Fatigue of bonded steel interfaces under cyclic shear loading and static normal stress

Hybrid joints that combine mechanical fastening and bonding provide potential joining alternatives for high strength steel structures. An experimental and analytical research program has been initiated to assess the static and cyclic Mode II shear strength of epoxy bonded steel interfaces subjected to static normal (Mode I) pre-stress. During cyclic loading, shear stress vs. interface displacement could be divided into elastic and inelastic regions with a power law equation describing the inelastic curve. Hysteresis loop shape varied with normal stress, shear stress and accumulated fatigue cycles. A shear stress amplitude threshold equal to about 50% of the fracture shear stress was observed.