Half hollow rivet with resin filling

Abstract

A kind of half hollow rivet with resin filler, comprising: rivet cover, rivet body and filler arranged in rivet body, wherein: the bottom of rivet cover is provided with glue groove around rivet body, the side of rivet body is provided with overflow glue hole, and the filler is arranged in rivet body by the thread arranged outside.The rivet with improved internal structure is used to realize the composite connection of composite material and metal material.According to the different thickness material scene, rivet with different internal cavity structure can be used to achieve the effect of accommodating composite material chips and filling the defects such as connection interface cracks, avoiding the influence of chips on appearance quality, and weakening the overall strength and corrosion resistance of connection interface cracks.

Description

Technical Field

[0001] This invention relates to a technology in the field of machining, specifically a semi-hollow rivet with resin filler. Background Technology

[0002] Composite materials are widely used in aerospace, automotive, and shipbuilding industries as lightweight reinforcing parts. However, traditional riveting techniques are prone to damage to composite materials, deformation of metal materials, or brittle fracture. Fusion welding is only suitable for thermoplastic composite materials and is prone to defects such as porosity and cracks, making it difficult to obtain high-performance joints. Existing rivets cannot avoid substrate damage and fiber delamination when penetrating thermoplastic fiber-reinforced metal laminates. Additional heating devices are needed to heat the thermoplastic resin inside the rivet cavity. The content of thermoplastic resin in the rivet cavity cannot be precisely controlled or adjusted in mass production to fill and repair the mechanical riveting interface. The molten thermoplastic resin flows out through the through-hole only due to the extrusion of material debris, making it difficult to evenly and fully fill the riveting interface. The resulting adhesive seal is poor, and the joint strength depends on the mechanical locking between the rivet and the materials to be joined, resulting in low peel strength. Summary of the Invention

[0003] This invention addresses the problems of fiber filament separation and numerous cracks near rivet holes in existing riveting and welding processes when joining composite materials. It proposes a semi-hollow rivet with resin filler, utilizing the improved internal structure of the rivet to achieve a composite connection between composite and metal materials. Depending on the material thickness, rivets with different internal cavity structures can be used, thereby accommodating composite material chips and filling defects such as cracks at the connection interface. This avoids the impact of chips on appearance quality and the weakening of overall strength and corrosion resistance caused by cracks at the connection interface.

[0004] This invention is achieved through the following technical solution:

[0005] The present invention relates to a semi-hollow rivet with filler, comprising: a rivet cap, a rivet body, and filler disposed in the rivet body, wherein: the bottom of the rivet cap is provided with an adhesive groove surrounding the rivet body, and the side of the rivet body is provided with an adhesive overflow hole.

[0006] The filler is disposed in the rivet body via external threads.

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

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

[0009] The glue containing groove is provided with a threaded structure, so as to realize the fastening connection with the resin filling.

[0010] The glue overflow hole is uniformly distributed on the side wall of the rivet body in the circumferential direction, and the total length of the glue overflow hole in the circumferential direction of the side wall of the rivet body is Wherein: F max The maximum axial feed force borne by the rivet during riveting, σ s The yield strength of the rivet material.

[0011] The present application relates to a kind of based on the above-mentioned filled half hollow rivet without pre-punched hole composite connection method, comprising:

[0012] 1) Process preparation: after the composite material plate to be connected is placed on the metal material plate, the whole stack is placed on the supporting mechanism, and the workpiece to be connected is pressed by the edge ring;

[0013] The length L of the rivet body and the thickness t of the composite material located in the upper layer c The thickness t of the metal material located in the lower layer m Satisfy: t c <L<t c +t m So as to realize that the rivet pierces the upper layer of composite material plate, the rivet leg realizes friction stir interlocking in the lowermost layer workpiece, and the rivet does not penetrate the lower layer workpiece.

[0014] The length L0 of the thermoplastic resin in the rivet cavity satisfies: Wherein: The outer diameter of the rivet body, The inner diameter of the rivet body cavity, h is the length of the rivet cavity, so as to ensure that the cutting chip entering the rivet cavity when the rivet penetrates the upper layer of composite material plate can form a certain extrusion force on the thermoplastic resin, so as to ensure that the molten thermoplastic resin is smoothly discharged, and does not cause too much resistance to the flow of composite material cutting chip to 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, so that the rivet leg approaches 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 moves the rivet axially at a set feeding speed, the rivet leg tip pierces 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, a large amount of heat is generated near the rivet hole, and the thermoplastic resin in the rivet cavity is melted by heat. The thermoplastic resin entering the rivet cavity is extruded by the composite material chips and overflowed to the interface gap between the rivet and the composite material through the preformed hole of the rivet body, so as to bond the broken fiber filaments together;

[0018] 5) bonding stage: there are two methods to fill the cavity thermoplastic resin to the interface between the rivet and the composite material, method one is that the rivet keeps rotating until the lower surface of the rivet is attached to the upper surface of the composite material, and in the process, the thermoplastic resin in the rivet cavity is extruded and overflowed to the interface gap between the rivet and the composite material under the combined action of stirring and rubbing heating and composite material chips; method two is that the rivet stops rotating but is extruded downward at high speed, and the thermoplastic resin is extruded and overflowed to the interface gap between the rivet and the composite material. Finally, the rivet and the lower metal plate stop stirring and rubbing to generate heat, and a solid-phase welded interface is formed between the two. The molten thermoplastic resin gradually cools and bonds, and the composite material, the metal material and the rivet are well bonded together;

[0019] 6) process end: the rivet completes the connection process of the composite material and the metal material, the rotating drive shaft is in a stopped rotating state, and then is fed in reverse to return to the original position. The edge ring is released, and the composite connection joint is formed.

[0020] Technical effects

[0021] The rivet body cavity of the rivet is internally provided with resin filling by thread connection. By accurately controlling the volume and length of the resin filling in the rivet cavity, it is ensured that the resin filling melted by heat fully fills the interface gap formed in the riveting process. Compared with the prior art, the rivet can uniformly fill the riveting interface and fully repair the composite material rivet hole. The strength of the prepared joint is derived from the three connecting 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 DRAWINGS

[0022] Figure 1 It is a schematic view of the rivet of the present application;

[0023] Figure 2 It is a schematic view of Example 1;

[0024] Figure 3 It is a schematic view of Example 2;

[0025] Figure 4 The riveting dimensions and joint cross-section used for the riveting experiment;

[0026] Figure 5 Single-lap shear test curves of joints prepared for different process parameters. Detailed Implementation

[0027] Example 1

[0028] like Figure 1 As shown, this embodiment relates to a semi-hollow rivet with filler, including: a rivet cover 101, a rivet body 104, and filler 105 disposed in the rivet body 104, wherein: the bottom of the rivet cover 101 is provided with an adhesive groove 102 surrounding the rivet body 104, and the side of the rivet body 104 is provided with an adhesive overflow hole 103.

[0029] The filler 105 is disposed inside the rivet body 104 by means of external threads.

[0030] In this embodiment, the height of the rivet cap 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... 6.0mm inner diameter It is 4.2mm.

[0031] The filler 105 is made of polyamide (PA) material (melting temperature ~210℃), with a length L0 of 4.6 mm and a volume V0 of 63.8 mm². 3 .

[0032] like Figure 2 As shown, this embodiment, based on the above-mentioned connection method using semi-hollow rivets with filler, specifically addresses a 4mm thick carbon fiber epoxy resin plate and a 4mm thick aluminum alloy plate. The specific process includes:

[0033] 1) Process preparation: After stacking the connecting carbon fiber epoxy resin material plate on the aluminum alloy material plate, the whole stack is placed on the support mechanism, and the workpiece to be connected is pressed by the pressure ring.

[0034] 2) Contact stage: Lock the rivet into the slot of the drive mechanism, and then feed axially at the set feed speed of 5mm / s to bring the rivet leg close to the upper surface of the carbon fiber epoxy resin material to be connected.

[0035] 3) Puncture stage: The drive 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 the upper carbon fiber epoxy resin material and gradually completes the puncture stage.

[0036] 4) Friction stage: After the rivet pierces the upper carbon fiber epoxy material, the lower aluminum alloy plate is subjected to friction stir action at a rotation speed of 2400 rpm and a feed speed of 8 mm / s to generate heat, which melts the thermoplastic resin in the rivet cavity. At this time, the surface temperature of the rivet cap reaches 225.4°C. The composite chip entering the rivet cavity is extruded to cause the thermoplastic resin to overflow from the rivet body overflow hole to the interface gap between the rivet and the carbon fiber epoxy material, bonding the broken fiber filaments together and forming a bonding repair interface around the rivet hole.

[0037] 5) Bonding stage: When the rivet feed amount reaches 6.8 mm, the lower surface of the rivet just fits the upper surface of the carbon fiber epoxy material. The rotation speed of the rivet is maintained at 2400 rpm, and the feed speed is reduced to 0 mm / s. The heated polyamide PA material is extruded and overflowed to the connection interface gap under the combined action of friction heating and composite chip extrusion. The rivet completes the connection process, the rotary drive shaft is in a stopped rotating state, and then the reverse feed is returned to the original position. The binder ring is released, the composite connection joint is formed, and the process is completed.

[0038] In summary, the present application is aimed at the connection process of carbon fiber epoxy plate and aluminum alloy plate. Under single lap shear test conditions, the maximum connection force is 7.48 kN, which is 94% higher than the traditional self-punching rivet joint of 3.86 kN and 17% higher than the pre-punched core rivet joint of 6.37 kN.

[0039] As shown in Figure 3 , the friction stir heating of the rivet causes the thermoplastic resin in the rivet cavity to melt completely. Then the rivet stops rotating but is extruded downward at high speed, causing it to be extruded and overflowed to the interface gap between the rivet and the composite material.

[0040] As shown in Figure 4 , the resin filler in the rivet cavity is extruded and overflowed to the interface gap between the rivet and the composite material under the combined action of composite chip extrusion and friction stir heating, thereby forming a bonding interface between the rivet and the composite material, repairing and bonding the composite material around the rivet hole.

[0041] As shown in Figure 5 , when the feed speed is fixed at 6 mm / s, the rotation speed varies from 1200 rpm, 2400 rpm to 3600 rpm, which causes the rivet strength to change due to insufficient, moderate and excessive friction stir heating. Similarly, the feed speed also affects the rivet strength: when the rotation speed is fixed at 2400 rpm, the feed speed is small, the heating is excessive, and the feed speed is large, the heating is insufficient, which also causes the rivet strength to fluctuate significantly.

[0042] Compared with the prior art, this embodiment eliminates the pre-drilling process, improves connection efficiency, reduces the axial feed force required for the connection equipment, introduces heat through friction to the bonding interface, improves the sealing and corrosion resistance of the connection joint, and the presence of the bonding interface also helps to improve stress concentration at the connection interface.

[0043] Example 2

[0044] In this embodiment, the rivet cap 101 has a height of 2mm, the rivet body length L is 3.5mm, the maximum height h of the rivet cavity is 4.2mm, and the outer diameter of the rivet body is... 5mm inner diameter It is 4.4mm.

[0045] The filler is made of polyamide (PA) material (melting temperature ~210℃), with a length L0 of 2.8 mm and a volume V0 of 42.6 mm². 3 .

[0046] like Figure 3 As shown, this embodiment, based on the above-mentioned connection method with semi-hollow rivets containing filler, specifically applies to a 4mm thick carbon fiber epoxy resin plate and a 3mm thick titanium alloy plate. The specific process includes:

[0047] 1) Process preparation: After stacking the connecting carbon fiber epoxy resin material plate on the titanium alloy material plate, the whole stack is placed on the support mechanism, and the workpiece to be connected is pressed by the pressure ring.

[0048] 2) Contact stage: Lock the rivet into the slot of the drive mechanism, and then feed axially at the set feed speed of 5mm / s to bring the rivet leg close to the upper surface of the carbon fiber epoxy resin material to be connected.

[0049] 3) Piercing stage: The drive 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 pierces the carbon fiber epoxy resin material.

[0050] 4) Friction stage: After the rivet pierces the upper carbon fiber epoxy resin material, it generates heat through stirring friction with the lower titanium alloy plate at a rotation speed of 2400 rpm and a feed speed of 8 mm / s. The surface temperature of the rivet head reaches a maximum of 217.8℃. The polyamide PA material is heated and melted and extruded into the gap of the connection interface, forming an adhesive repair interface around the rivet hole.

[0051] 5) bonding stage: rivet stops rotating, moves downward at a feeding speed of 10 mm / s to a position with a feeding amount of 4.5 mm, polyamide PA material is extruded to overflow to the interface gap between the rivet and the composite material, and the composite material, the metal material and the rivet are well bonded together. The rivet and the lower titanium alloy plate form a solid-phase welding interface.

[0052] To sum up, the application is aimed at the connection process of carbon fiber epoxy resin plate and titanium alloy plate, and the maximum connection force is 16.3 kN under the condition of single lap shear test, which is increased by 114% compared with 7.6 kN of the traditional self-punch riveting joint and increased by 15% compared with 14.2 kN of the pre-hole core-pulling riveting joint.

[0053] The above specific embodiments can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the application, the protection scope of the application is subject to the claims and is not limited by the above specific embodiments, and each implementation scheme within the scope is subject to the constraints of the application.

Claims

1. A semi-hollow rivet with filler, characterized in that, The rivet cap, the rivet body and the filler arranged in the rivet body, wherein: the bottom of the rivet cap is provided with a glue groove around the rivet body, the side of the rivet body is provided with a glue overflow hole, the filler is arranged in the rivet body through the thread arranged outside, the glue groove is located at the bottom of the rivet cavity and close to the position of the rivet cap, and the lower bottom position of the glue groove is determined according to the volume of the resin filler and the diameter of the rivet cavity. The glue groove is provided with a thread structure, so as to realize the fastening connection with the resin filler. The volume of the resin filler satisfies: wherein: is the rivet body length, is the rivet body outer diameter, is the rivet body inner diameter, so as to ensure that the volume of the thermoplastic resin is sufficient to fill the interface gap formed by the rivet cutting composite material; The method comprises the following steps: The length L of the rivet body and the thickness of the composite material located in the upper layer , the thickness of the metal material located in the lower layer satisfies: ; The length of the rivet inner cavity thermoplastic resin satisfies: wherein: is the outer diameter of the rivet body, is the inner diameter of the rivet body inner cavity, is the rivet inner cavity length.

2. The filled semi-tubular rivet of claim 1, wherein, The overflow glue holes are evenly distributed in the circumferential direction of the rivet body side wall wherein: is the maximum axial feed force borne by the rivet during the riveting process, is the yield strength of the rivet material.

3. A pre-holeless composite joining method with a filled semi-hollow rivet according to claim 1 or 2, characterized by, 1) process preparation: after the composite material plate to be connected is placed on the metal material plate, the whole is placed on the supporting mechanism, and the workpiece to be connected is pressed tightly by the edge ring; 2) contact stage: the driving mechanism is clamped and locked with the groove on the upper surface of the rivet cap, the driving mechanism feeds axially according to the set process parameters, and the rivet leg approaches 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 makes the rivet move axially at a set feeding speed, so that the rivet leg tip pierces into the upper layer of the composite material matrix and gradually completes the piercing stage; 4) friction stage: the rivet and the upper layer of the composite material and the lower layer of the metal material are subjected to stirring friction, a large amount of heat is generated near the rivet hole, the thermoplastic resin in the rivet cavity is melted by the heat, the thermoplastic resin in the rivet cavity is extruded by the cutting chips of the composite material and overflowed to the interface gap between the rivet and the composite material through the prefabricated hole of the rivet body, and the broken fiber filaments are bonded together; 5) bonding stage: the following any method is used to fill the thermoplastic resin in the cavity to the interface between the rivet and the composite material: a) the rivet keeps high-speed rotation until the lower surface of the rivet is attached to the upper surface of the composite material, in the process, the thermoplastic resin in the rivet cavity is extruded and overflowed to the interface gap between the rivet and the composite material under the combined action of stirring friction and the cutting chips of the composite material; b) the rivet stops rotating but extrudes downward at high speed, the thermoplastic resin is extruded and overflowed to the interface gap between the rivet and the composite material, finally, the rivet and the lower layer of the metal plate stop stirring friction to generate heat, and a solid phase welding interface is formed between the two, the molten thermoplastic resin gradually cools and is bonded, and the composite material, the metal material and the rivet are well bonded together; 6) process end: the rivet completes the connection process of the composite material and the metal material, the rotating driving shaft is in a stopped rotating state, and then reversely feeds back to the original position, the edge ring is released, and the composite connection joint is formed. ​

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