Temperature-controlled dual-material quasi-zero-stiffness isolator for variable loads

Conventional quasi-zero-stiffness (QZS) isolators are inherently limited to a single rated load, severely restricting their application where payloads vary. To overcome this fundamental limitation, this paper proposes a novel dual-material QZS (DM-QZS) isolator with stiffness tuning via temperature control. The isolator consists of a pair of symmetric dual-material elements, each formed by two serially connected, geometrically identical curved beams made of PETG and shape memory polymer (SMP), respectively. PETG provides the essential stiffness nonlinearity, while SMP enables active thermal tuning of the overall stiffness to achieve QZS conditions under different loads. A chained double curved beam constraint model (CDCBCM) and a genetic algorithm were used for static characterization and parameter optimization. A nonlinear dynamic model with fractional derivative damping was then established, and the steady-state response and displacement transmissibility were derived by the harmonic balance method. The results show that, compared with conventional QZS isolators, the proposed DM-QZS isolator can maintain stable periodic motion and effective low-frequency isolation under multiple loads through temperature adjustment. Experiments further verify tunable stiffness for two rated loads and broadband low-frequency vibration isolation in both cases.