Investigation of the mechanical behavior of adhesion bonded nanoparticulate composites

With the use of composite materials in many application areas such as aviation, construction, maritime, health, transportation, etc. sectors, it is seen that there are advances in these areas. Especially in these areas, some joining techniques are applied by bonding in order to improve the damage that occurs in composite materials, to recycle and use the material. In addition, nanocomposite materials have started to be used in order to show better mechanical performance and to improve their mechanical properties in application areas. Twill glass fiber reinforced epoxy composite sheets were used in this study. These sheets were produced both without additives and by using three different ratios of nano clay, boron carbide and graphene in epoxy resin, nano-additive glass fiber reinforced epoxy composite sheets were produced. Nano-additive ratios were determined as 0.75%, 1% and 1.25% by weight. Sheets without additives and all three sheets with nano-additives were produced by hand-laying method. These sheets were obtained with 8 layers and 2 mm thickness. In all the sheets produced, samples were prepared in three different geometries as undamaged, overlapped and single-effect patched connection. In the connection samples, the connection shape was created with adhesives and special molds produced by 3D printers. All prepared additive-free, nano clay, boron carbide and graphene-added glass fiber reinforced epoxy composite samples were subjected to tensile tests. In this experimental study, it was determined that the lap-joined samples showed higher damage load compared to the single-effect patched-connected samples. It was determined that boron carbide reinforcement did not improve the tensile strength in all study samples, and in clay samples, it was found that it increased by 2.7% in the undamaged sample with 1.25% additive ratio, by 2.9% in the lap-joined sample and by 3.7% in the single-effect patched-connected sample compared to the additive-free samples. It was found that graphene increased by 1.26% in the single-effect connection samples with 1.25% additive ratio and by 10.49% in the lap-joined samples. While the clay additive showed both increasing and decreasing effects at different rates, it was found that the boron carbide additive mostly reduced the damage load. It was determined that graphene additive provided a decrease in the damage load at 0.75% and 1% additive rates in all samples, and an increase of 10.49% in lap jointed samples with 1.25% additive rate, and 1.26% in single-effect patched jointed samples. In this study, it was determined that the meticulous selection of the connection geometry together with the nano additive type and rate is of critical importance to achieve the desired mechanical performance.