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Rods of basalt plastic armature (BPA) of a periodic profile with diameters of 6, 8, 10, 16 and 20 mm on the basis of an epoxy matrix were exposed for 30 months on open stands in a moderately warm marine climate of Gelendzhik and 28 months on similar stands in an extremely cold climate of Yakutsk. For initial and exposed BPA samples, changes of mechanical parameters were determined. After the exposure in Yakutsk, an increase of ultimate compression strength by 4–12% is found, depending on the diameter of rods. After the exposure in Gelendzhik, this indicator decreases by 10–17%. Using methods of thermomechanical analysis and dynamic mechanical analysis, linear thermal expansion coefficient and glass transition temperature of epoxy matrix were measured. In an initial state, a transition from a glassy state to a highly elastic one is discovered: an α1-transition at 118 °C and an α2-transition at 149 °C. After climatic action, there were detected a shift of α1-transition to low temperatures and a shift of α2-transition to higher temperatures. Reasons for the change of temperatures of transitions are weakening of a molecular layer and post-curing of the epoxy matrix in a surface layer. These effects are accompanied by an increase of the linear thermal expansion coefficient, moisture diffusion coefficient and maximum moisture saturation after the climatic action on BPA. Fractographic studies discovered presence of pores in a structure of BPA with sizes up to 10–20 μm, a quantity and size of which increase by 20–40% after the climatic action. In general, the studied BPA has high climatic stability and can be used for a long time under the extreme climatic conditions.

The formation of internal stresses in polymer composite materials (PCMs) caused by different elastic moduli and thermal expansion coefficients of polymer resin and reinforcing fibers, as well as by swelling due to the moisture uptake is discussed. The influence of thermal cycles on the internal stresses and strength of the materials was studied in dry and wet atmospheres. It shown that thermal cycles cause a periodic jumps in the stresses at lowfrequency mechanical loadings, during which the mechanical properties are degraded due to the formation of microscopic cracks in the polymer matrix. The relative changes in the strength, elastic modulus, glass-transition temperatures, moisture diffusion coefficient, and other PCM physical characteristics are proportional to the logarithm of the number of cycles and also depend on the form and size of specimens, amplitude, conditions, and length of thermal cycles. A prolonged action of external actions relaxes the internal stresses and reduces their influence on the aging of PCMs.

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