The study of issues related to the development of a scientifically substantiated method of obtaining hybrid polymer composites (containing more than one type of reinforcing continuous fiber) in order to improve the stiffness characteristics of the material is an urgent task of building materials science, allowing to expand the field of effective application of polymer composites for structural purposes. Wetting of reinforcing fibers with binders during the fabrication of composites largely determines the occurrence of adhesive bonding. In this study it is revealed that wettability correlates with energy characteristics of phases (reinforcing fibers and binder); dispersion parameters of free surface energy of carbon and glass fibers without oiling composition and apprette, parameters of free surface energy of fibers with oiling compositions and apprettes are determined; wetting of fibers by epoxy resins with determination of their surface tension, parameters of free surface energies at the boundary with air is studied; the question of the separation of fibers from air is investigated.