An Experimental Investigation Of The Impact Resistance Of Double Sheet Structures At Velocities To 24000 Feet Per Second PDF Download

Small pyrex glass spheres were launched into aluminum double-sheet targets at velocities to 8.8 km/sec to determine the effects of total sheet thickness and sheet spacing upon penetration resistance. The ballistic limit of double-sheet structures consisting of two equally thick aluminum sheets was found to increase with increasing total sheet thickness and sheet spacing. In addition, for a particular ratio of total sheet thickness to projectile diameter, the effectiveness of sheet spacing increases with increasing impact velocity. This effect is attributed to melting and vaporization of the projectile and front-sheet material, and it is concluded that this trend will continue as material vaporization becomes more dominant. The data of this report are used to establish the effectiveness of total sheet thickness and a lower limit for the effectiveness of sheet spacing. It was determined that the structural ballistic limit varies with the 2.5 power of the ratio of the total sheet thickness to the projectile diameter and with at least the square of the ratio of the sheet spacing to the projectile diameter. The data indicate that for impacts at a given velocity the ratio of front- sheet thickness to projectile diameter that causes maximum vaporization or fragmentation or both will result in the most efficient meteor bumper. It is concluded that the double-sheet structure most efficient in resisting penetration will use that thickness for a front sheet and the remaining available mass in the rear sheet. Measurements were also made of the front-sheet hole diameter and the front-sheet mass loss. It was determined that the front-sheet hole diameter varies with the square root of the impact velocity and the 0.45 power of the front-sheet thickness and the front-sheet mass loss varies with impact velocity and the square of the front-sheet thickness.