Energy Absorption Characteristics of Graded Foams Subjected to High Velocity Loading

Abstract

In this study the effect of layer stacking arrangement on the energy absorption characteristics of density-graded cellular polymers subjected to high velocity impact is investigated experimentally. Dynamic loading is performed using Split Hopkinson Pressure Bar (SHPB) which is also modified for a direct impact experiment. Different bulk density polymeric foam layers are bonded together in different stacking arrangements and subjected to impact loading. Ultra-high speed imaging is implemented to measure the deformation and observe the formation and propagation of compaction waves during direct impact. The effect of the orientation of the discrete layers on the dynamic stress-strain response is analyzed using digital image correlation (DIC). The effects of material compressibility are implemented to the analysis. The approach uses DIC to calculate the full-field acceleration and material density, later used to determine the stress gradients developed in the material. The best arrangement of layer structure is chosen by the highest energy absorption characteristics measured. Failure mechanisms associated with energy dissipation in graded materials are discussed.