Characterisation of reinforced body centered cubic, octahedral-type and octet truss lattice structures

Developments in additive manufacturing have encouraged a dramatic increase in the production and integration of the space-filling unit cells known as lattice structures. As designers begin to leverage the useful benefits provided by lattice structures, and these structures are used more frequently in industrial designs of parts, there is a need to characterise the properties that different lattice structures possess to aid the design process. The functional requirements of a specimen will often change during the design stage and this means that a designer will always wish to select the most applicable lattice structure for the optimal result. To date, there is no repository of lattice structure design properties from which a designer can choose a structure that best suits the design requirements. This article aims to propose a methodology for testing the capabilities of lattice structures and building a database of unit cell type design properties through compression and 3-point bending tests. The samples were created with PA2200 manufactured through the selective laser sintering process on an EOS P396. The lattice structure specimens were parameterised in terms of overall specimen unit cell size and strut diameter. Through regression analysis, particular benefits of lattice structures were noted: Reinforced Body Centered Cubic (RBCC) performed best in bending, Octet Truss performed best in compression and Octahedral performed worst in both tests but resisted much greater deformation. Additionally, though increases in strut diameter or number of unit cells per sample increased both Young’s Modulus and Ultimate Compressive Strength, it was strut diameter increases that had a factor of 10 greater of an effect. To complete a repository, it is desirable to increase the number of stages per design parameter and test over a greater range of values - to fully model the shape of the output curve.