A metal-to-composite fiber material connection structure and a processing method

Abstract

The application provides a metal and fiber composite material connecting structure, which comprises a metal material and a fiber composite material, the metal material has a connecting surface matched with the fiber composite material; a plurality of synaptic structure components, the synaptic structure component comprises a head and a root, the synaptic structure component is fixed to the connecting surface of the metal material through the root, and the synaptic structure component is inserted into the inside of the fiber composite material through the head. The synaptic structure component is used for adding a new connecting mode for a complex metal material part with difficult-to-process bolt holes on the surface, the synaptic structure component is inserted into the fiber composite material without cutting the fibers, the continuity of the fiber composite material is ensured, the mechanical properties of the composite fiber material are protected, the contact area of the metal material and the fiber composite material is larger through the synaptic structure component when the metal material and the fiber composite material are subjected to stretching, and the shear resistance of the overall connecting structure is stronger.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of heterogeneous material connection, in particular to a metal and composite fiber material connection structure and processing method. BACKGROUND

[0002] Additive manufacturing, also known as 3D printing, is a technology that adds materials layer by layer according to a designed 3D model to manufacture three-dimensional products. It has a significant role in industrial production and daily life due to its high manufacturing flexibility. Its outstanding advantages are that it can build shapes that cannot be achieved or imagined by other manufacturing processes, design components purely from a functional perspective without considering manufacturing-related limitations, allow very low production batches including single-piece production to achieve economically reasonable printing production purposes, and among all near-net shaping processes, additive manufacturing is the process with the highest net shaping level, with a very small amount of material that must be cut off for subsequent machining. The complex shapes constructed can be formed integrally, replacing products that currently require assembly from numerous components.

[0003] Generally, the connection technology of metal and FRP is divided into single connection such as glue joint, mechanical connection, welding, and mixed connection such as glue screw mixed connection. Glue joint refers to a connection technology that uses adhesive to bond two surfaces together in metal and composite materials. The presence of adhesive prevents the two surfaces from directly contacting each other, reducing the occurrence of electrochemical corrosion, and the uniform stress distribution of glue joint can avoid stress concentration and effectively reduce the weight of the connection structure without damaging the internal structure of the composite material. However, it has strict requirements for the connection surface, and the glue layer is easily affected by the environment and prone to aging, delamination, and other problems. Mechanical connection refers to a technology that uses bolts, rivets, etc. to connect the metal and FRP locally by opening holes. It is widely used in large heterogeneous material connections. However, since the mechanical parts penetrate the FRP, cutting off part of the fiber, it leads to local stress concentration at the hole, poor fatigue resistance, and other problems. Welding technology uses the local melting of the thermoplastic matrix to achieve connection, which is not suitable for thermosetting matrix composite materials. Mixed connection technology is a combination of multiple connection technologies, such as glue screw mixed connection structure. The bolt connection can reduce the peeling stress of the glue layer and prevent crack propagation. Compared with pure glue joint structure, the bolt can prevent sudden failure of the glue layer. However, due to different failure modes and bearing mechanisms of different connection methods, it is difficult to control the load ratio during use, and the bearing capacity improvement effect is not good. SUMMARY

[0004] Therefore, the present specification provides a metal and composite fiber material connection structure and processing method to protect the mechanical properties of the composite fiber material and improve the overall bearing and shear resistance of the connection structure.

[0005] The embodiment of the present specification provides the following technical solutions:

[0006] A connecting structure of metal and composite fiber material, comprising:

[0007] A metal material and a fiber composite material, the metal material has a connecting surface matched with the fiber composite material;

[0008] A plurality of synaptic structure assemblies, the synaptic structure assembly comprises a head, a neck and a root, the synaptic structure assembly is fixed to the connecting surface of the metal material through the root, and the synaptic structure assembly is inserted into the inside of the fiber composite material through the head.

[0009] Further, the synaptic structure assembly further comprises a neck and a waist, the diameter of the neck is smaller than that of the head, one end of the neck is connected with the head, the other end of the neck is connected with the root through the waist, the central axis of the waist has an included angle less than 90° with the direction of the connecting surface towards the metal material, and the radial sections of the head, the neck, the waist and the root are all curved surfaces.

[0010] Further, the waist expands towards the direction of the connecting surface, and the height of the waist is C1, wherein C1 is greater than or equal to the thickness of the fiber composite material.

[0011] Further, the head is a circular table, the diameter of the circular table is A1, A1 is smaller than the weaving aperture of the fiber composite material, and 0.3mm≤A1≤1mm, the outside arc radius of the circular table is A2, and 0.1mm≤A2≤0.2mm.

[0012] Further, the neck is contracted and then expanded towards the direction of the connecting surface, the diameter of the neck is smaller than that of the head and the waist, the fillet radius of the outside arc surface of the neck is B1, and 0.5mm≤B1≤1mm.

[0013] Further, the root expands towards the direction of the connecting surface, the diameter of the root is D2, 0.5mm≤D2≤2mm, the radius of the outside arc surface of the root is D1, and 0.3mm≤D1≤0.5mm.

[0014] Further, the metal material and the synaptic structure assembly are integrally formed by an additive manufacturing method, and the additive manufacturing method comprises a laser selective melting method.

[0015] Further, the metal material is one or a combination of stainless steel, high-temperature alloy and titanium alloy, and the fiber composite material is one or a combination of resin-based carbon fiber composite materials.

[0016] Further, the vertical section of the connecting surface is Z-shaped.

[0017] A processing method of a connecting structure of metal and composite fiber material, used for manufacturing the connecting structure of metal and composite fiber material, and the processing method comprises the following steps:

[0018] According to the connection strength requirement and the fiber gap of the fiber composite material, the size and arrangement of the synapse structure assembly are designed;

[0019] The metal material and the synapse structure assembly are integrally manufactured by using an additive manufacturing method;

[0020] The connecting surface of the metal material is subjected to mixed acid anodization treatment;

[0021] The fiber composite material is laid on the connecting surface of the metal material, and the synapse structure assembly is inserted through the fiber gap of the fiber composite material;

[0022] The fiber composite material and the metal material are combined into a mold, and after the whole is solidified and formed into the mold, the mold is removed and modified.

[0023] Compared with the prior art, the above at least one technical scheme adopted by the embodiment of the present application can achieve at least the following beneficial effects:

[0024] The synapse structure assembly can add a new connection mode to the complex metal material with difficult-to-machine bolt holes, reduce the appearance of bolts and other assembly parts, and when the synapse structure assembly is inserted into the fiber composite material, the fibers are not cut, the continuity of the composite fiber material is ensured, the mechanical properties of the fiber composite material are protected, and when subjected to tension, the contact area of the metal material and the fiber composite material is larger through the synapse structure assembly, so that the shear resistance of the whole connection structure is stronger. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 is a whole structure schematic diagram of the metal and the composite fiber material connection structure of the embodiment of the present application;

[0027] Figure 2 is a synapse structure assembly structure schematic diagram of the connection structure of the embodiment of the present application;

[0028] Figure 3 is a metal material and synapse structure assembly structure schematic diagram of the connection structure of the embodiment of the present application;

[0029] Figure 4 is a structure schematic diagram of the metal and the composite fiber material connection structure after demolding of the embodiment of the present application.

[0030] Reference numerals: 1, metal material; 2, synaptic structure assembly; 3, fiber composite material; 4, mold; 5, connecting surface. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below with reference to the drawings.

[0032] The above and other aspects of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[0033] It is to be understood that the foregoing description is that of certain examples of the application and that numerous changes in the details of construction and the combination and arrangement of parts can be made by those skilled in the art without departing from the scope of the application.

[0034] It is also to be understood that the following description is only illustrative of the aspects of the present application and that no limitation of the scope of the application is intended by the description.

[0035] Furthermore, in the following description, numerous specific details are set forth in order to provide a thorough understanding of the examples. However, it will be apparent to one skilled in the art that the aspects can be practiced without these specific details.

[0036] Nowadays, the study on the penetration enhanced connection finds that optimizing the shape and height of the connection synapse can greatly enhance the connection strength, the tensile strength of the ball pin is increased by 40% than the cylindrical pin, the connection strength of the pyramid is increased by 20% than the cylindrical, the failure strength of the linear pin is increased by two times than the cylindrical, and the failure mode is also changed.

[0037] The technical solutions provided by the embodiments of the present application are described below with reference to the drawings.

[0038] Reference Figure 1 And Figure 2 The connection structure of the metal and the composite fiber material in the embodiment of the present application comprises: a metal material 1, a fiber composite material 3, and a plurality of synapse structure assemblies 2, the metal material 1 has a connecting surface 5 matched with the fiber composite material 3, the synapse structure assembly 2 is fixed to the connecting surface 5 of the metal material 1, and the synapse structure assembly 2 is inserted into the inside of the fiber composite material 3. When the connection structure is processed, an external mold 4 is used for curing and forming.

[0039] The synapse structure assembly 2 comprises a head, a root, a neck, and a waist, the synapse structure assembly 2 is fixed to the connecting surface of the metal material 1 through the root, and the synapse structure assembly 2 is inserted into the inside of the fiber composite material through the head. The diameter of the neck is smaller than the diameter of the head, one end of the neck is connected with the head, and the other end of the neck is connected with the root through the waist.

[0040] The radial sections of the head, the neck, the waist, and the root are all curved surfaces, and the overall design is smooth, so that the fiber composite material 3 is prevented from being cut during the connection process, and the connection strength is effectively improved.

[0041] The head is a circular table, the diameter of the circular table is A1, A1 is smaller than the weaving aperture of the fiber composite material 3, A1 is 0.3mm to 1mm (0.3mm≤A1≤1mm), and the outer arc surface radius of the circular table is A2, A2 is 0.1mm to 0.2mm (0.1mm≤A2≤0.2mm). The circular table of the head ensures that the fiber composite material 3 is less likely to be pulled off under the stretching action after the synapse is bent during the connection process.

[0042] The waist gradually thickens in the direction towards the connecting surface 5, the height of the waist is C1, and C1 is greater than or equal to the thickness of the fiber composite material 3. The central axis of the waist and the direction of the connecting surface 5 towards the metal material 1 have an included angle less than 90°, that is, the waist is distributed in an inclined manner close to the fiber composite material 3, and the inclined direction is perpendicular to the left of the connecting surface 5 of the metal piece 1. The inclined design improves the stress uniformity, effectively improves the stiffness of the synapse structure assembly 2, and prevents the deformation of the synapse structure.

[0043] The neck portion expands towards the connecting surface 5, the diameter of the neck portion is smaller than the diameter of the head portion and the waist portion, the fillet radius of the outer arc surface of the neck portion is B1, and B1 is 0.5 mm to 1 mm (0.5 mm≤B1≤1 mm). The smooth transition of the neck portion avoids stress concentration when the synapse structure assembly 2 is connected with the fiber composite material 3, and does not cause the fiber delamination and fracture failure of the upper portion.

[0044] The root portion expands towards the connecting surface 5, the diameter of the root portion is D2, D2 is 0.5 mm to 2 mm (0.5 mm≤D2≤2 mm), and the radius of the outer arc surface of the root portion is D1, D1 is 0.3 mm to 0.5 mm (0.3 mm≤D1≤0.5 mm). The shape design of the root portion effectively improves the root fracture strength and the shear resistance.

[0045] As shown in Figure 3 The metal material 1 and the synapse structure assembly 2 are integrally formed by an additive manufacturing method, and the additive manufacturing method includes a laser selective melting method. By integrally forming the metal part through additive manufacturing, the synapse structure assembly on the surface of the connecting portion can provide a new synapse connection mode for complex parts with difficult-to-machine bolt holes, reduce the presence of bolts and other assembly parts, and connect without cutting the carbon fiber through the synapse structure assembly 2, ensuring the continuity of the carbon fiber and protecting the mechanical properties of the carbon fiber. When subjected to tension, the contact area between the metal and the composite material is larger, and the shear resistance of the synapse structure assembly 2 is stronger.

[0046] The metal material 1 can be one or a combination of stainless steel, high-temperature alloy, and titanium alloy, and the fiber composite material 3 can be one or a combination of resin-based carbon fiber composite materials.

[0047] In some embodiments, taking the preparation of a connecting piece of a carbon fiber composite material plate (fiber composite material 3) and an aluminum plate (metal material 1) as an example, the length, width, and height of the aluminum plate and the carbon fiber composite material piece are all 60 mm x 60 mm x 10 mm, and the area of the connecting region is 60 mm x 20 mm. The specific processing method is as follows:

[0048] Step one, according to the connection strength requirement and the fiber gap of the fiber composite material 3, the size and arrangement of the synapse structure assembly 2 are designed.

[0049] Specifically, the head diameter A1 of the synapse structure assembly 2 is 0.3mm to 1mm, and the radius A2 is 0.1mm to 0.2mm. The neck diameter of the synapse structure assembly 2 is smaller than the sizes of the head and the waist, and the shape is a circular arc, and the radius B1 of the outer arc surface is 0.5mm to 1mm. The waist of the synapse structure assembly 2 is inclined on one side, and the direction of the inclined waist is perpendicular to the connecting surface 5 of the metal material 1 and faces the metal material 1, and the height is not greater than the thickness of the connected fiber composite material 3. The waist of the synapse structure assembly 2 gradually thickens along the height direction, and the diameter of the synapse cross section at the root is circular or elliptical, but cannot have edges and right angles. The overall size of the head, neck, waist and root is related to the manufacturing aperture of the fiber composite material 3 and the use scene. According to experiments and simulations, if the fiber gap of the fiber composite material 3 is large and the external load is large, the size of the head, neck, waist and root can be increased, and if the fiber gap of the fiber composite material 3 is small and the external load is small, the size of the head, neck, waist and root is small. But it cannot be lower than the minimum size of the above interval, because the size effect makes the synapse structure assembly 2 fail to enhance the connection strength and greatly increase the difficulty of additive manufacturing.

[0050] The arrangement density of the synapse structure assembly 2 is related to the use scene of the connection. In the use scene with low connection strength requirement, low-density synapses are arranged, because the fiber gap of the fiber composite material 3 is usually less than 2mm, and the size can be determined by selecting the upper limit in the design. If the gap is too small, the lower limit can be used. The lower limit is related to the size effect, and too small size cannot meet the external load requirement, and the additive manufacturing process is very cumbersome. For example, when the shear strength is less than 20MPa, a 6*6 synapse arrangement can be used.

[0051] The top end is spherical, and the tensile performance is improved by 40% compared with the cylindrical structure. It is also found in actual simulation that the bending moment and shear force of the synapse structure assembly 2 gradually increase with the decrease of the height, so the root is designed to be inclined, and the connection strength is significantly enhanced compared with the cylindrical synapse. The height of the waist is consistent with the thickness of the connected part, and it is found in the test process that if the height of the waist is lower than the thickness of the connected part, the fiber composite material 3 is prone to delamination, fracture, slip and other damage forms during use, which significantly reduces the connection strength. It is found through experiments on the lower limit of the size range that the mechanical properties have been reduced to a certain extent, but the connection strength is significantly improved when the arrangement density is increased, but the additive manufacturing process becomes cumbersome and difficult, so the minimum value of the head, neck, waist and root is selected as the lower limit.

[0052] Step two, as shown in Figure 3 , the metal material 1 and the synapse structure assembly 2 are integrally manufactured by additive manufacturing.

[0053] Specifically, the vertical section of the connecting surface 5 is Z-shaped, effectively improving the flatness of the connecting surface.

[0054] Step three, the connecting surface 5 of the metal material 1 is subjected to mixed acid anodizing treatment.

[0055] Specifically, the time for the mixed acid anodizing treatment is 4 to 4.5 hours.

[0056] Step four, the fiber composite material 3 is laid on the connecting surface 5 of the metal material 1, and the synaptic structure assembly 2 is inserted through the fiber gap of the fiber composite material 3.

[0057] Specifically, the fiber composite material 3 can be carbon fiber composite material prepreg or dry carbon fiber reinforcement, the fiber composite material 3 is laid on the connecting surface 5 of the metal material 1, and the head of the synaptic structure assembly 2 first penetrates the fiber gap of the carbon fiber composite material prepreg or dry carbon fiber reinforcement, and the entire synaptic structure assembly is inserted into the fiber composite material 3.

[0058] Step five, the fiber composite material 3 and the metal material 1 are clamped together. The upper and lower molds are fastened with bolts, and a gap of about 0.2 mm is reserved for clamping under the premise of ensuring the sealing of the mold. The air tightness of the mold is checked, and the vacuum degree does not decrease by more than 0.005 MPa in 10 min;

[0059] Specifically, the mold 4 of the carbon fiber composite material prepreg after clamping is heated at a rate not greater than 3℃ / min to 80℃ and kept for 3h, and then cooled at a rate not greater than 2℃ / min to below 60℃, and kept for 2h at 55℃-60℃, i.e. the curing and forming method is mold pressing. Or the resin injection port of the fiber composite material 3 of the dry carbon fiber reinforcement is connected with the resin injection nozzle of a small resin injection equipment, the resin outlet of the mold is connected with the resin inlet of a resin collector, the injection pressure is adjusted, the resin is injected within a reasonable range (before the formal test piece is made, three simulation test pieces are used to determine the injection pressure of the final product), when the resin flowing out of the resin outlet is basically free of bubbles, the resin injection port and the resin outlet are closed in turn, the mold is heated at a rate not greater than 2℃ / min to 80℃, kept for 5h, and then cooled at a rate not greater than 2℃ / min to below 60℃ for curing and forming, i.e. the curing and forming method is mold pressing.

[0060] Step six, after the overall curing and forming of the mold 4, the mold 4 is demolded and modified.

[0061] Specifically, the connecting structure of the metal and the composite fiber material after demolding is as shown in Figure 4 .

[0062] According to the actual test and simulation data, the connection of the synaptic structure assembly 2 of the embodiment has improved tensile and impact resistance compared to ordinary glue connection, and can be used in the connection of metal and composite materials that bear stronger tensile force and greater impact.

[0063] The embodiment of the application achieves the following technical effects: The embodiment of the application takes an additive manufacturing method as a main design means, and when a complex metal part is manufactured, a metal surface is treated by an auxiliary chemical method to prevent electrochemical corrosion of the metal and the carbon fiber composite material and reduce the connection strength. Since the connection structure is integrally formed by molding / molding, the metal synaptic structure passes through the gap of the carbon fiber prepreg or dry carbon fiber reinforcement, does not shear the carbon fiber composite material, ensures the continuity of the carbon fiber composite material, has a larger contact area of the metal and the composite material when subjected to tension, and has stronger shear resistance. Compared with other connection methods, the embodiment can avoid stress concentration of mechanical connection and composite material fracture failure caused by cutting of carbon fibers, has large dispersion and low reliability of cementation, in a detection and repair process, if an internal microstructure is not damaged, a metal joint part can be reused, and maintenance is facilitated.

[0064] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts of each of the embodiments can be referred to each other, and each of the embodiments focuses on the difference from other embodiments. In particular, for the method embodiment described later, since it is corresponding to the system, the description is relatively simple, and the related parts can be referred to the part of the system embodiment.

[0065] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A connection structure between a metal and a composite fiber material, characterized in that, include: Metal material (1) and fiber composite material (3), wherein the metal material (1) has a connecting surface (5) that cooperates with the fiber composite material (3); Multiple synaptic structure components (2), each synaptic structure component (2) includes a head and a root, the synaptic structure component (2) is fixed to the connecting surface (5) of the metal material (1) through the root, and the synaptic structure component (2) is inserted into the interior of the fiber composite material (3) through the head; The synaptic structure assembly (2) also includes a neck and a waist. The diameter of the neck is smaller than the diameter of the head. One end of the neck is connected to the head, and the other end of the neck is connected to the root through the waist. The central axis of the waist has an angle of less than 90° with the direction of the connecting surface (5) toward the metal material (1). The radial sections of the head, the neck, the waist, and the root are all curved surfaces. The waist expands toward the connecting surface (5), and the height of the waist is C1, wherein C1 is greater than or equal to the thickness of the fiber composite material (3); The head is a circular platform with a diameter of A1, A1 being smaller than the weave pore size of the fiber composite material (3), and 0.3 mm ≤ A1 ≤ 1 mm. The outer arc radius of the circular platform is A2, and 0.1 mm ≤ A2 ≤ 0.2 mm. The neck contracts and then expands in the direction of the connecting surface (5). The diameter of the neck is smaller than the diameter of the head and the waist. The radius of the rounded corner of the outer arc surface of the neck is B1, and 0.5 mm ≤ B1 ≤ 1 mm. The root expands toward the connecting surface (5), the diameter of the root is D2, and 0.5 mm≤D2≤2 mm, the radius of the outer arc surface of the root is D1, and 0.3 mm≤D1≤0.5 mm.

2. The connection structure of metal and composite fiber material according to claim 1, characterized in that, Metal material (1) and synaptic structure component (2) are integrally formed by additive manufacturing method, which includes selective laser melting.

3. The connection structure of metal and composite fiber material according to claim 1, characterized in that, Metallic material (1) is one or more combinations of stainless steel, high-temperature alloy, and titanium alloy, and fiber composite material (3) is resin-based carbon fiber composite material.

4. The connection structure of metal and composite fiber material according to claim 1, characterized in that, The vertical cut of the connecting surface (5) is Z-shaped.

5. A method for processing a metal-composite fiber material connection structure, used to manufacture the metal-composite fiber material connection structure according to any one of claims 1 to 4, characterized in that, The processing method includes the following steps: Based on the connection strength requirements and the fiber gaps in the fiber composite material (3), the size and arrangement of the synaptic structure component (2) are designed; The metal material (1) and the synaptic structure component (2) are fabricated in one piece using additive manufacturing methods. The connecting surface (5) of the metal material (1) is subjected to mixed acid anodizing treatment; The fiber composite material (3) is laid on the connecting surface (5) of the metal material (1), and the synaptic structure component (2) is passed through the fiber gap of the fiber composite material (3); The fiber composite material (3) and the metal material (1) are placed into the mold (4) for mold closing. After the whole is cured and formed, the mold is removed and the finishing process is carried out.

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