Prediction of mechanical properties of creases in thin folded membranes

Abstract

Thin membranes underpin many light weight deployable space systems. Folds introduced in these membrane structures for logistics and storage, alter their in-orbit behaviour while deploying. Numerical modelling is relied on as a promising tool in studying the deployment behaviour of these space structures. However, most numerical models aimed at studying deployment behaviour, fail to incorporate fold-line properties due to unavailability of reliable experimental data. In this research, an attempt has been made to virtually predict the fold-line mechanics using nite element analysis. For this purpose, materially and geometrically nonlinear contact analyses using Abaqus FEA were performed to simulate creased geometry and conduct numerical tensile tests on single folded thin Kapton membranes. Moment - angle responses were plotted using results of simulations and compared with the data obtained from physical experiments and a justi able agreement was achieved. A further comparison with results from Elastica theory highlights the viability of the proposed numerical approach over analytical models. The use of virtual simulations to characterize the mechanics of fold-lines has proved to be an e cient technique. The developed fold-line behaviour model was then implemented in commercial nite element package, Abaqus for deployment simulation of single folded thin Kapton membranes using connector elements de ned with rotational sti ness. The results were validated against physical experiments and compared with other simulation techniques found in literature. The proposed technique with connector elements is meritorious over other techniques as it captures both the deformed pro le and axial displacements along the folded membrane with close agreement with experimental results. ii A quasi-static deployment simulation of a solar sail model with thin membrane wrapped around a polygonal hub was carried out using Abaqus/Explicit package to study the deployment behaviour. The fold-line idealisation scheme with connectors de ned with rotational sti ness was used to model the fold-lines in this multiply-creased membranes. However, the fold-line sti ness had little e ect on the deployment force of the sail in the range of deployment carried out experimentally .