Impact damage resistance and tolerance of honeycomb core sandwich panels

The damage resistance and tolerance of flat [(0/45)(n)/core/(45/0)(n)] sandwich plates with honeycomb core subjected to low-velocity impacts using hemispherical steel impactors has been investigated experimentally. The effects of impactor diameter on the impact behavior, resulting impact damage states, and residual strength under in-plane compressive loading was of particular interest. The impact responses characterized in terms of peak impact force was observed to be dependent on the facesheet type, core thickness, and impactor size, but was found to be independent of the boundary support conditions. The smaller impactor produced damage states characterized by residual dent depths that were comparable to the core thickness, accompanied by visible facesheet fractures. The larger diameter impactor produced damage states with large core damage regions but with dent depths less than the facesheet thickness. Under in-plane compressive loading, depending on the impact damage state, contrasting failure mechanisms involving net-section fracture and buckling failure were observed. A reduction in compressive strength up to 60% of the undamaged strength has been observed.