Experimental characterization of low velocity impact energy dissipation in sandwich composites with porous cores with tailored structure and morphology

The impact performance of several porous polymeric and metallic foam core sandwich composite systems were evaluated for their suitability for protecting vehicle occupants in the event of a low velocity impact. The material systems evaluated were glass/phenolic face sheets reinforced with Nomax honeycomb core, cross-ply carbon-fiber face sheets reinforced with aluminum honeycomb cores of different cell sizes, and aluminum metallic foam cores of different cell sizes. Lastly, an exploratory study using an extrusion type 3D-printed polystyrene foam structure that customized pore size, pore distribution were undertaken. The peak load and energy dissipation of the composite materials were experimentally measured. An instrumented large semispherical impactor (48 mm diameter) applied loads at constant strain rate on the order of 0.1 m/sec to a 50 mm x 50 mm coupon sized composite specimen with varying thicknesses. The impact damage to materials were also visually examined. The current material system used for some interior components (glass/phenolic face sheets reinforced with Nomax honeycomb core) reaches a maximum load in a small time duration and displacement, causing catastrophic local crushing and delamination events. It is expected that the failure can be spread out with these alternative material systems with varying pore size distribution so that the energy dissipation can be accomplished with a lower peak force to improve occupant safety.