Dynamic crushing behavior of random and functionally graded metal hollow sphere foams

Dynamic crushing responses of metal hollow sphere (MHS) foams with uniform, graded and random cell wall thicknesses were investigated. FE models are constructed for such foam structures based on hollow sphere model with different degrees of cell wall thickness non-uniformity. The plateau stress, the densification strain energy and the deformation modes are determined by using the FE models. The numerical results illustrate that the inertia effect has obvious influence at the impact side, but insensitive at the stationary side. Both the dynamic plateau stress and the densification strain energy at the impact side increase with increasing of crushing velocity, relative density and matrix material strength. The deformation modes of all models appear with three types which are the whole deformation, transitional deformation and the “I” shaped deformation. By comparing with the tradition model, result shows that density graded foam with the biggest density as the first impacted layer and least density as the last layer has some benefits in terms of maximum energy absorption with a minimum force level transmitted to the protected structures.