Experimental and numerical investigations of low velocity impact on sandwich panels

Sandwich panels with honeycomb cores are used for aerospace frames where mass efficient structures are needed; however the structural integrity of these panels is reduced by low velocity impacts. Their behaviour on impact is investigated in this paper by means of refined numerical Finite Elements simulations. The sandwich panels considered are made of a Nomex™ honeycomb core and thin Al 2024-T3 aluminium alloy skins. A highly detailed FE model (micro mechanical level) has been built by using data obtained from flatwise compressive tests of honeycomb cores and a calibration of the constitutive law and ductile failure of aluminium skins. Numerical results are compared in terms of damage shapes and failure onset with an experimental campaign, carried out using a free-fall apparatus and a spherical steel impactor. The impact phenomena, including the failure of the skin, have been reproduced by means of numerical models with an elevated grade of similarity to a real impact scenario. Discussion and perspective are reported.