Experimental and numerical investigation of impact behavior of nested tubes with and without honeycomb filler

In this study, the axial impact behavior of empty and filled nested tubular structures is parametrically investigated both experimentally and numerically. The experiments are conducted by a drop test machine and the numerical studies are conducted using LS-DYNA software. The tubes are made of AL6063 aluminum alloy and a regular hexagonal honeycomb filler of ABSplus plastics. The external sizes of all specimens are held constant for meaningful comparisons. The primary objective of this study is to investigate the effects of using a honeycomb filler, increasing the numbers of tubes, and changing the lengths of the tubes on the nested tube structures. The results of single, double, triple, quadruple, and quintuple tubular structures, with and without the honeycomb filler, are compared in terms of collapse mechanism and common crashworthiness indicators, namely, peak crash force, specific energy absorption, and crash force efficiency. The results indicate that the honeycomb filler has a significant effect on the collapse mechanism of single and nested tubular structures, and the filled nested tube systems with fewer tubes are better than empty ones in terms of specific energy absorption and crash force efficiency. In addition, the energy absorption of the nested tubes could be increased in certain cases with the increase in the number of tubes and tube lengths increasing from the innermost to outermost tubes. Therefore, the double nested tube structures with a honeycomb filler are recommended for crash box designs.