Rotational-inertia-enhanced quasi-zero-stiffness chiral metamaterial for high-performance low-frequency vibration isolation

Vibration isolators combining quasi-zero-stiffness (QZS) and inerters offer excellent low-frequency performance, yet their bulky components hinder practical deployment and conflict with miniaturization trends. To address this limitation, this paper proposes a rotational-inertia-enhanced quasi-zero-stiffness chiral metamaterial (RQCM) that simultaneously exploits QZS and compression-torsion-coupling (CTC) rotational inertia within an integrated metamaterial architecture. Its unit cell consists of a chiral structure (CS), an inertial ring, and a rotational base. It exploits the synergistic effects of QZS characteristics, CTC mechanisms, and enhanced rotational inertia in a compact configuration. The stiffness and CTC behaviors of the CS are first characterized through static finite element analysis and experiments, revealing a strong geometric influence on its force-displacement and angle-displacement responses. Subsequently, an equivalent dynamical model of the unit cell, incorporating nonlinear elasticity, internal friction, and fractional derivative damping, is developed to study the effects of excitation amplitude, inertial ring mass, and fractional derivative order on the transmissibility-frequency response. Vibration experiments validate the dynamical model and demonstrate that the RQCM achieves a 45% reduction in the vibration isolation onset frequency (from 6.2 Hz to 3.4 Hz) compared to a design without rotational inertia. This work offers a promising design approach for high-performance low-frequency vibration isolators.