An interlayer flame retardant method to effectively fire retardant and reinforce CF/EP composites by nanofiber film intercalation

As an advanced material with wide application, carbon fiber reinforced epoxy resin matrix composites (CF/EP) are flammable, but the traditional flame retardant methods negatively affect its molding process, heat resistance, mechanical properties, and how to solve this problem has been a challenge. This paper adopts a novel flame retardant method of inserting nanofiber films of flame retardant into the interlayer of the composite laminate to achieve fire resistance, higher strength, and toughness of the composite. In this work, pentaerythritol phosphate (PEPA) nanofiber films with phenoxy resin (PKHH) as a carrier was prepared by electrospinning and placed between the layers of CF/EP laminates. The results show that a dense charring layer with isolation and protection functions can be formed between the layers of the CF/EP intercalated by the nanofiber films during combustion. Accordingly, the nanofiber film containing 50 wt% PEPA with the thickness of only 30 μm increased the LOI value of CF/EP from 27.8% to 34.7%, while reducing the THR and pSD by 14% and 27.2% respectively. What’s more, due to the Ex-situ toughening effect of the nanofibers, the flexural strength, interlaminar shear strength, and compression strength after the impact of the modified CF/EP were increased by a maximum of 11.2%, 11.3%, and 12.2% compared to unmodified CF/EP. This work proves the feasibility of interlayer flame retardant fiber reinforced resin composites, and provides a new method to prepare high-performance flame-retardant composites.