Keyword: «strength gradients»

The reasons for the formation of gradients of mechanical parameters of polymer composite materials (PCM) during exposure to natural climatic conditions are considered. It is shown that in the process of thermal and moisture cycling, cyclic internal stresses are formed in materials, the amplitude of which increases in the surface layers. Under the action of internal stresses activated by the ultraviolet component of solar radiation, microcracks are formed. The density of microcracks is maximum in the surface layers, which explains the mechanisms of uneven aging of PCM.