Rivet for CFRTP ultrasonic welding and riveting composite connection and connecting method

Abstract

The invention discloses a rivet for CFRTP ultrasonic welding and riveting composite connection. The rivet comprises a head part, a rivet body and a rivet body, the head part is of a cylindrical structure, the tail part is of a cylindrical structure, the tail part and the head part are integrally connected, a containing cavity is formed in the tail part, and the two ends of the containing cavity are each of an opening structure; an inner groove is formed in the inner side of the end, away from the head, of the containing cavity in the circumferential direction of the containing cavity. The invention further discloses a rivet connecting method for CFRTP ultrasonic welding and riveting composite connection, the rivet and the plate are connected together to form a weld nugget under the action of ultrasonic waves by adjusting welding parameters, and the shear strength and the peel strength of an ultrasonic welding joint are improved under the combined action of mechanical connection and interface bonding.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic welding and riveting, and more specifically, to a rivet and a connection method for CFRTP ultrasonic welding and riveting composite connection. Background Art

[0002] Continuous fiber reinforced thermoplastic composite (CFRTP) is a composite material with thermoplastic material as the matrix and carbon fiber as the reinforcement. It has the advantages of high specific strength and modulus, good thermal stability, good fatigue performance and recyclability. It has been widely used in automobile body components, brake pads, aircraft wings, fuselages and other fields.

[0003] The thermoplastic matrix of CFRTP has a high viscosity, which greatly limits the molding size of CFRTP parts. Therefore, effective connection technology has become a key technology in the manufacturing of CFRTP parts. The mainstream connection methods of carbon fiber reinforced composite materials are mainly mechanical connection, fusion, welding, etc. However, mechanical connection and traditional welding will damage the material at the connection of semi-hollow slotted rivets, leading to stress concentration and electrochemical corrosion. Bonding can avoid the above problems, but bonding requires additional surface treatment processes and a long curing time, which leads to low bonding efficiency and peel strength of bonded joints, and reduced joint stability after heating. Ultrasonic welding, as an emerging connection method for thermoplastic materials, has the advantages of forming stable connections at lower temperatures and high efficiency and cleanliness. Ultrasonic welding technology is a method of transmitting high-frequency and low-amplitude sound waves to two welded parts through a metal welding head. The two welded parts rub against each other to generate heat and melt thermoplastic plastics to form a reliable weld, but the strength of the fastening structure formed by the weld alone is low. Summary of the invention

[0004] The purpose of the present invention is to design and develop a rivet for CFRTP ultrasonic welding and riveting composite connection. The internal slotted structure can form a mechanical interlocking structure between the rivet and the CFRTP sheet, thereby increasing the peel strength and shear strength of the joint after welding.

[0005] The present invention also designs and develops a rivet connection method for CFRTP ultrasonic welding and riveting composite connection. By adjusting the welding parameters, a weld core can be formed around a semi-hollow slotted rivet with an inner groove. Combined with the mechanical interlocking formed between the rivet and the plate, the mechanical connection and the interface bonding work together to improve the strength of the ultrasonic welded joint.

[0006] The technical solution provided by the present invention is:

[0007] A rivet for CFRTP ultrasonic welding and riveting composite connection, comprising:

[0008] head; and

[0009] The tail portion is a cylindrical structure, the tail portion is integrally connected to the head portion, and a receiving cavity is provided inside the tail portion, and both ends of the receiving cavity are open structures;

[0010] Wherein, an inner groove is arranged along the circumference of the inner side of one end of the accommodating cavity away from the head.

[0011] Preferably, the head comprises a first end and a second end disposed opposite to each other;

[0012] Among them, the first end is a circular structure, the second end is a cylindrical structure, and the outer diameter of the second end is smaller than the outer diameter of the first end, the outer side of the second end smoothly extends toward the outer edge of the first end, the inner middle part of the second end is recessed toward the first end, and one end of the tail is connected to the second end.

[0013] Preferably, the inner diameter of the recess gradually decreases from the second end to the first end.

[0014] Preferably, the outer diameter of the tail portion is the same as the outer diameter of the second end.

[0015] Preferably, the other end of the accommodating cavity is engaged with the recess.

[0016] Preferably, the inner diameter of the accommodating cavity gradually decreases along the axial direction of the tail portion extending from the inner groove to the head portion.

[0017] Preferably, the total height of the head and tail is 5.20 cm, the diameter of the head is 7.75 cm, the outer diameter of the tail is 5.30 cm, the minimum inner diameter of the accommodating cavity is 3.50 cm, and the depth of the inner groove is 0.50 cm.

[0018] Preferably, the ratio of the inner diameter of the inner groove to the minimum inner diameter of the accommodating cavity is 9:7.

[0019] A rivet connection method for CFRTP ultrasonic welding and riveting composite connection, using the rivet for CFRTP ultrasonic welding and riveting composite connection, comprises the following steps:

[0020] Step 1: Fix the CFRTP sheet to be riveted in the concave die of the ultrasonic welding machine;

[0021] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0022] Step 3: Start the ultrasonic welding machine, drive the welding head to apply pressure to the rivet, and the welding is completed;

[0023] Among them, the welding time is 1.8-2.2s, the amplitude is 61-65%, the welding pressure is 0.14-0.28Mpa, and the pressure holding time after welding is 3s.

[0024] Preferably, the ultrasonic welding machine comprises a driving device, an ultrasonic transducer, a horn and a welding head.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention designs and develops a rivet for CFRTP ultrasonic welding and riveting composite connection. The semi-hollow slotted rivet with an inner groove can form a good mechanical interlocking structure with the CFRTP sheet, thereby increasing the peel strength and shear strength of the joint after welding.

[0027] (2) The rivet connection method designed and developed by the present invention for CFRTP ultrasonic welding and riveting composite connection can form a weld core around a semi-hollow slotted rivet with an inner groove, and ultrasonic welding can form a mechanical interlock between the rivet and the plate to form a rivet-weld double connection, that is, the mechanical connection and the interface bonding work together to improve the strength of the ultrasonic welded joint, thereby solving the problem of low weld strength formed by ultrasonic welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the rivet used for CFRTP ultrasonic welding and riveting composite connection according to the present invention.

[0029] Figure 2 It is a schematic diagram of the cross-sectional structure of the head of the rivet described in the present invention.

[0030] Figure 3 It is a schematic diagram of the cross-sectional structure of the rivet used for CFRTP ultrasonic welding and riveting composite connection according to the present invention.

[0031] Figure 4 This is a schematic diagram of the rivet size used for CFRTP ultrasonic welding and riveting composite connection according to the present invention.

[0032] Figure 5 Schematic diagram of the structure of the first CFRTP board in the embodiment of the present invention.

[0033] Figure 6 Schematic diagram of the structure of the first CFRTP board and the second CFRTP board in the embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of the initial welding structure of the embodiment of the present invention.

[0035] Figure 8 This is a schematic diagram of the welding completed structure of the embodiment of the present invention.

[0036] Fig. 9 This is a cross-sectional image of the finished product of Example 2 of the present invention.

[0037] Fig.10This is a top view image of the finished product of Example 2 of the present invention.

[0038] Fig.11 This is a top view image of Comparative Example 4 of the present invention.

[0039] Fig.12 This is a top view image of Comparative Example 5 of the present invention.

[0040] Fig.13 It is a bar chart diagram showing the strength comparison between Example 2 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below so that those skilled in the art can implement it according to the description.

[0042] like Figure 1 As shown, a rivet 100 for CFRTP ultrasonic welding and riveting composite connection provided by the present invention comprises:

[0043] A head portion 110 and a tail portion 120 .

[0044] like Figure 2 As shown, the head 110 includes a first end 111 and a second end 112 that are relatively arranged, the first end 111 is a circular structure, the second end 112 is a cylindrical structure, and the outer diameter of the second end 112 is smaller than the outer diameter of the first end 111, and the outer side of one end of the second end 112 smoothly extends toward the outer edge of the first end 111, and at the same time, the inner middle part of the second end 112 is recessed toward the first end 111, and the bottom of the recess is also a smooth elliptical structure.

[0045] The tail portion 120 is a cylindrical structure. A receiving cavity is disposed inside the tail portion 120 , and both ends of the receiving cavity are open structures.

[0046] The outer diameter of the tail portion 120 is the same as the outer diameter of the second end 112 , and one end of the tail portion 120 is connected to the second end 112 , so that the head portion 110 and the tail portion 120 form an integral structure.

[0047] like Figure 3 As shown, one end of the tail portion 120 is away from the head portion 110, and an inner groove 121 is provided along the circumference of the inner side of the tail portion 120 near one end, so that one end of the tail portion 120 forms a hook-shaped structure, which facilitates the rivet 100 to form a mechanical interlocking structure with the CFRTP plate.

[0048] The other end of the accommodating cavity close to the head 110 is engaged with the recess, and the inner diameter of the accommodating cavity gradually decreases along the axial direction of the tail 120 from the inner groove 121 to the head 110, and the inner diameter of the recess also gradually decreases from the second end 112 to the first end 111.

[0049] The ratio of the inner diameter of the inner groove 121 to the minimum inner diameter of the accommodating cavity is 9:7.

[0050] The rivet designed and developed by the present invention for CFRTP ultrasonic welding and riveting composite connection can more easily form a mechanical interlocking structure with the CFRTP plate during welding and riveting by using a rivet with an inner groove, thereby improving the strength of the ultrasonic welding joint structure.

[0051] The present invention also provides a rivet composite connection method for CFRTP ultrasonic welding and riveting composite connection, using a rivet for CFRTP ultrasonic welding and riveting composite connection, specifically comprising the following steps:

[0052] Step 1: Figure 5 , Figure 6 , Figure 7 As shown, one end of the first CFRTP sheet 201 to be riveted and one end of the second CFRTP sheet 202 are overlapped and placed into the female die 301 of the ultrasonic welding machine, and fixed by a clamp so that the sheets will not be displaced or rotated during the welding process;

[0053] The ultrasonic welding machine includes a driving device, an ultrasonic transducer, a horn (not shown in the figure) and a welding head 302. The ultrasonic transducer is the core component of the ultrasonic welding machine, which can convert the high-frequency electrical signal input by the ultrasonic welding machine into a mechanical vibration of the same frequency; the function of the horn is to cooperate with the ultrasonic transducer to change the vibration amplitude, and then transmit it to the weldment in a direction parallel to the contact surface after being amplified by the horn; the driving device drives the welding head 302 to move downward to approach or be close to the rivet 100. The welding head 302 is cylindrical in shape and is used to transmit ultrasonic high-frequency vibration to the weldment to be welded.

[0054] Step 2: Place the rivet 100 at the center of the overlapping area of ​​the CFRTP plate;

[0055] Step 3: Figure 8 As shown, the ultrasonic welding machine is started, the welding head is driven to apply pressure to the rivet, and the welding is completed;

[0056] Among them, the welding time is 1.8-2.2s, the amplitude is 61-65%, the welding pressure is 0.14-0.28Mpa, and the pressure holding time after welding is 3s.

[0057] Example 1

[0058] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0059] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0060] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0061] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0062] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0063] Among them, the welding time is 1.8s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0064] Example 2

[0065] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0066] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0067] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0068] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0069] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0070] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0071] Example 3

[0072] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0073] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0074] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0075] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0076] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0077] Among them, the welding time is 2.0s, the amplitude is 65%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0078] Example 4

[0079] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0080] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0081] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0082] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0083] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0084] Among them, the welding time is 2.0s, the amplitude is 61%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0085] Example 5

[0086] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0087] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0088] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0089] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0090] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0091] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.28Mpa, and the pressure holding time after welding is 3s.

[0092] Example 6

[0093] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0094] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0095] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0096] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0097] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0098] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.14Mpa, and the pressure holding time after welding is 3s.

[0099] Example 7

[0100] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0101] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0102] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0103] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0104] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0105] Among them, the welding time is 2.2s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0106] Comparative Example 1

[0107] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0108] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0109] Step 2: Start the ultrasonic welding machine, drive the welding head to move vertically downward, perform rivet-free ultrasonic welding on the first CFRTP sheet and the second CFRTP sheet, and complete the welding;

[0110] Among them, the welding time is 1.8s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0111] Comparative Example 2

[0112] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0113] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0114] Step 2: Start the ultrasonic welding machine, drive the welding head to move vertically downward, perform rivet-free ultrasonic welding on the first CFRTP sheet and the second CFRTP sheet, and complete the welding;

[0115] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0116] Comparative Example 3

[0117] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0118] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0119] Step 2: Start the ultrasonic welding machine, drive the welding head to move vertically downward, perform rivet-free ultrasonic welding on the first CFRTP sheet and the second CFRTP sheet, and complete the welding;

[0120] Among them, the welding time is 2.2s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0121] Comparative Example 4

[0122] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0123] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0124] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0125] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0126] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0127] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.10Mpa, and the pressure holding time after welding is 3s.

[0128] Comparative Example 5

[0129] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0130] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0131] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0132] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0133] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0134] Among them, the welding time is 2.0s, the amplitude is 63%, the welding pressure is 0.34Mpa, and the pressure holding time after welding is 3s.

[0135] Comparative Example 6

[0136] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0137] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0138] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0139] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0140] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0141] Among them, the welding time is 1.5s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0142] Comparative Example 7

[0143] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0144] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0145] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0146] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0147] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0148] Among them, the welding time is 2.5s, the amplitude is 63%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0149] Comparative Example 8

[0150] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0151] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0152] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0153] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0154] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0155] Among them, the welding time is 2.0s, the amplitude is 56%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0156] Comparative Example 9

[0157] Step 1: overlap one end of the first CFRTP sheet to be riveted and one end of the second CFRTP sheet, place them into the concave die of the ultrasonic welding machine, and fix them with a clamp so that the sheets will not move or rotate during the welding process;

[0158] The dimensions of the first CFRTP sheet and the second CFRTP sheet are both 100 mm × 25 mm × 3 mm.

[0159] Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets.

[0160] The size of the rivet is Ф7.8×5.2mm (including tolerance).

[0161] Step 3, start the ultrasonic welding machine, drive the welding head to move vertically downward, apply pressure to the rivet, so that the rivet penetrates the first CFRTP sheet and the second CFRTP sheet under the action of the welding pressure, and the welding is completed;

[0162] Among them, the welding time is 2.0s, the amplitude is 70%, the welding pressure is 0.21Mpa, and the pressure holding time after welding is 3s.

[0163] The strength of the CFRTP plates obtained by ultrasonic welding and riveting composite connection in Examples 1-7 and Comparative Examples 1-9 was tested, as shown in Table 1.

[0164] Table 1 Ultrasonic welding and riveting CFRTP sheet strength of the embodiment and the comparative example

[0165]

[0166]

[0167] Among them, it can be seen from Table 1 that the best welding parameters are in Example 2. The peel strength and shear strength of the CFRTP sheet obtained after ultrasonic welding and riveting composite connection are the highest. Regardless of whether the welding time is extended or shortened, the peel strength and shear strength are reduced. The increase or decrease of the amplitude and welding pressure also affects the peel strength and shear strength. However, the peel strength and shear strength of the CFRTP sheet after ultrasonic welding and riveting composite connection obtained in Examples 1-7 are higher than the peel strength and shear strength of the ultrasonically welded CFRTP sheet obtained in the comparative example.

[0168] The effects of welding time, amplitude, welding pressure and post-weld holding time on the strength of the joint after welding are coupled. Applying appropriate welding pressure to the CFRTP sheet can make the upper and lower sheets stacked tightly together. The pressure during welding can accelerate the flow of molten resin and inhibit the formation of gaps in the weld during the resin flow process. Therefore, selecting appropriate welding pressure is a necessary condition for obtaining high-quality welds. When the welding pressure is less than 0.14Mpa, it is very easy for the half-slotted hollow rivet to fail to be pressed into the sheet. The joint strength increases rapidly with the increase of pressure, but when it exceeds the optimal pressure value, the joint strength decreases rapidly with the increase of pressure. Fig.11 As shown in the figure, the welding pressure is too small (0.1Mpa), so the half-slotted hollow rivet cannot be pressed into the plate, and a qualified welding and riveting composite connection joint cannot be formed; Fig.12 As shown in the figure, the excessive welding pressure (0.34Mpa) causes excessive extrusion of material around the rivet, causing damage to the resin matrix and reducing the strength of the welded joint.

[0169] Process parameters such as welding time, amplitude and post-weld holding time can together affect the total welding energy. When the total welding energy is lower than the optimal welding energy, the resin may not be completely melted and the welding joint may not be formed well. As shown in Comparative Examples 6 and 8, under the premise that other welding process parameters remain unchanged, the welding energy generated by a welding time of 1.5s and an amplitude of 56% is not enough to melt the plate near the rivet, and the rivet cannot penetrate the plate to form a stable welded and riveted composite connection joint, and its strength cannot reach the expected target; when the total welding energy is higher than the optimal welding energy, cracks and voids will appear in the heat-affected zone of the joint, which will also lead to a decrease in the strength of the joint. As shown in Comparative Examples 7 and 9, under the premise that other welding process parameters remain unchanged, a welding time of 2.5s and an amplitude of 70% will result in excessive welding energy, causing excessive thermal decomposition of the resin matrix of the CFRTP, resulting in a decrease in its strength. Therefore, the welding process parameters selected by the present invention can generate optimal welding energy, promote the material flow on the sinking trajectory of the semi-hollow slotted rivet, and at the end of the semi-hollow slotted rivet stroke, the molten material and the semi-hollow slotted rivet are completely fitted together. Since the semi-hollow slotted rivet has an inner groove, the semi-hollow slotted rivet and the CFRTP plate form a better mechanical interlocking structure.

[0170] like Fig.13 As shown, it is a strength comparison bar chart of Example 2 and Comparative Example 1. It can be seen that compared with the ultrasonic welded joint, the peel strength and shear strength of the ultrasonic welding-riveting composite connection joint are increased by 40% and 30% respectively. The improvement in the strength of the ultrasonic welded joint is the result of the weld core formed around the rivet and the mechanical interlocking formed between the rivet and the plate, that is, the mechanical connection and interface bonding work together to improve the strength of the ultrasonic welded joint.

[0171] The present invention designs and develops a rivet composite connection method for CFRTP ultrasonic welding and riveting composite connection, which can form a weld core around a semi-hollow slotted rivet with an inner groove, and ultrasonic welding can form a mechanical interlock between the rivet and the plate to form a rivet-weld double connection, that is, the mechanical connection and the interface bonding work together to improve the strength of the ultrasonic welded joint, thereby solving the problem of low weld strength formed by ultrasonic welding.

[0172] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A rivet for CFRTP ultrasonic welding and riveting composite connection, characterized in that: include: head; as well as The tail portion is a cylindrical structure, the tail portion is integrally connected to the head portion, and a receiving cavity is provided inside the tail portion, and both ends of the receiving cavity are open structures; Wherein, an inner groove is arranged along the circumference of the inner side of one end of the accommodating cavity away from the head.

2. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 1, characterized in that: The head includes a first end and a second end that are arranged opposite to each other; Among them, the first end is a circular structure, the second end is a cylindrical structure, and the outer diameter of the second end is smaller than the outer diameter of the first end, the outer side of the second end smoothly extends toward the outer edge of the first end, the inner middle part of the second end is recessed toward the first end, and one end of the tail is connected to the second end.

3. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 2, characterized in that: The inner diameter of the recess gradually decreases from the second end to the first end.

4. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 3, characterized in that: The outer diameter of the tail portion is the same as the outer diameter of the second end.

5. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 4, characterized in that: The other end of the accommodating cavity is engaged with the recess.

6. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 5, characterized in that: The inner diameter of the accommodating cavity gradually decreases along the axial direction of the tail portion extending from the inner groove to the head portion.

7. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 6, characterized in that: The total height of the head and tail is 5.20 cm, the diameter of the head is 7.75 cm, the outer diameter of the tail is 5.30 cm, the minimum inner diameter of the accommodating cavity is 3.50 cm, and the depth of the inner groove is 0.50 cm.

8. The rivet for CFRTP ultrasonic welding and riveting composite connection according to claim 7, characterized in that: The ratio of the inner diameter of the inner groove to the minimum inner diameter of the accommodating cavity is 9:

7.

9. A rivet connection method for CFRTP ultrasonic welding and riveting composite connection, using the rivet for CFRTP ultrasonic welding and riveting composite connection according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Fix the CFRTP sheet to be riveted in the concave die of the ultrasonic welding machine; Step 2: Place the rivets at the center of the overlapping area of ​​the CFRTP sheets. Step 3: Start the ultrasonic welding machine, drive the welding head to apply pressure to the rivet, and the welding is completed; Among them, the welding time is 1.8-2.2s, the amplitude is 61-65%, the welding pressure is 0.14-0.28Mpa, and the pressure holding time after welding is 3s.

10. The rivet connection method for CFRTP ultrasonic welding and riveting composite connection according to claim 9, characterized in that: The ultrasonic welding machine comprises a driving device, an ultrasonic transducer, a horn and a welding head.

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