Mechanical performance of hollow tetrahedral truss cores

Abstract

Hollow tetrahedral truss cores composed of nanocrystalline nickel are fabricated and tested, and the resulting strengths compared to Nomex ® honeycomb, a sandwich core commonly in use in aerospace applications. We conduct a systematic finite element study to determine optimal geometric parameters of hollow tetrahedral truss cores given height and density constraints. We introduce nodal height truncation as an additional parameter for this architecture, and demonstrate that nodal truncation can yield further improvements in the shear and compression strength of truss cores. Informed by the finite element results, we proceed to fabricate specimens by additively manufacturing polymer templates, coating the templates with nanocrystalline nickel, and subsequently removing the templates resulting in free-standing, hollow truss cores. Mechanical testing demonstrates that judicious selection of the architecture of hollow truss cores results in structures with shear and compression strengths exceeding those of Nomex ® honeycombs at comparable densities.