Fatigue failure of adhesively patched 2024-T3 and 7075-T6 clad and bare aluminium alloys

摘要

The fatigue behaviour of adhesive patches used for repairing aircraft components was investigated. Adhesive patches were simulated using single-lap shear specimens on clad and bare 7075-T6 and 2024-T3 aluminium alloy substrates. Stress-life curves were generated under constant amplitude loading at three stress ratios: R=-1, 0 and 0.5. In the bare materials, failure always occurred in the adhesive itself leaving the substrates intact. At fatigue lives below about 100 000 cycles, the clad alloy specimens also failed in this manner. However, at lower stress levels, the clad alloys failed by cracks initiating in the cladding layer along the end of the lap and subsequently propagating through the substrate. The fatigue strength of the substrate, due to the adhesive patch on the clad materials, was reduced by an order of magnitude compared to the Military Handbook values.