Abstract:A particular set of requirements is identified for the response of a passively actuated shape-adaptive structure. It is shown that neither conventional structures nor simple structural instabilities have suitable properties in order to meet these requirements. A novel solution is proposed which combines multiple structural instabilities to create a compound instability. This approach enables the shape-adaptive structure to achieve large output displacements only after a triggering input displacement is reached… Show more
“…Note that this change does not affect the shape of the branch bifurcating from B1. However, it does affect its stability, and B2 is shifted further up this branch and away from B1 [41].…”
Section: (A) Double Branching Point Structurementioning
confidence: 98%
“…Note that this change does not affect the shape of the branch bifurcating from B1. However, it does affect its stability, and B2 is shifted further up this branch and away from B1 [41]. Figure 4( a ) Equilibrium paths of the double branching point structure with α=1, β=1, γ=0.7 and η=0.05.…”
Section: Analysis Of Sequential Instabilitiesmentioning
confidence: 99%
“…The two curves in figure 8 b each correspond to a model with different fin thickness. Varying the fin thickness, t, increases the bending stiffness of the fin, EI, which is found to have a similar effect on the behaviour of the structure as varying β has on the double branching point bar-and-spring structure 4 [41]. Indeed, it can be seen from figure 8 b that increasing the fin thickness reduces the degree of interaction between the branching points to the stage where the response is fully stable, as was the case in figure 4 a .…”
Section: Function From Sequential Interacting Instabilitiesmentioning
Elastic instabilities have traditionally been considered a failure mechanism; however, recent years have seen numerous studies exploiting instabilities as a means to achieve structural functionality. By contrast, interacting instabilities and compound buckling are still largely viewed as a failure mechanism. In this paper, we show that interacting instabilities can also be exploited to achieve bespoke functionality. We focus on ‘sequential instabilities’, whose associated critical points cannot both lie on a fundamental equilibrium path. We obtain sequential instabilities by combining canonical bifurcations, (e.g. limit point, pitchfork) as building-blocks. Initially, this concept is explored through simple bar-and-spring models that are found to have several properties not exhibited by the building blocks from which they are constructed. Further, the utility of the building block approach, and that of sequential, interacting instabilities, is demonstrated through the development of a morphing structure which must rapidly deploy after a critical input displacement is attained, and meet specific post-deployment stiffness requirements. Two design concepts are proposed, each comprising building blocks to mirror the fundamental working principles identified through the bar-and-spring models. Finite-element models of the design solutions are presented, demonstrating how the designs positively use sequential, interacting instabilities in order to meet the challenging requirements of the application. This work extends the contextual framework of instabilities that can be used to create structures with novel functionality.
“…Note that this change does not affect the shape of the branch bifurcating from B1. However, it does affect its stability, and B2 is shifted further up this branch and away from B1 [41].…”
Section: (A) Double Branching Point Structurementioning
confidence: 98%
“…Note that this change does not affect the shape of the branch bifurcating from B1. However, it does affect its stability, and B2 is shifted further up this branch and away from B1 [41]. Figure 4( a ) Equilibrium paths of the double branching point structure with α=1, β=1, γ=0.7 and η=0.05.…”
Section: Analysis Of Sequential Instabilitiesmentioning
confidence: 99%
“…The two curves in figure 8 b each correspond to a model with different fin thickness. Varying the fin thickness, t, increases the bending stiffness of the fin, EI, which is found to have a similar effect on the behaviour of the structure as varying β has on the double branching point bar-and-spring structure 4 [41]. Indeed, it can be seen from figure 8 b that increasing the fin thickness reduces the degree of interaction between the branching points to the stage where the response is fully stable, as was the case in figure 4 a .…”
Section: Function From Sequential Interacting Instabilitiesmentioning
Elastic instabilities have traditionally been considered a failure mechanism; however, recent years have seen numerous studies exploiting instabilities as a means to achieve structural functionality. By contrast, interacting instabilities and compound buckling are still largely viewed as a failure mechanism. In this paper, we show that interacting instabilities can also be exploited to achieve bespoke functionality. We focus on ‘sequential instabilities’, whose associated critical points cannot both lie on a fundamental equilibrium path. We obtain sequential instabilities by combining canonical bifurcations, (e.g. limit point, pitchfork) as building-blocks. Initially, this concept is explored through simple bar-and-spring models that are found to have several properties not exhibited by the building blocks from which they are constructed. Further, the utility of the building block approach, and that of sequential, interacting instabilities, is demonstrated through the development of a morphing structure which must rapidly deploy after a critical input displacement is attained, and meet specific post-deployment stiffness requirements. Two design concepts are proposed, each comprising building blocks to mirror the fundamental working principles identified through the bar-and-spring models. Finite-element models of the design solutions are presented, demonstrating how the designs positively use sequential, interacting instabilities in order to meet the challenging requirements of the application. This work extends the contextual framework of instabilities that can be used to create structures with novel functionality.
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