Bundle-scale analysis of improved interfacial strength in carbon fiber/epoxy composites via polyacrylonitrile nanofiber interleaving

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ESKİZEYBEK V., Danişman A. F.

Gumushane Universitesi Fen Bilimleri Dergisi, cilt.16, sa.4, ss.1129-1143, 2026 (Scopus, TRDizin)

Özet

Electrospun nanofiber interleaving has emerged as an effective strategy for enhancing the interlaminar performance of carbon fiber reinforced polymer (CFRP) composites. However, its influence on interfacial mechanical behavior at intermediate length scales remains insufficiently quantified. In this study, the effect of polyacrylonitrile (PAN) nanofiber interleaving on the transverse and shear-dominated interfacial response of carbon fiber reinforced epoxy composites is systematically investigated at the fiber-bundle scale. Transverse fiber bundle tensile tests and mesoscale Iosipescu (V-notched) tow shear tests were employed to directly probe load transfer, stiffness evolution, and damage progression mechanisms associated with nanofiber-modified interfaces. The incorporation of PAN nanofibers resulted in an 18% increase in transverse bundle tensile strength and a 13% increase in transverse elastic modulus, indicating improved stress transfer under normal separation of adjacent filaments. More strikingly, Iosipescu shear testing revealed a pronounced 74% enhancement in bundle-scale shear strength, while the corresponding chord modulus increased only marginally (6%). This disparity highlights the strong loading-mode dependence of the nanofiber reinforcement mechanism. Fractographic analysis confirmed a transition from interfacial-dominated brittle failure in neat bundles to energy-dissipative damage modes in nanofiber-interleaved systems, including nanofiber bridging, pull-out, crack deflection, and localized plastic deformation within a resin-rich interphase. These results demonstrate that PAN nanofiber interleaving primarily enhances damage resistance and frictional load transfer under shear-dominated loading rather than elastic stiffening. This work directly links transverse tensile and Iosipescu shear responses to the underlying bundle-scale deformation mechanisms. The results provide new experimental insight into the mesoscale role of nanofiber interleaves. They also establish Iosipescu tow testing as a powerful method for correlating interfacial structure with mechanical performance in nanostructured CFRP systems.