Bio-inspired compression-torsion coupling metamaterial plate with programmable bandgaps

The development of vibration isolation systems featuring broadband low frequency attenuation is of significance to high precision sectors such as aerospace and automotive industries. In this work, a novel compression-torsion coupling mechanical metamaterial plate was proposed, in which 3D variable radius bio-inspired helical curved beams were employed to replace conventional chiral straight beams, and monolithic fabrication was achieved using polylactic acid-shape memory polymer (PLA-SMP). A combined framework integrating theoretical analysis, finite element simulations, and experiments was established. The flexural wave dispersion branches of the metamaterial plate were reconstructed using a lumped mass and equivalent spring model together with the plane wave expansion method, and distinct flexural wave bandgap distributions were revealed for isotactic and syndiotactic configurations due to the opposite signs of the coupling stiffness associated with the chiral units, thereby demonstrating an enhanced bandgap formation capability. The low frequency transmission attenuation of both configurations was validated through simulations and experiments, and the tuning relations between structural parameters and the bandgap boundaries were derived. Benefiting from the shape memory effect of PLA-SMP, multiple reversible programming pathways were implemented to realize reprogrammable bandgap modulation. Finally, by extending the concept of elastic topological insulators to the metamaterial plate, bandgap topology and band edge mode inversion were realized via ligament radius contrast. The proposed design is expected to have strong potential in low frequency vibration isolation, reconfigurable waveguiding, and adaptive structural systems.