Crushing Behavior of Functionally Graded Lattice

The mechanical performance of novel design body centered cubic (BCC) type bi-directional functionally graded (FG) lattices has been investigated experimentally and numerically. Uniform and uni-directional FG lattice structures were also studied for comparison. The three types of lattice structures were fabricated by multi-jet fusion (MJF) using polyamide 11 (PA 11). The results showed that the strength of the bi-directional FG structure was moderate in the initial stage of crush, as well as towards densification as compared with the uni-directional FG structure. Moreover, the strength of the bi-directional FG structure can be tailored by tuning the gradient. At the same density, both FG structures showed higher plateau stress than the uniform counterparts, and the bi-directional FG lattice had the highest plateau stress. Moreover, the FG structures demonstrated typical progressive collapse during the crush with stepwise-shaped stress–strain curves. The energy absorption capacity of the two FG lattices was also found to be slightly (around 10%) higher than that of the uniform structure with the same density.