Projectile-impact-induced fracture of liquid-filled, filament-reinforced plastic or aluminum tanks

Abstract : An experimental evaluation was made of the impact-fracture characteristics of liquid-filled tanks with walls of several filament-reinforced plastic materials. Comparisons were also made with tank walls made of an aluminum alloy. The materials evaluated were glass-filament- reinforced urethane or epoxy, Dacron-filament-reinforced urethane, steel-wire-reinforced urethane, and 2014-T6 aluminum alloy. The liquid contained in each tank was either water or liquid nitrogen. The impacting projectiles were 7/32-inch-diameter spheres of steel or aluminum, which were accelerated to velocities of 5500 and 6500 feet per second, respectively. The glass-reinforced plastics were most resistant to impact-fracture damage; the Dacron-reinforced urethane was least resistant. The glass-reinforced plastic walls were also more resistant to fracture than the aluminum alloy walls. Impacts into liquid-nitrogen-filled cylindrical tanks with approximately 1/32-inch-thick walls of these materials resulted in bursting of an aluminum wall stressed prior to impact to only 10 percent of the material ultimate strength, compared with only a puncture and local delamination of the outer filament layer of glass-reinforced epoxy walls stressed prior to impact to as high as 40 percent of the material ultimate strength.