The Mechanical Behavior Of Clamped Shallow Sandwich Arches Subjected To Impact And Quasi-Static Loading

Metal foam sandwich structures, obtained by combining metal face sheets with a lightweight metal foam core, have peculiar properties (low specific weight, efficient capacity of energy dissipation, high impact strength, acoustic and thermal insulation, high damping, etc.), that made them interesting for a number of practical applications, such as the realization of lightweight structures with high mechanical strength and good capacity of energy dissipation under impacts. Therefore, they have been applied to many fields, for example, aerospace aircrafts, high-speed rail vehicles, automotive, ships and so on.In this paper, the structural response of clamped shallow sandwich arches with aluminum foam cores subjected to impact and quasi-static loading have been measured. The shallow sandwich arches comprise2A12-0aluminum alloy face sheets and aluminum foam cores.The dynamic response of end-clamped shallow sandwich arches has been measured by impacting the arches at mid-span with aluminum foam projectiles. Laser displacement transducer was used to measure the permanent transverse deflection of the back face mid-point of the arches. The resistance to impact loading is quantified by the permanent back face deflection and final core compressive strain at the mid-span of the arches. First, the deformation/failure modes of shallow sandwich arch were observed and classified systematically. Further, the structural response and deformation mechanism of clamped shallow sandwich arches subjected to projectile impact were analyzed. Finally, the effects of projectile impulse, face-sheet thickness, core thickness, and radius of curvature on the structural response were obtained.Based on the experiments, corresponding finite element simulations were conducted using LS-DYNA software, and the simulation results are reported and discussed in this paper. Finite element simulations of these experiments are in good agreement with the experimental measurements. The results indicated that permanent deflection of the back face can be efficiently controlled by increasing thickness of face sheets, thickness of core or appropriately increasing curvature. Meanwhile, shock resistance of the shallow sandwich arch can also be improved. A limited study of weight optimization is carried out. Dimensionless parameters governing optimal designs are identified. Specific results are presented for the best performance that can be achieved and the optimal distribution of thickness between face sheet and core. The numerical simulations were employed to determine the pressure versus time history exerted by the foam projectiles on the arches. It was found that the pressure transient was reasonably independent of the dynamic impedance of the arch, suggesting that the metal foam projectile is a convenient experimental tool for ranking the shock resistance of structures.The structural response and plastic collapse modes for clamped sandwich arches under quasi-static loading have been investigated experimentally and theoretically. The experimental results showed that plastic collapse displayed in three competing mechanisms:face yield, core shear and indentation. Simplified theoretical models and analytical formulae are developed for the elastic stiffness and initial collapse strength of sandwich arches.