Nonlinear dynamics and chaos of a waterbomb origami unit-cell considering different symmetry conditions

Origami has been inspirating the development of novel engineering systems and structures. The traditional waterbomb folding pattern is one of the most widely employed pattern and its description from the unit-cell is related to multiple degrees of freedom (DoF) systems. This work investigates the nonlinear dynamics and chaos of a waterbomb origami through its unit-cell, considering different symmetry hypotheses that simplify its kinematics, resulting in 1-DoF and 2-DoF dynamical systems. The investigation starts with a kinematic analysis of the waterbomb folding pattern and afterward, a reduced-order dynamical model with lumped masses on vertices and torsional springs on creases is built. Symmetry assumptions are discussed, identifying the differences induced by either geometrical nonlinearities or external stimuli. Numerical simulations are carried out showing details of the system nonlinear dynamics, showing intricate situations such as chaos. The comparison among different symmetry conditions provides a qualitative picture of the system dynamics, showing significative differences and highlighting the importance of the origami mechanical behavior comprehension, its modeling and nonlinear dynamics for a proper design of origami-inspired systems.