Geometrical effects in the impact response of the aluminium honeycomb sandwich structures

Low-velocity impact tests have been conducted on sandwich beams and panels based on [0°, 90°] glass fibre-reinforced epoxy skins with an aluminium honeycomb core. The sandwich beams were placed on simple supports positioned at different separations to investigate the effect of target size on their impact response. Two thicknesses (13 and 26 mm) of honeycomb core were investigated. Following impact, damage within the beams was assessed by sectioning the samples and observing them under a low-power microscope. An energy-balance model was used to predict the maximum impact force for subsequent comparison with the experimental results. The energy-balance model was used to partition the energy absorbed during the impact event, giving an understanding of the energy absorption process. Finally, a limited number of tests have been conducted on square sandwich panels in order to investigate the effect of impact loading on their indentation behaviour. An examination of the cross-sections of impacted samples highlighted regions of core buckling and local plastic folding. At higher energies, damage in the form of localized fibre fracture was observed in the top skin close to the point of impact. The energy-balance model predicted the elastic response of the sandwich beams with reasonable success. The accuracy of the model decreased as damage became more extensive in the beams. It has been shown that the level of permanent indentation in both the beams and the square panels collapsed onto a single curve when the data are plotted against maximum impact force.