Ag/Fe 3 O 4 –PAN nanofiber interlayers in CFRP laminates: interfacial toughening and EMI attenuation after hydrothermal aging

Ag/Fe3O4-loaded polyacrylonitrile nanofiber interlayers were incorporated into carbon fiber-reinforced polymer (CFRP) laminates. Four nanofiber/epoxy architectures were screened, and the selected configuration achieved 10.09 dB total shielding effectiveness at 10 GHz, with an absorption shielding effectiveness of 8.38 dB and an effective absorption ratio of 85.46%. CFRP laminates were evaluated before and after immersion in distilled water at 70°C for 21 days. Interleaving reduced final moisture uptake by approximately 15%. Before aging, tensile strength, flexural strength, apparent interlaminar shear strength, and mean Mode-I propagation toughness increased by 26.5%, 28.5%, 32.9%, and 20.1%, respectively. After aging, these properties remained 33.6%, 35.7%, 42.5%, and 25.5% higher than in aged neat CFRP. However, the increases in mean Mode-I propagation toughness were not statistically significant within either conditioning state after Tukey adjustment. Fractography revealed crack deflection, fiber bridging, pull-out, and cohesive failure. Average shielding effectiveness over 8–12 GHz increased from 72.47 to 82.96 dB, with the interleaved laminate retaining 73.78 dB after aging. These findings show that the selected nanofiber-interleaved architecture improved interfacial damage resistance while maintaining enhanced EMI attenuation under the investigated hydrothermal exposure.