Invar alloy metamaterial with high vibration and thermal expansion stability

Metamaterials exhibiting extraordinary performance usually stem from the intentional promotion of one selected property, and the sacrifice of other secondary properties. In this study, by combining the strength of additive manufacturing and microstructural design, a type of ‘double-zero’ mechanical metamaterial has been proposed to realize quasi zero coefficient of thermal expansion (QZCTE) and quasi zero stiffness (QZS) at the same time. The curved unit cell is designed by symmetrically embedding multiple curved beams into planes or curved surfaces, and the parametric study is applied to program stiffness to achieve quasi zero stiffness and to verify static characteristics compared with the planar unit cell. Specimens are fabricated from Invar alloy by laser powder bed fusion (LPBF) and experimentally verified within the temperature range of 30–120 °C. Electron backscatter diffraction (EBSD) is produced to analyze the variation of coefficient of thermal expansion (CTE) at two orthogonal build orientations. The measured CTE of the metamaterial reaches 2.2 ppm/K, while the vibration isolation frequency is maintained below 35 Hz regardless of ambient temperature. The high thermal-mechanical stability and well vibration attenuation performance of the proposed metamaterial provide new ideas for the design of new multifunctional metamaterials.