Response of aluminium honeycomb sandwich panels subjected to foam projectile impact – An experimental study

Abstract

Aluminium honeycomb sandwich panels have potential applications as a protective mechanism that can be used to prevent failure of an important structure subjected to impact loading. Therefore it is important to fully understand the resistance of the sandwich panels subjected to impact loading conditions. The main objective of this work was to study the resistance of sandwich panels with different aluminium honeycomb cores, air sandwich panels (no core between the two face sheets) and monolithic plates of equivalent mass subjected to impact from foam projectiles. The deformation and the elastic spring-back of the honeycomb sandwich panels and the monolithic plates have been compared and discussed. The resistance of the panels and plates has been quantified by their back-face deflection with respect to the projectile impulse. Five different types of aluminium honeycombs have been used as the core material. The front-face sheet and the back-face sheet of the honeycomb sandwich panels are made of aluminium plate with 1 mm thickness. Cylindrical ALPORAS aluminium foams with a relative density between 9% and 11% are employed as the metal foam projectiles. They are fired at several hundred metres per second towards the centre of the panels and plates using a gas gun. The deflection histories of the back-face have been measured using a laser displacement sensor. From the deflection histories, the maximum deflection and the final deflection of the back-face can be distinguished. Deformation modes and failure modes of the individual component have been observed and classified into several categories. Moreover, the deflections of the honeycomb sandwich panels have been compared with deflections from air sandwich panels. It is found that the honeycomb sandwich panels outperform both the air sandwich panels and the monolithic plates within an impulse range of 2.25 kNsm−2 ～ 4.70 kNsm−2. Outside this operational range, the advantages associated with employing the honeycomb sandwich panels as a protective structure upon impact of foam projectiles diminishes.