Composite encasement enables enhanced impact resistance in sandwich construction under low-velocity impact loading

The demand for civil/military equipment protection has driven innovations in sophisticated sandwich structures with superior impact resistance. However, incorporating multiple strengthening regimes into one structural configuration to achieve superior mechanical performance remains challenging. Herein, the concept of a sandwich with a periodical hybrid core component with composite encasement is proposed, examined, and explored, both experimentally and numerically. Such a sandwich construction employs a periodically arranged hybrid core as a discontinuous core assembly, enabling superior mechanical performance compared to its counterpart. The introduction of composite encasement alters the dominant structural damage patterns of the intact sandwich target, enhancing its impact resistance through (1) reinforcing the bare foam core part owing to spatial constraints, (2) expanding the affected region resulting from the overall outward bending deformation, and (3) separating the propagation of internal damage occurring in the core component. Furthermore, for this composite sandwich target, the presence of composite encasement endows a pronounced enhancement in structural integrity and energy absorption. In addition, such a sandwich construction would further enhance its impact resistance when the debonding properties of the interfaces between adjacent cores and facesheets are improved. These findings offer promise for the design and application of multiple mechanism-incorporated protective structures in unmanned civil/military vehicles that operate under extreme loading conditions.