Perforation of cellular sandwich plates

An experimental investigation has been conducted to study the perforation characteristics in the axial direction of cellular sandwich plates, as well as of its individual components. The covers encompassed an aluminum alloy and acrylonitrile-betadyne styrene (ABS), while the cores consisted of honeycombs or flexible sheets of aluminum (Flexcore), with a total sample thickness of 19.1 or 15.9 mm. Hard-steel strikers of two sizes - of spherical, cylindro-conical or cylindrical shape - were fired orthogonally against the simply-supported targets. Initial velocities ranged from just below the ballistic limit to speeds well above this value, involving a span of 17-380 m/s for all targets. Perforation of the honeycomb sheets required higher velocities and produced different damage patterns than in the cellular samples with curved walls, due to different flexibility of individual cells. However, the ballistic limit of the sandwich was not significantly affected by the type, cell size or wall diameter of the composite, as the principal mechanism resisting perforation of the composite was piercing the facing plates. Thus, identical covers produced the same ballistic limit regardless of core type. The curve of terminal versus initial velocity was concave downward close to the ballistic limit and linear beyond, as observed frequently in other perforation cases. Cross sections of composite targets exhibited evidence of some interaction between covers and core that indicates a ballistic limit somewhat different than what would be computed from the values of the separate components on the basis of an energy balance. (C) 1997 Elsevier Science Ltd.