Improving the Mechanical Performance of Adhesively Bonded CFRP Composite Joints Exposed to Harsh Mediums with the Reinforcement of Boron Nanostructures

Abstract

In this study, the degradation in the strength of adhesively bonded carbon fibre composite joints exposed to different harsh mediums was improved with the addition of silane-modified BN and B4C nanostructures. For this purpose, modified BN and B4C nanostructures were added to the structural adhesive, and then composite plates were bonded with the new reinforced adhesives to produce single lap joints. The produced joints were aged 480, 960, and 1440 h in distilled water, saltwater, sulphuric acid, and ultraviolet light mediums. The mechanical properties of the joints were determined by the tensile test after aging. Moreover, liquid absorption and SEM analyses were performed to observe the structural change in the adhesives. The results revealed that adding nanostructures into the epoxy matrix positively decreases the absorption of distilled water, saltwater, and sulphuric acid solutions. It was also observed that the failure loads of joints decreased depending on the severity of the damage caused by the aging mediums. The joints bonded with BN and B4C nanostructures reinforced adhesives decreased the damage experienced by limiting the harmful effects of the mediums. After 1440 h of aging in the distilled water medium, the composite joints reinforced with BN and B4C nanostructures carried approximately 40% and 37.6% higher loads, respectively, compared to the neat joint. Similarly, as a result of the aging in the UV medium, BN and B4C reinforced joints carried approximately 48.3% and 40.9% higher loads, respectively, while these ratios were determined as 39.7% and 36.7%, respectively, for the saltwater medium.