Temperature‐Activated Interlaminar Fracture Toughness and Mechanical Enhancement of CFRP Using Electro‐Spun PVDF / MWCNT Nano‐Veils

Carbon fiber reinforced plastics (CFRPs) are widely used in high‐performance structures but suffer from brittleness and low interlaminar fracture toughness. While thermoplastic nanofibrous veils have been used for interlayer toughening, the interfacial mechanisms beyond physical crack‐bridging remain unclear. This study presents a temperature‐activated toughening strategy by interleaving electrospun poly(vinylidene fluoride)/multi‐walled carbon nanotube (PVDF/MWCNT) nanofiber veils into CFRP laminates. By controlling the compression molding temperature relative to the PVDF melting point, we demonstrate that the nano‐veils enhance toughness through both mechanical and chemical mechanisms. Above the melting temperature, PVDF interacts more effectively with the epoxy matrix, and complementary spectroscopic (FT‐IR, XPS, Raman) and thermal (DSC) analyses provide converging, indirect evidence for a temperature‐activated interfacial interaction between PVDF and epoxy, for which a four‐step reaction mechanism is proposed as a testable hypothesis. Consequently, the modified CFRPs show up to an 85% increase in interlaminar fracture toughness compared to pristine samples. Additional improvements include increases of 12% and 31% in flexural strength (longitudinal and transverse, respectively) and a 14% rise in interlaminar shear strength. These enhancements result from synergistic effects of CNT‐induced β ‐phase formation, the proposed PVDF–epoxy interfacial interaction, and sustained crack‐bridging. This work demonstrates that thermoplastic nano‐veils can be chemically activated during processing, offering a promising approach for designing high‐toughness CFRP laminates.