stiffest possible infill

thingiverse

This could be used as an infill for 3D printed parts. It is a combination of simple cubic infill with an octahedral infill (an octet truss with filled-in faces) that is half the size. This creates a "cubic-octahedral" infill. **It comes from this paper:** "Mechanical metamaterials at the theoretical limit of isotropic elastic stiffness". https://www.nature.com/articles/nature21075 doi: 10.1038/nature21075 The orientation was chosen so that no planes are coplanar to the printbed, which means a bit of the symmetry of the whole block is sacrificed. Related discussion: https://plus.google.com/+NicholasSeward/posts/hDYhP91YNph The foam achieves the Hashin-Shtrikman upper bounds on isotropic elastic stiffness. There may be other foams that perform equally well, but there are no provenly better foams. **Edit 2018-02-19:** A quicker rendering source file and smaller models were added, which print in a more reasonable time. The original version (v1) was too big, and the second version (v2) was too solid.