A novel asymmetric fish metamaterial with compression-torsion coupling effect

This article introduces a type of metamaterial based on the fish cell, which exhibits a compression-torsion coupling effect. By disassembling and reassembling the fish cell, two novel compression-torsion metamaterials have been developed (type-I and type-II). The expression for the torsion angle of the type-II cell is established based on the energy method and beam theory. The proposed unicell wrapped into square tubular compressiontorsion metamaterials (ST-CTM) and cylindrical tubular compression-torsion metamaterials (CT-CTM) are comparatively analyzed, and it is found that the ST-CTM with smaller axial dimensions has larger torsion angles. The parametric analysis of the vertical dimension a of the inclined rod and the dimension b of the vertical rod has been carried out. The law of variation of torsion angle of tubular compression-torsion metamaterials with the variation of a and b is obtained and its intrinsic reasons are analyzed. Additionally, it is proposed to arrange the cells into a hexahedral compression-torsion metamaterial (HCTM), which offers higher spatial utilization efficiency and compression-torsion conversion efficiency. The efficiency of compression-torsion conversion primarily depends on the number of arrays (N) and the array form between cells. Finite element results indicate that different array configurations significantly affect the torsion angle of the HCTM. In an array with chiral symmetry, type-I cells exhibit the highest torsion angle, reaching a maximum of 6.6 degrees/%.