Mechanical property of 3D-printed plastic cylinders with 2D or 3D infill patterns

3D printing technology  enables the creation of complex internal structures within elements. This research introduces the use of a bio-inspired 3D infill pattern, the Gyroid, to fill the inner space of plastic cylinders. Mechanical properties were analyzed under varying unit cell sizes and infill densities using compression tests combined with Digital Image Correlation (DIC) systems, and these results were compared to references using 2D infill patterns.  Local stiffness was investigated based on the symmetry of infill patterns, providing a quantitative measure of stiffness. Global stiffness was determined by analyzing the distribution of elastic modulus within representative sections. The mean value of global stiffness was used for comparison with other elements, while the standard deviation indicated the homogeneity of stiffness. Strength characteristics were also assessed.  Our findings reveal that increasing infill density from 20% to 30% has a minimal impact on mechanical properties. Interestingly, in uniaxial compression tests, elements with 2D infill patterns exhibited higher stiffness and strength compared to those with 3D infill patterns. However, 3D infill patterns contributed to a more even distribution of elastic modulus, enhancing performance under complex loading scenarios. Furthermore, the combination of DIC systems allowed us to observe the deformation of the entire element during compression and study the rotation of the infill pattern. These results offer valuable insights for the selection and design of elements incorporating 3D-printed infill patterns, with potential applications in engineering and design.