Tensile loading response of strut-based mechanical metamaterials fabricated using selective laser sintering process

Lightweighting with adequate mechanical strength is one of the key objectives of Industry 4.0. Replacement of solid parts with cellular lattice structured ones is one of the alternatives to elevate performance and reduce weight, without harming sustainability and carbon neutrality goals. Lattice structured parts possess several loads including tensile as the main type of loading; however, few researchers have studied the tensile response of mechanical metamaterials. This study aims to investigate the structural properties under tensile loading of four different types of mechanical metamaterials (simple cubic, octet, face-centered cubic, and body-centered cubic) fabricated using a selective laser sintering process using polyamide material. X-ray computed tomography was employed to examine the manufacturability of strut-based structures. Effects of relative densities, material distribution, deformation behavior, and fracture of structures on mechanical responses of each structure were evaluated at various relative densities of 40%, 50%, and 60%. Results exhibit that octet and FCC structures possess more elongation at higher relative densities compared to lower relative densities of the same structures. In addition, these structures fractured in a brittle manner at lower (40%) relative densities and this trend changes from brittle to ductile at higher relative density (60%). SC structure performed best (848 N) but the BCC (348 N) is worst at constant relative density (40%); thus, performance is significantly different due to different structure morphologies. The orientation of struts has a significant effect on the tensile loading of lattice structures. The structures having zero inclined struts fractured significantly different manner compared to their counterparts having inclined struts. The octet structure is considered to have a greater amount of elongation in the tensile direction while the SC structure has the highest load-bearing capacity.