4D printing system and method of a configurable bionic energy-absorbing honeycomb structure

Abstract

The present application relates to the field of intelligent protection, and particularly relates to a 4D printing system and method of a bionic energy-absorbing honeycomb structure with adjustable configuration, which can consider deformation and efficient energy absorption when facing different collision conditions, fully protect the integrity of the passenger cabin or cargo cabin, and effectively reduce the injury of passengers or goods. The printing device contains a double-material extrusion system, a control system and a dynamic forming platform. The double-material extrusion system integrates a digital magnetic control system with an auxiliary magnetic field material extrusion system. In the printing process, by planning the printing path and applying a magnetic field, a patterned ferromagnetic domain pattern can be obtained while forming a complex honeycomb structure. Under the coupling effect of a high-frequency induction heater and a driving magnetic field, combined with the dynamic chemical properties of the base material, the obtained honeycomb structure can adjust the cell structure and material stiffness of the honeycomb material to cope with different collision conditions, realize active intelligent protection, and has great application potential in the field of transportation.

Description

Technical Field

[0001] This invention relates to the field of intelligent protection, and in particular to a 4D printing method for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under complex impact conditions. Background Technology

[0002] Automotive pre-collision technology combines the environmental perception capabilities of active safety technologies with the protective functions of passive safety systems. It optimizes passive safety devices before a collision occurs, thereby enhancing protection. It integrates the target detection and recognition functions of active safety technologies with the protective functions of passive safety devices. Using a reasonable collision prediction algorithm, it pre-determines whether an unavoidable collision will occur and optimizes passive safety devices in advance to achieve optimal protection during the collision. However, traditional optimization measures, including airbag deployment algorithm optimization and seatbelt pretensioning, are limited in scope and have low protective efficiency. In particular, automotive energy-absorbing protective devices cannot intelligently adjust their energy-absorbing stiffness and energy absorption based on the predicted collision situation. Therefore, there is an urgent need to develop a high-efficiency, intelligent, and adjustable energy-absorbing device for protection under complex operating conditions, intelligently addressing collision protection under high, medium, and low speed conditions. Summary of the Invention

[0003] To address the lack of intelligent active tuning technology in the passive safety systems of existing automotive pre-collision technologies when facing complex collision situations, this invention provides a 4D printing method for biomimetic energy-absorbing honeycomb structures with adjustable configurations under complex loads.

[0004] The key advantage of this invention is the use of a smart resin-based composite material to create a programmable geometric shape and adjustable material properties through magnetically assisted photopolymerization 3D printing technology. This component senses the action of an external coupled magnetic field and adjusts its predefined geometric shape. Simultaneously, at a certain high temperature, the shape of the component is fixed. This energy-absorbing protective component, combining adjustments to the material's mechanical properties with real-time structural programming, exhibits significant energy absorption effects when dealing with complex collision loads.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration, comprising:

[0007] The dual-material extrusion system is used to extrude a matrix photosensitive resin material and a photosensitive resin precursor material containing magnetic reinforcing particles in real time at a certain extrusion speed. The extrusion heads of the single-material extrusion system and the material extrusion system with the auxiliary magnetic field work together to deposit the photosensitive resin precursor material with or without reinforcing particles along a certain printing path on the dynamic molding platform.

[0008] The control system controls the coordinated operation of the single-material extrusion system and the auxiliary magnetic field material extrusion system in the dual-material extrusion system, enabling timely alternating extrusion of a single photosensitive resin material and a photosensitive resin containing magnetic reinforcing particles; it controls the magnetic field strength, working time, and working mode of the digital magnetic control system in the auxiliary magnetic field material extrusion system; it controls the movement of the dynamic molding platform in three-dimensional space; and it controls the light intensity and switching time of the photocuring system.

[0009] The dynamic forming platform is an important component of 3D printing equipment. It can move in any form, such as straight lines or curves, in the horizontal plane and can also move up and down in the vertical direction. The dual-material extrusion system and the dynamic forming platform work together to deposit precursor materials with uniform magnetic polarity particles onto the dynamic forming platform as needed. Combined with the movement of the dynamic forming platform in three-dimensional space, it can achieve the molding and manufacturing of honeycomb structures with patterned magnetic domain distribution.

[0010] Furthermore, the dual-material extrusion system includes:

[0011] A single-material extrusion system is used to selectively deposit photosensitive resin precursor material without magnetic reinforcing particles onto a dynamic molding platform according to a certain printing path and printing speed.

[0012] The auxiliary magnetic field material extrusion system is used to selectively deposit photosensitive resin precursor material containing magnetic reinforcing particles onto a dynamic molding platform according to a certain printing path and printing speed. During the printing process, a digital magnetic control system is integrated. Under the action of Lorentz force, the magnetic particles produce controllable directional assembly. After the material is extruded and deposited, the magnetic polarity of the particles is still retained. By changing the direction of the applied magnetic field or the printing path, magnetic domains in the local space can be planned.

[0013] The UV curing system is integrated into the extruder as a spotlight, with a light intensity of 1000-1400 mW / cm². 2 The irradiation distance is 10-30mm and the spot diameter is 2-10mm. It is used to initially solidify the material deposited on the dynamic forming platform and to anchor the magnetic polarity of the particles.

[0014] The material extrusion system with an auxiliary magnetic field shares some of the same hardware components as the single-material extrusion system, including:

[0015] The extra-long material extrusion head extrudes the printing material inside the material cylinder. Its interior is a hollow cylindrical structure with an inner diameter of 0.84-1.80mm and a length of 20-50mm.

[0016] The material cylinder, with an extra-long material extrusion head attached below, is coaxially mounted with the material pusher and is used to hold the printing material;

[0017] Fixed support, used for dual-material extrusion systems, dynamic molding platforms and control systems;

[0018] The material pusher is used to extrude the printing material from the material cylinder and deposit it onto the dynamic forming platform through an ultra-long material extrusion head;

[0019] The difference between the material extrusion system with an auxiliary magnetic field and the single material extrusion system is that the material extrusion system with an auxiliary magnetic field has a digital magnetic control system, while the single material extrusion system does not have a digital magnetic control system.

[0020] The digital magnetic control system can adjust the direction of the applied magnetic field parallel to or opposite to the long axis direction of the ultra-long material extruder in real time according to the predefined magnetic domain distribution of the material. The magnetic polarity in the deposition material channel can be adjusted by switching the direction of the applied magnetic field or changing the printing direction. The magnetic field strength is usually set to 15-65mT. Using this method, complex ferromagnetic domain patterns can be encoded into complex honeycomb materials.

[0021] The digital magnetic control system also includes a magnetic shielding structure installed at the lower end of the ultra-long material extrusion head to attenuate the influence of the magnetic flux density at the lower end of the ultra-long material extrusion head on the magnetic polarity within the deposition material channel.

[0022] A 4D printing method for a 4D printing structure with an adjustable configuration, utilizing the aforementioned tunable biomimetic energy-absorbing honeycomb structure, includes the following steps:

[0023] Composition and preparation of the S101 printing material system:

[0024] Matrix material 55-95 vol%: Dimethacrylate and polypropylene glycol acrylate were mixed in a molar ratio of 1:1.8-2.2 to prepare a liquid printing precursor, followed by the introduction of 2.5-3.5% of the photoinitiator diacylphosphine oxide 819 and 0.05% of the light absorber Sudan III;

[0025] Magnetic reinforcing particles 5-45 vol%: 60-70 wt% iron oxide, 30-40 wt% neodymium iron boron;

[0026] After the above components are mixed in proportion, the precursor mixture solution is magnetized under a pulsed magnetic field of about 2.0-3.0T.

[0027] S102 energy absorption component model biomimetic design:

[0028] Inspired by the honeycomb structure inside the peel of a ripe grapefruit with high impact resistance, a biomimetic impact-resistant honeycomb material was designed. The initial unit cell structure of the honeycomb material is hexagonal, with a cell wall thickness of 0.1-0.55 mm and a sidewall length of 9-14 mm. Under the action of a coupled magnetic field, the mechanical properties of the honeycomb material will change with temperature, and its geometric shape will also undergo plastic or permanent deformation, thereby realizing the programmable adjustment of the stiffness and energy absorption characteristics of the honeycomb structure.

[0029] S103 Magnetic-Assisted Photopolymerization 3D Printing:

[0030] Based on magnetic-assisted photopolymerization 3D printing equipment, complex honeycomb structures are formed. During printing, the external magnetic field is combined to construct a patterned magnetic domain distribution inside the honeycomb material.

[0031] The specific steps are as follows:

[0032] ① Model establishment: To establish an efficient impact-resistant honeycomb structure model, it is necessary to clarify the magnetic domain distribution in each part of the honeycomb structure;

[0033] ② Slicing: Slicing is performed using professional 3D printing software to obtain selective photocuring cross-sectional information of each slice layer, magnetic field direction information of the digital magnetocontrol system, magnetic field strength (15-65mT) and magnetic field duration, photocuring switch switching time and power;

[0034] ③Magnetic-assisted photopolymerization 3D printing: The matrix materials in S101 that do not contain magnetic reinforcing particles and those that do contain magnetic reinforcing particles are transferred into a single material extrusion system and an auxiliary magnetic field material extrusion system, respectively. Then, according to the process flow and printing parameters obtained in step 3, the honeycomb structure is formed and its internal magnetic domain orientation is accumulating layer by layer to form a three-dimensional honeycomb structure.

[0035] ④ Post-processing: The formed three-dimensional honeycomb structure is placed in an ultraviolet curing chamber for further curing, and the curing time is 10-24 hours;

[0036] 4D transformation of S104 honeycomb structure:

[0037] Plastic deformation: First, a high-frequency induction heater with a magnetic induction coil is used to induce the iron oxide particles to vibrate at high frequency to generate heat. The power is 15-35KW and the time is 7-15s, which causes the printed honeycomb structure to heat up to 75-85℃. Then, a driving magnetic field is applied with a magnetic field strength of 200-500mT. The honeycomb structure induces the overall deformation of the printed part according to the pre-set magnetic domain distribution pattern in the material.

[0038] Permanent deformation: Based on plastic deformation, a high-power high-frequency induction heater is applied, with a power of 35-60KW and a time of 5-15s, to make the overall temperature of the honeycomb structure reach 116-125℃.

[0039] The present invention has the following beneficial effects:

[0040] Firstly, a patterned magnetic domain distribution 3D printing system and method based on a multi-material extrusion system has been developed, which can realize high-resolution pixelated magnetic polarity integrated molding.

[0041] Secondly, this invention proposes that the photosensitive resin material in the 3D printing method possesses dynamic chemical characteristics. By controlling the temperature, different covalent bond exchange mechanisms can be triggered, enabling on-demand control of the material's shape and properties after printing. At lower temperatures (75-85℃), dynamic bond exchange occurs between hindered urea bonds, endowing the material with the ability to undergo plastic deformation in the solid state, exhibiting abundant plastic deformation capacity. At higher temperatures (116-125℃), hindered urea bonds react with hydroxyl groups on the side chains, achieving network topological heterogeneity, and significantly enhancing the material's mechanical properties.

[0042] Thirdly, based on a photosensitive resin matrix with dynamic chemical properties and a patterned magnetic domain distribution, the present invention can produce reversible plastic deformation under the action of a low-power high-frequency induction heater, which can be used for low-speed impact protection; under the action of a high-power high-frequency induction heater, a higher temperature is generated, resulting in permanent deformation and a significant increase in material stiffness, which can be used for high-speed impact protection. Attached Figure Description

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0044] Figure 1 This is a schematic diagram of the system configuration of the present invention.

[0045] Figure 2 This is the initial state of the honeycomb structure described in the 4D printing method for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under complex impact conditions according to the present invention.

[0046] Figure 3 This invention relates to a magnetically assisted 3D printing extrusion system for a 4D printing method of biomimetic energy-absorbing honeycomb structures with adjustable configuration under complex impact conditions. During the extrusion process from an ultra-long material extruder, the magnetic particles within the matrix material undergo directional assembly along the printing path under the influence of a digital magnetic control system.

[0047] Figure 4 The distribution of the printing material and the magnetic domain pattern (arrow direction is N pole) of the single cell printing material in the 4D printing method of the present invention for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under complex impact conditions.

[0048] Figure 5This is the deformed state of the anti-collision honeycomb structure under high-speed driving, as described in the 4D printing method of the present invention for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under complex impact conditions.

[0049] The reference numerals in the figure are:

[0050] Dual-material extrusion system 1, control system 2, dynamic molding platform 3;

[0051] 11. Single material extrusion system; 12. Material extrusion system with auxiliary magnetic field; 13. Photocuring system;

[0052] Extra-long material extrusion head 111, material cylinder 112, fixed bracket 113, material pusher 114;

[0053] Digital magnetic control system 121, magnetic shielding structure 122. Detailed Implementation

[0054] The technical solutions of 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.

[0055] This invention addresses the problem of the lack of intelligent active tuning technology in automotive energy-absorbing protective devices within passive safety systems for complex collision scenarios. For detailed technical solutions, please refer to [link / reference needed]. Figure 1 As shown, a 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration includes:

[0056] The dual-material extrusion system 1 is used to extrude a matrix photosensitive resin material and a photosensitive resin precursor material containing magnetic reinforcing particles in real time at a certain extrusion speed. The single-material extrusion system 11 and the extrusion head 22 of the material extrusion system with auxiliary magnetic field cooperate and work together to deposit the photosensitive resin precursor material containing or without reinforcing particles onto the dynamic molding platform 3 along a certain printing path.

[0057] Control system 2 is used to control the coordinated operation of single material extrusion system 11 and auxiliary magnetic field material extrusion system 12 in dual material extrusion system 1, so as to realize the timely alternating extrusion of single photosensitive resin material and photosensitive resin containing magnetic reinforcing particles; control the magnetic field strength, working time and working mode of digital magnetic control system 121 in auxiliary magnetic field material extrusion system 12; control the movement of dynamic molding platform 3 in three-dimensional space; and control the light intensity and switching time of photocuring system 13.

[0058] The dynamic forming platform 3 is an important component of the 3D printing equipment. It can move in any form, such as straight lines or curves, in the horizontal plane and can also move vertically. The dual-material extrusion system 1 and the dynamic forming platform 3 work together to deposit precursor material with uniformly magnetically polarized particles onto the dynamic forming platform 3 as needed. Combined with the movement of the dynamic forming platform 3 in three-dimensional space, it achieves the molding and manufacturing of a honeycomb structure with patterned magnetic domain distribution.

[0059] Furthermore, the dual-material extrusion system 1 includes:

[0060] A single-material extrusion system 11 is used to selectively deposit a photosensitive resin precursor material without magnetic reinforcing particles onto a dynamic molding platform 3 according to a certain printing path and printing speed.

[0061] The auxiliary magnetic field material extrusion system 12 is used to selectively deposit photosensitive resin precursor material containing magnetic reinforcing particles onto the dynamic molding platform 3 according to a certain printing path and printing speed. During the printing process, a digital magnetic control system 121 is integrated. Under the action of Lorentz force, the magnetic particles produce controllable directional assembly. After the material is extruded and deposited, the magnetic polarity of the particles is still retained. By changing the direction of the applied magnetic field or the printing path, magnetic domains in the local space can be planned.

[0062] The UV curing system 13 is integrated into the extruder as a spotlight, with a light intensity of 1000-1400 mW / cm². 2 The irradiation distance is 10-30mm and the spot diameter is 2-10mm. It is used to initially solidify the material deposited on the dynamic forming platform 3 and realize the anchoring of the magnetic polarity of the particles.

[0063] The auxiliary magnetic field material extrusion system 12 has some of the same hardware components as the single material extrusion system 11, including:

[0064] The extra-long material extrusion head 111 is used to extrude the printing material inside the material cylinder 112. The material inside the extra-long material extrusion head 111 has a hollow cylindrical structure with an inner diameter of 0.84-1.80mm and a length of 20-50mm.

[0065] The material cylinder 112 is connected to an extra-long material extrusion head 111, which is coaxially mounted with the material pusher 114 and is used to hold printing material;

[0066] Fixed bracket 113, which is used for dual material extrusion system 1, dynamic molding platform 3 and control system 2;

[0067] Material pusher 114 is used to extrude the printing material in material cylinder 112 and deposit it on dynamic molding platform 3 through extra-long material extrusion head 111;

[0068] The difference between the material extrusion system 12 with the auxiliary magnetic field and the single material extrusion system 11 is that the material extrusion system 12 with the auxiliary magnetic field has a digital magnetic control system 121, while the single material extrusion system does not have a digital magnetic control system 121.

[0069] The digital magnetic control system 121 can adjust the direction of the applied magnetic field parallel (or opposite) to the long axis of the ultra-long material extrusion head 111 in real time according to the predefined magnetic domain distribution of the material. The magnetic polarity in the deposition material channel can be adjusted by switching the direction of the applied magnetic field or changing the printing direction. The magnetic field strength is usually set to 15-65mT. Using this method, complex ferromagnetic domain patterns can be encoded into complex honeycomb materials.

[0070] The digital magnetic control system 121 is further provided with a magnetic shielding structure 122, which is installed at the lower end of the ultra-long material extrusion head 111 to attenuate the influence of the magnetic flux density at the lower end of the ultra-long material extrusion head 111 on the magnetic polarity in the deposition material channel.

[0071] A 4D printing method for a 4D printing structure with an adjustable configuration, utilizing the aforementioned tunable biomimetic energy-absorbing honeycomb structure, includes the following steps:

[0072] Composition and preparation of the S101 printing material system:

[0073] Matrix material 55-95 vol%: Dimethacrylate and polypropylene glycol acrylate were mixed in a molar ratio of 1:1.8-2.2 to prepare a liquid printing precursor, followed by the introduction of 2.5-3.5% of the photoinitiator diacylphosphine oxide 819 and 0.05% of the light absorber Sudan III;

[0074] Magnetic reinforcing particles 5-45 vol%: 60-70 wt% iron oxide, 30-40 wt% neodymium iron boron;

[0075] After the above components are mixed in proportion, the precursor mixture solution is magnetized under a pulsed magnetic field of about 2.0-3.0T.

[0076] S102 energy absorption component model biomimetic design:

[0077] Inspired by the honeycomb structure inside the peel of a ripe grapefruit with high impact resistance, a biomimetic impact-resistant honeycomb material was designed. The initial unit cell structure of the honeycomb material is hexagonal, with a cell wall thickness of 0.1-0.55 mm and a sidewall length of 9-14 mm. Under the action of a coupled magnetic field, the mechanical properties of the honeycomb material will change with temperature, and its geometric shape will also undergo plastic or permanent deformation, thereby realizing the programmable adjustment of the stiffness and energy absorption characteristics of the honeycomb structure.

[0078] S103 Magnetic-Assisted Photopolymerization 3D Printing:

[0079] Based on magnetic-assisted photopolymerization 3D printing equipment, complex honeycomb structures are formed. During printing, the external magnetic field is combined to construct a patterned magnetic domain distribution inside the honeycomb material.

[0080] The specific steps are as follows:

[0081] ① Model establishment: To establish an efficient impact-resistant honeycomb structure model, it is necessary to clarify the magnetic domain distribution in each part of the honeycomb structure;

[0082] ② Slicing: Slicing is performed using professional 3D printing software to obtain selective photocuring cross-sectional information of each slice layer, magnetic field direction information of the digital magnetocontrol system 121, magnetic field strength (5-65 mT) and magnetic field duration, photocuring switch switching time and power;

[0083] ③Magnetic-assisted photopolymerization 3D printing: The matrix materials in S101 that do not contain magnetic reinforcing particles and those that do contain magnetic reinforcing particles are transferred into the single material extrusion system 11 and the material extrusion system 12 with the auxiliary magnetic field, respectively. Then, according to the process flow and printing parameters obtained in step 3, the honeycomb structure is formed and its internal magnetic domain orientation is accumulating layer by layer to form a three-dimensional honeycomb structure.

[0084] ④ Post-processing: The formed three-dimensional honeycomb structure is placed in an ultraviolet curing chamber for further curing, and the curing time is 10-24 hours;

[0085] 4D transformation of S104 honeycomb structure:

[0086] Plastic deformation: First, a high-frequency induction heater with a magnetic induction coil is used to induce high-frequency vibration of iron oxide particles to generate heat. The power is 15-35KW and the time is 7-15s, which causes the printed honeycomb structure to heat up to 75-85℃. Then, a driving magnetic field with a magnetic field strength of 200-500mT is applied. The honeycomb structure induces the overall deformation of the printed part according to the pre-set magnetic domain distribution pattern in the material.

[0087] Permanent deformation: Based on plastic deformation, a high-power high-frequency induction heater (35-60KW) is applied for 5-15s to make the overall temperature of the honeycomb structure reach 116-125℃.

[0088] A more preferred first embodiment of the method relating to this application—a 4D printing method for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under low-velocity impact—is as follows:

[0089] Matrix material 55-95 vol%: Dimethacrylate and polypropylene glycol acrylate were mixed in a molar ratio of 1:1.8-2.2 to prepare a liquid printing precursor, followed by the introduction of 2.5-3.5% of the photoinitiator diacylphosphine oxide 819 and 0.05% of the light absorber Sudan III;

[0090] Magnetic reinforcing particles 5-45 vol%: 60-70 wt% iron oxide, 30-40 wt% neodymium iron boron;

[0091] After the above components are mixed in proportion, the precursor mixture solution is magnetized under a pulsed magnetic field of about 2.7T.

[0092] Design and model a biomimetic impact-resistant honeycomb material, where the initial unit cell structure of the honeycomb material is hexagonal. Figure 2 The cell wall thickness is 0.2 mm and the lateral wall length is 10 mm.

[0093] The 3D printing software was used to slice the material, obtaining selective photocuring cross-sectional information for each slice layer, magnetic field direction information of the digital magnetron sputtering system 121, magnetic field strength of 50 mT, and magnetic field duration. The light intensity of the photocuring system 13 was 1200 mW / cm². 2 The irradiation distance is 20mm and the spot diameter is 50mm;

[0094] The matrix materials containing and without magnetic reinforcing particles are respectively transferred into a single-material extrusion system 11 and an auxiliary magnetic field material extrusion system 12, and then sliced ​​to obtain the process flow and printing parameters for honeycomb structure forming and internal magnetic domain orientation. Figure 3 and Figure 4 Layer by layer, they accumulate to form a three-dimensional honeycomb structure;

[0095] The formed three-dimensional honeycomb structure is placed in an ultraviolet curing chamber for further curing, with a curing time of 10-24 hours.

[0096] Finally, a high-frequency induction heater with a magnetic induction coil is used to induce high-frequency vibration of the iron oxide particles to generate heat. The power is 25KW and the time is 10s, which causes the printed honeycomb structure to heat up to 75℃. Then, a driving magnetic field with a magnetic field strength of 400mT is applied. The honeycomb structure induces the overall deformation of the printed part according to the pre-set magnetic domain distribution pattern in the material. Figure 4 ).

[0097] A more preferred second embodiment of the method relating to this application—a 4D printing method for a biomimetic energy-absorbing honeycomb structure with adjustable configuration under high-speed impact—is as follows:

[0098] Matrix material 55-95 vol%: Dimethacrylate and polypropylene glycol acrylate were mixed in a molar ratio of 1:1.8-2.2 to prepare a liquid printing precursor, followed by the introduction of 2.5-3.5% of the photoinitiator diacylphosphine oxide 819 and 0.05% of the light absorber Sudan III;

[0099] Magnetic reinforcing particles 5-45 vol%: 60-70 wt% iron oxide, 30-40 wt% neodymium iron boron;

[0100] After the above components are mixed in proportion, the precursor mixture solution is magnetized under a pulsed magnetic field of about 3.0T.

[0101] Design and model a biomimetic impact-resistant honeycomb material. The initial unit cell structure of the honeycomb material is hexagonal, with a cell wall thickness of 0.4 mm and a sidewall length of 12 mm.

[0102] The 3D printing software was used to slice the material, obtaining selective photocuring cross-sectional information for each slice layer, magnetic field direction information of the digital magnetron sputtering system 121, magnetic field strength of 50 mT, and magnetic field duration. The light intensity of the photocuring system 13 was 1200 mW / cm². 2 The irradiation distance is 20mm and the spot diameter is 50mm;

[0103] The matrix materials containing and without magnetic reinforcing particles are respectively transferred into a single material extrusion system 11 and a material extrusion system 12 with an auxiliary magnetic field. Then, according to the process flow and printing parameters obtained from the slice, the honeycomb structure is formed and its internal magnetic domain orientation is formed. Layer by layer, a three-dimensional honeycomb structure is formed.

[0104] The formed three-dimensional honeycomb structure was placed in an ultraviolet curing chamber for further curing, which took 20 hours.

[0105] 4D Deformation: First, a high-frequency induction heater with a magnetic induction coil induces high-frequency vibration of the iron oxide particles to generate heat. The power is 25KW, and the duration is 8s, causing the printed honeycomb structure to heat up to 80℃. Then, a driving magnetic field with a strength of 250mT is applied, inducing overall deformation of the printed part according to the pre-defined magnetic domain distribution pattern within the material. Building upon this plastic deformation, a high-power high-frequency induction heater (50KW) is further applied for 5s, causing the overall temperature of the honeycomb structure to reach 120℃. This transforms the plastic deformation into permanent deformation, significantly improving the material's stiffness.

Claims

1. A 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration, characterized in that, include: The dual-material extrusion system (1) is used to extrude the matrix photosensitive resin material and the photosensitive resin precursor material containing magnetic reinforcing particles at a certain extrusion speed in real time. The single-material extrusion system (11) and the extrusion head (22) of the material extrusion system with auxiliary magnetic field cooperate and work together to deposit the photosensitive resin precursor material containing or without reinforcing particles on the dynamic molding platform (3) along a certain printing path. The control system (2) is used to control the single material extrusion system (11) and the auxiliary magnetic field material extrusion system (12) in the dual material extrusion system (1) to work together to realize the timely alternating extrusion of a single photosensitive resin material and a photosensitive resin containing magnetic reinforcing particles; to control the magnetic field strength, working time and working mode of the digital magnetic control system (121) in the auxiliary magnetic field material extrusion system (12); to control the movement of the dynamic molding platform (3) in three-dimensional space; and to control the light intensity and switching time of the photocuring system (13). The dynamic forming platform (3) is an important component of 3D printing equipment. The dynamic forming platform (3) can move in any form, such as straight lines or curves, in the horizontal plane, and can move up and down in the vertical direction. The dual material extrusion system (1) and the dynamic forming platform (3) work together to deposit the precursor material with uniform magnetic polarity particles onto the dynamic forming platform (3) as needed. Combined with the movement of the dynamic forming platform (3) in three-dimensional space, the forming and manufacturing of honeycomb structure with patterned magnetic domain distribution is realized.

2. The 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration as described in claim 1, characterized in that, The dual-material extrusion system (1) includes: A single-material extrusion system (11) is used to selectively deposit photosensitive resin precursor material without magnetic reinforcing particles onto a dynamic molding platform (3) according to a certain printing path and printing speed; The auxiliary magnetic field material extrusion system (12) is used to selectively deposit photosensitive resin precursor material containing magnetic reinforcing particles onto a dynamic molding platform (3) according to a certain printing path and printing speed. During the printing process, a digital magnetic control system (121) is integrated. Under the action of Lorentz force, the magnetic particles produce controllable directional assembly. After the material is extruded and deposited, the magnetic polarity of the particles is still retained. By changing the direction of the applied magnetic field or the printing path, magnetic domains in the local space can be planned. The photocuring system (13) is integrated into the extruder in the form of a spotlight with a light intensity of 1000-1400 mW / cm². 2 The irradiation distance is 10-30mm and the spot diameter is 2-10mm. It is used to initially solidify the material deposited on the dynamic forming platform (3) to achieve the anchoring of the magnetic polarity of the particles.

3. The 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration as described in claim 2, characterized in that, The auxiliary magnetic field material extrusion system (12) has some of the same hardware components as the single material extrusion system (11), including: The printing material in the material cylinder (112) is extruded through the ultra-long material extrusion head (111). Its interior is a hollow cylindrical structure with an inner diameter of 0.84-1.80 mm and a length of 20-50 mm. The material cylinder (112) is connected to an extra-long material extrusion head (111) and is coaxially mounted with the material pusher (114) to hold the printing material; Fixed bracket (113) is used for the dual material extrusion system (1), dynamic molding platform (3) and control system (2); The material pusher (114) is used to extrude the printing material in the material cylinder (112) and deposit it on the dynamic molding platform (3) through the extra-long material extrusion head (111).

4. The 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration as described in claim 3, characterized in that, The difference between the auxiliary magnetic field material extrusion system (12) and the single material extrusion system (11) is that the auxiliary magnetic field material extrusion system (12) has a digital magnetic control system (121), while the single material extrusion system does not have a digital magnetic control system (121).

5. The 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration as described in claim 4, characterized in that, The digital magnetic control system (121) can adjust the direction of the applied magnetic field parallel to or opposite to the long axis direction of the magnetic field N pole and S pole of the ultra-long material extrusion head (111) in real time according to the predefined material magnetic domain distribution. The magnetic polarity in the deposition material channel can be adjusted by switching the direction of the applied magnetic field or changing the printing direction. The magnetic field strength is usually set to 15-65mT. Using this method, complex ferromagnetic domain patterns can be encoded into complex honeycomb materials.

6. The 4D printing system for a biomimetic energy-absorbing honeycomb structure with adjustable configuration as described in claim 5, characterized in that, The digital magnetic control system (121) also has a magnetic shielding structure (122) installed at the lower end of the ultra-long material extrusion head (111) to attenuate the influence of the magnetic flux density at the lower end of the ultra-long material extrusion head (111) on the magnetic polarity in the deposition material channel.

7. A method for 4D printing a configuration-adjustable biomimetic energy-absorbing honeycomb structure using a 4D printing system for a configuration-adjustable biomimetic energy-absorbing honeycomb structure as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Composition and preparation of the S101 printing material system: Matrix material 55-95 vol%: A liquid printing precursor was prepared by mixing dimethacrylate and polypropylene glycol acrylate in a molar ratio of 1:1.8-2.2, followed by the introduction of 2.5-3.5% of the photoinitiator diacylphosphine oxide 819 and 0.05% of the light absorber Sudan III; Magnetic reinforcing particles 5-45 vol%: 60-70 wt% iron oxide, 30-40 wt% neodymium iron boron; After the above components are mixed in proportion, the precursor mixture solution is magnetized under a pulsed magnetic field of about 2.0-3.0T. S102 energy absorption component model biomimetic design: Inspired by the honeycomb structure inside the peel of a ripe grapefruit with high impact resistance, a biomimetic impact-resistant honeycomb material was designed. The initial unit cell structure of the honeycomb material is hexagonal, with a cell wall thickness of 0.1-0.55 mm and a sidewall length of 9-14 mm. Under the action of a coupled magnetic field, the mechanical properties of the honeycomb material will change with temperature, and its geometric shape will also undergo plastic or permanent deformation, thereby realizing the programmable adjustment of the stiffness and energy absorption characteristics of the honeycomb structure. S103 Magnetic-Assisted Photopolymerization 3D Printing: Based on magnetic-assisted photopolymerization 3D printing equipment, complex honeycomb structures are formed. During printing, the external magnetic field is combined to construct a patterned magnetic domain distribution inside the honeycomb material. The specific steps are as follows: ① Model establishment: To establish an efficient impact-resistant honeycomb structure model, it is necessary to clarify the magnetic domain distribution in each part of the honeycomb structure; ② Slicing: Slicing is performed using professional 3D printing software to obtain selective photocuring section information of each slice layer, magnetic field direction information of the digital magnetocontrol system (121), magnetic field strength 15-65mT and magnetic field duration, photocuring switch switching time and power; ③Magnetic-assisted photopolymerization 3D printing: The matrix materials in S101 that do not contain magnetic reinforcing particles and those that do contain magnetic reinforcing particles are transferred into a single material extrusion system (11) and a material extrusion system (12) with an auxiliary magnetic field, respectively. Then, according to the process flow and printing parameters obtained in step 3, the honeycomb structure is formed and its internal magnetic domain orientation is formed. Layer by layer, a three-dimensional honeycomb structure is formed. ④ Post-processing: The formed three-dimensional honeycomb structure is placed in an ultraviolet curing chamber for further curing, and the curing time is 10-24 hours; 4D transformation of S104 honeycomb structure: Plastic deformation: First, a high-frequency induction heater with a magnetic induction coil is used to induce the iron oxide particles to vibrate at high frequency to generate heat. The power is 15-35KW and the time is 7-15s, which causes the printed honeycomb structure to heat up to 75-85℃. Then, a driving magnetic field is applied with a magnetic field strength of 200-500mT. The honeycomb structure induces the overall deformation of the printed part according to the pre-set magnetic domain distribution pattern in the material. Permanent deformation: Based on plastic deformation, a high-power high-frequency induction heater is applied, with a power of 35-60KW and a time of 5-15s, to make the overall temperature of the honeycomb structure reach 116-125℃.

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