Low-velocity impact response of cross-ply laminated sandwich composites with hollow and foam-filled Z-pin reinforced core

Sandwich composites offer unique lightweight and high bending stiffness adv antages for a wide variety of engineered structures. Traditional foam core sandwich constructions exhibit low transverse stiffness and catastrophic co mpression failure of the core. besides being inaccessible in terms of space . In this study, two configurations including a hollow truss/Z-pin core com prising 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 considere d in conjunction with traditional foam core sandwich composites. These inno vative core designs have the potential to enhance the impact damage resista nce, and provide damage containment mechanisms and space/core accessibility advantages. The top and bottom facesheets in all three types of sandwich c onstructions are made from 16 layers of E-glass/epoxy prepregs stacked in c rossly orientation The low-velocity impact response of the composites is st udied at five energy levels, ranging from 11 to 40 J, with an intention of investigating the damage initiation, damage propagation, and failure mechan isms. The influence of spacing the Z-pins in a foam core has also been stud ied at the same five energy levels. Detailed microscopic inspection has bee n conducted to determine the impact failure characteristics of the three ty pes of sandwich composites. Fur the energy levels considered, the results d emonstrate that by reinforcing the foam cells with Z-pins, low-velocity imp act damage is contained effectively and is limited to the localized dimensi ons of the core and facesheet that lie within a pin cluster dimension.