Indentation failure behavior of honeycomb sandwich panels

The failure behavior of simply supported honeycomb sandwich panels subjected to indentation loading on the top skin has been studied. A plate-on-elastic-foundation approach based on distributed load and panel-specific considerations (finite thickness and transverse shear) is developed to analyze the panel stress distribution. Panels with various glass-fibre/epoxy skins and aramid cores are analyzed by using this approach together with the finite-element analysis. Surprisingly good agreement is found between the theoretical and FEA solutions, suggesting that the model satisfactorily describes the panel indentation behavior. Indentation-induced stresses in the core relevant to the onset of indentation failure are found to depend on skin bending stiffness, core stiffness and indenter size. The calculated maximum shear and normal stress values are compared with the experimental data to assess the core failure mechanisms involved. The comparisons clearly show that core shear failure dominates the onset of indentation failure.