Fatigue crack propagation rate of CFRP/aluminum adhesively bonded DCB joints with acrylic and epoxy adhesives

Recently, structural acrylic adhesives have received increased interest because they can be cured at room temperature. However, there are few studies investigating the strength behavior of CFRP/metal joints bonded with acrylic adhesive, especially under cyclic loading. In this study, the fatigue crack growth rate was measured using adhesively bonded CFRP/aluminum double cantilever beam (DCB) joints made with an acrylic adhesive. To compare fatigue crack growth behavior with heat-cured type adhesive, fatigue testing was also conducted for DCB joints with an epoxy adhesive. For CFRP/aluminum asymmetrical joints, the ratio of the thickness of the lower adherend to the upper adherend is an important factor determining the mode ratio and stress distribution at the crack tip which are affected by the residual stress generated in the curing process. The effect of the thickness ratio for the DCB joints on the fatigue crack growth rate was investigated for DCB joints with both acrylic and epoxy adhesives.