<p>The article presents the results of the evaluation of the kinetics of changes in the main mechanical characteristics of a polymeric epoxy composite with different fillers under the influence of different types of aggressive media. To form the polymer composite, an epoxy diane oligomer of ED-20 grade was used as the main (matrix) component, into which a hardener – polyethylene polyamine PEPA, a modifier – d-ascorbic acid C6H8O6 and fillers were additionally introduced: microdispersed, obtained by electrodischarge dispersion from a mixture of powders of 87.5 Al+12.5 Cu (wt.%), and fibrous – from polymeric discrete fibers. The influence of polymer modification and corresponding fillers on the material properties was evaluated by varying the component composition of the epoxy composite. According to the results of the study, it was found that the highest chemical resistance and level of mechanical properties after exposure to aggressive environments are characterized by the composite reinforced with a complex filler, including both a highly dispersed powder component and discrete polymer fibers. It was found that the oil environment was more aggressive in terms of loss of mechanical properties compared to seawater. A two-stage change in the level of mechanical characteristics of composites with the time of exposure to aggressive environments was established and a mechanistic model of the mechanism of increasing the chemical resistance of polymer composites by using a filler was proposed, based on the hypothesis that the crack propagation trajectory in the adhesive volume increases due to the presence of dispersed filler and discrete fibers.</p>