RESUMEN
The explosion products, such as shock waves, fragments and heat energy formed by explosion, act on the plate structure, which may cause structural damage, material failure and even phase transformation of material. In this paper, the damage mechanism and protective effect of near-field blast load on sandwich structure based on foam-nickel core material were studied. Firstly, the near-field explosion test was conducted to investigate the blast response of the foam-nickel sandwich structure subjected to blast shock from 8701 explosive at near-field position. The deformation characteristics and stress history of the sandwich structure on the acting location of blast load were carefully investigated via experimental methods. A finite element model of near-field explosion was established for effective numerical modelling of the dynamic behaviour of the sandwich structure using the explicit dynamics software ANSYS/LS-DYNA for more comprehensive investigations of the blast shock response of the sandwich structure. The finite element model is reasonable and validated by mesh independence verification and comparing the simulated response behaviour to that from the experimental results for the sandwich structure subjected to near-field blast load. On this basis, the damage mechanism and protection effect of the near-field explosion impact on foam-nickel cores with different density and porosity are simulated more systematically. The investigated results from the experiments and a series of numerical simulations show the large deformation effect due to the extensive energy absorption, which suggests that the sandwich structure based on foam-nickel core material may be expected to become a new choice of protective structure under near-field blast load.
RESUMEN
Due to the unique "Brick-and-Mortar" structure, nacre exhibits extraordinary mechanical properties such as high strength and toughness, which are naturally exclusive in traditional engineering materials. The main threat to the shell is the impact load along the direction perpendicular to the lamellar structure. However, how it attenuates stress wave and dissipates kinetic energy during impact events remains unclear, especially along different loading directions (the directions perpendicular and parallel to the lamellar structure). In this paper, damping performance of nacreous bio-inspired composites is investigated to evaluate the energy dissipation from the perspective of dynamic modulus using theoretical and numerical methods. It is found that the stress states and Poisson's ratio of the "mortar" exert remarkable influence on composites' loss modulus. Moreover, the predicted optimal aspect ratio in this work is consistent with the previously reported experimental observation. Additionally, by introducing interlocked structure, the composites show strong direction-dependent damping behaviors, and the enhanced loss modulus is observed both in longitudinal and normal direction. The findings are not only expected to achieve a deep understanding of the dynamic energy dissipation mechanism of nacre, but also to provide a guideline for design of bio-inspired composites responding to shock loads.