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

TL;DR

This study uses numerical simulations to analyze how topology, porosity, and loading orientation influence size effects and effective elastic moduli in honeycomb cellular materials under various loadings.

Contribution

It provides a comparative analysis of beam and continuum models, revealing anisotropic size effects and the impact of pore shape on material behavior.

Findings

Honeycomb structures show significant anisotropy in size effects.

Circular pores lead to stronger size effects than hexagonal pores.

Negative size effects occur under bending and uniaxial loading.

Abstract

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.