Abstract
Additive manufacturing processes can be utilised to fabricate lattice structures with robust mechanical performance and high energy-absorbing capacity, which have garnered significant attention in various sectors, such as aerospace, automobile, and bioengineering industries. Despite the advantages of 3D printing technologies, such as fabricating highly complex workpieces at low costs, additive manufacturing processes can cause defects and imperfections in final products that might degrade the desired mechanical properties. To gain insights into the effects of process-induced defects on the mechanical performance of lattice structures, and to optimise the printing parameters and lattice design for obtaining structures with minimum imperfections, detailed characterisation of manufacturing-induced defects is necessary. This study investigates the characteristics of process-induced defects in a polymeric BCC lattice structure created via the powder bed fusion process. X-ray computed tomography (CT) techniques are used to scan the printed lattice. Then, image processing methods, utilising MATLAB scripts, are developed to extract the characteristics (morphology and distribution) of imperfections. The image processing results reveal that geometry-related defects (i.e. thickness variation and the deviation of strut cross-sectional shape) and internal voids exist in the 3D-printed sample. The distribution patterns of defects indicate that geometric imperfections are more pronounced near the strut junctions. Detailed characterisation of internal voids’ shape, including 3D dimensions, aspect ratio, and orientation, which have been rarely investigated in previous studies, are explored in this research. The morphology of internal voids and the correlation between the size of voids and powder particles suggest that lack of fusion has led to void formation.