Optimal design of functionally graded foam material under impact loading

With appropriate design, functionally graded metallic foam can show definitely better properties than homogeneous counterpart due to its better designability. In the present work, functionally graded aluminum foam blocks subjected to ball impact are investigated numerically by using nonlinear finite element code. Blocks with different density gradient distributions, various geometric parameters and under different impact velocities are analyzed. The block with linear decreasing density gradient is found to possess excellent performance in energy absorption and outperform blocks with other density distributions under middle to high speed impact. To obtain the optimal design of the functionally graded foam block, a structural optimization problem with the objective of maximizing the crush force efficiency is solved by response surface method (RSM). The thickness and density of each layer are selected as design variables and it is interesting to find that the optimum design shows gradually decreasing density distribution.