Experimental and analytical investigation of mechanical behavior of laser-sintered diamond-lattice structures

Typically, additive manufacturing (AM) processes are limited to a single material per build while many products benefit from the integration of multiple materials with varied properties. To achieve the benefits of multiple materials, the geometric freedom of AM could be used to build internal structures that emulate a range of different material properties such as stiffness, Poisson's ratio, and elastic limit using only a single build material. This paper examines a wide range of properties that can be achieved using diamond lattice structures manufactured from Nylon 12 with a commercial laser sintering (LS) process. Stiffness and energy absorption were measured for all lattices and the stiffness response was compared to finite element analysis (FEA). Simulation shows agreement with experimental results over a stiffness range of four orders of magnitude once a correction factor is applied. Experimental results also show a wide range of energy absorption for diamond lattice structures and a significant increase in the effective elastic limit of the build material, which compensates for the low ductility of many AM materials. The elastic limit decreases with an increasing t/L ratio meanwhile the degradation under cyclic loading is relatively independent of the t/L ratio. Extrapolating this data into lattice structures made from metal, these same structures could mimic a wide range of "fully" dense and porous materials with just the use of a single material. Since the diamond lattice is a cellular structure, the voids can also be filled with other materials or structures to add secondary control of embedded functions such as energy storage and sensing.