Experimental study on the dynamic deformation and mechanical behavior of compression-twist coupled chiral metamaterials

Compression-twist coupled chiral metamaterials offer high design flexibility. While their quasi-static mechanical properties have been extensively studied, their dynamic elastoplastic behavior under impact loading remains poorly understood, particularly regarding how different geometric configurations influence stress wave propagation, energy absorption, and deformation characteristics. Based on a compression-twist chiral unit, isotactic and syndiotactic lattice unit cells were developed using different modeling strategy in this paper. Experimental specimens made of AlSi10Mg aluminum alloy and 316L stainless steel were fabricated through 3D printing. Their dynamic elastoplastic mechanical behaviors were studied using a split Hopkinson pressure bar (SHPB) system. The results show that although the quasi-static mechanical responses of the two lattice configurations are similar, their dynamic behaviors differ significant with changes in geometric parameters. The isotactic compression-twist lattice unit cell, which undergoes global twist deformation, can transform compressive stress waves into a mix of compressive and shear stress waves. In contrast, the syndiotactic compression-twist lattice unit cell, which exhibits no overall twist deformation, almost completely prevents stress wave transmission, showing excellent energy absorption capability. These findings reveal the dynamic mechanical behaviors of compression-twist coupled chiral metamaterials with different geometric configurations and offer valuable insights for the development of advanced impact-resistant protective structures and directed-energy weapon systems.