A process for 3D printing continuous fiber reinforced composites

Abstract

The present invention relates to a process for 3D printing continuous fiber reinforced composite materials, belonging to the technical field of intelligent construction and building construction. By designing a precision control engine, continuous fiber 3D knitting and forming are realized, an adaptive path planning algorithm is developed to optimize the fiber arrangement direction, and a dynamic extrusion control system is integrated to achieve precise coordinated control of fiber dosage and printing speed gradient. A programmable telescopic positioning column array is deployed on the printing platform, and through characteristic processes such as continuous fiber spiral winding, multi-directional weaving and variable cross-section corrugation forming, prestressed tensile units, three-dimensional interlocking anchoring units and shear key units are prepared to form a modular FRP functional component system. It breaks through the problem of discreteness of mechanical properties of traditional short fibers, solves the problem of fiber damage in the existing hot melting process, realizes a tensile strength breakthrough of more than 1000 MPa, and is 6-8 times higher than that of short fibers.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent construction and building construction. Specifically, it relates to a process for 3D printing continuous fiber-reinforced composites. Background Art

[0002] Continuous fiber-reinforced composites (FRP) have been widely used in high-end fields such as aerospace and automotive manufacturing due to their high specific strength, lightweight, and corrosion resistance. Compared with traditional short fiber 3D printing technology, the mechanical property discreteness caused by the random distribution of fibers has long restricted its engineering applications - the tensile strength of short fiber materials is generally lower than 150 MPa, and the interfacial bonding efficiency is less than 60%. Therefore, short fiber materials are difficult to meet the strict requirements of building structures for load-bearing performance. This technical bottleneck directly limits the industrialization process of fiber composite materials in the field of intelligent construction. Moreover, when existing 3D printing technologies process FRP materials, they often cannot effectively control the arrangement and tension of fibers, resulting in unstable mechanical properties of printed parts. In addition, when traditional fused deposition modeling 3D printers print FRP materials, fiber damage is likely to occur due to the presence of the hot melting device, affecting the quality of the final components. Summary of the Invention

[0003] Aiming at the problems in the prior art, such as high mechanical property discreteness caused by the random distribution of short fibers, serious fiber damage in the hot melting process, and complex and costly traditional continuous fiber processes, the present invention proposes a process for 3D printing continuous fiber-reinforced composites. Through the reconstruction method of a special 3D printing equipment for FRP with dynamic parameter optimization and the in-situ forming process of FRP-reinforced structures guided by building mechanical properties, a technical breakthrough in high-performance composite construction is achieved.

[0004] The present invention adopts the following solutions:

[0005] A process for 3D printing continuous fiber-reinforced composites, comprising the following steps:

[0006] S1. Printer assembly step:

[0007] (1) Construction of the positioning system: Based on the three-dimensional coordinates of the prefabricated model, a standard positioning hole group is generated on the engineering-grade acrylic positioning template, and telescopic positioning columns are installed;

[0008] (2) Non-sticky interface treatment: The printing platform and telescopic positioning columns are completely wrapped with a polyethylene film, and a vacuum adsorption process is used to eliminate the wrinkles of the film layer to form a continuous isolation interface;

[0009] (3)Optimization of motion parameters: Based on the composition of the printed model, reconstruct the adaptive path planning algorithm in the dedicated slicing software, set the printing speed gradient to 15 mm / s - 30 mm / s, and the path curvature radius ≥ 8 mm to ensure that the fiber tension is stable in the range of 5 N - 8 N;

[0010] (4)Transformation of the low-temperature extrusion system: Remove the hot melt module of the traditional 3D printing head, integrate a dual-axis synchronous drive system, install a high-precision needle-shaped nozzle mechanism, and use the dual-axis synchronous drive system to drive the nozzle mechanism to move above the printing platform to achieve the constant-tension directional transportation of the fiber bundle;

[0011] S2. Printing and installation steps:

[0012] (5)Fiber deposition and forming: Import the FRP wire into the closed-loop control feeding system, and perform spatial weaving through the nozzle under the guidance of the telescopic positioning column. The interlayer staggered angle is controlled at 45 ± 5° to weave into a bending / shear-resistant FRP component;

[0013] (6)Vacuum-assisted impregnation: Remove the printed bending / shear-resistant FRP component together with the printing platform, perform several "infiltration - draining" cycles using a low-viscosity epoxy resin, and then cure it naturally at room temperature for 24 hours - 48 hours;

[0014] (7)Precision demolding: Dismantle the telescopic positioning column in reverse order, and use a flexible ejection mechanism to separate the component from the film interface;

[0015] (8)Modular assembly: Assemble the bending / shear-resistant FRP components according to the required structure through the prestress tensioning process;

[0016] (9)Composite structure forming: Pour concrete into the assembled 3D FRP for one-piece forming and cure it.

[0017] Furthermore, in step (1), the telescopic positioning column uses a single-pass positioning telescopic column and is installed with screws at each positioning point. A 2 mm screw cap embedding depth should be reserved in the lower threaded hole.

[0018] Furthermore, in step (6), perform three "infiltration - draining" cycles using a low-viscosity epoxy resin with a viscosity of 1200 ± 200 cps at 25°C, with an infiltration pressure of 0.3 MPa and a draining angle of 15°.

[0019] Furthermore, in step (8), the pre-tightening force of the prestress tensioning process is 30% of the ultimate load, and interface curing is carried out in an environment of 25°C / 60%RH for 72 hours after assembly.

[0020] Further, the biaxial synchronous drive system includes a mounting frame and a cross beam movably disposed on the mounting frame. A first transmission gear and a second transmission gear are disposed at one end of the cross beam, and a third transmission gear and a fourth transmission gear are oppositely disposed at the other end. A first fixed gear, a second fixed gear, a third fixed gear and a fourth fixed gear are disposed on the mounting frame. A servo motor is respectively disposed on the first fixed gear and the second fixed gear; upper and lower double-layer belt grooves are disposed on each fixed gear and transmission gear; a first transmission belt and a second transmission belt are further included. The first transmission belt is wound in the upper belt grooves of the first fixed gear, the second fixed gear, the third fixed gear, the fourth fixed gear, the second transmission gear and the fourth transmission gear, and both ends thereof are connected to the nozzle mechanism; the second transmission belt is wound in the lower belt grooves of the first fixed gear, the second fixed gear, the third fixed gear, the fourth fixed gear, the first transmission gear and the third transmission gear, and both ends thereof are connected to the nozzle mechanism; by coordinately controlling the rotation directions and rotation speeds of the two servo motors, the cross beam is driven to move back and forth along the mounting frame, and the nozzle mechanism can be driven to move left and right along the cross beam.

[0021] Further, a lifting mechanism is disposed on the printing platform, and the lifting mechanism is adapted to drive the printing platform to lift within the mounting frame.

[0022] Further, the nozzle mechanism includes a positioning housing, a rotating motor mounted on the positioning housing, a main shaft connected to the rotating motor, and a screw rod connected to the main shaft; a material roll and a needle-shaped nozzle are further mounted on the positioning housing; the material roll is adapted to supply a continuous fiber strip to the screw rod; the rotating motor drives the screw rod to rotate through the main shaft, so that the continuous fiber strip is output downward along the screw groove of the screw rod to the needle-shaped nozzle.

[0023] Further, a first positioning bracket is disposed below the material roll to guide the continuous fiber strip to be output toward the screw rod; the needle-shaped nozzle is disposed parallel to the main shaft.

[0024] Beneficial effects:

[0025] This solution realizes continuous fiber 3D knitting and forming by designing a precision control engine, develops an adaptive path planning algorithm to optimize the fiber arrangement direction, integrates a dynamic extrusion control system to achieve precise coordinated control of fiber dosage and printing speed gradient, and deploys a programmable telescopic positioning column array on the printing platform to ensure the spatial positioning accuracy of long fibers at the ±0.1 mm level, thus constructing an intelligent printing system that adapts to the functional requirements of building structures. Through special processes such as continuous fiber spiral winding, multi-directional interleaved knitting, and variable cross-section corrugation forming, prestressed tensile units with gradient modulus, mechanical anchoring units with three-dimensional interlocking interfaces, and shear key units for optimized shear stress transfer are respectively prepared to form a modular FRP functional component system. Adopting a two-stage composite process of vacuum-assisted epoxy resin impregnation and intelligent assembly, the FRP functional system and the concrete matrix are co-cured to finally form a composite structure with both tensile and shear resistance and high interfacial bonding strength. This technology breaks through the problems of scattered mechanical properties and insufficient strength of traditional short fiber materials, solves the problem of fiber damage in the hot melt process, realizes the high-integrity printing of continuous fibers, and even makes its tensile strength exceed 1000 MPa under 3D structures (6 - 8 times higher than traditional short fiber materials). Description of the Drawings

[0026] Figure 1 is a schematic flow chart of the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0027] Figure 2 is a schematic structural diagram of a biaxial synchronous drive system of the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0028] Figure 3 is a schematic structural diagram of a nozzle mechanism of the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0029] Figure 4 is a schematic side view structural diagram of a nozzle mechanism of the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0030] Figure 5 is a schematic exploded view structural diagram of a nozzle mechanism of the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0031] Figure 6 is a schematic diagram of preparing a rectangular 3D FRP system by using the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0032] Figure 7 is a schematic diagram of preparing a non-rectangular 3D FRP system by using the process of 3D printing continuous fiber reinforced composite materials in an embodiment of the present invention;

[0033] Figure 8 This is a physical diagram of a rectangular 3DFRP system prepared by the process of using a 3D printing continuous fiber reinforced composite material in an embodiment of the present invention;

[0034] Figure 9 This is a physical diagram of a T-shaped 3DFRP system prepared by the process of using a 3D printing continuous fiber reinforced composite material in an embodiment of the present invention;

[0035] Figure 10 This is a list of the strengths of existing short fiber materials in an embodiment of the present invention;

[0036] Figure 11 This is a detailed table showing the performance of continuous fiber reinforced concrete members by the process of using a 3D printing continuous fiber reinforced composite material in an embodiment of the present invention.

[0037] Reference numerals: nozzle mechanism 1, positioning housing 11, rotating motor 12, main shaft 13, screw 14, material roll 15, needle-shaped nozzle 16, positioning bracket 17, mounting frame 21, first fixed gear 211, second fixed gear 212, third fixed gear 213, fourth fixed gear 214, cross beam 22, first transmission gear 221, second transmission gear 222, third transmission gear 223, fourth transmission gear 224, printing platform 3, telescopic positioning column 4. Detailed implementation manners

[0038] Embodiment 1

[0039] Combined with Figure 1 , this embodiment provides a process for 3D printing continuous fiber reinforced composite materials, including the following steps:

[0040] S1. Printer assembly step:

[0041] (1) Construction of the positioning system: Based on the three-dimensional coordinates of the prefabricated model, a standard positioning hole group is generated on an engineering-grade acrylic positioning template (thickness ≥ 5 mm), and the telescopic positioning column 4 with a self-locking threaded interface is installed; the telescopic positioning column 4 adopts a single-pass positioning telescopic column, which is suitable for realizing telescoping through programming, allowing its height to be adjusted according to the fiber path requirements, so as to adapt to the printing of FRP components with different shapes and sizes; it is installed with screws at each positioning point, and a 2 mm screw cap embedding depth is reserved for the lower threaded hole for leveling;

[0042] (2)Non-sticky interface treatment: Use a 0.1-mm-thick polyethylene film to completely wrap the printing platform 3 and the telescopic positioning column 4. Adopt a vacuum adsorption process to eliminate the wrinkles in the film layer and form a continuous isolation interface; prevent the FRP component from bonding with the printing platform 3 during the subsequent epoxy resin infiltration process; the selection of the polyethylene film should meet the requirements of low friction coefficient and high ductility to ensure that it does not break and fits tightly during the vacuum adsorption process;

[0043] (3)Optimization of motion parameters: Based on the composition of the printed model, reconstruct the adaptive path planning algorithm in the dedicated slicing software, set the printing speed gradient to 15 mm / s - 30 mm / s, and the path curvature radius ≥ 8 mm to ensure that the fiber tension is stably in the range of 5 N - 8 N; this algorithm dynamically adjusts the movement trajectory and speed of the print head to make the fibers evenly arranged and avoid breakage or accumulation caused by tension fluctuations;

[0044] (4)Transformation of the low-temperature extrusion system: Remove the hot melt module of the traditional 3D print head, integrate a two-axis synchronous drive system, install a high-precision needle-shaped nozzle mechanism, and use the two-axis synchronous drive system to drive the nozzle mechanism to move above the printing platform 3 to achieve the constant-tension directional delivery of the fiber bundle; the rotational speed accuracy of the two-axis synchronous drive system is controlled within ±0.5 rpm, and a high-precision needle-shaped nozzle with an inner diameter of 0.5 ± 0.02 mm is configured to precisely control the constant-tension directional delivery of the fiber bundle and avoid damage to the fiber strength caused by hot melting.

[0045] S2. Printing and installation steps:

[0046] (5)Fiber deposition and forming: Import the FRP wire into the closed-loop control feeding system, and perform space weaving through the nozzle under the guidance of the telescopic positioning column 4. The interlayer staggered angle is controlled at 45 ± 5° to ensure the maximum utilization of fiber directionality and mechanical properties, so as to weave into a flexural / shear-resistant FRP component;

[0047] (6)Vacuum-assisted impregnation: Remove the printed flexural / shear-resistant FRP component together with the printing platform 3, and perform several "infiltration - draining" cycles using low-viscosity epoxy resin, and then naturally place it at room temperature for 24 - 48 hours to cure; specifically, the vacuum-assisted impregnation uses low-viscosity epoxy resin (viscosity at 25°C is 1200 ± 200 cps) to perform three "infiltration - draining" cycles, with each infiltration pressure of 0.3 MPa and the draining angle of 15°, and then naturally place it at room temperature for 24 - 48 hours to cure to complete the shaping of the FRP component;

[0048] (7)Precision demolding: Reverse-disassemble the telescopic positioning post 4, and use a flexible ejection mechanism to separate the component from the film interface; control the ejection force within the range of ≤50N to ensure that the FRP component is not damaged during the demolding process; the flexible ejection mechanism can be combined with the existing spring buffer device and limit block mechanism to ensure a smooth and controllable ejection process.

[0049] (8)Modular assembly: The flexural / shear-resistant FRP components are assembled by the prestress tensioning process according to the required structure; the pre-tightening force of the prestress tensioning process is 30% of the ultimate load, and interface curing is carried out for 72 hours in an environment of 25℃ / 60%RH after assembly; through this embodiment, FRP components with flexural, shear-resistant, and compressive functions can be printed, supporting the standardized design-printing-assembly process, and significantly improving the construction efficiency; for example, the flexural FRP component can be realized by the prestress tensioning process, the shear-resistant FRP component can be realized by the three-dimensional interlocking interface design, and the compressive component can be realized by gradient modulus optimization. Each component forms a standardized functional unit through modular assembly.

[0050] (9)Composite structure forming: Pour concrete into the assembled 3D FRP for one-piece forming and curing. The surface of the FRP component needs to be cleaned before concrete pouring to remove residual epoxy resin or other impurities; the key to this step lies in the co-curing of the concrete and the FRP component, which significantly enhances the bearing capacity of the overall structure by improving the interfacial bonding strength.

[0051] Combined with Figures 1 to 2As shown in the figure, the dual-axis synchronous drive system includes a mounting frame 21 disposed above the printing platform 3. A cross beam 22 is movably disposed on the mounting frame. The cross beam 22 is adapted to move back and forth on the mounting frame 21. The nozzle mechanism 1 is disposed on the cross beam 22 and is adapted to move left and right on the cross beam 22. Specifically, a first driving gear 221 and a second driving gear 222 are disposed at one end of the cross beam 22, and a third driving gear 223 and a fourth driving gear 224 are oppositely disposed at the other end. A first fixed gear 211, a second fixed gear 212, a third fixed gear 213 and a fourth fixed gear 214 are disposed on the mounting frame 21. The first fixed gear 211, the second fixed gear 212, the third fixed gear 213 and the fourth fixed gear 214 are respectively disposed at the four corners of the rectangle of the mounting frame 21. A servo motor is respectively disposed on the first fixed gear 211 and the second fixed gear 212; upper and lower double belt grooves are disposed on each fixed gear and driving gear; a first transmission belt 23 and a second transmission belt 24 are further included. The first transmission belt 23 is wound in the upper belt grooves of the first fixed gear 211, the second fixed gear 212, the third fixed gear 213, the fourth fixed gear 214, the second driving gear 222 and the fourth driving gear 224, and both ends are connected to the nozzle mechanism 1; the second transmission belt 24 is wound in the lower belt grooves of the first fixed gear 211, the second fixed gear 212, the third fixed gear 213, the fourth fixed gear 214, the first driving gear 221 and the third driving gear 223, and both ends are connected to the nozzle mechanism 1; by coordinately controlling the rotation directions and rotation speeds of the two servo motors, the cross beam 22 is driven to move back and forth along the mounting frame 21, and the nozzle mechanism 1 can be driven to move left and right along the cross beam 22. It should be noted that a lifting mechanism is disposed on the printing platform 3. The lifting mechanism is adapted to drive the printing platform 3 to lift within the mounting frame. By cooperating the lifting mechanism with the dual-axis synchronous drive system, the 3D printing function can be realized. The lifting mechanism can be a ball screw nut pair mechanism disposed between the printing platform 3 and the mounting frame 21.

[0052] Combined with Figures 1 to 5As shown, the nozzle mechanism 1 includes a positioning housing 11, a rotating motor 12 installed on the positioning housing 11, a main shaft 13 connected to the rotating motor 12, and a screw 14 connected to the main shaft 13; a material roll 15 and a needle-shaped nozzle 16 are also installed on the positioning housing 11; the material roll 15 is adapted to supply continuous fiber strips to the screw 14; the rotating motor 12 drives the screw 14 to rotate through the main shaft 13, so that the continuous fiber strips are output downward along the spiral groove of the screw 14 to the needle-shaped nozzle 16. A positioning bracket 17 is arranged below the material roll 15 to guide the continuous fiber strips to be output toward the screw 14; the needle-shaped nozzle 16 is arranged parallel to the main shaft 13. After the continuous fiber strips come out of the material roll 15, they are guided to the screw 14 through the positioning bracket 17, and then wind and move in the spiral groove along the helix direction of the screw 14, and are vertically led to the needle-shaped nozzle 16 at the bottom end of the screw for export. The needle-shaped nozzle 16 is provided with a tee printing port and an adapter, and the continuous fiber strips are output through the tee printing port. By rotating the screw 14, prestress can be applied to the continuous fiber strips. During operation, in the initial positioning stage, a positioning fixture is used to fix the continuous fiber strips exported from the needle-shaped nozzle 16 to the initial telescopic positioning column 4, and preliminary positioning is completed through the fixing frame; in the tension control stage, a 42-step motor (i.e., the rotating motor 12) is used to accurately control the rotation speed, apply a prestress of 5-8N, and cooperate with the needle-shaped nozzle 16 to realize the lateral tension directional output of continuous fibers; compared with the material loss and structural defect problems easily generated by traditional hot melt forming modules, the precision control engine of this system can effectively avoid material loss and structural damage and give full play to the ultimate performance of the materials.

[0053] In this embodiment, the tensile strength is significantly improved through continuous fiber spiral winding and multi-directional braiding process: combined Figure 10 with Figure 11 As shown, due to the random distribution of fibers, the tensile strength of traditional short fiber 3D printing is generally lower than 450MPa. However, in this embodiment, through continuous fiber spiral winding and multi-directional braiding process, the tensile strength breaks through more than 1000MPa, and the strength is increased by 3-8 times. In addition, by optimizing the shear stress transfer path through variable cross-section corrugated forming technology and combining with the vacuum impregnation process, the interfacial bonding strength is significantly improved. Figure 11 As shown, the experimental data shows that the FRP strength utilization ratio of the 150mm U-shaped wrapped specimen reaches 90.1%, the failure mode is upgraded to fiber fracture, and the interfacial debonding ratio is significantly reduced.

[0054] Furthermore, the present invention synergistically optimizes process efficiency and material utilization rate through a low-temperature extrusion system and a vacuum impregnation process. The low-temperature extrusion system adopts a dual-axis synchronous drive and a needle-shaped nozzle configuration, avoiding thermal damage, preserving the intrinsic properties of the fibers, and reducing fiber loss by 10-15%. The vacuum impregnation and normal-temperature curing processes achieve 28-day integrated curing of FRP-concrete, with an efficiency improvement of 50% compared to traditional continuous fiber processes (which require an additional 7-14 days of autoclave post-treatment). The solution of this embodiment can be used for the manufacture of complex structures in the field of intelligent construction. For example, in the seismic reinforcement of high-rise buildings, the tensile units prepared by continuous fiber spiral winding and multi-directional braiding processes can significantly improve the tensile strength of the structure. In bridge construction, the variable cross-section corrugation forming technology optimizes the shear stress transfer path, significantly enhancing the interfacial bonding strength and thus extending the service life of the bridge. In addition, the solution of this embodiment also supports the hybrid printing of recycled fibers, conforms to the trend of green construction, and has significant sustainability advantages.

[0055] Example 2

[0056] Combined with Figure 6 and Figure 8 As shown, this embodiment provides an installation method for a rectangular 3D FRP system. The process of 3D printing continuous fiber-reinforced composite materials is used to print and form curved FRP, U-shaped anchoring FRP, and shear-resistant FRP. The U-shaped anchoring FRP is installed at both ends of the curved FRP, and then the shear-resistant FRP is installed on both sides of the curved FRP, thereby forming a rectangular 3D FRP system with an opening at the top. The inner wall of the 3D FRP system is infiltrated with epoxy resin glue, and then concrete is poured into the opening to form the required component.

[0057] Example 3

[0058] Combined with Figure 7 and Figure 9 As shown, this embodiment provides a non-rectangular 3D FRP system. The process of 3D printing continuous fiber-reinforced composite materials is used to print and form bending-resistant FRP, U-shaped anchoring FRP, and shear-resistant FRP. The U-shaped anchoring FRP is installed at both ends of the bending-resistant FRP, and then the shear-resistant FRP is installed on both sides of the bending-resistant FRP to form a non-rectangular 3D FRP system. Then, the inner wall of the 3D FRP system is infiltrated with epoxy resin glue, and concrete is poured into the opening to form the required component (such as a T-shaped one).

[0059] It should be understood that the above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention.

[0060] The above introduction to the accompanying drawings used in the embodiments only shows some embodiments of the present invention and should not be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

Claims

1. A process for 3D printing continuous fiber reinforced composites, characterized in that, It includes the following steps: S1. Printer assembly steps: (1) Positioning system construction: Based on the three-dimensional coordinates of the prefabricated model, generate a standard positioning hole group on the engineering-grade acrylic positioning template and install telescopic positioning columns; (2) Non-sticky interface treatment: Use polyethylene film to completely wrap the printing platform and telescopic positioning columns, and adopt a vacuum adsorption process to eliminate film wrinkles to form a continuous isolation interface; (3) Motion parameter optimization: Based on the composition of the printing model, reconstruct the adaptive path planning algorithm in the slicing software, set the printing speed gradient to 15 mm / s - 30 mm / s, and the path curvature radius ≥ 8 mm to ensure that the fiber tension is stable in the range of 5 N - 8 N; (4) Low-temperature extrusion system transformation: Remove the hot-melt module of the traditional 3D printing head, integrate a two-axis synchronous drive system, install a needle-shaped nozzle mechanism, and use the two-axis synchronous drive system to drive the nozzle mechanism to move above the printing platform to achieve constant-tension directional delivery of fiber bundles; S2. Printing and installation steps: (5) Fiber deposition and molding: Import the FRP wire into the closed-loop control feeding system, and perform spatial weaving through the nozzle under the guidance of the telescopic positioning column. The interlayer staggered angle is controlled at 45 ± 5° to weave into a bending / shear-resistant FRP component; (6) Vacuum-assisted impregnation: Remove the printed bending / shear-resistant FRP component together with the printing platform, and perform several "infiltration - draining" cycles with an epoxy resin having a viscosity of 1200 ± 200 cps at 25°C, and then naturally place it at room temperature for 24 hours - 48 hours for curing; (7) Precision demolding: Dismantle the telescopic positioning column in reverse order, and use a flexible ejection mechanism to separate the component from the film interface; (8) Modular assembly: The bending / shear-resistant FRP component is assembled by the prestress tensioning process according to the required structure; (9) Composite structure forming: Pour concrete into the assembled 3D FRP for one-piece forming and perform curing.

2. The process for 3D printing continuous fiber reinforced composite materials according to claim 1, characterized in that, In step (1), the telescopic positioning column is a single-pass positioning telescopic column and is installed with screws at each positioning point. A screw cap embedding depth of 2 mm should be reserved for the lower threaded hole.

3. The process for 3D printing continuous fiber-reinforced composite materials according to claim 1, characterized in that, In step (6), three "infiltration - draining" cycles are performed with a low-viscosity epoxy resin having a viscosity of 1200 ± 200 cps at 25°C. The infiltration pressure for each time is 0.3 MPa, and the draining angle is 15°.

4. The process for 3D printing continuous fiber reinforced composites according to claim 1, characterized in that, In step (8), the pre-tightening force of the prestress tensioning process is 30% of the ultimate load, and interface curing is performed in an environment of 25°C / 60%RH for 72 hours after assembly.

5. The process for 3D printing continuous fiber reinforced composites according to claim 1, characterized in that, The double-axis synchronous drive system includes an installation frame and a cross beam movably arranged on the installation frame. One end of the cross beam is provided with a first transmission gear and a second transmission gear, and the other end is oppositely provided with a third transmission gear and a fourth transmission gear. The installation frame is provided with a first fixed gear, a second fixed gear, a third fixed gear and a fourth fixed gear, and a servo motor is respectively arranged on the first fixed gear and the second fixed gear; upper and lower double-layer belt grooves are arranged on each fixed gear and transmission gear; a first transmission belt and a second transmission belt are further included. The first transmission belt is wound in the upper belt grooves of the first fixed gear, the second fixed gear, the third fixed gear, the fourth fixed gear, the second transmission gear and the fourth transmission gear, and both ends are connected to the nozzle mechanism; the second transmission belt is wound in the lower belt grooves of the first fixed gear, the second fixed gear, the third fixed gear, the fourth fixed gear, the first transmission gear and the third transmission gear, and both ends are connected to the nozzle mechanism; by coordinately controlling the rotation direction and rotation speed of the two servo motors, the cross beam is driven to move back and forth along the installation frame, and the nozzle mechanism can be driven to move left and right along the cross beam.

6. The process for 3D printing continuous fiber-reinforced composites according to claim 5, characterized in that, A lifting mechanism is arranged on the printing platform, and the lifting mechanism is adapted to drive the printing platform to lift within the installation frame.

7. The process of 3D printing continuous fiber reinforced composites according to claim 1, characterized in that, The nozzle mechanism includes a positioning housing, a rotating motor installed on the positioning housing, a main shaft connected to the rotating motor, and a screw rod connected to the main shaft; a material roll and a needle-shaped nozzle are further installed on the positioning housing; the material roll is adapted to supply a continuous fiber strip to the screw rod; the rotating motor drives the screw rod to rotate through the main shaft, so that the continuous fiber strip is output downward along the screw groove of the screw rod to the needle-shaped nozzle.

8. The process for 3D printing continuous fiber reinforced composites according to claim 7, characterized in that, A first positioning bracket is arranged below the material roll to guide the continuous fiber strip to output towards the screw rod; the needle-shaped nozzle is arranged parallel to the main shaft.

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