Interlaminar fracture toughness of carbon fibre/RTM6-2 composites toughened with thermoplastic-coated fabric reinforcement

Thermoplastic toughening of epoxy (RTM6-2)/carbon fibre (CF) laminate composites without modification of the resin is reported, in which a CF fabric coated with 20 wt % of a poly (aryl ether ketone) (PAEK) was used to toughen composites. Dissolution of the PAEK during resin infusion, with subsequent reaction-induced phase separation and phase inversion during curing, formed PAEK-rich continuous layers with dispersed RTM6-rich particles within the interlaminar regions. These layers provided significant toughening during interlaminar fracture testing, in which the Mode I and Mode II fracture energies for the toughened system increased from 216 ± 7.2 to 751 ± 105 and 857 ± 99 Jm^-2 to 3316 ± 372 Jm^-2, respectively. Thus, coating of the CF fabric with PAEK avoided the significant increases in viscosity observed with resin systems containing dissolved thermoplastics; whilst generating multiphase toughening layers at the CF fabric – matrix interfaces which provide efficient interlaminar toughening.