Cosserat sigmoid bulge effects in the bending of a lattice of tetrakaidecahedron cells

A lattice of tetrakaidecahedron (truncated octahedron) cells is observed to have a Poisson’s ratio near 0.45 and to exhibit a sigmoid bulge deformation of the lateral surfaces in addition to the tilt expected via classical elasticity. The sigmoid curve is consistent with Cosserat elasticity, with a characteristic length about twice the cell size. By comparison, in other rib lattices the characteristic length was typically less than or equal to the cell size and in foams, more than five times the cell size.