Built-in intercalated hybrid PI/PPy nanofiber networks enabling optimizing interlaminar and electromagnetic shielding properties for CFRP composites

Developing advanced carbon fiber reinforced polymer (CFRP) with structure–function integrated characteristics holds considerable significance in the aerospace and military industries. Herein, electrospun polymide (PI) nanofibrous veils loaded with conductive polypyrrole (PPy) were incorporated into the interlayer of CFRP to simultaneously enhance the interlaminar properties, through-thickness electrical conductivity and electromagnetic interference shielding (EMI) properties. Experimental results demonstrate a remarkable 179.58 % increase in mode Ⅱ interlaminar fracture toughness compared to the plain specimen. Detailed analysis reveals the enhancement is driven by multiple toughening mechanisms, including matrix plastic deformation and cracking, nanofibers stretching and breakage, matrix-fiber debonding, as well as cracks deflecting and cross-layer migration. Importantly, incorporating these hybrid nanofibrous networks doesn’t compromise the overall mechanical integrity of CFRP, instead it results in a 30 % improvement in interlaminar shear strength over the baseline composites. Furthermore, the unique alternating sandwich lay-up structure, combined with the excellent electromagnetic wave attenuation properties of the nanofibrous veils, leads to a 1406 % increase in through-thickness electrical conductivity and a 211.68 % enhancement in EMI effectiveness compared to unmodified CFRP laminates. This study not only underscores the potential of hybrid nanofibrous veils in multifunctional composite design but also provides an efficient strategy for developing high-performance CFRP tailored for demanding applications.