Study On Crashworthiness Of Functionally Graded Density Aluminum Foam-filled Tapered Thin-walled Structures

To utilize functionally graded density aluminum foam-filled tapered sections to a vehicle crash-box, and to design and optimize aluminum foam-filled tapered tubes under oblique loading, a better understanding on the energy absorbing capacity of aluminum foam-filled tapered tubes and accurate numerical analyses are needed. And the nature density increase of aluminum foam should be a consideration in aluminum foam energy absorbing applications. The present study investigates the application of aluminum foam as energy absorbing filler in a vehicle crash-box structure.For this study, comparative tests and simulations of square and hexagonal hollow thin-walled structures, functionally graded aluminum foam tapers, and aluminum foam filled structures undergoing axial quasi-static compressive loading are performed and presented. Deformation mode, load vs. displacement curve, Absorbed Energy(AE) and Specific absorbed energy(SAE) defined as energy absorbed per unit mass, are compared.The numerical material parameters are all obtained from the experimental data of the standard testing process. Deshpande and Fleck constitutive model(2000)considering various densities published by Hanssen et.(2002) for aluminum foam is used and implemented in the explicit LS-DYNA software. For a better understanding and comparison on the energy absorbing capacity of different shapes and structures,numerical simulations with identical loading and model definitions are conducted.By comparing the deformation mode and crashworthiness indicators, it is found that under quasi-static uniaxial compression, cross-section shape of the aluminum foams and foam-filled structures has limited influence on the energy absorbing capacity. It is also found that the energy absorbing capacity of an aluminum foam-filled tapered section is greater than the combined energy capacity of individual aluminum foam and tapered section. Additionally, practical conclusions from experimental studies on foam density increase of functionally graded aluminum foam and interface fit of aluminum foam-filled structures are presented.The present study shows potential application of functionally graded aluminum foam filled tapered sections to energy absorbing structures.