On adhesive properties of nano-silica/epoxy bonded single-lap joints

The effects of nano-silica on the adhesive properties of epoxy were systematically studied by single lap-shear tests under quasi-static and cyclic loadings. The adhesives were produced from different amount of nano-silica particles incorporated into diglycidyl ether of bisphenol A (DGEBA) epoxy. Stainless steel plates were chosen as adherends. Quasi-static tests were conducted on single lap-shear joints at ambient, with and without exposure to 100% RH at 60 degrees C for different times. Cyclic fatigue tests were also performed on these bonded joints under tension-tension loading. The fracture surface morphology was examined using scanning electron microscopy (SEM) to identify the failure mechanisms. Compared to neat epoxy, it was found that the adhesive strength is increased by 20% under quasi-static loadings. Even after hygrothermal treatment, the benefit of having nanosilica in neat epoxy on the adhesive joint strength was retained. In cyclic fatigue, without hygrothermal aging, nano-slica/epoxy adhesives have longer lifetimes than neat epoxy; but after hygrothermal treatment, they have similar lifetimes for given stress amplitudes. (C) 2016 Elsevier Ltd. All rights reserved.