Fatigue behavior of adhesively bonded aluminium double strap joints

The fatigue life and failure mode of double strap joints constructed from bare and clad aluminum alloys were examined. Substrate failures were found to occur at lower stress levels, while the failure mode at higher stresses was debonding of the patches. The stress/strain state at the edge of the patch was altered by changing the patch thickness, patch modulus, or by tapering the edges of the patch. The specimens were modeled using finite element analysis. The results of the finite element analysis revealed a power law relationship between fatigue life and either the peak principal strain in the adhesive for adhesive failures, or the nominal axial stress in the substrate for substrate failures. The fatigue life and failure mode of a double strap joint specimen can be determined by calculating the failure life for that specimen under adhesive and substrate failure. The failure mode with the shortest life will indicate the failure mode and fatigue life of that specimen. Copyright © 2008 by ASTM International,.