The Mechanical Properties of Sandwich Structures Based on Metal Lattice Architectures

A range of metallic lattice structures were manufactured using the selective laser melting (SLM) rapid prototyping technique. The lattices were based assemblies of repeating unit-cells with their strands oriented at 0 degrees, +/-45 degrees, and 90 degrees to the vertical when viewed from the front. Mechanical tests on the strands and the lattice blocks showed that these systems exhibit a high level of reproducibility in terms of their basic mechanical properties. An examination of the compression failure mechanisms showed that the [+/-45 degrees] and [+/-45 degrees, 90 degrees] lattices failed in bending and stretching modes of failure, whereas the [0 degrees, +/-45 degrees] lattices failed as a result of buckling of the vertical pillars. Sandwich structures were manufactured by binding woven carbon-fiber reinforced plastic to the lattice structures. Subsequent three-point bend tests on these structures identified the principal failure mechanisms under flexural loading conditions. Here, cell crushing, hinge rotation, and gross plastic deformation in the strands were observed directly under the point of loading. Low-velocity impact tests were conducted on the sandwich beams and a simple energy-balance model was used to understand how energy is absorbed by the sandwich structures. The model suggests that the majority of the incident energy of the projectile was absorbed in indentation effects, predominantly in the core material, directly under the steel indenter.