Electrospun PAN / BN Nanofiber Interlayers for Enhanced Mode I Interlaminar Toughness and Multifunctionality in CF / EP Composites

ABSTRACT Carbon fiber/epoxy (CF/EP) composites are widely used in high‐performance structural applications, but insufficient interlaminar fracture toughness and limited multifunctional integration remain challenges for their broader application. In this work, boron nitride (BN) nanoparticles were incorporated into a polyacrylonitrile (PAN) solution to fabricate PAN/BN composite nanofibers, which were directly electrospun onto carbon‐fiber surfaces to construct a localized interfacial nanofiber layer. The resulting interphase combined a continuous PAN nanofiber framework with BN nanoparticles, providing additional fracture‐related energy dissipation and heterogeneous dielectric interfaces within the interlaminar region. With optimized BN loading, the modified composite exhibited enhanced Mode I interlaminar fracture toughness (G IC ), electromagnetic shielding, and modified thermal response. The optimized 10PAN/5BN‐CF/EP composite achieved a G IC of 706.8 ± 68.6 J m −2 , corresponding to a 38.1% increase compared with unmodified CF/EP. Its total electromagnetic shielding effectiveness reached 77.8 ± 5.1 dB, representing a 105.3% increase, while increased thermal diffusivity and a modified infrared thermal response were also observed. These results demonstrate that electrospun PAN/BN interfacial modification provides a localized strategy for simultaneously improving interlaminar fracture toughness and electromagnetic shielding while regulating the thermal response of CF/EP composites.