The effect of nanoparticles in single-lap composite joints studied by experimental and numerical analyses

The effect of Cu nanoparticle adding on to epoxy-based adhesive and adhesion properties

Epoxy-based adhesives are widely used for repairing or jointing the metal sheets in the industry. Because of their superior mechanical properties, the metallic nanoparticles can be selected as the additive of the epoxy adhesive. The strength of the Cu nanoparticles (CuNPs) can be expected to improve the mechanical properties of neat epoxy. In this study, CuNPs were added at various weight ratios, such as 1, 2, 5, 10, 15, and 20% into the epoxy resin adhesive. Tensile tests of the dog-bone specimens and the lap-shear tensile tests of the single lap joints were performed for obtaining the mechanical properties. In order to investigate the failure mechanisms, the fractured surfaces of the tensile test samples and adhesively joined sheets were imaged by using a Scanning Electron Microscope. The thermal properties of the adhesives were obtained by using Thermo Gravimetric Analysis and Differential Thermal Analysis. The mechanical and thermal properties of epoxy resin adhesive were improved by adding the CuNPs. The best adding ratios of CuNPs into epoxy were obtained by both mechanical and thermally point of views. As a result of this study, 15 wt% the ratio of Cu nanoparticle adding into the epoxy-based adhesive is suitable for improving the mechanical properties. On the other hand, 20% is the proper Cu nanoparticle adding ratio for the thermal properties improving.

Superior thermomechanical and wetting properties of ultrasonic dual mode mixing assisted epoxy-CNT nanocomposites

High-performance epoxy-carbon nanotube (CNT) nanocomposites were prepared by simultaneous use of ultrasonication and mechanical stirring. The dynamic and static mechanical properties and wetting properties of the nanocomposites were investigated. The dynamic mechanical analysis presented significant enhancement in storage modulus (approximately 124%) and glass transition temperature (approximately 25.6%) of epoxy-CNT nanocomposite at an optimized concentration of the CNT (0.25 wt%) possibly due to the formation of a strong interface between the epoxy and CNT. The tensile test results showed the significant improvement in tensile strength (approximately 47%) and Young’s modulus (approximately 40%) of the epoxy-CNT (0.25 wt%) nanocomposite without significantly affecting its stiffness. The homogeneous dispersion of CNTs in the epoxy matrix resulted in the significant enhancement in the dynamic and static mechanical properties of the nanocomposites. The hydrophilic character of the neat epoxy was tuned to a highly hydrophobic one by incorporation of CNTs in it. A direct relation between the average roughness of the tensile fracture surfaces and the contact angle of the nanocomposites was identified with respect to the concentration of the CNTs. These high-performance highly hydrophobic nanocomposites have the great potential to be used as the structural and functional materials in humid environments.