Characterisation of process-induced defects in polymeric strut-based lattice structures produced by the powder bed fusion additive manufacturing process

Abstract

Purpose The purpose of this study is to introduce methodologies for detailed characterisation of process-induced defects in 3D printed lattice structures, independent of the manufacturing process. Detailed characterisation of imperfections, particularly internal voids, including their geometry and distribution, provides insights into their impact on the mechanical properties of lattice structures. Furthermore, the correlation between defect severity, distribution and printing conditions, such as the printing direction, can be captured using the proposed methods. These correlations can be used to optimise printing parameters and lattice designs to achieve workpieces with minimal imperfections. Design/methodology/approach Due to the significant role of polymers and their composites in diverse industrial sectors, such as bioengineering, and the existing research gap regarding the impact of process-induced defects on the mechanical properties of polymeric lattices, the cellular structures were fabricated from the polymer in this study using the selective laser sintering process. To characterise additive manufacturing-induced defects in polymeric lattice structures, X-ray computed tomography is employed to scan the printed lattices, and image processing techniques using MATLAB scripts are developed to extract and analyse the characteristics of inspected defects, including their morphology and distribution. Findings This study reveals that polymeric lattice structures manufactured by powder bed fusion exhibit various defects, including geometry-related imperfections and internal voids. Geometry-related defects are more pronounced near strut junctions, with significant variations in strut thickness and cross-sectional shape. The analysis of voids’ morphology indicates that the lack of fusion during additive manufacturing leads to their formation, with voids exhibiting diverse shapes, sizes and orientations. This highlights the importance of detailed characterisation of process-induced voids and their incorporation into the structural analyses to improve the accuracy of the mechanical performance predictions for lattice structures. Originality/value The novelty of this work lies in the detailed characterisation of voids within manufactured polymeric lattices, including their 3D dimensions, aspect ratio and orientation. This comprehensive analysis of process-induced voids offers new insights into their impact on the mechanical performance of lattice structures, addressing the limitations of prior research that often simplified voids as spheres and overlooked the influence of void geometry on the mechanical properties of lattices. Furthermore, the methods developed for defect characterisation, especially for internal voids, are applicable to any lattice unit cell topology, regardless of the additive manufacturing method or material used.

Topics & Concepts