Mechanical responses of a composite sandwich structure with Nomex honeycomb core

Weights of honeycomb sandwich composite structures are strictly controlled in scenarios such as in contexts of aerospace engineering. However, such structures extensively studied in past investigations were partly or completely made of aluminum or other metallic materials. Sufficient research has not been reported for honeycomb sandwich composites made of lightweight non-metallic materials. This paper presents an investigation into the mechanical responses of the Nomex honeycomb sandwich structure in a three-point bending test. The mathematical relationship between the shear stress distribution in the skin and that in the Nomex honeycomb core under the bending load was deduced. By applying the commercial software ABAQUS/Explicit, numerical simulations were performed with a highly detailed finite element model (micromechanical level) and equivalent elastic parameters. By comparing the experimental and numerical results, the validity of the theoretical derivation was verified. The effects of the thickness of the skin and the direction of the core on the mechanical responses of the honeycomb sandwich structure were studied. The results showed two different failure patterns of the honeycomb sandwich structure in the three-point bending test, which has rarely been reported previously. The improving effect of the increase in the skin thickness on the ultimate bearing capacity was more remarkable when the honeycomb core had a higher shear rigidity. For the same core direction, the honeycomb sandwich structure with the thicker skin had a better crashworthiness. The skin shear force distribution coefficient decreased exponentially with the ratio of core height-to-skin thickness