Study On The Preparation,Properties And Application Of Nanocomposites Via 3D Printing

3D printing,or additive manufacturing,is a technique for rapid prototyping of material.The most immediate contribution of 3D printing is the assistance it provides for polymer materials so that they can be shaped into any complex geometries or structures without the restriction of molds.This progress is of great meanings because nowadays structure design is playing more and more important role in tuning the performance and application of polymer materials.Besides,individual requirements of material are common,especially in applications of aerospace or biomedical domain.The developments of 3D printing also brings newer and higher demands for printable materials in turn.The deeper influence of 3D printing is that it is an additive manufacturing method and the final product comes from the continuous accumulation of materials.The unit of accumulation and the sequence of accumulation can also be used to regulate the final performance of products.Moreover,with the development and maturity of the multi-material 3D printing technique,the collocation of different materials and the spatial distribution of different materials have become factors that cannot be ignored in material design.This paper focused on the extrusion-based 3D printing as the main manufacturing method.Studies were done on how to prepare printable and functionalized nanocomposites according to different application requirements.Moreover,through the full utilization and adjustment of the 3D printing technique,it is possible to optimize or improve the performance of final products.The detailed research contents are summarized as follows:(1)Conductive Horseshoe structure with skin-like mechanical responseCarbon nanotubes were introduced into the thermoplastic polyurethane matrix by melting blending to obtain conductive elastomer composites.Further,the composites were processed into filaments with 1.75 mm diameter so that they can be printable via a fused deposition modeling(FDM)3D printer.The Horseshoe structure can be printed by improving the hardware of the 3D printer and modifying the printing control code.The structure has a mechanical response similar to that of human skin,and can be accurately regulated by adjusting the structural geometric parameters.In this way,we realized the elastic conductor with the same mechanical response as human skin through 3D printing,and successfully combined the structural properties and functional properties of the material.(2)Epoxy ink for 3D printing and mechanical properties of printed samplesStudies were done on how to prepare epoxy-based materials for the 3D printing technique,direct ink writing(DIW).On the purpose of preparing qualified epoxy inks,we investigated the effects of fumed silica on the gel state of epoxy resin,including silica content,specific surface area,surface modification and dispersion methods.On this basis,the qualitative relationship between the rheological properties of printable ink and the actual printing effect is established.Through a series of mechanical tests,including quasi-static tension,quasi-static flexure,fracture and impact,the mechanical properties of samples with different printing paths were characterized comprehensively.The results show that performances of the printed samples have no obvious dependence on the printing path and no degradation compared with the cast molding samples.(3)3D printing of high modulus,high strength shape memory epoxy based compositesOn the basis of study(2),the material is further strengthened by adding short carbon fibers(SCF).In the process of material extrusion,SCF formed an obvious orientation,which can be characterized by Micro CT.Because of the orientation of SCF,the printed samples exhibit higher modulus and strength along the orientation direction.For the application of its excellent shape memory effect,inks that can be used as supporting materials were designed and prepared,and with the assistance of double printing heads,3D models with high span structure can be achieved which provides convenience for any structure manufacturing in practical application.(4)Friction and wear properties of epoxy based composites by 3D printingOn the basis of study(2),epoxy-based printable materials with low friction coefficient and low wear rate were prepared by adding SCF and graphite into epoxy ink.Due to the orientation in the material extrusion process,the surfaces parallel to the orientation direction or normal showed quite different performances under the tribological tests of different normal forces.The mechanism leading to the differences was studied.On this basis,the design of printing path was used to adjust orientation of fillers in different areas of the sample,which can further improve the friction and wear performance of the material under the high normal force.