A node-optimized metamaterial with high mechanical properties and heat insulation

Abstract

Lightweight metamaterials with high strength and superior heat insulation are crucial for hypersonic aircraft to resist mechanical and thermal shock under ultra-high speed conditions. However, an inverted relationship between mechanical properties and heat insulation leads to difficulties in their synergy improvement by controlling relative density. Therefore, innovative design of metamaterials for mechanical properties, heat insulation, and their successful fabrication are paramount, but often laborious because of the vast design space, associated complex mechanical-thermal physical models with spatial configuration, and their complex configuration with micron size. This work proposed a node optimization strategy for mechanical-heat insulation synergy improvement. Taking the previous bionic polyhedron metamaterial (BPM) imitated pomelo peel as an example, the node-optimized octahedron metamaterial (OCM) fabricated by laser powder bed fusion (LPBF) achieved superior heat insulation and high strength. Based on experiments and numerical simulations, the OCM with a unit cell size of 3 mm (OCM3) had equivalent thermal conductivity (ETC) of 0.72 W/(m·K) and 2.19 W/(m·K) at room temperature and 600 °C with 8 % relative density, respectively, its heat-shielding index was 77 % at the load plate with 370 °C in natural convection. Furthermore, the OCM3’s strength and Young's modulus were 23.71±0.75 MPa and 981.44±19.44 MPa at room temperature; At 600 °C, its strength and Young's modulus were 12.52±0.82 MPa and 376.97±12.78 MPa, respectively. The above finding will guide the design and optimization of metamaterials with high strength and exceptional heat insulation.