Debonding and impact tolerant sandwich panel with hybrid foam core

A major problem of sandwich panels is the debonding at or near the core/face sheet interface, especially under impact loading, which can lead to sudden loss of structural integrity and causes catastrophic consequences. The objective of this study is to develop and characterize new sandwich panels which are based on hybrid cores consisting of metallic millitubes and polymer matrix. To this end, two types of new hybrid cores were proposed. One consisted of polymer resin reinforced by vertically (transversely) aligned continuous metallic millitubes, denoted as Type-I sandwich panel. The other was made of polymer resin reinforced by horizontally (longitudinally) aligned continuous metallic millitubes, denoted as Type-II sandwich panel. Additionally, traditional sandwich panels with syntactic foam core were also prepared for comparison. Quasi-static compression and bending tests, low velocity impact test, and ballistic impact test demonstrated that the interface debondings and the subsequent shear failure in the core could be largely excluded from the Type-II panel. Meanwhile, a significant transition to ductile failure mode was observed in Type-II sandwich panel with dramatically enhanced load carrying capacity and impact energy dissipation. The results indicated that Type-II panel may be considered as an alternative for sandwich structures requiring debonding and impact tolerance.