Investigation into cracked aluminum plate repaired with bonded composite patch

Several parameters/factors related to mechanical and fatigue behaviors of a cracked 7075-T6 aluminum panel repaired with one-sided adhesively bonded composite patch were studied by a combined experimental–analytical approach. These were strain distribution, out-of-plane deformation and residual strength along with crack growth behavior. The effects of cool-down temperature during patch bonding, disbond and bending moment were also investigated. Residual thermal stresses, developed during patch bonding, requires the knowledge of temperature at which adhesive becomes effective in creating a bond between the specimen and patch. This can be determined through the out-of-plane deformation of the repaired panel. A bending moment is developed upon application of axial load due to initial out-of-plane deformation of the repaired panel with one-sided bonded patch. This can be also determined from the out-of-plane deformation. Further, the bending moment and temperature change during patch curing have a relatively more effect on the out-of-plane deformation than on the in-plane strain of the repaired panel. The disbond does not affect the out-of-plane deformation and in-plane strain except in their vicinity. Crack length has a small effect upon the in-plane strain and out-of-plane deformation. The stress intensity factor varies along the thickness of the repaired panel; however, crack growth rate was primarily dominated by stress intensity factor near the bonded patch side of the thin repaired panel in the present study. The bonded patch repair of a cracked panel provides a considerable increase in the residual strength as well as fatigue life.