Ultrasonic continuous welding method for fiber reinforced thermoplastic composite honeycomb structure

Abstract

The present invention discloses an ultrasonic continuous welding method for a fiber-reinforced thermoplastic composite honeycomb structure, and belongs to the technical field of thermoplastic composite welding. The welding method provided by the present invention includes: vertically and symmetrically abutting two corrugated boards, clamping independent energy-conducting ribs at all abutting points, and then starting ultrasonic continuous welding at the abutting points to obtain a first structural unit; vertically abutting the corrugated boards on both sides of the first structural unit respectively, clamping independent energy-conducting ribs at all abutting points, and then synchronously starting ultrasonic continuous welding at multiple abutting points, repeating the steps of vertical abutting, clamping independent energy-conducting ribs and ultrasonic continuous welding until a fiber-reinforced thermoplastic composite honeycomb structure is formed. The present invention can realize efficient welding of large-size honeycomb structures, effectively avoid the problem of corrugated board deformation, and can also realize high-strength interface bonding of thermoplastic composite honeycomb structures.

Description

Technical Field

[0001] The invention relates to the technical field of thermoplastic composite welding, and in particular to an ultrasonic continuous welding method for a fiber reinforced thermoplastic composite honeycomb structure. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Honeycomb structural materials have outstanding comprehensive mechanical properties, dimensional stability and multiple functional characteristics. They have been paid special attention and widely used in application fields such as satellites, fighter jets and automotive armor plates. At present, honeycomb structural materials usually use metal materials such as aluminum and titanium. Compared with metal materials, fiber-reinforced resin-based composite materials have relatively low density, high compression ratio stiffness and specific strength, and small thermal expansion coefficient. In the field of satellites and other high-precision structural parts, metal honeycomb structures have been gradually replaced by fiber-reinforced composite honeycomb structures.

[0004] The modulus of thermoplastic composites is relatively high at room temperature, and the viscosity of the resin after melting is relatively high, making it difficult to form and process large-sized complex structural parts in one go. Therefore, in the process of broadening the application path of thermoplastic composites, it is crucial to optimize their connection and assembly technology. Compared with traditional thermosetting resins, thermoplastic resins can soften and melt after heating, so welding technology can be used to connect and assemble thermoplastic composite components. Among them, ultrasonic welding has the advantages of high efficiency, good joint quality, little damage to the composite surface, intelligent control, and green and pollution-free. It is considered to be one of the most suitable connection methods for thermoplastic composites.

[0005] The patent with publication number CN116176001A (publication date: 2023.05.30) discloses a method for preparing a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, which first prepares a corrugated board with an energy-guiding structure by a molding process, and then prepares a honeycomb core by ultrasonic spot welding layer by layer on a horizontal workbench. The method of this patent mainly has the following problems: First, since its ultrasonic welding process requires downward pressure, under the combined influence of pressure and gravity, it is easy to cause the deformation of the thermoplastic composite corrugated board below, thereby affecting the strength and stability of the thermoplastic honeycomb structure. Second, the thickness of the honeycomb structure finally obtained by the patent is within 5cm, and it is difficult to effectively seal and connect the larger-sized thermoplastic composite honeycomb structure using its method. Third, the method of this patent requires ultrasonic spot welding connection layer by layer, and the connection efficiency is low. Fourth, the patent needs to first prepare a corrugated board with an energy-guiding structure by a molding process. This step has higher requirements for mold precision, so the equipment cost is relatively high.

[0006] The patent with publication number CN117841434A (publication date: 2024.04.09) discloses a preparation process for a continuous fiber reinforced thermoplastic composite honeycomb core, which uses ultrasonic offset spot welding to connect continuous fiber reinforced thermoplastic unidirectional sheets to obtain a composite honeycomb blank, and then uses a stretching machine to stretch and shape the composite honeycomb blank to obtain a continuous fiber reinforced thermoplastic composite honeycomb core. This method is also only applicable to the preparation of thermoplastic composite honeycomb cores of smaller thickness. When the size of the thermoplastic unidirectional sheet is too large, it is difficult to ensure the uniformity of the honeycomb structure after stretching, and the stretching process will also affect the strength of the honeycomb structure, and it is impossible to obtain a high-quality thermoplastic composite honeycomb structure.

[0007] Therefore, how to provide an efficient and low-cost ultrasonic welding method to prepare a thermoplastic composite honeycomb structure with high interface connection strength and high quality is an urgent problem to be solved. Summary of the invention

[0008] In view of this, the present invention provides an ultrasonic continuous welding method for a fiber reinforced thermoplastic composite honeycomb structure, which can achieve efficient molding of the fiber reinforced thermoplastic composite honeycomb structure and high-quality interface sealing and connection of large-size thermoplastic composite honeycomb structures, and has low equipment cost.

[0009] The present invention provides an ultrasonic continuous welding method for a fiber reinforced thermoplastic composite honeycomb structure, comprising the following steps:

[0010] S1. vertically and symmetrically abut two fiber-reinforced thermoplastic composite corrugated plates, clamp independent energy-guiding ribs at all abutting points, and then start ultrasonic continuous welding on the abutting points to obtain a first structural unit;

[0011] S2, vertically abutting the fiber-reinforced thermoplastic composite corrugated plates on both sides of the first structural unit, clamping independent energy-guiding ribs at all abutting points, and then simultaneously starting ultrasonic continuous welding on multiple abutting points;

[0012] S3. Repeat the steps of vertically abutting the fiber-reinforced thermoplastic composite corrugated sheets on both sides of the welded structural unit, clamping independent energy-guiding ribs at all abutments, and simultaneously starting ultrasonic continuous welding at multiple abutments until a fiber-reinforced thermoplastic composite honeycomb structure is formed.

[0013] Preferably, in step S1, the step of starting ultrasonic continuous welding at the abutment is specifically as follows:

[0014] Fixing the bottom and the top of the fiber-reinforced thermoplastic composite corrugated board, and starting ultrasonic continuous welding on the abutment between the bottom and the top; then fixing the welded abutment, and starting ultrasonic continuous welding on the abutment between the bottom and the top;

[0015] or,

[0016] The abutment between the bottom and the top of the fiber reinforced thermoplastic composite corrugated board is fixed, and ultrasonic continuous welding of the bottom and the top is started; then the welded abutment is fixed, and ultrasonic continuous welding of the abutment between the bottom and the top is started.

[0017] Preferably, the independent energy guiding ribs are planar energy guiding ribs with a thickness of 0.05-0.5 mm, and the length and width of the independent energy guiding ribs are respectively the same as the length and width of the surface to be welded at the abutment; the material of the independent energy guiding ribs is thermoplastic resin.

[0018] Furthermore, the thermoplastic resin is of the same type as the thermoplastic resin of the fiber-reinforced thermoplastic composite corrugated board.

[0019] Preferably, the thermoplastic resin in the fiber-reinforced thermoplastic composite corrugated board includes one or more of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyetherketoneketone (PEKK), polyetherimide (PEI) or polyetherketone (PEK); the fiber in the fiber-reinforced thermoplastic composite corrugated board includes one or more of carbon fiber, basalt fiber, aramid fiber, graphite fiber, glass fiber, ceramic fiber, boron fiber, polyamide fiber, polyethylene fiber, PBO fiber (poly(p-phenylene benzobisoxazole) fiber), polyester fiber or natural fiber.

[0020] Preferably, in steps S1 to S3, the step of initiating ultrasonic continuous welding on the abutment is specifically: supporting one side of the abutment with a supporting component, and then initiating ultrasonic continuous welding on the other side of the abutment.

[0021] Furthermore, in steps S2 and S3, the support component is placed in the structural unit formed after welding, and the ultrasonic continuous welding is performed on the outside of the structural unit formed after welding.

[0022] Preferably, the ultrasonic continuous welding of steps S1 to S3 includes a pre-pressing stage, a welding stage and a pressure holding stage.

[0023] Furthermore, the pressure in the pre-pressing stage is 100-500N, and the pressure in the welding stage and the pressure-holding stage is 400-2000N.

[0024] Preferably, the amplitude of the ultrasonic continuous welding in steps S1 to S3 is 20 to 100 μm, the frequency is 10 to 50 kHz, and the welding speed is 10 to 40 mm / s.

[0025] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0026] (1) The present invention adopts an ultrasonic continuous welding process to weld the vertically fixed fiber-reinforced thermoplastic composite corrugated sheet, and welds on both sides of the first structural unit at the same time, and multiple surfaces to be welded are effectively sealed and connected at the same time, so that efficient welding of large-size honeycomb structures can be achieved, and the problem of corrugated sheet deformation can be effectively avoided, which is beneficial to improving the stability of the honeycomb structure;

[0027] (2) The present invention adopts independent energy guiding ribs to replace the traditional energy guiding structures prepared by molding, injection molding or pultrusion, which significantly improves the uniformity of heat generation at the interface, eliminates defects at the welding interface and inside the composite material, significantly improves the quality of the weld and the strength of the joint, and realizes high-strength interface bonding of the thermoplastic composite honeycomb structure, while also reducing equipment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 is a schematic diagram of welding of the central area of ​​the first structural unit of Example 1 of the present invention;

[0030] Figure 2 is a schematic diagram of welding of the edge region of the first structural unit of Example 1 of the present invention;

[0031] Figure 3 is a schematic diagram of welding of the central area of ​​the second structural unit of Example 1 of the present invention;

[0032] Figure 4 is a schematic diagram of welding of the central area of ​​the third structural unit of Example 1 of the present invention;

[0033] In the figure, 1, the first corrugated board; 2, the edge area fixing clamp; 3, the support tube; 4, the ultrasonic welding head; 5, the center area fixing clamp; 6, the second corrugated board; 7, the third corrugated board. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0035] At present, the existing ultrasonic spot welding technology of thermoplastic composite honeycomb structure faces multiple bottleneck problems such as relatively low connection efficiency, high equipment cost, limited by the size of the honeycomb structure, poor uniformity of heat generation at the interface, which easily causes defects at the interface and inside the composite material, and easily causes deformation of the corrugated board below. In view of this, the present invention provides an ultrasonic continuous welding method for a fiber reinforced thermoplastic composite honeycomb structure, comprising the following steps:

[0036] S1. vertically and symmetrically abut two fiber-reinforced thermoplastic composite corrugated plates, clamp independent energy-guiding ribs at all abutting points, and then start ultrasonic continuous welding on the abutting points to obtain a first structural unit;

[0037] S2, vertically abutting the fiber-reinforced thermoplastic composite corrugated plates on both sides of the first structural unit, clamping independent energy-guiding ribs at all abutting points, and then simultaneously starting ultrasonic continuous welding on multiple abutting points;

[0038] S3. Repeat the steps of vertically abutting the fiber-reinforced thermoplastic composite corrugated sheets on both sides of the welded structural unit, clamping independent energy-guiding ribs at all abutments, and simultaneously starting ultrasonic continuous welding at multiple abutments until a fiber-reinforced thermoplastic composite honeycomb structure is formed.

[0039] In the present invention, the independent energy guiding ribs refer to energy guiding ribs that are independent of the corrugated board. The use of independent energy guiding ribs in the present invention can obtain better interface bonding quality. The clamping of independent energy guiding ribs at the abutment points described in the present invention refers to clamping and fixing the independent energy guiding ribs between the corrugated boards on both sides when the corrugated boards on both sides abut. Each abutment point constitutes a surface to be welded. The "multiple" in the simultaneous initiation of ultrasonic continuous welding at multiple abutments described in the present invention means greater than or equal to two; "synchronous" means that the ultrasonic continuous welding process is carried out simultaneously and the welding direction is consistent.

[0040] The present invention does not impose any special restrictions on the unit structure of the fiber-reinforced thermoplastic composite corrugated board, for example, it can be a waveform, a semicircle, a semi-hexagon, etc., as long as it can be connected to form a honeycomb structure. The present invention does not impose any special restrictions on the thickness of the fiber-reinforced thermoplastic composite corrugated board, preferably 0.5~5mm. The fiber-reinforced thermoplastic composite honeycomb structure of the present invention has a honeycomb cell pore side length (if it is a circular honeycomb, it is the radius) of 2~50mm, and a honeycomb cell spacing of 2~50mm. The overall size of the honeycomb structure depends on the honeycomb cell pore side length, cell spacing and cell number.

[0041] The present invention does not impose any special restrictions on the preparation process of the fiber-reinforced thermoplastic composite corrugated board. For example, the fiber-reinforced thermoplastic composite corrugated board can be prepared by compression molding, injection molding, pultrusion molding, and the like.

[0042] In step S1 of the present invention, the step of starting ultrasonic continuous welding at the abutment is specifically as follows:

[0043] Fixing the bottom and the top of the fiber-reinforced thermoplastic composite corrugated board, and starting ultrasonic continuous welding on the abutment between the bottom and the top; then fixing the welded abutment, and starting ultrasonic continuous welding on the abutment between the bottom and the top;

[0044] or,

[0045] The abutment between the bottom and the top of the fiber reinforced thermoplastic composite corrugated board is fixed, and ultrasonic continuous welding of the bottom and the top is started; then the welded abutment is fixed, and ultrasonic continuous welding of the abutment between the bottom and the top is started.

[0046] The fixing described in the present invention is preferably clamping fixing, and there is no special restriction on the fixing components, as long as the two parts can be stably abutted and the independent energy guiding ribs can be ensured not to move.

[0047] In the present invention, the independent energy conductor is preferably a planar energy conductor with a thickness of 0.05-0.5 mm. The length and width of the independent energy conductor are respectively the same as the length and width of the surface to be welded at the abutment. The material of the independent energy conductor is a thermoplastic resin, which is the same type as the thermoplastic resin of the fiber-reinforced thermoplastic composite corrugated board. During the ultrasonic continuous welding process, the resin melts under the heat generated by the ultrasonic wave and then diffuses at the interface. Due to the same type of resin, the planar energy conductor has good compatibility with the corrugated board, and it is easy to achieve integration of the workpiece and the weld, and the interface bonding strength is high.

[0048] In the present invention, the thermoplastic resin in the fiber-reinforced thermoplastic composite corrugated board includes one or more of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyetherketoneketone (PEKK), polyetherimide (PEI) or polyetherketone (PEK); the fiber in the fiber-reinforced thermoplastic composite corrugated board includes one or more of carbon fiber, basalt fiber, aramid fiber, graphite fiber, glass fiber, ceramic fiber, boron fiber, polyamide fiber, polyethylene fiber, PBO fiber (poly(p-phenylene benzobisoxazole) fiber), polyester fiber or natural fiber. The fiber reinforcement phase of the present invention is continuous fiber or long fiber (length ≥ 6 mm), and the weaving of continuous fiber can adopt common weaving methods such as plain weave, twill and satin weave, and the volume content of the fiber reinforcement phase is preferably 30~65%.

[0049] In steps S1 to S3 of the present invention, the step of starting ultrasonic continuous welding at the abutment is specifically as follows: using a support component to support one side of the abutment to ensure the stability of the honeycomb structure during ultrasonic vibration and the close fit between the welding head and the area to be welded; then starting ultrasonic continuous welding on the other side of the abutment. Furthermore, in steps S2 and S3, the support component is placed in the structural unit formed after welding, and the ultrasonic continuous welding is performed on the outside of the structural unit formed after welding, that is, the ultrasonic continuous welding equipment is kept acting on the outside of the structural unit formed by welding, which is easy to operate. The present invention does not impose any special restrictions on the support component, and its shape can be adaptively designed according to the formed honeycomb structure, preferably a round rod or an inflatable cylinder, and its diameter must be smaller than the single cell diameter of the honeycomb structure, that is, it can smoothly extend into the interior of the honeycomb single cell, thereby effectively supporting the abutment.

[0050] In the present invention, the ultrasonic continuous welding of steps S1 to S3 includes a pre-pressing stage, a welding stage and a pressure holding stage, which is determined by the ultrasonic continuous welding equipment. The ultrasonic continuous welding equipment includes a pre-pressing unit, a welding unit and a pressure holding unit. As the welding proceeds, the pre-pressing, welding and pressure holding operations are performed on the welding parts in sequence to ensure that the weld has a high quality.

[0051] In the present invention, the pressure in the pre-pressing stage is 100-500 N, and the pressure in the welding stage and the pressure-holding stage is 400-2000 N. The specific parameters are determined according to the type of material of the selected fiber-reinforced thermoplastic composite.

[0052] In the present invention, the amplitude of the ultrasonic continuous welding in steps S1 to S3 is 20 to 100 μm, the frequency is 10 to 50 kHz, and the welding speed is 10 to 40 mm / s.

[0053] The present invention does not impose any special restrictions on the number of honeycomb structure layers, and the timing of ending welding can be determined according to actual requirements.

[0054] The present invention does not impose any special restrictions on the welding device used in the above welding method, which preferably includes a fixed clamping unit, a supporting unit and an ultrasonic welding unit.

[0055] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0056] The length and width of the corrugated board referred to in the following examples refer to the projected lengths in the length direction and the width direction of the corrugated board when the corrugated board is placed horizontally. In the following examples, the single lap shear strength of the obtained welded joints was tested according to the method disclosed in GB / T 33334-2016, and 5 groups of specimens were taken at different positions of the weld to obtain the average shear strength.

[0057] Example 1

[0058] This embodiment provides an ultrasonic continuous welding method for a fiber-reinforced thermoplastic composite honeycomb structure. The fiber-reinforced thermoplastic composite corrugated board (hereinafter referred to as corrugated board) used is made of T700 unidirectional continuous carbon fiber reinforced polyetheretherketone (PEEK) composite prepreg through flat hot pressing and hot molding process, and its cross-sectional unit cell shape is a semi-hexagon; the thickness of the corrugated board is 3mm, the length is 200mm, and the width is 350mm; the planar energy-conducting rib used is a PEEK film with a thickness of 0.2mm. The size of a single surface to be welded of the corrugated board is 200 mm × 50 mm (the length is the same as the length of the corrugated board as a whole), and the size of the PEEK film is the same as the size of the surface to be welded, which is 200 mm × 50 mm.

[0059] (1) Schematic diagram of continuous welding of the first structural unit (single-layer honeycomb structure) Figure 1 and Figure 2 As shown, the specific steps are as follows:

[0060] ① Degreasing the surfaces to be welded of the two first corrugated sheets 1 and the surfaces of the PEEK film energy conductors is performed with isopropyl alcohol.

[0061] ② Fix the PEEK film energy guiding ribs (not shown in the figure) to the surfaces to be welded in the central area and edge area of ​​the first corrugated board 1, so that they abut against the surfaces to be welded on both sides; place the two first corrugated boards 1 vertically, and use the edge area fixing clamps 2 to fix the upper and lower edge areas of the first corrugated boards 1 with a pressure of 200 N; use the support tube 3 to support one side of the surface to be welded (abutment) in the central area of ​​the first corrugated board 1.

[0062] ③ Under the conditions of amplitude 80μm and frequency 20 kHz, a welding pressure of 800 N is applied perpendicular to the surface to be welded, the ultrasonic continuous welding equipment is started, and the ultrasonic welding head 4 is controlled to contact one side of the surface to be welded. After reaching the preset trigger condition, the ultrasonic continuous welding process is started. The pre-pressing pressure and the holding pressure are set to 300 N and 500 N respectively. The ultrasonic welding head 4 moves along the area to be welded at a welding speed of 15mm / s until the sealing and connection of the entire central area to be welded is completed. The ultrasonic equipment is turned off, and a continuous welded joint is formed after cooling. The single lap shear strength of the continuous welded joint in the central area is measured to be 35.2±2.1 MPa.

[0063] ④ The central area fixing clamp 5 is used to fix the central welded area of ​​the first corrugated board 1 with a pressure of 200 N; the support tube 3 is used to support one side of the central area of ​​the first corrugated board 1 to be welded (butt joint); under the conditions of amplitude 80 μm and frequency 20kHz, a welding pressure of 800 N perpendicular to the lap interface is applied, the ultrasonic continuous welding equipment is started, and the ultrasonic welding head 4 is controlled to contact one side of the surface to be welded. After reaching the preset trigger condition, the ultrasonic continuous welding process is started. The pre-pressing pressure and the holding pressure are set to 300 N and 500 N respectively. The ultrasonic welding head 4 moves along the area to be welded at a welding speed of 15 mm / s until the sealing and connection of the entire edge area to be welded is completed, the ultrasonic equipment is turned off, and a continuous welded joint is formed after cooling, and the welding of the first structural unit is completed to obtain a single-layer honeycomb structure. The single lap shear strength of the continuous welded joint in the edge area is measured to be 37.1±1.5 MPa.

[0064] (2) The welding steps of the second structural unit are as follows: Figure 3 As shown, the specific steps are as follows:

[0065] ① The surface to be welded in the central area of ​​the first structural unit in step (1) and the surface of the PEEK film energy conductor are degreased with isopropyl alcohol, and the PEEK film energy conductor is fixed to the surface to be welded in the central area and edge area on both sides of the first structural unit.

[0066] ② Place the two second corrugated sheets 6 in contact with the surface to be welded in the central area of ​​the first structural unit, and use the edge area fixing clamp 2 to fix the second corrugated sheets 6 and the edge area of ​​the first structural unit with a pressure of 200 N. Use the support tube 3 to extend into the internal gap of the first structural unit and support the surface to be welded.

[0067] ③ Under the conditions of amplitude 80 μm and frequency 20 kHz, a welding pressure of 800 N was applied perpendicular to the surface to be welded, the ultrasonic continuous welding equipment was started, and the ultrasonic welding heads 4 on both sides of the first structural unit were controlled to contact the surface to be welded at the same time. After reaching the preset trigger conditions, the ultrasonic continuous welding process was started. The pre-pressing pressure and the holding pressure were set to 300 N and 500 N, respectively. The ultrasonic welding head 4 moved along the area to be welded at a welding speed of 15 mm / s until the sealing and connection of the entire central area to be welded was completed. The ultrasonic equipment was turned off, and a continuous welded joint was formed after cooling to obtain the second structural unit. The single lap shear strength of the continuous welded joint in the central area of ​​the second structural unit was measured to be 35.0±1.9 MPa.

[0068] ④ Complete the sealing and connection of the surface to be welded in the edge area of ​​the second structural unit in the same manner as step ④ of step (1).

[0069] (3) The welding steps of the third structural unit are as follows: Figure 4 As shown, the specific steps are as follows:

[0070] ① The surface to be welded in the central area of ​​the second structural unit in step (2) and the surface of the PEEK film energy conductor are degreased with isopropyl alcohol, and the PEEK film energy conductor is fixed to the surface to be welded in the central area and edge area on both sides of the second structural unit.

[0071] ② Place the two third corrugated sheets 7 in contact with the surface to be welded in the central area of ​​the second structural unit, and use the edge area fixing clamp 2 to fix the third corrugated sheets 7 and the edge area of ​​the second structural unit with a pressure of 200 N. Use the support tube 3 to extend into the internal gap of the second structural unit and support the surface to be welded.

[0072] ③ Under the conditions of amplitude of 80 μm and frequency of 20 kHz, a welding pressure of 800 N is applied perpendicular to the surface to be welded, the ultrasonic continuous welding equipment is started, and the ultrasonic welding heads 4 on both sides of the second structural unit are controlled to contact the surface to be welded at the same time. After reaching the preset trigger condition, the ultrasonic continuous welding process is started. The pre-pressing pressure and the holding pressure are set to 300 N and 500 N respectively. The ultrasonic welding head 4 moves along the area to be welded at a welding speed of 15 mm / s until the sealing and connection of the surface to be welded in the entire central area are completed. The ultrasonic equipment is turned off, and a continuous welded joint is formed after cooling to obtain the third structural unit (i.e., a three-layer honeycomb structure). The single lap shear strength of the continuous welded joint in the central area of ​​the third structural unit is measured to be 35.1±1.5 MPa.

[0073] ④ The sealing and connection of the surface to be welded in the edge area of ​​the third structural unit is completed in the same manner as step ④ of step (2). The single lap shear strength of the continuous welded joint in the edge area of ​​the third structural unit is measured to be 36.8±1.7MPa.

[0074] Comparative Example 1

[0075] This comparative example uses ultrasonic spot welding to weld the three-layer honeycomb structure of the horizontally placed corrugated board. The material and preparation process of the corrugated board used are the same as those of Example 1, and the cross-sectional unit cell shape is a semi-hexagon; the thickness of the corrugated board is 3 mm, the length is 350 mm, and the width is 50 mm; the planar energy conductor used is a PEEK film with a thickness of 0.2 mm. The size of a single surface of the corrugated board to be welded is 50 mm × 50 mm, and the size of the PEEK film is the same as the size of the surface to be welded, which is 50 mm × 50 mm.

[0076] (1) Welding of the first layer of honeycomb structure: Degrease the surfaces to be welded and the PEEK film energy guide ribs of the two corrugated plate workpieces, place the two corrugated plate workpieces horizontally, place the PEEK film energy guide ribs on the surfaces to be welded, and fix them above the plane support anvil by a clamp. Ultrasonic spot welding is used to connect the areas to be welded under the conditions of amplitude of 80 μm and frequency of 20 kHz to obtain a welded joint, completing the welding of the first layer of honeycomb structure. The welding pressure and holding pressure are set to 1000 N and 800 N, respectively. The single lap shear strength of the welded joint obtained in step (1) was measured to be 34.8±3.1 MPa.

[0077] (2) Welding of the second honeycomb structure: The degreased corrugated sheet workpiece is placed horizontally on the surface of the first honeycomb structure in step (1), and a PEEK film energy guide is placed on the surface to be welded. It is fixed by a clamping block so that the surface to be welded of the corrugated sheet workpiece is in contact with the surface to be welded of the first honeycomb structure. Ultrasonic spot welding is used to connect the areas to be welded under the conditions of an amplitude of 80 μm and a frequency of 20 kHz to complete the welding of the second honeycomb structure. The welding pressure and the holding pressure are set to 1000 N and 800 N, respectively. The single lap shear strength of the welded joint obtained in step (2) is 32.0±2.2 MPa.

[0078] (3) Welding of the third honeycomb structure: The degreased corrugated sheet workpiece is placed horizontally on the surface of the second honeycomb structure in step (1), and a PEEK film energy guide is placed on the surface to be welded. It is fixed by a clamping block so that the surface to be welded of the corrugated sheet workpiece is in contact with the surface to be welded of the second honeycomb structure. Ultrasonic spot welding is used to connect the areas to be welded under the conditions of an amplitude of 80 μm and a frequency of 20 kHz to complete the welding of the third honeycomb structure. The welding pressure and the holding pressure are set to 1000 N and 800 N, respectively. The single lap shear strength of the welded joint obtained in step (3) is 31.6±2.4 MPa.

[0079] From the comparison between comparative example 1 and embodiment 1, it can be seen that the welded joint strength obtained by the welding method of embodiment 1 is higher, indicating that the welding interface quality is better, and the welding method of embodiment 1 can weld on both sides of the first structural unit at the same time, which is more efficient, and can also effectively avoid the problem of corrugated board deformation, and has higher stability. In addition, comparative example 1 can only complete the connection of smaller-sized corrugated boards, and cannot connect the large-sized corrugated boards of embodiment 1.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that this comparative example obtains the corrugated board with triangular PEEK energy-conducting structure on the convex side of the corrugation by compression molding, that is, the PEEK film energy-conducting ribs of Example 1 are not used.

[0082] Sampling was taken from the central welding area of ​​the first structural unit of this comparative example, and the single lap shear strength of the continuous welded joint in the central area was measured to be 33.1±2.8 MPa; sampling was taken from the edge welding area of ​​the first structural unit of this comparative example, and the single lap shear strength of the continuous welded joint in the edge welding area was measured to be 31.5±2.4 MPa.

[0083] It can be seen that the welded joint strength obtained by using independent PEEK film energy guiding ribs is higher than that obtained by using corrugated board with energy guiding structure, and the strength difference of continuous welded joints in the edge area is greater than that in the center area.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultrasonic continuous welding method for a fiber-reinforced thermoplastic composite honeycomb structure, characterized in that: The steps include: S1. Two fiber-reinforced thermoplastic composite corrugated sheets are vertically and symmetrically abutted, independent energy-conducting ribs are clamped at all abutting points, and then ultrasonic continuous welding is started at the abutting points to obtain a first structural unit; the specific step of starting ultrasonic continuous welding at the abutting points is: fixing the bottom and the top of the fiber-reinforced thermoplastic composite corrugated sheet, and starting ultrasonic continuous welding at the abutting point between the bottom and the top; then fixing the welded abutting points, and starting ultrasonic continuous welding at the abutting points between the bottom and the top; S2, vertically abutting the fiber-reinforced thermoplastic composite corrugated plates on both sides of the first structural unit, clamping independent energy-guiding ribs at all abutting points, and then simultaneously starting ultrasonic continuous welding on multiple abutting points; S3, repeating the steps of vertically abutting the fiber-reinforced thermoplastic composite corrugated sheet on both sides of the welded structural unit, clamping independent energy guiding ribs at all abutments, and simultaneously starting ultrasonic continuous welding on multiple abutments until a fiber-reinforced thermoplastic composite honeycomb structure is formed; Among them, in steps S1 to S3, the step of starting ultrasonic continuous welding on the abutment is specifically: using a supporting component to support one side of the abutment, and then starting ultrasonic continuous welding on the other side of the abutment; The independent energy conductor is a planar energy conductor with a thickness of 0.05-0.5 mm. The length and width of the independent energy conductor are respectively the same as the length and width of the surface to be welded at the abutment. The material of the independent energy conductor is thermoplastic resin. In steps S2 and S3, the support component is placed in the structural unit formed after welding, and the ultrasonic continuous welding is performed on the outside of the structural unit formed after welding.

2. The ultrasonic continuous welding method of the fiber reinforced thermoplastic composite honeycomb structure according to claim 1, characterized in that: The thermoplastic resin is of the same type as the thermoplastic resin of the fiber-reinforced thermoplastic composite corrugated board.

3. The ultrasonic continuous welding method of the fiber reinforced thermoplastic composite honeycomb structure according to claim 1, characterized in that: The thermoplastic resin in the fiber-reinforced thermoplastic composite corrugated board includes one or more of polyetheretherketone, polyphenylene sulfide, polyetherketoneketone, polyetherimide or polyetherketone; the fibers in the fiber-reinforced thermoplastic composite corrugated board include one or more of carbon fiber, basalt fiber, aramid fiber, graphite fiber, glass fiber, ceramic fiber, boron fiber, polyamide fiber, polyethylene fiber, PBO fiber, polyester fiber or natural fiber.

4. The ultrasonic continuous welding method of a fiber reinforced thermoplastic composite honeycomb structure according to claim 1, characterized in that: The ultrasonic continuous welding of steps S1 to S3 includes a pre-pressing stage, a welding stage and a pressure holding stage.

5. The ultrasonic continuous welding method of the fiber reinforced thermoplastic composite honeycomb structure according to claim 4, characterized in that: The pressure in the pre-pressing stage is 100-500N, and the pressure in the welding stage and the pressure-holding stage is 400-2000N.

6. The ultrasonic continuous welding method of the fiber reinforced thermoplastic composite honeycomb structure according to claim 4, characterized in that: The amplitude of the ultrasonic continuous welding in steps S1 to S3 is 20 to 100 μm, the frequency is 10 to 50 kHz, and the welding speed is 10 to 40 mm / s.

Images