Abstract
Sandwich composites offer unique lightweight and high bending stiffness advantages for a wide variety of engineered structures. Traditional foam core sandwich constructions exhibit low transverse stiffness and catastrophic compression failure of the core, besides being inaccessible in terms of space. In this study, two configurations including a hollow truss/Z-pin core comprising a three-dimensional (3-D) open network of titanium pins and a foam core reinforced with a 3-D arrangement of titanium pins have been considered in conjunction with traditional foam core sandwich composites. These innovative core designs have the potential to enhance the impact damage resistance, and provide damage containment mechanisms and space/core accessibility advantages. The top and bottom facesheets in all three types of sandwich constructions are made from 16 layers of E-glass/epoxy prepregs stacked in crossly orientation. The low-velocity impact response of the composites is studied at five energy levels, ranging from 11 to 40 J, with an intention of investigating the damage initiation, damage propagation, and failure mechanisms. The influence of spacing the Z-pins in a foam core has also been studied at the same five energy levels. Detailed microscopic inspection has been conducted to determine the impact failure characteristics of the three types of sandwich composites. For the energy levels considered, the results demonstrate that by reinforcing the foam cells with Z-pins, low-velocity impact damage is contained effectively and is limited to the localized dimensions of the core and facesheet that lie within a pain cluster dimension.
