The purpose of this paper is to investigate the compression behaviour of a topology-optimized re-entrant star auxetic structure of Inconel 718 additively manufactured through laser power bed fusion. A set of topology-optimized designs is studied to understand their effects on Poisson’s ratio and deformation patterns by experimental and numerical methods.
In this work, the topologies of re-entrant star auxetic structures are iterated by parameters such as cell size (CS) of 2 and 3 mm and relative density (RD) of 30%, 50% and 70% through ANSYS workbench. The test specimens are subjected to compression tests and finite element analysis (FEA). The deformation modes are studied to confirm the occurrence of auxetic behaviour induced by negative Poisson’s ratio (NPR). The microstructure of the fractured test specimens is studied using a field emission scanning electron microscope (FESEM) to illustrate the microstructure after the experimental test.
The deformation patterns and Poisson’s ratio of FEA confirm the experimental compression test under quasistatic conditions. The contraction of the re-entrant star auxetic structure is observed when subjected to axial compressive load because of NPR. FESEM micrographs reveal shear burrs, crack propagation, widening, and extension resulting in uniform collapse with improved strength. The inferences of FESEM micrographs confirm that higher relative densities optimize stiffness and lead to uniform collapse, while lower densities show more pronounced deformation.
During the compression test, the samples with a CS of 2 and an RD of 70% have reached the ultimate compressive stress of 556 MPa. The peak NPR is observed as −1.73, which contributes to auxetic behaviour. The contraction of the re-entrant star auxetic structure absorbs more energy when compared to conventional and lattice structures, making it suitable for aero-turbine applications.
