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This paper concerns the experimental characterization of static and fatigue strength of a flat panel stiffened by bonded pad made of aluminum alloy. The panels were full scale and tested under both static and fatigue loads, applied by means of an in house designed and built multi-axial static and fatigue machine. The fatigue crack propagation life of the stiffened panel has been compared to that of a simple flat panel and to that of a flat panel with chemical milling pad-up, getting that the fatigue crack growth life can be significantly improved.

During the last few years various experimental destructive and non-destructive methods were developed to evaluate residual stresses. However it is impossible to obtain a full residual stress distribution in welded structures by means of experimental methods. This disadvantage can be solved by means of computational analysis which allows to determine the whole stress and strain fields in complex structures. In this paper the temperature distribution and residual stresses were determined in a single-pass butt joint welded by GMAW (Gas Metal Arc Welding) process by finite element model (FEM). A 3D finite parametric element model has been carried out to analyze temperature distribution in butt weld joints and thermo-mechanical analyses were performed to evaluate resulting residual stresses. Temperature fields have been investigated by varying an initial preheating treatment. Moreover the technique of “element birth and death” was adopted to simulate the process of filler metal addition The high stresses were evaluated, with particular regard to fusion zone and heat affected zone. The influence of preheating and post-heating treatment on residual stresses was investigated. The residual stresses decrease when preheating temperature increases. The maximum value of longitudinal residual stresses without pre-heating can be reduced about 12% and 38% by using the preheating and post-heating process respectively.

In the present paper, results of experimental tests carried out on hybrid (bonded/bolted) and adhesive composite single-lap joints are showed. The laminate adherends were made by unidirectional carbon fiber/epoxy with symmetric stacking sequence. In particular, the tests were carried out to evaluate strength and failure mode of the different joints. These joints were subjected to quasi-static tensile displacement and tests were conducted using a universal testing machine. The maximum tension load that the specimen can bear is determined and the failure process is correlated to the lay-up of the composite and joint type.