Effect of carbon nano-filler addition on the degradation of epoxy adhesive joints subjected to hygrothermal aging

In this study, the effect of hygrothermal aging on the strength of pure and carbon nano-filler reinforced epoxy adhesive joints is presented. Epoxy adhesives containing three different carbon nano-fillers, namely, multi-walled carbon nanotubes (CNT), graphene nanoplatelets (GNP) and single walled carbon nanohorns (CNH) were prepared by using a high shear rate mixer. Thermogravimetric analysis (TGA) of the nano-filler reinforced epoxy indicated an improvement in the thermal stability compared to pure epoxy. Aging studies were carried out on single lap-shear specimens as per EN ISO 9142:2003 standard (cycle D3). The strength of the joints was found to decrease with hygrothermal aging time. The nano filler reinforced joints showed less reduction in joint strength with aging compared to pure epoxy joints. The GNP/epoxy joints showed the best resistance to aging followed by CNT and CNH reinforced joints. Fourier Attenuated Total Reflectance Transformation Infrared Spectroscopy (ATR-FTIR) analysis of the hygrothermal aged samples indicated lower degradation in terms of hydrolysis of epoxy groups for nano-filler reinforced epoxy. Gravimetric analysis of samples immersed in water showed lower weight gain for nano-filler reinforced epoxy composites. Fracture surface analysis was carried out to study the change in failure mechanism with aging time. (C) 2017 Elsevier Ltd. All rights reserved.