Compressive and energy absorption properties of CoCrMo 3D auxetic lattice structures fabricated by L-PBF

Lattice structures are highly porous architectures that can be integrated into applications that focus on the minimisation of weight while maintaining control over the mechanical response and resulting properties. To this end, this study presents the design, manufacturing, and characterisation of a novel triply periodic minimal surface (TPMS) lattice structure that exhibits auxetic deformation behaviour. Cylindrical samples of different variations of the TPMS lattice were designed and fabricated by laser powder bed fusion (L-PBF) with the cobalt chromium molybdenum alloy (CoCrMo) as feedstock material. These comprised three variations of homogeneous samples based on a magnification factor and an additional sample variation with a gradient in thickness. To comprehend the potential effect of manufacturing defects on deformation behaviour, optical microscopy was performed. Subsequently, compressive testing was performed to measure the auxetic behaviour and the mechanical properties. The homogeneous lattice structure showed auxetic behaviour in compression testing with apparent Poisson ratios of up to ν = −0.1443, accompanied by an energy absorption of up to 37.93 J/cm³, and compressive strength values of up to 231.44 MPa. The gradient lattice structure mechanically underperformed compared to the homogeneous sample variations. However, the gradient structure exhibited a recovery of the plastic deformation region after initial failure and densification, which can have specific applications. This study specifically addresses energy-absorption-related applications in the biomedical domain that require control over a structure's weight, permeability, and mechanical properties. Nonetheless, one can consider applications for this novel TPMS lattice structure in other fields such as aerospace, precision engineering, or thermal management.