Shear performance of MWCNTs modified single-lap joints of glass/epoxy laminates

In this experimental work, the single lap joint (SLJ) adhesive strength of glass fibre reinforced epoxy (GFRP) composites was investigated under quasi-static tensile loading. The adhesive used was 'Araldite® adhesives-2015 (AA)'. Further, the functionalized multiwall carbon nanotubes (s-MWCNTs) were used to modify the AA. The s-MWCNTs were mixed in AA through the ultrasonication method at six weight ratios, i.e. 0, 0.25, 0.5, 0.75, 1 and 1.25 wt. %. Experimental results showed that among different weight fractions of s-MWCNTs modified AA, the 1 wt. % of s-MWCNTs reinforcement yielded a maximum bond strength and slip. The two-parameter Weibull statistical method proved that the results for increasing s-MWCNTs in AA were reliable up to 1 wt. % s-MWCNTs doping. Strain-field analysis at bond-edge by using digital image correlation (DIC) technique showed a significant variation with s-MWCNTs reinforcement in strain distributions at bonded edge-section. Fracture behaviour analysis at the macroscopic and microscopic proved that with the rise in uniformly distributed s-MWCNTs, bridging (or interlocking mechanism) occurs, which hindered the bond failure. Further, above the optimized value of s-MWCNTs reinforcement, i.e. 1.25 wt. % of s-MWCNTs in AA; an agglomeration of s-MWCNTs took place, reducing the bond performance.