Investigation On Plastic Dynamic Response Of Sandwich Plates With Cellular Metallic Materials Subjected To Foam Aluminium Projectile Impacting

Ultra-light cellular metal as an ideal material of absorbing energy has many advantages such as light quality, highly efficient energy absorption, and so on. They have been gradually applied to many fields, for example, aerospace aircrafts, high-speed rail vehicles, automotives, ships, etc. And cellular metallic materials are also used to energy-absorbing buffer and damping device of the buildings. One of the main using of cellular metallic materials is the sandwich structure with core of high-porosity porous metal. A typical sandwich structure is composed of two layers of thin composite material plate or metal plate and thick metallic foam core which includes grid, metal foam and lattice truss core. Face-sheets provide high bending resistance and tensile strength to structures. At the same time, cellular materials can have a larger plastic deformation under almost constant stress conditions. And then in the process of deformation a lot of energy is dissipated. These structures are mainly applied to occasions at which the structure-functional property is required, for instance, energy absorption, sound absorption, electromagnetic shielding, etc. A great deal of concern is taken on good properties of these structures to strong dynamic loading in the academic and in engineering field. As has become research focus of academia. But investigation on dynamic response of the sandwich structure is in its infancy. Much work is still imperfect. Therefore, it is necessary to further investigate dynamic response of the metallic sandwich plate to impact loading.Dynamic responses of clamped cellular sandwich plates and solid plates of the same weight are studied in the paper. Experimental investigation, theoretical analysis and numerical simulation are applied to finish work systematically. Some significant conclusions are drawn.Experimental results show that deformations of sandwich plates are mainly concentrated in the central region to projectile impacting. Deformation mode of the front face is mainly indenting in the region of impacting. Failure mode includes indenting and penetration failure. Failure mode of core includes compression and shearing in central region. Near this region less compression is observed. No deformation is found close to the clamped edges. Deformation mode of the back face is non-elastic large deformation. Maximum deflection is observed on central point of the plate and minimum is on the edges. Deformation of the flower pattern is observed around central point of the back face. Mode of the overall deformation is arched shape. It is found that main plastic deformation is concentrated in the region of projectile impacting subject to dynamic loading and is continuous. However, static plastic hinge lies in surrounding of indenter and in clamped edges due to different angle of plate to quasi-static loading, obviously.Parameters studied include impulse of projectiles, thickness of face-sheet, thickness of core and density of core. It is found that the cellular metallic plate can sustain larger impacting impulses than a solid plate of the same mass. And a sandwich plate with aluminum honeycomb core has a superior shock resistance relative to the sandwich plate with aluminum foam core. Thereby, the best performance of the structures can be provided by applying the sandwich plate with aluminum foam core in structures. Experimental results reveal that the response of the structure is sensitive to impulse of the projectile and density of core. Permanent deflection of the central point of the back face is proportion to impulse or density.An analytical model is developed to investigate dynamic responses of clamped sandwich plates and solid plates of the same weight subject to impulse loading over a central loading patch. Reliability of the model is supported by the experimental results. The analytical formulae are employed to determine optimal geometries of the sandwich plates that maximize the shock resistance of the plates for a given mass. It is found that increasing density of core can provide the better performance. Results also reveal that deflection of the back face of the sandwich plate is the smallest when the ratio of thickness of core to half side length of the plate is or so 0.12.Dynamic responses of foam projectile impacting cellular metallic sandwich plates are simulated using finite element code LS-DYNA.V970 on the HP-J6750 workstation. Numerical results are in good agreement with the experimental measurements. Comparison between direct loading by the foam projectiles and pressure loading shows that difference of shock resistance performed by sandwich plates and solid plates of the same mass is mainly determined by the property of the structure itself. In the deformation process of the sandwich plate energy absorbed by the front face and core are more than energy by the back face. It is also found that capacity of shock resistance provided by increasing thickness of core is better than by increasing thickness of face-sheet of the same weight. The sandwich plate with aluminum honeycomb core has a superior shock resistance relative to the sandwich plate with aluminum foam core of the same mass to a certain impulse.