The heat-treatment process includes two basic stages: hardening of the initially liquid polymer-binder in the composition of the structure, and cooling of the already hard polymeric composite material. Researchers have focused their attention primarily on the stress--strain state of thick-wall articles in the cooling process (see, for example, [1-4]), since maximum tensile radial stresses develop and the monolithic character of the material is primarily disturbed in this stage of heat treatment, while these stresses are very small and relaxation processes are shortened in the hardening stage. As experimental data were accumulated, however, uncertainty arose concerning the effectiveness of this restricted approach, and studies on mechanical phenomena during the hardening of these ~rticles began to appear in scientific literature (see, for example, [5-9]). In our study, we attempt to demonstrate the need for conducting detailed investigations of the mechanical phenomena in the complex hardening process for the final solution of the above-described problem of maintaining monolithic character throughout production.