<p class="MsoNormal" style="text-align: justify">Thin-walled crush tubes and other axial members are often employed as energy absorbers in vehicle chassis to improve crashworthiness of front and side chassis members. Thin-walled axial crushing members are primarily used due to their high strength to weight ratios. Previous works cover extensively the study of thin-walled members under axial crushing loads. Additionally, work has been done exploring the effects of core addition to a standalone thin-walled structure. Previously, investigation on the addition of composite functionally graded hexagonal extruded cores proved to increase energy absorption capacity and improve stability of the structure. The present study is a continuation of the previous work on functionally graded core material addition to thin-walled crush tubes. Functionally graded cellular structures are often employed to enhance energy absorption due to their high strength and stability with minimal added weight burden. Additionally, this study investigated the addition of crushable foam material to the volume of the cellular structures. This study was conducted utilizing ABAQUS/Explicit dynamic modeling environment. A cross-shaped thin-walled crush tube of side length 25.4 mm, 3.048 mm wall thickness, and 160 mm length was modeled as a 3D deformable shell with addition of transverse extruded graded cellular structure. The crushable foam material was modeled using a uniquely designed 3D deformable solid and introduced to each cell of the functionally graded structure. The tube and cellular structure were discretized using 4-point shell elements with reduced integration and hourglass control. The impact plate was modeled and meshed using 4-point rigid shell elements. The structure was fixed on one end and impacted by a plate with an initial velocity of 35 mph (15.64 m/s).&nbsp; Material properties and general contact conditions were assigned to the tube wall, cellular core, impact plate, and crushable foam material to define surface interaction between the structure materials. Energy absorbing characteristics such as crushing/reaction force, deformation modes, plateau stress, energy plots and crush stroke were used to determine performance of the structure. The addition of graded cellular core material with crushable foam provided increased energy absorption capacity of the structure through increased structural stiffness and decreased crush stroke. The structure exhibited progressive folding/collapse mechanisms with a more global crushing response as compared to an empty tube structure. Increasing number of localized collapse zones promoted increased energy absorption and structural stability and capacity. As compared to previous graded cellular core structures, the crushable foam addition promoted a more global structural response and allowed for total energy absorption before structure densification. The addition of core materials within thin-walled crush tubes have shown positive influences on energy absorbing capacity and overall performance of crush tube members.</p>

Dynamic Response of Cross Tube With Crushable Foam-Filled Cellular Core

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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