This study elucidated the synergistic improvement of the interfacial performance and impact resistance of carbon fiber-reinforced epoxy (CF/EP) composites by employing continuous electrochemical oxidation. CFs were electrochemically treated at different current densities, and the surface physicochemical properties, including the surface morphologies, chemical compositions, and wettabilities, were analyzed. After electrochemical oxidation, the IFSS of the CF/EP increased by 48.8%, significantly improving the impact resistance of the composites. The experimental results showed that, when the current density reached 0.15 mA/cm², the damage area after impact reduced by 61%. Concurrently, fiber fracture and resin failure became the primary energy-dissipation modes, maximizing the fiber reinforcement effect and enhancing the impact resistance. However, fiber fracture deteriorated the static mechanical properties of the composites. Subsequently, at a 0.10 mA/cm² current density, the CF/EP composites exhibited an increased compressive strength after an impact of 331 MPa.

The brittleness of bismaleimide (BMI) resin is a major issue that restricts its use as a matrix for advanced composites. Blending with thermoplastics constitutes an effective toughening approach that preserves the thermal resistance and mechanical properties of the resin. Reaction-induced phase separation is the primary toughening mechanism in thermoplastic-toughened BMI resin. However, the complex phase-separated structure causes the relationship between the glass transition temperature (T_g) and the curing degree to deviate from that described by the classical DiBenedetto equation. In this paper, two improved models, incorporating power-law correction and threshold inhibition, were constructed to address the phase-separation effect. An aerospace-grade BMI resin was toughened by a thermoplastic polyimide. The relationship between T_g and the curing degree was fitted by the DiBenedetto equation and the improved models. It was found that the adjusted coefficient of determination for the power-law correction and threshold inhibition models for the toughened resin increased to 0.978 and 0.995, respectively, whereas that of the DiBenedetto equation was only 0.612. This work provides a new, readily applicable empirical model for the prediction of T_g in thermoplastics-toughened thermosetting resins and offers theoretical support for optimizing the curing process and controlling the performance of multiphase resins.