An analytic model for the response to water blast of unsupported metallic sandwich panels

A prior assessment of the response of a metallic sandwich panels to water blast has identified soft and strong core responses and outlined the advantages of softness. Ensuing analysis has provided mechanism maps that distinguish these responses. The present article extends these assessments by developing an analytic model for the wet face response, inclusive of fluid/structure interaction, that can be used for a wide range of core topologies. The model addresses cavitation and incorporates the momentum of reconstituted water attached to the wet face. It assumes a transient dynamic strength of the core associated with dynamic buckling. The model includes coefficients that have been independently characterized using numerical simulations. The fidelity of the analytic model has also been assessed using simulations. The results reveal that analytic predictions of the wet face velocities are quite accurate for most of the soft cores examined. The implication is that the models may be used as reliable input to panel-level simulations for predicting such metrics as the reaction forces and the displacements. Discrepancies arise for strong cores with relatively large push back stress, and for systems with very thin wet faces, suggesting that embellishments are required for panels incorporating such features.