Metallic sandwich panels subjected to high-intensity air-blast: Real-gas effects in modeling fluid-structure-interaction

Abstract

This paper investigates the influence of real-gas effects in fluid-structure-interaction while estimating high-intensity air-blast loads and its subsequent implications on the crushing of metallic sandwich panels. It is well known that at high pressure and temperature, nitrogen and oxygen molecules present in the air undergoes ionization and dissociation, which may, in turn, lead to higher stagnation pressure upon reflection from a wall. However, almost all fluid-structure-interaction models use the ideal-gas assumption even at very high pressure and temperature in estimating air-blast loads to simulate core compression of sandwich panels. In the present work, a new method is proposed to predict air-blast loads on free-standing metallic sandwich panels considering electronic excitation, ionization, and dissociation of the constituents in the air during fluid-structure-interaction. One-dimensional dynamic response of free-standing sandwich panels due to air-blast loads, which is computed based on the proposed method, is investigated and compared with other existing theories based on ideal-gas. The interaction of the panel with the fluid beyond, i.e., air-backed and water-backed conditions, is also studied. Real-gas effects in the air at the backside are also investigated and compared with the ideal-gas based backing condition. The study reveals that using ideal-gas based fluid-structure-interaction models in predicting high-intensity air-blast loads on sandwich panels leads to an under-prediction in core compression and plastic dissipation for the same "crushing strength to incident over-pressure ratio."Therefore, ignoring real-gas effects in the fluid-structure-interaction phase while designing the low-density core of a sandwich panel for high-intensity air-blast mitigation can be detrimental and may lead to catastrophic failure.