Invesitigation of mechanical behaviour of auxetic core sandwich composite panels produced by 3D printing

In this study, the effect of auxetic core structures with a negative Poisson's ratio on the mechanical performance of sandwich composites was systematically investigated using additive manufacturing (AM). Compared to conventional honeycomb structures with a positive Poisson's ratio, three different core configurations (re-entrant and improved re-entrant) were fabricated from polylactic acid (PLA) using the fused deposition modeling (FDM) technique. These core structures were then bonded with carbon fiber-reinforced epoxy surface layers to form sandwich composite panels. Tensile, three-point bending, and compression tests were conducted in accordance with ASTM standards, and Poisson ratios were determined experimentally. The results were then comparatively evaluated using finite element analyses (FEA). The results revealed that the cores with a negative Poisson's ratio significantly improved the mechanical performance of the sandwich composites. Among the tested designs, the improved re-entrant geometry achieved the highest strength values, reaching 160.83 MPa in the flexural test and 125 MPa in the compression test. These findings demonstrate that auxetic geometry design has the potential to improve the comparative mechanical performance of sandwich composites.