Recycled polyacrylonitrile nanofiber interleaves with graphene nanoplatelets for adhesively bonded composite joints: lap-shear and opening-mode fracture performance

Official URL: https://dx.doi.org/10.1002/pc.71342

This study presents a sustainable toughening strategy for adhesively bonded CFRP joints by using electrospun polyacrylonitrile (PAN) nanofiber interleaves produced from virgin PAN (vPAN) and recycled PAN (rPAN) recovered from textile-waste Orlon. Graphene nanoplatelet (GNP)-hybridized vPAN and rPAN interleaves were also examined to clarify the combined effect of nanofiber bridging and GNP-assisted crack resistance. Single-lap joint tests showed that the lap-shear strength increased from 10.34 MPa for neat epoxy to 11.80 MPa for vPAN/Ep and 12.40 MPa for rPAN/Ep. The highest strength was obtained for GNP–rPAN/Ep, reaching 13.24 MPa, which corresponds to a 28.08% improvement over neat epoxy. Under Mode-I DCB loading, the crack-initiation load increased from 49.39 N for neat epoxy to 77.68 N for GNP–rPAN/Ep, while the critical fracture energy increased from 230.16 to 376.31 J/m2. Fracture surface observations indicated that nanofiber interleaving changed the damage response from a more interface-dominated appearance toward a more heterogeneous mixed-fracture character. SEM observations further supported the activation of nanofiber bridging, pull-out, crack-path deviation, and GNP-assisted pinning/deflection mechanisms. The results show that rPAN nanofiber interleaves have the potential to improve joint strength and fracture resistance and promote the use of circular materials in composite bonding applications.