Synergetic Improvement of Interlaminar Fracture Toughness in Carbon Fiber/Epoxy Composites Interleaved with PES/PEK-C Hybrid Nanofiber Veils

Abstract

In this study, two types of soluble thermoplastic resins were added to epoxy resin at a fixed weight ratio to prepare a three-phase cast body. The cast was then manufactured into hybrid nanofiber as interleaves for interlaminar toughening of carbon fiber/epoxy resin (CF/EP) composites using a co-solvent method. The results revealed that when the hybrid components reached 15 wt%, Polyethersulfone (PES) and polyaryletherketone cardo (PEK-C) exhibited the best synergistic toughening effect, and the fracture toughness increased by 99.8% and 39.8%, respectively, compared with the reference or the same proportion of the single PES toughened sample. We used PES/PEK-C hybrid nanofibers with an areal density of 19.2 g per square meter (gsm) as composite toughening layers. Apart from the lack of significant influence of PES nanofiber on CF/EP composites, the interlaminar fracture toughness of mode I and mode II layers increased by 88.3% and 46.9%, respectively, compared to the reference sample. Scanning Electron Microscopy of the fracture surface and cross-section micromorphology of the laminate displayed that the thermoplastic microspheres of different sizes contribute differently to crack resistance: PEK-C consumes more energy due to the debonding and extraction of microspheres and resin, whereas the presence of the PES phase can induce more plastic deformation and crack deflection.

Funding

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University(KF2121); Science and Technology Department of Henan Province(212102210550); China National Textile and Apparel Council(2020061)