male mold assembly; the female mold is combined, heated to 80℃±5℃ at a heating rate of ≤3℃ / min, and kept for 30min±5min, then pressurized to the mold closing, and then heated to 125℃±5℃ at a heating rate of ≤3℃ / min, and kept for 90min-120min. Finally, under the pressure maintaining condition, the temperature is lowered to below 60℃ at a cooling rate of ≤2℃ / min or naturally cooled to below 60℃ and then depressurized.

[0037] According to the process flow, the wing surface structure is formed and cured, and after demolding and deburring post-processing, the main joint and the skin bonding surface, the main joint and the main beam bonding surface, and the main beam and the skin bonding surface area are subjected to non-destructive testing.

[0038] In some embodiments of the present application, the bonding surface between different materials such as metal and composite material, composite material and foam, and the foam splicing section needs to be coated with a corresponding amount of adhesive film according to the actual situation to ensure the strength of the bonding interface.

[0039] Referring to Figure 1The wing surface structure is from inside to outside. First, the composite main beam is pre-impregnated and laid up by the main beam laying-up mold with its internal PMI foam and metal joint sleeve part, to complete the positioning relationship between the metal joint and the composite main beam. Then, the metal joint is constrained by the positioning pin of the wing surface forming mold to determine the position of the metal joint and the composite main beam assembly in the wing surface forming mold. The gap between the wing surface forming mold and the metal joint and the composite main beam is filled with multi-section PMI foam to complete the assembly of the composite skin male mold (metal joint, composite main beam, and external PMI foam of the main beam). The pre-impregnated material is laid up on the surface of the male mold according to the designed lay-up table. Due to the complex shape of the wing surface, multiple vacuum pre-compaction is required during the lay-up process to ensure that the pre-impregnated material lay-up group completely matches the male mold assembly as much as possible. The female mold is combined, heated and pressurized, the wing surface structure is formed and cured according to the process flow, and post-processing such as demolding and deburring is completed. Finally, non-destructive testing is performed on the key areas such as the bonding surface of the main joint and the skin, the bonding surface of the main joint and the main beam, and the bonding surface of the main beam and the skin. In addition, it should be noted that in addition to the interface between the composite parts, the bonding surface between different materials such as metal and composite, composite and foam, and the foam jointing section needs to be coated with a corresponding amount of adhesive film according to the actual situation to ensure the bonding interface strength.

[0040] The metal joint is completely covered inside the composite skin except for the mechanical interface, without redundant structures to maintain the aerodynamic shape, and the composite wing surface structure does not use the pull pins or screws required by mechanical connection. The PMI foam is filled in the gap between the composite skin and the metal joint and the composite main beam, effectively reducing the weight of the wing surface structure and improving the integrity of the wing surface structure.

[0041] In addition, based on the strength analysis results, a local lightening groove is designed for the metal joint. Considering the limited bonding strength between the metal joint and the composite, which is prone to peeling failure under impact load, a process groove is designed for the sleeve section of the metal joint and the main beam, as shown in Figure 2 The process groove is filled with unidirectional carbon filaments, with one side limited in the process groove and the other side co-cured with the main beam, effectively improving the connection strength between the metal joint and the main beam.

[0042] As used herein, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It is also to be understood that terms such as those defined in commonly used dictionaries are to take on ordinary and customary meanings unless otherwise explicitly provided for herein and are to be interpreted as being indicative of the intent of the inventors to invoke a special definition beneficial over conclusions from a more customary, semantic meaning of term, unless otherwise explicitly provided for herein. The summary of the application described above, the detailed description of the application described below, and the drawings illustrate the state of the art, and are not limiting of the present application. It will be readily understood to those skilled in the art that the application is susceptible to broad disposal and use, and that the above described embodiments are only exemplary of the principles of the application and are not to be considered limitation on the scope of the application. Accordingly, the scope of the application is not intended to be limited to the above described embodiments but rather is capable of extending to other embodiments and uses thereof which come within the scope of the following claims and their equivalents.

Claims

1. A composite material wing structure with a pre-embedded metal joint, characterized in that, The system includes a composite material skin, foam, a main beam, a main connector, and carbon fiber. The main connector is a one-piece machined part, comprising a skin covering area and a main beam covering area. The skin covering area has a mechanical interface. The main beam covering area has several grooves, and carbon fiber is wound inside the grooves to form a carbon fiber filling area. Except for the mechanical interface area, the skin covering area of ​​the main connector is completely covered inside the composite material skin. The main beam covering area of ​​the main connector is inserted into the main beam, and the gap between the main beam and the composite material skin is filled with foam.

2. The wing structure as described in claim 1, characterized in that, The foam is specifically polymethacrylimide (PMI) foam.

3. The wing structure as described in claim 1, characterized in that, The main connector is made of metal.

4. The wing structure as described in claim 3, characterized in that, The metal material is specifically an aluminum alloy.

5. The wing structure as described in claim 1, characterized in that, It also includes a lightening groove, which is formed on the sidewall of the skin-covered area.

6. The wing structure as described in claim 1, characterized in that, It also includes relief holes, which are formed on the end face of the carbon filament filling area.

7. The wing structure as described in claim 1, characterized in that, The mechanical interface is provided with a boss. When the wing surface rotates, the locking pin contacts the boss and slides on the boss to prevent the metal locking pin from contacting the composite material and causing scratches on the surface of the composite material.

8. The method for laying the wing structure as described in claim 1, characterized in that, First, the main beam is prepreg laid using its internal foam and metal joint sleeve as the main beam lining mold, establishing the positioning relationship between the main joint and the main beam. Then, the main joint is constrained by the positioning pins of the wing-forming mold, determining the position of the main joint and the composite main beam assembly within the wing-forming mold. Multiple sections of foam are filled into the gaps between the wing-forming mold, the main joint, and the main beam to complete the assembly of the composite skin male mold assembly. Prepreg is then laid on the male mold surface according to the designed layup schedule. Multiple vacuum pre-compaction processes are required during layup to ensure the prepreg layup assembly adheres as completely as possible to the male mold assembly. Finally, the female mold is closed. The wing structure is formed and cured according to the process flow, and demolding and deburring are completed. Finally, non-destructive testing is carried out on the bonding surfaces of the main joint and the skin, the bonding surfaces of the main joint and the main beam, and the bonding surfaces of the main beam and the skin.

9. The method for laying the wing structure as described in claim 8, characterized in that, The mold assembly process is as follows: heat the mold to 80℃±5℃ at a heating rate of ≤3℃ / min, hold for 30min±5min, then pressurize the mold to close, then heat the mold to 125℃±5℃ at a heating rate of ≤3℃ / min, and hold for 90min~120min; finally, under pressure, release the pressure by cooling at a rate of ≤2℃ / min or by natural cooling to below 60℃.

10. The method for laying the wing structure as described in claim 9, characterized in that, For metals and composite materials, composite materials and foams, the bonding surfaces of different materials and the joints of foams need to be covered with the appropriate amount of adhesive film according to the actual situation to ensure the strength of the bonding interface.

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