Multi-stability of fiber reinforced polymer frames with different geometries

Abstract

Shape adaptable structures are desired in many fields of application such as aerospace, soft robotics, and architecture. Multi-stable structures can enable shape adaptation as they possess multiple stable morphologies that can be held without the need of external work. Many concepts to realize multi-stable systems have been proposed in the last decades. However, the vast majority of multi-stable structures exhibit minimal changes in shape or high coupling between stable states, which limits their applicability. Recently, a novel class of multi-stable composite structures has been investigated, showing that a periodic arrangement of square frames combined with pre-stretched membranes enables many stable states together with large shape transformations. To investigate how this new class can be employed in a broader range of applications, this study extends the design space to any N-sided regular polygon frame. The multi-stability is investigated through experiments and finite element (FE) analysis. The polygonal frames and their respective periodic arrangements possess a large number of stable states, with similar behavior to that of the square frames. Moreover, neutral stability is observed for the limit case of a circular polygonal frame. This study proves that the concept is highly flexible in terms of design, thus opening up new possibilities for applications of multi-stable composite structures.