An analytic solution is obtained for the one-dimensional problem of normal penetration of an elongated projectile made from a rigid-plastic material into a similar monolithic barrier. By using a more precise penetration-resistance law and a staging principle and describing the nonsteady phases of penetration with semiempirical relationships, we find it possible to obtain good agreement between calculation and experiment with respect to crater depth at impact velocities from near zero to several km/sec. The method is used to analyze the impact toughness of laminated barriers made from two different materials with different physicomechanical characteristics. It is shown that substitution of a laminated barrier for the monolithic target can save weight only if the variation of the impact-toughness ratio of the two materials changes sign at a velocity lower than the velocity of impact loading of the barrier. A procedure for determination of the optimum composition of a laminated barrier made from a finite number of materials is described. An expression is obtained for calculation of the maximum weight advantage due to proper specification of the thiknesses and arrangement of the layers.