Similar and dissimilar T-joints were made from 3 mm thick 2024-T3 cover sheet combined with 2.5 mm thick stiffeners consisting of either 2024-T3 or 2098-T8 material. The as-welded quality of both the surface and the fillet radius was high enough to avoid any post-weld machining. The T-joints were analysed by microstructural inspection, hardness profiles and tensile test behaviour. Results were somewhat less favourable for dissimilar joints caused by the artificially aged T8 temper of 2098 alloy resulting in a higher degree of overaging as compared to that in similar T-joints. Both SENT medium scale specimens and 2-stringer panels were produced to investigate fatigue crack growth perpendicular to the joint line. Crack growth rates were somewhat higher for the dissimilar configuration, but this effect could directly be correlated with lower amounts of compressive residual stresses present in front of dissimilar weld seams. Crack resistance curves in terms of loading force versus crack opening displacement revealed an increase in fracture toughness for the dissimilar joint as compared to the similar configuration. This effect might be attributed to the higher stiffness and the more ductile root of the welded 2098 stringer combined with the somewhat higher strength of 2098-T8 parent material.
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