By increasing the rotation speed, stirred zone grain size became larger.
The influence of the traverse and rotation speed on the microstructures, mechanical properties and residual stresses of the welded Aluminum plates were investigated. In addition, the electrical impedance curve has exhibited several sharp increases, which are attributed to the rapid crack growth.įriction stir welding was performed on AA2024-T6 aluminum plates using different rotation and traverse speeds with the objective of improving the mechanical strength and microstructure properties. During crack growth, the conductive network in epoxy matrix near the crack tip would be break and thus the electrical impedance would be increased. Almost linear trend has been observed in the impedance curve for the strain value of 0.57. Considering the electrical impedance changes simultaneously with the mechanical response of the adhesive joints, novel outcomes were obtained. In order to provide high sensing capability in the adhesive joint, several aluminum to aluminum adhesive joints were prepared by dispersion of 2.5 wt.% MWCNTs or 12 wt.% f-GNPs into the epoxy adhesive, respectively. The study aims to investigate the crack extension in the adhesive joint (Fracture mechanics) under mode I loading by both smart adhesives and proper measurement technique. The opening fracture mode (Mode I) loading condition, as one of the important fracture modes in adhesive joints was precisely evaluated in this study. The addition of Multi-wall carbon nanotubes (MWCNTs) or functionalized-graphene nanoplatelets (f-GNPs) into the epoxy resin create an electrical conductive networks which can be employed for structural health monitoring (SHM) in sensitive adhesive joints. Additionally, in comparison with interface fracture in defective adhesive joint, when a part of crack grows through the adhesive layer, the resistance change showed higher values. The results showed that the maximum relative resistance change has occurred by 220% when the microcracks are initiated and accordingly developed from the nanoadhesive and changed its direction from the Square defect boundary.
The effects of square and circular defects with two different sizes on the crack extension in the adhesive layer are evaluated. To provide a more concise evaluation of the crack extension in the adhesive layer under shear load, artificial defects are embedded into the SLJ specimens. Epoxy adhesive with high concentration of CNT is obtained during shear loading to have the maximum strength and provide the best sensory properties. Different weight percent of CNT are added to epoxy adhesive. In this work, the capability of CNTs for crack extension of a single lap Al-Al adhesive joints (SLJ) under shear load is studied using electrical resistance change. Carbon nanotubes (CNT) are ideally suited to be employed for damage sensing in fiber reinforced composite structures.
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