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This paper deals with the complexity of mechanical characterization of adhesives and modelling its behaviour in an assembly. Different testing systems have been studied such as tensile tests on bulk specimens, Arcan-Mines tests in different loading conditions, to characterize the mechanical behaviour and failure criteria of an epoxy base adhesive, under static and fatigue loading by taking into account viscoplastic behaviour of the adhesive. A static failure criterion has been proposed and extended for fatigue loading. Thick Adherent Shear Tests and single lap shear tests have been performed and compared with previous ones. A Finite Element (FE) simulation has been made in order to validate the proposed models. [ABSTRACT FROM AUTHOR]

Numerical calculations become a more and more efficient way to estimate the lifetime of structures under thermomechanical loading. But these life estimations cannot be reliable if the needed parameters have not been correctly identified and measured and if not all the damage causes have been considered. The disk testing under gas pressure is an experimental technique used for the mechanical characterization of thin sheets with various conditions: monotonous loading (biaxial rupture tests at strain rates from 10-6 to 10° s-1), constant loading under high stresses (sustained load) at elevated temperature (creep tests), cyclic loading (mechanical fatigue tests); the temperature may be chosen between 20 and 900 °C. The disk testing quickly reveals the damage when crossing cracks through the membrane create leakages detected by a mass spectrometer. Besides, we have developed a calculation method in order to measure the true mechanical properties of the pressurized disk. We evidence the quality of the results obtained with this method in the thermomechanical characterization of thin sheets and its sensitivity to secondary parameters. The analytical method of calculation will be optimized in order to obtain the best modelling of thermomechanical behaviour of materials loaded at temperature and strain rates within very large ranges and subject to different environments as gaseous hydrogen. [ABSTRACT FROM AUTHOR]

Abstract: The ability of structural adhesive to withstand combination of cyclic loading and service environment makes them suitable for a wide range of applications. It is nevertheless true that their mechanical and micromechanical behaviour is still little understood. The purpose of the work reported here is to study the fracture process and the role of talc fillers of an epoxy adhesive subjected to oligocyclic fatigue. Tests were conducted by using a set-up based on the Arcan fixture and experimental results have been reported for both tensile and shear cyclic loadings. The cohesive failure of the adhesive seems to set off at a specific amplitude level, whatever the loading value. By an incursion at the microstructural scale using scanning electron microscopy, we suggest an explanation of these phenomena. The foliated form of talc fillers are of major importance and seem to provide a deterministic evolution of damage. [Copyright &y& Elsevier]