Folding/Unfolding Properties Of Shape Memory Laminated Films

A lightweight film structures is making more and more attention in the design of large space structures.This is because that the lightweight deployable film structure has the advantages of small packaging volume,lighter weight,large expansion ratio,compared with the conventional mechanical structure.So it is considered to be one of the main technical ways to construct a large space structure in the future.However,the space deployable film structure needs to be tightly folded before the folded film is launched,which means that the flexible film needs to be bent with a large curvature.The film is caused to undergo irreversible plastic deformation,so that the smooth plane film is formed some crease near the folding line.The crease cannot be recovered even after the film is unfolded.Thus the amount and extent of film creases will affect the working state of the space structure.Therefore,in this paper,a shape memory epoxy resin and its laminated film bending/unfolding large deformation are taken as a problem.The preparation and performance characterization of shape memory laminated film and shape memory polymer bending-unfolding shape memory behavior of finite elements are carried out.Research on simulation methods and the mechanical properties of large-curvature laminated film structures are of great significance for the design and application of novel space deployable film structures.Firstly,this paper studies the heating performance of conductive films,quantitatively analyzes the relationship between the resistivity of the film and the thickness of the conductive film,and the length of the conductive film.Then,EP-OA/MXDA toroidal resin toughening system with shape memory properties was prepared.The glass transition temperature,shape memory properties and mechanical properties of the epoxy resin system were discussed.The effect is that the EP-90OA/10 MXDA epoxy resin system has the lowest Tg,easy heating,the best toughness and the strongest shape memory characteristics,and meets the large curvature bending performance requirements of the laminated film structure.Furthermore,the mechanical properties of the laminated film structure and the bending/expansion properties of the large curvature were studied by experimental methods.The elastic properties of the laminated film and the elastic recovery contribution of the polyimide film were studied,as well as the yield strength and tensile strength of the laminated film.The strength and the folding balance angle of the laminated film with large curvature are changed with the thickness of the shape memory epoxy layer.Finally,the reverse bending and the method of punching in the crease area for the angle of the laminated film are studied.Influence,it was found that both methods can significantly improve the maximum expansion angle of the laminated film.Secondly,the shape memory characteristics of the shape memory polymer layer in the laminated film are described.The calculation strategy of the general finite element simulation analysis of the shape memory polymer with viscoelasticity is given.The viscoelastic parameters required in the simulation calculation are obtained and obtained.Then,the large deflection bending/expansion process of shape memory epoxy resin was simulated based on the line viscoelastic model and Prony series.The thermal expansion coefficient,Poisson's ratio,elastic modulus,relaxation time and time-temperature equivalent were discussed by parameterization.The influence of material parameters such as equation constant on the shape memory behavior of shape memory epoxy resin.Finally,the shape memory laminated film was taken as the experimental research object.The loading process of the large curvature bending experiment of the laminated film was established.The large curvature bending experiment of the laminated film with different resin content under normal temperature and glass transition temperature was studied.The effect of different Kapton film thickness and resin thickness on the bending property,and the influence of progressive bending loading on the mechanical response of the film;the relationship between the bending force and the bending pitch,and the film thickness and the minimum bending pitch,the maximum bending The relationship between force and bending loss spacing;the bending angle of the large curvature of the film and the effect of reverse folding on the bending properties of the laminated film with large curvature were studied.