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Bistable Scissor Structures: Computational Design and Modelling

par Arnouts, Liesbeth
Président du jury Bouillard, Philippe
Promoteur Berke, Peter ;De Temmerman, Niels
Co-Promoteur Massart, Thierry,Jacques
Publication Non publié, 2021-12-21

Thèse de doctorat

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Résumé :

Inmany applications structures need to be easilymoveable, or deployed at high speed on unprepared sites. For this purpose, pre-assembled deployable structures, which consist of beam elements connected by hinges, are highly effective: transportable with a rapid transformation and a huge volume expansion. Intended geometric incompatibilities between the members can be introduced as a design strategy to instantaneously achieve a structural stability at deployment that can be sufficient for sustaining the weight of the structure. In such bistable scissor structures, these incompatibilities result in the bending of some specific members that are under compression with a controlled snapthrough behaviour.Attempts to design deployable bistable structures remain scarce, since the underlying structural-mechanical concepts are complex. Furthermore, the requirement of flexibility during deployment while ensuring some structural stability in the deployed state prevents the use of simple design methodologies relying on the structural behaviour under service loads only. In this dissertation, computational tools are developed and applied for the structural analysis and design process of deployable bistable structures. Computational tools are crucial for the geometrical and structural design, for the definition of a rigorous design methodology and for a deeper understanding of the complex transformation behaviour of these structures.First, a geometric design methodology is proposed for triangulated bistable scissor structures, taking explicitly the finite hinge size into account. Next, a 3Dnonlinear structural model is proposed to simulate the transformation of bistable scissor structures as well as their behaviour in the deployed state. This model was used to investigate the effect of geometrical imperfections in a stochastic approach during transformation. The structural analysis was combined with a multi-objective evolutionary algorithm to define an optimisationmethodology for bistable scissor structures, taking into account the requirement of a low peak force during transformation as well as the high stiffness requirement in the deployed state. A final design methodology is proposed for bistable scissor structures which combines a topology optimisation step with a shape and sizing optimisation step, resulting in optimised structures. Finally, a method was proposed in which the optimised results of a few structures were used to obtain solutions for other structures by inter- or extrapolation.