*2.3.3 Production of electrically functional self-healing epoxy composites*

Various strategies have been extensively explored to address the issue of inadequate electrical conductivity in epoxy composites. One commonly employed approach involves blending conductive single or hybrid fillers to utilize synergistic effects between epoxy polymers and various filler dimensions. For instance, Bian and his colleagues [53] introduced a remarkable self-healing epoxy composite capable of inhibiting electrical tree growth. They achieved this by incorporating SiO2 particles into the epoxy matrix and creating hydrogen bonds between the SiO2 particles and

epoxy chains through solution blending. The results demonstrated excellent selfhealing properties, with cracks healing upon the application of heat, and effective inhibition of electrical tree growth, a common cause of electrical breakdown in high-voltage applications.

Another approach, vacuum-assisted filtration, uses hierarchical filler architecture to prepare epoxy polymer composite films [54]. However, the time-consuming nature of this method has limited its practical application. On the other hand, the electrospinning coating method, known as the core-shell structure, provides a promising and simple means to create ordered composites [55–58]. Chen et al. [59] reported tough and rapidly self-healing carbon/epoxy composites using electrospun thermoplastic polyamide nanofiber (PAnf). The PAnf not only toughens the composite interlayer but also provides excellent self-healing capabilities. With just 1.2 wt% addition, the interlaminar shear strength and bending properties of composites increased by 17.6% and 14.7%, respectively. The entangled nanofiber structure enhances interlaminar adhesion, effectively suppressing microcrack and delamination propagation. The epoxy composites with PAnf demonstrated the best mechanical properties and healing efficiency after 3 h of electrospinning. Multiple healing cycles showed healing efficiencies of 70.1% for the third time. The inherent characteristic of thermoplastic PAnf allows it to repeatedly and steadily heal interlaminar fractures without depletion. The uniform distribution of porous PAnf promotes resin flow and impregnation without compromising the storage modulus and *T*g of the composites, preserving their original properties.

Additionally, a novel approach involves generating a 3D highly electrically conductive network by dispersing the epoxy polymer matrix, ensuring high electrical conductivity [60]. However, complex template preparation and polymer filling have hindered its widespread use. Magnetic field forces have also been used to promote filler orientation or construct electrical conduction networks [61]. Additionally, hot pressing is sometimes employed after processes like filtration, electrospinning, or template methods to reinforce the structure [62]. This innovative technique holds promise for advancing electrical conductivity in epoxy composites.
