Browsing by Author "Liyanage, PM"

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item: Conference-Abstract
Folding patterns for ultra-thin deployable membranes
Liyanage, PM; Mallikarachchi, HMYC
A deployable structure should mainly be adequately compact and should fit into any remaining space of the launch vehicle. The main factors which will determine these are the folding pattern, ease of deployment and stresses in the fold lines. Two folding patterns are selected based on extensive literature review to investigate the possibility of using those techniques for a large solar sail mission. It is expensive as well as extremely time consuming to perform experimental investigation under reduced gravity environment for this type of large membranes. Thus developing simulating techniques are quite important. Two models are simulated using Abaqus/Explicit commercial finite element software. Quasistatic conditions and numerical accuracy are verified by comparing strain energy together with kinetic energy and artificial strain energy. It is shown that spiral folding pattern requires less energy for deployment and hence that is preferred.
item: Thesis-Abstract
Modelling of the deployment behaviour of highly compacted thin membranes
(2016-09-14) Liyanage, PM; Mallikarachchi, HMYC
Space structures such as solar sails, solar reflectors, and sun shields have very large surface areas. Hence they require deployable methods to be stored and transported out of the earth’s atmosphere in limited cargo capacities available in launch vehicles. A deployable structure changes its shape and geometry to a compact state with the use of folding patterns for convenience in packaging and/or transporting. Ground testing of deployable structures using physical models requires a representative environment, i.e. a zero gravity environment, which can consume a lot of time, effort, and cost, giving rise to the requirement of simulations carried out in a virtual environment. This research develops a modelling technique which can be used to simulate the deployment behaviour of membrane type deployable structures using a commercial finite element analysis software. Commonly used spiral folding pattern was used to demonstrate the modelling technique. Modification for the fold line arrangement of spiral folding pattern to account for effects caused by membrane thickness; modelling the crease behaviour with the use of rotational springs; and robustness of the analysis indicated by energy histories were three main aspects considered when developing the modelling technique. Spiral folding pattern was modified by finding the arrangement of nodes in the folded state of the model by providing sufficient offset between planes and checking the ability of the structure to deploy into a plane sheet. This modification was proposed for modules with regular polygonal shaped hubs. Proposed modification was verified with the use of a paperboard model which had a square shaped hub of 10 mm × 10 mm, 15 nodes in a single spiral, and a thickness of 0.28 mm. Crease stiffness of Kapton Polyimide film was determined comparing data available from an experiment carried out at the Space Structures Laboratory of California Institute of Technology and results of finite element models developed to simulate the experiment. Finally two finite element models were made from the proposed technique and results of these analysis were discussed on importance of incorporating crease behaviour in finite element models, important aspects of their deployment behaviour, and robustness of analysis. This research has successfully developed an approach to modify the fold line arrangement of the spiral folding pattern with regular polygonal shaped hubs to account for the geometric effects caused by membrane thickness and a robust technique to model the deployment behaviour of membrane type deployable structures. Crease stiffness of Kapton Polyimide films was modelled as a rotational spring, where the resisting moment is considered to be proportional to the opening angle near the crease. Comparing results of two finite element models, with and without crease stiffness, showed that crease behaviour affects the deployment performance of these structures significantly, and hence it is important to be included in simulations.
item: Article-Full-text
Modified spiral folding pattern for deployable membranes
(Elsevier, 2021) Liyanage, PM; Gangasudan, N; Mallikarachchi, HMYC
Solar sails which provide propellant free propulsion are quite effective for missions that utilize small spacecrafts. These structures require a larger surface area compared to launch vehicles, hence require adopting deployable concepts. Neglecting geometric effects of membrane thickness can result in plastic deformations and wrinkling of membranes. As the issues arise in the stored configuration, they can be overcome by certain modifications to the fold-line arrangement in the pattern. We have developed a modified fold-line arrangement for modules which utilizes the spiral folding pattern using the arrangement of nodes in the folded state. We provided an offset to the nodes along the vertices of the hubs to the folded configuration to let the folding pattern accommodate the thickness. The proposed modification rearranges thenodes in the folding pattern which overcomes the adverse effects caused by the membrane thickness while achieving a compact folding state. Modified folding pattern was verified using paper models for different thicknesses and different levels of complexity.
item: Conference-Abstract
Origami based folding patterns for compact deployable structures
Liyanage, PM; Mallikarachchi, HMYC
A deployable structure should mainly be adequately compact and should fit into any remaining space of the launch vehicle. The main factors which will determine these are the folding pattern,ease of deployment and stresses in the fold lines. Two folding patterns are selected based on extensive literature review to investigate the possibility of using those techniques for a large solar sail mission. It is expensive as well as extremely time consuming to perform experimental investigation under reduced gravity environment for this type of large membranes. Thus developing simulating techniques are quite important. Two models are simulated using Abaqus/Explicit commercial finite element software. Quasi-static conditions and numerical accuracy are verified by comparing strain energy together with kinetic energy and artificial strain energy. It is shown that spiral folding pattern requires less energy for deployment and hence that is preferred.