Automobile chassis are constantly being redesigned to improve crashworthiness and decrease overall weight to assist in increased fuel efficiency. Typically, thin-walled axial members such as rectangular and circular tubes are employed as energy absorbers in front and side collisions. These members are designed to absorb a maximum amount of energy in a short period of time by utilizing their collapse behaviors. During collapse, these axial crush tubes undergo progressive folding which exhibits moderate and relatively constant plateau stress regions as collapse occurs. This study is a continuation of the investigation into cross-shaped crush tubes and the addition of a composite graded cellular core addition. The cross shaped tube and graded cellular core have shown to have distinct deformation modes and behaviors under axial loading conditions. Additionally, the work presented here further investigates this structure through the addition of crushable foam material within the cell voids. This foam addition along with bonding techniques of the inner core to external tube structure assist in altering the crush behavior of the tubes while increasing stability and energy absorbing capacity of the structure. Numerical simulations were conducted in ABAQUS finite element software for cross tubes under axial impact loading conditions. Four cases were considered for the present study: no bonding, 3 bonding sites, 5 bonding sites, and 7 bonding sites. These cases were matched with the previous study results to determine the effects of crushable foam addition to the graded cellular core structure. The results show that the addition of crushable foam material to the cellular core structure further increases the stability of the structure and is less susceptible to Euler type buckling. The crushable foam improved structural strength and increased overall energy absorbing capacity. The results presented are a positive indicator of the potential to tune automobile chassis energy absorbers to significantly increase energy absorbing potential and alter the behavior of these members to perform favorably under axial impact loading conditions.

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