| As the size of the space structure becomes larger and larger,the launch cost becomes more and more expensive.Thin-film antennas,which are lightweight and foldable materials,are gradually being widely used.The thin film in the traditional space structure is prone to some problems during work,such as the insufficient performance of the thin film material and easy breakage during work.However,the Young’s modulus of commercial polyimide films is low,which is insufficient to withstand large external tensile forces.Therefore,the surface stiffness of space film structures is generally low.In addition,because the Poisson ratio of the polyimide film is large,generally 0.35 to 0.4,the film is prone to wrinkling during tensioning.Based on this,this study completed the work of homogeneous fiber reinforcement of polyimide films,the design of Poisson’s ratio of fiber-reinforced polyimide films,and the analysis of the film’s anti-wrinkle properties and parabolic tension stress analysis.The film materials which traditionally used for space structures,especially antenna structures,mostly are Kapton series films of Du Pont,but their performance is not enough to withstand the severe test of space environment.Therefore,it is necessary to strengthen the traditional thin film material,to obtain a new thin film material with better performance.Since the polyimide fiber and the polyimide film have the same material,the compatibility of the bonding interface between the two is good after the fiber is used to strengthen the film,so that the obtained polyimide composite film has better tensile properties.When the number of fiber bundles per cm reaches 20,the tensile strength of the composite film along the fibers direction is increased by 203%compared with the pure polyimide film,and the Young’s modulus is also increased by202%.The Poisson’s ratio of the film brings about the wrinkling effect of the film in unidirectional tension,which is one of the problems in the work of the space film.For2 D materials,the Poisson’s ratio design can make the material exhibit an auxetic effect,which can just inhibit the wrinkling of the film to a certain extent.Using the orthogonal elliptical holes array structure,the Poisson’s ratio design of the composite film was carried out,and the Poisson’s ratios and Young’s moduli of the films were obtained by analyzing the ratio of the long axis of the elliptical holes to the ratio of the long axis and the short axis under different boundary distances between the holes.The Poisson’s ratios and Young’s moduli decrease continuously with the increase of the long axis ratio,which is caused by the torsional behavior of the cells in the film after perforation.In the parabolic tension of the film,the anti-wrinkle properties of the material and the stress distribution after tensioning are the parts worthy of attention.For a porous composite film with a Poisson’s ratio design in the form of an orthogonal elliptical hole array,its anti-wrinkle performance was investigated when the boundary distance between the holes was equal to 6 mm,and its stress distribution and stress concentration phenomena in the parabolic cylindrical tension shape were investigated.When the elliptical hole gradually becomes sharper,the critical buckling external load corresponding to the film becomes larger,and accordingly,the stress concentration phenomenon becomes more serious.Corresponding to the anti-wrinkle critical buckling load of the two films when the elliptical hole is circular and when the ratio of the length of the major axis of the elliptical hole to the length of the major axis and the length of the minor axis is 98%,the latter is 2 times that of the former. |
