Structure Design And Properties Study Of Metastable Intermolecular Composites Based On 3D Printing

In recent years,various advanced manufacturing technologies(such as 3D printing)have been widely used to prepare structural composite materials with special properties.In order to control the reactivity and safety of the thermite,a lot of research has been done on the preparation of the thermite at home and abroad.However,there is no report on the control of the structural energetics for thermite by core-shel 3D printing of thermite ink.In this study,based on the preparation of energetic material ink formulas,hollow and core-shell fibers were prepared by core-shell 3D printing,which realized the control of the thermite reaction performance.This structural design method based on energetic materials avoids frequent adjustments to the formulas of energetic materials.This method may have potential applications in the fields of microelectromechanical system devices(MEMS),aerospace propulsion components and micro-rockets.The research content of this article is as follows:(1)Through continuous improvement and optimization of the preparation process for the energetic material ink formulas,the Al/CuO/F2311,Al/Fe₂O₃/F2311,Al/Bi₂O₃/F2311,and Al/PTFE/F2311 inks were prepared respectively.The thermal decomposition behaviors of different thermite formulas indicate that the thermal decomposition onset temperature of the Al/CuO/F2311 formula is the lowest,and the thermal decomposition begins at about 288?.The heat release of Al/PTFE/F2311 is the highest among the four formulas,and the heat release is 7200 J/g.The constant volume combustion test results show that the peak pressure and pressurization rate of the thermite fibers for the Al/CuO/F2311 formula are 0.191 MPa and 12.337 MPa/s respectively,which are the highest among the four formulas.(2)Based on 3D printing technology,a core-shell printing method of energetic material ink is designed.The four hollow fibers of Al/CuO/F2311,Al/Fe₂O₃/F2311,Al/Bi₂O₃/F2311 and Al/PTFE/F2311 were fabricated by core-shell 3D printing.The combustion process of the hollow fibers is divided into three combustion phases,which are the unstable combustion phase,the accelerated combustion phase and the stable combustion phase.The results show that the unstable combustion duration of the hollow fibers is shorter than the solid fibers.Compared with solid fibers,the stable flame propagation rate of thermite hollow fibers for different formulas is higher.For the Al/CuO/F2311 formula with a fluororubber content of 15 wt.%,the stable flame propagation rate of the hollow fibers is as high as 395 m/s(4400 times higher than the solid fibers).The combustion test results show that the content of fluororubber and the diameter of the fiber have a great influence on the stable flame propagation rate of the hollow fiber.Finally,the self-accelerating combustion mechanism of hollow fibers under the action of"cavity-mediated effect"is proposed by combining experimental phenomena and experimental results.(3)The Al/CuO/F2311 ink and RDX/HTPB/N100 ink were combined by core-shell3D printing to prepare two core-shell fibers,which are MICs(outer layer)RDX(inner layer)core-shell fibers and RDX(outer layer)MICs(inner layer)core-shell fibers.The thermal decomposition properties of the two core-shell fibers were characterized and compared with MICs and RDX.This study compared the combustion performance of the two core-shell fibers,and found that different composite methods make the two core-shell fibers exhibit different combustion performance.Compared with RDX fibers,core-shell fibers of MICs(outer layer)RDX(inner layer)have a faster burning rate.The constant volume combustion test shows that the core-shell fibers of RDX(outer layer)MICs(inner layer)have significant advantages in gas production during the combustion.It not only maintains a sufficiently high peak pressure of combustion gas,but also increases the gas pressurization rate significantly.