Semi-hollow rivet with resin filler

Abstract

A semi-hollow rivet with resin filler comprises a rivet cover, a rivet body and filler arranged in the rivet body, a glue containing groove is formed in the bottom of the rivet cover and surrounds the rivet body, glue overflowing holes are formed in the side face of the rivet body, and the filler is arranged in the rivet body through threads arranged outside. The invention relates to a method for realizing composite connection of a composite material and a metal material by utilizing a rivet with an improved internal structure. According to the scenes of applied materials with different thicknesses, rivets with different inner cavity structures can be used, so that the effects of containing composite material cuttings and filling defects such as connecting interface cracks are achieved, the influence of the cuttings on the appearance quality is avoided, and the weakening of the connecting interface cracks on the overall strength and corrosion resistance is avoided.

Description

Technical Field

[0001] The invention relates to a technology in the field of mechanical processing, in particular to a semi-hollow rivet with resin filling. Background Art

[0002] Composite materials are widely used as lightweight reinforcement parts in the fields of aerospace, automobiles, ships, etc. However, traditional riveting technology is prone to damage to composite materials, deformation or brittle fracture of metal materials, etc. Fusion welding technology is only applicable to thermoplastic composite materials and is prone to defects such as pores and cracks, making it difficult to obtain high-performance connection joints. Existing rivets cannot avoid substrate damage and fiber delamination caused when penetrating thermoplastic fiber-reinforced metal laminates. At the same time, additional heating devices need to be added to heat the thermoplastic resin in the rivet cavity. The content of thermoplastic resin in the rivet cavity cannot be accurately controlled and adjusted in batch production to achieve filling and repair of the mechanical riveting interface. The heated and molten thermoplastic resin only flows out of the through hole by the extrusion of material debris, and it is difficult to evenly and fully fill the riveting interface. The obtained adhesive sealing is poor and the joint strength depends on the mechanical locking of the rivet and the material to be connected, and the peeling strength is low. Summary of the invention

[0003] In view of the problems of fiber filament extraction and many cracks near the rivet holes in the existing riveting and welding process when connecting composite materials, the present invention proposes a semi-hollow rivet with resin filler, and a method of realizing composite connection between composite materials and metal materials by using rivets with improved internal structures. According to the different thickness material scenarios applied, rivets with different inner cavity structures can be used to achieve the effect of accommodating composite material chips and filling defects such as cracks in the connection interface, avoiding the influence of chips on the appearance quality and the weakening of the overall strength and corrosion resistance by cracks in the connection interface.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to a semi-hollow rivet with filler, comprising a rivet cover, a rivet body and a filler arranged in the rivet body, wherein a glue containing groove is arranged around the rivet body at the bottom of the rivet cover, and a glue overflow hole is arranged on the side of the rivet body.

[0006] The filler is arranged in the rivet body through a thread arranged on the outside.

[0007] The volume V0 of the resin filler satisfies: Where: t c is the thickness of the composite material, L is the length of the rivet body, is the outer diameter of the rivet body, The inner diameter of the inner cavity of the rivet body ensures that the volume of the thermoplastic resin is sufficient to fill the interface gap formed by the rivet cutting the composite material.

[0008] The glue containing groove is located at the bottom of the rivet inner cavity close to the rivet cover, and the lower bottom surface position of the glue containing groove is determined according to the volume of the resin filling and the diameter of the rivet inner cavity.

[0009] The glue containing groove is provided with a thread structure, so as to achieve a fastening connection with the resin filler.

[0010] The overflow holes are evenly distributed on the side wall of the rivet body, and the total length of the overflow holes in the circumferential direction of the side wall of the rivet body is Among them: F max is the maximum axial feed force borne by the rivet during the riveting process, σ s is the yield strength of the rivet material.

[0011] The present invention relates to a composite connection method without prefabricated holes based on the semi-hollow rivet with filler, comprising:

[0012] 1) Process preparation: After the composite material plates to be connected are stacked on the metal material plates, they are stacked as a whole on the support mechanism, and the workpieces to be connected are pressed by the blank holder;

[0013] The length L of the rivet body and the thickness t of the composite material located on the upper layer c , the thickness of the metal material at the bottom layer t m Satisfy: t c <L<t c +t m , so that the rivet pierces the upper composite material plate, the nail legs achieve stir friction interlocking on the bottom workpiece, and the rivet does not penetrate the lower workpiece.

[0014] The length L0 of the thermoplastic resin in the rivet cavity satisfies: in: is the outer diameter of the rivet body, is the inner diameter of the rivet body cavity, and h is the length of the rivet cavity, so as to ensure that the chips entering the rivet cavity when the rivet penetrates the upper composite material plate can form a certain extrusion pressure on the thermoplastic resin, ensure that the molten thermoplastic resin is discharged smoothly, and do not cause excessive resistance to the flow of composite chips into the rivet cavity.

[0015] 2) Contact stage: The driving mechanism is locked with the groove on the upper surface of the rivet cap, and the driving mechanism is axially fed according to the set process parameters to make the rivet leg close to the upper surface of the composite material to be connected;

[0016] 3) Piercing stage: The driving mechanism drives the rivet to rotate at a set speed, and then the rivet moves axially at a set feed speed. The tip of the rivet leg penetrates into the upper composite material matrix and gradually completes the piercing stage;

[0017] 4) Friction stage: The rivet stirs and rubs with the upper composite material and the lower metal material, generating a large amount of heat near the rivet hole, causing the thermoplastic resin in the rivet cavity to melt. The thermoplastic resin that enters the rivet cavity is squeezed by the composite material chips and overflows through the prefabricated holes in the rivet body to the interface gap between the rivet and the composite material, bonding the broken fiber filaments together;

[0018] 5) Bonding stage: In this stage, there are two methods to fill the inner cavity thermoplastic resin to the interface between the rivet and the composite material. The first method is to keep the rivet rotating at a high speed until the lower surface of the rivet fits with the upper surface of the composite material. During this process, the thermoplastic resin in the inner cavity of the rivet is squeezed and overflowed to the interface gap between the rivet and the composite material under the combined action of the heating of the stirring friction and the composite material chips; the second method is to stop the rivet from rotating but extrude it downward at a high speed, and the thermoplastic resin is squeezed and overflowed to the interface gap between the rivet and the composite material. Finally, the rivet and the lower metal plate stop stirring and friction to generate heat, and the two form a solid phase welding interface. The molten thermoplastic resin gradually cools and bonding occurs, bonding the composite material, metal material and rivet well together;

[0019] 6) Process end: The rivet completes the connection process between the composite material and the metal material, the rotating drive shaft stops rotating, and then reverses and returns to its original position. The blank holder is released and the composite connection joint is formed. Technical Effects

[0020] The inner cavity of the rivet of the present invention is connected by a thread to realize the embedded resin filler. By accurately controlling the volume and length of the resin filler in the inner cavity of the rivet, it is ensured that the resin filler melted by heat fully fills the interface gap formed by the riveting process. Compared with the prior art, the present invention can evenly fill the riveted interface to achieve full repair of the rivet hole of the composite material; (4) The strength of the prepared joint is derived from the three connection effects of "bonding, riveting, and welding". The joint has excellent mechanical properties, good sealing of the connection interface, and good composite material repair effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the rivet of the present invention;

[0022] Figure 2 This is a schematic diagram of Example 1;

[0023] Figure 3 This is a schematic diagram of Example 2;

[0024] Figure 4 Rivet dimensions and joint profiles used for riveting experiments;

[0025] Figure 5 Single lap shear test curves of joints prepared with different process parameters. DETAILED DESCRIPTION Example 1

[0026] like Figure 1 As shown, a semi-hollow rivet with filler involved in this embodiment includes: a rivet cover 101, a rivet body 104 and a filler 105 arranged in the rivet body 104, wherein: a glue containing groove 102 is provided at the bottom of the rivet cover 101 around the rivet body 104, and a glue overflow hole 103 is provided on the side of the rivet body 104.

[0027] The filler 105 is disposed in the rivet body 104 via threads disposed on the outside.

[0028] In this embodiment, the height of the rivet cover 101 is 1.8 mm, the length L of the rivet body is 6.8 mm, the maximum height h of the inner cavity of the rivet body 104 is 8.2 mm, and the outer diameter of the rivet body is 1.8 mm. 6.0mm inner diameter It is 4.2mm.

[0029] The filler 105 is made of polyamide PA material (melting temperature ~ 210°C), with a length L0 of 4.6 mm and a volume V0 of 63.8 mm. 3 .

[0030] like Figure 2 As shown, this embodiment is based on the above-mentioned connection method of the semi-hollow rivet with filler, for a carbon fiber epoxy resin plate with a thickness of 4 mm and an aluminum alloy plate with a thickness of 4 mm, and the specific process includes:

[0031] 1) Process preparation: After the connected carbon fiber epoxy resin material plate is stacked on the aluminum alloy material plate, the whole is stacked on the support mechanism, and the workpiece to be connected is pressed by the pressure ring;

[0032] 2) Contact stage: The rivet is locked with the slot of the driving mechanism, and then axially fed at a set feed speed of 5 mm / s to make the rivet leg close to the upper surface of the carbon fiber epoxy resin material to be connected;

[0033] 3) Piercing stage: The driving mechanism drives the rivet to rotate at a set speed of 3600 rpm, and then the rivet moves axially at a set feed speed of 1 mm / s. The tip of the rivet leg penetrates into the upper carbon fiber epoxy resin material and gradually completes the piercing stage;

[0034] 4) Friction stage: After the rivet pierces the upper carbon fiber epoxy resin material, it stirs and rubs with the lower aluminum alloy plate at a rotation speed of 2400rpm and a feed speed of 8mm / s to generate heat, causing the thermoplastic resin in the rivet cavity to melt. At this time, the surface temperature of the rivet cap reaches a maximum of 225.4℃. The composite material chips entering the rivet cavity squeeze the thermoplastic resin from the overflow hole of the rivet body to the interface gap between the rivet and the carbon fiber epoxy resin material, bonding the broken fiber filaments together and forming a bonding repair interface around the rivet hole;

[0035] 5) Bonding stage: When the rivet feed amount is controlled to reach 6.8mm, the lower surface of the rivet fits the upper surface of the carbon fiber epoxy resin material just right. The rivet rotation speed is maintained at 2400rpm, and the feed speed is reduced to 0mm / s. Through the combined action of stirring friction heating and composite material chips, the heated polyamide PA material is squeezed out to the connection interface gap; the rivet completes the connection process, the rotating drive shaft is in a stopped state, and then reversely feeds back to the original position. The blank holder is released, the composite connection joint is formed, and the process ends.

[0036] In summary, the present invention is directed to a connection process for carbon fiber epoxy resin sheets and aluminum alloy sheets, and the maximum connection force under single lap shear test conditions is 7.48 kN, which is 94% higher than the 3.86 kN of traditional self-piercing riveted joints and 17% higher than the 6.37 kN of prefabricated hole core-pulling rivet joints.

[0037] like Figure 3 As shown, the rivet stirs and generates heat to melt all the thermoplastic resin in the inner cavity of the rivet, and then the rivet stops rotating but is extruded downward at a high speed so that it is squeezed and overflows into the interface gap between the rivet and the composite material.

[0038] like Figure 4 As shown, the resin filling in the inner cavity of the rivet overflows into the interface gap between the rivet and the composite material through the through hole on the side wall of the rivet under the combined action of the extrusion of the composite material chips and the stirring friction heating, thereby forming a bonding interface between the rivet and the composite material, which has the effect of repairing and bonding and sealing the composite material around the rivet hole.

[0039] like Figure 5 As shown in the figure, when the feed speed is fixed at 6mm / s, the riveting strength changes due to insufficient, moderate and excessive heat generation caused by stirring friction when the speed changes from 1200rpm, 2400rpm to 3600rpm. Similarly, the feed speed will also affect the riveting strength: when the speed is fixed at 2400rpm, the feed speed will produce excessive heat when it is too low and insufficient heat when it is too high, which will also cause significant fluctuations in the riveting strength.

[0040] Compared with the prior art, this embodiment eliminates the prefabrication process, improves the connection efficiency, reduces the axial feed force requirement for the connection equipment, introduces the bonding interface through frictional heat generation, improves the sealing and corrosion resistance of the connection joint, and the existence of the bonding interface also helps to improve the stress concentration of the connection interface. Example 2

[0041] In this embodiment, the height of the rivet cover 101 is 2 mm, the length L of the rivet body is 3.5 mm, the maximum height h of the rivet cavity is 4.2 mm, and the outer diameter of the rivet body is 4.2 mm. 5mm inner diameter It is 4.4mm.

[0042] The filler is made of polyamide PA material (melting temperature ~ 210°C), with a length L0 of 2.8mm and a volume V0 of 42.6mm. 3 .

[0043] like Figure 3 As shown, this embodiment is based on the above-mentioned connection method of the semi-hollow rivet with filler, for a carbon fiber epoxy resin plate with a thickness of 4 mm and a titanium alloy plate with a thickness of 3 mm, and the specific process includes:

[0044] 1) Process preparation: After the connected carbon fiber epoxy resin material plate is stacked on the titanium alloy material plate, the whole is stacked on the support mechanism, and the workpiece to be connected is pressed by the pressure ring;

[0045] 2) Contact stage: The rivet is locked with the slot of the driving mechanism, and then axially fed at a set feed speed of 5 mm / s to make the rivet leg close to the upper surface of the carbon fiber epoxy resin material to be connected;

[0046] 3) Piercing stage: The driving mechanism drives the rivet to rotate at a set speed of 3600 rpm, and then the rivet moves axially at a set feed speed of 1 mm / s, and the rivet gradually penetrates the carbon fiber epoxy resin material;

[0047] 4) Friction stage: After the rivet pierces the upper carbon fiber epoxy resin material, it stirs and rubs with the lower titanium alloy plate at a rotation speed of 2400rpm and a feed speed of 8mm / s to generate heat. The surface temperature of the rivet cap reaches up to 217.8℃, and the polyamide PA material melts under the heat and is squeezed into the gap of the connection interface, forming a bonding repair interface around the rivet hole;

[0048] 5) Bonding stage: The rivet stops rotating and moves downward at a feed rate of 10 mm / s to a feed amount of 4.5 mm. The polyamide PA material is squeezed out to the interface gap between the rivet and the composite material, and the composite material, metal material and rivet are well bonded together. The rivet forms a solid phase welding interface with the underlying titanium alloy plate.

[0049] In summary, the connection process of the carbon fiber epoxy resin plate and the titanium alloy plate of the present invention has a maximum connection force of 16.3kN under the single lap shear test condition, which is 114% higher than the 7.6kN of the traditional self-piercing riveted joint and 15% higher than the 14.2kN of the prefabricated hole core-pulling rivet joint.

[0050] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A semi-hollow rivet with filler, characterized in that: include: A rivet cover, a rivet body and a filler arranged in the rivet body, wherein: a glue containing groove is arranged at the bottom of the rivet cover around the rivet body, and a glue overflow hole is arranged at the side of the rivet body.

2. The semi-hollow rivet with filler according to claim 1, characterized in that: The filler is arranged in the rivet body through a thread arranged on the outside.

3. The semi-hollow rivet with filler according to claim 1, characterized in that: The volume V0 of the resin filler satisfies: Where: L is the length of the rivet body, is the outer diameter of the rivet body, The inner diameter of the inner cavity of the rivet body ensures that the volume of the thermoplastic resin is sufficient to fill the interface gap formed by the rivet cutting the composite material.

4. The semi-hollow rivet with filler according to claim 1, characterized in that: The glue containing groove is located at the bottom of the rivet inner cavity close to the rivet cover, and the lower bottom surface position of the glue containing groove is determined according to the volume of the resin filling and the diameter of the rivet inner cavity.

5. The semi-hollow rivet with filler according to claim 1, characterized in that: The glue containing groove is provided with a thread structure, so as to achieve a fastening connection with the resin filler.

6. The semi-hollow rivet with filler according to claim 1, characterized in that: The overflow holes are evenly distributed on the side wall of the rivet body, and the total length of the overflow holes in the circumferential direction of the side wall of the rivet body is Among them: F max is the maximum axial feed force borne by the rivet during the riveting process, σ s is the yield strength of the rivet material.

7. A composite connection method without prefabricated holes based on the semi-hollow rivet with filler as claimed in any one of claims 1 to 6, characterized in that: include: 1) Process preparation: After the composite material plates to be connected are stacked on the metal material plates, they are stacked as a whole on the support mechanism, and the workpieces to be connected are pressed by the blank holder; 2) Contact stage: The driving mechanism is locked with the groove on the upper surface of the rivet cap, and the driving mechanism is axially fed according to the set process parameters to make the rivet leg close to the upper surface of the composite material to be connected; 3) Piercing stage: The driving mechanism drives the rivet to rotate at a set speed, and then the rivet moves axially at a set feed speed. The tip of the rivet leg penetrates into the upper composite material matrix and gradually completes the piercing stage; 4) Friction stage: The rivet stirs and rubs with the upper composite material and the lower metal material, generating a large amount of heat near the rivet hole, causing the thermoplastic resin in the rivet cavity to melt. The thermoplastic resin entering the rivet cavity is squeezed by the composite material chips and overflows through the prefabricated holes in the rivet body to the interface gap between the rivet and the composite material, bonding the broken fiber filaments together. 5) Bonding stage: Use any of the following methods to fill the inner cavity thermoplastic resin to the interface between the rivet and the composite material: a) The rivet is rotated at a high speed until the lower surface of the rivet is in contact with the upper surface of the composite material. During this process, the thermoplastic resin in the inner cavity of the rivet is squeezed out to the interface gap between the rivet and the composite material under the combined action of the stirring friction heating and the composite material chips; b) The rivet stops rotating but is extruded downward at a high speed, and the thermoplastic resin is squeezed out to the interface gap between the rivet and the composite material. Finally, the rivet and the lower metal plate stop stirring and friction to generate heat, and the two form a solid phase welding interface. The molten thermoplastic resin gradually cools and bonding occurs, which well bonds the composite material, metal material and rivet together; 6) End of process: The rivet completes the connection process between the composite material and the metal material, the rotating drive shaft is in a stopped state, and then reverses and returns to its original position, the blank holder is released, and a composite connection joint is formed.

8. The composite connection method without prefabricated holes according to claim 7 is characterized in that: The length L of the rivet body and the thickness t of the composite material located on the upper layer c , the thickness of the metal material at the bottom layer t m Satisfy: t c <L<t c +t m .

9. The composite connection method without prefabricated holes according to claim 7 is characterized in that: The length L0 of the thermoplastic resin in the rivet cavity satisfies: in: is the outer diameter of the rivet body, is the inner diameter of the rivet body, and h is the length of the rivet inner cavity.

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