Hybrid thermoset composites for improving fracture toughness

In this work, the engineering thermoplastic and the rigid nanofiller aim to toughen a brittle epoxy resin without losing the mechanical and thermal properties of this thermoset. The composites of polyethersulfone (PESU), Graphene nanoplatelets (GNPs) and bisphenol A-based epoxy resin was prepared by mechanical mixing. The influence of PESU and GNPs on the characteristics and properties of epoxy were investigated. For the binary blends of PESU/epoxy, two-phase morphology was observed which PESU-rich phase dispersed in the epoxy matrix. According to the two-phase morphology, the enhancement of fracture toughness (KIc) and fracture energy (GIc) of the blend was obviously found with PESU content. Fracture surface showed the crack deviation around the thermoplastic phase that is the vital toughening mechanism for the binary blend. In addition, the presence of 0.5 wt% GNPs slightly improved fracture performance of the binary blend. The maximum value of KIc and GIc (1.05 MPa.m^1/2 and 236 J.m^-2 respectively) were investigated at the combination of 10 wt% PESU with 0.5 wt% GNPs loading which were counted as 37 % and 71 % improvement compared with the reference epoxy, respectively. As expected, the glass transition temperature (Tg) and tensile properties of the composites were maintained with the addition of PESU and GNPs.