Synchronous effects of multiscale reinforced and toughened CFRP composites by MWNTs-EP/PSF hybrid nanofibers with preferred orientation

MWNTs-EP/PSF (polysulfone) hybrid nanofibers with preferred orientation were directly electrospun onto carbon fiber/epoxy prepregs and interlaminar synchronously reinforced and toughened CFRP composites were successfully fabricated. With MWNTs-EP loading increasing, the oriented nanofibers were obtained accompanying with enhanced alignment of inner MWNTs-EP. Flexural properties and interlaminar shear strength of composites were improved with increasing MWNTs-EP loadings, whereas fracture toughness attained maximum at 10 wt% MWNTs-EP loading and then decreased. Based on these results, multiscale schematic modeling and mechanism schematic of hybrid nanofibers reinforced and toughened composites were suggested. Due to the preferred orientation of nanofibers, MWNTs-EP was inclined to align vertically to carbon fiber direction along the in-plane of interface layer. The proposed network structures, containing four correlative phases of MWNTs-EP/PSF sphere/carbon fiber/epoxy matrix, contributed to simultaneous improvement of strength and toughness of composites, which was realized by crack pinning, crack deflection, crack bridging and effective load transfer.