Experimental verification of a novel hierarchical lattice material with superior buckling strength

Abstract

Recently, a systematic approach for the design of lattice materials with extreme buckling strength has led to optimized hierarchical lattice materials with unprecedented load carrying capacity. This is obtained at the cost of a small decrease in linear stiffness. However, the superior buckling resistance of such optimized hierarchical lattice materials has so far only been predicted numerically. In fact, concerns have been raised regarding the validity of the employed linear buckling analysis and potential risk of catastrophic failure due to the coalescence of multiple critical buckling modes. This work aims at refuting these concerns by designing and testing manufacturable novel hierarchical lattice materials with superior buckling strength. Thereby, the basis is provided for wide applications of these high-performing materials in mechanical design. A novel hierarchical material is generated for this work by combining the mentioned design procedure with a requirement on the minimum feature size to ensure manufacturability. For addressing the raised concerns, the optimized material design, together with a reference material, is realized with the help of additive manufacturing and experimentally tested in uniaxial compression. The obtained results are compared to numerical simulations considering geometrical and material nonlinearities, and an overall good agreement is found between experimental and numerical results. This confirms an increase in buckling resistance and post-buckling load carrying capacity by a factor of more than three compared to the regular reference lattice structure. Hence, the buckling superiority of this novel type of architected materials is clearly demonstrated.