Three‐roll milling exfoliated graphite nanoplatelets enhanced epoxy resin matrix–octahedral spinel modified carbon fiber composites: Preparation, microstructure, and mechanical properties

Abstract This study aims to enhance the mechanical properties of epoxy resin (EP)‐based carbon fiber (CF) composites. Graphite nanoplatelets (GNPs) obtained from the exfoliation of expanded graphite (EG) were uniformly dispersed in EP using three‐roll milling (TRM) technology, ensuring the GNPs were well integrated with the EP matrix. Additionally, the surface modification of CF with octahedral magnesium‐aluminum (MA) spinel was investigated to improve the adhesion between EP and CF. The results showed that when GNPs were incorporated at 1 wt% of EP, the resulting GNPs reinforced EP matrix CF composites (GNPs‐EP/CF) exhibited enhancements of 26% and 12% in flexural and tensile strengths, respectively, compared to EP/CF composites. Furthermore, CF modified with a 1.5 wt% of MA solution produced octahedral MA‐spinel‐modified CF bonded to the epoxy resin matrix reinforced with TRM‐exfoliated GNPs, resulting in composites (GNPs‐EP/MA‐CF), which demonstrated a 20.2% and 14.6% increase in flexural and tensile strengths, respectively, over GNPs‐EP/CF composites. This research expands the scope of carbon fiber by functional oxides with special structures and provides a theoretical foundation for developing advanced materials and technologies for aviation applications. Highlights Successful exfoliation of EG to GNPs utilizing TRM and EP. Achieve uniform dispersion and tight binding of GNPs in EP. MA modifies CF surface to improve EP‐CF binding. MA and GNPs bond to the matrix to enhance the crack extension energy.