Reconfiguration of Kirigami-Inspired Parachutes*

Upon deployment, the abrupt deceleration of conventional parachutes leads to an opening shock that can cause joint and muscle pain to skydivers as well as excessive forces on payload. Mechanical metamaterials inspired by kirigami offer opportunities to reduce the parachute opening shock as they exhibit exotic reconfiguration under transverse flow. Here, we show that by adding slits to a flexible disk, we can control its drag-speed response under flow through geometric design. First, using an in-house finite element solver, we show that we can model pressure drag with pressure models based on momentum conservation laws and still fit accurately experimental data found in the literature. Second, we study the behavior of different kirigami patterns under flow and compare the simulation results with experimental data obtained by placing laser-cut samples in a wind tunnel. Guided by these results, we fabricate a kirigami-inspired parachute with a programmed drag-speed response under flow. Due to the simplicity and low cost of manufacturing these kirigami-parachutes, these would be ideal for humanitarian airdrops and, in the future, kirigami structures could be used for other fluid-structure applications such as shape-varying membranes under varying flow speeds.