PERFORATION OF CELLULAR SANDWICH PLATES

An experimental investigation has been conducted to study the perforat ion characteristics in the axial direction of cellular sandwich plates , as well as of its individual components. The covers encompassed an a luminum alloy and acrylonitrile-betadyne styrene (ABS), while the core s consisted of honeycombs or flexible sheets of aluminum (Flexcore), w ith a total sample thickness of 19.1 or 15.9 mm. Hard-steel strikers o f two sizes - of spherical, cylindro-conical or cylindrical shape - we re fired orthogonally against the simply-supported targets. Initial ve locities ranged from just below the ballistic limit to speeds well abo ve this value, involving a span of 17-380 m/s for all targets. Perfora tion of the honeycomb sheets required higher velocities and produced d ifferent damage patterns than in the cellular samples with curved wall s, due to different flexibility of individual cells. However, the ball istic limit of the sandwich was not significantly affected by the type , cell size or wall diameter of the composite, as the principal mechan ism resisting perforation of the composite was piercing the facing pla tes. Thus, identical covers produced the same ballistic limit regardle ss of core type. The curve of terminal versus initial velocity was con cave downward close to the ballistic limit and linear beyond, as obser ved frequently in other perforation cases. Cross sections of composite targets exhibited evidence of some interaction between covers and cor e 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.