Flow drilling hot melting screw joint process of thermoplastic composite material and light alloy

Abstract

The invention discloses a flow drilling hot melting screw joint process of a thermoplastic composite material and a light alloy, which specifically comprises the following steps of: overlapping a thermoplastic composite material plate and a light alloy plate in a form that the thermoplastic composite material plate is arranged on the upper part and the light alloy plate is arranged on the lower part, and then fixing; a flow drilling self-tapping screw is used as a connecting medium, flow drilling equipment is used for carrying out flow drilling hot melting screw joint, the rotating speed of the flow drilling stage is 6000-8000 r / min, the downward pressure is 0.4-0.8 kN, and the process time of the flow drilling stage is 5-20 s. According to the flow drilling hot melting screw joint process of the thermoplastic composite material and the light alloy, the thermal effect of the flow drilling self-tapping screw in the connecting process is used for enhancing the material flow of the thermoplastic composite material and the light alloy to form a melting layer effect at a material lamination interface; the reinforced composite connection effect of mechanical connection and welding of the composite material / light alloy is achieved, the applicability is high, operation is easy, the sealing performance is good, the connection firmness is good, and the application prospect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoplastic composite materials and light alloy dissimilar material connection, and particularly to a flow drilling hot melt screw connection process for thermoplastic composite materials and light alloys, and particularly to a method for realizing composite reinforced connection of thermoplastic composite materials and light alloy materials by using the flow drilling hot melt screw connection process. Background Art

[0002] Composite materials and lightweight alloys are key materials for lightweight manufacturing in the aerospace industry. Composite material / light alloy heterogeneous structures can meet the dual technical indicators of structural performance requirements and lightweight design. In addition, the application of heterogeneous materials has also promoted the development of material science and process technology, providing more advanced and reliable solutions for the aerospace field.

[0003] At present, there are three main ways to connect composite materials and light alloys: mechanical connection, adhesive connection and fusion welding. Mechanical connection usually requires the introduction of fasteners and prefabricated holes on the parts, resulting in stress concentration at the connection. Although the adhesive process is relatively mature, its process cycle is long, and the joints are not good at impact resistance, fatigue resistance, moisture resistance and other performance. Due to objective factors such as the difference in melting point and thermal expansion coefficient between metal and non-metal materials, fusion welding is difficult to form a high-quality connection interface, and the welded structure is prone to failure during the service stage.

[0004] Composite materials and metal materials have different physical and chemical properties, such as thermal expansion coefficient, thermal conductivity, etc. This mismatch leads to increased thermal stress and thermal strain at the connection interface. In addition, due to the complex and uneven structure of the composite material and the limited connection contact area, it is difficult to achieve a strong connection.

[0005] Therefore, it is of great practical significance to develop a method for connecting composite materials and lightweight alloys with high strength and good stability of the connecting interface. Summary of the invention

[0006] Due to the above-mentioned defects in the prior art, the present invention provides a method for connecting a composite material and a light alloy with a high strength and good stability of the connection interface, specifically a flow drill hot melt screw connection process for thermoplastic composite materials and light alloys, which utilizes the rotational friction of the flow drill screw to obtain a solid phase welding effect, while retaining the threaded connection characteristics of traditional flow drill self-tapping screws, to achieve a composite reinforced connection form of mechanical connection + welding of thermoplastic composite materials and light alloys, improve the strength of the connection and the sealing of the plate connection, ensure the stability and durability of the connection, and overcome the problems of poor strength and poor stability of the connection interface of the existing composite material and metal material connection methods.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A flow drilling hot-melt screw connection process for thermoplastic composite materials and light alloys, wherein a thermoplastic composite plate and a light alloy plate are overlapped and fixed in the form of the thermoplastic composite plate on top and the light alloy plate on the bottom, and flow drilling hot-melt screw connection is performed using a flow drilling device with flow drilling self-tapping screws as a connecting medium, the rotation speed of the flow drilling hole drilling stage is 6000-8000 r / min, the downward pressure is 0.4-0.8 kN, and the process time of the flow drilling hole drilling stage is 5-20 s.

[0009] By adjusting the process parameters of the flow drilling stage, increasing the process time of the flow drilling stage, increasing the heat generation, and applying the screw speed and down force from the beginning to the end of the connection process to continuously generate heat, the rotation and feeding movement of the screw enhance the fluidity of the molten thermoplastic composite material, enhance the thread forming quality and the laminate interface connection quality. The rotation speed, down force and flow drilling time have a key influence on the joint connection quality. Too slow rotation speed will lead to insufficient friction heat, incomplete fusion zone formation, and insufficient connection strength; while too fast rotation speed may cause material overheating, thread forming quality degradation and even joint strength reduction; too large down force is easy to cause material extrusion deformation or damage, while too small down force cannot form a stable connection, resulting in loose joints or failure; too long flow drilling time will lead to local overheating of the material and uneven fusion zone; too short time may affect the connection quality due to insufficient softening and flow of the material. Therefore, it is necessary to optimize the coordinated regulation of rotation speed, down force and flow drilling time to ensure thread forming quality and interface connection strength.

[0010] Compared with the existing hot-melt self-tapping screw connection process, the flow drill hot-melt screw connection process of the thermoplastic composite material and the light alloy of the present invention mainly melts the thermoplastic composite material through the heat generated by the flow drill, so that it serves as a welding medium, and then solidifies between the flow drill self-tapping screw, the thermoplastic composite material plate and the light alloy plate to form a form in which the thermoplastic composite material plate and the light alloy plate are fixed by solid-state welding and mechanical thread connection, and the bonding strength between the thermoplastic composite material plate and the light alloy plate is improved. The welded thermoplastic composite material can seal the perforation position of the flow drill self-tapping screw. Compared with the traditional process, it greatly improves the sealing performance and ensures the integrity of the joint, providing technical support for improving the high-quality and high-strength performance of dissimilar material connections, high-cycle fatigue resistance and sealing performance, meeting the needs of aerospace and military equipment for high-performance connections, and has great application prospects.

[0011] As the preferred technical solution:

[0012] In the above-mentioned flow drilling hot-melt screw connection process of a thermoplastic composite material and a light alloy, the thickness of the thermoplastic composite material plate is 1 to 3 mm; the thickness of the light alloy plate is 1 to 3 mm. If the thermoplastic composite material plate is too thick, the screw may not penetrate and the fusion zone may not be fully formed, while if it is too thin, it may be easily deformed or damaged under high temperature and high pressure, affecting the strength and stability of the joint; if the light alloy plate is too thick, it will increase the difficulty of processing and energy consumption, resulting in incomplete thread forming, while if it is too thin, it may be easily deformed or penetrated by the screw, destroying the sealing and strength of the joint.

[0013] In the flow drilling hot melt screw joining process of a thermoplastic composite material and a light alloy as described above, before overlapping the thermoplastic composite material plate and the light alloy plate, the surfaces of the thermoplastic composite material plate and the light alloy plate are cleaned to remove oil, dust, etc. to ensure good contact.

[0014] In the above-mentioned flow drilling hot-melt screwing process for thermoplastic composite material and light alloy, the fixing refers to fixing the overlapped thermoplastic composite material plate and the light alloy plate by using a clamp.

[0015] According to the above-mentioned flow drilling hot-melt screwing process for thermoplastic composite material and light alloy, after the flow drilling hot-melt screwing, the joint is cooled to realize the flow drilling hot-melt screwing of the thermoplastic composite material plate and the light alloy plate.

[0016] In the above-mentioned flow drilling hot-melt screw joining process for thermoplastic composite material and light alloy, the cooling time of the joint is not less than 1 minute.

[0017] In the above-mentioned flow drilling hot-melt screwing process for thermoplastic composite materials and light alloys, the matrix material of the thermoplastic composite material is polyphenylene sulfide (PPS) to enhance the connection quality of the thermoplastic composite material and the light alloy material and the bonding ability of the laminate interface material.

[0018] In the above-mentioned hot-melt screw connection process of a thermoplastic composite material and a light alloy, the thermoplastic composite material is a carbon fiber reinforced thermoplastic composite material or a glass fiber reinforced thermoplastic composite material. Of course, specific process parameter values ​​can be selected according to different properties and thicknesses of the materials to meet actual needs.

[0019] The above technical solution is only a feasible technical solution of the present invention, and the protection scope of the present invention is not limited thereto. Those skilled in the art can reasonably adjust the specific design according to actual needs.

[0020] The above invention has the following advantages or beneficial effects:

[0021] (1) The flow drilling hot melt screw connection process of the thermoplastic composite material and the light alloy of the present invention can realize the connection of the thermoplastic composite material and the light alloy material, and in particular can realize the overlapping stable connection of the thermoplastic composite material on the top and the light alloy on the bottom;

[0022] (2) The flow drilling hot melt screw connection process of the thermoplastic composite material and the light alloy of the present invention can improve the strength and reliability of the connection of dissimilar materials. The flow drilling hot melt screw connection method realizes a composite connection form of mechanical connection + solid welding of composite materials and metal materials through a combination of drilling and self-tapping threads, forming a tight connection between the plates, reducing the risk of loosening and falling off, and having good sealing and high connection strength;

[0023] (3) The flow drilling hot-melt screw connection process of the thermoplastic composite material and the light alloy of the present invention does not require prefabricated holes, additional connecting parts and complicated processes, can simplify the manufacturing process, reduce working hours and costs, has the advantages of being simple, fast and economical, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention and its features, appearance and advantages will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not drawn to scale, and emphasis is placed on illustrating the subject matter of the present invention.

[0025] Figure 1 It is a schematic diagram of flow drilling hot melt screw connection of the thermoplastic composite material and the light alloy of the present invention;

[0026] Figure 2 This is a schematic diagram of the strengthening effect of mechanical connection and welding on the lap interface bonding area during the downward pressure of the flow drill screw during the connection process;

[0027] Figure 3 Schematic diagram for comparing the connection interface strengthened composite material and aluminum alloy flow drill hot melt screw connection interface completed in Example 1 with the connection interface strengthened composite material and aluminum alloy hot melt self-drilling screw connection interface in Comparative Example 1 (left figure) and load-displacement curve comparison diagram of Example 1 and Comparative Example 1 (right figure). DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0029] Example 1

[0030] A flow drilling hot melt screw connection process for thermoplastic composite materials and light alloys comprises the following steps:

[0031] (1) Select 2mm thick 2A12 aluminum alloy and 2mm thick CF / PPS composite material (carbon fiber reinforced polyphenylene sulfide composite material), and the plate size is 100mm*40mm;

[0032] (2) Use alcohol to clean the interface between the CF / PPS composite material and the 2A12 aluminum alloy laminate;

[0033] (3) Stack the two together to form the overlap area, with the upper side being the CF / PPS plate and the lower side being the 2A12 aluminum alloy plate, and install them together in a steel support fixture to prevent rigid slip during the connection process;

[0034] (4) Place the flow drill screw in the flow drill equipment;

[0035] (5) The process equipment is placed above the overlapped part of the plate, and the flow drill screw speed is set to 8000rpm and the downward pressure is set to 0.4kN during the flow drill drilling stage; the screw speed is set to 3000rpm and the downward pressure is set to 0.25kN during the tapping stage; the torque during the tightening stage is set to 8Nm;

[0036] (6) The plates are connected by flow drilling hot melt screw connection process. Under the process parameters, the process time of the flow drilling stage is 15.05s and the heat generated is 4074.57J;

[0037] (7) After the connection is completed, the flow drill equipment is removed. After 2 minutes, the joint solidifies and cools down, and the sample is removed. The shear strength of the joint is tested and the shear strength reaches 7280N.

[0038] Comparative Example 1

[0039] A hot-melt self-drilling screw connection process for thermoplastic composite materials and light alloys comprises the following steps:

[0040] (1) Select 2mm thick 2A12 aluminum alloy and 2mm thick CF / PPS composite material (carbon fiber reinforced polyphenylene sulfide composite material), and the plate size is 100mm*40mm;

[0041] (2) Use alcohol to clean the interface between the CF / PPS composite material and the 2A12 aluminum alloy laminate;

[0042] (3) Stack the two together to form the overlap area, with the upper side being the CF / PPS plate and the lower side being the 2A12 aluminum alloy plate, and install them together in a steel support fixture to prevent rigid slip during the connection process;

[0043] (4) Place the flow drill screw in the flow drill equipment;

[0044] (5) The process equipment is placed above the overlapped part of the plate, and the flow drill screw speed is set to 8000rpm and the downward pressure is set to 0.8kN during the flow drill drilling stage; the screw speed is set to 3000rpm and the downward pressure is set to 0.25kN during the tapping stage; the torque during the tightening stage is set to 8Nm;

[0045] (6) The plates are connected by hot melt self-drilling screw connection process. The process time of the downstream drilling stage is 1.9s and the heat generation is 1989.96J;

[0046] (7) After the connection is completed, the flow drill equipment is removed. After 2 minutes, the joint solidifies and cools down, and the sample is removed. The shear strength of the joint is tested and the shear strength reaches 6020N.

[0047] The process of the present invention is used to perform flow drilling hot melt screw connection. Figure 1 As shown, the heat generated by the flow drill melts the thermoplastic composite material (such as Figure 1 The molten layer in the flow drill is used as a welding medium and then solidified between the flow drill self-tapping screw, the thermoplastic composite plate and the light alloy plate (such as Figure 1 The thermoplastic composite material plate and the light alloy plate are fixed by solid state welding and mechanical thread connection (partial enlarged figure as shown in the figure) Figure 2 as shown).

[0048] Comparison of the interface-strengthened composite material and the aluminum alloy flow-drilled hot-melt screwed interface completed in Example 1 and the interface-strengthened composite material and the aluminum alloy hot-melt self-drilling screwed interface completed in Comparative Example 1 Figure 3 As shown on the left, it can be seen from the figure that the sufficient heat input of the flow drilling hot melt screwing process can make the thermoplastic composite material fully soften and increase its fluidity and form a tight fusion with the plastically deformed aluminum alloy; while the hot melt self-tapping process has insufficient heat input, resulting in insufficient softening of the composite material and the aluminum alloy, causing the CF-PPS at the interface position to be unable to form a close contact with the surface of the 2A12 aluminum alloy, and continuous bubbles exist at the laminate interface, thereby forming a large area of ​​void defects. Comparison of the load-displacement curves of Example 1 and Comparative Example 1 Figure 3 As shown on the right, it can be seen from the figure that in the test of connecting thermoplastic composite materials and aluminum alloys by flow drilling hot melt screwing process, the maximum shear load of the joint is 7.28kN, and in the test of connecting thermoplastic composite materials and aluminum alloys by hot melt self-tapping process, the maximum shear load of the joint is only 6.02kN. The shear strength of the joint in Example 1 is much greater than the shear strength of the joint in Comparative Example 1 (21% higher), which confirms the superiority of the flow drilling hot melt screwing process in connecting thermoplastic composite materials and light alloys, and also confirms the enhancement effect of the presence of the weld layer on the connection quality.

[0049] Example 2

[0050] A flow drilling hot melt screw connection process for thermoplastic composite materials and light alloys comprises the following steps:

[0051] (1) Select 2 mm thick 6061-T6 aluminum alloy and 2 mm thick CF / PEEK composite material (carbon fiber reinforced polyetheretherketone composite material), and the plate size is 100 mm*40 mm;

[0052] (2) Use alcohol to clean the interface between the CF / PEEK composite material and the 6061 aluminum alloy laminate;

[0053] (3) Stack the two together to form a lap joint area, with the upper side being the CF / PEEK plate and the lower side being the 6061 aluminum alloy plate, and install them together in a steel support fixture to prevent rigid slip during the connection process;

[0054] (4) Place the flow drill screw in the flow drill equipment;

[0055] (5) The process equipment is placed above the overlapped part of the plate, and the flow drill screw speed is set to 7000rpm and the downward pressure is set to 0.5kN during the flow drill drilling stage; the screw speed is set to 3000rpm and the downward pressure is set to 0.25kN during the tapping stage; the torque during the tightening stage is set to 8Nm;

[0056] (6) The plates are connected by flow drilling hot melt screw connection process. Under this process parameter, the process time of the flow drilling stage is 13.32s and the heat generated is 3407.11J;

[0057] (7) After the connection is completed, the flow drill equipment is removed. After 2 minutes, the joint solidifies and cools down, and the sample is removed. The shear strength of the joint is tested and the shear strength reaches 6440N.

[0058] Example 3

[0059] A flow drilling hot melt screw connection process for thermoplastic composite materials and light alloys comprises the following steps:

[0060] (1) Select 3 mm thick AZ31B magnesium alloy and 2 mm thick CF / PPS composite material (carbon fiber reinforced polyphenylene sulfide composite material), and the plate size is 100 mm*40 mm;

[0061] (2) Use alcohol to clean the interface between the CF / PPS composite material and the AZ31B magnesium alloy laminate;

[0062] (3) Stack the two together to form a lap joint area, with the upper side being the CF / PPS plate and the lower side being the AZ31B magnesium alloy plate, and install them together in a steel support fixture to prevent rigid slip during the connection process;

[0063] (4) Place the flow drill screw in the flow drill equipment;

[0064] (5) The process equipment is placed above the overlapped part of the plate, and the flow drill screw speed is set to 8000rpm and the downward pressure is set to 0.5kN during the flow drill drilling stage; the screw speed is set to 3000rpm and the downward pressure is set to 0.25kN during the tapping stage; the torque during the tightening stage is set to 8Nm;

[0065] (6) The plates are connected by flow drilling hot melt screw connection process. Under the process parameters, the process time of the flow drilling stage is 11.86s and the heat generation is 3029.46J;

[0066] (7) After the connection is completed, the flow drill equipment is removed. After 2 minutes, the joint solidifies and cools down, and the sample is removed. The shear strength of the joint is tested and the shear strength reaches 6390N.

[0067] It has been verified that the flow drilling hot-melt screw connection process of the thermoplastic composite material and the light alloy of the present invention can realize the connection of the thermoplastic composite material and the light alloy material, especially can realize the stable overlapping connection of the thermoplastic composite material on the top and the light alloy on the bottom; it can improve the strength and reliability of the connection of dissimilar materials. The flow drilling hot-melt screw connection method realizes a composite connection form of mechanical connection + solid-state welding of the composite material and the metal material through a combination of drilling and self-tapping threads, forms a tight connection between the plates, reduces the risk of loosening and falling off, has good sealing and high connection strength; does not require prefabricated holes, does not require additional connecting parts and complex processes, can simplify the manufacturing process, reduce working hours and costs, has the advantages of simplicity, speed and economy, and has good application prospects.

[0068] Those skilled in the art should understand that those skilled in the art can implement variations by combining the prior art and the above embodiments, which will not be described in detail here. Such variations do not affect the essential content of the present invention, and will not be described in detail here.

[0069] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A flow drilling hot melt screwing process for thermoplastic composite materials and light alloys, characterized in that: The thermoplastic composite plate and the lightweight alloy plate are overlapped and fixed in the form of the thermoplastic composite plate on top and the lightweight alloy plate on the bottom, and flow drilling hot-melt screw connection is performed using flow drilling equipment with flow drilling self-tapping screws as the connecting medium. The rotation speed of the flow drilling stage is 6000~8000r / min, the downward pressure is 0.4~0.8kN, and the process time of the flow drilling stage is 5~20s.

2. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: The thickness of the thermoplastic composite material plate is 1-3 mm; the thickness of the light alloy plate is 1-3 mm.

3. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: Before overlapping the thermoplastic composite plate and the light alloy plate, the surfaces of the thermoplastic composite plate and the light alloy plate are cleaned.

4. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: The fixing refers to fixing the overlapped thermoplastic composite material plate and the light alloy plate by using a clamp.

5. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: After the flow drilling hot-melt screw connection, the flow drilling hot-melt screw connection of the thermoplastic composite material plate and the light alloy plate is achieved by waiting for the joint to cool down.

6. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 5 is characterized in that: The cooling time of the joint is not less than 1 minute.

7. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: The matrix material of the thermoplastic composite material is polyphenylene sulfide.

8. The flow drilling hot melt screwing process of thermoplastic composite material and light alloy according to claim 1 is characterized in that: The thermoplastic composite material is a carbon fiber reinforced thermoplastic composite material or a glass fiber reinforced thermoplastic composite material.

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