Compressive mechanical properties of open-cell cubic and rhombic dodecahedron lattice structures of variable cross section fabricated by fused deposition modeling

Abstract

Foams are known as structures with a high percentage of empty spaces and pores within them. Foams are classified into two categories, open-cell, and closed-cell, depending on their geometry and structure. Investigation of open-cell foams with non-uniform cross sections has been among the topics of recent studies. This research investigates the static analysis of cell foams fabricated through the additive manufacturing method. For this purpose, two structures with rhombic dodecahedron and cubic unit cells were placed under static loads using experimental, analytical, and numerical approaches. Thus, both unit cells with different relative density samples, were made with non-uniform cross-sections and validated with numerical values. Furthermore, the mechanical properties from analytical relationships were obtained for a uniform cross-section and further validated with numerical values. The open-cell porous structure built by additive manufacturing for Polylactic acid was investigated. The samples were tested under uniaxial compression with a constant strain rate, and the data obtained from the test was used to assess the structure's mechanical properties. For the analytical section, Timoshenko beam theory was utilized. Timoshenko beam theory was used in analytical solutions close to numerical results regarding yield stress, elastic modulus, and Poisson's ratio. In both unit cells, yield stress and elastic modulus were found to be increased proportionately with increasing relative density, in uniform and non-uniform conditions. By comparing the unit cells' yield stress, the impact of non-uniformity used for rhombic dodecahedron was found to be greater than cubic.