It is known that high-performance composite materials and composite-fibrous materials reveal excellent physical-mechanical properties but display one fault, namely, low crack resistance when stresses act in the direction transversal to fibers. This fault is frequently the reason for composite walls of high-pressure shells lose their tightness and as a result these walls may be penetrated by transported and stored mediums. We present a model for the process of crack generation for glass-reinforced plastic walls and propose a procedure for determination of parameters of penetrability of this material.