CN113681159B - A metal and thermoplastic composite material laser pressure welding device, method and application thereof - Google Patents

Abstract

The invention relates to the technical field of laser connection of metal and non-metal composite materials, in particular to a laser pressure welding device for metal and thermoplastic composite materials, and a method and application thereof. In order to solve the problems in the prior art that the existing process of laser pressure welding of fiber-reinforced thermoplastic composite materials and metals is difficult to control, the process is cumbersome, and the quality of the joints is poor, the present invention provides a laser pressure welding device for metal and thermoplastic composite materials, and a method and application thereof. Setting the laser to be coaxial with the spherical indenter can ensure pressure with welding. First, from the perspective that pressure affects fluidity, the molten layer can be accelerated to flow into the micro-texture gap on the metal surface within the original welding time; second, from the perspective that pressure affects interface heat conduction , the increase of the contact pressure can improve the interfacial heat transfer, promote the melting of the CFRP matrix in a shorter time, and increase the time for the molten layer to remain in a molten state to a certain extent, which is beneficial to eliminate the interfacial voids.

Description

A metal and thermoplastic composite material laser pressure welding device, method and application thereof

technical field

The invention relates to the technical field of laser connection of metal and non-metal composite materials, in particular to a laser pressure welding device for metal and thermoplastic composite materials, a method and application thereof.

Background technique

The urgent need for automotive lightweighting has prompted further applications of lapped composite structures of metal and thermoplastic composites. The use of carbon fiber reinforced thermoplastic polymer matrix composites (hereinafter referred to as CFRP) with high specific strength and high specific stiffness to replace the traditional single metal structure can greatly reduce the body weight and energy consumption. At present, the laser thermal conduction welding process has developed into one of the advanced joining technologies of metals and thermoplastic composites, which has attracted much attention from domestic and foreign researchers.

Due to the huge difference in physical and chemical properties of metals and CFRP, it is difficult to form a high-strength interfacial bond between them. Strengthening the mechanical anchoring effect through the laser surface microtexturing technology to improve the joint strength is currently the main measure to strengthen the metal and CRRP laser thermal conduction welded joints. The principle is to use laser ablation to prefabricate a micro-texture with a certain depth and shape on the metal surface. During the welding process, the molten layer of the CFRP matrix flows into the micro-texture, forming a mechanical occlusion with it, while increasing the contact area between the two. , to achieve the purpose of improving the joint strength.

However, the inventors found that because the viscosity of the CFRP matrix resin after melting directly affects the fluidity of the molten layer, when the prefabricated microtexture depth by laser ablation is too large or the laser parameters are unreasonable, it is very easy to cause a molten layer. The inability to fill the microtexture during the welding time results in residual air gaps at the interface after welding, which in turn reduces joint strength. Therefore, the strengthening effect of strengthening the anchoring effect by forming microtextures on the metal surface by laser ablation is closely related to the flow filling ability of the molten layer of the CFRP matrix. When the laser heat input is increased to improve the heat conduction (the lap laser heat conduction welding joint mostly uses the laser to directly heat the metal, and then the heat is transferred to the CFRP composite material in the form of heat conduction), although the increase of the interface temperature can promote the fluidity and improve the above problems, but High heat input inevitably increases residual stress, deformation and cracking of CFRP matrix after welding, and the welding process is not easy to control; secondly, optimizing the shape of the prefabricated microtexture on the metal surface can also avoid the above problems, but it increases the complexity of the process and limits the application of this enhancement.

In addition, the inventor also found that although the prior art discloses some methods of laser pressure welding of fiber-reinforced thermoplastic composite materials and metals, it is necessary to apply pressure before and after welding, supplemented by ultrasonic treatment, and slight changes in pressure and ultrasonic parameters can affect the The quality of the joint, the complex device and the high difficulty in operation.

SUMMARY OF THE INVENTION

In order to solve the problems in the prior art that the existing process of laser pressure welding of fiber-reinforced thermoplastic composite materials and metals is difficult to control, the process is cumbersome, and the quality of joints is poor, the present invention provides a laser pressure welding device for metal and thermoplastic composite materials, and a method and application thereof. Setting the laser to be coaxial with the spherical indenter can ensure the pressure with welding. First, from the perspective that the pressure affects the fluidity, the molten layer can be accelerated to flow into the micro-texture gap on the metal surface within the original welding time; secondly, from the perspective that the pressure affects the interface heat conduction , the increase of the contact pressure can improve the interfacial heat transfer, promote the melting of the CFRP matrix in a shorter time, and increase the time for the molten layer to remain in a molten state to a certain extent, which is beneficial to eliminate the interfacial voids.

Specifically, the present invention is achieved through the following technical solutions:

A first aspect of the present invention provides a metal and thermoplastic composite material laser pressure welding device, comprising: a support table, a laser and a spherical indenter, the support table is provided with a through groove, the spherical indenter is located in the through groove, and one end of the spherical indenter is connected to The movable connection of the ejector rod;

The support table is provided with a fixture, the fixture and the laser are located on the same side of the support table, the laser and the ejector are located on both sides of the support table, and the axes of the laser, the spherical indenter and the ejector are coincident.

A second aspect of the present invention provides a method for laser thermal conduction welding of metal and thermoplastic composite materials, comprising:

Place the metal and thermoplastic composite material on the through groove of the support table, the thermoplastic composite material is located between the metal and the support table, use a clamp to fix the metal, and adjust the position of the laser spot to ensure that the center of the spot and the center of the through groove of the support table are on the same axis. ;

Adjust the position of the ejector rod so that the axis of the spherical indenter is in the center of the through groove of the support table, and adjust the parameters of the starting pressure controller to the set value. The metal and thermoplastic composite materials located in the through groove are affected by the clamp and the spherical indenter extrusion;

Set the laser process parameters, set the moving speed of the support table to complete the welding movement process, and the moving speed is the welding speed;

Laser thermal conduction welding begins, the ejector rod maintains the same pressure, and the support table moves a certain distance to complete the lap welding. After cooling, the pressure is relieved, the tooling is removed, and the welding process is completed.

A third aspect of the present invention provides a composite material prepared by a method of laser thermal conduction welding of a metal and a thermoplastic composite material.

A fourth aspect of the present invention provides an application of a metal and thermoplastic composite material laser pressure welding device in the preparation of metal and non-metal matrix composite materials.

The above one or more technical solutions have the following beneficial effects:

1) Not affected by the size and depth of the micro-texture on the metal surface, even under low heat input, the process can still avoid the problem of post-weld air defects.

2) Using pressure with welding, firstly, from the point of view that the pressure affects the fluidity, the molten layer can be accelerated to flow into the micro-texture gap of the metal surface within the original welding time; secondly, from the point of view that the pressure affects the heat conduction of the interface, the increase of the contact pressure can improve the interface The heat transfer promotes the melting of the CFRP matrix in a shorter time, which increases the time for the molten layer to remain in a molten state to a certain extent, which is conducive to eliminating interfacial voids; finally, applying a pressure load during the welding process can promote the physical properties of the molten layer and the metal surface. Adhesion, promote the discharge of residual air, improve the interface stress state, and further enhance the bonding strength.

3) The process is simple, the operability is strong, the pressurizing device to be used is easy to prepare, and the pressurizing parameters are few, which is suitable for industrial production.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein:

1 is a schematic diagram of a welding pressurizing device for laser thermal conduction welding of metal and thermoplastic composite materials according to Embodiment 1 of the present invention;

Fig. 2 is the typical topography diagram of laser processing metal surface to form microtexture in Example 1 of the present invention;

Fig. 3 is the strengthening of the mechanical anchoring effect at the connection interface between the metal and the thermoplastic composite material with the welding pressure during the welding process of the embodiment 2 of the present invention;

Fig. 4 is in the welding process, the embodiment 2 of the present invention eliminates the void defect under the original conventional process with welding pressure;

Among them: 1. Metal, 2. Thermoplastic composite material, 3. Support table, 4. Fixture, 5. Laser, 6. Spherical indenter, 7. Ejector.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In the following examples, the experimental methods without specific conditions are usually in accordance with conventional conditions or in accordance with the conditions suggested by the manufacturer.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

It should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that The device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention.

The inventor found that for the laser joining technology of metal and non-metal composite materials, although the increase of the interface temperature can promote the fluidity and improve the air gap or strength problem at the joint, the high heat input inevitably increases the residual stress, deformation and CFRP after welding. The cracking of the matrix, and the welding process is not easy to control; secondly, optimizing the shape of the prefabricated microtexture on the metal surface can also avoid the above problems, but it increases the complexity of the process and limits the application of this strengthening measure.

In addition, the inventor also found that although the prior art discloses some methods of laser pressure welding of fiber-reinforced thermoplastic composite materials and metals, it is necessary to apply pressure before and after welding, supplemented by ultrasonic treatment, and slight changes in pressure and ultrasonic parameters can affect the The quality of the joint, the complex device and the high difficulty in operation.

Therefore, the present invention proposes a metal and thermoplastic composite material laser pressure welding device and its method and application to solve these problems. Specifically, the present invention is achieved through the following technical solutions:

A first aspect of the present invention provides a metal and thermoplastic composite material laser pressure welding device, comprising: a support table, a laser and a spherical indenter, the support table is provided with a through groove, the spherical indenter is located in the through groove, and one end of the spherical indenter is connected to The movable connection of the ejector rod;

The support table is provided with a fixture, the fixture and the laser are located on the same side of the support table, the laser and the ejector are located on both sides of the support table, and the axes of the laser, the spherical indenter and the ejector are coincident.

Some techniques apply pressure before and after laser welding, which is equivalent to applying pressure and laser heating and melting separately. Therefore, ultrasonic vibration-assisted treatment is required to ensure that the molten composite material fully fills the metal microstructure area under the combined effect of these forces. These methods are suitable for the pressure welding process in which the metal microstructure is raised, and the size of the protrusions is in the order of millimeters, so the size of the protrusions is large, so it is necessary to control the pressure and vibration parameters to regulate the flow of the molten composite material.

However, this application found that if during the laser heating and melting process, the center of the laser spot and the center of the spherical indenter on the other side of the through groove of the support table are on the same axis, the simultaneous pressure and welding can be realized, which can not only reduce the number of indenters, but also eliminate the need for The filling of metal microstructures with molten liquid can also be achieved by using an ultrasonic vibration device, killing two birds with one stone.

In order to increase the clamping stability and avoid the deformation of the non-metallic material during the melting process, in one or more embodiments of the present invention, there are two clamps located on both sides of the through groove.

In one or more embodiments of the present invention, the ejector rod provides pressure to the spherical indenter through a pneumatic pressure device;

Preferably, the pressure can be adjusted in a range of 200-2000N.

Further, the loading force at the bottom of the ejector rod with the rotatable spherical pressure head is realized by the pneumatic pressure device, and the pressure can be adjusted in the range of 200-2000N.

Place the fixture on the support table. The support table has a rectangular through groove that matches the size of the indenter along the direction of the slide rail. The support table is made of steel with good stability. The width of the through groove is 12mm, and the diameter of the spherical indenter is 12mm. It is 8mm, and there will be no mechanical collision between the ejector rod and the side of the through groove of the support table.

In one or more embodiments of the present invention, the apparatus further includes a metal and thermoplastic composite material, the thermoplastic composite material being located between the metal and the support table. The metal surface is provided with a micro-texture, and the micro-texture is composed of a groove array structure with a spacing of 80-200 μm and a depth of 200-450 μm.

The side of the metal surface provided with the microtexture is in contact with the thermoplastic composite. Compared with metals with raised microstructures on the surface, in some embodiments of the present invention, the metal surface microstructures are grooves, so laser heating and pressure can be used simultaneously, and ultrasonic vibration treatment can be used to make the fusion composite. Material fills the grooves.

In addition, some metal protrusions in the prior art are micron-sized, while in some embodiments of the present invention, the grooves are micron-sized. Experiments have found that for micron-sized grooves, simultaneous laser heating and pressure can better fill the grooves. This is also the solution and effect that the prior art has not revealed.

Preferably, the groove shape is a conical, cylindrical, spherical or wedge-shaped groove shape;

Preferably, the metal is selected from at least one of titanium alloy, stainless steel, aluminum alloy, and magnesium alloy, and the metal thickness is 1-5 mm;

In one or more embodiments of the present invention, the thermoplastic composite material is selected from at least one of short-range or continuous carbon fiber reinforced polyetheretherketone, polyphenylene sulfide or nylon 6, and the thickness of the reinforced thermoplastic composite material is 2 -5mm.

The thickness of the metal or thermoplastic composite material is millimeter level, and the metal groove is micrometer level. With laser heating and pressure, it can not only ensure that the thermoplastic composite material is completely immersed in the groove, but also avoid setting up multiple structures and increase the operation. difficulty.

A second aspect of the present invention provides a method for laser thermal conduction welding of metal and thermoplastic composite materials, comprising:

Place the metal and thermoplastic composite material on the through groove of the support table, the thermoplastic composite material is located between the metal and the support table, use a clamp to fix the metal, and adjust the position of the laser spot to ensure that the center of the spot and the center of the through groove of the support table are on the same axis. ;

Adjust the position of the ejector rod so that the axis of the spherical indenter is in the center of the through groove of the support table, and adjust the parameters of the starting pressure controller to the set value. The metal and thermoplastic composite materials located in the through groove are affected by the clamp and the spherical indenter extrusion;

Set the laser process parameters, set the moving speed of the support table to complete the welding movement process, and the moving speed is the welding speed;

Laser thermal conduction welding begins, the ejector rod maintains the same pressure, and the support table moves a certain distance to complete the lap welding. After cooling, the pressure is relieved, the tooling is removed, and the welding process is completed.

In one or more embodiments of the present invention, the movement of the support table is completed by an electrically driven guide rail, and the moving speed range is large, and no special design is required.

Preferably, the laser process parameters are: the laser power is 20-500W, the laser frequency is 30-1000Hz, the pulse width is 10-500ns, the wavelength is 800-1100nm, and the beam scanning speed is 100-5000mm/s;

The pressurized ejector always maintains a stable value during the laser heating process. By increasing the normal pressure in the center of the melting zone, the molten thermoplastic composite matrix is accelerated to flow and the microstructure of the filling metal surface is accelerated, so as to promote the fusion of the metal and the thermoplastic composite. The interface forms a void-free interlocking structure, eliminating void defects and achieving high-strength connection and extended service life of the joint. And after the laser heating or lap welding is completed, the pressure is maintained for 10-20s to stabilize the interface between the metal and the carbon fiber reinforced composite material.

A third aspect of the present invention provides a composite material prepared by a method of laser thermal conduction welding of a metal and a thermoplastic composite material.

A fourth aspect of the present invention provides an application of a metal and thermoplastic composite material laser pressure welding device in the preparation of metal and non-metal matrix composite materials.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are intended to explain rather than limit the present invention.

Example 1

As shown in FIG. 1, a metal and thermoplastic composite material laser pressure welding device disclosed in this embodiment includes: a support table 3, a laser 5 and a spherical indenter 6, the support table 3 is provided with a rectangular through groove, and the support table 3 The thermoplastic composite material 2 and the metal 1 are placed on the top in turn. The side of the metal 1 in contact with the thermoplastic composite material 2 is provided with a micro-texture. The micro-texture is composed of a groove array structure with a spacing of 120 μm and a depth of 300 μm, as shown in Figure 2 Show.

The metal 1 is 304 stainless steel with a thickness of 2 mm, and the thermoplastic composite material 2 is a short-range discontinuous carbon fiber reinforced nylon six (CF-PA6) with a thickness of 2 mm.

The spherical indenter 6 is located in the through groove, one end of the spherical indenter 6 is movably connected with the ejector rod 7, and the ejector rod 7 provides pressure for the spherical indenter 6 through a pneumatic pressure device. The width of the through groove is 12 mm, the diameter of the spherical indenter 6 is 8 mm, and there will be no mechanical collision between the ejector rod 7 and the side surface of the through groove of the support table 3 . Under the action of the ejector rod 7 , the spherical indenter 6 can reciprocate in the through groove while exerting pressure on the thermoplastic composite material 2 .

The support table 3 is provided with two clamps 4, the clamps 4 and the laser 5 are located above the support table 3, the ejector pin 7 is located below the support table 3, and the axes of the laser 5, the spherical indenter 6 and the ejector pin 7 are coincident.

The thermoplastic composite material 2 and the metal 1 are extruded under the action of the clamp 4 , the spherical indenter 6 and the ejector pin 7 .

Example 2

This embodiment discloses a method for laser thermal conduction welding of metal and thermoplastic composite materials, which is performed by using the device of claim 1 .

In step 1, the metal surface is cleaned with alcohol, and then the micro-texture of the to-be-welded area of the metal surface is prepared by laser processing technology. The metal and CFRP plates are superimposed and fixed on a sliding support table, the metal is on the upper layer of the overlapping structure, and the upper surface is fixed and pressed with a clamp to prevent rigid sliding.

Step 2, contact the spherical indenter on the ejector rod with the bottom of the CFRP plate through the rectangular through groove on the support table, set the loading pressure of the pneumatic pressure controller to 1000N, keep it vertically fixed, and maintain the pressure value within the welding process. Change. Adjust the position of the laser transmitter and fix it vertically, keeping it on the same axis as the center of the bottom spherical indenter (ball indenter) (as shown in Figure 1).

Step 3, set the laser process parameters, the laser wavelength is 1000nm, the laser pulse width is 15ps, the laser power is 16W, and the beam scanning speed is 1m/s. The metal surface is heated by laser, and the upper surface of CFRP is melted by heat conduction, and the melted layer is pushed by the pressure on the back of CFRP to reinforce the mechanical anchoring effect of the connection interface (as shown in Figure 3).

The metal material used in this embodiment is 304 stainless steel with a thickness of 2 mm, and the thermoplastic composite material is short-range discontinuous carbon fiber reinforced nylon six (CF-PA6) with a thickness of 2 mm. A picosecond laser is used for the processing of the metal surface microstructure, and the microstructure processed on the metal surface is a tapered groove structure with a spacing of 120 μm and a depth of 300 μm.

In order to reduce the contact friction between the ball indenter and the CFRP sheet, the surface of the indenter is coated with lubricant.

In this embodiment, the air in the deep tapered groove structure is eliminated by welding pressure to form a dense metal surface and the CFRP matrix interlocking structure is shown in Figure 4. The white arrow represents the direction of fluid flow, and the length of the arrow represents the flow capacity. After the welding is pressurized, the fluidity is improved, and the flow rate is accelerated, and the intensity is increased. Due to the gradient distribution of the pressure from the center to the edge, the center is the highest, and the air displaced by filling the groove is easier to be connected to the bonding area.

The conventional processing method is as follows: place the CFRP composite plate on the backing plate, place a metal plate on the upper side, and directly press the metal upper surface on both sides of the area to be welded with a clamp to restrain rigid sliding. In order to avoid trapping air pores in the groove, it is necessary to carefully select the laser parameters to adjust the heat input, and appropriately increase the welding time and increase the pressure constraints of the clamps on both sides of the upper metal surface.

The difference from this embodiment in the elimination principle is that: selecting the appropriate heat input is to ensure that the molten layer of the CFRP composite material has a certain fluidity, and increasing the welding time is to ensure that the flowing viscous matrix material can be filled more thoroughly Grooved microstructure. However, the conventional treatment method cannot exert the promoting effect of the external driving force on the fluidity of the molten fluid, nor can it exert the effect of improving the interfacial contact heat transfer characteristics under high pressure and thereby shortening the melting time of the CFRP composite material; , which can take into account the above two promotion effects, and simply and efficiently eliminate the process problem of remaining voids in the deep groove microstructure.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still understand the foregoing embodiments. The technical solutions described are modified, or some technical features thereof are equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (12)

1. A laser thermal conductivity welding method for metal and thermoplastic composite materials is realized by adopting a laser pressure welding device for the metal and thermoplastic composite materials, and the device comprises the following steps: the device comprises a supporting table, a laser and a spherical pressure head, wherein the supporting table is provided with a through groove, the spherical pressure head is positioned in the through groove, and one end of the spherical pressure head is movably connected with an ejector rod;

the supporting table is provided with a clamp, the clamp and the laser are positioned on the same side of the supporting table, the laser and the ejector rod are positioned on two sides of the supporting table, and the laser, the spherical pressure head and the ejector rod are in axial coincidence;

the support platform comprises a metal and a thermoplastic composite material, wherein the thermoplastic composite material is positioned between the metal and the support platform;

the metal surface is provided with a micro-texture, and the micro-texture is composed of a groove array structure;

the method is characterized by comprising the following steps:

placing metal and thermoplastic composite material on the through groove of the support table, wherein the thermoplastic composite material is positioned between the metal and the support table, fixing the metal by adopting a clamp, adjusting the position of a laser spot, and ensuring that the center of the spot and the center of the through groove of the support table are on the same axis;

adjusting the position of the ejector rod to enable the axis of the spherical pressure head to be positioned at the central position of the through groove of the support platform, adjusting the parameters of the starting pressure controller to a set value, and extruding the metal and the thermoplastic composite material positioned in the through groove under the action of the clamp and the spherical pressure head;

setting laser process parameters, and setting the moving speed of the support table to complete the welding moving process, wherein the moving speed is the welding speed;

starting laser thermal conduction welding, maintaining the pressure of the ejector rod unchanged, completing lap welding after the supporting table moves for a certain distance, waiting for cooling, releasing pressure, disassembling the tool and completing the welding process.

2. A laser thermal conductivity welding method for metal and thermoplastic composite material according to claim 1, wherein there are two clamps located at two sides of the through groove.

3. The laser thermal conductivity welding method for metal and thermoplastic composite material according to claim 1, wherein the ram provides pressure to the spherical indenter by a pneumatic pressing device.

4. The laser thermal conductivity welding method for metal and thermoplastic composite material as claimed in claim 3, wherein the adjustable range of the pressure is 200-2000N.

5. The laser thermal conductivity welding method for metal and thermoplastic composite material as claimed in claim 1, wherein the pitch of the microtextured groove array is 80-200 μm, and the depth is 200-450 μm.

6. A laser thermal conductivity welding method for metal and thermoplastic composite material according to claim 1, wherein the shape of the groove is a conical, cylindrical, ball head or wedge groove shape.

7. A laser thermal conductivity welding method for metal and thermoplastic composite material according to claim 1, wherein the metal is at least one selected from titanium alloy, stainless steel, aluminum alloy, magnesium alloy, and the metal thickness is 1-5 mm.

8. The laser thermal conductivity welding method for metal and thermoplastic composite material as claimed in claim 1, wherein the thermoplastic composite material is selected from at least one of polyether ether ketone, polyphenylene sulfide or nylon six reinforced by short distance or continuous carbon fiber, and the thickness of the reinforced thermoplastic composite material plate is 2-5 mm.

9. The laser thermal conductivity welding method of metal and thermoplastic composite material as claimed in claim 1, wherein the movement of the support table is performed by a motor driving a guide rail.

10. The laser thermal conductivity welding method for metal and thermoplastic composite material of claim 1, wherein the laser process parameters are as follows: the laser power is 20-500W, the laser frequency is 30-1000Hz, the pulse width is 10-500ns, the wavelength is 800-1100nm, and the beam scanning speed is 100-5000 mm/s.

11. The laser thermal conduction welding method for metal and thermoplastic composite material according to claim 1, wherein after the lap welding is completed, the pressure is kept for 10-20s, and the pressure is released by cooling.

12. Use of a laser thermal conductivity welding method of metal and thermoplastic composites according to any of claims 1 to 11 for the preparation of metal and non-metal based composites.

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