## 5 Conclusions
The NT3-T\({}_{\text{S}}\)+T\({}_{\text{S}}\) configuration, which involved two small CFRP tubes nested within a larger tube, achieved a significant mass reduction exceeding 27%, enhancing the  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Crushability**} & \multicolumn{2}{c}{**Sample**} & \multicolumn{2}{c}{**Sample**} & \multicolumn{2}{c}{**Frame**} & \multicolumn{2}{c}{**Emax**} & \multicolumn{2}{c}{**Absorbed**} & \multicolumn{2}{c}{**Specific Energy**} & \multicolumn{2}{c}{**Crush Force**} & \multicolumn{2}{c}{**Work**} \\  & **Sample Combination** & \multicolumn{2}{c}{**Ratio, e.g.,**} & \multicolumn{2}{c}{**Weight**} & \multicolumn{2}{c}{**(N)**} & \multicolumn{2}{c}{**(N)**} & \multicolumn{2}{c}{**Energy, EA, (J)**} & \multicolumn{2}{c}{**Absorption,**} & \multicolumn{2}{c}{**Efficiency,**} & \multicolumn{2}{c}{**Effectiveness,**} \\  & & \multicolumn{2}{c}{**(nm/mm)**} & \multicolumn{2}{c}{**(g)**} & \multicolumn{2}{c}{**(N)**} & \multicolumn{2}{c}{**EA, (J)**} & \multicolumn{2}{c}{**SEA, (Jg)**} & \multicolumn{2}{c}{**CFE, (\%)**} & \multicolumn{2}{c}{**Weft, (Jg)**} \\ \hline \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & T\({}_{\text{M}}\) & 0.82 & 46.5 & 812 & 1491 & 51.1 & 1.10 & 54 & 0.90 \\  & & T\({}_{\text{M}}\) & 0.81 & 39.2 & 1150 & 1640 & 55.7 & 1.42 & 70 & 1.15 \\  & & T\({}_{\text{S}}\) & 0.78 & 23.3 & 1952 & 4141 & 56.4 & 2.42 & 47 & 1.89 \\ \cline{2-11}  & & & NT2-T\({}_{\text{S}}\) & 0.78 & 69.8 & 1420 & 3865 & 85.7 & 1.23 & 37 & 0.96 \\  & & NT2-T\({}_{\text{M}}\) & 0.78 & 85.7 & 1649 & 2884 & 99.5 & 1.16 & 57 & 0.91 \\  & & NT3-T\({}_{\text{S}}\)+T\({}_{\text{S}}\) & 0.75 & 93.1 & 2772 & 5219 & 160.2 & 1.72 & 53 & 1.29 \\  & & NT3-T\({}_{\text{S}}\)+T\({}_{\text{M}}\) & 0.75 & 109 & 2484 & 5799 & 143.6 & 1.32 & 43 & 0.99 \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \hline \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}{**Effectiveness,**} \\  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \cline{2-11}  & & & & & & & & & & & \\ \hline \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Crush Force**} & \multirow{6}{*}{**Effectiveness,**} & \multirow{6}{*}  
specimen's overall efficiency despite a slight decrease in absorbed energy compared to aluminum nested specimens. Based on these findings, the NT3-T5+TM combination stands out as the optimal sample for maximizing energy absorption efficiency in nested tubular structures. Future studies should explore the integration of different material combinations and investigate the effects of varying tube dimensions and wall thicknesses on energy absorption characteristics. Additionally, dynamic impact tests and real-world crash simulations would provide further validation of the observed trends and enhance the practical applicability of the findings in automotive and aerospace safety design. Conceptualization, M.M.Y. and M.I.O. ; methodology, M.M.Y. and M.I.O. ; formal analysis, M.M.Y. and M.I.O. ; investigation, M.M.Y. and M.I.O. ; writing--original draft preparation, M.M.Y. and M.I.O. ; writing--review and editing, M.M.Y. and M.I.O. ; visualization, M.M.Y. and M.I.O. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable.