AGING AND FRACTURE OF COMPRESSIBLE ELASTIC-VISCOUS MEDIA
During the prolonged action of mechanical stresses and moderate temperatures the interrelated processes of deformation and damage in polymer materials are occured. These processes lead to destructive eﬀects and are accompanied by chemical reactions, which increase the structure changes and properties of the considered materials. Accordingly, it is possible to distinguish two types of fracture of polymeric materials during long-term mechanical and thermal eﬀects. The ﬁrst type (mechanical) is implemented in the condition of active loading, and in experiments on creep at moderate temperatures. The second type of fracture (chemical) is associated with the accumulation of structural damage in the long process of aging in the absence of external stress (static fatigue). The modiﬁed version of Maxwell’s equation and the equation for the damage parameter are formulated. The analytical solutions for the creep and stress relaxation are derived. Unlike Maxwell formula, the stress relaxation ratio has not zero asymptote. To describe the creep deformation and fracture of a compressible elastic-viscous medium the Boltzmann-Volterra equation is used. An analytical solution for the continuity parameter and the long-term strength criterion is received. The theoretical curves for the continuity parameter and the long-term strength criterion are plotted. Quantitative and for creep curves qualitative agreement with the corresponding experimental curves are observed. Refs 12. Figs 6.