Magnetic driving mechanics of a bistable composite cylindrical structure

Abstract Bistable composite cylindrical structure is a thin-walled shell, which is stable at both its extended and coiled configurations, offering large shape morphing capabilities without structural damage, and has been successfully applied in deployable structures and launched in-orbit. Smart morphing design provides new freedom and flexibility for space deployable mechanics to reduce structural weight and complexity. Here, we presented a novel magnetic activated bistable composite cylindrical structure, where the fundamentals on the critical magnetic driving boundaries were revealed for the first time to develop reversed smart morphing design principle. This is achieved by employing a magnetic responsive area within a bistable composite, where the NdFeB particles were co-cured directly with the carbon layups to ensure well bonding. Theoretical analysis on the magnetic driving principle was developed to indicate the interacting mechanics when a bistable structure was subjected to magnetic actuation. The magnetic field distribution was characterised through experiments; a series of magnetic responsive bistable composite cylindrical samples were produced and subjected to magnetic activation to determine the critical shape transition intensities. Their shape-changing processes were also evaluated through mechancial testing and compared to the magnetic driving mechanics. It is found that there is an optimal level in magnetic particle concentration to minimise the magnetic responsive time and input energy; the critical boundaries in terms of the current and air gap are established through theoretical analysis, and verified through experimental observations. The magnetic driving mechanics is then discussed and concluded in details. These provide a simple and effective alternative for smart driving and morphing control of the bistable composite structures, which are expected to promote their future applications to deep space explorations.