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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. [ABSTRACT FROM AUTHOR]

• Blast experiments were conducted to study the close-in blast effect and failure characteristics of honeycomb HSPs. • The blast performance of auxetic HSPs is compared with regular hexagonal HSPs. • Simulation is in good agreement with experiments and can describe the deformation and fracture damage. • The effect of the core type and unit-cell angle on the damage of HSPs is investigated. 3D-printed auxetic honeycomb sandwich panels (HSPs) have considerable potential for blast resistance enhancement. This study aims to bridge the gap with regard to the experimental data on the effect of 3D-printed auxetic hexagonal honeycomb cores on the blast response of HSPs. To this end, the blast resistance of HSPs developed using auxetic re-entrant and regular hexagonal honeycomb cores is investigated experimentally and numerically. First, six HSPs are tested under close-in blast loadings. The HSPs comprise Q345 steel top and bottom sheets as well as a honeycomb aluminum alloy core with two configurations (regular hexagonal and auxetic re-entrant). According to the results, the former configuration enhances the HSP blast resistance by not only decreasing the deformation of the HSPs but also improving their damage tolerance. In addition, the responses of the HSPs are numerically studied via finite element analysis. The numerical method using the finite element program LS-DYNA achieves reasonable accuracy. Finally, a parametric study is conducted to investigate the effects of the honeycomb type, cell angle, debonding effects, and core material on the blast resistance of the HSPs. The results demonstrate that employing auxetic hexagonal honeycomb core, smaller cell angle, and ductile core material can improve the blast resistance of HSPs. [ABSTRACT FROM AUTHOR]

Abstract: Finite element simulation is employed to analyse the behaviour of clamped sandwich panels comprising equal thicknesses mild steel plates sandwiching an aluminium honeycomb core when subject to blast loadings. Pressure-time histories representative of blast loadings are applied to the front plate of the sandwich panel. The FE model is verified using the experimental test results for uniform and localised blast loading in the presence of a honeycomb core and with only an air gap between the sandwich plates. It is observed that for the particular core material, the load transfer to the back plate of the panel depends on the load intensity, core thickness and flexibility of the sandwich panels. [Copyright &y& Elsevier]

Abstract: Two series of experiments are performed to investigate the dynamic response of various essential components of a class of sandwich structures, under high-rate inertial loads. One consists of dynamic inertia tests and the other involves dynamic impact tests. A split Hopkinson bar apparatus is modified and used for these experiments. First, the energy-absorbing characteristics of the plate material in a sandwich structure are investigated using novel dynamic inertia tests, paralleled by detailed finite-element simulations. The loading conditions in this case are similar to those in high-rate pressure loading situations, and hence more closely simulate potential blast effects on structures. Plates made of DH-36 naval structural steel are used in the dynamic inertia tests. The plates subjected to inertia loading show membrane deformation behavior, but as the deflection or thickness increases, the bending deformation near the clamped joint becomes significant. Second, the dynamic behavior of the core material in a sandwich structure is studied through dynamic impact (compression) tests, using high-speed photography. In addition, both the quasi-static and dynamic response of the material is quantified using hydraulic testing machines and the Hopkinson-bar techniques. Aluminum foam as a core material is used in these experiments. Aluminum foam is a lightweight material with excellent plastic energy absorbing characteristics. The experimental results show a localized deformation in the metal foam specimens, at suitably high impact velocities. The simulation results correlate well with the test results in the overall behavior of the metal foam specimens. With these two experimental methods, the dynamic behavior of sandwich structures under high-rate inertial loading conditions can be examined minimizing the need for direct pressure-induced impulse experiments. Each series of experiments is relatively simple and can be performed separately to study the complex behavior of sandwich panels in simple and well-controlled tests. The validity of separate performance test is shown by a finite element analysis with aluminum foam core sandwich specimen subjected to blast loading. [Copyright &y& Elsevier]