This paper presents the results of investigation of the influence of oxidized, nanodispersed additive and carbon fibers on thermophysical properties and structure formation. It was proved that there is no mass loss in the temperature range of ∆Т = 293–568 K for all studied materials. This allowed us to establish the initial temperature of mass loss of composites (T0 = 568–573 K). It was found that the maximum value of the exoeffect (Tmax = 709 K) has a material containing oxidized nanodispersed additive (0.075 wt%) and carbon fibers (0.100 wt%). Due to this, it was possible to determine the end of destructive processes for the studied materials, which occurs in the temperature range of ∆T = 757.4–770.2 K. Thus, the inexpediency of using composites in a certain range was stated since the last stage of destruction of materials took place. The activation energy of thermal destruction of the epoxy–polyester matrix and composite materials developed on its basis has been experimentally established. In particular, it was found that the activation energy of the developed composite materials increases by two times compared to the epoxy–polyester matrix and reaches the maximum value (E = 127.0–129.4 kJ/mol) for composite materials No. 1 and No. 2. The regularities of the physical and chemical processes at structure formation were determined by the infrared (IR) spectra. The interaction between the two-component filler and the reactive groups of the binder, and the change in the local structure of such materials, were defined. Therefore, directed control of the processes of structure formation can be had by introducing a two-component bidispersed filler into the epoxy–polyester matrix. 2152-2057/22/$35.00 © 2022 by Begell House, Inc. www.begellhouse.com