CN110641027A - Point joining method for long fiber reinforced thermoplastic composites and dissimilar materials - Google Patents

Abstract

The invention relates to a point connection method for long fiber reinforced thermoplastic composite material and dissimilar materials: (1) prefabricating cylindrical bosses on the surface of long fiber reinforced thermoplastic composite material, and connecting the material with the long fiber reinforced thermoplastic composite material The upper surface is provided with a circular truncated hole with a thread on the inner wall; (2) the long fiber reinforced thermoplastic composite material is used as the upper plate, and the material connected to it is used as the lower plate, which is fixed with a clamp; (3) The external auxiliary stationary shaft shoulder is driven to move down to contact with the upper plate; (4) start the ultrasonic system to preheat the connecting parts; (5) drive the needleless stirring head to rotate and lower, and the lowering amount is not greater than the height of the cylindrical boss; (6) connect the needleless stirring head and the external The auxiliary static shoulder is moved up, the ultrasonic system is turned off, and the test piece is removed after cooling to room temperature; the invention does not destroy the carbon fiber structure of the long-fiber reinforced thermoplastic composite material during the connection process, can realize the connection without thinning, and can increase the number of joints mechanical interlocking capability.

Description

Point joining method for long fiber reinforced thermoplastic composites and dissimilar materials

technical field

The invention belongs to the technical field of point connection between thermoplastic composite materials and dissimilar materials, and particularly relates to a point connection method for long fiber reinforced thermoplastic composite materials and dissimilar materials.

Background technique

Metals, ceramics, thermosetting polymers and wood materials are the most widely used materials in the manufacturing field. Thermoplastic polymers have the characteristics of high specific strength, good dimensional stability and good fatigue resistance, and have also been widely used in the field of manufacturing. Therefore, the connection structure between thermoplastic composite materials and other materials is difficult to avoid. Since the thermophysical properties of composite materials and metals, ceramics and other materials are quite different, the connection of the two is difficult. At present, the connection methods of long fiber reinforced thermoplastic composite materials and dissimilar materials include adhesive bonding and mechanical connection.

Chinese invention patent (publication number: CN 106515023 A, publication date: March 22, 2017) invented a kind of opening hole in the metal plate, plug the prepreg into the prefabricated hole, and finally carry out curing molding in the molding die , but the curing process in this method is complicated and takes a long time.

Chinese invention patent (publication number: CN108547836A, publication date: September 18, 2018) invented a method of combining structural adhesive and fastening connection to connect carbon fiber composite materials and dissimilar materials, but the prefabricated holes in this method will The carbon fiber structure in the composite material is seriously damaged, and the composite material will have problems such as delamination failure and matrix cracking.

Chinese invention patent (publication number: CN108547836A, publication date: September 18, 2018) invented a rivet-free riveting device between dissimilar materials based on the principle of hot melt. In this method, a hot-melt drill is used to melt the composite material and pass through the prefabricated holes of the lower plate, and a rivet-free connection is formed on the back of the lower plate by a light column upsetting. This method can reduce the weight of the structure and has high production efficiency, but there will be holes in the joints, the effective connection area is small, and it cannot withstand large forces. At the same time, higher temperatures will have a greater impact on the base material.

Although the above method can connect long fiber reinforced thermoplastic composite materials and dissimilar materials, complex surface treatment and long curing time are required in the bonding; the prefabricated hole process in the mechanical connection will destroy the long fiber structure in the composite material, reducing The area of the connection area is increased, while the area of stress concentration is increased. Therefore, there is an urgent need for a connection method for long fiber reinforced thermoplastic composite materials and dissimilar materials to solve the above problems.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides a point connection method for long fiber reinforced thermoplastic composite material and dissimilar materials, which has the advantage of not destroying the carbon fiber structure of the long fiber reinforced thermoplastic composite material during the connection process.

A point connection method for long fiber reinforced thermoplastic composite materials and dissimilar materials, which specifically comprises the following steps:

Step 1: A cylindrical boss is prefabricated on the surface of the long fiber reinforced thermoplastic composite material, and the upper surface of the dissimilar material connected with the long fiber reinforced thermoplastic composite material is provided with a circular truncated hole with a thread on the inner wall;

Step 2: Place the parts to be connected on the workbench, the long fiber reinforced thermoplastic composite material is used as the upper plate, and the dissimilar material connected with the long fiber reinforced thermoplastic composite material is used as the lower plate, which is fixed with a clamp and placed on the bottom surface of the lower plate. Ultrasonic luffing lever, at this time keep the needleless stirring head in contact with the upper surface of the cylindrical boss in the upper plate;

Step 3: Drive the external auxiliary stationary shoulder to move down until it contacts the upper plate;

Step 4: Start the ultrasonic system to preheat the material to be connected for 5s to 30min, the ultrasonic vibration power is 60-2000W, and the amplitude is 15-55μm;

Step 5: After preheating, drive the needleless stirring head to rotate at a speed of 50 to 8000 rpm, and tie down at a speed of 0.1 to 10 mm/min. The lowering amount is not greater than the height of the cylindrical boss. Rotate and stay for 1 to 120s for welding;

Step 6: After welding, move the needleless stirring head and the external auxiliary static shaft shoulder up, turn off the ultrasonic system, and remove the test piece after cooling to room temperature.

The diameter of the needleless stirring head is 1-50 mm larger than the diameter of the boss, and the height of the cylindrical boss is 0.5-20 mm.

The diameter of the upper bottom of the circular truncated hole in the step 1 is 5-70% of the diameter of the needleless stirring head, the diameter of the lower bottom of the circular truncated hole is 5-80% of the diameter of the needleless stirring head, and the area of the upper bottom of the circular truncated hole is less than Lower bottom area in order to increase the bending resistance of the joint.

The circular truncated holes are evenly distributed in the spot welding area to improve the torsion resistance of the joint, and the specific number is designed according to needs.

The volume of the prefabricated cylindrical boss is larger than the total volume of the multi-circular truncated holes in the lower plate, so as to ensure that the lower plate multi-circular truncated holes can be fully filled, and at the same time, a welded joint with high surface quality can be obtained.

The lower plate material may be metal, ceramic, thermoplastic polymer, thermosetting polymer or wood material.

The method can also be used for the joining of short fiber reinforced thermoplastic composites, particle reinforced thermoplastic composites, thermoplastic polymer materials and dissimilar materials.

The beneficial effects of the present invention are:

1. The present invention provides heat for the joint by means of friction stir, and the upsetting effect of the needleless stirring head and the external auxiliary static shoulder can improve the flow of the material along the thickness direction, which is conducive to filling the truncated hole with the material. At the same time, the ultrasonic auxiliary method can Increase the temperature at the interface and promote the flow of materials, effectively avoiding the incomplete filling of the truncated hole in the lower plate;

2. In the present invention, a prefabricated cylindrical boss is arranged on the upper plate, and the needleless stirring head is used for welding, which can realize the connection without thinning;

3. In the present invention, the external auxiliary static shaft shoulder first acts on the upper plate, and is preheated by ultrasonic, so as to solve the problem of poor thermal conductivity of the upper plate composite material;

4. In the present invention, the static shaft shoulder is pre-forged on the upper plate, which can effectively avoid the flow of the material at the boss along the direction of the upper surface of the material, and further ensure that the material at the boss can effectively fill the truncated hole of the lower plate;

5. In the process of connecting the long-fiber reinforced composite materials in the present invention, since the depth of the needleless stirring head is not greater than the height of the prefabricated cylindrical boss, it will not cause damage to the long fibers in the upper plate;

6. The number and size of the circular truncated holes in the present invention can be designed according to the area of the connection area to ensure the torsion resistance of the joint; the cylindrical boss has a narrow top and a wide bottom, which can improve the anti-peeling ability of the joint; in addition , adding threads on the inner surface of the truncated hole can improve the mechanical interlocking effect of the connection area.

Description of drawings

Fig. 1 is the connection schematic diagram before welding of the present invention;

Fig. 2 is the top view of the material to be connected after assembling before welding in the present invention;

Fig. 3 is the A-A direction view of Fig. 2;

in,

1 Needleless stirring head, 2 External auxiliary stationary shoulder, 3 Upper plate, 4 Lower plate, 5 Ultrasonic horn, 6 Conical hole, 7 thread.

Detailed ways

In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention will be described in detail below with reference to the accompanying drawings and through specific embodiments.

Example 1

As shown in Figures 1-3, in this embodiment, the present invention is used to connect the glass fiber reinforced PEI composite material and 2024 aluminum alloy. The height of the surface boss of the glass fiber reinforced PEI composite material is 3 mm and the radius is 15 mm; the diameter of the needleless stirring head 1 The diameter of the cylindrical boss on the surface of the composite material is 2mm; the radii of the upper bottom and the lower bottom of the circular truncated hole 6 opened on the surface of the 2024 aluminum alloy are 3mm and 5mm respectively. The external auxiliary static shoulder 2 and the needleless stirring head 1 used in the welding And the ultrasonic amplitude rod 5 is driven by different systems respectively, and the specific steps of connection are as follows:

Step 1: A cylindrical boss is prefabricated on the surface of the glass fiber reinforced PEI composite material, and a circular truncated hole 6 with a thread 7 on the inner wall is opened on the upper surface of the 2024 aluminum alloy;

Step 2: Put the parts to be connected on the workbench, the glass fiber reinforced PEI composite material is used as the upper plate 3, the 2024 aluminum alloy is used as the lower plate 4, and the clamps are used for fixing and the ultrasonic horn 5 is placed on the bottom surface of the lower plate 4. At this time Keep the needleless stirring head 1 in contact with the upper surface of the cylindrical boss in the upper plate 3;

Step 3: Drive the external auxiliary stationary shaft shoulder 2 to move downward until it contacts the upper plate 3;

Step 4: Start the ultrasonic system to preheat the material to be connected for 5s to 30min, the ultrasonic vibration power is 60-2000W, and the amplitude is 15-55μm; in this embodiment, the material to be connected is preheated for 5s, the ultrasonic vibration power is 2000W, and the amplitude is 15μm;

Step 5: After the preheating, drive the needleless stirring head 1 to rotate at a speed of 50-8000rpm, and tie at a speed of 0.1-10mm/min, and the lowering amount is 2.8mm. Stay for 1 to 120s; in this embodiment, the rotation speed of the needleless stirring head 1 is 800rpm, the lowering speed is 1mm/min, and it stays for 1s after reaching the lowering amount;

Step 6: After the welding is completed, move the needleless stirring head 1 and the external auxiliary stationary shaft shoulder 2 up, turn off the ultrasonic system, and remove the test piece after cooling to room temperature.

Example 2

In this example, the present invention is used to connect the glass fiber reinforced PEI composite material and the titanium alloy. The height of the cylindrical boss on the surface of the glass fiber reinforced PEI composite material is 5 mm and the radius is 18 mm; the diameter of the needleless stirring head 1 is larger than the diameter of the boss on the surface of the composite material. 2mm; the radii of the upper bottom and the lower bottom of the circular truncated hole 6 opened on the surface of the 2024 aluminum alloy are 3mm and 5mm respectively, and the external auxiliary static shoulder 2, the needleless stirring head 1 and the ultrasonic amplitude rod 5 used in the welding are separated by different systems. The specific steps of driving and connecting are as follows:

Step 1: A cylindrical boss is prefabricated on the surface of the glass fiber reinforced PEI composite material, and a circular truncated hole 6 with a thread 7 on the inner wall is opened on the upper surface of the 2024 aluminum alloy;

Step 2: Put the parts to be connected on the workbench, the glass fiber reinforced PEI composite material is used as the upper plate 3, the 2024 aluminum alloy is used as the lower plate 4, and the clamps are used for fixing and the ultrasonic horn 5 is placed on the bottom surface of the lower plate 4. At this time Keep the needleless stirring head 11 in contact with the upper surface of the cylindrical boss in the upper plate 3;

Step 3: Drive the external auxiliary stationary shaft shoulder 2 to move downward until it contacts the upper plate 3;

Step 4: Start the ultrasonic system to preheat the material to be connected for 5s to 30min, the ultrasonic vibration power is 60-2000W, and the amplitude is 15-55μm; in this embodiment, the material to be connected is preheated for 30min, the ultrasonic vibration power is 100W, and the amplitude is 55μm;

Step 5: After the preheating, drive the needleless stirring head 1 to rotate at a speed of 50-8000rpm, and tie at a speed of 0.1-10mm/min, and the lowering amount is 4.5mm. Stay for 1 to 120s; in this embodiment, the rotation speed of the needleless stirring head 1 is 2000rpm, the lowering speed is 10mm/min, and it stays for 120s after reaching the lowering amount;

Step 6: After the welding is completed, move the needleless stirring head 1 and the external auxiliary stationary shaft shoulder 2 up, turn off the ultrasonic system, and remove the test piece after cooling to room temperature.

Claims (7)

1. A point connection method for long fiber reinforced thermoplastic composite material and dissimilar material is characterized in that: the method specifically comprises the following steps:

the method comprises the following steps: a cylindrical boss is prefabricated on the surface of the long fiber reinforced thermoplastic composite material, and a circular truncated cone-shaped hole with threads on the inner wall is formed on the upper surface of a dissimilar material connected with the long fiber reinforced thermoplastic composite material;

step two: placing a part to be connected on a workbench, taking the long fiber reinforced thermoplastic composite material as an upper plate, taking a dissimilar material connected with the long fiber reinforced thermoplastic composite material as a lower plate, fixing by using a clamp, placing an ultrasonic amplitude transformer on the bottom surface of the lower plate, and keeping the needleless stirring head in contact with the upper surface of a cylindrical boss in the upper plate;

step three: driving the external auxiliary stationary shoulder to move downward until contacting the upper plate;

step four: an ultrasonic system is started to preheat a material to be connected for 5s to 30min, the ultrasonic vibration power is 60-2000W, and the amplitude is 15-55 mu m;

step five: after the preheating is finished, driving the needleless stirring head to rotate at the speed of 50-8000 rpm, and downwards rolling at the speed of 0.1-10 mm/min, wherein the downwards rolling amount is not more than the height of the cylindrical boss, and only keeping the rotational motion and staying for 1-120 s for welding after reaching the downwards rolling amount;

step six: after the welding is finished, the pin-free stirring head and the external auxiliary static shaft shoulder are moved upwards, the ultrasonic system is closed, and the test piece is taken down after being cooled to the room temperature.

2. The method of claim 1 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the diameter of the needleless stirring head is 1-50 mm larger than that of the boss, and the height of the cylindrical boss is 0.5-20 mm.

3. The method of claim 1 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the diameter of the upper bottom of the circular truncated cone-shaped hole in the first step is 5-70% of the diameter of the pin-free stirring head, the diameter of the lower bottom of the circular truncated cone-shaped hole is 5-80% of the diameter of the pin-free stirring head, and the area of the upper bottom of the circular truncated cone-shaped hole is smaller than that of the lower bottom of the circular truncated cone-shaped hole, so that the bending resistance of the connector is.

4. The method of claim 3 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the circular truncated cone-shaped holes are uniformly distributed in the spot welding area so as to improve the torsion resistance of the joint, and the specific number is designed according to the requirement.

5. The method of claim 1 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the volume of the prefabricated cylindrical boss is larger than the total volume of the lower plate multi-cone-shaped hole, so that the lower plate multi-cone-shaped hole can be fully filled, and meanwhile, a welding joint with high surface quality is obtained.

6. The method of claim 1 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the lower plate material may be a metal, ceramic, thermoplastic polymer, thermosetting polymer, or wood material.

7. The method of claim 1 for point joining of long fiber reinforced thermoplastic composite materials to dissimilar materials, wherein: the method can also be used for connecting short fiber reinforced thermoplastic composite materials, particle reinforced thermoplastic composite materials, thermoplastic polymer materials and dissimilar materials.

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