On the fracture of nano-silica/epoxy bonded single-lap steel joints

Abstract

This research aims to investigate the influence of nano-silica inclusion on the adhesive properties of an epoxy resin, and its capability in increasing the failure load of the joint with steel substrates. For this purpose, single-lap joints manufactured from Stainless Steel 304 (SS) adherends bonded together with a thin layer of the silica-reinforced epoxy resin (as the adhesive) are investigated. To improve the epoxy, silica nanoparticles (SNPs) are utilized in three different concentrations (i.e. 1, 2 and 3 wt. %). Failure loads of the joints are extracted by uniaxial tensile loading for the joints including either neat or reinforced epoxy resins. Scanning Electron Microscope (SEM) are used to examine the dispersion quality of nanoparticles into the polymer as well as the hindrance effect of the nano-silica inclusions on the micro-cracks' propagation or/and their unification. In addition, the fracture surfaces of the joints were investigated so as to relieve the failure type of the joints; whether cohesive or a combination of both adhesive and cohesive types. It was found out that the joint including silica-reinforced epoxy resin at 2wt.% best improved the failure load and changed the debonding mechanism to a fully cohesive type compared to that of the joint comprising the neat resin.