Research On Folding Method And Splicing Strategy Of Discontinuous Membrane Structure

In recent years,with the development of aerospace industry,thin-film structures have been widely used in space structures such as solar sail,light shield,thin-film antenna,solar array.Space membrane structure has the development trend of large-scale,lightweight and flexible,so it puts forward higher requirements for the materials,processing technology,folding and unfolding technology of space membrane structure.In this paper,the research on the planar membrane structure made by butt splicing includes the experimental study on the mechanical properties and tensile wrinkling phenomenon of the membrane specimen with seam,the analysis of the folding process of the planar membrane structure,and the analysis of the form finding and tension of the planar membrane structure.Firstly,the material properties of the polyimide film with thickness of 0.025 mm and the film with seam width of 25 mm were tested,and the elastic modulus of the film and seam area were measured.The rectangular pure membrane specimens with length width ratio of 4:1,3:1,2.5:1 and2:1 and the membrane specimens with seam width of 25 mm were designed.The displacement load and stress-strain curves of the specimens under 5 mm/min unidirectional loading were obtained by uniaxial tensile test,and the out of plane deformation values of the specimens were obtained by means of non-contact digital image correlation measurement technology.The points on the center line of the cross section of the film specimen were selected to analyze the out of plane deformation.In addition,thin film specimens with 12.5mm seam width were designed.The test results showed that only the seam width of 25 mm can provide enough adhesive force.On the basis of the experiment,the numerical simulation was carried out,and the accuracy of the finite element analysis was verified by comparing the experiment result with the simulation result.Secondly,based on the motion process analysis method of pin-joint structure mechanism,the motion process of a square hub rigid winding configuration was solved by MATLAB,and the calculated rigid displacements were substituted into ABAQUS for analysis.The analysis results showed that according to the rigid displacement driving mode,the membrane structure could achieve low stress folding,and the folding effect was good.For the non-rigid winding configuration of hexagonal hub,the creases were added to convert it into rigid configuration.The analysis results showed that the stress was lower in the folding process only by adding crease.Sometimes,the plate element contact occured in the folding process when the non-rigid configuration was converted into rigid configuration.In this case,winding folding was realized through two stages: rigid folding stage and additional displacement folding stage.In addition,the effects of two kinds of seam area arrangement on the folding process were also studied.Finally,the finite element software RFEM and ABAQUS were used to simulate the tension analysis and optimization analysis of the planar membrane structure,and ABAQUS was used to verify the correctness of RFEM form finding results.In practical engineering,the planar membrane structure is only tensioned by applying cable force,so the tension analysis of the planar membrane structure was carried out on the basis of the form finding form.The results show that the film stress was uneven and small,and the edge shape was also different.In view of this situation,an optimization idea was proposed,which mainly included stress optimization and edge shape optimization.In addition,the influence of seam arrangement and seam number on the structure was studied,and the planar membrane structure considering seam effect was optimized.