Stiffness-mass-coding metamaterial with broadband tunability for low-frequency vibration isolation

•A stiffness-mass-coding model realizes the tunable multi-resonance coupling.•The stiffness-mass-coding metamaterial is proposed with tunable performance.•The coupling of tunable out-of-plane and in-plane vibration bandgaps is realized.•The SMCM realizes the broadband tunability for low-frequency vibration isolation. Low-frequency vibration isolation is essential for safety, accuracy and stability in various engineering areas. Traditional methods are generally limited to the adjustment of vibration bandwidth and frequency, so broadband tunability is challenging in practical low-frequency isolation applications. This paper proposed a stiffness-mass-coding metamaterial (SMCM) to achieve broadband tunability for low-frequency vibration isolation. For the proposed SMCM, two basic stiffness-mass-coding supercells are connected vertically, leading to the coupling of out-of-plane and in-plane vibration bandgaps. The stiffness-mass-coding supercell is composed of four tunable local resonators with tunable effective stiffness and effective mass, which is designed with tunable magnetic force and center mass to realize the tunable multiple bandgaps. Theoretical derivation explains the tunable multi-resonance coupling mechanism of the proposed SMCM model. Experiments demonstrate that the lower bound and the bandwidth of the SMCM bandgap are both flexibly adjustable with the stiffness-mass-coding model. Furthermore, a tunable ultra-broad bandgap can be generated with the SMCM based on the tunable multi-resonance coupling mechanism, leading to the broadband tunability for low-frequency vibration isolation. The proposed SMCM design realizes the tunable multi-resonance coupling, provides a new idea on the low-frequency broadband tunability and shows potential in many related engineering applications.