Instrumented Impact Testing of Composite Sandwich Panels

The impact response of various composite sandwich panels has been investigated. These composite sandwich panels, consisting of various fabric facesheet materials and different densities of poly(vinyl chloride) (PVC) foam cores, demonstrate exceptional low-energy impact resistance. The macroscopic failure modes, microfailure mechanisms, and energy absorbing characteristics of these composite sandwich panels were studied by using in strumented impact test, light microscopy, and scanning electron microscopy. The impact resistance of composite sandwich panels was found to be mainly controlled by the facesheets and relatively independent of the density of the PVC foam core, provided the facesheet material is tough enough The impact failure mechanism of sandwich panels containing less tough facesheets was found to change from facesheet-dominated to foam- core-dominated behavior, when the PVC foam core increased from low density to relatively high density. The energy absorbed by a sandwich panel made of low-density foam core was about 15%-100% greater than the sum of the energies absorbed by its separate constituents This result indicates that the impact energy of a composite sandwich panel cannot be predicted by the rule-of-mixtures law. This percentage deviation increased as the density of the foam core increased.