Improvement of toughness and shear properties of multiwalled carbon nanotubes/epoxy composites

In this work, Epocast 50-A1/946 epoxy have been modified with different weight percentages (0.25, 0.5, 0.75, 0.1, 1.25, and 1.5 wt%) of multiwalled carbon nanotubes (MWCNTs). Because of Epocast epoxy was primarily developed for joining and repairing of composite aircraft structural components, the optimum weight percentage of MWCNTs must be determined based on trade-offs between the optimum tensile, in-plane shear and toughness properties of the developed MWCNTs-composites, which is the objective of this study. The effect of MWCNTs on the toughness and in-plane shear was studied using single-edge notch tension and Iosipescu shear tests, respectively. The experimental results showed that the composite materials with 0.75 wt% MWCNTs has the highest improvement in the in-plane shear properties compared to the neat epoxy. While the maximum improvements in the tensile and toughness properties were observed at 0.5 wt% MWCNTs. Eleven models were selected from an extensive literature survey, for predicting the in-plane shear moduli of the developed MWCNTs-composites. The modified rule of mixture can effectively predict the in-plane shear moduli of the composites with MWCNTs up to 0.75 wt%. While the nonlinear behavior of the modified Halpin-Tsai model with exponential shape function is the closest to the experimental results up to 1.5 wt% MWCNTs. POLYM. COMPOS., 39:815-825, 2018. (c) 2016 Society of Plastics Engineers