Army Aircraft Protective Structures Program

Mathematical analyses of the physical properties of the various materials as well as experiments in which fragment simulating projectiles were used have yielded insight into the basic mechanics of fragment defeat. Materials were tested by impacting them with projectiles weighing between 17 and 300 grains at velocities ranging from 500 to 5,000/ft/sec. Data from these tests are presented to illustrate the relations between mass, velocity, and penetration depths of the projectiles into ballistic nylon, wood, sand, and clay. Three different failure modes that are dependent on the impact velocity of the projectile were identified for ballistic nylon. Test results showed that as the projectile impact velocity increased, a critical velocity was reached at which the nylon sheared immediately upon impact, offering little resistance to penetration. Test results also indicated that the relation between thickness and effectiveness of nylon was not linear.