Deformation and Failure Modes of I-Core Sandwich Structures Subjected to Underwater Impulsive Loads

This article reports an experimental study carried out with the aim of quantifying performance and failure modes of sandwich structures when subjected to impulsive blast loading. In particular, performance enhancement with respect to solid panels of equal mass per unit area is assessed. Likewise, the optimal distribution of the mass per unit area in the design of sandwich structures is investigated by comparing the behavior of sandwich structures with various distributions of face sheets thickness. By employing a previously developed FSI experiment, the study confirmed that usage of sandwich structures is beneficial and that performance enhancements, in terms of maximum panel deflection, as high as 68% are possible. The study also confirms theoretical and computational analyses suggesting that use of soft cores maximizes the benefits. Another interesting aspect revealed by this work is that the level of enhancement is highly related to the applied normalized impulse. The same distribution of mass per unit area between face sheets resulted in different normalized maximum deflection. A better performance enhancement was achieved at lower impulses. Here again, failure modes and their sequence seem to be the directly related to this finding. The work here reported clearly reveals a number of important features in the study of lightweight structures and points out to the synergies between structure geometry, materials, manufacturing methods, and threat levels as manifested by the strength of the impulse. Further theoretical and computational studies accounting for experimentally observed failure modes and its interdependence with the fabrication methods is needed to achieve additional predictive capabilities.