Abstract <p>This study investigates the influence of carbon nanotubes (CNTs) and silicon carbide (SiC) powder on the structural and mechanical properties of an epoxy-anhydride binder. The primary objective was to elucidate the modification mechanisms of the polymer matrix upon filler incorporation and evaluate their impact on the material’s thermoelastic characteristics. A key challenge involved establishing correlations between filler-induced structural changes and the composit’s viscoelastic behavior. X-ray diffraction analysis revealed that SiC addition reduces the intensity of the first diffusion peak by 23% with concomitant peak broadening, indicating decreased atomic clustering. Conversely, CNT incorporation increased the <i>z</i>₁/<i>z</i>₂ ratio by 15%, accompanied by expansion of the most probable interatomic distances (<i>r</i>₁) to 2.8 Å. Dynamic mechanical analysis demonstrated that SiC enhances the elastic modulus by 20.8% at 0.75 wt % concentration through formation of additional crosslinking nodes and cluster interactions, while maintaining property stability within the 40–115°C range. Both fillers extended the relaxation temperature interval by 5–7°C, improving damping capacity through the creation of “friction centers,” as evidenced by 18% increases in tan δ peak heights with unchanged peak widths. Radial distribution functions revealed distinct structural modifications: SiC reduced <i>r</i>₁ to 2.1 Å, indicating denser packing and lower curing energy, while CNTs produced a less dense structure with higher activation energy. These findings demonstrate that filler modification of the epoxy matrix not only alters rheological properties but also induces nanoscale phase transitions, enabling rational design of composites with desired thermomechanical performance.</p>