An analysis approach is presented to predict the low-speed impact response of sandwich pnels with different face-sheet thicknesses, honeycomb-core thicknesses, and core densities. In this approach, impact analysis of a plate on an elastic foundation is performed first to determien the contact force and surface strains on the impacted side of the sandwich panel. The contact force obtained from this analysis is used in a subsequent impact analysis of a sandwich panel modeled as a homogeneous plate to determine the out-of-plane displacement and surface strains on the side of the sandwich panel opposite to the impacted side. The contact force and strain results obtained using this method compare very well with experimental results. The experimental and analytical resutls obtained for the sandwich panels considered herein suggest that impact response for sandwich panels is a very local phenomenon where the panel boundary conditions and size do not significantly influence the response. The damage-initiation impact-energy levels for sandwich panels is determined to be mcu hlower than those for paltes with the same properties as the face sheets with similar edge conditions. The damage threhsold energy level and failure mode appear to be functions of the face-sheet thickness. This difference in damage-initiation levels is due to the local nature of sandwich panel response which precipitates shear and delamination failure modes. For higher impact-energy levels, the dominant failure modes are through-the-thickness shear failure, delaminations, face-sheet back-surface tension failure, extensive spallation, honeycomb core separation and crushing.
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