Construction of micro–nanostructure for interlayer reinforcement and toughening of carbon fiber/poly(phthalazinone ether sulfone ketone) with coaxially spun polyimide/polyvinylpyrrolidone–carbon nanotube core–shell fibers after stepwise etching

Carbon fiber-reinforced high-performance thermoplastic polymer (CFRHPTP) composites are highly susceptible to interlaminar damage when are subjected to external damage, which affects their mechanical properties and structural integrity. In this study, a core–shell electrospun fiber with partially exposed carbon nanotubes (CNTs) on the shell layer was prepared by coaxial electrostatic spinning of polyimide/polyvinylpyrrolidone (PI/PVP) core–shell fiber veils containing CNTs, and then was gradually etched until the CNTs embedded in the shell layer of the fibers were as gradually exposed. The introduction of core–shell veils with micro–nanostructures into the interlayers of carbon fiber-reinforced poly(phthalazinone ether sulfone ketone) (CF/PPESK) composites enhanced their interlayer and in-plane properties. The initial and propagation values of the composite’s mode I interlaminar fracture toughness were increased to 1182 J/m 2 and 1266 J/m 2 (46 % and 39 % increases, respectively), and the mode II interlaminar fracture toughness was improved to 2091 J/m 2 (113 % increase) after the introduction of electrospun veils into the interlayers. In addition, the tensile strength, flexural strength, and interlaminar shear strength of the CF/PPESK composites were enhanced by 17 %, 20 %, and 18 %, respectively. Molecular dynamics simulations elucidated the positive effect of PVP for an enhanced interface between the spun fiber and resin. Simultaneous increases in toughness and strength of the CF/PPESK composites were achieved. This study provides new ideas and methods for synergistic reinforcement and toughening of CFRHPTP composites through interlayer design of high-performance composites.