Energy-absorption analyses of grooved Al-sheet stacks using modified split Hopkinson pressure bar

Abstract

This study suggests that stacks of thin aluminum (Al) sheets with fine rectangular or triangular grooves are effective materials for energy absorption. The energy-absorbing performance of these materials was evaluated using a modified split Hopkinson pressure bar (SHPB). Two important energy-absorbing parameters, impact momentum (I) and maximum impact acceleration (amax), were measured from stress-time (sigma-t) curves. These parameters were found to vary with groove shape, groove cavity fraction, and specimen thickness. Both I and amax showed a continuous decrease as the specimen thickness increased from 6 to 18 mm or as the groove cavity fraction increased from 29-30% to 38-39%. Analyzing the sigma-t curve shapes revealed that the triangular grooved specimens exhibited broad-peak shaped curves, resulting in a greater reduction in I compared to the broadened plateau shape observed in the rectangular grooved specimens. Taking into account both I and amax, the overall energy-absorbing performance of the triangular grooved specimens was better than that of the rectangular grooved specimens. Notably, in the triangular grooved specimens with a high cavity fraction, the triangular embossing intruded into the groove cavities, resembling a 'zipper' mechanism, further enhancing the effectiveness of energy absorption. This study presents a promising approach for developing various grooved Al sheet stacks that exhibit reduced amax and I by strategically exploring suitable groove shapes, cavity fractions, and stack thicknesses, especially in dynamically compressed artillery environments.