Nonlinear compressive stability of hyperelastic 2D lattices at finite volume fractions

A framework is introduced for benchmarking periodic microstructures in terms of their ability to maintain their stiffness under large deformations, accounting in a unified manner both for buckling and softening due to geometric and material nonlinearities. The proposed framework is applied to three classical 2D lattice microstructures at different volume fractions as well as to an optimized hierarchical microstructure from the literature. The high slenderness of the structure members, often assumed in analyses, is demonstrated not to be valid at volume fractions of 10% and above, with the infinitesimal volume fraction solutions underestimating the actual buckling resistance considerably. The performed analyses provide useful and quantitative insight regarding the compressive load carrying capacity of materials with a moderately dense periodic microstructure, in a rather universal and practical form.