Mechanical behaviors regulation of triply periodic minimal surface structures with crystal twinning

Triply periodic minimal surface (TPMS) structures have been realized as excellent mechanical materials with high specific strength, energy absorption, and unique layered deformation mechanism due to their saddle shape-surface with non-positive Gaussian curvature. However, the performance of TPMS structures is limited by anisotropic mechanical behavior owing to the oblique shear band with stress concentration when the load beyond the yield stress, resulting in structural catastrophic failure. Herein, a strategy is proposed to manipulating the path of stress transfer by introducing crystal twinning to achieve a designable deformation behavior of the TPMS structures. Various contact reflection twin boundaries for the gyroid (G) and diamond (D) surface structures have been introduced by connecting the ideal structures by mirror-symmetry while maintaining the structural integrity. Compression tests were carried out from various directions of perfect and twinned- G and D surface scaffolds after 3D printing. It was found that the twin boundary can effectively protect the structure from catastrophic failure by deflecting the cracks under compressive loads, and regulate the deformation behavior by various structural design. This study provides new insights in applying the microscopic crystal defects to macroscopic architectural materials, which also contributes to the understanding of these unique microscopic structures.