High-performance sandwich panels with Inconel-718 cores for extreme blast loading

Novel sandwich structures are being developed to combat the ever-increasing threat of terrorist attacks and the onset of wars in several parts of the world. Traditional sandwich panels consist of a single, thin-shell hollow core layer sandwiched between two solid metal sheets, usually made of steel. However, scientists are now developing novel sandwich panels with superior blast-resistant capabilities, particularly for high-intensity blast applications. Therefore, in the present study, a three-stage circular core sandwich panel is developed numerically to provide blast protection against very high loads of 8–15 kg of TNT. The face-sheets of the panel are made of the traditional steel material, but the core layers are composed of Inconel-718, a nickel-based alloy that can retain its mechanical properties at elevated temperatures. The three core layers are separated by two intermediate sheets, also composed of steel. Numerical analysis is conducted by subjecting this novel sandwich structure to blast loads of 8, 10, 12, and 15 kg of TNT at a stand-off distance (SoD) of 135 mm. The study is carried out using a Finite Element solver, wherein the CONWEP blast simulation code is employed, by defining the mass of the explosive in terms of TNT equivalent and the SoD. The Johnson Cook (J-C) material model is used to accurately predict the ductile failure and plastic deformation behaviour of both metals. The data from the blast analysis is collected in the form of front and back face deflection of the panel, the pressure variation on the top surface of the panel, the internal and plastic dissipation energy stored in the panel, and the variation of kinetic energy across the three core layers. The findings from the recorded data show that the three-stage sandwich panel with Inconel-cores can adequately resist blast loads of up to 15 kg TNT, and the back face deflection of the panel at all loads between 8 to 15 kg is within 100 mm. Upon conducting energy analysis, it is observed that the cores exhibit minimal energy absorption due to their limited deformation, and no localised deformation is observed at the central blast impact zone. This is because the three-stage structure facilitates progressive energy dissipation, and the blast pressure is distributed across the three layers.