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The effect of ultraviolet irradiation, the physical nature and percentage of fine-grained fillers on the mechanical properties of composites has been studied. It has been found that the ultraviolet irradiation of epoxy compositions causes a decrease in the adhesive strength and an increase in the cohesive strength of protective coatings. This has been proved to be due to a change in the course of physicochemical processes at the filler/epoxy oligomer interface, owing to which external surface layers, which have a considerable extent and a high degree of cross-linking, are formed around fine particles in the matrix.Introduction. The latest achievements in polymeric materials science make it possible to create composite materials (CM) and protective coatings based on them with tailor-made set of performance characteristics [1]. The use of different methods for the modification of composites at the initial stage of their formation by external energy fields is of prime importance in this respect. The ultraviolet irradiation (UVI) of polymeric compositions, such as epoxy oligomers, shows promise, for it makes it possible to considerably improve the properties of CMs [2].At the present time, new methods for the activation of physicochemical processes, which are associated with the possibility of controlling CM structure formation by using ultraviolet irradiation, are intensively developing. For instance, UVI of epoxy compositions at initial stage of their formation (before the addition of hardener) shows promise both from a technological and from a practical standpoint. At the same time, it is important to choose the percentage and physical nature of fine-grained filler, which is also a condition for the creation of epoxy composites with improved performance characteristics. Hence establishing the regularities and studying the mechanism of the influence of UVI and the physical nature of fillers on CM structure formation processes and the mechanical properties of CMs are a topical problem of modern polymeric materials science.The aim of the work is to establish the main regularities of the influence of fillers of different physical nature and UVI on the mechanical properties of epoxy composite materials.Materials and Methods of Investigation. The object under investigation was polymeric composite materials based on ED-20 epoxydiane oligomer (GOST 10587-84), which is characterized by a high adhesive and cohesive strength, inconsiderable shrinkage and technological effectiveness of application to extensive surfaces of complex profile. To cross-link epoxy compositions, PEPA hardener (TU 6-05-241-202-78) is used. Powders of 20-40 mm fineness, which have a different chemical nature, are chosen as fillers. They include gas black (GB)

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