Dynamic perforation behavior of closed-cell aluminium foams and foam core sandwich panels with various shaped projectile tips

This paper investigates the shape effects of projectile tips on the perforation behavior of closed-cell aluminium foams and foam core sandwich panels under low velocity impact. The density and thickness of the selected foam were 0.5 g/cc and 21 mm, respectively. The thickness of the aluminium face sheets used in the sandwich panel was 1 mm. The impact perforation experiments were conducted using fifteen additively manufactured aluminium alloy projectile tips of various cone angles and geometrical shapes. The tests were carried out using an instrumented drop tower with an impact velocity of 6 ms^-1 (impact energy 105 J) for the foam panels and 10 ms^-1 (impact energy 274 J) for the foam core sandwich panels. The impact responses of the foams and foam core sandwich panels, such as perforation resistance force, perforation energy absorption, and failure modes for the studied projectile tips, were investigated. The results indicate that the projectile tip shape and angle have an influence on the impact responses of foams and foam core sandwich panels. The highest peak force and energy absorption enhancement are observed for the pencil and cone-type projectile, respectively, for changing the angles from 20° to 30°. An approximately three-fold rise in energy absorption is observed for the sandwich panels because of the additional force required to perforate the face sheets.