Investigation of Beam Finite Element Models of Octet-Truss Unit Cell Using Homogenization

This study investigates the beam model accuracy of octet-truss lattice solid cell in the calculation of homogenized material properties using the average stress method with Ansys finite element program for a range of relative density 0.01-0.5.While alignment is observed at lower relative densities (less than 0.1), the beam model underestimates results at higher densities, revealing reductions in elastic and shear modulus values.The study critically examines existing beam model modifications in literature, traditionally centred on increasing strut stiffness at joint regions, particularly for lattice materials under compression testing.The studies found in the literature ultimately produced multiple parameter pairs by considering only the modulus of elasticity.The procedure for determining these parameters is graphically illustrated in detail considering also the shear modulus and it is concluded that both modulus values could not be fit to the solid model results with this type of modification.Closed expressions for the moduli of octet-truss lattice material are presented to be used for the relative density range higher than 0.1, to keep the error under ten percent.