Limiting strain for auxeticity under large compressive Deformation: Chiral vs. re-entrant cellular solids

Under compression, auxetic open cell cellular solids may lose auxeticity due to instability and/or self-contact between the ribs. This study explores the limiting strains for preserving auxetic effects for auxetic open cell materials of two different cellular structures: re-entrant honeycomb and the ‘missing-rib’ type chiral cellular solids. Experiments of the 3D printed specimens, periodicity analysis, and ellipticity analysis showed that, under compressive loads, the auxetic effects and the limiting compressive strain for auxeticity are mutually exclusive. In other words, the limiting compressive strain has to be reduced if larger auxetic effect is desired, vice versa. It was found that compared with re-entrant honeycombs, due to chirality-induced rotation, the chiral cellular solids can preserve auxetic effects under much larger compressive strain (>−10–30%).