| General note |
Adhesive joining presents a compelling substitute to traditional joining techniques, like<br/>welding and mechanical fastening. Adhesive bonding offers several advantages, such as the<br/>capability to construct lightweight and stiff structures, the ability to join various types of<br/>materials, offer improved fatigue performance, and a decrease in heat effects zones commonly<br/>associated with welding. However, lack of structural redundancy and moderate strength offered<br/>by adhesive joints still makes it an area of exploration for researchers as joint strength is<br/>significantly influenced by geometric, surface, manufacturing, and environmental parameters.<br/>In recent times, modification to the properties of host resin by the addition of nanofillers is a<br/>non-geometric parametric technique proven to be effective in improving the mechanical<br/>performance of adhesive joints. In literature, the effects of various fillers (metallic, nonmetallic) have been studied with varying rates of success. The conducted research aims to fill<br/>the gap in the non-metallic category by performing a systematic study of the effect of graphene<br/>nanoplatelets (GNPs), multiwalled carbon nanotubes (MWCNTs) and reduced graphene oxide<br/>(RGO) addition on a high viscous, high strength structural adhesive at various weight fractions<br/>of the nanofiller addition. The nanofillers including the functional components of GNPs and<br/>MWCNTs (COOH and NH2 functionalized) were added in weight fractions of 0.25, 0.5, 0.75<br/>and 1 wt% in the adhesive. A comprehensive mixing method based on solution mixing<br/>technique was developed for uniform mixing of nanofillers in the host resin. The effects of<br/>filler addition on the dispersion characteristics, mechanical response of nanofiller/adhesive<br/>composite and strength characteristics of two different lap joint configurations were then<br/>investigated. The joints were fabricated using aluminum 5083 alloy where adherends were<br/>electrochemically treated prior to joining. Lap shear tests were conducted on Universal Testing<br/>Machine (UTM). Fourier-Transform Infrared Spectroscopy (FTIR) was utilized for the<br/>analysis of functional groups and chemical interaction of nanofillers with the adhesive.<br/>Variation in the cure kinetics was investigated using Differential Scanning Calorimetry (DSC).<br/>Ultraviolet-Visible Spectroscopy (UV-VIS-Nir) was carried out to quantitatively quantify the<br/>dispersion characteristics of nanofillers. ANOVA study was performed for the evaluation of<br/>data variation and interaction. Optical and Scanning Electron Microscopy (SEM) was utilized<br/>for the analysis of fracture surfaces, and the correlation between nano-reinforcement and<br/>strengthening mechanisms was critically discussed. A comprehensive comparison of the<br/>x<br/>mechanical behavior of bulk adhesive specimens and strength characteristics of lap joints<br/>reinforced with GNPs, MWCNTs and RGO was established.<br/>The novelty of the research is that, it introduces a pioneering exploration into the combined<br/>effects of functional and non-functional components of Carbon Nanotubes (CNTs), Graphene<br/>Nanoplatelets (GNPs), and Multi-Walled Carbon Nanotubes (MWCNTs) within high viscous<br/>structural adhesive. Unlike previous independent studies, our approach considers filler<br/>concentration, dispersion behavior, and diverse lap joint configurations, providing a holistic<br/>understanding of their impact on mechanical properties. The developed solution mixing<br/>technique ensures uniform nanofiller dispersion, and advanced characterization techniques<br/>offer unprecedented insights. This research not only addresses critical literature gaps but also<br/>provides a roadmap for tailoring adhesive properties, with wide-ranging implications for<br/>automotive, aerospace, marine, and construction industries.<br/>The result of the study depicted that the role of non-functionalized GNPs, MWCNTs in<br/>improving failure parameters in lap joints was superior to that of nonfunctionalized ones in<br/>general. This is a consequence of their superior dispersion properties and higher cross-linking<br/>density with the adhesive. However, in comparison between fillers, the strength improvement<br/>of lap joints reinforced with MWCNTs was superior to both GNPs and RGO. This is due the<br/>lateral length of the MWCNTs particles being greater than GNPs and MWCNTs which<br/>provided maximum shearing resistance out of the three nanofillers. The findings of this<br/>research can be applied to the aerospace and automotive sectors, construction and infrastructure<br/>and general adhesive industry where adhesive joints play a critical role in structural integrity.<br/>By incorporating carbonaceous nanofillers into epoxy adhesives, it is possible to enhance the<br/>strength and durability of adhesive bonds, resulting in improved performance and safety. |
