A continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, preparation device and preparation method

Abstract

The present invention provides a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, comprising an upper panel, a honeycomb core and a lower panel; the honeycomb core is formed by welding corrugated plates made of continuous fiber reinforced thermoplastic resin unidirectional prepregs; both the upper panel and the lower panel are compression molded from continuous fiber reinforced thermoplastic resin unidirectional prepregs; the resin types used for the upper panel, the honeycomb core and the lower panel are the same. The present invention also provides a preparation device and a preparation method for the above honeycomb sandwich structure. In view of the deficiencies of the prior art, the present invention respectively solves the problems of the preparation of thermoplastic composite corrugated plates with energy directors, the design of ultrasonic welding preparation tooling, and the design of the honeycomb body interface and the core connection process of the sandwich structure surface. On this basis, by integrating the above key technologies to form a working pipeline, the efficient and rapid preparation of lightweight and high-strength all continuous fiber reinforced thermoplastic composite honeycomb cores and sandwich structures is realized.

Description

Technical Field:

[0001] The present invention belongs to the technical field of composite material honeycombs, and particularly relates to a continuous fiber reinforced thermoplastic composite material honeycomb sandwich structure, a preparation device and a preparation method. Background Art:

[0002] Honeycomb sandwich composites have been widely used in the fields of aerospace, deep-sea exploration, automobiles and rail transit due to their excellent mechanical properties, dimensional stability, and multifunctional characteristics such as wave absorption, noise elimination, and heat insulation. In the prior art, the more widely used honeycomb sandwich structures are generally prepared by connecting traditional core materials such as aluminum honeycombs and paper honeycombs with metal panels or composite material panels through connection forms such as brazing or bonding. Among them, metal honeycomb sandwich structures such as aluminum honeycombs have been gradually replaced by carbon fiber composite material honeycombs in the fields of satellites and high-precision structural components due to their high density, low compression specific stiffness and specific strength, significant thermal expansion, and significant galvanic corrosion when combined with carbon fiber panels. Nomex aramid paper honeycomb improves the problem of poor mechanical properties of traditional paper honeycombs by loading aramid short fibers and precipitated fibers, but it still has defects in terms of anti-humid heat aging and weather resistance, and the phenolic resin it loads is a thermosetting resin, significantly reducing its recycling and reuse ability.

[0003] With the continuous improvement of the requirements for lightweight and environmental protection of various high-end equipment, new demands have been put forward for the development of new lightweight, high-strength, and recyclable all-composite material honeycomb sandwich structures.

[0004] Compared with aluminum alloy honeycombs, the specific stiffness of continuous fiber reinforced thermoplastic resin matrix composite material honeycombs such as carbon fiber and glass fiber is increased by about 2 - 3 times, and the specific strength is increased by about 4 - 5 times. Moreover, according to the bearing requirements, targeted design can be carried out to obtain the required stiffness and strength. At the same time, compared with thermosetting composite materials, thermoplastic composite materials have excellent impact resistance characteristics, higher damage tolerance, and the characteristics of being able to repeatedly rise and fall in temperature. No additional adhesive film is required for the connection between the surface and the core, and all materials can be recycled and reused, with high resource utilization rate. However, thermoplastic composite materials have a high modulus at room temperature, and the processing and forming are difficult. The bonding-tensile preparation method of traditional metal honeycombs and paper honeycombs is no longer applicable. If the corrugated board bonding method of thermosetting composite materials is used for preparation, since the honeycomb as a whole is softened by heat at high temperature, in addition to the fact that the honeycomb node interface cannot be effectively compressed and cured, it will also affect the final forming accuracy of the honeycomb.

[0005] Based on the above technical status, it is urgent to develop a rapid preparation device and a preparation method for continuous fiber reinforced thermoplastic composite material honeycomb cores and sandwich structures. Summary of the Invention:

[0006] The object of the present invention is to provide a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, a preparation device and a preparation method in view of the deficiencies of the prior art. Through the preparation of thermoplastic composite corrugated plates with energy guiding structures, the design of ultrasonic welding preparation tooling, and the design of the honeycomb body interface and the core connection process of the sandwich structure surface, the rapid preparation of lightweight and high-strength fully continuous fiber reinforced thermoplastic composite honeycomb cores and sandwich structures is realized.

[0007] The present invention adopts the following technical solutions:

[0008] (1) A continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, including an upper panel, a honeycomb core and a lower panel; the honeycomb core is formed by welding corrugated plates made of continuous fiber reinforced thermoplastic resin unidirectional prepregs; both the upper panel and the lower panel are molded from continuous fiber reinforced thermoplastic resin unidirectional prepregs.

[0009] Furthermore, in the continuous fiber reinforced thermoplastic resin unidirectional prepreg, continuous fibers are used as the reinforcement, specifically one or more of carbon fiber, glass fiber, aramid fiber, quartz fiber, basalt fiber and natural fiber; thermoplastic resin is used as the matrix, specifically polyethylene, polypropylene, polyamide, polyetherimide, polycarbonate, polyphenylene sulfide, polyether ether ketone or polylactic acid; the resin types used for the upper panel, the honeycomb core and the lower panel are the same.

[0010] (2) The present invention also provides a preparation device for a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, including a corrugated plate molding device, a honeycomb core ultrasonic connection device, a sandwich structure surface-core ultrasonic connection device and a conveying device; the corrugated plate molding device is used to make corrugated plates from continuous fiber reinforced thermoplastic resin unidirectional prepregs, the honeycomb core ultrasonic connection device is used to weld the corrugated plates into a honeycomb core, and the sandwich structure surface-core ultrasonic connection device is used to weld the upper panel, the honeycomb core and the lower panel to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure; the conveying device is used for automatic conveying between the devices.

[0011] Furthermore, the corrugated plate molding device includes a flat molding press, an upper corrugated mold and a lower corrugated mold; the upper corrugated mold is installed below the upper pressure plate of the flat molding press, and the lower corrugated mold is installed above the lower pressure plate of the flat molding press; a through groove with a triangular cross-section is provided on the bottom surface of the groove of the lower corrugated mold, and the length of the through groove is the same as the length of the groove in the lower corrugated mold.

[0012] Furthermore, grooves and protrusions are arranged at intervals on the welding surfaces of the upper corrugated mold and the lower corrugated mold, and the cross-sections of the grooves and protrusions are both in the structure of a semi-regular hexagon. Among them, the side length of the semi-regular hexagon is the same as the side length of the honeycomb hexagon, and the variation range is 2.75 mm to 20 mm.

[0013] Further, the cross-section of the through groove is an isosceles right triangle; the length of the right-angled side in the isosceles right triangle is set according to the thickness of the corrugated board, with a variation range of 0.5 to 2 mm; the number of through grooves is set according to the size of the honeycomb to be prepared. The number of through grooves in the bottom surface of each groove is 1 to 9, and the basis for the number selection is that the ratio of the total area of the triangular cross-section (mm 2 ) / the side length of the semi-regular hexagon (mm) is 0.20 to 0.25.

[0014] Further, the corrugated board molding device further includes a cooling water circulation pump and a water flow conduit. Cooling water channels are provided in both the upper pressing plate and the lower pressing plate of the flat molding press, and the cooling water channels are connected to the cooling water circulation pump through the water flow conduit. The cooling water circulation pump provides water flows at different flow rates to control the cooling rate of the molding press.

[0015] Further, the flat molding press is of an existing structure, specifically including a pressure controller, a temperature controller, a servo control motor, and upper and lower pressing plates. The upper and lower pressing plates are both flat pressing plates; a triangular cross-section groove is provided on the surface of the lower pressing plate, and the triangular cross-section groove penetrates the width direction of the lower pressing plate; among them, the mold temperature can be set in the range of 30 to 400 °C, the mold closing is controlled by the servo control motor, and the rate can be set in the range of 0 to 1000 mm / min, and the diameter of the cooling water channel is 8 to 14 mm.

[0016] Further, the corrugated board molding device further includes two groups of side baffles, and the two groups of side baffles are respectively installed on both sides of the corrugated lower mold through bolt fixing parts.

[0017] Further, the honeycomb core ultrasonic connection device includes a first ultrasonic vibration generator, a welding bottom mold, and a semi-regular hexagon welding head. The semi-regular hexagon welding head is fixedly installed below the first ultrasonic vibration generator, and the width of the semi-regular hexagon welding head is the same as the height of the honeycomb core; a number of hexagonal prism core hole combinations are provided on the side wall of the welding bottom mold, and each hexagonal prism core hole combination includes three hexagonal prism core holes. Among them, two hexagonal prism core holes are symmetrically distributed on both sides of the lower part of a hexagonal prism core hole; the distance between adjacent two hexagonal prism core hole combinations is the same as the side length of the cross-section of the hexagonal prism core hole; a hexagonal prism core rod is provided in the hexagonal prism core hole, and the length of the hexagonal prism core rod extending out of the hole is the same as the height of the honeycomb core, and the part of the hexagonal prism core rod extending out of the hole corresponds to the upper and lower positions of the semi-regular hexagon welding head.

[0018] Further, the width of the semi-regular hexagon welding head is 5 mm to 50 mm, and the bearing length of the hexagonal prism core rod is the same as the width of the semi-regular hexagon welding head; the semi-regular hexagon welding head is provided with 3 to 10 parallel vibration surfaces, and diamond-shaped grid patterns are provided on the vibration surfaces.

[0019] Further, the hexagonal mandrel is fixed inside the hexagonal core hole through fixing bolts; vertical threaded holes equal in number to the hexagonal core holes are provided at the top of the welding bottom die, and the vertical threaded holes communicate with the hexagonal core holes. By screwing the fixing bolts into the vertical threaded holes and applying pressure to the hexagonal mandrel, the fixing of the hexagonal mandrel is achieved.

[0020] Further, the honeycomb core ultrasonic connection device further includes quick clamps and silicone rubber stoppers; the quick clamps are fixedly installed at the top of the welding bottom die, and the silicone rubber stoppers are fixedly connected to the pressing crossbars of the quick clamps; the silicone rubber stoppers are distributed outside the hexagonal mandrels and block the outward movement of the honeycomb core during the honeycomb core welding process. After the honeycomb core welding is completed, the silicone rubber stoppers rotate upward under the drive of the quick clamps to take out the honeycomb core.

[0021] Further, through holes are provided on the quick clamps, and threaded connection holes corresponding to the positions of the through holes are provided at the top of the welding bottom die. By passing screws through the through holes and screwing them into the threaded connection holes, the fixation of the quick clamps to the welding bottom die is achieved.

[0022] Further, the sandwich structure surface core ultrasonic connection device includes a second ultrasonic vibration generator, a welding sandwich bottom die, a planar longitudinal vibration welding head, and a fixing device; the planar longitudinal vibration welding head is fixedly connected to the second ultrasonic vibration generator and is distributed below the second ultrasonic vibration generator, and the welding sandwich bottom die is arranged below the planar longitudinal vibration welding head; the fixing device is arranged on the welding sandwich bottom die and is used for fixing the sandwich structure during the welding process.

[0023] Further, the fixing device includes a welding clamping head and a silicone rubber chuck; the welding clamping head is fixedly connected to the welding sandwich bottom die; the silicone rubber chuck is installed on the welding clamping head and applies pressure to the sandwich structure under the drive of the welding clamping head.

[0024] Further, the welding clamping head is threadedly fixed to the welding sandwich bottom die, the welding clamping head is of a quick clamp structure, and the silicone rubber chuck is fixed at the clamping handle end of the quick clamp structure and restricts the degrees of freedom in all directions of the sandwich structure during the welding process under its drive.

[0025] Further, the welding surface of the planar longitudinal vibration welding head is provided with diamond-shaped patterns with a side length of 0.5 mm to increase the friction coefficient between the panel to be welded and the welding head during vibration.

[0026] (III) The present invention also provides a method for preparing a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, including the following steps:

[0027] S1. Prepare continuous fiber reinforced thermoplastic unidirectional prepreg by using thermoplastic resin film and continuous fiber reinforced composite material, where the fiber volume fraction is 55% - 65% and the resin mass fraction is 36% - 44%.

[0028] S2. Cut the prepreg prepared in step S1 according to the service characteristics of the honeycomb, stack it in the laying sequence, and then seal the edges at both ends of the stacked prepreg with polytetrafluoroethylene release tape; evenly spray high-temperature release agent on the surface of the corrugated lower mold to form a release agent layer, then lay and compact resin powder of the same resin type as that used to prepare the prepreg in the through groove to form the first energy guiding structure; lay the edge-sealed prepreg between the corrugated upper mold and the corrugated lower mold and perform molding to obtain a prepreg corrugated board.

[0029] S3. Cut the obtained corrugated board into narrow strips, and the width of the narrow strip is the same as the height of the honeycomb core; stack the narrow strips of the corrugated board with the side having the first energy guiding structure facing down between the hexagonal core rod and the semi-hexagonal welding head in sequence, push and pull the quick clamp and start the first ultrasonic vibration generator, and the semi-hexagonal welding head presses down to complete the ultrasonic connection of the nodes of the honeycomb core; move other nodes to be connected of the corrugated board to the welding area and repeat the above process to obtain the honeycomb core.

[0030] S4. Cut the prepreg prepared in step S1 according to the service characteristics of the honeycomb and stack it in the laying sequence; lay and compact resin powder of the same resin type as that used to prepare the prepreg in the triangular cross-section groove on the surface of the lower pressing plate to form the second energy guiding structure, and then lay the cut and stacked prepreg between the upper and lower pressing plates of the flat die press for molding to obtain the upper panel and the lower panel.

[0031] S5. Cut the honeycomb core obtained in S3, and cut the upper panel and the lower panel prepared in step S4 to the same size as the honeycomb core; place the side of the upper panel having the second energy guiding structure facing down on the upper end face of the honeycomb core, align them and place them in the bottom mold of the welding sandwich, push and pull the welding clamping head to complete the structural fixation and start the second ultrasonic vibration generator, and the flat longitudinal vibration welding head presses down to complete the connection between the upper panel and the honeycomb core; flip the welded structure by 180° and repeat the above process to complete the connection between the lower panel and the honeycomb core to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure.

[0032] Furthermore, the molding process of the prepreg corrugated board is the same as that of the upper and lower panels; the molding process is as follows: Set the temperature target to the forming processing temperature window of the thermoplastic resin. The preferred processing window is 95% Tm (resin melting point temperature, °C), and adjust appropriately according to the reinforcing material to ensure that the material has a low storage modulus while avoiding large fluidity of the resin. When the internal real-time temperature reaches the forming processing temperature window of the resin, set the downward pressure rate of the corrugated upper die / upper pressing plate to 1 mm / min, and press the closing die switch. After the die is completely closed, set the temperature target to the molding processing temperature window of the thermoplastic resin. The preferred processing window is 102% - 105% Tm (resin melting point temperature, °C). After the temperature reaches the set value, maintain the molding pressure and temperature for 5 - 25 min to ensure that the thermoplastic resin has appropriate fluidity and fully infiltrates the mold cavity. Turn off the heating switch, turn on the cooling water circulation pump switch, set the cooling water flow rate to 5 L - 12 L / min, control the cooling rate to 10 - 60 °C / min. When the temperature drops below the glass transition temperature (Tg) of the thermoplastic resin, turn off the pressure switch. After cooling to room temperature, take out the corrugated board specimen / upper panel and lower panel.

[0033] Advantages of the present invention:

[0034] The present invention proposes a preparation method for a continuous fiber-reinforced thermoplastic composite honeycomb sandwich structure that meets the different application requirements in the fields of aerospace, automotive, and rail transit, etc., and realizes the introduction of thermoplastic composites for the preparation of honeycomb cores. By introducing a local heat source through ultrasonic welding, problems such as surface collapse, poor precision, and high energy consumption in the overall bonding preparation of thermoplastic corrugated boards for honeycombs are solved. The prepared honeycomb has excellent mechanical properties such as recyclability, high toughness, and impact resistance compared with thermosetting composites. Compared with the prior art, the present invention has the following specific advantages:

[0035] (1) Compared with metal honeycomb cores, the specific stiffness and specific strength of the material are significantly improved, and the coefficient of thermal expansion is reduced, having the advantages of integrated structural function designability and lightweight.

[0036] (2) Compared with thermosetting composite honeycomb cores, there is no need for a 2 - 3-hour curing time of thermosetting materials, and the preparation efficiency is greatly improved. In addition, because there are no small molecules of cured released gases, the material has a high density, and has excellent anti-hygrothermal expansion characteristics and can be recycled repeatedly.

[0037] (3) Compared with the method of directly bonding thermoplastic corrugated boards in an oven to prepare honeycombs or sandwich structures, the ultrasonic welding time is only 0.1 - 5 s, and the pressure and temperature are highly controllable, with high preparation efficiency and honeycomb size accuracy. At the same time, it avoids the uneven material properties caused by softening and crystallization behaviors in non-connected areas due to temperature rise, has high energy utilization efficiency, and effectively reduces carbon emissions during the preparation process. Description of the Drawings:

[0038] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0039] Figure 2 It is a schematic diagram of the structure of the corrugated board molding device of the present invention;

[0040] Figure 3 It is a schematic diagram of the structures of the upper corrugated mold and the lower corrugated mold in the corrugated board molding device of the present invention;

[0041] Figure 4 It is a schematic diagram of the honeycomb core ultrasonic connection device of the present invention;

[0042] Figure 5 It is a schematic diagram of the semi - hexagonal welding head for ultrasonic welding of the honeycomb core of the present invention;

[0043] Figure 6 It is a three - dimensional schematic diagram of the honeycomb core ultrasonic connection device of the present invention;

[0044] Figure 7 It is a schematic diagram of the ultrasonic connection device for the surface core of the sandwich structure of the present invention;

[0045] Figure 8 It is a schematic diagram of the stacking of corrugated boards during the ultrasonic welding process of the honeycomb core of the present invention;

[0046] The reference signs in the drawings are:

[0047] 1. Corrugated board molding device; 2. Honeycomb core ultrasonic connection device; 3. Ultrasonic connection device for the surface core of the sandwich structure; 4. Conveyor device; 5. Flat die press; 6. Upper corrugated mold; 7. Lower corrugated mold; 8. Cooling water circulation pump; 9. Water flow conduit; 10. Cooling water channel; 11. First ultrasonic vibration generator; 12. Welding bottom mold; 13. Second ultrasonic vibration generator; 14. Semi - hexagonal welding head; 15. Hexagonal prism core rod; 16. Hexagonal prism core hole; 17. Threaded connection hole; 18. Screw; 19. Welding sandwich bottom mold; 20. Welding clamping head; 21. Plane longitudinal vibration welding head; 22. Pressure controller; 23. Temperature controller; 24. Servo control motor; 25. Side baffle; 26. Through groove; 27. Vibration surface; 28. Vertical threaded hole; 29. Fixed bolt; 30. Quick clamp; 31. Silicone rubber block; 32. Pressing bar crossbar; 33. Handle; 34. Silicone rubber chuck; 35. First energy guiding structure; 36. Upper panel; 37. Honeycomb core; 38. Second energy guiding structure; 39. Lower panel. Detailed Embodiments:

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] I. The present invention provides a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure

[0050] The structure of the present invention includes an upper panel, a honeycomb core, and a lower panel; the honeycomb core is formed by welding corrugated plates made of continuous fiber reinforced thermoplastic resin unidirectional prepregs; both the upper panel and the lower panel are molded from continuous fiber reinforced thermoplastic resin unidirectional prepregs; the density of the honeycomb core is generally 100 kg / m 3 ~230 kg / m 3 .

[0051] Among them, in the continuous fiber reinforced thermoplastic resin unidirectional prepreg, the continuous fiber is the reinforcement, specifically one or more of carbon fiber, glass fiber, aramid fiber, quartz fiber, basalt fiber, and natural fiber, and the continuous fiber can have a layup adjustable in any direction from 0 to 360° on the honeycomb wall; the thermoplastic resin is the matrix, specifically it can be polyethylene, polypropylene, polyamide, polyetherimide, polycarbonate, polyphenylene sulfide, polyether ether ketone, or polylactic acid. Polyether ether ketone or polyphenylene sulfide is preferably used in the high-temperature environment of aerospace, polycarbonate is preferably used for moisture-resistant precision parts, and polyethylene, polypropylene, or polyamide is preferably used in the automotive industry and rail transit.

[0052] The resin types used for the upper panel, honeycomb core, and lower panel are the same. The side length of the cross-section of the honeycomb core is 2.75 mm to 20 mm, the thickness of the honeycomb wall is 0.14 mm to 2 mm, and the height of the honeycomb is 5 mm to 50 mm.

[0053] II. The present invention provides a preparation device for a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure

[0054] Referring to Figures 1 - 8 , the device of the present invention includes a corrugated plate molding device 1, a honeycomb core ultrasonic connection device 2, a sandwich structure surface-core ultrasonic connection device 3, and a conveying device 4; the corrugated plate molding device 1 is used to make corrugated plates from continuous fiber reinforced thermoplastic resin unidirectional prepregs, the honeycomb core ultrasonic connection device 2 is used to weld the corrugated plates into a honeycomb core, the sandwich structure surface-core ultrasonic connection device 3 is used to weld the upper panel, honeycomb core, and lower panel to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure; the conveying device 4 is used for automatic conveying between the devices.

[0055] The structures of the corrugated board molding device 1, the honeycomb core ultrasonic connection device 2, and the sandwich structure surface-core ultrasonic connection device 3 are described separately as follows:

[0056] (I) Corrugated board molding device

[0057] Referring to Figures 1 - 2 , the corrugated board molding device 1 includes a flat die press 5, a corrugated upper die 6, and a corrugated lower die 7.

[0058] Among them, the flat die press 5 is a conventional structure, specifically including a pressure controller 22, a temperature controller 23, a servo control motor 24, and upper and lower pressure plates. The upper and lower pressure plates are both flat pressure plates. Among them, the settable range of the molding temperature is 30 - 400 °C, and the mold closing is controlled by the servo control motor 24, and the rate can be set in the range of 0 - 1000 mm / min. For the corrugated board molding device 1 of the present invention, based on the flat die press 5, the following modifications are made:

[0059] 1) An isosceles right triangle cross-section groove is opened on the surface of the lower pressure plate, and the isosceles right triangle cross-section groove penetrates the width direction of the lower pressure plate.

[0060] 2) The corrugated upper die 6 is detachably installed below the upper pressure plate of the flat die press 5, and the corrugated lower die 7 is detachably installed above the lower pressure plate of the flat die press 5, and the upper pressure plate and the corrugated upper die 6 are thermally conductive, and the lower pressure plate and the corrugated lower die 7 are thermally conductive; the welding surfaces of the corrugated upper die 6 and the corrugated lower die 7 are both provided with grooves and protrusions arranged at intervals, and the cross-sections of the grooves and protrusions are both semi-regular hexagon structures. Referring to Figure 3 , among them, the side length of the semi-regular hexagon is the same as the side length of the honeycomb hexagon, and the variation range is 2.75 mm - 20 mm.

[0061] 3) A through groove 26 with a triangular cross-section is opened on the bottom surface of the groove of the corrugated lower die 7. Referring to Figure 3 , the length of the through groove 26 is the same as the length of the groove in the corrugated lower die 7. The cross-section of the through groove 26 is an isosceles right triangle, and the length of the right side of the isosceles right triangle is set according to the thickness of the corrugated board, and the variation range is 0.5 - 2 mm; the number of the through grooves 26 is set according to the size of the honeycomb to be prepared, and the number of the through grooves 26 in each groove bottom surface is 1 - 9, and the selection basis of the number is that the ratio of the total area of the triangular cross-section (mm 2 ) / the side length of the semi-regular hexagon (mm) is 0.20 - 0.25.

[0062] 4) Cooling water channels 10 with a diameter of 8 - 14 mm are provided in the upper platen and lower platen of the flat die press 5, and a cooling water circulation pump 8 and a water flow conduit 9 are correspondingly provided. The cooling water flow rate is 5 L - 12 L / min, and the die pressing cooling rate varies in the range of 10 °C / min - 60 °C / min. Refer to Figure 2 . The cooling water channels 10 are connected to the cooling water circulation pump 8 through the water flow conduit 9. The cooling water circulation pump 8 provides water flows at different flow rates to control the cooling rate of the die press, enabling rapid cooling after die pressing and improving work efficiency.

[0063] 5) Two groups of side baffles are added. The two groups of side baffles 25 are respectively installed on both sides of the corrugated lower die 7 through bolt fasteners. Refer to Figure 3 .

[0064] (2) Honeycomb core ultrasonic connection device

[0065] Refer to Figures 4 - 6 , the honeycomb core ultrasonic connection device 2 includes a first ultrasonic vibration generator 11 (commercially available, wherein the adjustable range of the amplitude is 10 - 30 μm, the frequency can be switched among 15 kHz, 20 kHz, and 35 kHz according to the thermoplastic resin material, the pressure can be switched among 0.1 - 0.8 MPa according to the thermoplastic resin material, the welding power is 3000 W, and the ultrasonic generation mode can be set according to time, power, and displacement), a welding bottom die 12, and a semi - hexagonal welding head 14 (the material is aluminum alloy or titanium alloy). The semi - hexagonal welding head 14 is fixedly installed under the first ultrasonic vibration generator 11 by threads, and the width of the semi - hexagonal welding head 14 is the same as the height of the honeycomb core. A number of hexagonal prism core hole combinations are provided on the side wall of the welding bottom die 12. Each hexagonal prism core hole combination includes three hexagonal prism core holes 16. Among them, two hexagonal prism core holes 16 are symmetrically distributed on both sides of the lower part of a hexagonal prism core hole 16; the distance between adjacent two hexagonal prism core hole combinations is the same as the side length of the cross - section of the hexagonal prism core hole 16; a hexagonal prism core rod 15 is provided in the hexagonal prism core hole 16, and the length of the hexagonal prism core rod 15 extending out of the hole is the same as the height of the honeycomb core. The part of the hexagonal prism core rod 15 extending out of the hole corresponds to the upper and lower positions of the semi - hexagonal welding head 14.

[0066] The width of the semi - hexagonal welding head 14 is 5 mm - 50 mm, and the bearing length of the hexagonal prism core rod 15 is the same as the width of the semi - hexagonal welding head 14; the semi - hexagonal welding head 14 is provided with 3 - 10 parallel vibration surfaces 27, and diamond - shaped patterns are provided on the vibration surfaces to increase the friction coefficient between the panel to be welded and the welding head during vibration. Refer to Figure 5 .

[0067] The hexagonal mandrel 15 is fixed inside the hexagonal core hole 16 by fixing bolts 29; on the top of the welding bottom die 12, there are vertical threaded holes 28 with the same number as the hexagonal core holes 16. The vertical threaded holes 28 communicate with the hexagonal core holes 16. By screwing the fixing bolts 29 into the vertical threaded holes 28 and applying pressure to the hexagonal mandrel 15, the fixing of the hexagonal mandrel 15 is achieved. Refer to Figure 6 .

[0068] A limiting device is also provided to prevent the honeycomb core from moving outwards during the welding process. Specifically, refer to Figure 6 , the limiting device includes a quick clamp 30 and a silicone rubber stopper 31. There is a through hole on the quick clamp 30, and on the top of the welding bottom die 12, there is a threaded connection hole 17 corresponding to the position of the through hole. By passing a screw 18 through the through hole and screwing it into the threaded connection hole 17, the quick clamp 30 is fixed to the welding bottom die 12; the silicone rubber stopper 31 is rigidly connected to the pressing cross bar 32 of the quick clamp 30 by a thread. The silicone rubber stoppers 31 are distributed outside the hexagonal mandrel 15 to block its outward movement during the honeycomb core welding process, ensuring the normal constraint during the honeycomb welding process. When the honeycomb core welding is completed, the silicone rubber stopper 31 rotates upwards (with an adjustable angle of 90°) driven by the quick clamp 30 to take out the honeycomb core. The quick clamp 30 is a commercially available structure, and its structure will not be described in detail in this article.

[0069] (3) Sandwich structure surface-core ultrasonic connection device

[0070] Refer to Figure 7 , the sandwich structure surface-core ultrasonic connection device 3 includes a second ultrasonic vibration generator 13 (commercially available), a welding sandwich bottom die 19, a planar longitudinal vibration welding head 21, and a fixing device; the planar longitudinal vibration welding head 21 is fixedly connected to the second ultrasonic vibration generator 13 by a thread and is distributed below the second ultrasonic vibration generator 13. The welding sandwich bottom die 19 is arranged below the planar longitudinal vibration welding head 21; the fixing device is arranged on the welding sandwich bottom die 19 for fixing the sandwich structure during the welding process.

[0071] The fixing device includes a welding clamping head 20 and a silicone rubber chuck 34. The welding clamping head 20 is fixedly connected to the welding sandwich bottom die 19 by a thread, and the silicone rubber chuck 34 is installed on the welding clamping head 20 to apply pressure to the sandwich structure driven by the welding clamping head 20. Among them, the welding clamping head 20 is a quick clamp structure (commercially available), and the silicone rubber chuck 34 is fixed at the clamping handle end of the quick clamp structure to restrict the degrees of freedom of the sandwich structure in all directions during the welding process.

[0072] The welding surface of the planar longitudinal vibration welding head 21 is provided with diamond-shaped patterns with a side length of 0.5 mm, which can increase the friction coefficient between the panel to be welded and the welding head during vibration.

[0073] 3. The present invention provides a method for preparing a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure

[0074] The method comprises the following steps:

[0075] Step 1: Preparation of prepreg:

[0076] A continuous fiber reinforced thermoplastic resin unidirectional prepreg is prepared by using a thermoplastic resin film and a continuous fiber reinforcement composite material, wherein the fiber volume fraction is 55% to 65% and the resin mass fraction is 36% to 44%;

[0077] Step 2: Cutting of prepreg:

[0078] The prepreg obtained in step one is cut at different laying angles according to the honeycomb service characteristics, and is cut to have the same width as the corrugated lower mold 7 and a length that is 4 / 3 of the length of the corrugated lower mold 7; for in-plane shear load-bearing environment, ±45° laying is preferred; for bending load-bearing environment and out-of-plane shear load-bearing environment, 0° laying along the bending direction is preferred; for out-of-plane compression load-bearing environment, 90° laying is preferred; for the superposition environment of the above-mentioned load-bearing characteristics, layer superposition can be carried out in a targeted manner according to needs.

[0079] According to the load-bearing environment characteristics of the honeycomb, the preferred ply is shown in Table 1.

[0080] Table 1 - Honeycomb core layer selection

[0081] Main load form Honeycomb core ply selection In-plane shear ±45° Bending, out-of-plane shear 0° Out-of-plane compression 90°

[0082] Step 3: Preparation of prepreg corrugated board:

[0083] After the prepreg prepared in step 2 is cut, it is stacked in a layering order, and then both ends of the stacked prepreg are sealed with polytetrafluoroethylene release tape; a high-temperature resistant release agent is evenly sprayed on the surface of the corrugated lower mold 7 to form a 20μm release agent layer, and then a resin powder consistent with the resin type used to prepare the prepreg is laid in the through groove 26 and compacted to form a first energy guiding structure 35, and the powder diameter is preferably 13.0μm (1000 mesh) to 29.9μm (500 mesh); the edge-sealed prepreg is laid between the corrugated upper mold 6 and the corrugated lower mold 7, and molded to obtain a prepreg corrugated board.

[0084] The molding process is as follows: Set the temperature target to the forming processing temperature window of the thermoplastic resin. The preferred processing window is 95% Tm (resin melting point temperature, °C), and adjust it appropriately according to the reinforcing material to ensure that the material has a low storage modulus while avoiding excessive fluidity of the resin. The specific processing windows for honeycomb molding of different thermoplastic resins are shown in Table 2.

[0085] Table 2 Molding Processing Temperatures of Corrugated Sheets of Typical Materials

[0086]

[0087]

[0088] When the internal real-time temperature reaches the forming processing temperature window of the resin, set the downward pressure rate of the corrugated upper mold 6 to 1 mm / min, and press the closing mold switch; after the mold is fully closed, set the temperature target to the molding processing temperature window of the thermoplastic resin. The preferred processing window is 102% - 105% Tm (resin melting point temperature, °C); after the temperature reaches the set value, maintain the molding pressure and temperature for 5 - 25 min to ensure that the thermoplastic resin has appropriate fluidity and fully infiltrates the mold cavity; turn off the heating switch, turn on the switch of the cooling water circulation pump 8, set the cooling water flow rate to 5 L - 12 L / min, and control the cooling rate to 10 - 60 °C / min. For crystalline thermoplastic resins such as polypropylene and polyethylene, the preferred cooling rate is 60 °C / min to optimize the preparation efficiency of the corrugated sheet; for semi-crystalline thermoplastic resins such as polyphenylene sulfide and polyether ether ketone, the preferred cooling rate is 10 °C / min. When the temperature drops below the glass transition temperature (Tg) of the thermoplastic resin, turn off the pressure switch; after cooling to room temperature, take out the corrugated sheet specimen.

[0089] In addition, for the resin powder laid in the through groove 26, for resin systems with a melting point temperature less than 250 °C, the laid powder is pure resin powder; for resin systems with a melting point temperature range of 250 °C - 400 °C, the laid powder is a mixture of nano-reinforcing particles and pure resin powder. Preferably, the nano-reinforcing particles are multi-walled carbon nanotubes or nano-silica.

[0090] Step Four: Preparation of the honeycomb core:

[0091] The corrugated board obtained by preparation is cut into narrow strips by water jet cutting. The width of the narrow strip is the same as the height of the honeycomb core, and is controlled within the range of 5 mm to 50 mm. The side of the corrugated board narrow strip with the first energy guiding structure 35 is placed downward and stacked in turn between the hexagonal core rod 15 and the semi-hexagonal welding head 14. Set the process parameters of the amplitude, pressure, vibration time, delay time, power, and welding head pressing rate of the first ultrasonic vibration generator 11. Push and pull the quick clamp 30 and start the first ultrasonic vibration generator 11. The semi-hexagonal welding head 14 presses down to complete the ultrasonic connection of the nodes of the honeycomb core. Move other nodes of the corrugated board to be connected to the welding area, and repeat the above process to obtain the honeycomb core 37.

[0092] The specific ultrasonic connection process parameters for different thermoplastic resins of the honeycomb core are shown in Table 3.

[0093] Table 3 Ultrasonic Welding Parameters of Corrugated Boards of Typical Materials

[0094]

[0095] Step Five: Preparation of the upper panel and the lower panel:

[0096] The prepreg prepared in Step One is cut according to the service characteristics of the honeycomb, and stacked in the laying sequence. Resin powder of the same type as the resin of the prepreg to be prepared is laid in the isosceles right triangle cross-section groove and compacted to form the second energy guiding structure 38. Subsequently, the cut and stacked prepreg is laid between the upper and lower pressing plates of the flat die press for die pressing (the upper and lower pressing plate die pressing process is the same as the corrugated board die pressing process) to obtain the upper panel 36 and the lower panel 39.

[0097] Step Six: Preparation of the continuous fiber reinforced thermoplastic composite honeycomb sandwich structure:

[0098] The honeycomb core obtained in Step Four is cut to the required length and width dimensions of the sandwich structure. The upper panel 36 and the lower panel 39 prepared in Step S4 are cut to the same size as the honeycomb core 37. The side of the upper panel 36 with the second energy guiding structure 38 is placed downward on the upper end face of the honeycomb core 37. After alignment, it is placed in the welding sandwich bottom die 19. Set the process parameters of the amplitude, pressure, vibration time, delay time, power, frequency, and welding head pressing rate of the second ultrasonic vibration generator 13. Push and pull the welding clamping head 20 to complete the structure fixation and start the second ultrasonic vibration generator 13. The planar longitudinal vibration welding head 21 presses down to complete the local connection of the honeycomb sandwich structure. Move the welding sandwich bottom die 19 to complete the connection between the upper panel 36 and the honeycomb core 37. Flip the welded structure 180°, and repeat the above process to complete the connection between the lower panel 39 and the honeycomb core 37 to obtain the continuous fiber reinforced thermoplastic composite honeycomb sandwich structure. In the present invention, the function of the second energy guiding structure 38 is to complete the preparation of the honeycomb sandwich structure through the wall-climbing effect after the melting of the guiding structure resin.

[0099] Example 1

[0100] The present embodiment provides a continuous carbon fiber reinforced polyetheretherketone composite honeycomb sandwich structure for an aircraft rudder, and the preparation method thereof is as follows:

[0101] Step 1: prepare unidirectional prepreg by compounding polyetheretherketone resin film and T800 carbon fiber reinforcement, with the fiber volume fraction controlled at 65% and the resin mass content controlled at 36%.

[0102] Step 2: Cut the continuous fiber thermoplastic prepreg obtained in step 1 at different laying angles according to the honeycomb service characteristics, cutting it to the same width as the corrugated lower mold 7 and 4 / 3 of the length of the corrugated lower mold 7; for bending and out-of-plane compression load-bearing environments, 0° / 90° orthogonal laying is preferred.

[0103] Step three, evenly spray a high-temperature resistant release agent on the surface of the corrugated lower mold 7 to form a 20μm release agent layer, and then lay the same polyetheretherketone resin powder and multi-walled carbon nanotubes used to prepare the prepreg in step one in the through groove 26 with an isosceles right triangle cross-section and compact them. The powder diameter is preferably 13.0μm (1000 mesh); seal the ends of the prepreg stacked in the order of plying with polytetrafluoroethylene release tape, lay it between the corrugated upper mold 6 and the corrugated lower mold 7, and place it as a whole inside the flat plate molding machine 5, and set the temperature target to 380°C.

[0104] Step 4: When the real-time temperature inside the flat-bed molding machine 5 reaches the molding processing temperature window of the resin, set the flat-bed pressing rate to 1 mm / min and press the mold closing switch; after the mold is completely closed, set the temperature target to the molding processing temperature window of the thermoplastic resin, and the preferred processing window is 390°C; after the temperature reaches the set value, maintain the molding pressure and temperature for 25 minutes; turn off the heating switch, turn on the cooling water circulation pump 8 switch, set the cooling water flow rate to 12 L / min, control the cooling rate to 60°C / min, and when the temperature drops below 143°C, turn off the pressure switch; take out the corrugated board sample after cooling to room temperature.

[0105] Step five, the prepared corrugated board is cut into 30mm narrow strips required for the honeycomb core by water jet cutting; the narrow strips with the side surface of the first energy guiding structure 35 facing downward are stacked in sequence between the hexagonal core rod 15 of the welding bottom mold 12 and the semi-hexagonal welding head 14, the amplitude of the first ultrasonic vibration generator 11 is set to 20μm, the pressure is 0.5MPa, the vibration time is 2500ms, the delay time is 5s, and the power is 1800W, the quick clamp 30 is pushed and pulled and the generator is started, and the welding head is pressed down to complete the ultrasonic connection of the nodes of the honeycomb core; the other nodes to be connected of the corrugated board are moved to the welding area, and the above process is repeated to complete the manufacture of honeycomb cores of predetermined different sizes.

[0106] Step 6: Cut the honeycomb core obtained in Step 5 to 500×500×25 mm; cut the prepreg obtained in Step 1 to the same length and width dimensions, stack it according to the layup in a flat die with an isosceles right triangle cross-sectional groove, heat it to 385 °C, and then lay the resin powder in the isosceles right triangle cross-sectional groove according to the same process as in Step 3. After molding, a continuous fiber-reinforced thermoplastic composite panel with a second energy guiding structure 38 on one side is obtained. Place the obtained panel on the upper end face of the honeycomb core 37, align it, and place it in the welding sandwich bottom die 19; set the amplitude of the second ultrasonic vibration generator 13 to 20 μm, the pressure to 0.5 MPa, the vibration time to 2500 ms, the delay time to 5 s, and the power to 1800 W. Push and pull the welding clamping head 20 to complete the structural fixation and start the generator. Press down the welding head to complete the local connection of the honeycomb sandwich structure. Move the welding sandwich bottom die 19 and repeat the above process to complete the connection of one side panel; after reversing the structure by 180°, place the lower panel on the upper end face of the honeycomb core and repeat the above process to complete the connection of the other side panel, obtaining a continuous fiber-reinforced thermoplastic composite honeycomb sandwich structure.

[0107] Example 2

[0108] A continuous glass fiber-reinforced polypropylene composite honeycomb sandwich structure for train skins is prepared as follows:

[0109] Step 1: Prepare a unidirectional prepreg by compounding a polypropylene resin film with an E-class glass fiber reinforcement, controlling the fiber volume fraction at 50% and the resin mass content at 45%.

[0110] Step 2: Cut the continuous fiber thermoplastic prepreg obtained in Step 1 at different layup angles according to the honeycomb service characteristics, cut it to the same width as the corrugated lower die 7, and the length is 4 / 3 of the length of the corrugated lower die 7; for in-plane shear and compression bearing environments, a 0° / ±45° / 90° quasi-isotropic layup is preferably used.

[0111] Step 3: Uniformly spray a high-temperature release agent on the surface of the corrugated lower die 7 to form a 20-μm release agent layer, and then lay and compact the same polypropylene resin powder as that used in the prepreg prepared in Step 1 in the through groove 26 with an isosceles right triangle cross-section. The powder diameter is preferably 29.9 μm (500 mesh); seal the two ends of the prepreg stacked in the layup order with polytetrafluoroethylene release tape, lay it between the corrugated upper die 6 and the corrugated lower die 7, and place the whole in the flat die press 5, and set the temperature target to 170 °C.

[0112] Step 4: When the flat die press 5 feeds back that the internal real-time temperature reaches the forming and processing temperature window of the resin, set the flat die downward rate to 1 mm / min and press the mold closing switch; after the mold is fully closed, set the temperature target to the molding processing temperature window of the thermoplastic resin, and the preferred processing window is 185 °C; after the temperature reaches the set value, maintain the molding pressure and temperature for 5 min; turn off the heating switch, turn on the switch of the cooling water circulation pump 8, set the cooling water flow rate to 5 L / min, control the cooling rate to decrease by 10 °C / min, and turn off the pressure switch when the temperature drops below 70 °C; take out the corrugated board specimen after cooling to room temperature.

[0113] Step 5: Cut the prepared corrugated board into 10-mm-wide strips required for the honeycomb core by water jet cutting; stack the side of the strip with the first energy guiding structure 35 facing down in turn between the hexagonal core rod 15 of the welding bottom die 12 and the semi-hexagonal welding head 14, set the amplitude of the first ultrasonic vibration generator 11 to 15 μm, the pressure to 0.2 MPa, the vibration time to 300 ms, the delay time to 1 s, and the power to 800 W, push and pull the quick clamp 30 and start the generator, and the welding head presses down to complete the ultrasonic connection of the nodes of the honeycomb core; move other nodes to be connected of the corrugated board to the welding area, and repeat the above process to complete the manufacture of the honeycomb core.

[0114] Step 6: Cut the honeycomb core obtained in Step 5 to 300×300×25 mm; cut the prepreg obtained in Step 1 to the same length and width dimensions, stack it according to the layup in the flat die press 5 and heat it up to the molding processing temperature window, and prepare the upper panel 36 and the lower panel 39 of the sandwich structure by using the same molding process parameters as in Step 4; place the obtained panel on the upper end face of the honeycomb core 37, align it and place it in the welding sandwich bottom die 19; set the amplitude of the second ultrasonic vibration generator 13 to 15 μm, the pressure to 0.2 MPa, the vibration time to 300 ms, the delay time to 1 s, and the power to 800 W, push and pull the welding clamping head 20 to complete the structure fixation and start the generator, and the welding head presses down to complete the local connection of the honeycomb sandwich structure, move the welding sandwich bottom die 19, and repeat the above process to complete the connection of one side panel; reverse the structure by 180° and place the other panel on the upper end face of the honeycomb core, and repeat the above process to complete the connection of the other side panel to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure.

[0115] Example 3 - Performance Test

[0116] Test the mechanical properties of the continuous fiber reinforced thermoplastic composite honeycomb sandwich structures prepared in Example 1 and Example 2, and compare them with ordinary metal honeycomb cores. The results are shown in Table 4.

[0117] Table 4 Test Results of the Honeycomb Performance of the Examples

[0118] Technical indicators Example 1 Example 2 Traditional aluminum honeycomb <![CDATA[Cell density / kg / m 3 > 133.90 100.68 54.29 Flat compression strength / MPa 11.73 4.81 1.19 Flat compression specific strength / N·m / kg 87602.08 47775.16 22100.18

[0119] As can be seen from Table 4, the mechanical properties of the honeycomb sandwich structure prepared in the embodiments of the present invention are significantly better than those of traditional aluminum honeycombs.

[0120] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A continuous fiber reinforced thermoplastic composite honeycomb sandwich structure, characterized in that it includes an upper panel, a honeycomb core and a lower panel; the honeycomb core is formed by welding corrugated plates made of continuous fiber reinforced thermoplastic resin unidirectional prepregs; both the upper panel and the lower panel are molded from continuous fiber reinforced thermoplastic resin unidirectional prepregs; the resin types used for the upper panel, the honeycomb core and the lower panel are the same; the preparation device for the continuous fiber reinforced thermoplastic composite honeycomb sandwich structure includes a corrugated plate molding device (1), a honeycomb core ultrasonic connection device (2), a sandwich structure surface-core ultrasonic connection device (3) and a conveying device (4); the corrugated plate molding device (1) includes a flat plate molding press (5), a corrugated upper mold (6) and a corrugated lower mold (7); the welding surfaces of the corrugated upper mold (6) and the corrugated lower mold (7) are provided with grooves and protrusions arranged at intervals, and the cross-sections of the grooves and protrusions are both semi-regular hexagon structures; a through groove (26) with a triangular cross-section is provided at the bottom of the groove of the corrugated lower mold (7), and resin powder consistent with the resin type for preparing the prepreg is laid and compacted in the through groove (26) to form a first energy guiding structure (35); resin powder consistent with the resin type for preparing the prepreg is laid and compacted in the triangular cross-section groove on the surface of the lower pressing plate for molding the upper panel and the lower panel to form a second energy guiding structure (38); the honeycomb core ultrasonic connection device (2) includes a first ultrasonic vibration generator (11), a welding bottom mold (12) and a semi-hexagonal welding head (14), the semi-hexagonal welding head (14) is fixedly installed below the first ultrasonic vibration generator (11), and the width of the semi-hexagonal welding head (14) is consistent with the height of the honeycomb core; a number of hexagonal prism core hole combinations are provided on the side wall of the welding bottom mold (12), and each hexagonal prism core hole combination includes three hexagonal prism core holes (16), wherein, two hexagonal prism core holes (16) are symmetrically distributed on both sides of the lower part of a hexagonal prism core hole (16); the distance between adjacent two hexagonal prism core hole combinations is consistent with the side length of the cross-section of the hexagonal prism core hole (16); a hexagonal prism core rod (15) is arranged in the hexagonal prism core hole (16), the length of the hexagonal prism core rod (15) extending out of the hole is consistent with the height of the honeycomb core, and the part of the hexagonal prism core rod (15) extending out of the hole corresponds to the upper and lower positions of the semi-hexagonal welding head (14).

2. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that the corrugated plate molding device (1) is used to make corrugated plates from continuous fiber reinforced thermoplastic resin unidirectional prepregs, the honeycomb core ultrasonic connection device (2) is used to weld the corrugated plates into a honeycomb core, the sandwich structure surface-core ultrasonic connection device (3) is used to hot-press and cure the upper panel, the honeycomb core and the lower panel to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure; the conveying device (4) is used for automatic conveying between the devices.

3. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that The corrugated upper die (6) is detachably installed below the upper platen of the flat die press (5), and the corrugated lower die (7) is detachably installed above the lower platen of the flat die press (5); The length of the through groove (26) is the same as the length of the groove in the corrugated lower die (7).

4. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that The corrugated board die pressing device (1) further includes a cooling device, the cooling device includes a cooling water circulation pump (8) and a water flow conduit (9), cooling water channels (10) are arranged in both the upper platen and the lower platen of the flat die press (5), and the cooling water channels (10) are connected to the cooling water circulation pump (8) through the water flow conduit (9).

5. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that The hexagonal prism mandrel (15) is fixed inside the hexagonal prism core hole (16) by fixing bolts (29); Vertical threaded holes (28) with the same number as the hexagonal prism core holes (16) are arranged at the top of the welding bottom die (12), the vertical threaded holes (28) communicate with the hexagonal prism core holes (16), and by screwing the fixing bolts (29) into the vertical threaded holes (28) and generating pressure on the hexagonal prism mandrel (15), the fixing of the hexagonal prism mandrel (15) is achieved.

6. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that The honeycomb core ultrasonic connection device (2) further includes quick clamps (30) and silicone rubber stoppers (31); The quick clamps (30) are fixedly installed on the top of the welding bottom die (12), and the silicone rubber stoppers (31) are fixedly connected to the pressing bar crossbar (32) of the quick clamps (30); The silicone rubber stoppers (31) are distributed outside the hexagonal prism mandrel (15) and block its outward movement during the welding of the honeycomb core. After the welding of the honeycomb core is completed, the silicone rubber stoppers (31) rotate upward under the drive of the quick clamps (30) to take out the honeycomb core.

7. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that The sandwich structure surface core ultrasonic connection device (3) includes a second ultrasonic vibration generator (13), a welding sandwich bottom die (19), a planar longitudinal vibration welding head (21) and a fixing device; The planar longitudinal vibration welding head (21) is fixedly connected to the second ultrasonic vibration generator (13) and is distributed below the second ultrasonic vibration generator (13), and the welding sandwich bottom die (19) is arranged below the planar longitudinal vibration welding head (21); The fixing device is arranged on the welding sandwich bottom die (19) and is used for fixing the sandwich structure during the welding process.

8. The continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 7, characterized in that The fixing device includes a welding chuck (20) and a silicone rubber chuck (34). The welding chuck (20) is fixedly connected to the bottom die (19) of the welding sandwich layer. The silicone rubber chuck (34) is installed on the welding chuck (20), and under the drive of the welding chuck (20), it generates pressure on the sandwich structure to fix it.

9. The preparation method of the continuous fiber reinforced thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that, It includes the following steps: S1. Prepare a continuous fiber reinforced thermoplastic resin unidirectional prepreg by using a thermoplastic resin film and a continuous fiber reinforced composite material. S2. Cut and stack the prepreg prepared in step S1 according to the service characteristics of the honeycomb. Then, seal the edges of the stacked prepreg with polytetrafluoroethylene release tape at both ends. Uniformly spray a high-temperature release agent on the surface of the corrugated lower die (7) to form a release agent layer. Then, lay and compact resin powder of the same resin type as that used to prepare the prepreg in the through groove (26) to form a first energy guiding structure (35). Lay the edge-sealed prepreg between the corrugated upper die (6) and the corrugated lower die (7), and perform compression molding to obtain a prepreg corrugated board. S3. Cut the obtained corrugated board into narrow strips, and the width of the narrow strip is the same as the height of the honeycomb core. Stack the narrow strips of the corrugated board with the side having the first energy guiding structure (35) facing down in sequence between the hexagonal core rod (15) and the semi-hexagonal welding head (14). Push and pull the quick clamp (30) and start the first ultrasonic vibration generator (11). The semi-hexagonal welding head (14) presses down to complete the ultrasonic connection of the nodes of the honeycomb core. Move the other nodes to be connected of the corrugated board to the welding area, and repeat the above process to obtain the honeycomb core (37). S4. Cut and stack the prepreg prepared in step S1 according to the service characteristics of the honeycomb. Lay and compact resin powder of the same resin type as that used to prepare the prepreg in the triangular cross-section groove on the surface of the lower pressing plate to form a second energy guiding structure (38). Then, lay the cut and stacked prepreg between the upper and lower pressing plates of a flat die press and perform compression molding to obtain the upper panel (36) and the lower panel (39). S5. Cut the honeycomb core obtained in S3, and cut the upper panel (36) and the lower panel (39) prepared in step S4 to the same size as the honeycomb core (37). Place the side of the upper panel (36) having the second energy guiding structure (38) facing down on the upper end surface of the honeycomb core (37). After alignment, place it in the welding sandwich bottom die (19). Push and pull the welding chuck (20) to complete the structural fixation and start the second ultrasonic vibration generator (13). The planar longitudinal vibration welding head (21) presses down to complete the connection between the upper panel (36) and the honeycomb core (37). Flip the welded structure by 180°, and repeat the above process to complete the connection between the lower panel (39) and the honeycomb core (37) to obtain a continuous fiber reinforced thermoplastic composite honeycomb sandwich structure.

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