Out-of-plane and in-plane compression of additively manufactured auxetic structures

Abstract

Auxetic structures exhibit negative Poisson's ratio (NPR) and offer valuable enhancement of mechanical properties. This study presents a combined experimental and numerical investigation of the out-of-plane and in-plane performances of a recently proposed auxetic structure, re-entrant chiral auxetic (RCA), under quasi-static uniaxial compression. The popular hexagonal honeycomb and re-entrant honeycomb were also studied as benchmarks for comparison. Specimens were fabricated by fused deposition modelling (FDM) process. It was found that printing quality depends on the size and complexity of the printed structures. Deformation mode, stress-strain curves and energy absorption of the three types of structure were studied and compared. Specific energy absorption per unit volume, Wv, and per unit mass, SEA, were calculated up to the strain at the onset of densification. Results show that the out-of-plane energy absorption of the proposed structure outperformed that of the other two benchmarks. In contrast, when comparing the energy-absorbing efficiency, the hexagonal honeycomb revealed the highest energy absorption efficiency of 65%, compared with 44% and 52% for the re-entrant and the proposed RCA structure, respectively. For the in-plane compression, the proposed structure exhibited a negative Poisson's ratio and demonstrated anisotropic mechanical performance.