A material used in running shoes and memory foam pillows has inspired the design of a 3D-printed product that could help protect buildings from collision damage and other high impact forces, equivalent to a car travelling at 60km/hr.
Published in Smart Materials and Structures, Dr Tatheer Zahra from the QUT Centre for Materials Science and QUT School of Civil and Environmental Engineering used off-the-shelf bioplastic to 3D print geometric shapes that mimic the behaviour of auxetic materials.1
- 1. "Rather than flattening when stretched or bulging when compressed, auxetic materials expand or contract in all directions at once, which makes them highly energy-absorbent and load resistant," Dr Zahra said. "But existing commercial auxetic material is expensive and not locally available, so I designed geometric shapes that achieved the same behaviour."
Tatheer Zahra. Behaviour of 3D printed re-entrant chiral auxetic (RCA) geometries under in-plane and out-of-plane loadings. Smart Materials and Structures, 2021; 30 (11): 115011 DOI: 10.1088/1361-665X/ac2811
Three-dimensional printing of auxetic materials is an emerging research field due to their intriguing negative Poisson's ratio (NPR) behaviour which enables improved load resistance than conventional materials for various applications. In this research, re-entrant chiral auxetic (RCA) structures of three different geometries were printed using polylactic acid (PLA) filament. The PLA material was also characterised in compression and tension. In total, 27 RCA specimens of varied cell sizes were designed, printed and tested under in-plane tension and compression and out-of-plane bending loads. Digital image correlation method was employed to study the failure modes, displacement profiles, load–displacement curves and ductility characteristics. Results showed that the samples with the smallest cell sizes exhibited the highest resistance against compression, tension and out-of-plane loading. The elastic modulus and Poisson's ratio was also higher for these geometries with the maximum NPR of −9 in compression and −5 in tension. In comparison, the larger cell geometries due to wider gaps between the cells showed higher deformability which resulted in high energy absorption characteristics in compression and tension. Whereas in out-of-plane bending, all designed geometries, irrespective of cell sizes exhibited similar deformability with the maximum ductility obtained for the RCA structures made of smaller cells.