Experimental and analytical studies of mechanical properties of additively manufactured lattice structure based on octagonal bipyramid cubic unit cell

In this study, analytical relationships were developed to calculate the mechanical properties including elastic modulus, Poisson's ratio, and yield stress of a new porous material based on the regular polygonal transversely isotropic micro-architecture called octagonal bipyramid. Stiffness matrix of the lattice structure was extracted based on superposition principle method using Euler-Bernoulli beam theory equations. The octagonal bipyramid unit cell has a higher stiffness than other shapes due to its triangular faces, vertical, horizontal, and inclined trusses, as well as having eight node connections in the lattice configuration. Analytical results were validated by utilizing the finite element modeling of the structure in Abaqus software. Also, additively manufactured porous lattice structure was fabricated by FDM method and compressive test experiments were performed to determine its mechanical properties. Then, digital image correlation (DIC) method was used to calculate the Poisson's ratio during compression test. The analytical results are in good agreement with the numerical and experimental results. Finally, the effect of changes in the geometric parameters of the unit cell was evaluated on the mechanical behavior of the structure including elastic modulus, Poisson's ratio, and yield stress in the X and Y directions.