A Study of Mechanical Behavior of Folding and Welding Connections of Kapton Films While Manufacturing a Solar Sail

Large-area membrane spacecraft, such as solar sails, must be tightly stowed before launch. However, excessive folding readily induces plastic creases that impede full on-orbit deployment and degrade membrane surface accuracy. To overcome this challenge, this study aims to quantify the mechanical response of Kapton films during folding and to establish a reliable welding process for post-fold sail membranes. Based on the theory of linear elastic engineering, an S-shaped folding model was theoretically simplified to obtain the relationship between the rebound force P of adjacent contact thin films and the thin-film spacing h. Then, the Kapton film folding process was numerically simulated based on the implicit static method by using ABAQUS. The stress–strain curves and mechanical parameters of the thin films measured through uniaxial tensile tests are applied to theoretical and numerical results. It is found that the P-h curves obtained by the theoretical, numerical, and experimental method have good consistency. Step-loaded creep tests show that, after 6 h, the mean spacing reductions Δh are 0.43 mm for 50 µm thin films and 1.05 mm for 125 µm thin films, matching simulation results within 3%. Finally, uniaxial tensile tests are conducted on the welded thin films to measure the strength of the thin-film welds under different welding temperatures and pressures. The tensile force and elongation required to eliminate weld wrinkles are also measured to explore the welding connection of Kapton film. Further, for 50 µm thin films with a 10 mm weld width, eliminating welding-induced wrinkles requires a tensile force of 9.61 N and an elongation of 0.43%.