In-plane elasticity of a strengthened re-entrant honeycomb cell

This paper presents a stiffening method by which new inclined walls are added to the classical re-entrant honeycomb cell. This modification boosts the in-plane rigidity of the re-entrant cell without significant loss from auxetic behaviour. This study focuses on the in-plane elasticity moduli and negative Poisson's ratios along the principal axes. Analytical expressions that calculate the elasticity moduli and negative Poisson's ratios are derived; both finite element modelling and experiments reported in the literature validate the expressions of this work. Further, the variation in the in-plane elastic properties of the core cell is examined by altering the new wall's geometric, sectional, and material parameters. The results from the analytical expressions and the finite element models match very closely and demonstrate the boosted rigidity of the cell proposed in this work. This work also provides a benchmark of the new cell against the classical cell that can be used to tailor the in-plane elasticity moduli and negative Poisson's ratios to suit the needs of different applications.