The trapped gas effect on the dynamic compressive strength of light aluminum foams

Light aluminum closed-cell foams (4% relative density to solid aluminum) were experimentally studied in order to determine the added dynamic compressive strength facilitated by the trapped gas. A compression machine, an impact pendulum, and a shock tube were used to compress foam samples in strain rates varying from 10^-3 s^-1 to 700 s^-1. Very similar results were recorded from the compression machine and the impact pendulum experiments. The shock tube results exhibited a significantly higher compressive strength. An experiment was designed to isolate the compressive strength contribution from the gas trapped inside the foams. It was shown that, in light aluminum foams, gas compression contributes the additional dynamic stress. It was also shown that, in the samples used in this study, gas compression caused as much as 50% of the dynamic compressive strength. An isentropic model was used to analytically explain the gas contribution to the dynamic compression stress recorded in the experiments.