Paper detail

Influence of Topology and Porosity on Size Effects in Stripes of Cellular Material with Honeycomb Structure under Shear, Tension and Bending

Cellular solids are known to exhibit size effects, i.e., differences in the apparent effective elastic moduli, when the specimen size becomes comparable to the cell size. The present contribution employs direct numerical simulations (DNS) of the mesostructure to investigate the influences of porosity, shape of pores, and thus material distribution along the struts, and orientation of loading on the size effects and effective moduli of regular honeycomb structures. Beam models are compared to continuum models for simple shear, uniaxial loading and pure bending of strips of finite width. It is found that the honeycomb structure exhibits a considerable anisotropy of the size effects and that honeycomb structures with circular pores exhibit considerably stronger size effects than those with hexagonal pores (and thus straight struts). Positive (stiffening) size effects are observed under simple shear and negative (softening) size effects under bending and uniaxial loading. The negative size effects are interpreted in terms of the stress-gradient theory.