The synergistic effect of hybrid nano-silica and GNP additives on the flexural strength and toughening mechanisms of adhesively bonded joints

Abstract

This study intended to research the effects of nanoparticle hybridization (nano-silica and GNP) on the bending performance of adhesively bonded joints of Al-2024 sheets. For this purpose, nano-silica/GNP hybrid nanofiller reinforced single lap joints (SLJ) with total additive ratios of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% by weight were manufactured and subjected to three-point bending tests. Among hybrid nanoparticle-doped joints with a ratio of nano-silica to GNP of 1:2,1:1, 2:1, 3:1, and 3:2, the best performance was obtained in a 1.5% nano-silica +0.5% GNP doped sample with 3:1 particle ratio. The enhancement in flexural strength was 51.3% in this sample compared to the sample containing pure Araldite 2014 adhesive. In addition, it exhibited 3.1% and 30.8% better strength, respectively, compared to the samples containing single GNP and single nano-silica particles. In the SEM views which were taken from fracture surfaces of the damaged samples, it was observed that the hybridization of nano-silica and GNPs improved the particle dispersion. Nano-silica particles were attached between the GNP lamellae, forming a new three-dimensional hybrid structure. This structure improved the interfacial interaction of nanoparticles with the adhesive, and also increased the resistance of crack deviation, crack stopping, crack bridging and pull-out mechanisms against peeling and shear stresses caused by three-point bending loads.