Determination of the effects of nanoparticle reinforcements on mechanical and composite surface fractures in joints bonded with epoxy adhesives

Various studies are carried out to increase the strength of the joints made with adhesives. One of these studies is to investigate the use of nanoparticles as reinforcement elements in adhesives. In this study, the tensile strength of the bonding joints made by adhesives DP410, DP460 and DP490 epoxy adhesives at the rates of 0.1, 0.2, 0.3 and 0.4% wt. of the graphene nanoparticles (GNP) were investigated. AA5754 aluminum alloys and glass fiber reinforced composites were used as adherent and patches, respectively. Tensile tests were carried out to determine the effect of reinforcement ratios on adhesive bonds. After the tensile tests, macro and scanning electron microscopy (SEM) images were taken to examine the adhesion damage between nanoparticle, adhesive and adherent surfaces. In the results of the tensile test experiments, the tensile strength of all the joints in which the reinforcement element is used was higher than the non-reinforced bonding. The highest tensile strength in GNP-reinforced joints using DP410 and DP490 adhesives was obtained as 5674.4 and 4837.4 MPa, respectively, at 0.2% wt. reinforcement rate. However, the highest tensile strength of all experiments was obtained as 6154.4 MPa in DP460 adhesive, where 0.3% wt. reinforcement ratio was used. In the damage analyses made after the tensile tests, it was observed that there were fiber breaks in the glass fiber composite used as the patch material in the bonding joints, where homogeneity was formed between the surfaces of the GNP and the epoxy adhesive. Especially, this situation occurred in the joints where 0.2% wt. in DP410 adhesive and 0.2% wt. and 0.3% wt. of reinforcement ratios of DP460 adhesive joints were used. Finally, in the fatigue tests, the GNP particle reinforcement increased the fatigue life of the adhesive joints.