Curved-sided hexagrams with multiple equilibrium states have great potential
in engineering applications such as foldable architectures, deployable
aerospace structures, and shape-morphing soft robots. In Part I, the classical
stability criterion based on energy variation was used to study the elastic
stability of the curved-sided hexagram and identify the natural curvature range
for stability of each state for circular and rectangular rod cross-sections.
Here, we combine a multi-segment Kirchhoff rod model, finite element
simulations, and experiments to investigate the transitions between four basic
equilibrium states of the curved-sided hexagram. The four equilibrium states,
namely the star hexagram, the daisy hexagram, the 3-loop line, and the 3-loop
"8", carry uniform bending moments in their initial states, and the magnitudes
of these moments depend on the natural curvatures and their initial curvatures.
Transitions between these equilibrium states are triggered by applying bending
loads at their corners or edges. It is found that transitions between the
stable equilibrium states of the curved-sided hexagram are influenced by both
the natural curvature and the loading position. Within a specific natural
curvature range, the star hexagram, the daisy hexagram, and the 3-loop "8" can
transform among one another by bending at different positions. Based on these
findings, we identify the natural curvature range and loading conditions to
achieve transition among these three equilibrium states plus a folded 3-loop
line state for one specific ring having a rectangular cross-section. The
results obtained in this part also validate the elastic stability range of the
four equilibrium states of the curved-sided hexagram in Part I. We envision
that the present work could provide a new perspective for the design of
multi-functional deployable and foldable structures