Defect-sensitivity of stochastic and periodic minimal surface titanium cellular materials

The progression of additive manufacturing has paved the way for in-depth studies of various strut-, plate-, and sheet/shell-based cellular (meta)materials. Despite their promising mechanical properties, these metamaterials are highly sensitive to manufacturing defects. This study investigates the imperfection sensitivity of stochastic and periodic triply periodic minimal surface (TPMS) cellular materials by comparing imperfect additively manufactured samples to simulated defect-free lattices. Stochastic TPMS sheet-network lattices, using Schwarz-Diamond, Schoen−IWP, and Fischer-Koch S topologies, and their periodic counterparts, are investigated across various relative densities. Samples were additively manufactured using laser powder bed fusion of titanium alloy powder to evaluate the damage-tolerance of these cellular materials. Microstructural analysis was performed using micro-CT and SEM to assess 3D printability and defect density. Stochastic TPMS cellular materials demonstrated remarkable resistance to additive manufacturing defects compared to their periodic counterparts. In the presence of defects, stochastic TPMS sheet-based cellular materials maintain their stretching-dominated deformation behavior, whereas the deformation mode of the periodic counterparts was altered to a bending-dominated deformation. The reduced defect sensitivity allows superior mechanical performance of stochastic TPMS lattices at lower relative densities, where defects are most prominent. Numerical simulations indicate that defect-free periodic TPMS lattices display superior mechanical properties to their stochastic counterparts at all relative densities and show a clear effect of parent topology. This work expands on the understanding of the mechanical behavior of stochastic TPMS cellular materials and facilitates further improvements in their damage-tolerance and potential applications in various engineering fields.