The performance characteristics of composite materials reinforced with polyacrylonitrile technical flagellum (PAN-TF), which has the reactivity of functional groups, can be improved by modifying it. The aim of the work was to study the effect of polyacrylonitrile fibrous materials, applied with AGM-9, A-187, A-174 and Duron OS 3151 modifiers, on the kinetics of the ED-20 epoxy resin curing process, structural features of the developed composites and their operational properties. The methods of kinetic research, differential scanning calorimetry (DSC), scanning electron microscopy and mechanical testing of composite materials were used in the work. The effect of modified PAN-TF on the change in the kinetics of the curing process of the epoxy binder is shown, characterized by an increase in the curing time, a decrease in the maximum curing temperature and a decrease in the activation energy of the curing ED-20. The results of kinetic studies are confirmed by the data of DSC epoxy compositions based on modified PAN-TF, which show a decrease in the maximum temperature and an increase in the thermal effects of the ED-20 curing process in the presence of the studied reinforcing systems compared with epoxy composite reinforced with unmodified flagellum. The structure formation of epoxy compositions under milder conditions ensures the formation of a contact zone between the elementary fibers and the binder, which contributes to an increase in the solidity of plastics compared to a composite based on the original PAN-TF. A comparative analysis of the strength properties of the studied composites showed that when applied to ED-20, there is an improvement in strength indicators. The assessment of kinetic parameters, structural features and strength properties of the developed composites reinforced with modified PAN-TF indicates an increase in the surface activity of fibrous materials as a result of their modification.