Crashworthiness and Energy Partitioning in Monolithic and Layered Thin-Walled Metallic Tubes under Axial Impact

Thin-walled metallic tubes are widely used as energy-absorbing components in structures subjected to impact loading due to their high crashworthiness efficiency. While the axial impact behaviour of monolithic tubes has been extensively investigated, the response of layered thin-walled tubes remains insufficiently understood, particularly in terms of deformation characteristics and energy dissipation mechanisms. In the present study, a detailed finite element investigation was carried out to evaluate the crashworthiness of circular as well as square hollow mild steel and aluminum tubes of 200 mm length, with three different cross-sectional sizes in monolithic and layered configurations subjected to low-velocity axial impact of a 350 kg rigid mass. The numerical simulations were performed using ABAQUS/Explicit, employing S4R shell elements and a strain rate-dependent Johnson–Cook material model. Contact interactions, including interlayer friction, were incorporated using general contact algorithm with penalty friction to accurately capture the response of layered systems. The deformation behaviour, total energy absorption, and energy partitioning into plastic, elastic, and frictional components were systematically evaluated and compared. The results showed that layered tubes exhibit significantly higher axial deformation compared to monolithic tubes, with increases of up to 51.53% for circular sections and about 15% for square sections, depending on size. However, monolithic tubes demonstrate slightly higher total energy absorption due to dominant plastic energy dissipation. Circular tubes consistently outperform square tubes in terms of crashworthiness performance owing to their stable deformation modes and uniform stress distribution. The study highlights interlayer interaction effects, providing useful insights for the design of efficient energy-absorbing structures.