| Biomaterials are arranged into various orderly structures by using fiber and other reinforcement elements to achieve performance control.For example,mantis shrimp uses spiral arrangement of fibers to improve the impact resistance of materials,shell uses brick and mud structure to enhance the toughness of materials,pine tower scale uses anisotropic fiber orientation of double-layer structure to control deformation,etc.The biomaterials construction strategy has the advantages of high efficiency and versatility,and exhibits superior performance beyond the artificial materials,such as light and strong,strong and tough,adaptive and self-repairing.Although biology provides design solutions,it is extremely difficult to imitate the complex structure of bioinspired materials in the field of engineering materials.Additive Manufacturing(3D Printing)is a manufacturing technology driven by digital model and cumulative moulding by adding materials point by point.It has the potential ability to to regulate the organizational structure of materials in the printing process,which makes it possible to design and manufacture bioinspired materials with complex structure.However,current printing technology cannot directional assembly of reinforcing materials,and it is an urgent need to develop a shape-controllable and performance-controlled additive manufacturing technology for the preparation of bionic ordered structural materials,exploring structural-performance relationships,and providing theoretical basis and practical manufacturing techniques for the development of next-generation advanced materials.In this thesis,a magnetic assembly 3D printing technology using magnetic field to orient the reinforcing material was developed.The effects of magnetic field strength and material properties on the orientation assembly performance were studied,and the optimized assembly printing process parameters were obtained.After that,several typical bioinspired materials with ordered structure control performance were designed and fabricated by using magnetic assembly 3D printing technology,including:(1)bioinspired impact-resistant materials,using fiber arrangement structure to control and enhance the mechanical properties of materials;(2)bioinspired thermal control materials,using fiber orientation to control the thermal properties of materials;(3)bioinspired microstructure-controlled self-deforming materials,The ordered structural fibers are printed in a deformable matrix,and the orientation of the fibers is used to control the deformation of the material.This thesis studies the influence of ordered structure form and parameters on material properties,reveals the relationship between material structure and properties,proves the feasibility of using bionic ordered structure design to realize material performance control,and provides design basis and manufacturing approach for the development of bionic materials.The specific research contents of this thesis mainly include the following four aspects:(1)A magnetically assisted 3D printing technology based on magnetic assembly process and digital light curing technology was developed to locally control the fiber orientation inside the material while printing complex geometric shapes.The principle of magnetic assembly printing technology is that magnetic short fibers are added to liquid photosensitive resin printing materials,and directional assembly of fibers is carried out by controlling the direction of fibers by programmable magnetic field,so as to achieve ordered fiber reinforced material printing.The principle of magnetic assembly printing technology is that magnetic short fibers are added to liquid photosensitive resin printing materials,and directional assembly of fibers is carried out by by programmable magnetic field,so as to achieve ordered fiber reinforced material printing.The effects of magnetic field,process parameters and fiber content on fiber orientation and curing degree of materials were studied.The optimized material ratio,magnetic field and printing parameters were obtained,which provided a practical and low-cost manufacturing method for the preparation of bionic ordered structural materials.(2)The micro-structure coupled with the herringbone and the spiral in the appendage material of the appendix material of mantis shrimp with excellent mechanical properties is used as a model to carry out the bionic structure design,and the corresponding bioinspired material is prepared by the magnetic assisted 3Dprinting process.The effects of fiber arrangement structure and parameters on the properties of materials were studied.It was found that the impact resistance and compressive properties of materials were related to the fiber arrangement and parameters.The primary and secondary stru ctural factors affecting the mechanical properties of materials were determined by orthogonal experimental design and range analysis method,and the regression mathematical model of material properties and structural elements was established by multiple orthogonal regression design method.(3)Ordered arrangement structure can not only affect the mechanical properties of materials,but also affect the physical properties of materials such as such as heat,light and electricity..Inspired by the biological method of structural regulation,ordered structural materials were designed and prepared.The effects of structural forms and parameters on thermal conductivity and thermal stability of materials were studied.The results show that the thermal conductivity of the ordered reinforced structural materials is related to the direction of the fibers.The thermal conductivity of the materials parallel to the direction of the fibers increases,while the thermal conductivity of the materials perpendicular to the direction of the fibers decreases.The thermal metamaterials with different fiber orientations at different positions were prepared by magnetic assembly 3D printing.The thermal properties of the bioinspired materials show that the materials have anisotropic and site-specific thermal properties.This material whose thermal properties change with position is called thermal metamaterial.It has broad application prospects in electronic packaging,solar cells,lithium batteries and heat sink materials.Compared with current homogeneous materials,it can not only improve heat conduction and Thermal stability also enables thermal management functions such as heat shielding and heat concentration.(4)4D printing is an excitation-response material structure of 3D printing,which can produce programmable shape or property changes when it meets appropriate external excitation.Biological materials use ordered structure of fibers to control deformation.Using this control principle and magnetic assembly 3D printing,the research of bioinspired microstructural programming 4D printing is carried out.Bionic design was carried out on the basis of pine tower scale fiber structure.Theexcitation response materials with ordered microstructures were printed by 4D magnetic assembly technology.The effects of fiber orientation,distribution and parameters on the deformation properties of materials are studied.The relationship between fiber orientation and deformation is revealed.A design method of 4D printing based on bionic microstructural programming is proposed.How to use material structure design to control 4D behavior is the key technology of 4D printing.The internal structure programming of materials gives full play to the advantages of3 D printing and expands the design space of 4D printing. |
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