A method for cross-scale regulation of waste FRP recycling and 3D printing

Abstract

The present application relates to the field of waste composite material recycling and 3D printing additive manufacturing, and discloses a cross-scale regulated waste FRP recycling and 3D printing method, which comprises the following steps: performing pretreatment and high-quality fiber recovery of waste FRP to obtain regenerated fibers; performing cleaning and surface activation of the fibers to anchor magnetic nanoparticles on the surface of the regenerated fibers; performing preparation of regenerated FRP-based 3D printing composite wires; establishing a printing process parameter system special for regenerated materials; and performing 3D printing forming, in which an external magnetic field is applied to control the orientation of the regenerated fibers during the printing process to obtain a three-dimensional solid member. The present application reduces fiber damage by using laser-assisted pretreatment and low-energy dissociation process in the recycling step; gives the fibers magnetic responsiveness by anchoring magnetic nanoparticles on the surface of the regenerated fibers; and actively regulates fiber arrangement by using an external magnetic field during 3D printing forming.

Description

Technical Field

[0001] This invention relates to the field of waste composite material recycling and 3D printing additive manufacturing, specifically a method for recycling and 3D printing waste FRPs that can be controlled across scales. Background Technology

[0002] Fiber-reinforced polymer (FRP) composites have been widely used in aerospace, transportation, and civil engineering due to their excellent mechanical properties and lightweight characteristics. However, with the mass production and service expiration of FRP components, the amount of waste FRP is continuously increasing, posing a serious environmental and resource disposal challenge.

[0003] Currently, the recycling technology for waste FRP mainly focuses on mechanical methods. Existing mechanical methods generally employ energy-intensive crushing and pulverizing processes. These processes rely on strong impact and shear forces to dissociate the FRP, which severely damages the structural integrity of the recycled fibers, resulting in short recycled fibers with significantly reduced mechanical properties.

[0004] Furthermore, existing dissociation processes lack an effective pretreatment step for the size of FRP blocks before execution. This necessitates increased energy consumption during subsequent dissociation and further exacerbates mechanical damage to the fibers. Simultaneously, the dissociation products obtained by current processes are typically a disordered mixture of fibers and resin powder. The lack of an effective post-processing grading unit prevents the sorting of recycled fibers by length, severely restricting the reuse of regenerated fibers in high-performance products. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cross-scale controllable method for recycling and 3D printing waste FRP, which solves the problems of fiber damage and disordered length distribution caused by existing waste FRP recycling processes. It also solves the problems of poor bonding between recycled fibers and matrix resin and large fluctuations in composite wire diameter, and further solves the problem of the inability to actively control the internal fiber arrangement during 3D printing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for cross-scale controlled recycling and 3D printing of waste FRP, comprising the following steps: S1. Perform the pretreatment and high-quality fiber recycling steps for waste FRP: Perform a multi-stage controlled dissociation process to obtain recycled fibers with length distribution from waste FRP; S2. Perform the fiber cleaning and surface activation regeneration steps: clean, dry and surface chemically modify the regenerated fiber obtained in step S1. The surface chemical modification anchors magnetic nanoparticles on the surface of the regenerated fiber to obtain regenerated fiber with magnetic nanoparticles anchored on the surface. S3. Perform the preparation steps of recycled FRP-based 3D printing composite filament: Mix the recycled fiber with magnetic nanoparticles anchored on the surface obtained in step S2 with the matrix resin, and prepare the composite filament through melt extrusion, filament forming and quality inspection. S4. Steps for establishing a dedicated printing process parameter system for recycled materials: Print standard samples using the composite filament obtained in step S3, and test the standard samples to determine the printing process parameters. S5. Perform 3D printing molding step: Use the printing process parameters determined in step S4 and the composite filament obtained in step S3 to perform fused deposition modeling printing, and apply an external magnetic field to control the orientation of the regenerated fibers in the extruded composite filament melt to obtain a three-dimensional solid component with internal fibers arranged in a preset manner.

[0007] In one technical solution, the multi-stage controllable dissociation process in step S1 specifically includes: First, the waste FRP components are macroscopically crushed using a macroscopic crushing module to obtain material blocks; Next, the material block is subjected to laser-assisted preprocessing using a laser-assisted preprocessing module to obtain a smaller material block; Finally, the pretreated material blocks are subjected to low-energy dissociation and grading through a low-energy dissociation and grading module to obtain the recycled fibers with the length distribution.

[0008] In one technical solution, the laser-assisted pretreatment step involves controlling the laser's output power, scanning speed, and scanning path to enable the laser beam to perform grid cutting on the material block. The key to this step is ensuring uniform block size, which facilitates resin release from the block in subsequent processes.

[0009] In one technical solution, the low-energy dissociation and classification step utilizes a horizontal drum mill containing flexible abrasive media. Dissociating the material at lower grinding times and speeds reduces mechanical damage to the fibers. Furthermore, a multi-stage classification unit equipped with multiple layers of screens with varying apertures classifies the dissociated products, achieving cross-scale sorting of the recycled fibers to obtain recycled fibers of different lengths.

[0010] In one technical solution, the fiber cleaning and surface activation regeneration steps in step S2 specifically include the following steps in sequence: The recycled fibers are subjected to resin pyrolysis treatment under microwave heating through a resin pyrolysis module to remove residual resin adhering to the fiber surface. The pyrolyzed fibers are ultrasonically cleaned using an ultrasonic cleaning module to remove pyrolysis products and inorganic fillers. The washed fibers are then dried. In the surface modification module, the dried fibers are subjected to plasma activation treatment to introduce active groups on the fiber surface; The recycled fibers, after plasma activation treatment, are immersed in a solution containing a silane coupling agent and magnetic nanoparticles for a chemical grafting reaction. The silane coupling agent acts as a bridging agent, enabling the magnetic nanoparticles to be chemically bonded and anchored to the surface of the regenerated fibers, thereby imparting magnetic responsiveness to the regenerated fibers.

[0011] In one technical solution, the melt extrusion step in step S3 is performed using a twin-screw extruder. The screw assembly of the twin-screw extruder is arranged with conveying and distributive mixing as the main functions and shear mixing as a secondary function.

[0012] In one technical solution, during the wire forming and quality inspection step in step S3, the diameter of the extruded wire is measured in real time by a diameter measuring unit, and the traction speed of the traction unit is adjusted by a control unit. This achieves closed-loop feedback control of the composite wire diameter, ensuring the uniformity of the wire diameter.

[0013] In one technical solution, the test in step S4 specifically involves: performing a tensile strength test on the standard specimen using a mechanical property testing unit. The determination of printing process parameters specifically involves: analyzing the tensile strength test data using a data analysis terminal to determine the optimal combination of printing process parameters, including printing temperature, printing speed, and layer height.

[0014] In one technical solution, the orientation control in step S5 is achieved through a fiber orientation control module. The fiber orientation control module includes an array of electromagnets arranged outside the print nozzles of the fused deposition modeling (FDM) printer. The electromagnet array is controlled by an orientation control unit, which is electrically connected to the main controller of the FDM printer for synchronizing print path information.

[0015] In one technical solution, the execution process of the orientation control includes: First, during the printing path planning stage, the fiber target orientation angle is preset for different areas of the component; During printing, the orientation control unit calculates and drives the electromagnet array to generate a magnetic field in the corresponding direction based on the real-time position and motion vector of the printing nozzle and the preset fiber target orientation angle through a built-in control algorithm. Ultimately, the regenerated fibers containing magnetic nanoparticles in the melt extruded from the nozzle overcome the viscous force of the melt under the action of the magnetic field torque, align themselves along the direction of the magnetic field, and are fixed as the material cools.

[0016] This invention, through the aforementioned technical solution, achieves the recovery of regenerated fibers with controllable length and magnetic response from waste FRP, and combines this with melt extrusion technology to prepare high-quality 3D printing composite filaments. Furthermore, by establishing a dedicated printing process parameter system and utilizing an external magnetic field to actively control the orientation of the magnetized regenerated fibers during the melt deposition modeling process, a high-performance three-dimensional solid component with internally reinforcing fibers arranged as needed is ultimately obtained, realizing the high-value closed-loop reuse of waste FRP.

[0017] This invention provides a method for cross-scale controlled recycling and 3D printing of waste FRP. It has the following beneficial effects: 1. This invention achieves gentle dissociation of waste FRP by setting up a laser-assisted pretreatment step to engrave grooves on the surface of the material block, combined with a low-energy dissociation step using flexible abrasive media, and setting up a multi-level grading unit at the end, thereby obtaining recycled fibers with length distribution and reducing mechanical damage to the fibers during the recycling process.

[0018] 2. This invention performs fiber cleaning and surface activation regeneration steps, and uses chemical bonding to anchor magnetic nanoparticles on the surface of the regenerated fiber, thereby endowing the regenerated fiber with magnetic response function; at the same time, the diameter closed-loop feedback control is adopted in the preparation of composite filament to ensure the diameter uniformity of the composite filament for 3D printing.

[0019] 3. This invention applies an external magnetic field during the fused deposition modeling printing process. By using an array of electromagnets arranged outside the printing nozzle, a magnetic torque is applied to the regenerated fibers containing magnetic nanoparticles in the extruded melt. This enables active control over the fiber arrangement inside the three-dimensional solid component, resulting in a reinforced structure with an on-demand arrangement in the final component. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of crushing, grinding, and screening waste FRP according to the present invention; Figure 2 This is a flow chart of the resin pyrolysis treatment process for waste FRP according to the present invention. Figure 3 This is a flow chart of the high-quality recycling process for waste FRP according to the present invention; Figure 4 This is a process flow diagram for preparing the recycled FRP-based 3D printing composite filament of the present invention; Figure 5 This is a schematic diagram of the 3D printing molding based on recycled FRP according to the present invention.

[0021] Among them, 101 is the macroscopic crushing module; 102 is the laser-assisted pretreatment module; 102a is the laser source; 102b is the beam transmission system; 102c is the scanning galvanometer; 102d is the three-dimensional processing platform; 102e is the control unit; 102f is the dust collection device; 103 is the low-energy dissociation and classification module; 103a is the grinding chamber; 103b is the grinding media; 103c is the drive motor; 103d is the multi-stage classification unit; 103e is the control unit; and 101 is the resin. 201a, pyrolysis module; 201b, sealed high-pressure resistant reaction chamber; 201c, microwave generator; 201d, reaction medium injection system; 201e, pressure and temperature sensing control system; 201f, waste gas treatment interface; 201g, wastewater treatment interface; 301, main control unit; 301, ultrasonic cleaning module; 301a, cleaning tank; 302, vacuum filtration module; 303, constant temperature drying module; 303a, drying chamber; 304, surface modification module; 304a 404a Plasma reaction unit; 404b Chemical grafting reaction unit; 404c Weighing unit; 404d Pretreatment unit; 404e Mixing unit; 404f Melt extrusion module; 404a Loss-in-weight feeding unit; 404b Twin-screw extruder barrel; 404c Screw assembly; 404d Zoned heating and cooling system; 404e Drive motor; 404f Die head; 404g Main control unit; 405 Wire forming and quality inspection system; 405a 505a Cooling unit; 505b Diameter measurement unit; 505c Traction unit; 405d Winding unit; 405e Control unit; 501 FDM printer; 501a Printing nozzle; 502 Mechanical property testing unit; 503 Data analysis terminal; 504 Fiber orientation control module; 504a Electromagnet array; 504b Programmable DC power supply; 504c Orientation control unit; 505 Size evaluation module; 506 Microstructure analysis module. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See attached document Figure 1 Appendix Figure 2 With appendix Figure 3 , attached Figure 1 This is a process flow diagram of crushing, grinding, and screening waste FRP according to an embodiment of the present invention, with attached... Figure 2 This is a process flow diagram of resin pyrolysis treatment of waste FRP according to an embodiment of the present invention, with attached... Figure 3 This is a flow chart of a high-quality recycling process for waste FRP according to an embodiment of the present invention. In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, the pretreatment of waste FRP and the high-quality fiber recycling steps include: Multi-stage controllable dissociation process: The steps of the multi-stage controllable dissociation process are implemented through a waste FRP dissociation system. The waste FRP dissociation system includes a macroscopic crushing module 101, a laser-assisted pretreatment module 102, and a low-energy dissociation and classification module 103.

[0024] The first step is macroscopic crushing. Large-sized waste FRP components to be processed are placed in the macroscopic crushing module 101. The macroscopic crushing module 101 has a built-in hydraulic shearing unit. This unit applies high-intensity shearing force to the waste FRP components via a hydraulic drive, causing them to fracture and form pre-sized blocks. By setting the feed length and shearing frequency of the hydraulic shearing unit, blocks within a target size range can be controllably obtained, for example, blocks with dimensions in the range of 5-10 cm, to facilitate processing in subsequent modules.

[0025] Next, a laser-assisted pretreatment step is performed. The macroscopically crushed material is conveyed to the laser-assisted pretreatment module 102. The laser-assisted pretreatment module 102 includes a laser generator and a scanning galvanometer. By setting the laser's output power, scanning speed, and scanning path through the control system, the laser beam etches deep, grid-like grooves on the resin matrix along the surface of the material. The purpose of this step is no longer to efficiently remove most of the resin, but to perform structural weakening pretreatment on the rigid FRP block without damaging the internal fibers. Microcracks are created inside the matrix through thermal shock and grooving, disrupting its dense structure and providing larger reaction medium penetration channels and reaction surface area for subsequent resin pyrolysis (e.g., resin pyrolysis module 201), and reducing the mechanical load for subsequent fiber dissociation (low-energy dissociation and classification module 103). Although laser treatment itself is a high-energy-consuming process, its purpose is to improve the efficiency of subsequent chemical and physical treatments. The overall energy efficiency and processing speed of the entire process need to be balanced and optimized in conjunction with the specific process. The control system can be equipped with a depth monitoring function based on machine vision or spectral sensing to provide real-time feedback on the grooving status and ensure that the laser automatically adjusts its power or stops before reaching the fiber layer.

[0026] Finally, a low-energy dissociation and classification step is performed. The product, after laser-assisted pretreatment, is input into the low-energy dissociation and classification module 103. The low-energy dissociation and classification module 103 contains flexible abrasive media and multiple layers of screens. In this embodiment, the abrasive chamber 103a is a horizontal drum mill, and the abrasive media 103b is a high-density rubber rod or polyurethane abrasive media. By setting a low abrasive time and rotation speed, the fiber bundles are broken up and dissociated under the gentle compression and kneading action of the abrasive media. This low-energy dissociation method aims to maximize the protection of the original length and aspect ratio of the fibers and avoid fiber damage caused by high-energy impacts. The product is then separated by screens with different aperture sizes. Cross-scale sorting of regenerated fibers is achieved by using a combination of aperture sizes of the classification screens (e.g., 5 mm, 2 mm, 1 mm) to obtain regenerated fibers with a specific length distribution.

[0027] Fiber cleaning and surface activation regeneration: The fiber cleaning and surface activation regeneration steps are implemented using a fiber regeneration system. The fiber regeneration system includes a resin pyrolysis module 201, an ultrasonic cleaning module 301, a vacuum filtration module 302, a constant temperature drying module 303, and a surface modification module 304.

[0028] The regenerated fibers from the low-energy dissociation and classification module 103 are conveyed to the resin pyrolysis module 201. The resin pyrolysis module 201 contains a microwave reaction chamber. Under specific atmospheric (e.g., water vapor or inert gas) and pressure conditions, polar resin molecules are heated by microwaves, causing hydrothermal pyrolysis of the resin remaining on the fiber surface, achieving deep separation of the fiber and resin. The module is also connected to an exhaust gas treatment system and a wastewater treatment system for collecting and treating the oil and gas products and acidic wastewater generated during pyrolysis.

[0029] The deeply separated fibers are transported to the ultrasonic cleaning module 301. A cleaning solvent (such as an environmentally friendly organic solvent or an alkaline aqueous solution) is added to the cleaning tank inside the module. The cavitation effect generated by the ultrasonic generator removes soluble stains and pyrolysis residues (such as inorganic fillers) from the fiber surface.

[0030] The washed fiber and solvent mixture enters the vacuum filtration module 302, where the fiber and waste liquid are separated by vacuum filtration. The separated wet fiber is sent to the constant temperature drying module 303, where it is dried at a preset temperature (e.g., 80-120°C) to remove all moisture from the fiber surface and interior.

[0031] The dried fibers then enter the surface modification module 304. First, the fibers undergo low-temperature plasma activation in the module's plasma reaction chamber to introduce oxygen-containing active groups onto their surface. Subsequently, the activated fibers are immersed in a solution containing a silane coupling agent for chemical grafting. To achieve fiber orientation control during subsequent printing, in this embodiment, the chemical grafting step also includes a co-deposition step of magnetic nanoparticles (e.g., Fe3O4), anchoring the nanoparticles and coupling agent together on the fiber surface. After the grafting reaction is completed, regenerated fibers with functionalized surfaces are obtained and collected for subsequent 3D printing filament fabrication.

[0032] See attached document Figure 1 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after performing the macro-fragmentation step, a laser-assisted pretreatment step is performed.

[0033] The laser-assisted pretreatment step is performed in a laser-assisted pretreatment module 102. The laser-assisted pretreatment module 102, as part of the waste FRP disintegration system, receives material blocks from the macro-crushing module 101.

[0034] The laser-assisted preprocessing module 102 includes a laser source 102a, a beam transmission system 102b, a scanning galvanometer 102c, a three-dimensional processing platform 102d, a control unit 102e, and a dust collection device 102f. In this embodiment, the laser source 102a is a CO2 laser, as its wavelength is easily absorbed by the resin matrix.

[0035] The control unit 102e is electrically connected to the laser source 102a, the scanning galvanometer 102c, and the 3D machining platform 102d, respectively, and is used to set and execute machining commands. The beam transmission system 102b guides the laser beam emitted by the laser source 102a to the scanning galvanometer 102c. The dust collection device 102f is located above the 3D machining platform 102d and is equipped with a high-efficiency filtration system.

[0036] The operation process of laser-assisted pretreatment is as follows: the macro-crushed material block is fixed on the three-dimensional processing platform 102d.

[0037] The operator sets the processing parameters via the control unit 102e. These parameters include laser power, laser pulse frequency, scanning speed, and scanning path. The scanning path is set to etch a grid of grooves onto the surface of the material block to be processed.

[0038] The control unit 102e activates the laser source 102a, the scanning galvanometer 102c, and the dust collection device 102f. The laser beam reaches the scanning galvanometer 102c via the beam transmission system 102b, and is then controlled by the scanning galvanometer 102c to be focused on the surface of the material block and move along a preset scanning path.

[0039] The energy of the laser beam is absorbed by the resin matrix on the surface of the material block, causing thermal ablation of the resin matrix and forming gaseous products and tiny particles. During this process, the dust collection device 102f removes the dust generated by the ablation from the processing area.

[0040] The energy of the laser beam is absorbed by the resin matrix on the surface of the material block, causing thermal ablation of the resin matrix and forming gaseous products and tiny particles. During this process, the dust collection device 102f efficiently removes the dust generated by the ablation from the processing area.

[0041] By adjusting the combination of laser power and scanning speed, the input amount of laser energy per unit area (i.e., energy density) is controlled. This energy input is set to be higher than the ablation threshold of the resin matrix while lower than the damage threshold of the fiber material. The control unit 102e can also integrate a spectral analysis module to analyze the plasma spectrum of the ablation products and determine the ablation depth in real time, attempting to achieve closed-loop feedback control of the laser power. It should be noted that since the fiber-resin interface in FRP is not a microscopically flat surface, the real-time interpretation and feedback control of this spectral signal is highly complex in engineering, requiring high-speed response hardware and robust algorithm support, which is one of the technical challenges for achieving precise control in this module.

[0042] After completing one surface grooving operation, the control unit 102e drives the three-dimensional machining platform 102d to fine-tune the focal length in the vertical direction, or adjusts the focal length of the scanning galvanometer 102c to deepen the groove. The grooving operation is repeated until a microcrack network of predetermined depth is formed, causing stress concentration in the internal fiber structure.

[0043] After processing, a block with grooved surface and initially weakened internal structure is obtained. This block is then transferred to the low-energy dissociation and classification module 103 for further processing.

[0044] See attached document Figure 1 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after performing the laser-assisted pretreatment step, the low-energy dissociation and classification step is performed.

[0045] The low-energy dissociation and classification step is performed in a low-energy dissociation and classification module 103. The low-energy dissociation and classification module 103, as part of the waste FRP dissociation system, receives grooved blocks of material from the laser-assisted pretreatment module 102.

[0046] The low-energy dissociation and classification module 103 includes a grinding chamber 103a, a set of grinding media 103b, a drive motor 103c, a multi-stage classification unit 103d, and a control unit 103e. In this embodiment, the grinding chamber 103a is a horizontal drum mill, and the grinding media 103b is a high-density rubber or polyurethane grinding rod.

[0047] The control unit 103e is electrically connected to the drive motor 103c and is used to set and control the rotation speed and working time of the grinding chamber 103a. The multi-stage grading unit 103d is connected to the discharge port of the grinding chamber 103a, and the multi-stage grading unit 103d is equipped with a screen group with progressively smaller apertures from top to bottom.

[0048] The operation procedure for the low-energy dissociation and classification step is as follows: The material block from the laser-assisted pretreatment module 102 and the grinding media 103b are loaded into the grinding chamber 103a according to the preset media-material ratio.

[0049] The operator sets the grinding parameters through the control unit 103e. The grinding parameters include the rotational speed (ratio of revolution to rotational speed) of the grinding chamber 103a and the grinding duration.

[0050] Control unit 103e starts drive motor 103c, and grinding chamber 103a begins to rotate. During rotation, grinding media 103b continuously squeezes and kneads the material block. By precisely controlling the drum speed, the movement trajectory and energy of grinding media 103b can be adjusted. This action further breaks down the residual resin in the material block and loosens and separates the internal fiber bundles. The fiber length can be controlled by adjusting the grinding duration. It must be emphasized that this step uses a low-energy drum mill and flexible media precisely to avoid the catastrophic damage to fiber length caused by high-energy grinding equipment such as planetary ball mills. Therefore, setting grinding parameters (such as speed, time, and media-to-material ratio) is a crucial trade-off: ensuring sufficient dissociation of fiber bundles while maximizing the retention of average fiber length, as fiber length is a key factor affecting the final reinforcement effect of the composite material.

[0051] After the grinding operation is completed, the rotation of the grinding chamber 103a is stopped, and the mixture inside the chamber is unloaded into the multi-stage grading unit 103d. Under the action of the vibration device, the material passes through the screen group in sequence.

[0052] Fibers of different lengths are trapped by screens with different apertures and collected from the corresponding outlets. For example, fibers longer than the aperture of the first screen are collected from the first outlet, and fibers with lengths between the apertures of the first and second screens are collected from the second outlet.

[0053] Through low-energy dissociation and fractionation steps, regenerated fiber products with partitions of specific length ranges are obtained. These products are labeled and stored separately for use in subsequent fiber cleaning and surface activation regeneration steps.

[0054] See attached document Figure 2 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after completing the multi-stage controllable dissociation process, a resin deep pyrolysis and preliminary cleaning step is performed.

[0055] The deep pyrolysis and preliminary cleaning steps of the resin are performed in a resin pyrolysis module 201. The resin pyrolysis module 201 includes a sealed high-pressure resistant reaction chamber 201a, a microwave generator 201b, a reaction medium injection system 201c, a pressure and temperature sensing and control system 201d, a waste gas treatment interface 201e, a wastewater treatment interface 201f, and a main control unit 201g.

[0056] A microwave generator 201b is connected to a sealed, high-pressure resistant reaction chamber 201a and is used to apply a tunable microwave field to the interior of the chamber. A pressure and temperature sensing and control system 201d is used to monitor and regulate the pressure and temperature within the sealed, high-pressure resistant reaction chamber 201a. Exhaust gas treatment interface 201e and wastewater treatment interface 201f are connected to external exhaust gas treatment systems and wastewater treatment systems, respectively. The main control unit 201g is electrically connected to all components within the module.

[0057] The operation procedure for the deep resin pyrolysis and preliminary cleaning steps is as follows: the regenerated fiber product with residual resin from the low-energy dissociation and classification module 103 is loaded into the sealed high-pressure resistant reaction chamber 201a, and then the sealed high-pressure resistant reaction chamber 201a is sealed.

[0058] A measured amount of reaction medium is injected into the sealed, high-pressure resistant reaction chamber 201a through the reaction medium injection system 201c. In this embodiment, the reaction medium is water.

[0059] The operator sets the processing parameters via the main control unit 201g. These parameters include the target reaction temperature, target reaction pressure, microwave power, and processing time.

[0060] The main control unit 201g starts the microwave generator 201b. The microwave field acts on the reaction medium and residual resin on the fiber surface within the sealed, high-pressure reaction chamber 201a. Water rapidly heats up and vaporizes under the action of microwaves, forming a high-temperature, high-pressure water vapor environment. (Thanks to the pretreatment by module 102) The polar molecular bonds in the resin absorb microwave energy and react with the high-temperature water molecules, causing the chemical bonds to break and the polymer to decompose.

[0061] The pressure and temperature sensing control system 201d monitors the state inside the cavity in real time and feeds it back to the main control unit 201g. The main control unit 201g adjusts the output power of the microwave generator 201b according to the feedback data to realize programmed heating and constant pressure control of the reaction process, so that the temperature and pressure inside the cavity are maintained within the set value range.

[0062] Under set temperature and pressure, the reaction medium reacts with the resin pyrolysis products, further decomposing the residual polymer. The gaseous products generated during the pyrolysis process are discharged through the waste gas treatment interface 201e and enter the waste gas treatment system for condensation recovery or incineration.

[0063] Once the processing time reaches the set value, the main control unit 201g stops the operation of the microwave generator 201b. After the sealed high-pressure resistant reaction chamber 201a cools and depressurizes, the liquid products generated by the reaction are discharged through the wastewater treatment interface 201f and enter the wastewater treatment system for oil-water separation and purification.

[0064] The sealed, high-pressure resistant reaction chamber 201a is opened, and the treated fibers are removed. The treated fiber surface has only a small amount of inorganic filler and pyrolysis residue adhering to it. The removed fibers are then transferred to the ultrasonic cleaning module 301 for further processing.

[0065] See attached document Figure 3 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after performing the resin deep pyrolysis and preliminary cleaning steps, the fiber fine cleaning and drying steps are performed.

[0066] The fiber fine cleaning and drying steps are performed sequentially in an ultrasonic cleaning module 301, a vacuum filtration module 302, and a constant temperature drying module 303.

[0067] First, a fine cleaning operation is performed. The fibrous material from the resin pyrolysis module 201 is placed in the cleaning tank 301a of the ultrasonic cleaning module 301. Cleaning solvent is injected into the cleaning tank 301a until the fibrous material is completely submerged. The ultrasonic cleaning module 301 also includes an ultrasonic generator and a transducer connected to the cleaning tank 301a.

[0068] Start the ultrasonic generator and set the operating frequency and time. The transducer converts electrical energy into mechanical vibration, generating cavitation in the cleaning solvent. The formation and collapse of cavitation bubbles create microjets on the fiber surface, acting on the fiber surface to peel off and disperse pyrolysis residues and inorganic filler particles attached to the fiber surface. During the cleaning process, the cleaning solvent can be changed in stages, and mechanical stirring can be used to improve cleaning efficiency. After cleaning, a mixture containing fibers and suspended contaminants is obtained.

[0069] Next, a solid-liquid separation operation is performed. The mixture from the ultrasonic cleaning module 301 is introduced into the vacuum filtration module 302. The vacuum filtration module 302 includes a filter funnel with a filter membrane, a collection bottle, and a vacuum pump connected to the collection bottle.

[0070] The vacuum pump is activated, creating negative pressure inside the collection bottle. This pressure difference forces the liquid in the mixture through the filter membrane into the collection bottle, while fibers larger than the membrane pore size are trapped on the membrane surface, forming a moist fiber filter cake. The waste liquid in the collection bottle is then collected and treated.

[0071] Finally, the drying process is performed. The fiber filter cake obtained from the vacuum filtration module 302 is transferred to the drying chamber 303a of the constant temperature drying module 303. The constant temperature drying module 303 includes a heating element, a temperature sensor, and a control unit.

[0072] The operator sets the drying temperature and time via the control unit. Based on real-time feedback data from the temperature sensor, the control unit adjusts the power of the heating element to maintain the temperature inside the drying chamber 303a at the set value. Under constant temperature conditions, the moisture and residual solvent in the fiber filter cake evaporate.

[0073] After the drying time reaches the set value, heating is stopped. The material is removed from the drying chamber 303a, yielding dry, clean regenerated fibers. The regenerated fibers are collected for subsequent surface chemical modification steps.

[0074] See attached document Figure 3 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after performing the fiber fine cleaning and drying steps, the fiber surface chemical modification step is performed.

[0075] The fiber surface chemical modification step is performed in a surface modification module 304. Surface modification module 304 includes a plasma reaction unit 304a and a chemical grafting reaction unit 304b. The physical implementation of the chemical grafting reaction unit 304b is attached. Figure 3 The heating magnetic stirrer shown.

[0076] First, surface activation is performed. Dry, clean regenerated fibers from the constant-temperature drying module 303 are loaded into the vacuum reaction chamber of the plasma reaction unit 304a, and the reaction chamber is sealed. The vacuum system is activated to evacuate the pressure inside the reaction chamber to the preset background vacuum level.

[0077] A working gas is introduced into the vacuum reaction chamber. In this embodiment, the working gas is oxygen. An RF or microwave power supply is activated to excite the working gas within the vacuum reaction chamber, generating a low-temperature plasma. The regenerated fiber is exposed to the plasma environment for a predetermined treatment time. This operation forms oxygen-containing active groups on the fiber surface. After treatment, the pressure is released and the fiber is removed.

[0078] Next, the chemical grafting operation is performed. The plasma-activated fibers are placed into the reactor of the chemical grafting reaction unit 304b.

[0079] A silane coupling agent solution is prepared in a reaction vessel. The preparation process includes dissolving a specific type of silane coupling agent in a water-alcohol solvent and adjusting the pH of the solution to a preset value using a pH adjuster to promote the hydrolysis of the coupling agent.

[0080] As before, in order to control fiber orientation in the subsequent printing process, a pre-dispersed magnetic nanoparticle suspension is added to the solution in this step.

[0081] Start the heating and stirring functions of the chemical grafting reaction unit 304b. Heat the solution in the reactor to the set reaction temperature and turn on the magnetic stirrer to keep the fibers uniformly suspended in the solution.

[0082] The fibers are reacted in solution for a specified time under set temperature and pH conditions. This reaction process allows the hydrolyzed silane coupling agent molecules to form covalent chemical bonds with the active groups on the fiber surface. At the same time, the silane coupling agent can also chemically bond with the hydroxyl groups on the surface of the magnetic nanoparticles, thereby firmly anchoring the nanoparticles to the fiber surface through the chemical bridging effect of the coupling agent.

[0083] After the reaction is complete, heating and stirring are stopped. The fibers in the reactor are separated from the solution. The separated fibers are washed to remove unreacted coupling agent and free nanoparticles, and then dried again. The final product is regenerated fibers with surface grafted functional molecules and magnetic particles, which are used for the preparation of the second part of the 3D printing filaments.

[0084] See attached document Figure 4 , attached Figure 4 This is a process flow diagram for preparing recycled FRP-based 3D printing composite filaments according to an embodiment of the present invention. The preparation steps of the recycled FRP-based 3D printing composite filaments provided by the present invention begin with the steps of raw material compounding and pretreatment.

[0085] The raw material compounding and pretreatment steps are carried out in a raw material preparation system. The raw material preparation system includes a weighing unit 401, a pretreatment unit 402, and a mixing unit 403.

[0086] First, a predetermined mass of regenerated fibers from the surface modification module 304 is weighed using weighing unit 401. Then, a predetermined mass of nylon matrix resin chips is weighed using weighing unit 401. The mass ratio of the regenerated fibers to the PA6 matrix resin chips is set according to the performance requirements of the target composite wire. In this embodiment, the set mass ratio is 30:70.

[0087] In this embodiment, the pretreatment unit 402 is a vacuum drying oven. The weighed regenerated fibers and PA6 matrix resin slices are placed on different trays, and then the trays are placed together into the drying oven of the pretreatment unit 402.

[0088] Set the drying parameters and start vacuum drying. The drying temperature for the PA6 matrix resin chips was set to 80℃, and the drying time to 8 hours. The drying temperature for the regenerated fibers was set to 100℃, and the drying time to 2 hours. This rigorous vacuum drying pretreatment of the PA6 matrix resin chips and regenerated fibers is crucial to prevent hydrolytic degradation during the subsequent high-temperature melt extrusion process, which is essential for ensuring the mechanical properties of the composite filament.

[0089] In this embodiment, the mixing unit 403 is a high-speed mixer. After the drying step is completed, the dried regenerated fibers and dried PA6 matrix resin chips are taken out from the pretreatment unit 402 and immediately transferred to the mixing drum of the mixing unit 403.

[0090] Start the mixing unit 403, set the mixing speed and mixing time, and physically mix the two materials. This operation initially disperses the recycled fibers between the PA6 matrix resin chips, forming a macroscopically uniform mixture.

[0091] After mixing, a homogeneous mixture is obtained. The mixture is collected and sealed for storage, and used in subsequent multi-stage screw melt extrusion steps.

[0092] See attached document Figure 4 After the raw material compounding and pretreatment steps, the multi-stage screw melt extrusion step is performed.

[0093] The multi-stage screw melt extrusion step is performed in a melt extrusion module 404. The melt extrusion module 404 receives the mixture from the mixing unit 403.

[0094] The melt extrusion module 404 includes a loss-in-weight feeding unit 404a, a twin-screw extruder barrel 404b, a screw assembly 404c, a zoned heating and cooling system 404d, a drive motor 404e, a die head 404f, and a main control unit 404g.

[0095] The twin-screw extruder barrel 404b is sequentially divided into a feeding zone, a compression zone, a melting zone, a mixing zone, a venting zone, and a homogenization zone along the material conveying direction. The heating and cooling system 404d provides independent temperature control for each zone after the feeding zone. The screw assembly 404c is installed inside the twin-screw extruder barrel 404b and is driven to rotate by the drive motor 404e. The main control unit 404g is electrically connected to the feeding unit 404a, the heating and cooling system 404d, and the drive motor 404e.

[0096] The operation process of the multi-stage screw melt extrusion step is as follows: the mixture from the mixing unit 403 is added to the hopper of the feeding unit 404a.

[0097] The operator sets the extrusion process parameters through the main control unit 404g. The process parameters include: the feeding rate of the feeding unit 404a, the target temperature of each heating zone of the twin-screw extruder barrel 404b, and the rotational speed of the screw assembly 404c.

[0098] The main control unit 404g starts the feeding unit 404a, the heating and cooling system 404d, and the drive motor 404e. The mixture enters the twin-screw extruder barrel 404b from the feeding zone at a set rate.

[0099] The material is conveyed forward sequentially by the screw assembly 404c. In the compression and melting zones, the PA6 matrix resin chips are heated and melted. In the mixing zone, the screw assembly 404c employs an element arrangement that prioritizes transport and distribution mixing, supplemented by shear mixing. This involves using large-lead transport elements and staggered toothed mixing elements, rather than strong shear kneading blocks. The purpose of this design is to apply sufficient mixing to the melt, ensuring adequate dispersion of the regenerated fibers within the molten PA6 matrix, while minimizing fiber length shortening and damage caused by excessive shearing. Therefore, optimizing the screw assembly design is a crucial balance between ensuring effective dispersion and maximizing fiber length retention, and is key to determining wire performance. In the venting zone, a connected vacuum device extracts volatile gases from the melt. In the homogenization zone, the melt is further mixed to achieve a uniform temperature and component distribution.

[0100] Finally, the uniform composite melt is first passed through a melt gear pump to stabilize the melt pressure and eliminate extrusion pulsation, and then extruded through a die head 404f (e.g., a circular die orifice with a diameter of 1.75 mm or 2.85 mm) to form a continuous molten strip. The formed continuous molten strip is then sent to the wire forming and quality inspection system 405.

[0101] See attached document Figure 4 After the multi-stage screw melt extrusion step, the wire forming and quality inspection steps continue.

[0102] The wire forming and quality inspection steps are performed in a wire forming and quality inspection system 405. The wire forming and quality inspection system 405 receives continuous molten strips from the melt extrusion module 404.

[0103] The wire forming and quality inspection system 405 includes a cooling unit 405a, a diameter measuring unit 405b, a traction unit 405c, a winding unit 405d, and a control unit 405e. The cooling unit 405a, diameter measuring unit 405b, traction unit 405c, and winding unit 405d are arranged sequentially along the wire's forward direction. The control unit 405e is electrically connected to the diameter measuring unit 405b and the traction unit 405c, forming a closed-loop feedback control.

[0104] The operation flow for wire forming and quality inspection is as follows: The continuous molten strip extruded from the die 404f of the melt extrusion module 404 first enters the cooling unit 405a. In this embodiment, the cooling unit 405a is a circulating water bath, where the molten strip is cooled and solidified in water to form a wire.

[0105] The cured wire passes sequentially through the diameter measuring unit 405b and the traction unit 405c. The traction unit 405c pulls the wire forward at an initial speed. The diameter measuring unit 405b (e.g., a high-precision laser diameter gauge) measures the diameter of the passing wire in real time and sends the measurement data to the control unit 405e.

[0106] The control unit 405e employs a PID (Proportional-Integral-Derivative) control algorithm to compare the received real-time diameter measurement data with a preset target diameter value. When the measurement data deviates from the target diameter value, the control unit 405e precisely adjusts the traction speed of the traction unit 405c. When the measured diameter is greater than the target value, the control unit 405e increases the traction speed; when the measured diameter is less than the target value, the control unit 405e decreases the traction speed. This operation stabilizes the wire diameter near the target value, for example, within a tolerance range of ±0.03 mm.

[0107] The wire passing through the traction unit 405c is fed to the winding unit 405d. The winding unit 405d neatly winds the wire onto the spool. The rotational speed of the winding unit 405d is synchronized with the traction speed of the traction unit 405c via a tension sensor to ensure a smooth and constant tension during the winding process.

[0108] Ultimately, a spool of recycled FRP-based 3D printing composite filament with uniform diameter was obtained. The filament was used for the third part of the 3D printing process.

[0109] See attached document Figure 5 , attached Figure 5This is a schematic diagram of 3D printing based on recycled FRP according to an embodiment of the present invention. The 3D printing and performance control steps based on recycled FRP provided by the present invention begin with the establishment of a dedicated printing process parameter system for recycled materials.

[0110] The establishment of a dedicated printing process parameter system for recycled materials is performed within a 3D printing and performance control system. The system includes an FDM printer 501, a mechanical property testing unit 502, and a data analysis terminal 503.

[0111] First, the standard part model used to establish the parameter system is determined. In this embodiment, the selected standard part model is a tensile test strip designed according to the ASTM D638 standard. Simultaneously, the printing process parameters that need to be optimized are determined. In this embodiment, the selected process parameters include the printing nozzle temperature, heated bed temperature, printing speed, layer height, and infill density.

[0112] An orthogonal experimental design method was used to set multiple levels for the selected process parameters and generate an orthogonal experimental table. Each experimental combination corresponds to a specific set of printing parameter settings.

[0113] The recycled FRP-based 3D printing composite filament prepared in the second part was mounted on FDM printer 501. According to each set of parameters in the orthogonal experimental table, the corresponding number of tensile specimen strips were printed using FDM printer 501.

[0114] All printed tensile test strips are placed on the mechanical property testing unit 502 for testing. In this embodiment, the mechanical property testing unit 502 is a universal testing machine. Tensile strength is tested on each tensile test strip, and the maximum tensile strength value at fracture is recorded.

[0115] The tensile strength test data of all tensile specimens are entered into the data analysis terminal 503. In the data analysis terminal 503, range analysis or variance analysis is performed on the test results. Through analysis, the order of influence of each process parameter on tensile strength is determined, and the combination of process parameter levels that yields the highest tensile strength is identified.

[0116] This combination was identified as the dedicated printing process parameters for this recycled FRP-based 3D printing composite filament. The purpose of this step is to establish a material-process-performance database for the recycled FRP composite filament, and this parameter system is stored for use in subsequent 3D printing steps for high-performance components.

[0117] See attached document Figure 5In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after establishing a special printing process parameter system for recycled materials, the active control step of fiber orientation during the printing process is continued.

[0118] The active control step of fiber orientation during the printing process is performed in the 3D printing and performance control system. A fiber orientation control module 504 is added to the system. The fiber orientation control module 504 includes an electromagnet array 504a, a programmable DC power supply 504b, and an orientation control unit 504c.

[0119] An electromagnet array 504a is arranged around the outside of the print nozzle 501a of the FDM printer 501. A programmable DC power supply 504b is electrically connected to each electromagnet in the electromagnet array 504a. An orientation control unit 504c is electrically connected to the programmable DC power supply 504b and the main controller of the FDM printer 501.

[0120] The regenerated fibers used in this embodiment have been grafted with magnetic particles in the surface chemical modification steps described above.

[0121] The operational flow of the active fiber orientation control step is as follows: During the software slicing stage of print path planning, target fiber orientation angles are set for different areas of the component. The target orientation angle information and print path information are compiled together into machine-readable control instructions.

[0122] When printing begins, the main controller of the FDM printer 501 executes the printing path instruction and simultaneously sends the coordinates and motion vector information of the current printing nozzle 501a to the orientation control unit 504c.

[0123] The orientation control unit 504c calculates the direction and intensity of the magnetic field to be applied at the current position based on the received information and the preset fiber target orientation angle.

[0124] The orientation control unit 504c accordingly issues commands to the programmable DC power supply 504b. The programmable DC power supply 504b provides precise current to a specific combination of electromagnets in the electromagnet array 504a, thereby generating a magnetic field in a specific direction at the extrusion point of the print nozzle 501a.

[0125] When regenerated fibers containing magnetic particles are extruded from the printing nozzle 501a along with the molten matrix, the fibers rotate under the influence of the magnetic field torque until their axial direction aligns with the direction of the magnetic field. This alignment process is completed before the matrix material cools and solidifies. It is particularly noteworthy that this active control process presents significant physical challenges. First, the molten material in FDM printing cools and solidifies extremely rapidly after being extruded from the nozzle, leaving a very short time window for the fibers to complete their rotational alignment under the influence of the magnetic field torque. Second, the high viscosity of the molten matrix generates significant resistance to fiber rotation. To overcome this viscous resistance and achieve instantaneous reversal, an array of electromagnets capable of generating sufficient strength and high-speed direction changes needs to be integrated within the limited space of the printing nozzle. This places extremely high demands on hardware design, heat dissipation, and power control. However, it is precisely because this invention focuses on protecting the fiber aspect ratio in the preceding processes (such as the low-energy dissociation in the low-energy dissociation and grading module 103 and the low-shear extrusion in the melt extrusion module 404) that the necessary physical basis is provided for overcoming the aforementioned physical challenges and achieving effective magnetic field control.

[0126] During the movement of the printhead of the FDM printer 501, the orientation control unit 504c continuously updates the magnetic field direction, aligning the fibers in the newly deposited material according to a preset path. The orientation control unit 504c is deeply integrated with the slicing software, capable of reading magnetic field vector instructions defined in G-code for specific path segments (e.g., straight lines, corners, fills), thereby attempting to achieve regional control over the fiber arrangement within the component. Achieving ideal voxel-level precision control, constrained by the aforementioned physical conditions, is a key optimization goal of this system. Through this step, a reinforced component with a specific internal fiber arrangement is ultimately fabricated.

[0127] See attached document Figure 5 In the cross-scale controlled waste FRP recycling and 3D printing method provided by the present invention, after the active control step of fiber orientation during the printing process is performed, the forming and evaluation steps of the printed component are performed.

[0128] This step is completed using a 3D printing and performance control system. First, the 3D CAD model of the target component is input into the control software of the FDM printer 501.

[0129] In the software's slicing settings interface, input the established steps of the dedicated printing process parameters for recycled materials (including print nozzle temperature, heated bed temperature, and printing speed). Simultaneously, import the control strategy from the generated fiber orientation control module 504 based on the preset mechanical performance requirements of the target component.

[0130] Start the FDM printer 501 to execute the printing task. Following instructions containing specific process parameters and fiber orientation paths, the FDM printer 501 melt-deposits and regenerates the FRP-based 3D printing composite filament layer by layer, ultimately forming a three-dimensional solid component. After printing is complete, allow the heated bed to cool, then remove the formed component from the printing platform.

[0131] The removed molded component is sent to the evaluation process. The evaluation process uses a dimensional evaluation module 505, a mechanical property testing unit 502, and a microstructure analysis module 506.

[0132] The dimensional accuracy of the component is evaluated in the dimensional evaluation module 505. In this embodiment, the dimensional evaluation module 505 is a 3D laser scanner. The 3D laser scanner is used to scan the formed component to obtain point cloud data. The point cloud data is compared with the original 3D CAD model to calculate the dimensional error of the formed component.

[0133] The mechanical properties of the component are evaluated in the mechanical property testing unit 502. A standard specimen is cut from the molded component, or the component itself is tested directly. In this embodiment, a three-point bending strength test is performed on the component, and its bending strength and bending modulus data are recorded.

[0134] The internal structure of the component is evaluated in the microstructure analysis module 506. In this embodiment, the microstructure analysis module 506 is a scanning electron microscope. Metallographic samples are cut from specific locations on the component, and the cross-section of the samples is observed under the scanning electron microscope to analyze the actual distribution, orientation angle, and interfacial bonding between the internal regenerated fibers and the matrix resin.

[0135] The data generated from all evaluation steps are aggregated to form a comprehensive performance report of the printed component, and fed back to the data analysis terminal 503 and slicing software for further optimization of the printing process parameter system and fiber orientation control strategy, forming a closed-loop control system for manufacturing evaluation and optimization.

Claims

1. A method for cross-scale controlled recycling and 3D printing of waste FRP, characterized in that, Includes the following steps: S1. Perform the pretreatment and high-quality fiber recycling steps of waste FRP: Perform a multi-stage controllable dissociation process to obtain recycled fibers with length distribution from waste FRP. The multi-stage controllable dissociation process specifically includes: macroscopically crushing the waste FRP components through a macroscopic crushing module to obtain material blocks; The material block is pretreated by laser-assisted pretreatment module to engrave deep grid-like grooves on the resin matrix, thereby obtaining small material blocks of uniform size. The pre-treated material blocks are subjected to low-energy dissociation and classification through a low-energy dissociation and classification module. A horizontal drum mill containing flexible grinding media is used to dissociate the material blocks at a low grinding time and speed. The dissociation products are classified through a multi-level classification unit with multiple layers of screens with different apertures, thereby realizing cross-scale sorting of the recycled fibers. S2. Perform fiber cleaning and surface activation regeneration steps: Clean, dry, and chemically modify the recycled fibers obtained in step S1, specifically including the following steps: The recycled fibers are subjected to resin pyrolysis treatment under microwave heating using a resin pyrolysis module. The pyrolyzed fibers are ultrasonically cleaned using an ultrasonic cleaning module, dried after cleaning, and then plasma activated in a surface modification module. The recycled fibers that have undergone plasma activation are immersed in a solution containing silane coupling agent and magnetic nanoparticles to carry out a chemical grafting reaction, so that the silane coupling agent and the magnetic nanoparticles are chemically bonded and anchored to the surface of the recycled fibers, thereby obtaining regenerated fibers with magnetic nanoparticles anchored to the surface. S3. Perform the preparation steps of recycled FRP-based 3D printing composite filament: Mix the recycled fiber with magnetic nanoparticles anchored on the surface obtained in step S2 with the matrix resin, and prepare the composite filament through melt extrusion, filament forming and quality inspection. In the wire forming and quality inspection step, the diameter of the extruded wire is measured in real time by the diameter measuring unit, and the traction speed of the traction unit is adjusted by the control unit to achieve closed-loop feedback control of the diameter of the composite wire. S4. Steps for establishing a dedicated printing process parameter system for recycled materials: Print standard samples using the composite filament obtained in step S3, and test the standard samples to determine the printing process parameters; The test specifically involves: performing a tensile strength test on the standard samples using a mechanical property testing unit; The determination of the printing process parameters specifically involves: analyzing the test data of the tensile strength test using a data analysis terminal to determine the optimal combination of printing process parameters. S5. Perform 3D printing molding step: Use the printing process parameters determined in step S4 and the composite filament obtained in step S3 to perform fused deposition modeling printing, and apply an external magnetic field to control the orientation of the regenerated fibers in the extruded composite filament melt to obtain a three-dimensional solid component with internal fibers arranged in a preset manner.

2. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, In the laser-assisted pretreatment step, by controlling the output power, scanning speed and scanning path of the laser, the laser beam is made to carve deep grid-like grooves on the resin matrix along the surface of the material block.

3. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 2, characterized in that, The laser-assisted pretreatment module uses a CO2 laser as the laser source. By adjusting the combination of laser power and scanning speed, the laser energy input per unit area is controlled to be higher than the ablation threshold of the resin matrix and lower than the damage threshold of the fiber material.

4. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, The resin pyrolysis treatment under microwave heating in step S2 is specifically as follows: Water is introduced into a sealed, high-pressure reaction chamber as a reaction medium. Polar resin molecules are heated by microwaves, causing the water to vaporize under the action of microwaves, forming a high-temperature and high-pressure water vapor environment, which causes the resin remaining on the fiber surface to undergo hydrothermal decomposition.

5. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, In the ultrasonic cleaning stage of step S2, the cavitation effect generated by the ultrasonic generator peels off the pyrolysis residue and inorganic filler particles on the fiber surface, and then the cleaned wet fiber is separated from the waste liquid by vacuum filtration.

6. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, The melt extrusion step in step S3 is carried out using a twin-screw extruder, and the screw assembly of the twin-screw extruder adopts a component arrangement that is mainly for conveying and distributing mixing, and secondarily for shear mixing.

7. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 6, characterized in that, The barrel of the twin-screw extruder is divided into a feeding zone, a compression zone, a melting zone, a mixing zone, a venting zone, and a homogenization zone along the material conveying direction. The mixing zone uses large-lead conveying elements and staggered toothed mixing elements.

8. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, In step S3, the control unit uses a PID control algorithm to compare the received real-time diameter measurement data with the preset target diameter value and precisely adjust the traction speed of the traction unit to keep the diameter of the wire within the set tolerance range.

9. The method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 1, characterized in that, The orientation control in step S5 is achieved through a fiber orientation control module, which includes an array of electromagnets arranged outside the print nozzle of the fused deposition modeling printer. The array of electromagnets is controlled by an orientation control unit, which is electrically connected to the main controller of the fused deposition modeling printer for synchronizing print path information.

10. A method for cross-scale controlled recycling and 3D printing of waste FRP according to claim 9, characterized in that, The execution process of the orientation control includes: During the printing path planning stage, preset fiber target orientation angles for different areas of the component; During printing, the orientation control unit calculates and drives the electromagnet array to generate a magnetic field in the corresponding direction based on the real-time position and motion vector of the printing nozzle and the preset fiber target orientation angle through a built-in control algorithm. This causes the regenerated fibers with magnetic nanoparticles in the melt extruded from the nozzle to align along the magnetic field direction under the action of the magnetic field torque.

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