Effect of Hybridization of Carboxyl‐Terminated Acrylonitrile Butadiene Liquid Rubber and Alumina Nanoparticles on the Fracture Toughness of Epoxy Nanocomposites

The aim of this work was to study the effect of carboxyl‐terminated acrylonitrile butadiene (CTBN) liquid rubber and alumina nanoparticles (Al₂O₃) on the fracture toughness of an epoxy resin. Hybrid nanocomposite samples were prepared by the inclusion of the optimum concentration of CTBN (15 phr) and 0–10 phr Al₂O₃ into the epoxy matrix. Samples were examined using Fourier transform infrared spectroscopy, scanning electron microscopy, and fracture toughness test. Fractal dimension values were also estimated from the edge of the fracture surfaces for the hybrid samples. The maximum value of critical stress intensity factor, K _IC, was found for the non‐hybrid sample containing 15 phr CTBN and the G _IC values showed an increasing trend as it was expected from the increase in K _IC values and decrease in Young's modulus. The maximum K _IC for the hybrid samples was obtained for the one containing 7 phr Al₂O₃ and an almost similar trend was observed for G _IC, accompanied with the significant changes in the fracture surface morphology. These were consistent with the fractal dimension results, where the sample containing 7 phr Al₂O₃ exhibited the maximum roughness. Therefore, the hybrid system of epoxy/CTBN (15 phr)/Al₂O₃ (7 phr) was found to be the optimum formulation. POLYM. COMPOS., 40:2700–2711, 2019. © 2018 Society of Plastics Engineers