Thermoplastic resin-based composite material connecting method

Abstract

The invention provides a thermoplastic resin matrix composite material connecting method which comprises the following steps: paving a first connecting layer on one side of a first composite material plate, co-curing to form a first to-be-welded part, paving a second connecting layer on one side of a second composite material plate, and co-curing to form a second to-be-welded part; curing thermoplastic resin on the surface of the heating element to form a composite heating element; placing a composite heating element between the first connecting layer and the second connecting layer, heating the composite heating element to a preset welding temperature, and melting the first connecting layer and the second connecting layer; and the first to-be-welded piece and the second to-be-welded piece are pressurized so that the first connecting layer and the second connecting layer can be attached, and the composite material welding plate is obtained after cooling and solidification. When the method is adopted for welding, on the premise that connection is achieved, the situation that too high temperature is generated on a welding interface, so that pores and layering are generated in a welding base material is avoided, and then the strength of a composite material connector is improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite material connection, and more particularly to a method for connecting thermoplastic resin-based composite materials. Background Art

[0002] Resistance welding has the characteristics of short process flow, simple and flexible equipment, and low cost. It is an efficient and high-quality welding technology for thermoplastic composite materials and has broad application prospects. The principle of resistance welding technology is: placing a heating element between thermoplastic composite laminates, heating the surface to be welded to a molten state through the principle of resistance heat generation, and forming a welded joint through pressurized cooling and consolidation.

[0003] The temperature of the welding interface in the resistance welding process is a key factor affecting the quality of the welded joint. In the existing technology, the welding interface temperature is generally too high during the welding process, resulting in pores and delamination inside the laminate, affecting the material strength inside the composite material. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The technical problem to be solved by the present invention is that when the existing thermoplastic resin-based composite materials are connected by resistance welding technology, the temperature at the welding interface is too high, resulting in pores and delamination inside the laminate.

[0006] (II) Technical solution

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for connecting thermoplastic resin-based composite materials, comprising the following steps:

[0009] A first connecting layer is laid on one side of the first composite material plate, and co-cured to form a first workpiece to be welded; a second connecting layer is laid on one side of the second composite material plate, and co-cured to form a second workpiece to be welded; wherein the first connecting layer and the second connecting layer are both connecting materials containing thermoplastic resin, and the first melting point of the connecting material is lower than the second melting point of the first composite material plate, and lower than the third melting point of the second composite material plate;

[0010] Curing and connecting the thermoplastic resin on the surface of the heating element to form a composite heating element;

[0011] The composite heating element is placed between the first connecting layer and the second connecting layer, and the composite heating element is heated to a preset welding temperature to melt the first connecting layer and the second connecting layer;

[0012] The first workpiece to be welded and the second workpiece to be welded are pressurized to make the first connecting layer fit with the second connecting layer, and then cooled and consolidated to obtain a composite material welded plate.

[0013] Preferably, the preset welding temperature is higher than the first melting point, and lower than the second melting point and the third melting point.

[0014] Preferably, the first connecting layer is a resin film or a resin-based fabric prepreg containing a fabric reinforcement;

[0015] And / or, the second connecting layer is a resin film or a resin-based fabric prepreg containing a fabric reinforcement.

[0016] Preferably, the material of the fabric reinforcement includes carbon fiber and glass fiber, and the form of the fabric reinforcement includes plain weave, twill, satin and spread fabric.

[0017] Preferably, the surface weight of the fabric reinforcement is in the range of 50 to 400 g / m 2 .

[0018] Preferably, the melting point of the connecting material is at least 30°C lower than the melting point of the first composite sheet, and the melting point of the connecting material is at least 30°C lower than the melting point of the second composite sheet.

[0019] Preferably, the thermoplastic resin includes polyaryletherketone, polyetheretherketone, polyetherketoneketone, polyetherimide, polyphenylene sulfide, nylon, polyethylene and polypropylene.

[0020] Preferably, during the co-curing process, the hot pressing temperature ranges from 200 to 400° C., the molding pressure ranges from 1.0 to 3.0 MPa, and the hot pressing time is from 30 to 60 min.

[0021] Preferably, the material of the heating element includes carbon fiber and metal.

[0022] Preferably, the first connection layer comprises at least one layer of prepreg of a connection material; and / or the second connection layer comprises at least one layer of prepreg of a connection material.

[0023] (III) Beneficial effects

[0024] The above technical solution of the present invention has at least the following advantages:

[0025] In the present invention, a first connection layer is laid on one side of a first composite material plate, and a second connection layer is laid on one side of a second composite material plate. The first connection layer and the second connection layer are heated by a composite heating element to melt them, and then pressurized to connect the first connection layer with the second connection layer, thereby realizing the connection between the first composite material plate and the second composite material plate. The first connection layer and the second connection layer are both connection materials containing thermoplastic resin. Since the first melting point of the connection material is lower than the second melting point of the first composite material plate, and lower than the third melting point of the second composite material plate, during the welding process, the temperature of the welding interface can be controlled to be higher than the first melting point and lower than the second melting point and the third melting point. Therefore, during welding, the temperature of the welding interface will not reach the melting point of the first composite material plate and the second composite material plate, thereby avoiding the generation of pores and stratification inside the first composite material plate and the second composite material plate due to excessively high welding temperature; in addition, the composite heating element is arranged between the first connecting layer and the second connecting layer, and the first connecting layer isolates the first composite material plate from the composite heating element, thereby avoiding the heat generated by the composite heating element from directly acting on the first composite material plate. At the same time, the second connecting layer isolates the second composite material plate from the composite heating element, thereby avoiding the heat generated by the composite heating element from directly acting on the second composite material plate, thereby further avoiding the generation of pores and stratification inside the first composite material plate and the second composite material plate due to excessively high welding temperature.

[0026] In the present invention, the surface of the heating element is solidified and connected with a thermoplastic resin, and the melting point of the thermoplastic resin is slightly higher than the melting point of the connecting material, and the resin forms a composite heating element. The thermoplastic resin is an insulating material, which wraps the heating element to prevent it from leaking electricity.

[0027] In the present invention, after the welding process is completed, the heating element is finally retained in the finally formed composite material welding plate. The heating element is preferably a conductive material with good compatibility with the resin material, such as carbon fiber. When it is implanted in the composite material welding plate, it can serve as a reinforcement of the resin-based material to further enhance the strength of the connection interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a schematic diagram of the implementation principle of the thermoplastic resin-based composite material connection method provided in an embodiment of the present invention.

[0030] The reference numerals in the figures are:

[0031] A. First workpiece to be welded; B. Second workpiece to be welded; 1. First composite material plate; 2. First connecting layer; 3. Second composite material plate; 4. Second connecting layer; 5. Composite heating element; 6. Wire; 7. Power supply; 8. Insulating pressure block. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly located on the other element or indirectly located on the other element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention, and do not indicate that a device or element must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating relative importance or indicating the number of technical features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The specific implementation of the present invention is described in more detail below in conjunction with specific embodiments:

[0036] like Figure 1 As shown, an embodiment of the present invention provides a method for connecting thermoplastic resin-based composite materials, comprising the following steps:

[0037] A first connecting layer 2 is laid on one side of the first composite material plate 1 and co-cured to form a first part to be welded A, and a second connecting layer 4 is laid on one side of the second composite material plate 3 and co-cured to form a second part to be welded B; wherein the first connecting layer 2 and the second connecting layer 4 are both connecting materials containing thermoplastic resin, and the first melting point of the connecting material is lower than the second melting point of the first composite material plate 1, and lower than the third melting point of the second composite material plate 2; specifically, the thickness of the first connecting layer 2 is less than one tenth of the thickness of the first composite material plate 1, and the thickness of the second connecting layer 4 is less than one tenth of the thickness of the second composite material plate 2.

[0038] Thermoplastic resin is solidified and connected on the surface of the heating element to form a composite heating element 5; the thermoplastic resin is of the same type as the thermoplastic resin of the first connecting layer 2 and the second connecting layer 4 to ensure that the material properties of the two are consistent. The thermoplastic resin solidified and connected on the surface of the heating element is of the same type as the connecting material, or is a different material with good compatibility. Specifically, the thermoplastic resin solidified and connected on the surface of the heating element has a fourth melting point, which is greater than the first melting point.

[0039] The composite heating element 5 is placed between the first connecting layer 2 and the second connecting layer 4, and the composite heating element 5 is heated to a preset welding temperature to melt the first connecting layer 2 and the second connecting layer 4;

[0040] The first workpiece to be welded A and the second workpiece to be welded B are pressurized to make the first connection layer 2 and the second connection layer 4 fit together, and then they are cooled and consolidated to obtain a composite material welded plate.

[0041] In one embodiment, the preset welding temperature is higher than the first melting point, and lower than the second melting point and the third melting point.

[0042] In one embodiment, the first connecting layer 2 is a resin film or a resin-based fabric prepreg containing a fabric reinforcement;

[0043] In one embodiment, the second connection layer 4 is a resin film or a resin-based textile prepreg containing textile reinforcement.

[0044] In one embodiment, the material of the fabric reinforcement includes carbon fiber and glass fiber, and the form of the fabric reinforcement includes plain weave, twill, satin and spread fabric.

[0045] In one embodiment, the surface weight of the fabric reinforcement is in the range of 50 to 400 g / m 2 .

[0046] In one embodiment, the melting point of the connecting material is at least 30° C. lower than that of the first composite material plate 1 , and the melting point of the connecting material is at least 30° C. lower than that of the second composite material plate 3 .

[0047] In one embodiment, the thermoplastic resin includes polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), nylon (PA), polyethylene (PE) and polypropylene (PP).

[0048] In one of the embodiments, during the co-curing process, the hot pressing temperature ranges from 200 to 400° C., the molding pressure ranges from 1.0 to 3.0 MPa, and the hot pressing time is 30 to 60 min.

[0049] In one embodiment, the material of the heating element includes carbon fiber and metal. In the connection of composite materials, the material of the heating element is generally preferably carbon fiber, and the carbon fiber can be implanted into the connection material as a reinforcement to further improve the connection strength of the welding interface.

[0050] In one embodiment, the first connection layer 2 comprises at least one layer of prepreg of a connection material; and / or the second connection layer 4 comprises at least one layer of prepreg of a connection material.

[0051] The following is an explanation of the thermoplastic resin-based composite material connection method provided in the present application in conjunction with specific embodiments: the experimental methods used in the following embodiments are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following embodiments are all commercially available unless otherwise specified.

[0052] Example 1

[0053] In this embodiment, the first composite material plate 1 and the second composite material plate 3 are both made of carbon fiber / polyetheretherketone laminates, the connecting material is SW110C / low melting point polyaryletherketone resin fabric prepreg with a resin content of 45%, the heating element is made of stainless steel metal mesh, and the polyaryletherketone resin layer is cured and connected on the surface of the heating element to form a composite heating element 5. The surface density of the glass cloth SW110C is 110g / m 2 , the carbon fiber / polyetheretherketone laminate layup is [0 / 90] 4s The melting point of low melting point polyaryletherketone resin is 306℃, and the melting point of polyetheretherketone resin is 343℃.

[0054] The specific steps are as follows:

[0055] 1. Co-curing: Lay the first connection layer 2 on one side of the first composite material plate 1, and co-curing to form the first welded part A. Lay the second connection layer 4 on one side of the second composite material plate 3, and co-curing to form the second welded part B. The co-curing process parameters are: the room temperature is raised to 370°C, the heating rate is 5°C / min, and the temperature is pressurized to 2MPa after reaching 370°C, and the temperature is kept constant for 30 minutes, and then the pressure is cooled to room temperature and demolded. Among them, the thickness of the first composite material plate 1 and the second composite material plate 3 is 2.5mm, and the thickness of the first connection layer 2 and the second connection layer 4 is 0.2mm.

[0056] 2. Resistance welding: The composite heating element 5 is fixed between the first connection layer 2 and the second connection layer 4, and a thin layer of K-type thermocouple is placed on the surface of the composite heating element 5 to detect the welding temperature. The two ends of the composite heating element 5 are connected to the power supply 7 through the wire 6. Figure 1As shown. Insulating pressure blocks 8 are placed above the first welded part A and below the second welded part B, and a pressure of 1.0 MPa is uniformly applied. The welding interface temperature is heated to 330±5℃ and kept constant for 30s, then heating is stopped and the temperature is cooled to room temperature at constant pressure to obtain a composite material welding plate.

[0057] 3. The above-mentioned composite material welded plate was processed into a single lap specimen with a width of 25.4 mm and a length of 176.6 mm. A single lap shear test was performed according to the ASTM D5868 standard. The single lap shear strength of the welded joint was 25.6 MPa.

[0058] Example 2

[0059] In this embodiment, the first composite material plate 1 and the second composite material plate 3 are both made of carbon fiber / polyetheretherketone laminates, the connecting material is 45% SW110C / polyetherimide resin fabric prepreg, the heating element is made of carbon fiber plain fabric, and the polyetherimide resin layer is cured and connected on the surface of the heating element to form a composite heating element 5. The surface density of the glass cloth SW110C is 110g / m 2 , the carbon fiber / polyetheretherketone laminate layup is [0 / 90] 4s The melting point of low melting point polyaryletherketone resin is 306℃, and the melting point of polyetheretherketone resin is 343℃.

[0060] The specific steps are as follows:

[0061] 1. Lay the first connection layer 2 on one side of the first composite material plate 1, and co-curing to form the first welded part A. Lay the second connection layer 4 on one side of the second composite material plate 3, and co-curing to form the second welded part B. The co-curing process parameters are: the room temperature is raised to 370°C, the heating rate is 5°C / min, and the temperature is pressurized to 1.5MPa after reaching 370°C, and the temperature is kept constant for 30 minutes, and then the pressure is cooled to room temperature and demolded. Among them, the thickness of the first composite material plate 1 and the second composite material plate 3 is 2.5mm, and the thickness of the first connection layer 2 and the second connection layer 4 is 0.2mm.

[0062] 2. Resistance welding: The composite heating element 5 is fixed between the first connection layer 2 and the second connection layer 4, and a thin layer of K-type thermocouple is placed on the surface of the composite heating element 5 to detect the welding temperature. The two ends of the composite heating element 5 are connected to the power supply 7 through the wire 6. Figure 1 As shown. Insulating pressure blocks 8 are placed above the first welded part A and below the second welded part B, and a pressure of 1.0 MPa is uniformly applied. The welding interface temperature is heated to 320±5℃ and kept at a constant temperature for 20s, then the heating is stopped and the temperature is cooled to room temperature at a constant pressure to obtain a composite material welding plate.

[0063] 3. The above-mentioned composite material welded plate was processed into a single lap specimen with a width of 25.4 mm and a length of 176.6 mm. A single lap shear test was performed according to the ASTM D5868 standard. The single lap shear strength of the welded joint was 23.5 MPa.

[0064] It can be seen from the test results of the above-mentioned Examples 1 and 2 that the joint strength of the composite material welded plate prepared by the thermoplastic resin-based composite material connection method provided by the present invention meets the strength requirements of the relevant standards.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for connecting thermoplastic resin-based composite materials, characterized in that: The following steps are involved: A first connecting layer is laid on one side of the first composite material plate, and co-cured to form a first workpiece to be welded; a second connecting layer is laid on one side of the second composite material plate, and co-cured to form a second workpiece to be welded; wherein the first connecting layer and the second connecting layer are both connecting materials containing thermoplastic resin, and the first melting point of the connecting material is lower than the second melting point of the first composite material plate, and lower than the third melting point of the second composite material plate; Curing and connecting the thermoplastic resin on the surface of the heating element to form a composite heating element; The composite heating element is placed between the first connecting layer and the second connecting layer, and the composite heating element is heated to a preset welding temperature to melt the first connecting layer and the second connecting layer; The first workpiece to be welded and the second workpiece to be welded are pressurized to make the first connecting layer fit with the second connecting layer, and then cooled and consolidated to obtain a composite material welded plate.

2. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The preset welding temperature is higher than the first melting point, and lower than the second melting point and the third melting point.

3. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The first connecting layer is a resin film or a resin-based fabric prepreg containing a fabric reinforcement; And / or, the second connecting layer is a resin film or a resin-based fabric prepreg containing a fabric reinforcement.

4. The method for connecting thermoplastic resin-based composite materials according to claim 3, characterized in that: The material of the fabric reinforcement includes carbon fiber and glass fiber, and the form of the fabric reinforcement includes plain weave, twill, satin and spread fabric.

5. The method for connecting thermoplastic resin-based composite materials according to claim 3, characterized in that: The surface weight of the fabric reinforcement is in the range of 50 to 400 g / m 2 .

6. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The melting point of the connecting material is at least 30° C. lower than the melting point of the first composite sheet, and the melting point of the connecting material is at least 30° C. lower than the melting point of the second composite sheet.

7. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The thermoplastic resin includes polyaryletherketone, polyetheretherketone, polyetherketoneketone, polyetherimide, polyphenylene sulfide, nylon, polyethylene and polypropylene.

8. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: During the co-curing process, the hot pressing temperature ranges from 200 to 400° C., the molding pressure ranges from 1.0 to 3.0 MPa, and the hot pressing time is 30 to 60 min.

9. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The materials of the heating element include carbon fiber and metal.

10. The method for connecting thermoplastic resin-based composite materials according to claim 1, characterized in that: The first connection layer comprises at least one layer of prepreg of a connection material; and / or the second connection layer comprises at least one layer of prepreg of a connection material.

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